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Home , Phosphor, Phosphorus pentoxide, Phosphorus tetroxide, Phosphorus trioxide

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Professional Degree Theses Student Theses and Dissertations

1944

The combustion of

Erwin Charles Hoeman

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Recommended Citation Hoeman, Erwin Charles, "The combustion of phosphorus" (1944). Professional Degree Theses. 284. https://scholarsmine.mst.edu/professional_theses/284

This Thesis - Open Access is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in Professional Degree Theses by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. THE COMBUSTION OF PHOSPHORUS BY

ERWIN CHA.RLES HODWt

A

'l'HESIS

subnitted to the faculty of the

SCHOOL OF MINES AND METALLURGY OF THE UNIVERSITY OF MISSOURI

1D partial. fulfillment of the work required tor the

Degre. of

CBDlICAL gGIIllma

Rolla~ II1s80url 1944

Approved by: It;-\/ '~I Cha1rmaD,De.partmant of. Chaistry ind Chea1cal IDg1Deer1ng. i

ACKNOWLEDGMJ!JiT

The author gratefu1lr acknowledges the experience gained in the production and utilization of phosphorus, through his employ­ ment in the Department of Chemical Engineering of the United States

Tennessee Valley Authority. 'SpecificallY', he acknowledges the supervision of work and inspiration gained through his association with Dr. RaY'Dlond L. Copson, Chief of the Research and ,Development

Division; Dr. GradY' Tarbutton, Assistant to the Chief; and

Mr. John H. Walthall,. Head of the Developllellt Section.

Particular thanks for guidanoe in the selection of the general plaD for this paper are due to Mr. J. F. Shults, formerlY'

Chemist with the United States Department of Agt-iculture, and now

Chemist in the organisation of the United States Tennessee Valley

Authority. 1i

CONT:mTS

Page

Aoknowledgment ...... i Table of contents ...... li

List of figures • • • • • • • • • • • • • • • • • • • • • • • 111

List or tables • • • • • • • • • • • • • • • • • • • • • • • • • iv In troduction ...... 1 The produotion of phosphorus in electrio furnaces ••••••• 6

The properties of phosphorus •••••••••••••••••• 20

The oombustion of phosphorus 1D air •••••••• • • • • • • 23

Industrial processes utilizing phosphorus oombustion • • • • • • 31 The preferential oxidation ot phosphorus •••••••••••• 42- The reactions of phosphorus with water ••••••••••••• J.h The oxidation of phosphorus with steam •••• • • • • • • • •• 51 An eValuation of phosphorus combustion prooesses ••• • • • •• 56 Bibliography ••• • • • • • • • • • • • • • • • • • • • • • •• 58

Inc!ex • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 111

Figure Page

1 Heat oontent of gases • • • • • • • • • • • • • • • • • • 22

2 Phosphorus made by phosphorus combustion processes • • • • • • • • • • • • • • • • •• 32 iv

Table Page

1 Significant events in the history of phosphorus • • • • • • 2

2 Installed e~city for the production of phosphorus in the United States ••••••••••••• 3

.3 Reactions in the electric furnace reduotion of rock phosphate. • • • • • • • • • ••• • • • • • • • • 10 4 Eleotric furnace operating oondi tiona and heat balance •• 12

Eleotric furnace operating data • • • • • • • • • • • • • .13 The relative amounts ot the or phosphorus produoed by burning phosphorus in air •••• • • • • • • 25 7 The cbaraoteris"'ics of oonoentrated superphosphate • • • • 36

S Production and distributiGn of fertilizers b,y TVA • • • • • J.l 9 Comparative heat balances when burning pboSpholUS with air and with a mixture of air and steam in a metaphosphate furnaoe • • • • • • • • • • • • • • • • 53 1

m OOMBUST;rQ! Ql PHOSPHORllS

Intro4uctigg

Phosphorus first jo1Ded tl» ranks of large-tonnage industrial raw materials about teD ,.ars ago, with the development of the electric furnace uthod for its production from rock phosphate. For lI8Ily years before the present era of large-scale productiOD, phosphorus had been little .ore than a laboratory oariosity. Thereafter, it found extensive applioation in. p..J1"Oteobnics, utah tips, rat poisons, and other uses Dot requiring IIOre thaD a few h1JllCime of tons in a year.

Phosphoric acids 1Mre geDerally produced by th8 reaction of with rock phosphate. The development and growth of electro­ thermal prooes.e. for the recluotion of rock phosphate completely ohanged the IIetbod ot producing pbosphoric acids. Phospborua, produced in electrio 1\Irnaoe.8, is now an industrial oommodit1' that

11&1' be burDed to the , then hydrated to phosphorio aCids, and finally oonverted into a great Dumber of phosphate COlipoundS.

A br1.ef catalogue ot the 81p1.tioant e'Yent.s leading up to the present state of deTelopaent ot the electrio-1Um.aoe process tor the production of phosphorus is abowD in the follow1Dg table: 2

Table 1

Signifioant Eunis ia tho HistorY 9! Phosphorua

Year ~Ev_ep~t~ ______

1669 Brandt discovered phosphorus.

1..,.,5 Scheele produced phosphorus from bones.

1829 Wohler produced phosphorus experim811tailT by heating calciDed bones with sand and .

1867-79 Earll ~ish and French patents on the thermal reduotion of pho8phates appeared in the 1iterature on the subject.

1890 Phosphate reduction was brought to a stage of praotical developaent by Readman and others · (Geman patents), aDd the first use 1I'II.S made of an eleotric furaaoe to SIIelt a IIixture of phosphate, cote, and silica.

1920 The first electrio f'urnace plaDt for the reductioo of rock phosphate, in the United States .. was metalled at .&amiston, Alabama, by Swann Chemical Comp8l1" (aoquired later by the Monsanto Cheaioal. CoIllp8D7).

1934 Electrie furnace processes for making phosphorus were first adapted to the manutaot.ure of phosphate fertUinr8, at Wilson Du, .Al.abama, by the United States T.anessee Valle,. Authority.

The Monsanto Company, the Tamessee ValJ.sy Autborit;y, and the Victor

Chemioal Coapany, all of which now have fumaceplants near the Tennessee pho8phate fields, were the pioneers in the productiGa ot pbosphoras on a large scale. The Victor Comp81'l7, notabl;y, al80bas .pioneered 1D the pro­ duction ot phospho1"\la by theruJ. reciuCtiOll of rock phosphate 1D the blast f'urDace. The future of the hlast-furDace method for the production of phosphoru.s, however, is at present uncertain. Apparently, it cannot compete with the electric-furnace method in areas looated near low-cost electric energy.

Statistical data on the production of phosphorus are not obtain­ able fro. the records or the United States Censua, chiefly because of 3 the 8ID8l.l nwaber of pr1aary producers. Based OIl news accounts (l) and personal 8O~ces of infomatiOll, It appears that the prociuctl00 of phosphorus has increased about eeven-fold iD the deoade from 19.30 to

1940, or as shown in the following tablez Table 6- !pstalled. Capac1t% m .:Y!I. Prpduotigp .if. Phosphona m. !!M. YD»ed Sit-tea (Tons per 8DDWI) Blast Electric Furnace ltV Furnace 'lV' Industa Total 19.30 8,000 2,000 10,000 1935 8,000 8,000 2,000 18,000 1936 1l,OOO 8,000 26,000 .45,000 1937 ll,OOO 12,000 26,000 49,000 1938 12,000 37,000 60,000 1939 16,000 38,000 54,000 ~940 16,000 49,000 65,000 1941 16,000 ':>7,000 73,000 lil1tary uses for phosph01"\lS, DOW in a t:ble ·o£ war, take praotioal-

17 t):le entire output ot phosphorus. ~d1tlonal. .productloa capacity baa

been installed .ince 1941, ad increased productioo i. being obtaiDed

troll all installation.. It Is probable that present production exceeds

100,000 tons per annuli.

The story of the development ot .processes tor the electric-furnace

productiOR. ot phosphorus and itB. nbsequ_t ·utilization 115 an extreaely

inter.sting. aocount of ohera1cal _gin.. ring achievement.

The contrlbutiOils of .the Tennessee Vallq Authority to phosphone

and phosphate developments are particular1,. thorouglUy. covered in a serie.

(1) Largel7 froa the Hews .lcUtiOl1 .of Indus.trial and Jugineering Cb..t8'try. 4 of articles, describing the W11son Dam Plant (2-9).

The plant constructed at Muscle Shoals, Alabama, for the United

States Govemment at the close otWorld War I was converted into a plant to manufacture phosphorus and phosphate fertUizers as a part of the regional development program of the Tennessee Valley !utbority.

The original p1aat _s designed to make 8JW01)i& by the caloiUII cyanamide prooeas, and to utUize the ammonia to manu.factur.e .-oniUll nitrate for JIUIl1.tions. Obviously, the plant in its original fora was a wart1llle allset, and the problem of converting it for phospboru. production had to be met in a W8.1 not to prevent its possible future

(2) Curti., H. A. TVA make. B~L electricall7 atWUson Dam. Chell. let. !ilg. v 42, pp. 320-324 (1935).

(3) Curtis, B. A. IIaldng concentrated superphosphate at TVA Works. Chem. Met. l!ilg. v 42, pp. 488-491 (1935). .

(4) CurtiS, H. A., and.iller, A. II. Operating obsernt1.oas at '!'VA Fertilizer Plallt. Chell. let. IIlg. v 43, pp. 408-4l2 (1936).

(5) IIU1er, A. II., and .Junld.ns, J. H. TVA estimates favorable costs for oOllceDVated superphosphate. Chem. let. lag. T . 43, I. pp. ·58.3-58'7 and II. pp. 647-650 (1936).

(6) Curti., H. A., Ulller, A.II., and Bewton, R. H. TYArenews ita experience in phosphate SlleltiDg. Ob_. Met.lIlg. v 45, pp. 116-120 (19.38).

(7) Curtis, B. A... lI111er, A. 11., and .Iewton, R. H. Process develop­ .ent. at TVA plant. Cbem. Met. mg. v 45, pp. 19.3-197 (1938).

(8) lewton, R. R. TVA's phosphate smelting results. Ch_. Met. !Dg. v. 45, pp. 374-379 (19.38).

(9) CurtiS, H. A., and Heaton~ R. C. Design for a phosphate fumace. Chem. "t.Bag. v 45, pp. 536-540 (1938). 5 reconversion for munitions production. The management succeeded in

solving this problem in conversion. In fact, as measured by the demands of the present war, it bas added to the munitions produotion value of the plant by making it a source of munitions phosphorus as well as ammonium nitrate.

The purpose of this paper is to present a review end discussion of phosphorus as a raw material with particular reference to its com­ bustion and conversion thereby into other useful 1I&terials. The greater part of the u.tbor t s experience with phosphorus bas been in the operation of large pilot plants in which phosphorus combustion was en important factor, including the research attendant upon the development of the several proce8ses for burning phosphorus. 6 Ih!. Production sU: phosphorus .m Electric Furnaces

Phosphorus furnaces at the Wilson Dam plant were constructed in the building that originally accommodated the twelve carbide furnaces. Five of the original carbide furnaces were replaced b,y phosphorus furnaces. It is apparent, therefore, that the arrangement of furnaces for phosphorus production was controlled by the facUities existent for carbide production.

Caloium oarbide furnaces have open tops with the charge delivered to a floor level with the furnace top and loaded into the furnaces as required for their operation. Electrodes are suspended directly into the furnace, and have their lower, free-hanging ends subnerged in the burden of l1me and coke. Suction fans draw the gases from the open furnace tops. The calcium carbide is tapped through tap holes, placed near the furnace bottoms, directly into chill cars running on tracks on the floor of the fUrnace building.

The phosphorus furnaces, with closed tops, were construoted at calcium carbide furnace sitel. The electrodes tor these furnaces pass through the furnace roof, and ducts for drawing otf the furnace gases are proVided near one end and near the top of each of the tive furnaces.

Slag and terrophospborus aetal, bypI'Qducts ot phosphol"\1s production, are drawn ott threugh tap boles provided Dear the base of each rumace.

PhosPAoru@ Furnace Pesi@;

All of the elements in the general deSign of phosphorus furnaces have been presented and illustrated in a publication by members of 7 the staff of the Tennessee Valley Authority (10), and will not be re­ peated here.

The best size and shape for an electric furnace producing phos­ phorus are not definitely known. The olearance between electrode surfaces must be sufficient to prevent any oonsiderable passage of current directly from electrode to electrode. The desired flow of ourrent is from each of the three electrodes through the oorden to the ground, thus concentrating heating and melting in the bottom of the furnace and providing for the maintenance of a pool of mol ten slag and ferrophosphorus metal to be drawn from the furnace by tap­ ping. Electrodes in the Tennessee VeJ.ley Authority furnaces are spaced about 6 feet from center to center.

Cylindrical. and rectangular shapes have been used in furnace de­ sign. At the WUson Dam plant, one of the furnaces is cylindrical, and the other four furnaces are rectangular. The latter shape is favored for several reasons including the adTantage of more working space and better arrangement or feed chutes at the furnace top.

Four or the five furnaces are of 6,OOO-kilowatt capacity and the other one of l2,OOO-kUo1f8.tt capacity. Six kilowatt hours of electric energy are required to produce one pound of phosphorus, as established by many checks or energy and aaterlB1 balances in the operations of the furnaces. Thus, each of the 6,OOO-k1lowatt furnaces produces

12 tons, and the 12,OOO-kilowatt furnace produces 24 tons of phos­ phorus eaoh day. Operated at full capacity for an 11-lIlonth year

(10) See footnote 9. 8

(one month in each year is required to reline and recondition a phos­

phorus furnace), the Tenneasee Valley Authority phosphorus plant pro­

duces approximately 16,000 tons of phosphorus. (One of the furnaces

does not have a phosphorus condensiag system, and the gases from the

furnace are burned directly).

Phosphgrus l)roace ODeratiop

Rock phosphate is received at the plant by rail shipment from

the fields and washing plants in Tennessee. The operation of the

furnaces require that the phosphate be in lump (Orll, ~refore natural lumps are preferred. However, the exploitation of the

Tennessee deposits has very nearly exhausted the supply of plate rock which is broken into lumps in the mining and handling operations.

Practically all of the phosphate now used consist. of wasPed sands which must be agglomerated into lumps tor subsequ8Jlt 1188 tn the furnacea.

Bxper1aents have been JUde OD the composite aggloaeration of the conatituenta (rock pboephate, silica, and coke) into lumps for the fur­ nace burdens, rut the reaults ore not satisfactory. These composite lumps did not handle well in the turnaces. In present Qperatioos, lup phosphate, silica pebbles, and screened coke are prepared separately an~ aixed in biDs prior to charging to the fumaces.

The phosphate S8Jlds are agglomerated either by swter1Dg on

Dwight-Lloyd s1ntering machines or by' nodullzing in rotary kilns.

The Tennessee Valley Authority prefers agglomerates produced by nodu­ lizing, principally because large rotary kilns, provided originally for calcining liMstone to produce lime to be used for calciUli carbide 9 production, were ava.U.e.ble at the Wilson Dam plant. In addition, tests appeared to indicate that nodules are superior to sinter in phosphorus furnace burdens.

Carbon monoxide gas, produced as a byproduct of the phosphorus furnace operations, is used, with some powdered cou, as the ruel for noduli zing or agglomerating the phosphate sends. The practice of nodu1izing phosphate sands in rotary kilns has been developed to a very high stage b7 the Tennessee Valley Authority. One of the _jar problems, that of the formation of accretions in the kilns, bas been solved by providing mechanically operated cleDDing bars that periodi­ cally or continuously reaove deposits of fused and subsequently har­ dened phosphate fro. the kiln walla.

In producingtbe charge for the furnaces, the lump or agglomer­ ated phosphate i8 IIixed with a proper proportion of silica aDd coke to give a satisfactory slag composition. kperience has indicated that the proportions of the raw matedals should be· suoh that the

8lag bas a 8102 to ceO wight ratio of 0.7 to 0.8, and that the coke should be sufficient to provide approx1llately 0.422 pound of carbon per pound of P20') and 0.222 pound of carboD per pound-of Fe20y A small excess of coke, usually about 2 percent, is also al10wed to provide for other reducible compounds in the blrdan and to m'n11l1 ze electrode conSUllption. Various details of the calculation of phos­ phorus furnace burdens are described in an article published in 1938 (11).

(ll) See footnote 8. 10

Several reactions oocur tn the electrio furnace. Some of these are exothermic, as SOOllll below, but the overall reaction is endothermic requiring electrical energy.

Tp.blt ..1

RtV£iops ill .JU. Electd.c-lYmapt Itducttgp. gl. ~ l!lwl!pbfW

1. 2 Ca,(P04>2 + 10 -0 ~ 6 CaD + '4 + 10 00 2. CaD + 8i02 = CaS10, 3. , ceO + 2. 8i02 = Ca,Sii>7

4. OaF2 + Si02 = 2 CaD + SiP'4

5. Fe~3 + .3 C = 2. Fe + .3 00 6. Fe + P = FeP 7. 2 F. + P = Fe2P

The overall fumaoe reaotion is usually represented by the follow­ ing -.uationsl 2 Ca,(P04)2 + 10 C = 6 oeO + P4 + 10 00 and X ceO + I 8102 = (X-I) Ca.3Si~7 + (.31-2X) CaB103. It ie apparent from the second equation that variations in the ratio of silica to rock phosphate aq be aade to control the 8102 to

0.0 ratio ()f the calciUll ell1cate elag.

The energy COIlSUllptiOil in the el.ctric tumace depends upon a DUIl­

'her of variable faotors which are described below from records of ob­ eervations of the operation of the furnace plant:

(1) the PtJ5 content of the turden is the prinoipal factor in­ fiuencing the conSWlption of energy. 1Ihen the P20S content was increas­ ed fro. 25 percent to 28.~ percent, the energy coneuaption decreaeed II regularly tl"Oll 5800 to 4200 kilowatt hours per ton of pbo8pbo~s pentox1de volatUized.

(2) Increase in energy load gave an increase in productive ca­ pacity for phosphorus. Although the ..erg)" requirement per ton or

P20S reduced increases with increased load, as a r.sult of mcreased heat 10sse8, the increased capacity warrants the higher loads.

(,3) Higher voltage pel'llitted greater low without increased current deD81ti7. Higher voltage gave more efficient operation by spreading the he4ting in the furnace and by giving less electrode eonSUDlption per unit of P20S reduced. The l1Jdting factor on voltage is the safety of the furnace personnel and the carrying over of dust from the furnace. Increasing the depth of the furnaces has permitted higher voltages without increasing the carrying over of dust from the furnace.

(4) .ergy requirements are decreased bT decrease in cu.rreat denai ty. na. ux1a1l11 aUoahle appears to be .32 uaperes per square inch ot eleotrode surface. Factors pel'ldttiDg this high value with efficient eDergy utilization are careful attention to makinl good electrode joints and maintenanoe of proper turDace presllllft COIltrol.

TJpical operating CODditioo8 and a beat balance for All .lectrio turnace are aho1lJl in fable 4' 12

Table J..

Electric Puma£! QperatiAg Conditione ~~ B!lance

ORerating Copd!tionP' Energy load, kilowatts 6550 Arc voltage 125 P20; in rock phosphate and s11ica, percent 26.4 Furnace charge, tons of P20; per hour 1.41 Excess coke in charge, percent 2.1 Energy consumption, kilowatt-hours per ton of P20; charged 4635 Slag, 8i02/o8O ratio 0.73 P20S in slag, percent 1.00

Heat &lAPee: (Basis: 1 ton of P205 in oharge)

Heat Input Btu. x 1.000.000 Percent 9f input Electric energy 1;.8 100.0 Heat 9»tput Net chemical reactions 7.6 48.0 Heat in products: 2.72 tons of slag at 2727° J. 4.6 29.0 0.218 tons of ferrophosphorus at 2727° F. 0.2 1.3 0.361 tons ot P4 at 7~6° F. 0.6 3.S Oooling water: Electrodes, 4,440 lb. at 51° F. 0.2 1.3 l"umace shell, 18,300 lb. at 40° F. 0.7 4.5 Radiation and convection 0.1 0.7 Unaccounted f~r losses 1.8 11.4

Additional average operating data for an electric furnace, taken tor a three months' period of operation for the same furnace as in Table 4, are show in Table 5: 1.3

Table j, Electric Furnace Operating Data

Energy load, kilowatts 6550 kilovolt-ampere load (kilowatts/power factor) 7l2O Transformer voltage 215 Arc voltage 125 Electrode~ent, saperes 19,.300 Current , amperes per square inch 27.2 Energy consumption, kilowatt hours 13,800,000 PZ05 oharged: for entire period, tons .3000 per day-, tons 34.6 P20'> in slag, tons 80 P20'> in ferrophospborus, toRS 120 P20'> volatilized: for entire period, tons 2820 per day, tons 32.3 P20'> in rock phosphate and ailica, peroent 27.5 Energy- couS\1ll8d: kilowatt hours per ton of P20S charged 4550 kilowatt hours per toil of P20'S volatillaed 1$10 Electrode COD8UIlption, pounds per ton of

P20'S oharged 16.0 Exoes8 colte in oharge, peroent .3.9 Total days .0£ operating time 87.5 Operating tlae, percent of total tiM 97.0

The average oharge to the fumace over the test period abo_ iD Table '5 .. 33 percent rock: phosphate, containing .31.6 percent

P205' and 67 percent noduli zed rock: phosphate sands, oontaiDing

.3.3.5 percent P20'S.

!he slag 8Il4t.l'l'Opbospbo1'Ua _tal were tapped trom the fur- nace at two-hour intervaJ.a, into a carbon-liDed cnLoible wherein the aetal settled b7 gravity. The alag overfio1Md trom the lip of the orucible hto a slag-handling duct whereinlt was granulated and conveyed into a collect1ng basin by atreaas or 1algh-preseurt ste... and _ter. The terropbosphonlS _tal. W8.8 poured and cast in pig IIOlds, amd was refined to reMve sUica b7 reaelting with rock phosphate ad 11M in either a .Detroit rocking electrio furnace or a vertioal-eJ.ectrode furnace ot conventional tyPee Phosphorus CQndenaat10n m llMdling Phosphorus, as produoed in the eleotric fUrnace, is at. a tempera­ ture above its dewpoint in admixture with nearlY' pure gas. This vapor and gas mixture can be blrned direotlY' in order to oxidize the phosphorus to to be oonverted into phosphorio aCid, or, alternatively, the phosphorus can be condensed from the lli.xture and the carbon monoxide conserved for use as a fuel gas.

The characteristics and advantages and disadvantages of the two types ot phosphorus-haadlina systems are desoribed iD a pubUcation bY' CurtiS, 'tiller, and lewton (12) ot the swr of the T4D.I1essee vaneY' AutboritY'e A single furnaoe with an adjacent coabu..tioo ohamber for burning the. fUmaoe gases direotly .,s 1nstal1ed and is in operation up 1;0 the present t!Jae. Tests haYe shown, however, that no real eOOllomes 1D ' operation are realized, and phosphorus tram al1 of the other furnaces is ooa.iensed from. the gas streaa md conected in 80lid torm. EarlY' ~ the developaant ot ,phosphorus produotiOill at

Wilson Dua, it .... OOIleidered that the phosphorus might some daY' plaY' an iJIportant part in militar;y use, and, therefore would need be colleoted in so11d torm for transportation and use in theaters ot ~. The colleotion &11d purification of phosphorus has entailed oon­ siderable exper1JMDtation to evolve suitable handliDg 8Y'stems. Wet

(12) See tootnote 6. M condensation, that is, by water from sprays, orig1nal.11 appeared to be the most desirable method.

In wet condensation of phosphorus, the fUrnaoe gases are cooled, and phosphorus i. condensed b.r water froll sprays in a vertical, cylin­ drical condenser. The condensed water and phosphorus sludge is pUIlped to a Dorr thickener from wbich the phosphorus underflow is pumped to storage tanks and the water overflow back to the condenser tor use as spray liquor. "nl. residual gas, IIOStl1 carbon IIODoxide, is collected by tans and blown elsewhere tor use as fuel gas.

Various operating difficulties developed in the application of this phosphorus oondensing system. Potassiwa fluos1l1cate, gelati­ nous silioa, pbospli:lorus and dust ftOOWDw.s.ted in the reo1rcul.ating oondenser water and plugged the water pipe lines. This d1tf1qu1ty was correoted to a great extent, but not entire17, b.Y making the thickener the coldest part ot the system (by water eooJ 1n,) and thus .II&1ntaining the other batter part8 ot the 81'Steil unsaturated with respect to the soluble impurities. Also, to aid in temperature control in the system and to clean deposits from the pipe lines, steam as inj ected into the liquor return line. The most iaportant correotive treataeDt for the e1il1ination ot troubles due to impurities hae 'been the use at agglomer- a ted phosphate in the furnaces, as reduction and heating during agglomer­ ation removes much of the fluorine tro. the pbosphate, and decreases oondenser troubles.

Phosphorus losses in wet condensation also were troublesome in the operation of this type of condenser. The first method tried _s to install a tubular gas cooler in the pipe line carrying the exhaust gases from the oondenser system. Plugging and corrosion of the equipment were 16 severe. An Infilco entrainment separator was then installed. Diffi­

culties due to plugging again were too severe to be tolerated. Finally, a Nash- Hytor pump and entrainment separator of the type often used for removing condensate from the return lines in steam heating systems was

tried with excellent success. In the application of this system, the most of the phosphorus in the gases leaving the condensing system was

collected in the pump. With the installation of other electric furnaces, enditional wet condensation systems were installed with slight changes in design but retaining the Dorr thickener for phosphorus sludge and the Nash-Hytor pump and entrainment separator systems. As the work on phosphorus production progressed, it became in­ creasingly apparent that better methods of collecting phosphorus and

changes in operating technique to produce cleaner phosphorus were necessary. The product from wet condensation is a phosphorus sludge

comprising a phosphorus-in-water emulsion stabilized by dust and fluo­ . Various methods for filtering this sludge, to effect separation of water and impurities from the phosphorus, distillation,

and ohemical emulsion breaking were all tried with indifferent success. tT se of the phosphorus sludge directly in phosphorus 'turning systems multiplied operating and corrosion difficulties.

Attention was dra1Vll to the possibility of condensing the phos­ phorus from the furnace gases directly, out of the presence of water, in externally cooled tubular condensers. Small-scale work on the dry condensation of phosphorus demonstrated that the process was feasible, and the deoision was made to use this system on a new furnace then 17 being oonstruoted. The application of a dry condenser system, however, fequired that the gas must be cleansed ot impurities prior to phosphor­ us oondensation.

Gas oleansing was accomplished by the use of electrostatic pre­ oipitators in the gas lines trom the electric tUrnaoe. These were main­ tained at a temperature above the dewpoint of phosphorus in the gas by the use of external strip heaters. The system used was designed bT the

Research Corporation and was operated with eminent sucoess. Removal of the aocumulations of dust from the preoipitator dust bins and oontami­ nation of the oil used in the oil-seal system caused some difficulty. is finally evolved, the dust was periodically fiusbed from the colleo­ tors with water, and the seal oil, when contaminated with phosphorus, was purified by treatment with sulfate and soda solution.

PreCipitation of moisture on the precipitator wire insulators caused aroing and severe oracking of the insulators and a forced sbutdom to replace them. To prevent recurrence of this difficulty, steam coU. were placed in the air ooapa.rtment surrounding the insulators to heat the air and prevent the oondensation of lIOisture on the insulators.

Temperature oontrol in the condenser proper proved to be _17 oritioal. If too much cooling water was used on the external. surfaces ot the condenser tubes, phosphorus frose within the tubes. This, however, was the ouy serious difficult,. and was remedied by install­ ing a recirculating counter-current cooUng water syste. with a con­ trolled inlet te.perature of 110· F.

In ~ocessfUl operation, the heat transfer on the condenser tube surrace was 2.5 Btu. per hour per degree Fahrenheit per square foot. 18

Phosphorus recove17 in the tube units amounted to about 70 peroent, and the reaainder of the phosphorus was entrained as droplets in the gas stre8Dl leaving the units. Entrainment of phosphorus is primarilY' due to rapid cooling which results in fog formation. Also, turnace puffing due to slippage of stock and other reasons blew phosphorus from the surface of the tubes into the exhaust gas line. In entra1n­ llent separator of a balfie-wall type was installed in the exhaust line froll the condenser and served to collect about 10 to 15 percent of the total phosphorus.

The complete success of the above system of d17 condensation of phosphorus depended upon the efficiencY' of the Hash-Hytor exhaustor

PWllp as an antra1mlent separator. It collected up to 25 percent of tae total pbosphonts. Aa the pap is construoted of corrosion-resistant metal, wat.r i. reoirculated to it and drain. with the pho.,horu8 con­ densate to the coUection tank.

Atter several ;rears of operation, the following OOIIp8ri8OGS can be aade of phosphorus coUeotion b7 .... t and dr)' oondenser systells:

Wet condenser" are JII\IOh more nex1ble than drr coodensers and are less seDsiti ve to fiuctuations in tumace operatioo. lumue potts place a greater load on the Bash exhaust pump of the dry s1stea. lD the drJ systea, it ia necessary to Rut do. the anti" furnaoe systell to olean ooDdeDser tubes ol' to repair leaks. Dry- oondenser s18tems have lower initial and depreciation costs and lower maintenanoe cost due to the excessive liquor eyatea aaintenanoe o08t of the wet l!Iystea8. In­ stallation of electrostatio precipitators to cleanse gases before con­ densing phosphorus in wet B1st_s, however, ma:y equalize the JlBinte- 19 nance costs of the two kinds of systems. A slightly greater phosphorus recovery has been obtained with the dry systela than with the wet system.

Phosphorus, atter condensation and co11eotion, is stored usually in underground concrete storage tanks. It is, when necessary, stored in steel tanks above ground, and is shipped in tank cars aad tank wagons. Submerged pumps are the most practical method tor delivering phosphorus froll underground tanks • . Where practical, phosphorus is customarily JIOved from tanks by water d1sp1acaaent so that the pwIp8 handle water rather than phosphorus. Brass lines have proved highly resistant to corrosion troll fiowing phosphorus. These lines at first were steam jaCketed, but present practice is to wrap the lines wi th steam tracers under insulation. Plugging of lines and attendant ditfieultie8 are frequent in the handling of dirty phosphorus. .ter­ ing ot phosphorus has Men very difficult due to its low vi8oosit1 in the _lta tom. In pUot-plant operations, it is de1i... ered by _ter displaoell8llt, and the water now is ..tered (13).

(13) In the discussion of the produotion of phosphorus in e1ectric tumaces, in addition to direct obserTation, IlUch of the data pre­ sented was gathered in group studies ot operating phosphorus units. Additional data M.7 be obta.1ned. troa published papers, eepeciall1 those mentioned in footnotes on page 4 of this thesis. 20

The Properties ~ Phosphorus

Phospborus exists in It least four well-recognised modifications.

These are usual.l.y described by color, and are ]mom as Yltllow (or white),

red, violet, and b1aok phosphorus. All of these probably are not dis­

tinctive allotropic fom8 of phosphorus, as there is considerable sup­

port for the belief that the red form may be a physical mixture of

white and Tiolet phosphorus. The white allotrope is definitely known.

Usually, it is contaminated with at least traces of other allotropes,

and is cOlllDOnly known as yellow phosphorus. Bed phosphorus has been

known and manufactured for years, but very little progress has been made in iaproving prooesses for its produotion OD a very large scale.

Whi te phosphorus is altered to red phosphorus bT heating under Tery

care.fUll7 controlled conditions. Violet and black pboaphortll are com­

paratiTel,. stable fol"llls about which little is lmown. Red, black, and

Tiolet phospborus are progressively more stable than white- phosphorus.

A thorouch discussion ot pbospbol"lll and its principal. oldAes is

presented in standard treatises on cheaistry (14).

So.. of the thel"ll8l properties of phosphorus and phosphoNS

pentoxide are shown in the following S1DIIII&rY=

. Heat ot fusion ------3.0 Btu. per cu. ft. at 600 .,. fusion temperature ------1110 F. Heat ot vaporisation ----- 76.5 Btu. per cu. ft. at f:J:J0 .,. Boiling temperature ----- 5350 F.

P205: Heat ot eublillation ----- 41.75 Btu. per cu. ft. at f:J:Jo r. Subllaation temperature --- 680° .,. The heat content ot pbospbons and phosphorus pentoxide vapor

(14) Mellor, J. •• A comprehensiTe treatment ot inorganic and theo­ . retioeJ. ehelllist17. lew impression, v 8. H.Y., Longmans-Green, 1940. pp. 771-782. 21

and the heat contents of other gases involved in phosphorus combustion

processes have been calculated from data in the International Critlcal

Tables and various engineering handbooks, and are shown in Figure 1

in a form found convenient for aaking phosphorus coabustion calcula­

tions.

The readiness with which phosphorus aay be oxidized to the

tact that It -1' be blrned in the presenoe of other OOIDblstible gases,

suoh u - oarbon monoxide 8Dd l:qdrogen, without cOilrustlon of those

gases. lhlder certain cOllditlons, to be discussed later in this thesls,

. it may be oxidized with to produce phosphorus oxides

and oarbon monoxide, or with water or steaa to produoe phosphorus

oxides and .

In erf.ot, therefore, the combustion ot phosphorus maT be aooas­ plished in three waySI Coaplete -OOIIlbwitiOll in air.

entlal oxidation in the presence ot other combustible ga•• s.

l IJ b¢ ~ V ! '- j l' Z ~ /20 V , t ~ ,,' f;. v;.~"'4 ~ "L / I/~ s- Y- J ' /.;;q ~ ; ~ I Till r- /00 , V "7 - r-~ \1 /COp / 1-- V I • L '10 0( I r;7, 37i~/ { "/ /' /"'~O b(l -' 1 v.. y.';,~ 'I I r/. I 1.7. I // VII Y. ~ 7 V 611 / ' Yt >1 Yo /' Y ~~2--J "')1 ::... 50 7 )/ /' ~~~J.ICO"':J ~ I 1./ ' IA V. ~ H y 7./ ~ "2- Ir Z ~ /7 ~ /171 ~ b::?I , 9.-.t:t~ ~~ ~ I ~!,..o~ ~~I L~'V""'"/" - ~ii"'" ' ' I~ ~ ~ ~y Jh~ ,I o r-~ Tt: "',IIe ,-A J.IA. r- e- G f1 re .1.800 J'~ ~2OD -31 0 o FJ'IJR£ /- !lEAT CONTEAlT OF LfA5ES FROM ?1I()SfJ/tJI?US COMBUSTION FURNACES 2.3

The ComWstlon 9!. Phosphorus iJ!. Air.

Phosphorus, in uncondensed fOrll as a product of the electric­ furnaoe reduotion of phosphates, is present in a gaseous mixture con­ taining 8 to 8.5 percent phosphorus, 80 to 90 percent carbon monoxide,

1 to 5 percent water vapor, hydrogen, , and carbon dioxide; cer­ tainly at least traces of phosphorus trifluoride and pentafluoride and phosphorus oxyfluoride (PO'.3)' and probably traces of arsine, phos­ phine, and various phosphorus oxides.

In present oommeroial. operations, the phosphorus plus other combustibles may be burned completely, or the phosphorus may be con­ densed, as described in the previous section of this thesiS, and burned separately. In either praotice, the reaction is the oxidation of phosphorus by oxygen in air.

fgpphprua ImitJ,on: Phosphorus ignites spontaneously in air at noraal. atmospherio tea.peratur.s. Early inY8stigati0ll8 (15) have shown tbat the ip!tlon of yellow phosphorus is aooelerated by rari­ tioatloa and retarded b.1 compression of the air supplied for the combustion. Under the cond1tioa of raritioation ot the air, a sub­ onde, the trioxide, the tetroxide, and 80118 red pbosphorus. may be formed, in addition to pbospaorus pentox1de. The writer has deteot­ ed of' phosphorus ill the exhaust gues trOll phosphorus com­ bustion f'urnaees operating, with an insuffioient supply of air for the complete oxidation of phosphorus to phosphorus pentox1de. When phosphorus is burned with an excess of air, it is converted COII-

(15) See footnote 14. 24 pletel)" to phosphorus pentoxide.

When a considerable quantity of air at a low temperature i8 passed over phosphorus, a slow oombustion occurs to produce a slight elevation of temperature Which gradually accelerates the reaction until the phos- phorus finally bursts into fiaae.

The ignition of phosphorus is acoelerated b.1 a great variety of substances, includingI ammonium, , and calcium chlorides; anti- mony and ; bariam hydroxide; borio acid; calcium oarbonate and lime; charcoal and lampblack; fiuorspar; magnesia and ; hydroxide; silica; and sodium nitrate. Any conditions whioh hinder the diSSipation of heat generated during oxidation or hasten the rate of oxid.ation cause phosphorus to ignite.

Zagvozdkin and Bar1l.ko (16), reoentl)" oollected oper1.llental data on the rate. of oxidation and the cOIIlpo.aition of the products f01"ll8

The reaults of these exPer1aents are sho1lll in Table 6:

(16) Zagvosdltin, It. I.~ and Bar1lko, N. A. Rates of oxidation and oomposition of produots in phosphorus oxidation.. J. Ph7S. Chem. (U.S.S.R.) v 14, pp. 505-512 (1940). C. A. v 3~, p. 2058. 25

T,able ~

1Q!. Relative AmountJ! R! ~ Qrldes 9L Pho@phorus frqduced

.Pz J&rnj,pg Ppo@phorns ~ Air

Temperature, W!lght p'@rce!t oc. P4010 P406 P402 P40 12; 35 3; 4.7 - 0.6 28 250 35 19 0.9 - 4.0 20 .350 75 14 0.9 - 0 • .3 10 450 88 12 0 0

Zagvozdkin and Bar1lko proposed that their data might be explained by the following equations for the first stage of the oxidation:

1. P4 + 0 = P40 2. P40 + 02 ::: P402 + °

3. P402 + 02 = P404 At low pressures, the second stage or the oxidation may be repre-

.ented by the following equations:

4. P404 = 4 PO

5. PO + 202 = P02 + 03 6. t P02 = P204

7. P'iP4 + 0,3 = P20; + 02 At higher pressures, P404 adds 02 to produ.ce P406' P408' and

P 4°10. , one or the 1ntemediate products in the oxidation of phos- phorus, was also observed by lishbeck and Rich (17), who stated that it

(17) Fishbeck, K., md Etch, H. The ozone reaction in the oxidation of phosphorus. Bar. v 7lB, pp. 520-532 (1938). c. A. v 32, p. 44l4. 26 is produced by the reaction of phosphorus with oxygen.

Semonov (18), in an evaJ.uation of numerous earlier investigations , described a critical pressure of oxygen in the oxidation of phosphorus.

He showed that this critical pressure, Pk, is related to the partial pressure of phosphorus, Pp 4' by the expression, Pk -.J Pp 40 equals a constant.

Also, he found that Pk\l + l!aI(P k + Pa)]} equals a constant, when another material, a, exerts a partial pressure, Pa.

A valid relationship between the diameter, d, of the reaction tube, and the constant, Pk , is fO'lUld in the expression, Pkd.3/2 • . This latter relationship is independent of the temperature, ex­ cept insofar as it affects the partial pressure of phosphorus.

The data of' SeJROnov were reconciled by him with the following conoepts relative to the oxidation of phosphoruea

1. The reaction between moles of P4 and 02 is not inetantaneous. 2. The reacting moles are in an aotivated state, and may iose their activity by shocks against the walls of' the reaction chamber •

.3. The reaotion is a chain mechanism which proceeds veFY slowly because of the small number of reaction centers, and could become exploeive under certain conditions.

Booy (19) demonstrated the exis.tence of' two pressure lbdts of oxidation of' phosphorus, by the aid of the mathematical concept of chain reactions, and found that the presBUre limits of oxidation .of phosphorue are quite comparable with the explosion lillits in explosive gas mixture••

(18) Semanov, It. The oxidation of phosphorus vapors at low pressures. J. Phys. Chem. (U.S.S.R.) v 46, pp. 109-1.31 (1927). C.A. v 22, 901.

(19) BoOT, I. J. Explosive gas reactions. Ree. trav. chim. v 49, pp. 866-875 (1930). C.A. v 24, p. 5159. 27 Melville (20), studied the effect of inert gases in chain re­ actions, uSing hydrogen, methane, hydrogen , carbon disulfide, phosphine, and phosphorus. He fO\Dld that the inert gases accelerate the oxidation of the lighter 1lO1eeules more than that of the heavier , and that the velocity of the chain reaction is inversely proportional to the diffusion coefficient of the chain through the gas mixture.

King and Ludlam (21), in studying the chaiD theory of o:d.dation of phosphorus vapor, found that deuterium and helium are almost equivalent in their capacity to prevent the explosion chain carriers from reaching the walls of the reaction chamber, and that hydrogen is less efficient. The ratios for the retarding effect are: H2:D2sHe = 1.00:1.30:1.32. They found that illumination of the gas mixture with , from a spark or a llerCUl7 are, below the lower explosion limit, (a) displaced the lower liJllit to lower pressures and

(b) induced reaction between phosphorus and oxygen below this limit.

The displacement is a wall effect, probably due in the first place to dissociation of P4 to P2 • The displacement is not permanent, blt slowly decays as the reaction Id%ture is illowed to stand before being eXploded. U1 traTiolet light raised the upper explosion limit. As this could not be explained as a wall. effect, it was interpreted as resul ting from the production of P2 molecules. The rate of the stable reaction is proportional to the pressure of P4 and to the square of

(20) Melville, B. W. Inert gas effects ill cba1r1 reaotions. Trans. Paraday Soo. v 28, pp. 814-118 (1932).

(21) ICing, D. W., and Ludlam, E. B. Chain theory of the oxidation of phosphorus vapor. J. Chem. Soc. Part II, pp. 1500-1503 (1938). 28 the oxygen pressure, although independent of the pressure of the inert gas.

The foregoing general concepts of phosphorus oxidation will be elaborated later in the discussion of special cases of oxidation, i.e., preferential oxidation and oxidation with water.

For the present discussion of phosphorus combustion in air, it is important only that the following requirements be established:

(1) Phosphorus is burned almost completely to phosphorus pentoxide (p4010) in the vapor state, only in the presenoe of excess air.

(2) Phosphorus combustion in ,air is a slow chain reaction and ample combustion space must be provided for cOlipletion of the reactions.

(3) Phosphorus is burned best when it has been vaporized prior to combustion.

Industrial PhosphojtU8 Burners

Two important industrial processes utilize phosphorus combustlOD as 8Jl essential. item in their operation, i.e., the Dl8Dufacture of phosphoric acid and the manufacture of the metaphospbates.

Prior .to the elucidation of the principles lnv.olved in the com­ bustion of phosphorus, 1IlBll)" trials were made of various kinds of phosphorus burners. These were JIOstlT based on the belief that, inasmuch as phosphorus ]1&7 be handled in the liquid state in JlUch the same wq as fuel oU or other liquid fuel, it might readily be handled in a liquid­ fuel bu.mer. Most early attempts at blrning phosphorus without prevaporization were failures. It was fo~d that the phosphorus, uaually containing water and other impurities, is highly corrosive to

.etale and that lIlet.all.io burner tips are rapidly corroded away. Water- cooling of the burner nozzles failed to afford much relief, and a burner designed so that seoondary combustion air cooled the nozzle was not much more successful. However, in spite of the fact that burner nozzles are oorroded and must be frequently replaced in service, they are used in pilot- plant installations aDd elsewhere when their short life is not a very great economic factor. In these in- stances, they are Simple, inexpensiVe, nipple- type burners.

The most notable advance in phosphorus l:urning came about when

it was accepted that phosphorus should be vaporized preliminary to

19ni t1on.

Three patents granted to individuals who have been intimately associated with the solution of the problem of burning phosphorus are

abstracted below to show how the problem 1s handled: Phosphorus vaporizer (22) L1quified phosphorus is introduced into a confined zone and continuously vaporized, thoroughly mixed with excess air OVer that required for complete oxidation. The proportion of phosphorus vapors to air is controlled by regulating the temperature of the liquid phos-

phorus, as by externally heating the vessel in which 1 t is oontained. Oxidizing phosphoruS (23) A primary air supply is used sufficient to vaporize all of the

phosphorus and suffioient to oxidize only a limited amount of the

phosphorus. A secondary air supply is used in amount sufficient to

(22) Zinn, R. E. Phosphorus vaporizer. U. S. patent 1,991,916. Assigned to Victor Chemical Company (1935). (23) JunkinS, J. N. Oxidizing phosphorus. U. S. patent 2,125,297. ASSigned to the Tennessee Valley Authority (1938). convert all of the partly oxidized and unoxidized phosphorus to phosphorus pentox1de, and to form a hot gaseous mixture containing the latter. The operation of the process oomprises introduoiJlg the phosphorus into an uncovered liquid-confining zone substantially centrally- located in a surrounding gas-confining zone, passing the primary air in heat-exchange relationship with the bot gaseous mixture containing phosphorus pentox1de. The heated pr1.mary" air is admitted tQ the gas-confining zone immediately above the surface ot the phos­ phorus contained in the llquid-eontining zone to form a gaseous mixture ot partly oxidized and unoxidized phosphorus. The secondary air is ada1tted to the gas-confining zone 80 that it will be mixed with the gaseous mixture of partly oxidized and unoxidized phosphorus to form the hot gaseous mixture oontaining phosphorus pentoxide which is passed in heat-exchange relationships to both the primar,y air and the liquid­ confining zone.

The prooess comprises treating crude phospborus containing solid impurities in a vaporizing chamber containing an atmosphere of vapors of phosphorus and oxldized phosphorus. The crude phosphorus and air are continuous17 injected into the chamber, whUe aaintdning the quantity of air eupp;Lied at such an amount that the o~gen content is only a minor part ot the amount theoretically required for complete oxidation of all of the phosphorus. The amount of air used is sufficient to main­ tain the teaperature ot the partly oxidized combustion produot. above the fusion point ot the se1idimpuritles associated therewith, ot the order Qt 9000 to llOOo C.

(24) Almond, L. H. The oxidation of crude phosphorus. U. S. patent 2,221,710. Assigned to the Tennessee Valley AutBority (1940). .31

Industrial Prooesses UtUizinS Phosphorus Compustion

The combustion of phosphorus to produoe useful products is best exemplified in the phosphate fertilizer industry and b.Y the engineer­ ing developments of the Tennessee Valley Authority. The publioations that are oited below traoe the development of the electric- furnace method for produoing phosphorio aoid and ooncentrated superphosphate

(25), calcium metaphosphate (26), and potassium metaphosphate (27).

As is shown by Figure 2, the combustion of phosphorus in air is the starting point for manufaoturing eaoh of the aforementioned materials. This oomposite scheme of manufacturing phosphate ferti- lizers represents the status of phosphates produotion processes at the Wilson DBa plant of the Tennessee Valley Authority. One pro- oeS8 for manufacturing conoentrated superphosphate and two processes for manufacturing calcium metaphospbate haYe been in operation in tul1-scale plant units for several years. A prooess for manufactur- ing potassium metapoosphate bas bean operated on large pilot-plant soale for several years.

Ppgsphoric Acid 1Ianufaotm:e: '!'he produotion of phosphorio aOid, as a separate operation, is required only for the production of con­ centrated superphosphate, a product of reaotion of the acid with rock

(25) CurtiS, H. A. General. Outline of activities. Tennessee Valley Authority, Department of Chemical EngineeriDg. Chemical Engi­ neering Report 110. 1. Treasurer's Office, Tennessee Valley Authority, Knoxville, Tennessee (1940). Also see footno'\es 2-9. (26) CurtiS, H. A., Copson, R. L., and Abrams, A. J. Jletaphosphate investigations aim at cheaper fertUizers. Chem. l.t. Eng. v 44, pp. l4O-l42 (19.37), and Manufacture of caloium meta­ phosphate ill a full-soale unit. Trans. Am. !nst. Chem. Engrs. v.34, pp. 287-313 (19.38). (27) Copson, R. L., Pole, G. R., and Baskerv1ll, W. B. Development of processes for metaphosphate produotions. Ind. Fng. Chem. v 34, pp. 26-.32 (1942). WAT£/f ) PHP~:/ldl/c ~ IIYPKATIJR elf) ... MIXER ~ 5(/f£~p#oSPHATE 787. I/.;J'lJ 4 r ~8~&"5

i 81)cl( 1'/ldSPIIATF) PfIOJPHI/{US. CALC/VM

PHpJPlldRPSBIllIE!? PEmKlIJE ... REACT/P'; M£rA!?Nasf/IATE 7' ~ ~1g~ , UNIT 62.% f,.t'J

PPTAjS/vHCl/ttJKlPE.., pdrAS5/fI/t-1

!1fi"f~Plto>P/lAT£ '7 REAcn(J~ VNIT ~ ~5~/i05' 3>'Z !Go

1 - IIrp~ocHbRIC, , I1CIP

- F/6I1RE 2. - PllosPIlATE rElrnLIZEKS I'1AP£ 8r PII1J5{JlltJRII.5COH81.15T/IJ/V PRocESSES 33 phosphate. Beyond this, however, orthophosph&ric acid and sW1.ar acids of phosphorus are likely to become increas1ngly iIlportant as industrial acids. Among the new applications of phosphoric acid i8 its use as a dehydrating agent 1n the production of nitrocellu- lose bT nitration of ootton linters. Recent research on the pro- duction of phosphoric acids is described 1n pIlblished papers (28).

Various processes for the production of phosphoric acid b,y

burning phosphorus and absorbing the phosphorus pentox1de product

in water or in acid have been applied on a large- plant scale at

Wi180n Du.

A description of a typical process tor the production of pbo~

phoria aciel i8 &8 t611ow., Liquid phosphorus nows into a hori­

zontal, refractory-lined .....pori.er. J.....n proportion of the total. quantity of air required to burn the phosphorus is adJa1 t ted to the

vaporizer, wherein just sufficient phosphorus i8 blmed. to euppl,.

the heat to vaporize the remainder of the phosphorus. !h. stream of

vaporized phosphorus,. phosphorus oxides, and arises f'roa

one ead of the combustion chamber, through a _tal duct. A reverse

turn at the upper end of the duct permits deliverr of the vapor

stream into the top of a large, OTllndrioal, horizontal phospbonls , burner. Bere, Rftlcient increment of ~ is provided to complete

the ooabu.etien of the phosphorus to phosphorus pentoxlde. The

(28) BaskervU1, W. B. The packed-tower collection of phosphoric acid. Trans. Am. !nst. Chell. l!.:ngrs. v 37, pp. 79-94 (1941). Walthall, J. B., and Striplin, Jl. K• . Superphospberic acid by ab80rptioll of phosphorus pentoJdde vapor. Ind. lIlg. Chell. v 33, pp. 995-1000 (1941). .34 resultant gas stream, consisting Gf phosphorus pentorlde, nitrogen, and oxygen, fiows through another duct into a hydrator where it as­ cends through water mist descending from sprays. Aoid formed and condensed in this unit falls to the bottom and is drained from the hydrator tower into 811 acid-oolleoting 8UIlp. Much of the acid, hOl¥- ever, is not collected in the hydrator, 8l1d asoends in the form of mist to the top of the tower, from which it is withdrawn through a duct 8l1d through an electrostatic precipitator by an exhaust fen.

The remainder of the acid in the gas stream is preCipitated in the preCipitator and then flows into the swap that delivers the acid to storage tanks.

Variations ot the schae described above are the oombination of the bu.mer and bJdrator units in a single tower and the substitution ot a eoke-packed tower for the electrostatic preolpitato~.

CODCentu~d. S"peqboSPha:tdP· "PJlt:aotuJ.!t I Conoentrated super­ phosphate (a JDat.rial oontaining abNt 48 percent phosphorua pent­ oxide, as coapared with ordiJuu7 superphosphate oontaining about

16 pereent phosphorus peIltox1de) is produced by the reaction ot pbos­ phoric &oid with rock phosphate. Various deta.1ls of the procesees developed by' the Tennessee Valle7 Autborit7 bave been desoribed (29).

(29) See tootllotea 3, 4, and 5. Oopeoa, R. L., .ewtoo, R. B., and Lindsay, J. D. Initial reaotion rate bet._ phosphate rock 8Ild phosphoric acid. Ind. Bbg. Cbea. v 29, pp. 175-179. (19.37). Bardin, L. J., Oldhaa, F. D., and Bumond, J. W. Deve10Pllent ot ~205 insolubility in phosphate Jlixtures: The formation ot fiuorapatite azui its cause. Ind. &1g. Chem. T 29, pp. 758-766 (19.37). 35 A brier description of' the operations of' manufacturing concen­ trated superphosphate i8 as follows: Acid from the aoid plsnt

(80 to 90 percent ~PO4) is puIlped to yard storage tank~ or to tanks in the superphosphate 1W.lding, where it is diluted with water or with weak acid to the desired oonoentration of 78 percent H3P04• Rock phosphate 1s unloaded from railway ears on a treatle by an in­ clined oonveyor belt, or, if the material is dry and less than 1/4 inch mesh size, b,y a Draoco pneumatio unloading system. The rook is dried if necessary, and is ground in Raymond mills to a fineness of approximately 50 percent through a 325-mesh sieve. The ground rock is transferred from the mills to sUos in the manufacturing blilding by a Holley pneumatic conveyor system.

Phosphoric aoid is mixed with the rook dust in two batoh Idxers.

The mixers are of the sigma-blade type, manufaotured 'b1 the Read lIachine17 Company, and eaoh one handles 1200 pounds of rock phosphate and produces a mix of green superphosphate eTery 10 minutes. The aotual JIlix1.ng requires on17 1-1/2 llinutes and the balanoe of the time is used for loading and unloading the mixer. The ratio of acid to rock used for the lIixtlare is varied and amounts- to from 80 to 95 peroent of' the amount of phosphGrlc acid required to react with the caO, P205' 'e:l0.31 and Al20.3 in the rock. The exact ratia, of acid for each kind of rock phosphate is determined b.1 the application of a mathematical fonmla taking into aocount the re1ativa costs of the materials and the properties of the product. ObYiously, the acid is the most expensive ID8.terial, and the least amount of acid required to give a satisfactory product is the amount used to produce the superphosphate • 36

The superphosphate leaves the mixers in the form of moist, pul- verant lumps dropped on a conveyor belt which transports it to trolley cars running on a monorail track circumscribing the inside eaves ot a storage building. The superphospbate is dumped trom the trolley oars into bays in the storage building where it is permitted to cure in piles tor a period of 8 to 12 weeks. Preliminary studies of accelerated curing processes were successful, but additional handling oosts are un­ desirable. The curing operation decreases tree acid and insoluble phosphate contents of the product, or, in other words, increases the conversion of the phosphate from the rock phosphate into soluble or

"available" form.

Cured superphosphate is taken from the piles b,y grab-buoket tractor cranes, and dropped through a grizzly onto a belt conveyor whioh carries it to the 8llperphosphate preparati.on brllding. It is then ground in a squirrel-oage diSintegrator, bagged in lOO-pound bags, and Shipped.

Concentrated superphosphate has the charaoteristics shown in

Table 7.

Ia OharacWisticB !2! Concentrated SgperphoSRbatt

Chemi0al Anal1S1s& Ijoisture Total Available Free aoid Insoluh1! £!!L lW,tore curing 48.9 47.1 4.9 1.8 21.2 Atter curing 3.1 49.7 48.2 1.2 1.5 22.1

S1!VI S~ZII Cumul~~~V! ~1[Cen~ 1Ju;o~~ ~ !!tlb l.Q sesh 2Q mesh As shipped 99.0 78.3 37 Caloium Metaphosphate Manufacture: Unlike concentrated super­ phosphate, oaloiwa metaphosphate has not y-et reached the status of wide aooeptanoe as a fertilizer m.at&rial.. Its definite advantage as a fertilizer is due to its very high content of phosphorus in avail­ able form - approximately 65 percent phosphorus pentoxide.

CalciUJll metaphosphate, as a fertilizer material, is the product of researoh and engineering development by the Tennessee Valley Auhhority (30).

Various prooesses have been devised and are being developed to improve the methods for the produotion of the metaphosphate. DeSign, operating, and economic data on ODe of these processes has been pIlblished (,31).

Natural lump rock phosphate or agglomerated phosphate fines are delivered by a skip hoist to the top of a reaction tower, and are oharged through a feed hopper into the towr where they rest on re­ fractory grates. The grates are internally cooled by a fiowing stream of water or air. Phosphorus is burned with air in a oOllbustion obaaber immediately below the grates sustaining the Wrden of rock phosphate.

The hot gases from the burning phosphorus ascend through the rook b0r­ den and by their stored heat content initiate and sustain the reaotion of phosphorus pentoxide with rook phosphate to form caloium metaphosphate;

Ca3(P04)2 + 2 Pil5 = ,3 OaP~6. The oalcium. metaphosphate, in a fused state, nows from the grates of the tower into the base of the oombustion ohamber from whioh it is periodioally tapped. The auld metaphosphate, on tapping, nows into a rotary cooler (externally cooled by water from sprays) where it first

(,30) See footnotes 25, 26, and 27.

(31) Bee footnote 26. .38 cools in a thin fllm and then breaks free from the wall of the cooler due to the contraction on cooling. The fi&k:elike lumps of calcium

Iletaphosphate are disintegrated, usuallY' in a cage mill, and bagged in the same waY' as concentrated superphosphate.

It is expected that better methods will be developed for the manufacture of calcium lIetaphosphate, as very- definite objections to the above scheme have been found during several years of operation of a unit, like the above, producing nearly 50 tons of calcium metaphosphate per daY'. Probably the most serious difficulty with the described process is the rapid corrosion and tailure ot the refractory grates used to sus­ tain the lump phosphate burden. , "Corhart" (high alumina, eleotrocast) refraotory- shapes were used for the oonstruction of the grates and

suffered severe corrosion. In present practioe, these refractories are faced with ziroon blocks. The zircon refraotor,y, although verY' expen­

sive, apparentlY' is the onlY' material that w1l1 resist for an,. time the attaok of the oorrosive gases and molten metapbosphate.

Another process for manufacturing calciUll IIetaphosphate, now being develoved, uses rook phosphate fines whioh are blown with air direotlY'

into the phosphorus combustion ohamber. This process has shown 80Ble promil'e, btlt has also created new difficulties. The reaotion chamber

for the phosphate tines process must be sumounted by' a coke-filled tower. The paoking of this tower is continually wetted by water or

reciroulated phosphoric acid froll spraY's to colleot and absorb phos­ phorus pentoxide produced by- the b.uning phosphorus. The aoids drip

trom the absorption tower onto the pile of rock phosphate fines blown into the :t.\1rnace. This operation is necessary to provide the proper .39 time of contact bet~en rock phosphate particles and the gaseous products ot phosphorus combustion. The major diffioulty in the tines process is

the neoessity for handling and circulating a hot phosphoric acid medium.

'i'his acid contains fluorine trom the rock phosphate and is extremely

corrosive. Research 115 in progress to remove fluorine trom the aoid, in a continuous operation, and thus deor8ase acid corrosion to reasonable limits.

Inasmuch as research and development is continuing and processes

tor the production of caloium metaphosphate have not yet attained a

state of complete oommeroial success, a more detailed disoussion cannot

be given at this time.

Potass1wn lIewBb9sphat. llanufactY.£!= Potassium _taphosphate can be manufa.otured by prooesses simllar to those for oalcium metaphosphate.

Pilot-plant development has indicated that a prooess s1mUal" to the previously mentioned fines process is probably the !lOst desirable one.

In making potassium metapbosphate b,y the process, potas8ium chloride

is blown with air into the phosphorus cOIDwstion chamber and converted

into metapbosphate by the following reaction:

2 ICl + HzO + PzOS = 2 1PO,3 + 2 HOl.

A tower filled with coke packing 1s also used in this process to

collect and return phosphorus, in the form of phosphoric acid, to the reactioD zone. The hydroohloric acid vapor, due to 1ts greater vo1a­ til!ty, is drawn from the top of the absorber tower, condensed by

cooling, and drawn through a limestone-filled tower to neutralize it.

Present research is in progress to determine methods for the utiliza­

tion of the hydroohloric acid byproduct of the prooess. One of the

.ost prous1ng methods is to use it to reaot with rock phosphate to J.o produce dicalcium phosphate. This app1ioation is still in a pioneering stage of development.

The value of potassium metapbosphate lies in the fl.~ that it con­ tains both phosphorus and p'tassium in high1,. concentrated forms direot-

1y available as fertilizers.

feriilizers from Phosphorys: The foregoing brief description of the

development of processes ~ the Tennessee Valley Authority is supplied

in explanation of Figure 2, which aims to show the relation of phosphorus

combustion in air to the development of fertilizer processes.

Not all the of the fertilizer materials mentioned above have reached

tne status of unqualified acceptance by agriculture, but definite advances

in this direotion have ,been made within recent 1'8ars. Agricultural

experiment .tations throughout the United States and its possessions are

making extensive tests, and a considerable tonnage of the fertilizers

have been distributed to f~rs for trial under diverse ~oultura1 con­

ditions. A resume of the lllanufacturlng and distribution data, c~plete

through the year 1941... is shown in Table S. lIbnaal developlD8nt of ferti­

lizer maDufaeturing processes has been prevented, since 1941., _ to the

tremendous demand for munitions phosphorus. Table .a.

Production ~ Distribution Q!: Fertilizer .m: m (.32) (Net tons for fiscal years ending June 30 of year indicated)

Production 1935 1936 1937 1938 1939 1940 1941 Superphosphate 19,884 27,028 35,012 47,268 67,698 79,089 96,373 Metapbosphate 4,514 4,647 3,798 11,447 D1stribut1gp Superphosphate: to demonstra­ tion farms 2,209 29,806 22,644 13,464 14,438 20,115 18,619 to A.A.A. 17,119 26,2;0 50,480 62,324 68,021 to other agencies 88 26 44 70 351 Total 2,209 29,894 39,789 39,758 64,961 82,509 86,991 Jletaphosphatea to demonstra­ tion farms 414 3,867 7,901 9,254

The results of practical tests of the fertilizer materials have been favorable. Except in cases where the calcium sulfate content or ordinary superphosphate is a distinct advantage to a particular tJpe of soil or crop, the TVA fertUizers have been found to be as efficient forms as any of the older fertUizer materials.

(32) See footnote 25. .D.t. Pyterentlal 9x1datlon 91 Phosphorus

Phosphorus and carbon monox1~e, when rurned with an excess of oxygen, ere each capable of burning under contions wherein a theoreti- oal flame temperature of above 20000 C. is reached. This oondition of complete combustion may be expressed b,y the following equations.

P4 + 5 O2 = P4010 + 1,316,720 Btu. 10 CO + 5 02 = 10 002 + 1,226,400 Btu. It is apparent that if a gas containing 1 1I01e of P4 and 10 moles of CO is burned, nearly 50 percent of the total heat is not useful heat,

1. e., not heat evolved in the useful reaction of the oxidation of P4 to P4010- The tact that under certain conditione carbon dioxide, produced by the combustion of carbon monoxide, may in turn serve to oxidize phosphorus and be reduced back to carbon monoxide was ascertained by numerous investigators. IO.ugh (33), in 192.3, obtained a patent in which he stated that the phosphate material is eleotrie smelted to- gether with a sUiceous nux and oarbon or other reducing material to produce carbon monoxide and phosphorus, and that these gases are treated with a restricted amount of air to oxidize the phosphorus without appreciable oxidation of the carbon monoxide.

Br1tZke, at about the same time, alao obtained a patent for pre­ ferential orlda:t. of phosphorus (.34hthich states that in producing

(.3.3) IO.ugh,:8. G. Ilectric furnace oxidation of phosphorus. U. S. patent 1,46.3,959 (1923). (J4) Britzke, I. Power gas and phosphorus_ Brit. patent 229,768 (192.3) • phosphoric acid by treatment of phosphates with silicates and oarbon

in a shaft furnace, the oxidation of the phosphorus present in the

evolved gases is effected with air or oxygen at a temperature of

10000 to 13000 C. so that substantially no oxidation of carbon monoxide occurs.

Emmett and Shultz (35), in 1939, performed experimental work to

establish the characteristics of the CO-C02-Pi>4-Pi>, equilibrium.

They found that in the temperature range of 8000 to 12000 C., a

gaseous mixture of phosphorus end carbon dioxide, containing more than

ll.l peroent phosphorus vapor, quickly reaches equilibrium correspond-

ing to the conversion of about 80 peroent of the carbon dioxide to

carbon monoxide. If les9 than ll.l percent phosphorus was present,

practioally all of the phosphorus is absent in the equilibrium mixture

at these temperatures, and a mixture of phosphorus pentoxide and

i8 obtained. The equilibrium in the syatem is

auoh that with equal molal quantities of the pentoxide and tetroxide,

the ratio of carbon monoxide to carbon dioxide is about 1 to 2. It was

also shown that, in the presence of rock phosphate to absorb the

phosphorus pentoxide as formed, the oxidation of phosphorus by" carbon

dioxide is complete. and the phosphate product formed is oalcium

••taphoaphate.

The 'l'ennessee Valley Authority, previous to the work of 1!Dm.ett

and Shultz, had undertaken work on the production of calciUll metaphos-

(35) Emmett, P. H., end Shultz, J. F. Oxidation of phosphorus to a pentavalent form by carbon dioxide. Ind. Eng. Chem. v :U, pp. 105-111 (1939). 44 phate, and was also interested in the possibilities of the utilization of preferential oxidation in processes for manufacturing phosphoric acid directly from gases containing phosphorus and carbon monoxide, wi thout burning the carbon monoxide. Curtis of the TVA recognized that phosphorus blast-furnace gas could be used in the stoves to pre­ heat the air blast if the phosphorus in the furnace exhaust gas could be oxidized to phosphorus pentoxide witbout lm'ning the carbon monoxide t(j) carbon dioxide (36).

FrearIOU, and Hull (37) of the '1"IA have prepared data collected after several months of smell-scele and pilot-plant work. Almost eoJD­ plete oxidation ot phosphorus was accomplished at temperatures ot ;000 to 7000 e., with the oxidation of about 1 percent of the carbon monoxide, using about 160 percent of the air theoretically required for the oxida­ tion of pbospborus to the pentoxide, ad a gas mixture containing 1 percent phosphorus and 39 percent carbxl monoxi~. Preferential oxida­ tion at 11000 C. was found possible with this gas mixture when the phospherus pen'toxide produced was reaoted with rook phosphate to produce calcium metapbospbate.

A narrower temperature range, 5500 to 6000 e. , end less excess air, 125 peroent of the theoretical, favored the preferential oxidation when the gas llixture consisted of 7 percent phosphorus and 90 percent carbon monoxide. Under the latter conditions, the oxidation of the phosphorus was substantially eomplet., and 2 peroent of the carbon monoxide was oxidized to carbon dioxide. The presence of water vapor increased the

(36) See footnote 25.

(:31) Frear, G. L., Ogg, E. R., and Hull, L. H. The preferential. oxida­ tion of phosphorus in the presence of carbon monoxide. (In preparation). 45 oxidation of oarbon monoxide, and the combustion rates required careful control, with both gas compositions. The two gas mixtures studied by' the TVA simulated phosphorus blast fUrnaoe and electric furnace gas, respectively. Having demonstrated the actual workability of preferential oxida­ tion for gases from either the blast or the electric furnace, the TVA eValuated its findings as follows:

The air for combustion may be dry or it may contain sufficient water vapor to convert the pentoxide into metaphosphoric acid. 1he combustion rate should be 0.3 pound of phosphorus per hour per cubic foot of combustion space. B.1 lowering the temperature, drying the air, and decreasing the proportion of air to combustibles, the actual amount of carbon monoxide as well as its conoentration may be increased in the furnaoe exhaust gas, thus increasing the heating value of thi8 gas and decreasing the dilution of phosphorus pentoxide contained therein.

However, the riohest exit gases produoed from the siJUulated bla.st­ furnace gas and electrio-!urnace gas contained 30 percent and 34 percent, respeotively, of carbon monoxide, due to the dilution by' nitrogen. This gas composition has a heating value of about 100 Btu. per cubic foot, or approximately the same as for the gas from the blast furnace. D!!. Reactigns .2! Phosphorus .:Jr.Uh Water

Mellor (.38) reviews the data obtained by a number of early in- vestigators who show that water can be deoomposed b,y phosphorus.

L. Gmelin and B. von Dybkowsky showed that phosphorus and water oan reaot chemioally at ordinaq temperatures, and C. F. Gross and

.1. Riggin found that the reaotion oocurs only in the presence of o~gen. T. Weyl observed that phosphorus deoomposes warm water with the evolution of phosphiDe. V. Ipatiefr and V. Nikolaie!f stated that white phosphorus and water in a sealed tube at .3600 C. yield phosphorio aoid and phosphine, and that the formation of phosphine starts at about 290° C. and 40 to 50 atmospheres pressure, as indi- eated by a break in the temperature-pressure curve. Russian researoh workers have been particularly active 1m ex- ploring the mechanism of phosphorus decomposition by water. lureodov and others (.39) obtained a patent in 1931 for a oontinuously operated autoolave for oxidizing phosphorus. Their apparatus consisted of an external thiok walled jacket end an inner oylinder surrounded by water. The inner cylinder was divided into an upper reaction ohamber and a lower ohamber subdivided b,y plates with overfiow tubes. The upper ohamber was provided with a tube for the admission of liquid phosphorus aad water, terminating in a mixing nozzle. A tube was provided for the transfer of the reaction liquid into the lower oham- ber aad another tube for the esoape of the gaseous reaotion products.

(.38) See footnote 14.

(.39) lCureodov, A. 11., Ignatyuk, V. G., and Drennov, K. A. A oon­ tinuously operated autoclave for the oxidation of phosphorus. Russian patent 27,.381 (19.31). C. A. v 27, p. 2258. 47 Frost end others reported on the results of experiments relative to the water oxidation of phosphorus, and proposed formulas for the reaotions that they observed:

The oxidation of yeJJ.o,!!' phosphorus with water at elevated :temperature and pressure (40) The oxidation of yellow phosphorus proceeds nt the same velocity as that of red JjI.osphorus, althougb the phosphoric acid produced by the oxidation of yellow phosphorus is more nearly pure, and the hydro- gen is more contaminated with phosphine and phosphorus vapors, than when red phosphorus is oxidized. Atomized phosphorus end water were pumped into the reaction vessel, with the injeotion nozzle protected from exoessive heating to avoid the formation of red phosphorus. A oatalyst conSisting of sodium hydroxide was admitted separately in the form of a cold concentrated solution. The reaction vessel was fitted with partitions to retard the passage of the reaotion mixture. The vessel was heated by stages. After an initial preheat to 3250 C., further heating was provided by the reaction. The highest yield of phosphoric acid was obtailled when the pressure on the mixture was sufficient to maintain the reagents in the liquid phase.

(40) Bushma k1 n, I. B., Ruisakov, II. V., and Frost, A. V. The oxida­ tion of yellow phosphorus with water at elevated temperature and pressure. J. Applied Chem. (U.S.S.R.) v 6, pp. 588-606 (1933). G. A. v 28, p. 3678. The oxidation of red phosphorus with water at elevated temperature and Rressure (41) As a result of experiments carried out in a -lined autoclave,

heated in a molten metal bath, Frost explained the oxidation of red

phosphorus by water using the following equations:

1. P4 + 6 ~O = 2 Hj'O,3 + 2 PH,3 2. P4 + 8¥ '" 2 R,3P04 + 2 PR,3 + 2 R2 ,3. P4 + 12 Hi> = 4 H,3PO,3 + 6 R2

4. P4 + 16 B~ = 4 H,3P04 + 10 ~

He assumed that the intermediate products, ~PO,3 and PH.3, may react as follows:

5. H,3PO.3 + H~ = HJP04 + ~ 6. 4 B)PO,3 " .3 H.3PO 4 + PH.3

7. PH) + .3 Hi> = H:IO) + .3 ~

8. PH) + 4 B~ = Hj'04 + 4 H2 The process takes place in two stages. In the first stage,

the phosphorus is dissolved according to reactions 1 to 4. In the second stage, the intermediate products are oxidized accordiDg to

reactions 5 to 8. An almost complete conversion of phosphorus to

phosphoric acid and hydrogen was obtained by heating to 4000 c.

without a catalyst. In the presence of 1 percent NiO, the reaction

was completed in 4 minutes, at 2800 C., and the liquid phase oontained 20 to 25 percent of the total phosphorus as H.3PO 4. The catalyst

arrected oaly the first stage ot the reaction. The maximum yield was

obtained when the ratio of water to phosphorus was 3. The partial

(41) Busbmakin, I. N., Ruisakov, M. V., and Frost, A. V. The oxida­ tion of red phosphorus with water at elevated temperature and pressure. J. Applied Chem. (U.S.S.R.) v 6, pp. 577-587 (1,.3,3). C. A. v 28, p. 3678. 49 pressure of hydrogen had no apparent effect on the velocity of' the reaction within the range of 35 and 100 atmospheres. The two following patents deserve to be mentioned with relation to the Dature of other catalysts used for the acceleration of the re- actions of phosphorus with water: (1) A French patent (42) makes the statement that pbosph1des, particularly those of copper and , are used as cataJ.ysts for the oxidation of phosphorus by water. The phos­ phides are prepared by' the reaction of phosphine with metallic salts distributed or suitably supported on calcined bone, coke or porous blocks of carbide, ferrosllicon, etc. (2) Miner (43) states that the reaction of phosphorus with water is effected in the presence of an alkaJ.i metal such as potassium intermixed with phosphorus in the form of a condensate.

Ipatiev and Usaohev (44) found that the oxidation of phosphorus wi th water vapor under pressure, in the presenoe of 1.00 to 9.75 N. BaCH solution, produces various oxidation produots. They found that if cough BaDR is used to form N~HP03' only H3P03 is obtained at temperatures not higher than 2250 C., while BjP04 is obtained at temperatures of above 2500 C. The sodium salt of H.3~ can be oxidized

(42) Compagnie Nationale De I14tieres Colorantes Et Kanuractures De Produits ChiJDiques Du Bord Reunies, Etablisseaent. Kullmann. Prenoh patent 635,501 (1927). C. A. v 22, p. 47)8. (43) lliBer, O. G. Oxy-compounds of phosphorus. U. S. patent 1,686,873 (1928). (44) Ipatiev, V. B., and Usachev, P. V. Oxidation of phosphorus with water at high temperatures and pressures in the presence of alkalies. J. Am. Chem. Boa. v 57, pp. 300-302 (19.35). 50 comp1ete1,. to Hj03 or HfO4 (without the evolution ot PH3) ~ depending upon the amount of NaOB used and the temperature.

Ipatiev and Freitag (45) explained the oxidation of phosphorus by water at elevated temperatures and pressures by the tollowing equations:

1. P4 + (3 + n) Hi' = PZl3.nBi> + 2 PH3

2. P203.n¥ + 2 HtJ = P205.~O + 2 H2

3. 2 PH, + (5 + n) H20 = P205.nHiD + 8 H2 Over a period of considerable time, they found that only phosphoric acid and hydrogen are tormedz

4. P 4 + {lO + 2n} H20 = 2 P20 5.nB.20 + 10 H2•

The ettects ot variables were studied between 1750 and ;.200 C. and between 20 end JJO atmospheres pressure. The velocities of ill ot the reactions lncre,sed with higher temperature. In the absence ot catalysts, temperatures of about 2800 C. 8Ild higher were e&s&sentiel for the oxidation ot PtJ3' the tirst reaction being the most rapid. Metallic salts, especially those ot nickel and , but also sUver, copper, and iron, showed marked catalytic activity. Small quantities ot nickel nitrate made the reaction go to completion in a short time, at 2000 C.

A. French patent (46) states that phosphorus is oxidized b,. water vapor either IliDd or not mixed with air~ in the presence ot binary-, tertiary, or quarternary metallic oollpO'Ullds ot sUicon, such as sl1i- eides ot copper, double sUicides of nickel and copper, or triple si1icides of irGU, copper, and nickel.

(45) lpatiev, V. N., and l"reitag~ C. Ox1.datiGn ot phosphorus with water at elevated temperatures and pressures. Z. anorg. al.lgem. Chem. v 21S, pp. 388-414 (1933). C. A. v 28, p. 1594.

(46) Compagnie Nationale De lIatieres Colorante&s Et Manufactures De Produ.its Chiadques Du Nord Reunies, Etab1issemente Jtuhlmann. The oxidation ot phosphorus. French patent .635,432 (1927). c. A. v 24, p. 697. :nut Qadation 9l.. Pbosphoru( .l!iY! Steam

Based on the investigations of the reaotions of phosphorus with water, considerable interest now exists relative to the possible development of paactical prooesses for oxidizing phosphorus with steam. Conceivably, a process might be evolved using equipment similar to that used in the produotion of calcium metaphosphate and produoing hydrogen gas as well as the metaphosphate.

Liljenroth (47) obtained a patent on a process for oxidizing phoaphorus with steaa at a temperature of 10000 C. Brunauer and

Shultz (48) investigated the reaction in the presence and absence of rock phosphate. The latter investigators concluded that when phos- phorus is oxidized by steam at 10000 to llOOo C., the products of the reaction are not merely phosphorus ~toxide and hydrogen, 1::uta180 phosphorus tetroxide and phosphine. Since compounds of the 10wer oxides ot pbospborus are harmfu1 to plants, these must be el;J.mtnated if the oxidized phosphorus is to be used for the manufacture of fertilizers. If the hydrogen is to be used for the synthesis of ammonia, the phosphine must be removed as it poiSons ammonia-synthesis catalysts. Both of these undesirable products are eliminated if the reaction ot phosphorus with steu occurs in the presence of rook phosphate; the tetroxide 1s oxidized to pentoxide, which in turn reacts with the rock phosphate to give calcium metapbosphate, and the

(47) Liljenroth,". G. Oxidizing phosphorus. Canadian patent 247,164 (192S); U. S. patents 1,594,372 (1926) and 1,673,691 (1928).

(48) Brunauer, S., and Shu!tz, J. F. The oxidation of phosphorus by steam. Ind. Eng. Chem. v 33, pp. 828-832 (1941). 52 hydrogen becomes free of phosphine.

These findings of Brunauer and Shultz appeared to indioate that the process might be a successful one, and research was undertaken.

The heat requirement of' the process appear to be excessively high for the direot application of steam oxidation of phosphorus in furnaces of present design.

An approximation of the additional heat required for the oxida- tion of phosphorus by steam in a calcium metaphosphate f'urnaoe was prepared by the author of this thesis, and is eho19Il in Table 9.

In this table, a heat balance for a calcium metaphosphate furnace using air for the cOllb1stion of phosphorus (49) is compared with a similar balanoe that would be effective if a mixture of air and steam were substituted for air alone.

In making the substitution, it was assumed that the Ilixture of air and steam would be exactly proportioned to give an eJlhaust gas from the furnace containing 3 moles of h1drogen for eaoh mole of nitrogen, and thus result in an exhaust gas mixture suitable fQr the synthesis of ammonia.

'!'he datum temperature for the heat balances was 320 F. A value of 79 percent excess air was assumed when air alone was used for the eomblstion of' phosphorus, and a value of 150 percent excess air when the mixture of air and steam was used. The temperature in the com- bustion challber was 19600 F.

(49) CurtiS, H. A., Copson, R. L., Abrams, A. J., and JunkinS, J. lie Full-scale production of metaphosphate achieved at Wilson Dam. Chem. Met. Eng. v 45, pp. 318-322 (1938). 53

Table .2-

ComparatiTe ~ Bal.anoes Em Burning Phosphorus .!Uh!!!:.sm

:!.U.b. .!. Mixture 2! Ai.l: l!:rut Steam JA. A Metaphosphate Furnace

!!r 2&da~~on Ak + steam 2~dation Input: Ton moles Btu. iJ 106 Ton moles Btu. X; 106 P at 1670 F. 6.2 0.5 6.2 0.; H~O at 1670 F. 2.7 0.7 2.7 0.7 Air at 800 F.: J 2 4~.4 1.16 4.0 0.1 14.2 0.34 1.18 0.03 ~o 0.6 1.3 19.2 44.7 Rock phosphate at 800 F. 17.; 0.3 17.5 0.3 P (heat or combustion) 131.7 26.9 A!ditional beat required 62.71* Total 136.0 136.0

Output a

Exit gases at 15500 F.: 47.4 36.9 4.0 3.1 0.85 9.1 ~ 6.3 4.9 ~o 3.6 13.1 11.55 42.0 CaP206 at 19.400 F. 30.5 36.1 30.5 36.1 Heat losses: Taporizer shell 12.3 12.3 grate cooling 10.4 10.4 radiation and conTection 16.0 16.0 unaceounted ror 6.,3 7.0 Total 136.0 136.0 * This represents the additional heat requirement for the operation or the 87stem using air plus 8team for phosphorus oxidation. 54

The combustion of phosphorus in air is represented b,y the equation:

~ (solid) + 5 O2 (gas) = 2 PiD5 (solid) + 1,316,720 Btu., and the

combustion of phosphorus in a mixture ot air and steam is represented by the equation:

P4 (solid) + 0.74 02 + 2.84 N2 + Ca3(P04)2 = 3 CaP206 + 2.84 N2 + 8.52 H2 + 269,270 Btu. A comparison of the two heat balances shown ta fable 9, indicates that there is an additional heat requirement of 62,770,000 Btu. for the

prooess when using air plus steam oxidation. Supplying this additional

heat appears to be the major difficulty to be overcome in the applica­

tion of steam oxidation for phosphorus oombustion in a metaphosphate

furnace of present design. In the solution of this problem, some of the

required beat might be added as superheat in the steam used for oxi­

datIon, but the balance of the heat would need to be furnished to the

system by other means, possibly b.r increasing the thermal insulation. Research is in progress to develop a suitable furnace and satisfactory conditions for carrying out the process.

A promising possible development in connection with the utilization

of steam oxidation of phospho1"\ls in the presence or a solid phosphate

(phosphate, other than rock Pllosphate might be used) 'WOuld be the pro­ duction ot a product containing both ammonium and potassium meta­

phosphates. A product of this character might be designated as It(NH4)P206' and 1IOUl.d oonta1n 22.9 percent potaeh.(lf), 6..s percent

nitrogen (82), aud 68.8 percent phosphoric acid (Pi>5)' or a total. of 98.5 percent active fertilizer material, in the terms in whioh these are usually expressed. Obviously, also, the relative propotions of 55 potash and nitrogen might be varied as desired between the limits of potassium metaphosphate and ammonium metapbosphate. The synthesis of ammonia from the hydrogen and nitrogen probably would need be done outside of the furnaoe. Potassium metephosphate eontaining an exoess of phosphorio acid might be produced in the fur­ naoe and this produot then might be neutralized with gaseous ammonial

KP03 + HP03 + NH3 = K(NH4)P206• That this would be praotioal 1s demonstrated by the faot that in present fertilizer-manufaoturing operations ammonia is us~ to oondi­ tion or neutralize the free aoid oontent of phosphate fertilizer oompounds, inoluding both oaloium and potassium metaphosphate.

On the basis of past experienoe, it appears probable that some very signifioant developments will be made utilizing steam oxidation or phosphorus in conneotion with the manufaoture of metaphospbates and other phosphate materials. 56

An. Evaluation of Phosphoru~ Combustion Prooesse.s

The developments in the science of utilizing phosphate materials, espeoially during the past ten ye~r., have brought phosphorus to the status of an abundant industrial raw material. Prior to about 1933, it was produced only on a oomparatively small scale and used b.1 in­ dustry in limited quantities. The effeots of its u~e in chemical warfare in the present war are tremendous, and it will have many new industrial uses when the war is over. Inasmuoh as phosphorus is used mostly in the form of its oompounds, a large number of new prooesses and refinements of old prooesses have been developed for oonverting it into its compounds. Phosphorus is produoed either in the eleotric furnace or in the blast furnaoe in a vapor form aocompanied b.1 a large quantity of carbon monoxide. Although the entire gaseous furnace produot may be burned to convert the phosphorus to its oxide, this treatment is basioall,. uneoonomio as the carbon monoxide is a valuable fuel. It is for this reason that the phosphorus is separated from the fUrnace exhaust gas and handled and burned separatel,.. In add! tion to the oonservation of. the gas heating value, the isolation of solid phos­ phorus in phosphate prooessing has mad. available supplies of the material for use in warfare. The comparatively new developlent of preferential oxidation of phosphorus will probably enjoy" wide use in the era after the war. The process is at present in an advanoed stage of pilot-plant development, and will be particularly applioable to blast-fUrnaoe practice where the phosphorus pentox1de produoed b.1 the oxidation may be converted to phosphoric aoid and the oarbon monoxide may be burned to preheat the 57 blast in the furnace stoves. Although steam oxidation of phosphorus is still in the research

stage of development, there is a possibility that the method may be developed into a commercial process. The particular usefulness of

this form of oxidation of phosphorus appears to lie in the manufacture of metaphosphates. The process would appear to be desirable to the

fertilizer industry beoause the gaseOus produots may be used to syn­

thesize ammonia. The ammonia thus produoed could be used to make ammonium phosphates or various other ammoniated fertiliser compounds. 58

UlBLIOGRAPHY A. Book: 1. Mellor, J. W. A comprehensive treatise of inorganic and theoretical ohemistry. Second impression, T 8. Longmans- Green, 1940. pp. 711-182. B. Periodicals,

1. Brunauer, S., and Shultz, J. F. Oxidation of phosphorus b,y steam. Ind. Eng. Chem. v. 33, pp. 828- 832 (1$41).

2. Copson, R. L., Newton, R. H., and Lindsay, J. W. Initial reaction between phosphate rock and phosphoric acid. Ind. Eng. Chem. v 29, pp. 175-179 (1937).

3. Copson, R. L., Pole, G. R., and Baskervill, W. H. Development of processes for metapbosphate productions. Ind. Eng. Chern. y 34, pp. 26-32 (1942).

4. 'CuiT.'U1I, H. A. TVA makes ~PQA e1eotrical.l.T<·at Willian Dam. Chem. Met. Eng. v 42, pp. 320-324 (1935).

5. CurtiS, H. A. Kaldng ooncentrated superphosphate at TVA fertilizer works. Chem. Met. Fag. v 42, pp. 488-491 (1935).

6. Gurtia, H. A. J Cop80n, R. L. and. Abrams, A. 3. Metaphosphate investigations aim at cheaper fertilizers. Chem. let. &1g. v 44, pp. 1J.O-142 (1937).

7. CurtiS, H. A., Copson, R. L., Abrams, A. J., and JUDkinS, J. N. Full-scale production of metaphosphate achieved at Wileon Dam. Chem. Met. Eng. v 45, pp. 318-322 (1938). 8. CurtiS, B. A., and Heaton, R. C. DeSign for a phosphate furnace. Chem. Met. l!hg. v 45, pp. 536-540 (19.38).

9. CurtiS, H. A., and lIUler, A. M. Operating observations at TVA fertilizer plant. Chem. Met. Eng. v 43, pp. 408-412 (1936).

10. CurtiS, H. A., Miller, A. M., and Newton, R. H. TVA reviews its experience in phosphate Re1ting. Chem. Met. Eng. v 45, pp. 116-120 (1938).

11. CurtiS, H. A.,. "Iller, A. M., and Newton, R. H. Process developments at TVA phosphoric acid plant. Ohem. Met. Eng. v 45, pp. 193-197(1938). 59

12. Emmett, P. H., and Shultz, J. F. The oxidation of phosphorus to a pentavalent torm b1 oarbon dioxide. Ind. Eng. Chem. T 31, pp. 105-111 (1939).

13. Frear, G. L., Ogg, E. R., and Hull, L. H. Preferential oxi­ dation of phosphorus in the presence of carbon monoxide. (In preparation).

14. Hardin, L. J., Oldham, F. D., and Hammond, J. W. Development of' P20; iD801ubllity in phosphate mixtures: The formation of' and its cause. Ind. !hg. Ohem. v 29, pp. 758- 766 (1937).

15. Junkins, J. N., and Heaton, R. H. Instrumentation of a TVA electric furnaoe phosphoric acid plant. Instruments v 12, pp. 161-165 (1939).

16. lIil1er, A. II., and JunkinS, J. H. TVA estimates favorable oosts for oonoentrated superphosphate. Chem. Met. Eng. v 43, I. pp. ;83-587 and II. pp. 647-650 (1936). 17. Newton, R. R. TVA's phosphate smelting results. Chem.llet • . Eng. v 45, pp. 193-197 (1938).

18. Walthall, J. H., and Striplin, II. M. Superphosphorio acid by the absorption of phosphorus pentoJdde vapor. Ind. Ing. Chem. v 33, pp. 995-1000 (1941).

C. PIlblieations of' Leamed Societies:

1. Baakervill, W. H. The paoked-tonr oolleotiOD of phosphoric aoid. Trans. Am. !nst. Chem. T!bgre. v 37, 10. 1, pp. 79-94 (1941).

2. CurtiS, H. A., Copson, R. L., Abrams, A. J., and JunkinS, J. 11. llanutacture of' calciUll metaphoaphate in a full-scale unit. Trans. Am. Inat. Chem. Engrs. v 34, Ho. 3, pp. 287-313 (1938).

3. Ipatiev, V. H., and Usaohev, P. V. The oxidation of phosphorus wi th water at high tesperatures and pressures in the presence of alkalies. J. Am. Chem. Soo. v 57, pp. 300-302 (1935).

4. lIe1ville, I. W. Inert ias effects in chain reactions. Trans. P'araday Boc. v 28, pp. 814-818 (1932).

D. U. S. Government Publications:

1. CurtiS, H. A. General outline of activities. Chemioal IIlgineering Report No.1. Tennessee Valley Authority, Department of Chemical Engineering. 1940.

E. Foreign Publications:

1. Booy, I. J. Explosive gas reactions. Reo. trav. ohim. v 49, pp. 866-87; (1930). C. A. v 24, p. 5159. 60

2. Bushmakin, I. H., Ruisakov, M. V., and Frost, A. V. The oxidation of red phosphorus with _ter at elevated tem., peratures and pressures. J. Applied Chem. (U.S.S.R.) v 6, pp. 577-587 (1933). C. A. v 28, p. 3678.

3. Bushmak1n, I. H., Ruisakov, M. V., and Frost, A. V. The oxidation of yellow phosphorus at elevated temperatures and pressures. J. Applied Chem. (U.S.S.R.) v 6, pp. 588-606 (1933). C. A. v 28, p. 3678.

4. Fishbeck, It., and Eich, H. The ozone reaction in the oxidation of phosphorus. Bar. v 7lB, pp. 520-532 (1938). C. A. v 32, p. 4414. 5. Ipatiev, V. N., and Freitag, G. The oxidation of phosphor­ us with water at elevated temperatures and pressures. Z. anorg. allgem. Chem. v 215, pp. 388-414 (1933). C. A. v 28, p. 1594.

6. Iting, D. W., and Ludlam, E. B. Chain theory of oxidation of phosphorus vapors. J. Chem. Soc. (British) Part II, pp. 1500-1503 (1938). 7. Semenov, N. The oxidation of phosphorus vapors at low temperatures. Z. Physik. v 4h, pp. 109-131 (1927). C. A. v 22, p. 901.

8. ZagvOli!idkin, K. I., and Barilko, N. A. The rates of oxi­ dation and the oomposition of products in phosphorus oxidation. J. Pbys. Chem. (U.S.S.R.) v 14, pp. 505-512 (1940). C. A. v 35, p. 2058.

F. U. S. Patents:

1. Almond, L. H. The oxidation or crude phosphorus. 2,221,770 (1940).

2. Junk1Ds, J. B. Oxidizing elemental phosphorus. 2,125,297 (1938). 3. Uugh, B. G. Electrio turna.ce oxidation of phosphorus. 1,463,959 (1923). 4. Llljenroth, F. G. Oxidizing phosphorus. 1,594,372 (1926), and 1,673,691 (1928). .

5. Kiner, C. G. Oxy-compounds of phosphorus. 1,686,873 (1928). 6. Zinn, R. E. Oxidizing phosphorus. 1,991,916 (1935). 61

G. Foreign Patents:

1. Britzke, E. Power gas and phosphorus. Brit. patent 229,768 (1923). 2. Compagnie Nationale De Katieres Colorantes Et Manufactures De Produits Chimiques Du Bord Reuni's, Etab1issements Kuhlmann. Oxidation of phosphorus. French patent 635,432 (1927). C. A. v 24, p. 697 •

.3. Compqnie Nationale De Matieres Co1orantes Et Manufactures De Produits Chimiques Du Nord Reunies, Etablissements Kuhlmann. Oxidation of phosphorus. French patent 635,501 (1927). C. A. v 22, p. 4738.

4. Kureodov, A. II., Ignatyuk, V. G. and Drennov, K• .1. A continuously operated autoclave for the oxidation of phosphorus. Russian patent 27,)81 (1931). c. A. v 27, p. 2258.

5. LilJenroth, 1". G. Oxidizing phosphorus. Canadian patent 247,164 (1925). 62

INDEX

Page

A. A. A. • • • • • • • • • • • • • • • • • • • • • • • • • • • • 41

Aoceleration of phosphorus ignition and oxidation • • • • 23-24, 27

Accretions in rotary kilns • • • • • • • • • • • • • • • • .... 9

Achievement, ohemical engineering, in phosphorus production • • 3, 4

Aoid S'UJlp • • • • • • • • • • • • • • • • • • • • • • • • • • • • 34 Aotivity of reaction of moleeules of phosphorus · .. • • • • · . .. 26 Adaptation b.Y TVA of electric furnace to fertilizer production .. 2

Additional production capacity for phosphorus • · . . . . . • • • 3 Agglomerates •••••••••••• • • • • • • • • • • • .. . 8, 9

Agglomeration of phosphates • • • .. • • • • • • • • • • • • • 8-9, 37 Agricu1 tural experiment stations •• · ...... • • • • • • • 40 Agriculture, aooeptanoe of fertilizers by •••• • • • • • • 37, 40 Air blast of blast furnaoe •••••••• .••• • • • • • • 44, 45

Air, comoostion of phosphorus in •• 21, 23-24, 29-32, 37, 4{), 52-53 Air compartment of electrostatic precipitator. • • • .. • • • •• 17

Air, ignition of phosphorus in ...... • .. • • • • • • .. ... 23-24

Air, primary . .. .. • • ...... • • • • • • • • • • • .. . 29, 33 Air, seoondary ...... • .. .. . · .. • • • • • • • • • • • 29, 33 Air, vaporizing phosphorus in • ...... • • • • • . .. . 29, 33 Alkali metal, as catalyst for oxidation of phosphorus ••• · . . 49 Allotropio forms of phosphorus •••••••••••••• • • • 20 .bmonia • • • • • • • • • • • . . • • ...... • • 4, 51- 52, 55, 57 Ammoniated fertilizer oompounds .. . • • . . . • • • • • • • • • 57 Ammonium ohloride, as catalyst ••• • .. • • • • • • • .. .. • ... 24 6.3 Page Ammonium metaphosphate ••••••••••••••••••••• 55

Ammonium nitrate • • • • • . . • • • • • • • • • • • • • • • • 4 ,5

Ammonium phosphates • • • • • • • • • • • • • • • • • • • • • 57 Anniston, Alabama, site of first electric phosphorus furnace • • 2 , a8 catalyst ••••••••••••••••••••• 24 Applications of phosphoric acid •••••••••••••••• 33

Applications of phosphorus ••••••••••••••••••• 1 Arcing at precipitator-wire insulators • • • • • • • • • • • •• 17

Arc voltage • • • • • • • • • • • • • • • • • • • • • • • • • .12-13

ArseniO, as oatalyst ••••••••••• • • • • • • • • • • • 24

Arsine in phosphorus furnace gases •••• • • • • • • • • • • • 23

Atomized phosphorus • • • • • • •••••• • • • • • • • • • • • 47

Autoclave for oxidizing phosphorus •• • • • • • • • • • • •

Available phosphate ••••••••• • • • • • • • • • •

Average charge to phosphate reduction furnace • • • • • • • • • • 1.3 Average operating data tor phosphate reduction furnaoe ••• 12, 1.3

Barilko, N. A. (See Zagvozdk1n, I. I.)

Bario hydroxide, as catalyst • • • • • • • • • • • • • • • • • 24 Bars, mechanical, for cleaning rotary kilns •••••••••• 9 Batch mixers for superphosphate •••••••••••••• 35,.36

Belt, inclined oonveyor ••••••• • • • • • • • • • • • • • 35

Black phosphorus •••••••••• • • • • • • • • • • • • • 20

Blast furnaoe tor producing phosphorus • • • 2- .3, 43 , 44-45, 56-57 of phosphorus ••••• · . . . . . • • • • • • • 20 64 Page Bone, calcined, as catalyst ...... 49 Bone, calcined, as source of phosphorus . . · . . 2 Bones, production of phosphorus from, by Scheele ••• • • 2

Booy, I. J., mention of work by ••••••••••• • • 26 Boric acid, as catalyst · ...... 24 Br8Ildt, discoverer of phosphorus · ...... 2

Brass, for phosphorus pipe lines • • • • • • • • • • • • • 19

Breaking phosphorus emulsions • • • • • • • • • • . . • • 16 Britzke, mention of work by . . . • • • • • • • • · . . • • 1.2 Brunauer, S., mention of work by · ...... • • • • 51-52 Burdens for phosphate furnaces ...... 8-9, 10, 12-13 Burners for phosphorus · ...... 28-29, 32-33

Cage mill disintegrator · ...... 36, 38 Calcium carbide furnaces ...... · . . . . 6 Caloium carbonate, as eatalyst ••••• • • • • • • • • • 24 Calcium earbonate, as packing in absorption tower ••••• 39 Calcium chloride, as catalyst •••• • • • • • • • • • • • • • 24 Calcium cyanamide process for ammonia synthesis •••••••• 4 Caloium metaphosphate •• • • •• 31-32, 37-39, 41, 43-44, 51-54, 57 Calcium ...... · ... 10 Calcium sulfate in fertUizers, value of • • • • • • • · . . . 41 Capacity of electric furnaces for phosphorus production · . 3, 7-8 Carron •••••••••••••••••••••••• 2, 9, 1.2-43 Carbon disulfide •••••••••••••••••• • •• 27 65 Page

Carbon dioxide • • • • • • • • • • • • • • • • • • 21-2.3 , 42-44

Carbon mono~de •••••••••••• 9, 14-15, 21-2.3, 42-45, 56 Carry- over of dust from furnaces • • • • • • • • • • • • • •• 11

Catalogue of events in the histol7' of phosphorus ••••• 1, 2

Catalyjt for phosphorus oxidation • • • • • • • • • • • • • 47-49

Chain mechanism of phosphorus oxidation • • • • • • • • • • 27-28

Chain carriers in phosphorus oxidation • • • • • • • • • • • 27 Chain reactions ...... • • • 27-28 Charcoal, as catalyst •• • • • • • • • • • • • • • • • • • • 24

Chemical breaking of phosphorus emulsions • • • • • • • • • • 16 Chill cars ••••••••••••••• • • • • • • · . . . 6 C1earamce between electrodes in electric furnaces • • • • • • 7

Cloth bags for shipping fertilizers • ••• • • • • • • • • • 36

Cobalt, as eatalyst •• . . • • • • • • • • • • • • • • • • • 50 CQke ••••••••• ...... • •••• • • • .2, 6, 8-9, 13, 49 Coke-packing tor absorption towers • • • • · . • • • • •• .34,.38 Color or phosphorus •••••• • • • • • • • • • • • • • • • 20

Collection tank for phosphorus • • • • • • • • • • • • • • • • 18

Combustion rate of phosphorus ••• • • • • • • • • • • • • • 45 Combustion space for phosphorus • • • • • • · . . • • .27, .3.3, .37-.38 Composite lumps of charge for furnace burdens • • • • • • • • S

Compression of air, effect on phosphorus ignition • • • • • • 23

Concepts of phosphorus oxidation • • • • • • • • • • • • • • • 28 Concrete phosphorus storage tanks •••••••••••••• 19 66 Page Concentrated superphosphate ...... 31-32, 34-36, 40-41 Condenser tubes · ...... 17, 18 Condenser water • • • ...... 15 Contamination of seal oi l of precipitators · . . . . . 17 Control of pressure on electrie furnaces · ...... 11 Control of temperature in condensers · ...... 17 Conveyor (See belt conveyor) Cooling water · ...... 12, 17, 29, 37 Cooler, rotary for oaloium metaphospbate · · • · · • • • • 37 Copper, as catalyst • . . • . • • • • · • · • • · · • • · · 50 Copper phosphide, as catalyst · · • • · • • · • · · • • 49 Copper sUicide, as catalyst • · · • • • • · · • · • • • • • • · 50 Copper sulfate, for purifying preCipitator seal oll • • · • • • • 17 Corhart high- alumina refraotory material • • • · • • • • • • • • 38 Corrosion ...... • • .15-16, 18, 28-29, 3g-39 Crt tical pressure of oxygen in phosphorus oxidation •••• • •• 26 Cross, C. F., mention of work by · ...... 46 Cnoible, carbon-lined, for receiving slag and metal •••••• 13

Crude phosphorus • • • • • • • • • • • • • • • • • • • • • • • • 30

Current density in electric furnaces • • • • • • • • • • • • • • 11 Current flow between electrodes in electric furnaces . . . . 7 Curing superphosphate •••••••••••••••••••••• 36

CurtiS, H. A., ••••• • • • • • • • • • • • • • • • • • ••• 14, 44 67 Page

Datum temperature for heat balance • • • • • • • • • • • • • • • 52 Dehydrating agent in production of nitrocellulose •••••••• 33 Deposits of impurities in pipe lines handling phosphorus •••• 15

Design of calcium metaphosphate furnaces • • • • • • • • • • 37-39

Design of phosphorus furnaces ••• • • • • • • • • • • • • Y. 6-S Detroit rocking furnace for refining ferrophosphorus . . . . . 14 Deuterium, effect of retarding ohain carriers ••••••••• 27 Development of electric- furnace method for phosphorus ••• 1-2, 4, 14 Development of preferential oxidation of phosphorus • • • • 42-45, ;6 Development of process for xxidizing phosphorus with steam ••• 51-56

Developments in utilizing phosphates • • • • • • • • • • • • • ;6

Dewpoint of phosphorus •••••• • • • • • • • • • • • • 14, 17 Diamter of reaotion tube, effect on pbosphons oxidation •••• 26

Dioaloium phosphate •••••••••••••••••••••• JJ)

Difficulties in cleanSing fUrnaoe gases ••••••••••• 17, 18

Biffi.eulties in condensing phosphorus •••••••••••• 14.. 16 Difficulties in metering phosphorus • • • • • • • • • • • • •• 19

Diffusion ooeffioient of ohain reactions • • • • • • • • • • • 27

Dilution of gases • • • • • • • • • • • • • • • • • • • • • • • 45 DiSintegrator (See cage mill)

Dissociation of P4 to P2 • • • • • • • • • • • • • • • • • • • Displacement of explosive liaits in phosphorus oxidation • • •• 28

Dissipation of heat in phosphorus ignition •••••••••• 24

Distribution of fertilizers by TVA •••••••••••••• 41

Dorr thickeners for phosphorus sluge • • • • • • • • • • • • 15-16 68 Page

Dracco unloading system for rock phosphate • • • • • • • • • • .35

Dry condensation of phosphorue •••• • • • • • • • • • • • 16-19

Drying air •••••••••••• •• • • • • • • • • • • • • 45 Drying rock phosphate • • • . . . . . · ...... • • • • • .35 Ducts for conveying phosphorus-containing gases • • • • • • • • .34 Dumping superphosphate in piles for curing •• · . . • • · . . .36 Dust •••••••••••••••••• ••• • • • • • 11, 15-17

Dwight-Lloyd sintering machines • • • • • • • • • • • • • • • • 8 Dybkowsky, B. von, mention of work by • • • · . . • • • • • • • 46

Early investigators • • • • • • • • • • • • • • • • • • • • • .2.3, 46

Eoonomic data on oalcium metaphospbate produotion • • • • • • • 37

Economic faotors in methods of burning phosphorus • • • • • • • 29

Effeots of variables on phosphorus oxidation • • • • • • • • • 50 Electrocast refraotories (See Corhart) Electrio-furnace method of phosphorue produotion ••••• 1-5, 56 Electric furnace, reactions in •••••••••••••••• 10 Electrode consumption • • • • • • • • • • • • • • • • • • •• 11, 1.3

Electrodes • • • • • • • . . • • • • • • • • · ...... • • • 6-7, 12 Electrode current in eleotric furnaces • • • • • • • • • • • • • 13

Electrostatic preoipitators •••••• • • • • • • • • • • • • 34 Elevated temperatures and pressures for phosphorue oxidation •• 47-1J!> Elimination of impurities • • • • • • • • • • • • • • • • • •• 51

Emmett, P. H., mention of work by • • • • • • • • • • • • • • • 43

Endothermic reactions in phosphate reduction • • • • • • • • • 10 69

P~ge

Entrainment separators •••••• • • • • • • • • • • • • • • .16-18 E4uations for phosphorus oxidation • • •• · . . ••••••• .42, AS Equilibrium mixtures of gases •••••••••• • • • • •• 43- 45 Equipment corrosion (See corrosion)

Evaluation of phosphorus combustion processes • • • • • • • • 56-57

Excess air • • • • • • • • • • • • • • • • • • • • • 23, 29, 53

Eacess coke ••••••••••••••• • • • • • • • • • • • 13

Excessive cost of liquor system maintenance • • • • • • • • • • 18

Exhaust gases from furnaces • • • • • • • • • • • 18, 46, 52-53, 57 Exothermic reactions in phosphate reduction furnaces • • • • •• 10 Explosion chain carriers (See chain carriers) Explosive gas mixtures • • • • • • • • • • • • • • • • • • • •• 26 ExplOSion limits in phosphorus oxidation •••••••••••• 27 External heatin.g of phosphorus vaporizers • • • • • • • • • • •• 29

Extemal surfaces of condenser tubes, cooling of • • • • • 17-18

Farmers, use of experimental fertilizers by ,. . . . . ~ .. • • J.D Factors in maintenance of effecicient energy utilization • • • 10-11

Fans • • • • • • • • • • • • • • • • • • • • • • • • • • • 6, 15, 34

Feed chutes for electric furnaces • • • • • • • • • • 7

Feed hoppers •• • • • • • • • • • • • • • • • • • • • • • • • • Y7

Ferropbosphoras •••• • • • • • • • • • • • • • • • • • • 6-" 13

Ferrosi11con • • • • • • • • • • • • • • • • • • • • • • • ... 49 FertUizers • • • • • • • • • • • • • • • • • • • • • • ;6, 40, 51, 57

FUtering phosphorus .1Uge • • • • • • • • • • • • • • • • • • 16 Fines process for producing calicum metaphosphate • • • • • •• 38-39

Fishbeck, (., Mention of work by • • • • • • • • • • • • • • • 70 ;Page Flame temperature •••••••••••••••••••••• 24,42

Flexibility of dt condensation versus dry condensation •••• 18

Fluctuations in furnace operation ••• • • • • • • • • • • • • 18

Fluid oalcium metaphosphate, hendling of • • • • • • • • • • 37-38 Fluorapatite (See rock phosphate)

Fluorine • • • • • • • • • • ...... • • 15, 39

Fluorspar, as catalyst • • • • • • • • • • • • • • • • . . • • 24

Flushing dust from electrostatic precipitators • • • • • • • • 17

?o, formation in phosphorus condensef s •••• • • • • • • • • 18

Frear, G. L, mention of work by' • • • • • • • • • • • • • • • • 44

Free aeid in fertilizer compounds • • • • • • • • • • • • • • 36, 55 Freezing of phosphorus in condenser tubes ••••••••••• 18 Freitag, C. (See Ipat1ev, V. N.)

Frenoh patents, mention of ••• • • • • • • • • • • • • • • • 49-50

Frost, A. ,., mention of work by' • • • • • • • • • • • • • • 47, .48

!'unlaoe botto.s • • • • • • • • • • • • • • • • • • • • • • • • 6 Furnaoe gases • • • • • • • • • • • • • • • • • • • • • 6, 9, 14-15 Furnaoe pressure control •••••••••••••••• · . . . 11 Furnaoe shell temperature ••••••••••••••• • • • • 12 Furnace tops •••••• • • • • • • • • • • • • • • • • • ••• 6

Gas-oonfining zone ••••••••••••••••••••••• 30

Gases • • • • . . • • • • • • • • •• Q , 9 , 14-18, 21-22, 27, 45, 51

Gas mixtures • • • • • • • • • • • • 14, 27-28, 31, 34, 42-45, 52, 56

Gelatinous silioa • • • • • • It • • • • • • . . • • • • • • • • 15 German patents, mention of •••••• • • • • • • • • • • • •• 2 71 Page

Gmelin, L., mention of work by • • • • • • • • • • • • • • • • 46

Granulating slag ••••••• · , ...... • • • • • • 13 Grates f~r supporting rock phosphate in metaphosphate furnaces • 37

Green superphosphate • • • • • • • • • • • • • • • • • • • 35 Grab-bucket tractor cranes for moving superphosphate •• • • • 36

Grizzly • • . • • • • • • • • • • • • • • • • • • . • • • • • • 36

Ground rock phosphate • • • • • • • • • • • • • • • • • • • • • 35

Hardened phosphate on rotary kiln walls •••••••••••• 9 Heat balances in furnaces ...... 11-12, 52-5.3

Heat content of gases •• • • • • • • • • • • • • • 21-22, 45, 56

Heat exchange and exchangers • • • • • • • • • • • • • • • •• 30

Heat losses • • • • • • • • • • • • • • • • • • • • • ••• 11, 53 Heat of rusion ot phosphorus ••••••••••••••••• 20 Heat ot nbl.1mation of phosphorus pentoJdde •••••••••• 20

Beat of vaporization of phosphorus • • • • • • • • • • • • • • 20

Heat transfer in phosphorus condensation • • • • • • • • • • • 17 Heating burdens in electric furnaces ••••••••••••• 7 Heating phosphates during agglomeration •••••••••••• 15

Heating white phosphorus to produce red phosphorus · . . • • • 20 Helium .•••••••••••••••••••• • • • • · . . 27 High voltages in electric furnaces, advantages of . . . . • • • 11

Holley pneumatiC conveyor system • • • • • • • • • • • • • • • 35

Horizontal burner for phosphorus • • • • • • • • • • • • • • • 33 Horizontal vaporizer for phosphorus •••••••••••••• 33 Hull, L. H. (See Frear, G. L.) 72 Page Hydrator ••••••• • • • • • • • • • • • • • • • • • • •• .34

Hydrochloric acid • • • • • • • • • • • • • • • • • • • • • • .39

Hydrogen •••• • • • • • • • • • • • • • • . . . 21-2.3, 27, 46-54 •••• • • • • • • • • • • • • • • • • • • • 27

Ignition of phosphorus ••••••••••••••••••• 2.3-24 Illumination of gas mixtures, effect on oxidation • • • • • • • 27

Impurities in phosphorus •••••••••••••••••• 15, 20

Impurities in seal oil for electrostatic precipitators • • • • 17 Industrial value of phosphorus ...... • • • 1, 28 , .31-.3.3

Inert gases, .frect of on phosphorus oxidation • • • • • • • • 27

Infilco entrainment separator • • • • • • • • • • • • • • • • • • 16 Inlet temperature of phosphorus condenser • • • • • • • • • • • 17 Input of heat to furnaoes ••••••••••••••••• 12, 5.3

Installed capacity tor phosphorus production in the U. S. • • •• .3 Insufficient air, effect on phosphorus oxidation •••••••• 2.3

Insulators on electrostatic precipitators • • • • • • • • • • • 17 Ipatiev, V. N., mention of work by ••••••••••• • .46, 49-50

Iron blast fUrnace, heating value of gases from •••• • • • • 45

Iron salts, as catalyst • • • • • • • • • • • • • • • • • • • • • 50

Iron silicid., as catalyst ••••• • • • • • • • • • • • • • • 50

International Critical Tables •••• • • • • • • • • • • • • • • 21

Joints of electrodes • • • • • • • • • • • • • • • • • • • • • 11 73

Page

Kilns, rotary • • • • • • • • • • • • • • • • • • • • • • • • • 8-9

Kilowatt capaoity of furnaces • • • • • • • • • • • • • • • • 7-8 Kilowatt-hours required for phosphorus production · . . . 10- ll, 13 King, D. W., mention of work by •••••••• • • • • • • • 27 Klugh, B. G., mention of work by • • • • • • • • • • · . . . . 42 Kureodov, A. II., mention of work by • • • • • • • • • • • • • •

Lampblack, as catalyst • • • • • • • • • • • • • • • • • • • • 24

Leaks in condensers • • • • • • • • • • • • • • • • • • • • • • 18

Liljenroth, F. G., mention of work by • • • • • • • • • • • • • 51

Lime, as oatalyst •• • • • • • • • • • • • • • • • • • • • • • 24

Lime for caloium oarbide production • • • • • • • • • • • • • • 8

Limestone, oaloination of •• • • • • • • • • • • • • • • • • • 8 Limestone-filled tower for H01 absorption • • • • • • • • • • • 39

Linters, cotton, nitration of ••• • ••• • • • • • • • • • • 33

Liquid-confining zone in phosphorus oxidation • • • • • • • • • 30

Liquid phosphorus, handling of •••••• • • 14-19, .30, 33, 46-47

Load on exhaust pumps due to turnace putfing • • • • • • • • • 18

Lump phosphate •••••••••••••• • • • • • • • • • 8, 36

Magnesia, as catalyst ••••••••••••••• · . . . 24 Maintenance costs of phosphorus condensation systems • • • • 18-19

Manganese, as oa~st ••••••••••••• • • • • • • • 24 Manufaoturing Wilding for superphosphate •••• · . . • • • 35-36 Match tips • • • • ...... 1 74 Page

Mathematical formulas • • • • • • • • • • • • • • • 26-27, 35, 47 Material balances •• •••••••••••• 7, 12-13, 41, 53-54 l4uimum yield of phosphoric acid by phosphorus oxidation ••• 4S Mechanisms of phosphorus oxidation •••••••• 24-28, 47-49, 50

Mellor, J. W., mention of book by • • • • • • • • • • • • • 20, 46

Melville, H. W., mention ot work by • • • • • • • • • • • • • 27

Mercury arc ••••• • • • • • • • • • • • • • • • • • • • • 27

Metallic ~er tips • • • • • • • • • • • • • • • • • • • • 28 Metallic salts • • • • · ...... • • • • 49-50 lIetaphosphates • • • • • • • • • • • • Jl, 35, 37-1JJ, 44, 51-55, 57

Metaphosphoric acid • • • • • ...... • • • 38, 45, 55

1Iete-rhir'-php ~r.u. - • • • • • • • • • • • • • • • • • • • • • 19

Methane • • • • • • • • • • • • • • • • • • • • • • • • • •• 27

MUitary uses for phosphorus •••• • • • • • • • • • 3-5, 1.0, 56 Miller, A. II. (See Curtis, H. A.)

Mist from sprays ••••••••• • • • • • • • • • • • • • 34

Mixers tor superphosphate • • • • • • • • • • • • • .... 35-36

Mixing nozzle tor phosphorus and water ••••••••• • • 47 liner, C. G., mention ot work b,y •••••••••••• · . 49 Mining rock phosphate •••••••••••••••••• • • Molds for terrosphosphorus , , • • • • • • • • • • • • • • •

Molecules, reactions between . . . ••• • • • • • • • • • • Monsanto Chemical Oompany ...... • • Munitions (See military uses for phosphorus) Muscle Shoals, Alabama • • • • • • • • • • • • • • • • • • • • 4 75 Page

Nash-Hytor exhaust pump • • • • • • • • • • • • • • • • • • 16, 18

Natural lump phosphate ••• 0 • 0 • • • • • • • • 0 • • • • • 37

Neutralization of free acid •••• • • • • • • • • 0 • • • • 55 Newton, R. H. (See Curtis, H. A.)

Niokel and niokel salts, as oatal7sta • 0 • • • • • • • • • ,4a-50

Nodules ••••••••• •••••••••••••••• 8, 9, 13

Nodulizing phosphate fines ••• 0 • • • • • • • • • • 0 • 8, 9

Nikolaieff, V. (See Ipatierf, V. Bo)

Nitration of cotton liRters • • • • • • • • • • • • • • • • • • 33

Nitrocellulose • • • • • • • • • • • • • • • • • • • • • • • • 33

Nitrogen •• 0 • 0 • 0 •• 0 0 ••• 0 • 0 0 • 0 • • 33, 45, 52- 55 Nozzle (See mixing nozzle)

Oil, purification of precipitator • • • • • • • • • • • • • • 17

Oil-seal system for electrostatic precipitator • • • • • • • • 17

Operating conditions for eleotric furnaces • 0 • • •••• 12, 13 Ortbophosphoric acid (See phosphoric acid)

OrdinarT superphosphate • • • • • • • • • • • • • • • • • • • 34

Original plant at Iluso1e Shoals. Alabama • • • • • • • • • • • 4

Output of heat from furnaees • • • • • 0 • • • • • • • • • • 12, 53

Overall e1eotric-fUrnace reaotion . . • • • • • • • • • • • • • 10

Oxidation of phosphorus • • 0 o • 21, 24~2~, 26-32, 33, 42-45. 47-57

Oxygen • • • • • • • • • • • • • • • • 0 22-23, 24-26, 42-43, 53-54

Ozone • • • • 0 • • • • • • • • • • • • • • • • • • • • • • • • 25

Paoking of absorption towers · . . · . . • • o • • • • • • • 38- 39 Phosphate fertilizers 0... • • • • • · . . . . 4, 31, ltJ-41 76 Page Phosphate sands ••• ...... • 8-9, 13 Phosphides ••••• ...... • • 49 Phosphine • • ...... • • • • •• 23, 27, 46, 48-50~ 52 Phosphoric acid ...... 1, 14, 31-36, 38-39, 48-50, 54-55 Phosphorus furnaces ••••••••• ...... 2, 4-14, 23 Phosphorus fluorides and oxyfluorides ...... 23 Phosphorus burners • • • • • ...... 28-30, 33, 37 Phosphorus-tn-water emulsions · ...... • • • •• 16 Phosphorus losses ...... 15 Phosphorus oxides • 1, 10-13, 20-28, 32-34, 36, 39, 42-45, 50, 54, 56 Phosphorus, properties ot •••••• • • • • • • • • •• 20 Phosphorus suboxides ••••••••••••••••••• 23, 25 Phosphorus production • • • • • • • • • • • • • • • • • • • •• 1-14

Phosphorus, uses ot • • • • • • • • • • • • • • • • • • • • 1-3, 5

Pilot plants •• • • • • • • . . • • • ...... 5, 19, 29, 44 Pipe lines •••••• • • . . . . • • • . . • • • • • • • · . 15 Plugging of condensors and pipe lines handling phosphorus •• 15-19 Pneumatic conveyors •••••••••••••••••••••• 35 Poisons ••. • • • • • . • • • • • • • ••••••.•••• 1, 51 Potassium chloride ••••••••••••••••••••• 32, 39

Potassium fluosilioate • • • • • • • • • • • • • • • • • • • 15, 16 Potassium hydroxide, as catalyst · ...... • • • • • 24 Potassium metaphosphate •••••••••••••• 31-32, 39-41, 56 Powdered coal. as fuel for phosphates noduli zing · . . . . 9 PreCipitators •••••••••••••••••••••• 17-18, 34 77 Page

Preferential oxidation of phosphorus • • • • • • • • • 28, 42-45

Primary producers of phosphorus • • • • • • • • • • • • • • •• 3

Puffing of furnaces •••• • • • • • • • • • • • • • • • 18

Pumps ••••••••• • • • • • • • • • • • • • • • • • 16, 18-19

Purifioation of phosphorus . . • • • • • . . . • • • • • 14, 16, 19 Jyro'tatohnios, use of phosphorus in • • • • • • • • • • • • • • 1

Radiation and conveotion losses from furnaoes •• • • • • •• 12, 53 Railway cars for hauling rook phosphate •• • • • • • • • • • •• 35 Rarification of air, effect on phosphorus oxidation ••••••• 23

Ratio of aoid to rook phosphate in superphosphate mixing • • • •• .35

Ratio of pater to phosphorus in phosphorus oxidation •••••• 48

Raymond mille • • • • • • • • • • • • • • • • • • • • • • • • • .35 Reaotions in electrio fUrnaoes •• • • • • • • • • • • • • • •• 10 Reactions of phosphorus with water • • • • • • • • • • •. •• 46-50 Reaction rate for pbosphorus oxidation • • • • • • • • • • • • • 24 Reaction tower of calcium metaphosphate unit • • • • • • • • •• 38

Read Maohinery Company superphosphate mixers • • • • • • • • • • .35 Readman, mention of patents b,y ••••••••••••••••• 2 Reoondi tioning and relining of phosphate reduotion furnaces ••• 8 Red phosphorus ••••••••••••••••••• 20, 2.3, 47-48 Reduotion of phospbat&s (See phosphorus production)

Refraotory-lined vaporizer • • • • • • • • • • • • • • • • • • • .3.3 Refractori.s for metaphosphate furnaoe grates · ...... 37 Requirements tor phosphorus oxidation in air • • • • • • • • • • 28 78 Page

Research Corporation ...... • • • • • • • • • • • • • • • • 17 Rock phosphate •• • • • • • 1-2, 8-10, 13, 34-39, 43-44, 51, 53 Rotary coolers (See coolers, rotary)

Russian experiments on phosphorus oxidation • • • • • • • • • • • 25

Safety of electric fUrnace operators • • • • • • • • • • • • • • 11

Scheele, mention of work by • • • • • • • • • • • • • • • • • • 2

Semenov, N., mention of work by ••• • • • • • • • • • • • • • 26 Separators (See entrainment separators) Shaft furnaces (See blast furnaces)

Shape of eleotric fUrnaces ••••••••••••••••• • • 7 Shu!tz, J. r., mention of work by ••••••••••••• 43, 52

Significant events in the history of phosphorus •••••• • • 2

Silica • • • • • • • • • • • • • • • • • • • • • • 8, 10, 13, 15, 24

Siliceous flux •• • • • • • • • • • • • • • • • • • • • • • •• 1.2.

Silicon carbide as catalyst support • • • • • • • • • • • • • • 49

Silos for rock phosphate storage • • • • • • • • • • • • • • • • 35

Silver, as oatalyst •• • • • • • • • • • • • • • • • • • • • • 50

Sintering rock phosphate • • • • • • • • • • • • • • • • • • • 8, 9 Sizes of electric furnaces •••••••••••••••••• 7, 8 Skip hoist for conveying charge to caloium metaphosphate fUrnace 37 Slag • • • • • • • • • • • • • • • • • • • • • • •• 6, 9-10, 12-13 Slag handling ••••••••••••••••••••••••• 13

Sludge, phosphorus ••••••••• • • • • • • • • • • • • • 15-16

Sodium chloride, as catalyst • • • • • • • • • • • • • • • • •• 24 79 Page

SodiUlll hydroxide in oxidation of phosphorus • • • • • • • 47, 49-50

Sodium nitrate, as catalyst • • • • • • • • • • • • • • • • • 24

SodiUlll phosphates • • • • • • • • • • • • • • • • • • • • • • • 49-50 Sprays, water •••••••••••••••••••• 15, 34, 37-,38

Statistics on phosphorus production • • • • • • • • • • • • • • 3

S~atistios on fertilizer produotion and distribution b.r TVA • •

Steam • • • • • • • • • • • • • • • • • • • • 16-17, 19, 21, 51-55

Steam oxidation of phosphorus • • • • • • • • • • • e "· • • • 22, 51-55

Storage tanks for phosphorus • • • • • • • • • • • • • • • • 15, 18

Stoves, blast-tumace • • • • • • • • • • • • • • • • • • 44

Sublimation temperature of phosphorus pentoxide • • • • • • • • 20

Submerged pumps for phosphorus • • • • • • • • • • • • • • • • 19

Superheated steam for phosphorus oxidation • • • • • • • • • • 54 Suspension of eleotrodes in electric furnaces ...... 6

Swann Chemioal Company • • • • • • • • • • • • • • • • • • • • 2

Synthesis of ammonia • • • • • • • • • • • • • • • • • 51-52, 55

Tanks for phosphorus storage • • • • • • • • • • • • • • • • 18, 19

Tanks for pbQsphorio aoid storage • • • • • • • • • • • • • • • 34

Tank oars and wagons for phosphorus transportation • • • • • • 19

Tap holes of eleotrio furnaces • • • • • • • • • • • • • • • 6, 7

Tapping furnaces • • • • • • • • • • • • • ...... 7, /I)

Tennessee phosphate fields • • • • • • • • • • • • • • • • • • 2

Tennessee Valley Authority • • • 2-9, 14, 31, 34, 37, /1)-41, 44-45

Temperature oontrol in phosphorus oondensers • • • • • • • 15, 17

Temperature control in phosphorus vaptrizers • • • • • • 29-30, 33 So Page Temperature of gases from electric furnaces • • • • • • • • • • 17 Temperature required for oxidation of • • • 50

Tests of phosphorus collection systeas • • • • • • • • • • • • 14 Tests of TVA experimental fertilizers ...... 40 Thermal properties of phosphorus and phosphorus pentox1de • • 20-22 Thickeners (See Dorr thickeners) Tower of metaphosphate furnaces ...... 37-3S Transformer voltages for eleotric furnaces •••••••••• 1.3 Trestle for unloading rook phosphate ••••••••••••• 35 Trolley ears tor carrying superphosphate to storage ••••• 36

U1 travio1et light, effeot ot on phosphorus oxidation ••• •• 27

Unaccounted for losses in heat balanoes • • • • • • • • •• 12, 53

Useful heat in phosphorus oxidation • • • • • . . . • • • • • 42

Vaporizers, phosphorus • • • • • • • • • • • • • • • 28-.30, 33, '3

Victor Chemical Company • • • • • • • • • • • • • • • • • • • • 2

Violet phosphorus • • • • • • • • • • • • • • • • • • • • • • 20

Washing phosphate sands • • • • • • • • • • • • • • • • • • • S

Water oxidation of phosphorus • • • • • • • • • • • • • • • 46-50 Wet oondensation of phosphorus ••••••••••••••• 14-17

Whi te phosphorus ••••••••••• • • • • • • • • • • • 20 Wilson Dam plant of the TVA •••••••••••••• 7, 14, 33

Wohler, mention of work b,y •• • • • • • • • • • • • • • • •• 2 81

Page

World War I • • • • • • • • • • • • • • • • • • • • • • • • • 4

Yellow phosphorus • • • • • • • • • • • • • • • • • • • • • • 20

Zagvozdk1n, I. I., mention of work by • • • • • • • • • • • 24-25 Zino spark • • • • • • • • • • • • • • • • • • • • • • • • •• 2:7 ERWIN c. HOmAN - Chemical !ngineer u. a, Bureau g! Mipe!!. Rolla, Missouri. Aesociate Chemical Engineer since December, 1942. In oharge of Hydrometallurgical Unit and alumina production investigations.

tJ r Bt IennesS!e Vallez Aijthoritl, WUson Dam, Alabama.

Assistant Chemical &gineer from July, 1940 to December, 1942.

Member of the staff of the Research and Development Coordination Unit,

engaged in the preparation of work programs, reports, and technical

eorrespondence. Junior Chemical Engineer from July, 1937 to July,

'1940, engaged 1nF8Upervi,S1ng pilot-plant operations in the develop­ ment of prooesses for produoing oaloium aetapbosphate, phosphorio acici, and other mat.rials. CheJdoal !algin•• ring Aide from September,

1936, to July, -1937.

W.st Kentuclq M'n.ral Company, Murray, tentucky.

Chemical Engineer froll August, 1935, to September, 1936. In

charge of research on the development of bleaching clays. Western Ya!. Works, Stet Gen.vieve, Missouri.

Chemical Engineer trom February, 1933, to September, 1934. In charge of research on the development of processes tor the produc­

tion of calcium formate and formic acid.

Phillip! Petroley! CoePa.nl. Kansas City, IanS8.B.

Research assistant from April, 1931, to January, 1933, engaged in testing and research on petroleum and petroleum products. ~ Refining Compf¥l:L. Port Arthur, Texas.

A.ssistant Chemioal Engineer from July, 1930, to March, 19.31, engaged in petroleum refining research investigations.

Missouri Sohool of lIiBls !D.4. lIetallurgy, Rolla, Missouri.

II. S. in Chemical Engineering, 1935.

B. S. in Chemical ihgineering, 1930.

Assistant Chemist, 19.34-.35. II. E. R. A. Fellowship with the

Missouri Geological Survey.