4P42 Section: 1 .I Reference: 2 Title: Steam: It Generation And Use, 38th Edition, Babcock and Wilcox, New York, B ITUMINOU COAL COMBUSTION AP-42 Section Reference Number 1
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j9th edition of "Steam," a book by :k,& Wilcox Company that details Copyright 0 1975 by The Babcock & \Vilcos Company wces in the production of steam Revised thiry-eighth edition iization of fuels. First printing :2nt change in this new edition is ?d coverage of nuclear steam gen- ipment in recognition of the grow- :rice of nuclear fuels as a source 3r the production of steam. [ion also reflects the augmented m quality control, which has ef- mtant improvements in product ing the last twenty years concur- large increases in the capacity of steam generating units. i .issue of "Steam" appeared in long after a New Jersey engineer ohen Wilcox applied his knowledge .culation theory to perfecting a new cept. In 1867, Wilcox formed a 2 with George H. Babcock and the Qcock&Wilcox Company succeeded ttle more than a century since the' I was formed, B,&W has grown from id one product into an organization ian 36,000 men and women em- lacilities throughout the world. Its ring activities range from nuclear o specialty steels and refractories ed machinery. npanY gratefully acknowledges the ooperation and loyalty of its patrons syees. which have made possible ~~,bc~~l:& ~vilcox~orrtporiy. AII rights rcscrccd a Igj5>j960, 1963, lgj2, by UtiOnS in the field of steam genera- ?'hisbook, m,y ,,ads tjLcrcof,moy riot be reproduced ita atry for,jr toilhod SreSSeS the hope that this volume Gritten permission of the publi.sIm t@x tlmulate further advances in Stea rn/its generation and use
Babcock&Wilcox 161 East42ndStreet NewY0rk.N.Y. 10017 Copyright 0 1975 by The Bahcock & Wilcax Company Revised thirty-eighth edition Fint printing
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Librory of Congress Catalog Cord Number: 75-7696 Printed in the United Stores of Americo 22 Sampling of coal
290 21 Although thc coal consumption in a ccntral station may be incasured in thousands of tons per day, the samples 20 nscd for laboratory ;in;ilysis are incnsurcd in grams. It = c is tliercfore important and difficult to obtain representa- 2 280 19 .E c ” tivc sainplcs of coal. IhW playcd a prominent part in P .-- 18 resolvirlg this dilliculty, and thc first ASTM Standard for G !? Sampling Coal. (I1 21) was based 1;rrgely on the work of 270 17 9 3? B&W pcrsonncl. : II ASTM Standard 11492 now in usc was developed, a 16 adoptcd in 1948, and rcapprovcd in 1958. In this stand- 260 15 ard, which is less laborious than thc original, allowances arc made for the probable ash content of the coal, per- 14 mitting the use of smallci gross samplcs for the coals of lower ash content. 250 - 13 19M1 ‘61 ‘62 ‘63 ‘64 ‘65 ‘66 ‘67 ‘68 ‘69 ‘70 Two sampling procediires are recognized in thc pres- Year ent standard. 1. Commercial-Sampling Procedure. Fig. 4 Recoverable reserves and the reseNesproduction ratio of natural gas in the United States. (Source. Bureau of Mines.) 2. Special-Purpose Sampling Procedurc. The “Commercial-Sampling Procedure” applies to the average commercial sampling of coal. This procedure is Table 13 Recoverable natural gas reserves and production designed to measure the average ash content of a large in the ten leading states of the US. number of samples within -t 10% to a 95% probability. (Trillion cu ft) The “Special-Purpose-Sampling Procedure” applies to Reserves Production the sampling of coal when special accuracy is required. Jan. 1, 1970 1969 This rocedure should be used to supply samples for the
~~~ Texas 112.4 4.6 classigcation of coals and the establishment of design or performance parameters. The special-purpose sample Louisiana 85.1~~ ~ 7.28 Oklahoma 17.6 1.68 can be one of two sizes, either 4 times that of the com- New Mexico 14.3 1.09 mercial sample, giving an accuracy of e 5% of the ash Kansas 14.1 0.89 content of the coal samples, or 9 times that of the com- California 8.9 0.84 mercial sample, giving an accuracy of * 3.33% of the ash Alaska 5.2 - content of the coal sampled. Wyoming 3.9 0.32 Standard D 492 also sets procedures for reducing gross Arkansas 2.6 0.17 samples and for obtaining samples for standard and spe- West Virginia 2.4 0.21 Mississippi - 0.17 cial moisture determinations. Two additional pertinent - - publications by the ASTM are: Symposium on Bulk Total 264.5 20.11 Sampling (STP242, 1958) and Symposium on Coal Total in the US. 275.1 20.12 - Samplinz (STP 162, 1955). A new method has also been Source, Ameriqn Gas Association, Inc. adopted-in 1968 covering the mechanical sampling of coal.~..~ .-n22’4. ~~-~ Careful coal sampling is of prime importance since any in circumstances which prevented the free access of air. data resulting from subsequent analyses are only as At intervals, wind and water covered this mass with sedi- representative as the sample provided. ment, sand and dirt to form the overburden now found above coal seams. During millions of years, these layers Coal analysis of vegetation were subjected to moisture, heat and pres- Customary practice in reporting the components of a sure, and portions of the cellulose and other organic ma- mal is to use two different analyses, known as “proxi- terials were converted to carbon and hydrocarbons. In mate” and “ultimate.” The proximate analysis is defined this manner wood and vegetation were changed, perhaps as the determination of moisture, volatile matter, and ash, progressively, to peat, brown coals and lignite, subbitu- and the calculation of fixed carbon by difference. The minous and bituminous coals, and finally to anthracite. ultimate analysis from a dried samplc is defined as the The intrinsic ash of coal was largely in the vegetation determination of carbon, hydrogen, sulfur, nitrogen and from the beginning. The extraneous ash came from mud ash, and the estimation of oxygen by difference. The deposits of shale and pyrites that filled the cracks and scope of each is indicated in the following analyses of a crevices caused by thc movemcnt of the earth‘s crust. West Virginia coal, in which the ultimate analysis has Most of the coal mined in the US. corncs from.scams been converted to the as-received basis. 3 to 6 ft thick, with the average about 5.5 ft. One seam The nnalysis on thc as-received basis includes the total ncar Lakc De Sniet, Johnson County, Wyoming, aver- moisture content of coal received at the plant. Similarly, ages more than 100 feet in thickness and acquircs a maxi- the as-fired basis includcs the total moisture content of mum thickness of 220 ft. The thickcst known scam in the the coal as it enters thc Iioilcr furnace or pulverizers. The world, 425 ft, is in Manchuria. various values from such analyses are needed to imple- Steam / Sources of chemical energy 5-9
Coal analyses ing and h;indling equipment and. in the &sign and On asreceived basis (Pittsburgh Seam Coal. West Virginia) arr;ingcment of hcat trnnsfcr surfaces. Mcthods and principlcs of burning arc closely :issociated with specific Proximate Analysis Ultimate Analysis types of equipment, and rcfcrencc should be madc to Component Weight,% Component Weight,% Chapters 9, 10 and 11. Thc nature and effccls of impuri- ties in coal arc discusscd in Cliaptcr 15. Moisture 2.5 Moisture 2.5 One classification of coal is by rank, ix., according to Volatile matter 37.6 Carhon 75.0 the degree of mct;imorphism, or progrcssivc nltcration, Fixed carbon 52.9 Hydrogen 5.0 in the natural scrics from lignite to anthracitc. Volatile Ash -7.0 Sulfur 2.3 matter, fixed carbon, inhcrcnt or bed moisturc (equi- Total 100.0 Nitrogen 1.5 lil)r:itcd moisturc at 30C and 97% humidity), and oxy- Oxygen 6.7 gcn arc all indicative of rank, but no one item completely Heating value, Ash -7.0 dcfilies it. In thc ASTM classification, thc basic criteria Bhi/lb 13,000 Total 100.0 iirc the fixcd carbon and the calorific values calculated on a mineral-matter-free basis. It is necessary, in establishing the rank of mals, to use ment the formulas in this chapter and in Chapter 6. information showing an appreciable and systcmatic vari- Standard laboratory procedures for making these analy- ation with age. For the older coals, a good criterion is ses appear in ASTM D 271. A list of other testing stand- thc “dry, mincral-matter-free fixed carbon or volatile.” ards is given in Table 14. However, this valuc is not suitable for designating the rank of the younger coals. A dependable means of classi- ASTM classification by rank fying the latter is the “moist, mineral-matter-frcc Btu,” Coals are classified in order to identify end usc and also which varies little for the older coals but appreciably to provide data useful in specifying and selecting burn- and systematically for younger coals.
Table 14 ASTM standards for testing coal, specifications and definitions of terms
ASTM Standards for Testing Coal ‘D 1756 Carhon Dioxide in Coal OD 2234 Sampling, Mechanical, of Coal ‘D 2361 Chlorine in Coal OD 2013 Samples, Coal, Preparing of Analysis ‘D 291 Cubic Foot Weight of Crushed Bituminous Coal *D 410 Screen, Analysis of Coal ‘D 440 Drop Shatter Test for Coal D 311 Sieve Analysis of Crushed Bituminous Coal OD 547 Dustiness, Index of,of Coal and Coke D 310 Size of Anthracite ‘D 1857 Fusibility of Coal Ash ‘D 431 Size of Coal, Designating from ‘D 1412 Equilihlium Moisture of Coal at 96 to its Screen Analysis 97% Relative Humidity and 30C *D 1757 Sulfur in Coal Ash ‘I32014 Expansion or Contraction of Coal by the ‘D 2492 Sulfur, Forms of, in Coal Sole-Heated Oven ‘D 441 Tumbler Test for Coal TI 720 pee-Swelling Index of Coal D 409 Grindability of Coal by the Hardgrove- SDecifications Machine Method ‘D 2015 Gross Calorific Vnlue of Solid Fuel by the ‘D 388 Classification of Coals by Rank Adiabatic Bomb Calorimeter ‘E 11 Wire-Cloth Sieves for Testing Purposes D 1812 Plastic Pro erties of Coal by the E 323 Perforated-Plate Sieves for Testing Purposes Cieseler P Pastometer D 2639 Plastic Properties of Coal by the Automatic Gieseler Plastometer Definitions of Terms D 197 Sampling and Fineness Test of Powdered Coal OD 121 Coal and Coke ‘D 271 Sampling and Analysis, Laboratory, D 2796 Lithological Classes and of Coal and Coke Physical Components of Coal D 492 Sampling Coals Classified According to ‘D 407 Gross Calorific Value and Net Calorific Ash Content Value of Solid and Liquid Fuels
~ e Approved as American National Standard by the American National Standards Inititutc. 5-10
Tahlc 15, ASTM D 388, is uscd for cliissificntion ~ic- cording to rank or ~ifie.Oldcr coals arc classificd hy dry, inincral-m;ittc.r-frec fixcd carbon, and yoiingcr coals by Anthracite moist, inincr;il-tiintti~r-frccDtu. Thcsc tcrms an: dcfincd by thc Parr formulas (2) and (3). 17onnul;is (4), 90 (l), Semi Anthracite (5) ;id (6) arc approxiinate forms of the Parr formu- las. I’roxiiiiatc nnnlyses and higher licnting v;!lucs are used in making thc cnlculntions. Parr formulas Dry, Mm-frec FC = FC - 0.15 S 100 - (M + 1.08’4 + 0.55 S) x 100, %
Dry, Mm-free VM = 100 - Dry, film-free FC, %
Moist, Mm-free Btu = Btu - 50 S X 100, per Ib 100 - (1.08.4 + 0.55 S)
Approximation formulas Dry, Mm-free FC = FC 40 High-Vol 100, % +#&j++j+i loo - (Af + 1.1.4 + 0.1 S) x CBitum Bitum Bitum Dry, Mm-free VM = 30 6 8 10 12 14 16 100 Dry, Mm-free - FC, % Moist. Mineral.Matter.Free. loo0 Et”
Moist, Mm-free Btu = Fig. 5 Distribution plot for over 300 coals of the United States, Btu illustrating ASTM classification by rank as defined in Table 15. X 100, per Ib 100 - (1.1’4 + 0.1 S) where: Other classifications of coal by rank Mm = mineral matter There are classifications of coal by rank (or typc) which Btu = heating value per Ih are currently in limited use on thc European Continent. FC = fixed carbon, yo These are the International Classification of Hard Coals VM = volatile matter, % by Type, and the International Classification of Brown fif = bed moisture, yo Coals. The systems weqe developed by a Classification A = ash, % Working Party established in 1949 by the Coal Coni- S = sulfur, yo mittee of the Economic Commission for Europe. All for coal on a moist basis. The classification system of hard coals, which also in- cludes a simplified statistical grouping combining coals The term “moist” refers to bed moisture only, and having the same general characteristics, appears in Table analyses of constituents must be of bed samples collected 17. Thc term “hard coal” is bascd on European tcrmi- as prescribed by ASTM D 388. Agglomerating and nology and is defined as coal with a calorific value of weathering (or slacking) indices are used to differentiate more than 10,260 Btu/lb on the moist, ash-frce basis. between certain adjacent groups and are defined in this The term “type” is equivalcnt to rank in American coal standard. classification terminology and the term “class” npproxi- Tablc 16 lists 17 selccted UScoals, arranged in the mates thc ASTM rank. 1“ order of the ASTM classification. The basis for the two The nine classes of coal, based on dry, ash-free vola- I, ASTM criteria (the fixed carbon and the calorific values tile matter content and moist, ash-free calorific value, are calculated on a moist, mineral-matter-free basis) are divided into groups according to their caking properties. shown in Fig. 5 for over 300 typical coals of the U.S. The Either the free-swelling test or the Roga test may be classcs and groups of Tablc 15 are indicated in Fig. 5. used to determine caking properties (a mcasurc of the For the anthracitic and low- and medium- volatile bi- behavior of coal whcn heated rapidly). tuminous coals, the moist, mineral-matter-free calorific Thc coal groups arc further subdivided into subgroups valuc changes very.littlc; hcnce the fixed-carbon criterion according to their coking propcrtics, which arc n nicas- is used. Conversely, in the case of the high-volatile ure of the behavior of thc coal when heatcd slowly. bituminous, subbituminous and lignitic coals, thc moist, Either the Audibert-Arnu tcst or the Gray-King coking Inincral-matter-frce calorific valuc is used, sincc the tcst may hc used to detcrminc thcse coking propcrties. fscd carbon is almost the same for all classifications. A thrcc-figure code uumbcr is used to cxprcss cod Steam /Sources of chemical energy 5-11
Table 15 Classification of coals by rank' (ASTM D 388) Fixed Carbon Volatile Matter Calorific Vahie Limits, % Limits, % Limits, Btu/lb (Dry, Mineral- (Dry, hlizwra- (h1aist.b Matter-Frec Mattcr-Free Mineral-Mattcr- Agglomerating Class Cl<,,,p Basis) Basis) Free Basis) Character Equd or Equnl Equal or Greater Less Grcnter or Lcas Greater Less man TI,^,, TIK,~ mn Than Than 1. Meta-anthracite 98 - - 2 - 1. Anthracitic 2. Anthracite 92 98 2 8 - 1 }\lmagglomerating 3. Semianthrscitec 86 92 8 14 - - 1. Low volatilc bituminous coal 78 86 14 22 - 2. Medium volatile bituminous coal 69 78 22 31 - 11. Bituminous 3. High volatile A bituminous coal - 69 31 - 14,000d - 4. High volatile B bituminous mal - - - 13,000d 14,000 ag!$omcratingo 5. High volatile C bituminous coal - - - 11,500 13,000 10.500Q 11.500 lconlmonlyAgglomerating 1. Subbituminous A coal - - - - 10,500 11,500 111. Subbituminous 2. Subbituminous B coal - - - - 9,500 10,500 3. Subbituminous C cod - - - - IV. Lignitic 1. Lignite A - - - - 6,300 8,300 2. Lignite B - - - - 6,300 *This classification does not include a few coals. principal1 "on- Table 16 Seventeen selected U.S. coals arranged in order of ASTM classification Coal Rank Coal Analvsis. Bed Moisture Basis Rank Rank No. Class Group State County M VM FC. A S Btu FC Btu 1 I 1 Pa. Schuylkill 4.5 1.7 84.1 9.7 0.77 12,745 99.2 14,280 2 I 2 Pa. Lackawanna 2.5 6.2 79.4 11.9 0.60 12,925 94.1 14,880 3 I 3 Va. Montgomery 2.0 10.6 67.2 20.2 0.62 11,925 88.7 15,340 4 I1 1 W.Va. hlcDowell 1.0 16.6 77.3 5.1 0.74 14,715 82.8 15,600 5 I1 1 Pa. Cambria 1.3 17.5 70.9 10.3 1.68 13,800 81.3 15,595 6 I1 2 Pa. Somenet 1.5 20.8 67.5 10.2 1.68 13,720 77.5 15,485 7 I1 2 Pa. Indiana 1.5 23.4 64.9 10.2 2.20 13,800 74.5 15,580 8 11 3 Pa. Westmoreland 1.5 30.7 56.6 11.2 1.82 13,325 65.8 15,230 9 I1 3 KY. Pike 2.5 36.7 57.5 3.3 0.70 14,480 61.3 15,040 10 I1 3 Ohio Belmont 3.6 40.0 47.3 9.1 4.00 12,850 55.4 14,380 11 11 4 111. Williamson 5.8 36.2 46.3 11.7 2.70 11,910 57.3 13,710 12 I1 4 Utah Emery 5.2 38.2 50.2 6.4 0.90 12,600 57.3 13,560 13 11 5 111. Vermilion 12.2 38.8 40.0 9.0 3.20 11,340 51.8 12,630 14 I11 1 Mont. Musselshell i4.i 32.2 46.7 7.0 0.43 11,140 59.0 12,075 15 111 2 WYO. Sheridan 25.0 30.5 40.8 3.7 0.30 9,345 57.5 9,745 16 III 3 wyo. Campbell 31.0 31.4 32.8 4.8 0.55 8,320 51.5 8,790 -17 IV 1 N.D. 37.0 26.6 32.2 4.2 0.40 7,255 55.2 7,610 Notes: For definition of Rank Classification according to ASTM requirements, scc Toblc 15. Data on Coal (Bed Moisture Basis) M =equilibrium moisture, %; VM =volatile matter, %; Rank FC = dry, mincral-matter-free fixed carbon, % FC =fixed carbon, %; A = ash, %; S =sulfur, %; Hank Btu =moist, mineral-matter-free Btu per Ih. Btu = Btu per Ib, high heating value. Calculations by Parr formulas. 5.12 -_ I- M .-c n a m e m -M A 3 .-2 m A .-L a! m m 5 A U c m a! m m +% A A hX - -I -n 2. 20 m nm 1 I mo 2 co -A z m m I c N2 .c A 0 - - 0 I dz A I -m c .-0 Y m I E 0) .Yc - I -a m m IB 0 * 4 A N 2 A A 7 . Steam / Sources of chemical energy t A NW m* A I 5-14 cl..issific;ition. .: Thc first figure indicates the class of thc is not shown, since it is of littlc importnncc. It is said that coal, thc sccoiid figurc the group, nnd the third figiirc this Pcrch and Husscll ratio is closely rclatcd to the cok- thc subgroup. For cxamplc, a 635 coal would bc a class ing properties of coals used in coke-oven practice. 6 coal with a free-swclling index grcnter than 4 2nd es- It may be of interest to consider the validity of other pansion (dilatation) greater than 140. criteria in the classification of coal by rank based on the The rank classification is about the same as ASTM dry, ash-free analyses appearing in Table 21. Carbon (C) classification except for dctcrminntion of calorific-value comes close to lining up the coals in the samc order as correction. The Intcrnntional system uses the ash-frce the ASTM rank. As a criterion, the carbon content would basis, whereas the ASTM system uses the mineral- be quite simple, but it cannot be used as a suitable basis matter-frcc basis. Amcrican coals fit in the International for classification. Oxygen (0,) generally decreases with classification as shown by the open faced blocks in Table the age of coals, but it is not consistent. The volatile mat- 18. A gcneral comparison of the systems with several tcr (VM),fixed carbon (FC), hydrogen (H,), and the American coals is shown in Table 19. Btu do not follow the same order as the ASTM method. Nitrogen (N,) varies little for all ranks. Table 19 Since the quality of the volatile matter in coal is an System comparison of selected American coals index of the extent of the conversion of the original Classification carbohydrates to hydrocarbons, studies have been made State Count.? Seam ASTM International suggesting that the heating value of the volatile matter W.Va. McDowell Pocahontas #3 Ivb 333 will serve as an accurate criterion for classification by Pa. Clearfield Lower Kittaning mvb 435 rank. This criterion, develo ed on “purc coal” basis as W.Va. Monongalia f. .a. Pittsburgh hvAb 635 calculated in equation (12 , is listed in Table 21 under 111. Williamson No. 6 hvBh 734 Ill. K”0X No. 6 hvCb 821 Btu per Ib VM,,. lvh = low-volatile bituminous Composition of the fixed carbon in a11 types of coal is mvb = medium-volatile bituminous substantially all carbon. The variable constituents of hvAb = high-volatile A bituminous coals can, therefore, be considered as concentrated in hvBb = high-volatile B bituminous the volatile matter. One index of the quality of the vola- bvCb = high-volatile C bituminous - tile matter, its heating valuc, is perhaps the most im- Source, Bureau of Mines. portant property as far as combustion is concerned and bears a direct relation to the properties of the pure coals (dry, mineral-matter-free). The volatile matter in coals of lower rank, where the conversion of carbohydrates The International Classification of Brown Coals is to hydrocarbons has not progressed far, is relatively high shown in Table 20, where the term “brown coal” refers in water and CO, and, consequently, low in heating to coal containing less than 10,260 Btu/lb on the moist, value. The volatile matter, in coals of hi her rank, is ash-free basis. The six classes of coal, based on the ash- relatively high in hydrocarbons, such as metR ane (CH,), free equilibrium-moisture content, are divided into and, consequently relatively high in heating value. groups according to their tar yield on a dry, ash-free The analyses and heating values of the coal must be basis. This grouping indicates the value of these low-rank converted to the mineral-matter-free (“pure coal”) basis coals as fuel and as raw material for chemical purposes. Brown coals with high tar content are generally used as raw material in the chemical industry rather than as fuel. Table 20 Other criteria for the classification of coal by rank International classification of brown coals have been proposed by various authorities. (Gross calorific value below 10.260 Btu/lb)* A method of classifying, by computing the heating Group Parameter value of the residual coal with moisture (M), ash (A), Croup Tar Yield (dry, and sulfur (S) removed, has been used by Lord. This No. ash free), % Code Number is called the “H”value. 40 >?3 1040 1140 1240 1340 1440 1540 30 >20-25. ~~ ~ 1030~~~~ 1130~~~~ 1230~~~~ 1330~~~~ 1430~~~~ 1530~~~~ Btu - 4050 S loo 20 >15-20 1020 1120 1220 1320 1420 1520 (7) 10 >lo-15 1010 1110 1210 1310 1410 1510 .,. = 100 - (M + A + S) 00 lO&less 1000 1100 1200 1300 1400 1500 Class Number 10 11 12 13 14 15 While the H values as listed in Table 21 are of interest, Class Parameter, 20 20 30 40 50 60 they do not arrange the 17 coals in the same order as i.e., Total Moisture, and to to to to to the ASTM classification. (ash free), % less 30 40 50 60 70 Another classification method, reported by Perch and - I Russell, is based on the following ratio: Notes: The total-moisture content refers to freshly mined coal. For internal purposes, coals with a gross calorific value over 10,260 Btu/lb (moist, ash-free basis), considered in the country of origin Moist, Mm-free Btu as brown cosls but classified as hard coals for international pur- Ratio = (8) Dry, Mm-free VM poses, may be classified under this system. to ascertain, in particu- lar, their suitability for processing. When the tatnl-moisture content is over 30%, the gross calorific Values of this ratio for the 17 coals listed in Table 16 value is always below 10,260 Btdlb. arrange these coals in Table 21 in exactly the same order Moist, ash-free basis (BGF/SG% relative humidity). as the ASTlV method. The very high ratio for coal No. 1 Source, Bureau of Mines. .Steam / Sources of chemical energy 5-15 Table 21 Study of the suitability of other criteria in the classification of coals CWlk I5tU I'ClCh i\ 11hi Coal An;dysis, Dry, Ad-Frce Basis Tuldc 16 Lid's Il1,rall 1WI Grid No. I1 \'aluc IVatin ll,hl,,c VAf FC C 112 0 2 N. Ut,, ability 1 14,')50 ~ - 2.0 9R.0 93.9 2.1 2.3 0.0 14,850 37 2 15,180 2520 25,685 7.3 92.7 93.5 2.6 2.3 0.9 15,100 26 3 15,410 1358 23,330 13.6 8G.4 90.7 4.2 3.3 1.n 15,325 83 4 15,765 907 21,750 17 7 82.3 90.4 4.8 2.7 1.3 15,670 100 5 15,840 834 11,155 19.8 80.7 89.4 4.8 2.4 1.5 15,615 112 G 15,765 GtJ8 19,785 23.5 76.5 88.6 4.8 3.1 1.6 15,540 10.5 7 15,930 611 19,570 2G,5 73.5 87.G 5.2 3.3 1.4 15,G30 95 8 15,500 445 17,230 35.2 64.8 85.0 5.4 5.8 1.7 15,265 88 9 15,460 389 16,930 39.0 61.0 85.5 5.5 6.7 1.6 15,370 5G 10 15,230 322 15,450 45.8 54.2 80.9 5.7 7.4 1.4 14,730 57 11 14,800 320 14,875 43.8 56.2 80.5 5.5 9.1 l.G 14,430 GO 12 14,359 318 14,200 43.2 56.8 79.8 5.6 11.8 1.7 14,ZGO 50 13 14,830 300 14,690 49.3 50.7 79.2 5.7 9.5 1.5 14,400 61 14 14,170 295 13,885 40.8 59.2 80.9 5.1 12.2 1.3 14,110 55 15 13,145 229 11,435 42.8 57.2 75.9 5.1 17.0 1.6 13,100 43 16 13,055 181 11,570 49.0 51.0 74.0 5.6 18.6 0.9 12,970 52 17 12,400 170 9,945 45.3 54.7 72.7 4.9 20.8 0.9 12,330 45 Notes: For calculations of Lord's H Value and the Perch & Russell ratio, The subscript pc means on a "pure coal" basis. The dry, ash-free and the heating value of the volatile matter (pure-coal basis) VM may be used, instead of the VMpc, without appreciable error. refer to equations 7 to 12, inclusive, this chapter. Grindability is determined by ASTM Method D 409. in order to establish reasonably accurate heating values The Btu per lb volatile matter, calculated from the for volatile matter. The only difference in the convcrsion above formulas, is given in Table 21 for 16 of the 17 coals nsed for this method and the conversion used in the listed, covering the entire rangc of rank. The order of ASTM Standard D 388 is that half the sulfur is assumed these values follows generally the ASTM classification of to be pyritic on thc pure-coal basis. The assumption that the coals, although the correlation is not as good as with only half the sulfur is pyritic and the remainder organic the Perch and Russell ratio. The range of values of Btu is in closcr agreement with the average for a large num- per Ib volatile matter, from about 8000 to 28,000 (Fig. ber of US.coals. The formulas for converting the analy- 6), is large and may serve as a useful classification. ses and coal heating values to the "purc coal" basis and The relation of the heating value of the volatile matter for calculating the heating value of the volatile matter and the heating value of the pure coal is shown in Fig. are as follows: 6 for a large number of coals. It is evident that a fair line could be drawn, without serious error, to indicate VAT - (0.0SA + 0.2 S) the path of this relationship. x 100, % "'fpc = 100 - (1.0SA + 0.2625 S + A'f) FC - 0.0625 s Commercial sizes of coal x 100, % (lo) FCpc = GO - (1.08A + 0.2625 S + M) Bituminous. Sizes of bituminous coal are not well Rtu - 26.2 s standardizcd, but the following sizings are common: x loo, (11) Bt"PC = lool.08A + 0.2625 s + M) Run of mine. This is coal shipped as it comes froin Btu/lb thc mine without screening. It is uscd for both do- Btupc - (xFCpc)14,460 mestic heating and steam production. (12) I?tu/lb I'Mnc = __- - x loo, Run of mine (8 in.). This is run of mine with over- VAf,, size lumps broken up. Btu/lb Lrmp (5 in.). This sizc will not go throngh a 5-in. where : round hole. It is wed for hand firing and domestic VA/, FC, A, S, A{, and Btu are the same as noted purposes. previously for the Parr formulas. Subscript pc dc- notes "purc coal" basis. Egg (5in. X 2 in.). This size goes through 5 in. and is 5.16 Heating Value of Volatile Matter, 1000 Btullb Fig. 6 To illustrate a suggested coal classification using the relationship of the respective heating values of “pure coal” and the volatile matter. retained on 2-in. round-holc screens. It is used for librium at 10-15C above room temperature, and 2) pre- hand firing, gas producers, and domestic firing. scribed oven drying for one hr at 104-llOC, after pulverizing (see also ASTM Standard D 271). Nut (2 in. X 1% in.). This size is used for small in- The air-dried component of the total moisture value dustrial stokers, gas producers, and hand firing. should be reported separately, because this information Stoker coal (1% in. X 3/4 in.) is used largely for small is required in the design and selection of equipment. It industrial stokers and domestic firing. is the surface moisture having nom1 vapor pressure that must be evaporated prior to efficient pulverizing of Slack (3/4 in. and under) is used for pulverizers, Cy- anthracite and bituminous wal. clone Furnaces, and industrial stokers. ASTM Standard D 1412 provides a means of estimat- ing the bed moisture of either wet coal showing visible Several other sizes of bituminous coal are prepared by surface moisture or coal that may have lost some mois- different producers especially for domestic stoker re- ture. It may be used for estimating the surface, or ex- quirements. traneous, moisture of wet coal, i.e., the difference between Anthracite. Definite sizes of anthracite are standard- total moisture, as determined by ASTM Standard D 271, ized in Table 22. The broken, egg, stove, nut and pea and equilibrium moisture. Also, for classification of coal sizes are largely used for hand-fired domestic units and by rank, the equilibrium moisture of a sample is con- gas producers. Buckwheat and rice are used in mechani- sidered to be equal to the bed or inherent moisture. cal types of firing equipment. (ASTM Standard D 388.) Calorific value of coal Table 22 Commercial sizes of anthracite (ASTM D 310) The calorific or heating value of coal is determined ac- (Graded on round.hole screens) curately in an oxygen bomb submerged in cooling water. Diameter of Holes. Inches Several acceptable makes or types of bomb calorimeters Trade Name Through Retained On are listed in ASTM Standard D 271. A pulverized coal Broken 44’8 3-1/4 to 3 sample is compressed into a hard pellet and ignited in Egg 3-1/4 to 3 2-7/16 an oxygen atmosphere with a hot wire. The heating Stove 2-7/11?~ ~.._ 1.5/R~ ”. - value is then determined from the rise in water tem- Nut 1-5/8 13/16 perature. Pea 13/16 9/16 Buckwheat 9/16 5/16 Gross (higher) heating value is defined as the heat Rice 5/16 3/16 released from combustion of unit fuel quantity (mass), with the products in the form of ash, gaseous CO, , SO, , N,, and liquid water exclusive of any water added di- Moisture determination rectly as vapor. Thc net (lower) heating value is calcu- Moisture in coal is determined quantitatively by dcfinite lated from the gross heating value as the heat produced prescribed methods. It is prcfcrable to determine the by a unit quantity of fuel when all water in the products moisture in two steps: 1) prescribed air drying to equi- remains as vapor. This calculation (ASTM Standard . Steam / Sources of chemical energy 5-17 D 407) is madc by deducting 10:30' l%tu/Il~of wntcr Free-swelling index dorivcd from thc fnrl, iiiclttding Iiotli tlic w:itcr origi- The AST~MStnndnrd hlithod D 720 is uscd for obtaining nally prcscnt as nioisturc ;itid that forincd Iiy combits- information regording tlic frcc-s\\dling property of a tion. In Amcric;i tlic gross c;ilorific V;I~III: is cominonly coal. Since it is a ini~asurcof thc bchavior of rapidly used in Itcat 1xil;iiice c;iIculatioiis. \oliilc iii Ertropc the hcatcd coal, it may bc,uscd as nn indionti~~nof thc caking net valtic is gcncl.ally risid. charactcristics of cod burned as n fucl. Grindability of coal Coal ash Grindability is a tcmm uscd to niixsitrc thc case of pul- The nature, composition, and propcrties of coal ash are vcrizing a co;il in cotnp;irison \\,it11 a st:ndird con1 discussed in Chapter 15. chosen ns 100 grindnhility. For il description of thc method of testing to ,dcterinine grindahility of a coal, Characteristics of fuel oil see "Grindability Index (ASTM D 409);' Chnptcr 9. It is common practice in rcfining pctrolcum to produce Fig. 6 of the same chnptcr shows thc machine used in fuel oils complying with several specifications prcpared making,the test. The grindability of the 17 rcprescntative by the ASTM and adoptcd as a commercial standard by coals in Table 16 is tnhulated in thc last column of the US. Bureau of Standards. These standards have been Tablc 21. revised scveral times in order to meet changes in snpply ___ and dcniand and further changes may be expected. ' The value of 1030 Btu/lb of water, an average figure, corrects The current standards are tabulated in Table 23. Fuel for hath the latent heat of vnp&ation and conversion from con- stant volume conditions of the calorimeter to on eqnivalent con- oils arc graded according to gravity and viscosity, the stant pressure basis. lightest being No. 1 and the hcaviest No. 6. Grades 5 Table 23 ASTM standard specifications for fuel oils' No. 1 A distillate oil intended for vaporizing pot-type burnen No. 5 (Light) Preheating may be required depending on climate and other burners requiring this grade of fuel and equipment No, 2 A distill& ail for general purpose domestic heating for use No, 5 (Hew ) Preheatin may be required for burning and, in in burnen not requiring No. 1 fuel oil cold cktes, may %e required for handling No. 4 Preheating not usually required for handling or burning No. 6 Preheating required far burning and handling Water Carbon Tempe'nturer.Dirtillnlion Kinemafic Visrnsity. deB E Grade FIarh Pour and Residue F (Cl Sagbolt ViPFDlitY. see entistoker Grav- of Point, on 10% Ash. ity. 1 Pint. Sediment. Stri1 Fuel F F %by Bottoms. %by IO% 90% Univerral st Furol at At 4 Oil (C) (C) Volume % Weight Paint Paint IOOF (38Cl 122F (50C) ( API rosio Min Max Mar Max Mnr Max I Min I Mnx Min I Mar I Min I Mar ilin Mni Mi" Mar Mi" Mar 2.2 - 3.6 - 26.4) - (162) (42) - (92) *Recognizing the necessity for low-sulfur fuel oils used in connection lower grade unless in fact it meets all requirements of the lower grade. with heat-rreahnenl, nonferrous melHI, glass, and ceramic furnaces and c Lower or higher pour points may be specified whenever required hy other special UEOS. P sulfur requirement may be specified in accordance conditions of storage or we. with the following tnble: 4 The 10% distillation temperature point may be specified it 440F Grade of (226C) maximum for use in other than atomizing burners. Fuel Oil Sulfur, Max. X e When pour point lerr than 0 F is specified, the minimum viscosity shsll No. 1 ...... 0.5 be 1.8 er (32.0 sec, Sayboll Universal) and the minimum 90%point shall Na.2 ...... 0.7 be waived. No. 4 ...... no limit I Viscosity values in liarentheses are for information only and not neces- No. 5 ...... no limit sarily limiting. No. 6 ...... nolimit 6 The amount of water by distillation ~IUIthe sediment by extraction Other sulftm limits may be specified only by mu~uolagreement between shall not exceed 2.00%. The amount of sediment by extraction shall not the purchaser and the der. exceed 0.50%.A deduction in quantity slid be made for a11 water and sediment in excess of 1.0%. 18 ~t is the intent of these classifications that failure to meet my require- ment 8 give!, grnde does not automuticnlly place an oil in the next Source, ASTM D396. 5-18 xid G gcncrdly r(x1iiirr Iic:itiirg for s:itisf:ictory pumping 20.0 iiiid burning (see Oil Dirr.ncrs, Cliol>ter 7). Analyses ;uid - @Y rclativc cost of soiitc srlactcd fucl oils arc lislcd in Tablc 19.8 9 $?! 24. The range of ;inalyscs and 1ic;iting v:ilues of tlic z 28 Is scver:il gradcs nf fucl nils arc givcn in Tablc 25. 19.6 '$ 1.03 The gross hc;iting volrtcs of verions fucl oils of differ- G : 1.01 ent gravity arc shown in Fig. 7. The abscissa on this .2 figurc is the API (Amrric;iii Petroleum Institute) gravity. 5 8.9 0.99 Ilcgrccs API rvfcr to a hydromctcr scale with the follow- # 19.4 8.7 0.97 ing relation to specific gravity: .-s 19.2 8.5 0.95 I y1 3 8.3 0.93 D 141.5 E (13) Ilcgrccs API = -- - 131.5 19.0 8.1 0.91 81) gr 0. (iO/liOF s - 7.9 0.89 where: -m sp gr @ 60/60F represents the ratio of oil dcnsity g- 18.8 7.7 0.87 >it60F to watcr dcnsity also at 60F. -m 7.5 0.85 c" 18.6 7.3 0.83 The heating valucs, as listed in Fig. 7, are closely related to the gravity of the oil. The heating value for an actual 7.1 0.81 oil is obtained by correcting the Btu/lb valuc from Fig. 18.4 6.9 0.79 7 as f~llows: 6.7 0.77 18.21 I I 1 I I i ' 1'1 I 6.5 0.75 0 10 20 30 40 50 I3t~/lhX [I00 - (A + M + S)l + 40.5 60 (1'0 100 Gravity. Deg API 141.5 where: DegAPI = SpGrk60,60f-131.5 Btu/lb is taken from Fig. 7 Fig. 7 Heating value, weight (Ib per gal), and specific gravity A = % by wt of ash of fuel oil for a range of API gravities. A! = % by wt of watcr S = "/o by wt of sulfur is also dependent on the API (American Petroleum In- The volume percentages of water and sediment can be stitute) gravity range as illustrated by the three para- used without appreciable error in place of weight per- metric curves of Fig. 8. centage where the percentages by wcight of water and Since handling and especially burning equipment is ash arc not known. usually designed for a maximum oil viscosity, it is neces- Fuel oils are generally sold on a volume basis with sary to know the viscosity characteristics of the fuel oil 60F as the basc temperature. Correction factors are to be used. If the viscosities of heavy oils are known at given in Fig. 8 for converting known volumes at other two temperatures, viscosities at other temperatures can temperatures to the 60F standard base. This correction he closely predicted with negligible error by a linear interpolation between these two values located on the Table 24 standard ASTM chart of Fig. 9. Viscosity variations with Selected analyses and relative cost of fuel oils . temperature for certain light oils can also be found with Grade of Fuel Oil No. 1 No. 2 No. 4 No. 5 No. 6 the aid of the ASTM chart but in this case knowledge Weight, percent of the viscosity at only oiic temperature is required. Sulfur 0.1 0.3 0.8 1.0 2.3 Viscosities of light oils at various temperatures within Hydrogen 13.8 12.5 - - 9.7 the region designated as No. 2 fuel oil can be found by Carbon 86.1 87.2 - - 85.6 drawing a line parallel to the No. 2 boundary lines Nitrogen - 0.02 - 2.0 through the point of known viscosity and temperature. Oxygen Nil Nil - Ash Nil Nil 0.03 0.0311 0.12 Copies of the chart may bc obtained from thc ASTM. Compared with mal, fuel oils are relatively easy to Dig API 42 32 20 19 - handle and burn. Heating is not required for the lighter Specific 0.815 0.865 0.934 0.940 - oils, and evcn the heavier oils are relatively simple to Lb .-Der ad 6.79 7.21 7.78 7.83 -. handle. There is not as much ash-in-bulk disposal proh- Pour point, F -35 -5 +20 +30 - lem as there is with coal, and the amount of ash dis- Viscosity charged from the stack is correspondingly small. In most Centistokes oil burners the oil is atomized tn a mist of small pnrticles @ IOOF 1.8 2.4 27.5 130 - that mix with combustion air. In thc atomized state, the SUS @ lOOF - 34 130 - - SSF @ 122F - - - 30 - characteristics of oil approach those of a gas, with con- sequent similar explosion hazards (see Snfety Water bi sediment, Precao- vol % Nil Nil 0.2 0.3 0.74 tions, Chapter 7). Heating value Rccausc of its rclatively low cost compared with that Btu per Ib, of lighter oils, No. 6 fuel oil is the most widely used for gross 19,810 19,430 18,8GO 18,760 18.300' stcam generation. It ciiii bc considered a by-product of llclative cost per Btu 118 inn 76 60 51 the refining process. Its ash content ranges from about 'Bombcnlorirneter determination. 0.01 to 0.5')4>, which is very low compared with coal. Steam / Sources of chemical energy 5.19 Table 25 Range of analyses of fuel oils Cmdc of Fiiel Oil No. I No. 2 No. 4 No. 5 No. 6 Wcight. percent Solfur 0.01-0.5 0.05-1.0 0.2-2.0 0.5-3.0 0.7-3.5 Hydrogen 13.3-14.1 11.8-13.9 (10.6-13.0)' ( 10.5-12.0)0 (9.5-12.0)' Corhon 80.1-88.2 (86.5.89.2) ( 86.5-89.2)e (86.5-90.2)' Nitrogen Oxygen Ash Gravity Deg API 40-44 28-40 15-30 14-22 7-22 S ecific 0.825-0.806 0.887-0.825 0.966-0.876 0.972-0.922 1.022-0.9l?? L% per gal 6.87-6.71 7.39-6.87 8.04-7.30 8.10-7.68 8.51-7.68 Pour point, F 0 to -50 0 to -40 -10 to +50 -10 to +80 +I5 to +85 Viscosity Centistokes @I IOOF 1.4-2.2 1.9-3.0 10.5-65 65-200 260-750 SUS 0 IOOF - 32-38 60-300 - - SSF 0 122F - - - 20-40 45-300 Water & sediment, vol % - 0-0.1 tr to 1.0 0.05-1.0 0.0 5 - 2.0 Heating value 17,410-18,990 Btu per Ib, gross 19,670-19,860 19,170-19,750 18,280-19,400 18,100-19,020 (calculated ~ *Estimated 0.97 0.96 33 ! ! ! ! ! ! ! ! ! ! ! ! I I NWI I I I ! I NU Vol G 60F = Vol @tx F. \ 0.95 I I 0 20 40 60 80 loo 120 140 1M) t =Temperature. F Fig. 8 Temperaturevolume correction factor for fuel oil Note: On the scale at the left, find the SUS viscosity at IOOF (standard test temperature) for the given oil; move horizontally to the vertical line for 100F. From However, despite this low percentage content, ash con- this intersection move parallel to the diagonal lines ta.the taining compounds of vanadium, sodium and sulfur can viscosity required for atomization; the temperature neces- sar to achieve this viscosity can be read the bottom resaonsible for a number serious operating on bc of . _.prob- scare. The chart, based an US. Cammerical Standard lcms ('Chapter 15). 12-48 has been developed from data for many fuels and Fuel oils generally available on the Eastern seaboard should be sufficiently accurate for most applications. are prodttccd from varying amounts of Venezuelan and Middle East crudes, depcnding on the relative quantities of shipments and on the blending at the refineries to Fig. 9 Approximate viscosity of fuel oil at various tempera nrcct No. G fuel-oil viscosity specifications. Fuel oils ttsed tures. (Source, ASTM.) 5-20 on the Gulf nnd West Coasts are produced largely from usad and, also, ;uay supplen1cnt;ay crudc oil uscd in the hncstic crudes, altliough they may contain some Venc- fcrdstock. At the prevniling cmt of producing oil from zuclnn crudc. I3ccausc of this it is difficult, if not im- pctrolcum, it has not been coiniaicrcially attractive to possiblr, to idcntify tlac source of fuel oils as fired. producc oil products from oil shale in the US. Shale oil Characteristics of natural gas An analysis of a typical Grcen River oil shale from the Of nll chcinical fuels, natural gns is considered the most Colorado-Utah-Wyoilling nrcn is given in Table 26. Fuel oils produced froin rcfinerics using shale oil feedstock on ilcsirablc for steam generation. It is piped directly to a commcrcial scale arc unavailable. Characteristics of tlac consuincr, eliminating the need for storage at the consumer's plant. It is snbstnntinlly frcc of ash, and the fucl oil will depcnd on the refincry processes to be mixes intimately with air to provide complete coinbus- tion at low excess air without smoke. Although the total Table 26, hydrogen content of natural gns is high, the amount of Analysis of a Green River oil shale free hydrogen is low. Because of this characteristic, Physical properties natural gas is not as cnsy to burn as some manufactured Specific gravity, GOL;/GOF 2.3 gnscs with their high free hydrogen content. Bulk density, 48 mesh, The high hydrogen content of natural compared 67.8 , gas Ih/cu ft with that of oil or coal results in more water vapor pro- Oil-shale assay,' % by wt Oil 10.3 duccd in the combustion gases with a correspondingly Cas 2.5 lower efficiency of the steam generating equipment. This Water 1.4 cnn readily be taken into account in the design of the 3.1 Organic residue equipment and evaluated in comparing- the cost of gas Mineral residue 82.7 wkh-other fuels. Yield in oil, gal per ton 26.7 Analyses of natural gas from several US. fields are Mineral residue, wt % of raw shale given in Table 27. Mineral COz evolved 20.0 Mineral analysis of ash Silica as Si02 26.4 Relative costs of the three major fuels Calcium as CaO 17.1 Magnesium as MgO 5.4 Transportation of fuels is an important factor in fuel Aluminum as A1203 6.6 costs, particularly in the case of coal which is not as Alkalies Y NazO & K20 3.7 Iron as Fez03 2.6 readily pumped through pipclines as are oil and gas. A Phosphorus & Vanadium as PzOs & VzOs 0.4 number of methods for reducing the cost of transporting Sulfur as So3 0.5 coal have been or are being tried (Chapter 8). Several ~ Modified Fischer assay. large electric generating plants have been built at the Table 27 Selected samples of natural gas from United States fields Sample No. 1 2, 3 4 5 Source of Gas Pa. so. Cal. Ohio La. Okla. Analyses Constituents, % by vol Hz Hydrogen - - 1.82 - - CH4 Methane 83.40 84.00 93.33 90.00 84.10 Czb Ethylene - - 0.25 - - C2H6 Ethane 15.80 14.80 - 5.00 6.70 CO Carbon monoxide - - 0.45 - - COz Carbon dioxide - 0.70 0.22 - 0.80 Nz Nitrogen 0.80 0.50 3.40 5.00 8.40 Oz Oxygen - - 0.35 - - HzS Hydrogen sulfide - - 0.18 - - Ultimate, % by wt s Sulfur - - 0.34 - - Hz Hydrogen 23.53 23.30 23.20 22.68 20.85 C Carbon 75.25 74.72 69.12 69.26 64.84 Nz Nitrogen 1.22 0.76 5.76 8.06 12.90 0, Oxygen - 1.22 1.58 - 1.41 Specific gravity (re1 to air) 0.636 0.636 0.567 0.600 0.630 Higher heat value Btu/cu ft @ 60F & 30 in. Hg 1,129 1,116 964 1,002 974 Bhdlb of fuel 23,170 22,904 22,077 21,824 20,160 Steam / Sources of chemical energy 5.21 mini: site in sitii;iti,ins wlicre it is cconomical to trans- LOO port clcctricity rnthcr than coal. Costs of all fuc:ls vary from ycir to ycnr and cvcn 580 0 seasonally so that, in the siiinc locnlity, first one and then .. - another fucl may hi3 thc inoro cc~inoniicnl to usc. In 5 60 YI I sonic parts of the country, stcam gcncrating cquipmcnt c is arrmigcd to burn ;ill thrcc fuels-coal, oil or natural 40 8 gas. Table 28 shows thc “as-consumcT fucl costs for 0 thc ycer 1968 for stcam clcctric plants located in the 7’ 20 Middle Atlantic and Ncw Ihgland Coast arcas. The as- li 0 consiimcd cost of nntural gas is xsiiiiicd to be tlic same 0 20 40 MI 80 100 120 as the delivercd cost. Thi: pi~ccntof the totnl cncrgy, on Natural Gar. Cents/ IWO cu 11 a Btu basis, supplied by cwh fucl is also indicatcd. 0123456789 Residual Fuel Oil, CenlslGal Table 28 0 2 4 6 8 IO 12 14 16 18 Aseonsumed fuel costs of steamelectric plants, 1968 Coal, DallarrlTon CcnWMillinn Btii Pcrcent of. Tnlnl Btu Fig. 10 Comparative fuel costs in cents per million Btu. State or City Coal Oil Cnr Coal Oil Gar Maine - 30.4 - 0 100 0 Marsnchusctts 30.7 29.1 31.7 32 65 3 portions crack on contact with the hot carbon, leaving Connecticut 32.5 29.3 31.G 46 54 - ini ndditional qu;rntity of cnrbon. Thc carbonaceous resi- Rhode Island 41.0 30.8 33.G 15 77 8 dtic cont:iining the ash and a part of the sulfur of thc New York City 38.0 34.9 37.1 30 48 22 New ersey 33.0 35.4 31.4 46 48 6 original cod is callcd “coke.” The amount of sulfur and Philadelpliia 32.4 33.3 30.2 GG 33 1 the ;nnount and nature of the ash in the coke depend in Delaware 31.2 61.0 31.1 81 G 13 large mcasure on the coal from which it is produced and Source, National Coal Association. thc coking proccss used. The principal uses for cokc are in the production of pig iron in blast furnaccs and thc Table 24 lists rclativc costs for various grades’of fuel chnrging of iron foundry cupolas. Because it is smokeless oils. Because of thc proportionately great variations over in combustion, considerable quantities have bcen used periods of time and in different localities, these, rclative for space heating. costs can only serve as a rough approximation. Coke production and consumption in millions of tons The cost of natural gas in the US.closc to the sourcc for thc ycnr 1968 are tabulatcd as follows: is about 12 cents per million Btu and increases up to 70 Total coal uscd for cokc production 91.3 cents further from the sourcc. Since a large percentage Total annual coke production 63.7 of natural gns is used for space heating, the demand for Coke breezc produced 4.1 natural gas is considerably higher during winter months. Coke breeze used for steam gener a t’ion 0.5 During summer, natural g?s may be available at rela- Coke breeze used for sintering iron ore 1.6 tively low cost for steam gcneration, cvcii in arcas at a considerable distance from the source. However, some Undersized coke callcd “coke breeze,” usually passing nahiral gas is now being stored underground during the a 5/8-in. screen, is unsuited for charging blast furnaccs summer in consumer areas rcmote from gas fields to hold and is available for steam generation. A typical analysis it for higher winter prices. Morc and more industrial of coke brceze appears in Table 29. Approximately 4.570 boilers up to sizes of 250,000 Ib of steam per hour are by weight of thc coal charged into slot-type coke ovens is using oil and natural gas fuels year-round. Thc supply rccovcrcd as breeze. of natural gas is currently greater than pipeline capacity. As pipeline capacity is increased, the cost of natural gas Table 29 may approach that of oil and coal, even in areas ncar its Selected analyses -bagasse. coke breeze, and fluidized-bed char source. Comparative costs of coal, oil, and natural gas in cents per million Btu are shown in Fig. 10 over a widc Fluidized- range of costs for these three fuels. Analyses (as fired), % by wt Bagasse Bed Char Prodmate Other fuels for combustion Moisture 52.0 7.3 0.7 Volatile matter 40.2 2.3 14.7 Among othcr fuels used, those derived from coal are the Fixed carbon 6.1 79.4 70.4 most important. Also uscd are petroleum by-products; Ash 1.7 11.0 14.2 wood, its by-products and wastes from wood-processing Ultimate industries; and certain types of vegetation, particularly H2 Hydrogen 2.8 0.3 - bagasse. C Carbon 23.4 80.0 - s Sulfur trace 0.6 4.1 Coke N2 Nitrogen 0.1 0.3 - When coal is heated in the absence of air or with a large 02 Oxygen 20.0 0.5 - deficiency of air, the lightcr constituents are volatilized H20 Moisture 52.0 7.3 - and the hcavier hydrocarbons crack, liberating hydrogen A Ash 1.7 11.0 - and [caving a residue of carbon. Some of the volatilized Heating value, Btu/lb 4000 11.670 12.100 5.22 Until the Lite 194Os, roughly three-fourths of thc dcnsnblc portioii is called “coke-oven ” Constituents breeze produccd at cokc oveii plants was uscd by the dcpcnil 011 thc nature of tlic coal and t IL coking’ process producing companic,s for stcani gcncmtioo. Io 1968 the used (T;iblc 30). Y’ usc of brcczc for stcam generation amounted to only A part of the sulfur from coal may be prcsent in cokc- 12.4% of the output. This rcdnction was, in large part, oveii gis iis hydrugcn sulfide ;ind carbon disulfidc. These the rcsult of increased rcquircmcnts for cokc brcczc for may bc rcmoved by scruhhing. Coke-oven gas often con- sintering iron ore. tains otlicr impuritics that deposit in lines and burners requiring the use of relatively large bumcr-gas-port Tars and char openings to rcducc plugging. Also, burners arc arranged A portion of the coal tars produccd as a by-product of for easy iicccss and cleaning. Coke-ovcn gas burns read- thc various coking proccsses may bc burned in equip- ily bccnusc of a high frec-hydrogen contcnt and presents mcnt similar to that uscd for heavy petroleum oil. Low no problems when uscd as fuel for steam gcncration ex- temperature (900 to 11OOF) carbonization processes have cept for the buildup of deposits. been devclopcd for the extraction from coal of valuable Approximatcly 14 to 16% by weight of the coal tars, bitumens and gascs for use as raw materials in the charged into slot-type cokc ovens is recovered in the chcmical industry. The by-product solid fuel from these form of a fuel gas. In 1968 a total of 923 billion cu ft of proccsses is called char. Disco char, produced by low coke-oven gans was formed from 90.0 million tons of coal temperature carbonization has bccn sold for use in the averaging 10,251 cu ft per ton of coal carbonized. A domestic and smnll comnicrcial fuel market. Char which breakdown of gns produccd in 1968 shows 36.0% used appears to havc the greatest commercial significance is to heat coke ovens, 56.5% used by thc producing com- that produccd by the fluidized-bed method. At present, Ties,in st+ and allied plants and in boilers, 4.0% sold economics has curtailed the widespread use of any of or residential, commercial, and industrial heating, and these processes. A typical analysis of fluidized-bed char 1.5% wasted. is given in Table 29. Blast-furnace gas. The gns discharged from steel mill Gaseous fuels from coal blast furnaces is uscd at the mills in heating furnaces, gas engines, and for steam generation. This gas is quite A number of gaseous fuels are derived from coal both variablc in quality but is generally of high carbon mon- as by-products and from coal gasification processes. oxide content and low heating value (Table 30). Table 30 lists selected analyses of these ases according The gas is discharged from the furnace at about 500F to the various types dcscribed in the H’ollowiog para- and contains 5 to 7 grains of entrained dust per cu ft. graphs. At the present time they have been largely sup- This gas may be burned directly for steam generation. planted by natural gas and oil. However, improvements However, at many mills, cntrained dust is first removed in coal gasification and wider use of coal in the chemical by washing or by electrostatic precipitation. Wet washed and liquid fuel industries could reverse this trend. gas, from many types of washers, will have a dust load- ing of 0.1 to 0.2 grains per cu ft. Table 30 Selected analyses of gaseous fuels derived fmm coal Both dirty and wet washed gas burned for steam gen- cration can cause trouble by plugging gas lines and Column No. 12 34 burner ports and fouling boiler heating surfaces. Blast- furnace-gas deposits adhere very firmly, and provisions Analyses, 9o by vol must be made for cleaning boiler heating surfaces. Be- H2 Hydrogen 47.9 2.4 34.0 14.0 cause of the nature of the deposits, wet washed gas is CH4 Methane 33.9 0.1 15.5 3.0 often more troublesome than hot, dry, dirty gas. Electro- CzHq Ethylene 5.2 - 4.7 - statically cleaned gas may or may not cause trouble, CO Carbon monoxide 6.1 23.3 32.0 27.0 depending on the collector efficiency. CO2 Carbon dioxide 2.6 14.4 4.3 4.5 When blast-furnace gas is used for steam generation, N2 Nitrogen 3.7 56.4 6.5 50.9 special safety precautions are required because of fluc- 02 Oxygen 0.6 - 0.7 0.6 tuations in gas supply from variations or interruptions C6H6 Benzene - - 2.3 - in blast furnace operation. Also, an alternate fuel must H20 Water - 3.4 - - be immediately available in cases where the steam pro- Specific gravity (relative to air) 0.413 1.015 0.666 0.857 duction rate must be maintained. Higher heat value-Btu/cu ft Water gas. The gas produced by passing steam @ 6OF & 30 in. Hg 590 - 534 163 through a bed of hot coke is known as water gas. Carbon @ 80F & 30 in. Hg - 83.8 - - in the coke combines with the steam to form hydrogen and carbon monoxide. This is an endothermic reaction Col. No. Kind of Gas Col. No. Kind of Cas which cools the coke bed. General practice is to replace 1 Coke-oven gas 3 Carbureted water gas stcam periodically by air for combustion of coke in or- 2 Blast-furnace gas (lean) 4 Producer gas der to regain the required bcd temperature. While the air is passing through the bed, the discharged products Coke-oven gas. A considerablc portion of coal is con- of combustion are diverted to the atmosphere to avoid verted to gases or vapors in the production of coke. Valu- diluting the water gas with noucombustibles. able products recovered from these gaseous portions Water gns is often cnrichcd with oil by passing the gas include ammonium sulfate, oils and tars. The noocon- through a chcckerwork of hot bricks sprayed with oil . Steam /Sources of chemical energy 5-23 which in turn is cr;ickcd to a gm liy tlic hc:it. Ilcfitit,ry tcristics. Melting piiints wry coirsidcl.al~ly:d the pliysi- gas is dso uscd for cnrichmcnt. It may citlicr IIC: iniscd cal propcrties vary from soft ;ind gutniny to hard and with the stem xnd ~~ISSC~through the kc bcd or fri;tl,lc. The low melting point pitchcs inay I)c 1ic;itcd niiscd directly with tlic witcr gas. Siich i:nriclicd water and \)urncd like licnvy nil, while those with higher ndt- $as is called “c;irhurctcd witcr gis” (Tnlilo 30) ;ind it ing points may bc pdvcrizcd ;ind l~uriicd,(ir cruslicd IS piped for relatively short distanci~sthrough city niiiiiis ;ind burncd in tlic Cycloiic Furnace. for inc1nstri;il mid domcstic c~insiiinption.\Vhcre it is so Woad used, it is clcancd at thc sourcc to rcmovc sulfur g;iscs Salccted analyses and heating vducs of several typcs of :ind other iiiipuritics. In many :irc:is IISC of carhiirctcd water &is has hcen rcplaccd by nntur;il gis. wood (also analyses of wood ash) are givcn in Tnblc 32. Wood, in coininon with dl types of vegct:ition, is coni- Producer gas. When coal or coke is liurncd with a posed primarily of carbohydrates and consequently has dcficicncy of air and a controllcd anioiuit of moisture ii rclativcly low heating value comparcd with bituminous (stcam), a gas known ;is produccr gis is olitaincd. This coal nnd oil. gas, nftcr removal of entraincd ash and sulfur coni- Wood bark may pick up impurities during transporta- pounds, is uscd near its sourcc because of its low Iicat- tion. It is common pmctice to drag tlic rough logs to ing value. centrnl loading points in the logging area. This rcsults in Gasification using in-situ combustion of coal has been sand pick-up. Where the logs arc salt-water borne, bark carried out by the Burcau of Mincs on an cxpcrimentnl will absorb sen water with its iiicludcd salt. Combustion basis at Gorgas, Alabama. The xirposc of thcsc tests tempcraturcs from burning dry bark may be high was to demonstrate that energy /rom coal in scams too enough for impurities to causc fluxing of refractoly fur- thin for mining could be made available through undcr- nacc walls and fouliiig of boiler hcating surfaccs, unlcss ground gnsification. Russia has made produccr gas for sufficient furnacc cooling surface is provided. Sand pass- pwar gyeration using this process. This means of gasi- ing through the boiler banks can causc erosion of boilcr cation IS not economically competitive in the US. at the present time. Table 32 Coke from petroleum Analyses of wood and wood ash Thc he;ivy residuals from thc various petroleum crack- Wood analyses Pine Oak Spmcc Redwood (dry basis), % by wt ing processes arc prcscntly utilized in a number of ways -_-Bark Bark Bark’ -Bark‘ to produce a higher yield of lighter hydrocarbons and a Proximate solid rcsiduc suitablc for fucl. Characteristics of these Volatile matter 72.9 76.0 69.0 72.6 residues vary widely, depending on the proccss used. Fixed carbon 24.2 18.7 2G.G 27.0 Solid fucls from oil include dclaycd coke, fluid coke and Ash 2.9 5.3 3.8 0.4 petroleum pitch. Some sclectcd analyses arc givcn in Ultimate Table 31. Hydrogen 5.6 5.4 5.7 5.1 Carbon 53.4 49.7 51.8 51.9 Table 31 Sulfur 0.1 0.1 0.1 0.1 Selected analyses of solid fuels derived from oil Nitrogen 0.: 0.2 0.2 0.1 Analyses (dry basis), Oxygen 37.9 39.3 38.4 42.4 % bywt Delayed Coke Fluid Coke Ash 2.9 5.3 3.8 0.4 Proximate Heating value, Btu/lb 9030 8370 8740 8350 Volatile matter 10.8 9.0 6.0 6.7 Ash analyses, % by wt Fixed carbon 88.5 90.9 93.7 93.2 Ash 0.7 0.1 0.3 0.1 Si02 39.0 11.1 32.0 14.3 Ultimate Fez03 3.0 3.3 6.4 3.5 Sulfur 9.9 1.5 4.7 5.7 Ti02 0.2 0.1 0.8 0.3 Heating value, BtuAb 14,700 15,700 14,160 14,290 AI203 14.0 0.1 11.0 4.0 hlna04 Trace Trace 1.5 0.1 CaO 25.5 64.5 25.3 6.0 The delayed coking process uscs residual oil heated MgO 6.5 1.2 4.1 6.6 and pumped to a reactor for coking. Cokc is dcposited Na20 1.3 8.9 8.0 18.0 as a solid mass and is subscquently strippcd either mc- K20 6.0 0.2 2.4 10.6 chanically or hydraulically, in the form of lumps and so3 0.3 2.0 2.1 7.4 granular material. Some of these cokes arc easy to burn C1 Trace Trace Trace 18.4 and pulverize, while others are quitc difficult. Ash fusibility, F Fluid coke is produced by spraying hot residual feed Reducing onto externally heated sced coke in a fluid bed. The Initial deformation 2180 2690 fluid cokc is rcmoved as small pnrticlcs, which arc built Softening 2240 2720 up in laycrs similar to an onion. This coke can hc pul- Fluid 2310 2740 verizcd and burned, or it can be burned in the as-rc- Oxidizing ceivrd size in a Cyclone Furnace. Both types of firing Initial deformation 2210 2680 rcquirc sotnc supplcmental fuel to aid ignition. Softening 2280 2730 The process producing pctroleiim pitch is an altcrnatc -Fluid 2350 2750 to the caking process and yields fucls of various charac- O’Salt-water stored. 5-24 tnlii:s, p;irticiil;irly il the saiid I~iacliiig01‘ tlic Ilur, giiscs is ents arc rcmovrd in the .distillation proccss, with the incrws(d by ri~ti~riringcollcctd m~t~~rialki 111~: lur~r:lcc rrsult that the rcsidue is sonicwliat more difficult to from liopp,rs or dnst collcctors. Siiclr coll<.ctorsmay bo Iiiirn. Otlicr thm this, fuel properties itre much the same n~liiirctlwith sonic typcs of Id-hriiiup, cqiiipmcnt to iis those of tlic riiw wood, ;ind the problcms involved in rcdncr tlic stack discharge of inc~im~ili~t~~lyIniriicd liark utiliz;itioii ;ire similar. to ;icc(y tablc li mi Is. \\iwd or bark with ni~iirturc~cnntcnt oS 509, or lcss Bagasse burns quito wt.ll; Iiowcwr, iis tlic moistnrc content in- Mills grinding sugar ciine coininonly usc bngnssc for cr(xsi.s :iliovc this ;iinount, c~niiliiisti(niIicconic:~ nioro st<”;iin production. The mills nonnally operate 24 hours Micult. \\’it11 nioisturc content nlxwc G5‘j,, a large part per day during the grinding season. The supply of of tlw htill tlic. wood is rcquircd to cv:ipor;itc tlrc mois- bngnssc will easily equal that required to nicet the lant tnrc, ;nid littlc rcniiiilis for stc;nn generation. l3urning of stcam demands in mills where the sugar is not re l.ned this wet bark I)cco~ncsii mealis of ~lisposalriitlier th;ni a Consequently, where tlicrc is no other market for the soiircc of energy. bapssc, no particular effort is made to burn it efficiently, “I-Ioggcd” wood and bark iirc \’cry bulky and rcqnirc md burning equipment is provided that will burn the relatively large 1i;indling nnd storage equipment (see bagasse as received from the grinders. In plants where Wood He/irse, C/in))ter 27). Unintcwupted flow from refining is done, supplcmcntal fnels are required to pro- bunkers or bins through clrutcs is difficult to maintain, vide the increased steam demands. Greater efforts to ob- and avnilablc cqnipnicnt for this piirposc is not nlw:iys tain higher efficiency are justified in these plants. A satisfactory. srlectcd nnnlysis of bagnsse is given in Table 29. Wood wastes. Therc arc several industries using wood Other vegetation wastes as a rnw matcrial where combustible by-products or Food and related industries producc numerous vegetable wastes are available as fuels. The most important of these wastes that are usable as fuels. They include such ma- arc the pulp and turpentine industries. The nature and terials as grain hulls, thc residue from the production methods of utilization of the coml~ostibleby-product of furfural from corn cobs and grain hulls, coffee grounds from the pulp industry are discussed in Chapter 26. from the production of instant coffee and tobacco stems. Thc rcsidue remaining after the stcam distillation of Fucls of this type are available in such small quantities coniferous woods for the podtiction of turpentine is us- that they are relatively insignificant in our total energy ;ible as a fuel. Some of the more easily bunicd constitu- rcquircnicnts. ‘r, a