March 16, 1954 w_ J, MATTOX 2,672,410 GASIFICATION OF CARBONACEOUS SOLIDS Filed D60. 1, 1949

EXCHANGER

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O2 INL£T /4/ STEAM INLE7"_ 2 f ' f Patented Mar. 16, 1954 2,672,410

UNITED STATES PATENT OFFICE 2,672,410 .GASIFIGATION OF CARBONACEOUS SOLIDS William J. Mattox, Baton Rouge, La.,assignor to Standard Oil Development Company, a corpo ration of Delaware Application December 1, 1949, Serial No. 130,493 15 Claims. (01. 48-206) 2 The present invention relates to the production the gas generator in a so-called single-vessel sys of gases fromynon-gaseous carbonaceous ma tem or a continuous circulation of suspended terial, and speci?cally to the production of gas solid carbonaceous material to a separate heater mixtures containing carbon monoxide and hy in which heat is generated by combustion of the drogen, such as water gas, from such carbona carbonaceous constituents of the residue, and re ceous materials as coke and coals, wherein the circulation of the highly heated ?uidizable com formation of carbon dioxide is repressed by the bustion residue to the gas generation zone to sup~ addition of an alkali metal halide. ply the heat required therein in a so-called two It has long been known that solid fuel ma vessel system. terials, such as coke, coal, and the like, may be 10 The single-vessel system would as such; be converted into more valuable gases which can more desirable than the two-vessel system be more easily be handled and more efficiently uti cause the latter requires the circulation of tre lized for a greater variety of purposes. One of mendous quantities of solids between the two the most widely practiced gas-generating con vessels, a factor which presents serious problems versions is the so-called water-gas process in 15 of design and equipment maintenance. However, which solid fuels, such as coal or coke of any single-vessel operation involves the disadvan origin, are reacted with steam at temperatures tage of product gas dilution with nitrogen and of about 1400" to 2000° F. to produce water gas carbon dioxide when air is used as the combus mixtures of carbon monoxide and hydrogen in tion-supporting gas. Since technically pure oxy varying proportions, depending mainly on the 20 gen has become available at relatively low cost, time of contact, conversion temperatures, and nitrogen dilution may be eliminated by the use steam feed rate. The overall water gas reaction of oxygen in a commercially feasible operation. being endothermic, heat must be supplied; this However, carbon dioxide formation remains a is usually accomplished by the combustion of a problem seriously affecting the practicability of portion of the carbonaceous feed with an oxidiz the otherwise preferable single-vessel system. ing gas, such as oxygen, at about 1600°-2400° F. Recent investigations have shown, for example, The combustion reaction may be carried out that in a gasi?cation ‘operation employing 2300 either simultaneously with the water gas reac lbs. of powdered coal, 1700 cu. ft. of oxygen and tion or alternately in a make-and-blow fashion. 2000 lbs. of steam per hour to produce 70,000 cu. The water gas process permits the production 30 ft. of water gas, the product gas contains about of gas mixtures of varying composition and 16% of CO2. This carbon dioxide represents a B. t. u. content. The process as such, therefore, total loss as far‘as the output of hydrogen or is suited not only for the production of fuel gases synthesis gas is concerned. The significance of but also for the production of gases for hydro this loss will be appreciated when it is borne in genation processes and particularly for the cata 35 mind that the present methods of synthesis gas lytic synthesis of hydrocabons and oxygenated production account for about 60% of the cost of organic compounds from C0 and H2, which proc synthetic fuel production. Although CO2 forma ess requires H2:CO ratios, depending on the tion may be reduced to a certain extent by ad products desired and reaction conditions to be justing operating conditions, this can be done maintained, varying within limits of about 0.5 to 40 only at the expense of generator capacity. 2.5 or more volumes of H2 per Volume of CO‘. The present invention substantially alleviates The technical utilization of the water gas proc these difficulties and a?ords various additional ess, particularly for hydrogenation and for pro advantages as will appear from the description duction of synthesis gas, has been impeded by given below wherein reference will be made to difficulties encountered particularly in heat sup 45 the accompanying drawing. ply, continuity of operation, and limitations in In accordance with the present invention, car temperature imposed by low ash fusion or soften bon dioxide formation is considerably reduced ing points. The problem of continuity of opera and even substantially eliminated in water gas tion has been satisfactorily solved heretofore by generators wherein carbonaceous solids are gasi the application of the ?uid solids technique 50 ?ed with steam and oxygen, by the addition to wherein the carbonaceous charge is reacted in the generator of small proportions of a halide the form of a dense turbulent mass of ?nely di which at the reaction conditions’ yields halogen vided solids ?uidized by ‘the ‘gaseous reactants and/or a volatile halogen compound.” and products. . Heat is generated either by par , 'Alkali metal halides, such as the chlorides, bro tial combustion of carbonaceous materials within 65 mides, and ?uorides of sodium, potassium, vlith 2,672,410 3 4 ium, rubidium, and cesium, or mixtures of such ~ control the Hz/CO consumption ratio of the syn halides are particularly suitable for the purposes thesis reaction. of the invention, but alkaline earth metal halides, The process of the invention may be carried such as those of barium, calcium, and magnesium, out in any system wherein carbonaceous solids may also be used. Sodium chloride, because of are reacted with steam and oxygen to produce its ready availability and low cost, is the preferred gas mixtures of the type of water gas. Any con~ addition agent. Proportions of about 0.01—5%, ventional gas generator working on this principle preferably about 0.05-l%, ‘by weight of alkali may be adapted for the purposes of the invention, metal halide based on carbon supplied to the independent of the special technique involved, i. e. generator, are suitable to depress C02 forma 10 the essential advantages of the invention may be tion from about 15-20% to less than about 5% realized in ?xed bed, moving bed, ?uid bed or of the product gas. true suspension operation. However, ?uid opera While it is not intended to limit the present tion is preferred, because of its superior charac invention by any theory of the reaction mecha teristics of gas-solids and solids-solids contact nism involved, it is believed that the effect of 15 and its improved heat transfer characteristics, the addition of halides may be explained as fol which greatly enhance the inhibiting and cata lows. Alkali metal halides, such as NaCl, react lytic effects of the addition agents of the inven with steam in the presence of oxygen at the gas tion. A system of this preferred type is illus generation temperatures of about 1800°-2000° F., trated in the drawing, the single ?gure of which to yield free halogen and/or hydrogen halide and 20 depicts schematically an expanded flow plan of alkali metal oxide and carbonate. Small amounts the process. _ of halogen or volatile halogen compounds are Referring now to the drawing, the system shown known to suppress the formation of CO2 in favor consists essentially of a conventional ?uid-type of an exclusive formation of CO in the combus water gas generator [0 and metal halide recover tion of carbonaceous materials. Since CO2 for- - ing equipment 30 and 40, the functions and coop mation in the water gas generator is largely due eration of which will be forthwith described using to a complete combustion of carbon to CO2, the the gasi?cation of a low temperature coke in the halogen or halogen halide supplied by the alkali presence of NaCl as an example. It should be metal halide will act to suppress CO2 formation understood, however, that the system may be op in the water gas reaction. 30 erated in a similar manner for the gasi?cation of It will be appreciated from the foregoing that other carbonaceous solids, such as various coals, the addition of halides in accordance with the in the presence of other suitable halides. invention has nothing in common, regarding its In operation, fresh coke ground to a particle purpose and effect, with the known addition of size passing 4 mesh with a major proportion such agents catalyzing the water gas reaction as passing 60 mesh is fed from a feed hopper, pref alkali metal carbonates, nickel, heavy metal erably a lock hopper I, into a standpipe or other oxides or sul?des, etc., or mixtures thereof which conveying means 3 into generator Ill. The coke have no inhibiting effect on the formation of 00:. may be preheated to temperatures of about 400° It is, however, a particular advantage of the 800° F. in hopper I by means of product gases present invention that such catalytic agents as passed therethrough via lines 6 and 8, or in any alkali metal oxides or carbonates are formed as other conventional means. Sea water is intro the solid residue of the liberation of halogen or duced through line 5 into standpipe 3 in amounts hydrogen halide. As a result of this secondary su?icient to introduce about 0.054% by weight catalytic eiiect, the gasi?cation temperature may of NaCl, based on carbon, into the coke. About be substantially reduced and the 00 content of 25-100 gals. of sea water per ton of coke passing the product gas considerably increased. The through standpipe 3 are normally adequate for latter effect is due mainly to an acceleration of this purpose. If the coal is preheated as de the reaction scribed, the sea water evaporates quickly in the standpipe and the steam so generated acts as an aerating agent. which may be very appreciable at NazCOa con Simultaneously, a mixture of steam and Oz in centrations as low as 0.01%, as has been shown a ratio of about 700-1800 lbs. of steam per 1000 by other researchers. cu. ft. of O2 is supplied from lines 12 and M, In accordance with the preferred embodiment respectively, through a distributing device such of the invention, the alkali metal halide to be 55 as grid 16. About 1000-1500 cu. ft. of oxygen and added is introduced into the gas generator by about 700-2400 lbs. of steam per ton of coke are the injection of, or the impregnation of the car normally su?icient to support the water gas reac bonaceous charge with natural brines containing tion in the presence of NaCl at temperatures of the desired halide, for example sea water. The about 1'700°—1800° F. In the absence of NaCl, the alkali metal oxide or carbonate remaining on the 60 steam and oxygen consumption are somewhat gasi?cation residue may be recovered as the higher for the production of a gas of comparable corresponding hydroxide or carbonate by an aque composition, and the process is much more sensi ous extraction of the gasi?cation residue. The tive to variations in the concentration of these aqueous extract may be used as a scrubbing solu reactants than one employing the alkali halide tion to remove any excess halogen from the prod additive. Reactor [0 should be so designed that uct gases, if desirable. The halide salt content at the solids and gas feed rates involved a linear of the used scrubbing solution may be reutilized super?cial gas velocity of about 0.5-1.5 ft. per in the process as a carrier of alkali metal halide second is maintained in reactor l0, at which its to be added to the generator in accordance with contents are converted into a highly turbulent the basic principle of the invention. In some 70 ?uidized mass M10 having an upper interface L10 cases, it may also be desirable to pass a certain ' ' and an apparent density of about 20-40lbs. per quantity of halogen with the gas produced to a cu. ft. - synthesis stage in order to promote a selectivity _. A dilute solids-in-gas suspension is withdrawn more favorable to certain desired products, in- ’ overhead from level L10 and passed through a creased unsaturation of synthetic products. 01‘ t0 7.5 gas-solids separator, such as cyclone it, from 79,819,410 "6 which Separated ?nes may beretul'ned to ‘mass treated with ‘anaqueousmedlum dissolving com M10 via glipspipe go, Product gas {substantially pounds of the cation of said halide-to iorma so free of solids is withdrawn, through line 22. ‘This lution enrichedin said compound. ,gas, at the conditions spec v “d may haves cem .8.‘ The method 1of. claim 7 which said gas pcsitign about-as follows: mixture isscrubbedwith said solution to remove Volspercent at lea-eta substantial portion of itscontent in H2 _--__=: ______“A0 to 45 halogen . and volatile .ha‘logen compounds from said gas mixture and to form .saidhalide in said. solution. Total Cl (free and combined) ______<0.5 10 ;9. The process of claim 8, in which the halide

N2 ------‘?-..-.'1l—.'.--—.------'-. termed in. said solution isv introduced into said gtbfir‘iulpurities T-Tg zone. _ 10. The. process of claim linlwhich said halide Any desired BQl'?QQ-Q? the intellect gas may be is an alkaline earth metal» halide. heat exchanged. with case soccer ,1 via Y 11. The ‘process of claim 10- in which said lines 6 and '8 as above described. The ‘total gas halide is selected from the group consisting of e?luent in line 22 may then be further cooled in theihalidesof barium, calcium and magnesium. heat exchange with feed. gases and/or other 12. In the production of gas mixtures contain media in a heat exchange and cooling system 24 ing Hz and CO by reacting solid carbonaceous to be passed through line 26 to a scrubber 30 at materials with steam and oxygen in a gasi?cation a temperature of about 60° to 200° F. zone at gasi?cation conditions, the improvement Returning now to generator l0, solid gasi?ca which comprises contacting said steam and oxy tion residue is withdrawn through line 35 and gen simultaneously at said conditions in said passed to an extractor 40. Sea water may be zone adding to said zone an extraneous metal supplied through line 42 to extractor 40 in 25 halide forming at said conditions a. reaction amounts adequate to extract the soda content of product selected from the group consisting of ele the ash. All or part of the sea water to be sup mental halogen and volatile halogen compounds, plied to line 5 may be used for this purpose. Ex with a dense turbulent mass of subdivided carbo tracted ash may be discarded via line 44. En naceous solids ?uidized by upwardly ?owing gases riched sea water is passed through line 46 to 30 to resemble a boiling liquid, said halide being scrubber 30 wherein it is used to remove chlorine present in amounts providing a halogen equiva and its compounds from the product gas in a lent corresponding to that of about 0.0l—1% by manner obvious to those skilled in the art. Sea weight of alkali metal halide based on carbon water which may now contain NaCl somewhat present and said amounts being adequate to in above its normal concentration may be returned hibit the formation of CO2 in favor of CO forma via line 48 to feed line 5. The product gas re tion. covered from scrubber 30 through line 50 is now 13. In the production 01’ gas mixtures con substantially free of halogen and is ready as a taining H2 and CO by reacting solid carbona feed gas to ya conventional hydrocarbon syn ceous materials simultaneously with steam and thesis or other hydrogenation unit, if desired 40 oxygen in a gasi?cation zone at gasi?cation con after further desulfurization by conventional ditions, the improvement which comprises con means. However, scrubber 38 may also be so op tacting said steam and oxygen at said condi erated that a substantial proportion of the sulfur tions in said zone with a dense turbulent mass content of the product gas is absorbed therein. of subdivided carbonaceous solids ?uidized by up The above description and exemplary opera- ~ ?owing gases to resemble a boiling liquid and tions have served to illustrate speci?c embodi adding to said mass a natural metal halide brine ments of the invention but are not intended to containing a halide forming at said conditions a be limiting in scope. reaction product selected from the group con What is claimed is: sisting of elemental halogen and volatile halogen 1. In the production of gas mixtures contain- _. compounds, said metal halide being present in ing H2 and CO by reacting solid carbonaceous amounts providing a halogen equivalent corre materials simultaneously with steam and oxygen sponding to that of about 0.01-1% by weight of in a gasi?oation zone, the improvement which alkali metal halide based on carbon present and comprises adding to said reaction an extraneous said amounts being adequate to inhibit the for metal halide yielding a reaction product selected , mation of CO2 in favor of CO formation. from the group consisting of elemental halogen 14. The process of claim 13 in which said brine and volatile halogen compounds at the reaction comprises sea water. conditions said halide being present in amounts 15. In the production of gas mixtures con providing a halogen equivalent corresponding to taining H2 and CO by reacting solid carbona that of about 0.01-1% by weight of alkali metal (30 ceous materials simultaneously with steam and halide based on carbon present and said amounts oxygen in a gasi?cation zone at gasi?cation con being adequate to inhibit the formation of CO2 ditions, the improvement which comprises im in favor of CO formation. pregnating subdivided carbonaceous solids of 2. The process of claim 1 in which said halide ?uidizable particle size with sea water of enriched is an alkali metal halide. CD GI metal halide content, said metal halide forming 3. The process of claim 2 in which said halide at said conditions a reaction product selected is sodium chloride. from the group consisting of elemental halogen 4. The process of claim 1 in which said halide and volatile halogen compounds, said metal is added to said materials prior to said reaction. halide being present in amounts providing a 5. The process of claim a in which said halide 70 halogen equivalent corresponding to that of is added in the form of a natural halide brine. about 0.01-l% by weight of alkali metal halide 6. The process of claim 5 in which said'brine based on carbon present, said amounts being comprises sea water. ‘1 adequate to inhibit the formation of CO2 in 7. The process of claim 1 in which solid gasi? favor of CO formation contacting said impreg cation residue withdrawn from said zone is ex nated solids with steam and oxygen at said con ~ 2,672,410 7 ditions in said zone in the form of a dense tur References Cited in' the ?le of this patent bulent mass of solids ?uidized by upwardly ?ow ing gases, withdrawing a product gas contain UNITED STATES PATENTS ing volatile halogen compound and free halogen Number Name Date from said zone, separately withdrawing solid 5 649,550 Rowland ______I____ May 15, 1900 gasi?cation residue from said zone, leaching said 1,948,085 White et a1. ______Feb. 20, 1934 residue with sea water to extract soluble alkali 2,187,872 Winkler et al ______Jan. 23, 1940 and alkaline earth metal compounds and to pro 2,527,846 Phinney et a1 ______Oct. 31, 1950 duce sea water enriched in said last-named com 2,533,666 Gunness ______Dec. 12, 1950 pounds, scrubbing said product gas with said last 10 FOREIGN PATENTS named enriched sea water to extract volatile halogen compounds and free halogen from said Number Country Date product gas and to produce said sea water of en 606,321 Great Britain ______Aug. 11, 1948 riched metal halide content, and using said last OTHER REFERENCES named sea water for said impregnating treat- 15 Grant: “Hackh’s Chemical Dictionary.” 3rd ment. edition, page 685. WILLIAM J. MATTOX.

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