US2640034A - Production of mixtures of carbon monoxide and hydrogen - Google Patents

Description

May 26, 1953 M C Kl JONES 2,640,034

I PRODUCTION OF MIXTURES OF CARBON MONOXIDE AND HYDROGEN- Filed June 4, 1946 minar' @.K. Jones 'avenbor D 'bl M CLbborneg,

Patented May 26, 1953 PRODUCTION OF MIXTURES OF CARBON MONOXIDE AND HYDROGEN Minor C. K. Jones, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application June 4, 1946, Serial No. 674,255

4 Claims. 1

The present invention relates to the production of combustible gases from solid carbonaceous materials. Moreparticularly, the invention is concerned with the conversion of solid carbonaceous materials such as coal, coke from coal or petroleum, peat, tar sands, oil shale, cellulosic materials, etc., into gas mixtures useful in the catalytic synthesis of hydrocarbons from carbon monoxide and hydrogen.

The use of solid fuels such as coal, coke, oil shale, or the like as plentiful and inexpensive starting materials for the catalytic synthesis of hydrocarbons from carbon monoxide and hydrogen has been the object of extensive research work in recent years. The ultimate aim of these studies is a process which permits the continuous and substantially complete conversion of the carbon available in the solid starting material into suitable mixtures of carbon monoxide and hydrogen and heat required by this conversion. All prior art processes of which I am aware have fallen short of accomplishing this result. The conventional water-gas processes provide for a conversion of solid fuels with steam into socalled blue water gas by blowing steam and air and/or oxygen simultaneously or alternately through a fixed bed of the solid starting material. These processes require frequent cleaning periods resulting in discontinuous operation or they involve incomplete conversion of the available carbon into water gas and heat. The operation` may be made fully continuous by employing the so-called fluid solids technique in which the reactions take place in a dense iiuidized bed of finely divided solids maintained in a turbulent ebullient state by means of iiuidizing gases. 'Ihis technique has highly Idesirable additional advantages such as greatly improved heat distribution and ease of solids handling,

In accordance with a more recent development of the latter technique the heat required by the gasification reaction is supplied in the form of sensible heat of solid combustion residues circulated to the heat-consuming reaction from a zone wherein solid carbonaceous material such as solid carbonaceous gasification residue is subjected to combustion. In this manner, the gasication aone and product may be kept entirely free of combustion products and diluting gases such as nitrogen. However, aside from the factl that large quantities of heat are wasted as-'sensible heat of the volatile products of gasification and combustion this process yields hydrogen and carbon monoxide in the substantially xed ratio of about l to 1.3 moles of hydrogen per l mole of carbon monoxide while the synthesis of hydrocarbons usually requires a feed gas having a considerably greater hydrogen content of about 2 or more moles of hydrogen per mole of carbon monoxide. Therefore, it has been necessary heretofore to enrich the water gas obtained from solid fuels with hydrogen produced in a separate and 2 thermally independent process, either electrolytically or by the reduction of steam or by other means adding considerably to the investment and operating cost of synthesis gas manufacture.

The present invention overcomes the aforementioned drawbacks and affords various additional advantages, These advantages, the nature of the invention, and the manner in which it is carried out will be fully understood from the following description thereof, read with reference to the drawing which gives a semi-diagrammatic View of a system particularly adapted to carry out the invention.

It is an important object of my invention to provide an improved process for the conversion of finely divided solid carbonaceous materials into combustible gases.

Another object of my invention is to provide a process for continuously converting finely divided solid carbonaceous materials into combustible gases comprising mixtures of carbon monoxide and hydrogen of suitable composition for the catalytic synthesis of hydrocarbons.

Other objects and advantages of my invention will appear hereinafter.

I have found that mixtures of hydrogen and carbon monoxide containing more than about one mole of hydrogen per mole of carbon monoxide may be produced from solid carbonaceous materials in an economical manner when heat and reducing gases generated in the manufacture of blue water gas are utilized for the production of make-up hydrogen by the reduction of steam. In accordance with my invention carbonaceous solids are reacted with steam to form blue water gas, heat required for this endothermic reaction being generated by the combustion of carbonaceous solids in a separate heating zone operated to produce substantial amounts of carbon monoxide Which is used in the reduction of steam to produce make-up hydrogen. For the latter purpose, I prefer to contact steam with a reducing metal such as iron or alloys thereof with activitycontrolling metals such as manganese, tungsten, or the like to form hydrogen and metal oxide and to regenerate the metal by reducing the metal oxide with the carbon monoxide produced in the heating zone of the water gas manufacture.

By employing the uid solids technique my process may be operated in a fully continuous manner and all the heat required for the endothermic water gas and hydrogen producing stages may be generated in and recovered from other stages of the process. More specifically, I prefer to use both the carbonaceous solids and the reducing metal in the form of dense iluidized beds of finely divided solids maintained in Water gas and hydrogen generation zones, respectively, to supply the heat to the wate gas generation as sensible heat of solid combustion residue from a separate fluid solids burner producing carbon monoxide, and to supply at least a portion .of the heat 'required for the lhydrogen generation as sensible heat of reducing metal withdrawn from a separate heat-generating fluidized regeneration zone wherein the metal oxide formed in the hydrogen generation zone ris :reduced by means of the carbon monoxidepro'duced in the burner. Additionalheat may be supplied to the hydrogen producing `system 'as sensible heat of the carbon monoxide produced vat high temperatures in the burner and as sensible heat of the water gas produced in "-the ywater gas'generation zone. The rate of hydrogenfproduction may be controlled by controlling the rate of addition of reducing metal and steam to the hydrogen generationzone. 'Inthis manner, all heat generated in the Vprocess and available in the various streams of gases and solids'is fully utilized for the 'purposes of my process, the only materials to be rejected from the vprocess being the products of complete combustion, that is, completely burned'ilue gas withdrawn from the metal regeneration zone and ash which vmay be withdrawn from any suitable portion of rthe water gas producing section of the system.

The conditions of temperature and pressure may vary within wide limits depending on the character of the carbonaceous solids used, the type of reducing Imetal'employed and the cornposition of the 'product gas desired. In general, the water gas generation zone'may be maintained at a temperature of about l4002400 F., preferably about 16001800 F. at burner temperatures of about l6002500 preferably about 1`8001900 F. vfor an air-fuel ratio appreciably less than that required for complete combustion of the available carbon. lThe temperature of the hydrogen generation and metal `regeneration'zonesfmay fall vwithin the approximate ranges of about 60021200 F., preferably '70'0-1100 and about 12001700 F., preferably about 1300`1500 respectively. Pressures ranging from subatmospheric to about200 'lbs/sq. in. may be applied in any or all of the treating zones. However, the pressure is preferably so adjusted that the final product gas -leaves the system at the pressure at which it is used inthe yhydrocarbon synthesis.

Having set forth the general nature and ob- `jects,the invention will be best understood from the subsequentmore detailed description in which `reference will be made to the accompanying drawing whichillustrates Aa system suitable for carrying outa preferred embodiment of the invention.

The system'shown inthe drawing 'essentially comprises a water v'gas generator I0, a heater burner 20, a hydrogen generator 60 and a metal regenerator 40. The function and manner of cooperation of these yelements will be presently explained using coke as an example fora suitable initial carbonaceous solid and iron as an exmple for a reducing metal. It should be understood, however, that other carbonaceous starting materials and reducing metals may be used in an analogous mamier.

Referring now in detail to the drawing, coke ground by any conventional means (not shown) to a iluidizable particle size, for example of the order of 50% having a size of 'less than 100'mesh, althoughsmall lumps of up to 1A; or 1/2 inch size may be used, is fed lin any manner known per se to feed 'hopper I. An aerating gas, such as `ilue gas, steam or the like, may be supplied through line 3 to maintain the coke in .hopper I in the form of a vdense iluidized mass flowing like a liquid .through lducts and valves. The fluidized coke flows through pipe 4 carrying control valve 5, into pipe 1. The flow of solids through pipe 4 may be further facilitated by the 'addition'pfiaeratin'g gas from line 3 as indicated. In'line 1,`the coke is picked up by a stream of steam to form a suspension of lower density which .is passed .under the `pseudo-hydrostatic pressure of column 4 .to the lower portion of water gas generator I 0 which it enters through a perforated :distribution/.device 9. The water gas generator is maintained at a temperature of about 1600"- 1800 F. and a pressure of preferably about 30 lbs/sq. in. to permit ithe water gas reaction to take placebetweenthe steam andthe coke. 'Ihe superficial velocity ofthe steam is so controlled that the coke forms a dense turbulent mass I2 iluidized'by the steam andthe water gas formed and'having a well de'ned upper level I3. Supercial gas'velocities of about v0.345 "ft, per second are generally adequate for this purpose. The amount of steam supplied per pound of coke is preferably less than that 4required to convert the entire amount of ycarbon available into water gas andthe contact time is preferably so controlled 'that 'about `5-30% of carbon remains unconverted. The 'heat required for the water gas Yreaction is supplied "by'highly'heated solid combustion residue recirculated from `heater-burner "2 llas will'appearmore clearly hereinafter. Blue water gaslconsisting substantially o'f 'hydrogen Vand carbon vmonoxide in the approximate volumetric ratio of about 5:4 is 'Withdrawn 'overhead 'from `the dense lphase I2, through a 'conventional gas-solids separator II of the electrical and/or centrifugal type, provided with 'a vsolids return pipe Iand 'from here through lines I6, v'and T3 toany desired further treatment.

Fluidized solid carbonaoeous'gasification residue is Withdrawn downwardly from zone I2 `through'vertical pipe f5 aerated through lines I'I, and passed through control valve I8 into'line I9 where `it is 'picked up by an'oxidizing gas such as air and/or oxygen to form a suspension of 10W *density which is passedunder the pseudo-hydrostatic pressure of 'standpipe I 5 and substantially at the temperature of gasification zone I2 tothe =lower portion of heater-burner 20 which it enters through a distributing device 2I. The oxidizing gas supplied to line I9 -may be preheated vto temperatures of about 1`2001500 F., particularly during'the starting period. The air-fuel ratio is preferably so controlled that about 3 to 30cu. `1't. of oxygen is supplied per pound of carbon burned to yield by partial combustion a producer gas containing about 25-35% `o'f carbon monoxide and about 3-1'0% of carbon dioxide at a heater temperature of about 18001900 F. and a pressure of about 30 lbs/sq. in. If desired, steam, say up to about 20%, may be added to the oxidizing gas, in .which case the producergas will contain about lil-15% of hydrogen in addition to the carbon monoxide. The superficial velocity of the gas owing .upwardly through heater-burner "20 iS maintained between about 0.3 and l0 ft. per second, preferably Ain the'neighborhood of about 1.5 ft. per second to establish a dense iluidized solids .phase 22 lhaving an upper level 23, similar todense phase I2 in generator I0. Fluidized solid combustion residue passes downwardly from zone 22 'through pipe 25aerated through line 2l yand provided vwith control valve 29 to enter pipe 1 and to 'form therein a dilute suspension in steam, which is passed .under `the pseudo-hydrostatic .pressure of standpipe 25 and substantially -at the temperature of zone 22 to Water gas generator l0 to supply the heat required therein. The amount f I f vary between the approximate limits of 30 to 300 times the carbon content of the fresh carbonaceous feed depending on the temperature difference between phases 22 and I2 and is preferably so controlled that levels I3 and 23 are maintained substantially constant.

Producer gas of the `composition mentioned above passes upwardly from zone 22 through the free space 3l above level 23 wherein a substantial portion of entrained solids drops out, and then, if desired, through a conventional gas-solids separator 33 from which separated solids fines may be returned to dense phase 22 through line 35. Producer gas substantially freefof solids passes through line 31 where it picks up finely divided oxidized iron of the approximate average composition of FezOi withdrawn from hydrogen generator 60 through line 65 as will appear more clearly hereinafter, and the dilute suspension formed enters the lower section of metal regenerator 4U through a distributing device 39, to form in regenerator 40 a dense iiuidized solids phase 42 having i an upper level 43, similar to phases l2 and 22.

The temperature of dense phase 42 is maintained at about 13001600 F. to cause substantial reduction of the iron oxide by the producer gas to metallic iron. Since this reaction is exothermic it may be desirable to withdraw heat by any conventional means such as a cooling coil 44. The particle size of the iron oxide which may be Supplied to regenerator 40 by any means known per se such as screw conveyor 45 before starting up the process, is preferably somewhat smaller than that of the carbonaceous feed and may fall within the approximate range of 150-300 mesh to establish proper iiuidization at gas flow conditions similar to those outlined in connection with chambers I0 and 20. Flue gas practically free of combustible constituents is withdrawn overhead from dense phase 42, passed through a conventional gas-solids separator 41 provided with solids return line 49, and leaves the system through line 50 either to be vented or to be used for preheating and/or aeration purposes in the system.

Solid fluidized reduced iron passes downwardly from dense phase 42 through standpipe 5I provided with control valve 53 and enters line 55 where it is suspended in steam and passed to the lower section of hydrogen generator 60 through a distributing device 51. The conditions of gas and solids flow to hydrogen generator B0 are s0 controlled that a dense iiuidized solids phase 62 having an upper level 63 is formed therein and kept at a steam reducing temperature of about '750-1100 F. to form the desired amount of hydrogen. I-Ieat required for this reaction may be supplied as sensible heat of the reduced metal from the high temperature zone 42. In general, solid circulation rates of about 0.1 to lbs. of reduced metal per cu. ft.- of steam dependingon the temperature difference between phases 42 and 62 are suitable for this purpose. Solid fluidized oxidized iron is withdrawn downwardly from zone 62 through pipe 65 carrying control valve 61 and passed into line 31v and regenerator 40 as outlined above.

Hydrogen which may contain some unconverted steam passes overhead from zone 62, is

`freed of entrained solids in conventional separator 69 provided with solids return pipe 1I, and is withdrawn through line 13 wherein it may be mixed with blue water gas supplied from water gas generator I0 by way of lines I6 and 15, t0 establish the desired ratio of hydrogen and carbon monoxide in the final synthesis gas mixture.

The embodiment of my invention illustrated by the drawing permits of numerous modifications. For example, heat may be supplied to generator l0 by a partial combustion of carbonaceous material within generator I0 by the direct supply of relatively small amounts of an oxidizing gas in such a manner as to maintain overall reducing conditions in generator l0. The conditions of temperature, steamand oxygen supply in generator I may also be so controlled as to produce predominantly carbon monoxide. Hydrogencontaining solid lines may be used in place of coke, or hydrogen-containing solid, liquid and/or gaseous fuels may be introduced into heaterburner 20 to enrich the producer gas with hydrogen, if desired. Part or all of the water-gas produced in generator l0 may be introduced through line 11 into the hydrogen generator 60 to reduce iron circulation and to supply additional heat as sensible heat of the water-gas and/or heat of the reaction between its components and metal oxide formed in zone 62. Instead of feeding solids to the bottom of chambers l0, 20, 40 and 60 by means of a carrier gas any other conventional means of conveying fluidized solids such as pressurized feed hoppers, mechanical conveyors, etc. may be used. Means for the removal of ash may be provided at any suitable point of the solids cycle of the water-gas producing system. For instance, separator il may be operated in stages so that light ash may be rejected through line 19. It will be understood that the operation of the entire system may be made fully continuous by continuously feeding solid and gaseous starting materials, maintaining a continuous solids circulation and withdrawing continuously water-gas, hydrogen, flue gas and ash from the system. Other modifications and variations within the scope of my invention will appear to those skilled in the art.

My invention will be further illustrated by the following specic example.

EXAMPLE The following conditions of my process have been found useful for manufacturing 100,000 C. F./hr. of gas containing two moles of hydrogen per mole of carbon monoxide.

Operation of waterr gas generator and heater burner Water Gas Generator Heater Burner Operating Conditions:

Feed Coke Containing meedoet "(Dperlztz'an 'of .hydrogen .generator fand metal o'egenerator :Hydrogen Metal 'RegfGenerator, generator '.OperatingConditiorls:

Temperature, F -Pressurep sti/g. 1:# xFe -Rcacting/l'lr.4 Vi# F0304 vto Reduce/hr.

steam Addeuwhr 1,1350

Geel-leaving Vesscl,-C -F./hr l 100, 0005 .82,000 Gas Composition Leaving Vessel *A fee 33 N11 EL... 6s Nil 'Oz I 1 While 'the 'foregoing description and exemplary operations '-have served to illustrate specific applications and results of my invention, other modifications lobvious to .those skilled Ain v.the art are Within the scope of my invention. Only such ylimitations Ashould .be imposed on my invention as `are vindicated in ,the .appended claims.

Ifclaim:

1. .The continuous ,process fof 4producing mixtures lof hydrogen fand carbon `monoxide serving :as ieedga's to ahydrocarben ysynthesis process and containing rcontrolled molecular' proportions 'of hydrogen vfrom lsolid 'carbonaceous materials vand -stea-m which-comprises continuously `feeding yfresh finely 'divided :carbonaceous solids -to a heated v/atergasfgeneration Zone, subjecting said finely dividedsolid carbonaceous material, :in the form-(of a dense, turbulent `bedtoffsolids fiuidized -by an :upwardly flowing gas fand resembling a :boiling fliquid having a well defined upper level, toa -Waterzgas reactionWith-steam in said zone :to1.p1odu'ce;afhotstreamiof'water gas, continu- -ously circulating fsolid carbonaceous residue of the YWater gas reactionto afheating.zone'and.subjecting itfthereinin rthe formoffa-similarly 'fluid- :ized bed of solids to incomplete'combustion with lair and-steam .to tpreduce afhot Acombustible gas containing about to `35% -of car-bon monkoxide 'and about .16% to 15% hydrogen, continuously supplying a part of :the heat Egenerated by said combustion to said Water gas reaction in the form of sensible heat of solid combustion residue returned from "sai'd'heating zone to said water gas generation. zone, continuously subject- 'ing steam to a reducing Atreatment at a steam reducing "temperature with a 'finely divided reduced 'metal 4oxide ,maintained in `a similarly uidized bed of solids to Aform 'hydrogen and finely divided metal oxide, continuously regenerating said reduced .metal-.oxdein -aseparate `regeneration zone by reducing said metal oxide in a similarly uidized bed of solids heated to a temperature higher than said steam reducing .'30 temperature by said hot combustible gas and reduced ithereby producing a completely burned vent gas substantially free of carbon 'monoxide continuously lsupplying to said steam reducing treatment at least 'apart -of 'said hot water gas together with reducedrmetal-oxide from said regenerating zone substantiallyfat said higher temperature, controlling the molecular ratio fof hydrogen to carbonmonoxide in the gas from -said -steam reducing treatment by controlling the f7.0

amounts .of hot water gas and steam fed thereto together With said reduced metal-oxide, mixing said gas with any remaining watergas by-passing vthe steam reducing-treatment, and recovering the V.hydrogenenriched-mixture.

2. The process-as claimed inclaim 1 -in which :said metal 4is iron and said metal oxide approximates the .composition FeaOl.

3. The .process as claimed in 4claim 1 `in which rasmall amount of -steam is added to said 'oxidizingigas.

14. The lcontinuous `:process of producing .mixtures Iof :hydrogen and carbon monoxide serving @as feed gas to a hydrocarbon synthesis lprocess and containing more than equimolecular proportions Aof :hydrogen from solid carbonaceous vmaterials Aand steam which comprises continuously feeding fresh finely divided carbonaceous solids :tofa heated vwater gas generation'zone, subjecting said finely divided solid carbonaceous material, in the dorm lof a dense turbulent bed 4of solids Tuidized by an upwardly flowing gas and resembling a boiling liquid having a well dened upper level, to a water gas reaction -with steam in said'zone to produce a Ihot stream of waterigs, continuously circulating solid 'carbonaceous resi- `dueof the Water gas reaction to a vheating zone Aand subjecting it therein in the form of a Vsimilarly fluidized 'bed of solids to incomplete lcombustion withair andsteam to produce a hot'combustible gas containing about 25% -to 35% of fcarbon monoxide and 'about 10% to 15% of hydrogen, continuously supplying a `part of the heat generated by'said combustion to said 'water .gas reaction inthe form of .sensible heat of solid combustion 'residue returned from said `heating zone'to said water gas Ageneration zone, 'continuously subjecting steam to a reducing treatment at a steam Yreducing .temperature with a finely divided reduced metal oxide maintained in fa similarly iluidized rb'edfof solids to form hydrogen and finely divided metal oxide, 'continuously 'regenerating said reduced metal oxide in a separate regeneration Azone by reducing'said metal oxide in a similarly fluidized 'bed of solids heated to 'a temperature higher than said steam reducing tempera-ture by -said `hot combustible :gas and vreduced thereby producing a completely burned ventgas substantially free of carbon monoxide, 'continuously supplying hot reduced ymetal oxide from said regenerating zone to said steam reducing treatment substantially at said higher 'temperature passing 'at least a portion of 'said hot water gas into said hydrogen generation lzone -to supply fadditional heat for said steam-reduc- .ing treatment, mixing said water Agas and said hydrogen, and recovering the hydrogen-enriched mixture.

MINOR C. K. JONES.

References Cited fin the file of this patent 'UNITED STATES PATENTS Number Name Date 2,198,560 Marshall, Jr. Apr. 23, 1940 y2,436,933 Scharmann et al. Mar. 2, `1948 2,449,635 Barr Sept. 21, 1948 42,482,187 Johnson Sept. 20, 1949 2,579,398 -Roetheli Dec. y18, 1951 FOREIGN PATENTS --Number Country Date 220,676 Great vBritain Aug. 21, 1924 v112,360 :Switzerland Nov. I2, l1925 632,466 France Oct. 10, 1927 `.OTHER REFERENCES -'lvaylorgndustrial Hydrogen, 1921, The Chemi-

Claims (1)

1. THE CONTINUOUS PROCESS FOR PRODUCING MIXTURES OF HYDROGEN AND CARBON MONOXIDE SERVING AS FEED GAS TO A HYDROCARBON SYNTHESIS PROCESS AND CONTAINING CONTROLLED MOLECULAR PROPORTIONS OF HYDROGEN FROM SOLID CARBONACEOUS MATERIALS AND STEAM WHICH COMPRISES CONTINUOUSLY FEEDING FRESH FINELY DIVIDED CARBONACEOUS SOLIDS TO A HEATED WATER GAS GENERATION ZONE, SUBJECTING SAID FINELY DIVIDED SOLID CARBONACEOUS MATERIAL, IN THE FORM OF A DENSE, TURBULENT BED OF SOLIDS FLUIDIZED BY AN UPWARDLY FLOWING GAS AND RESEMBLING A BOILING LIQUID HAVING A WELL DEFINED UPPER LEVEL, TO A WATER GAS REACTION WITH STEAM IN SAID ZONE TO PRODUCE A HOT STREAM OF WATER GAS, CONTINUOUSLY CIRCULATING SOLID CARBONACEOUS RESIDUE OF THE WATER GAS REACTION TO A HEATING ZONE AND SUBJECTING IT THEREIN IN THE FORM OF A SIMILARLY FLUIDIZED BED OF SOLIDS TO INCOMPLETE COMBUSTION WITH AIR AND STEAM TO PRODUCE A HOT COMBUSTIBLE WITH CONTAINING ABOUT 25% TO 35% OF CARBON MONOXIDE AND ABOUT 10% TO 15% HYDROGEN, CONTINUOUSLY SUPPLYING A PART OF THE HEAT GENERATED BY SAID COMBUSTION TO SAID WATER GAS REACTION IN THE FORM OF SENSIBLE HEAT SOLID COMBUSTION RESIDUE RETURNED FROM SAID HEATING ZONE TO SAID WATER GAS GENERATION ZONE, CONTINUOUSLY SUBJECTING STEAM TO A REDUCING TREATMENT AT A STEAM REDUCING TEMPERATURE WITH A FINELY DIVIDED REDUCED METAL OXIDE MAINTAINED IN A SIMILARLY FLUIDIZED BED OF SOLIDS TO FORM HYDROGEN AND FINELY DIVIDED METAL OXIDE, CONTINUOUSLY REGENERATING SAID REDUCED METAL OXIDE IN A SEPARATE RE-

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