US2657124A - Generation of heating gas from solid fuels - Google Patents

Description

Oct. 27, 1953 l.. P. GAUCHER 2,657,124

GENERATION OF HEATING @As FROM SOLID FUELS Filed Dec. 5o. 1948 C OAL T/Ws, o/ AND SOL/D5' IN V EN TOR.

91T TOEN E YS* Patented Oct. 27, 1953 UNITED STATES PATENT OFFICE GENERATION F HEATING GAS FROM SOLID FUELS Leon P. Gaucher, Mount Vernon, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application December 30, 1948, Serial No. 68,27 0

(4) Preferably the process should use iine coal as feed since there is `a large accumulationof useless fines in existing coal fields. It is re ported that in Pennsylvania alone there are of gas of high heating value from a solid car- 5 200,000,000 tons of anthracite silt accumulated bonaceous fuel. and that this by-product of anthracite -mining The process of this invention is applicable to is now being produced at the rate of about the treatment of solid carbonaceous materials 5,000,000 tons per year. In any event, it is of various types and grades, for example, ancheaper to mine coal mechanically if a large thracite, bituminous coals, lignite and oil shale. percentage of fines can be tolerated. The process of this invention is particularly suit- (5) The investment must not be too great and able for the gasification of soft coals, waste coals, the operating manpower requirement must be caking coals, anthracite silt, lignite, or the like. small. The operating and maintenance costs Petroleum hydrocarbons, including natural gas, must be small. refinery gases and fuel oil, are inherently better To meet these requirements is a primary obsuited as the starting materials for the producject of the present invention. tion of natural `and synthetic locomotion fuel The complete gasification of coal with oxygen and lubricating oils than any other conceivable at high thermal efficiency can produce a gas feed, At the present time, however, almost half having a heating value of about 400 to `450 of the current production of this valuable nat- B. t. u.s per cubic foot. A product gas of higher ural resource is being burned as heating fuel or heating value may be obtained by enriching the for power generation. coal gas with light hydrocarbons of high heating This situation exists because oil and natural value. Methane, for example, has a heating gas are easy to handle and burn; they can be value of 1012 B. t. u.s per cubicfoot; ethane, transported by pipe lines; the oil can be stored; 1,762 B. t. u.s per cubic foot; and propane, 2,509 and in most instances both oil and gas are readily B. t. u.s per cubic foot. These lighthydrocaravailable at prices competitive with solid coal or Ibon gases may be supplied to the coal gas by manufactured gas. cracking within the coal gasification apparatus Petroleum hydrocarbons would not be so exwhich inevitably is operated at a very high terntensively used for heating if coal could be ecoperature, a heavy, less desirable petroleum fracnomically converted to a gas of high heating tion, such as crude residuum. value and distributed as fuel gas at a price some- An important object of the present invention what less than the cost of petroleum hydrois to provide an improved method and apparatus carbons. It follows, therefore, that the conservafor the productionof a fuel gas of high heating tion of petroleum natural resources and their value from solid carbonaceous materials. utilization for the production of locomotion fuels Another object is to provide a process and and lubricating oils would be materially enhanced `apparatus for the generation of high heating by improvements in the economics of coal utilizavalue fuel gases which are particularly suited tion. This may be accomplished by an efficient to the utilization of low grade solidcarbonaceous processfor the gasification of coal at thesource fuels containing volatilizable constituents, e. g., to produce a heating gas competitive with a bituminous coals and lignite. natural gas having a heating value of about Still another object of this invention is `to pro 1,000 B. t. u.s per cubic foot. Several requirevide such a process wherein low grade petroleum ments must be met before such as gasification hydrocarbons may be utilized to advantage for process is economically attractive: enrichment of the gases obtained by gasification (1) The gas produced must have a high heatof solid fuels. ing value approaching 1,000 B. t. u.s per cubic A further object is to provide an improved foot to permit economical transportation over apparatus for the gasification of solid carbonlong distances. aceous materials in particle formto produce a (2) The process must have high thermal ei- 50 mixture of-carbon monoxide and hydrogen.

ciency.

(3) The process must be sufciently iiexible to handle a number of grades of coal, preferably as received from .the mines or `as lay-products without excessive prehandling, such as Washing, cleaning, sizing or drying.

Other objects and advantagesof this invention will be evident from the following detailed description.

, In accordance with the present invention, nely divided solid carbonaceous material is fed-.to a distillation zone into a bed of particles undergoing distillation. Hot gases, comprising carbon oxides and hydrogen from a subsequent gasification reaction, are passed upwardly through the bed. The velocity of the gases is such that the bed of particles is maintained in dense fluid phase insuring free flow of solid particles and intimate admixture of fresh feed with heated particles. In the distillation zone, the particles of solid feed material are heated to a temperature suicient to drive off any volatilizable constituents contained in the feed.

The resulting carbonized preheated particles are fed directly into a gasification zone or ow type gas generator in which the particles are gasied in disperse phase. Gasication is carried out with steam and oxygen at high temperature. Hot gases from the gasification reaction supply heat to the distillation Zone. The distillation zone is operated at a temperature considerably lower than the temperature of the gasification zone. Under these conditions, a portion of the hydrogen and carbon oxides from the gasication Zone are converted to methane with a resulting increase in the heating value of the product gas.

The gasification zone is operated at a temperature within the range of from about 1300 to about 3200 F. while the distillation zone is operated at a temperature within the range of 1090 to 1800" F., and preferably within the range of 1200 to 1500* F.

In a preferred embodiment of the process of this invention, a hydrocarbon oil, for example, bunker fuel oil, crude residuum, or the like, is injected into the distillation zone at the top oi the fluidized bed of carbonaceous particles. The hydrocarbon oil wets the particles of carbonaceous material and substantially eliminates carry-over of the coal particles in the gas stream. As the particles of solid move downwardly through the distillation Zone Vtoward the point of inlet of heated gases from the gasiiication Zone. they become heated to a temperature approaching the temperature of the 'gases from the gasification zone.

Condensable oils and tars volatilized in the distillation zone are separated from the gas stream and may advantageously be returned to the distillation zone, preferably entering the distillation zone at the lowerinost portion of the bed of carbonaceous particles. This effects cracking of the tars and oils to gaseous hydrocarbons and residual carbon. The gaseous hydrocarbons enrich the product gas from the coal gasification zone and residual carbon is carried with the carbonaceous feed material into the gasification zone where it is reacted with oxygen and steam to produce additional gas.

The process and apparatus may be operated with coke from coal or petroleum as feed. Coke breeze is particularly suited as feed to the process. With coke as a feed, no volatilizableV constituents are present in solid feed to the distillation zone; additional hydrocarbon oil may be supplied to make up this deciency.

' In a preferred form of the apparatus of this invention, a generator of the downow type described in my copending applicati-on, Serial No. 7,446, led February l0, 1948, is employed as the gasiiication reactor. The preheating zone and gasification Zone of the apparatus of this invention are constructed as a unitary piece of apparatus, the preheating zone or distillation zone disposed directly above and in direct unrestricted communication with the gasification zone.

The novel unitary construction of the present generator is such that coal or other carbonaceous particles of a relatively wide range of sizes may be fed to the apparatus. The construction avoids the necessity for lvalves or other apparatus with moving parts operated at high temperatures. The novel apparatus, forming a part of this invention, contributes greatly to the improved results obtained from the process of this invention.

The process and apparatus will be more readily understood from the following detailed description taken together with the accompanying drawing.

The ligure is an elevational View, partly diagrammatic and partly in cross-section, illustrating a preferred form of the apparatus of this invention.

With reference to the figure, the gasification apparatus is in the form of a unitary reactor comprising a distillation Zone I and a gasiiication zone 2. The gasiiicaticn zone illustrated is the generator disclosed in my copending application Serial No. 7,446, iiled February l0, 1948.

The gasication zone is provided with an outer cylindrical steel shell G capable of withstanding an elevated operating pressure, and a refractory lining I of a material suited to the temperature conditions encountered in operation. Powdered solid carbonac-eous material is fed to the apparatus through line 3 into the distillation zone from which it passes through a conduit 8 into the upper end of the gasification zone. Oxygen is supplied to the gasiiication Zone through an oxygen line II and oxygen header I2. From the oxygen header, a series of feed pipes I3 introduce the oxygen, as controlled by valves I4, into the gasification zone immediately below the point of introduction of the solid carbonaceous feed niaterial and tangential to the inner surface of the zone.

Steam is introduced'into the gasification zone immediately below the points of introduction of oxygen.. Steam is admitted to the reactor through a series of feeder pipes I9 in amounts controlled by valves 2|. The feeder pipes IS, in turn, are supplied from header 2S and steam line 23. The feeder pipes preferably are directed into the gasification zone tangent to the inner wall and upward so that the particles of coal are directed upwardly and away from the walls, as fully described in said copending application.

Molten ash and slag formed by burning the coal is collected at the lower end of the gasication zone from which it is withdrawn through a slag disposal pipe 21.

A portion of the generated gases, comprising carbon monoxide and hydrogen, are withdrawn from the lower end of the gasification zone through a product gas line 3|. Water for quenching the product gas is supplied to the outlet line 3| through line 34. By this means, the hot product gas may be cooled to a temperature below that at which undesirable reactions take place. A regulator valve 35 in the product gas line 3| serves to control the pressure within the gasication zone and the quantity of gases withdrawn through line 3|, and therefore differentially controls the amount of hot gas flowing up through conduit 9, as will be brought out more fully hereinafter. V

Ihe distillation Zone is placed directly atop the gasification Zone. The distillation Zone comprises an outer steel shell 35 provided with a refractory line 3l. This zone is frustro-conical in cross section with the small end of the frustuni connecting with conduit 9. Thus, the diameter,

B and area, of the distillation zone increases `from conduit 99 upwardly Aalong the path of flow of gases from the gasification zone.

Product gases from the distillation zone are discharged through an outlet pipe 38 provided with a refractory lining 39. Water may be admitted through pipe 4I `to pipe 38 for quenching the gas, i. e., cooling it to a temperature below that at which undesirable reactions take place. Hydrocarbon oils maybe supplied "to the dis-` tillation zone `through line 43 and distributed therein by a distributing ring 4'4. l

A removable sleeve 45 of refractory material may be provided within conduit 9 to control the effective diameter of this conduit. The sleeve 46 may be removed or replaced by a sleeveof different internal diameter to vary the capacity of the apparatus in accordance with seasonal variations in demand for fuel gases.

Product gases discharged throughline 38 are passed vthrough a separator i wherein tars, condensable oils and solids are separatedfrom the gas stream. The resulting gas is discharged from the separator through line 52 to a `regulator' valve 53 which, in conjunction with valve `35, serves to control the pressure Within the gasification apparatus and to control `the quantity of gas discharged through line 38. Liquids and solids separated from the gas stream `are discharged from the separator 5i through line 56 from which they maybe returned to the distillationzone through pipe 5T to a point near the iowermost portion of the distillation zone or point of introduction of hot gases from the gasification zone. These residual materials are distributed by a spray nozzle 58 into the distillation zone. Alternatively, part or all of the tars and oils may be withdrawn through line 6| for other uses.

In operation, particles of coal are fed into the distillation zone I through line 8. The particles of coal tend to drop downwardly through the distillation zone due to the influence of gravity. The particles are contacted in the distillation zone by an upfiowing stream of hot gases from the gasification zone which retards their downward progress, the extent of the retarding effect of the gases depending upon the velocity of the gases, size of the coal particles, etc. A fiuidized bed of particles is maintained in the distillation zone at all times. The particle size of the feed material may range from about one quarter inch in average diameter to fine powder.

The gasification apparatus may be operated at substantially atmospheric pressure or at an elevated pressure, for example, up to about 1,000 pounds per square inch gauge.

The quantity of hot gases supplied to the distillation zone from the gasification zone, and hence, the velocity of the gases in the distillation zone may be controlledby regulation of the valve which restricts the quantity of gas Withdrawn from the gasification zone. It will be evident that under steady feed conditions, the quantities of gas evolved from the coal and oil fed to the distillation zone will be approximately constant. Therefore, any desired quantity of hot gases from the gasification zone may be passed upward through the distillation zone through conduit 9 by regulating the quantity of gas passing through valve 35. The remainder of the gases produced in the gasilication zone are discharged through conduit 9 into the distillation zone and through line 52 and regulator valve 53.

The quantity of carbonized coal entering the gasification zone from the fiuidized bed in the distillation Azone isldependent largely Aupon .the velocity ofgasesxthroughy-the.conduit S and the throatiofinsertd. itis evident that the feed to the .gasification `zone is controlled by the rate. of withdrawal of gases through the regulator valve 35. Fine particles carried .out of the fluid bed in the distillation zone through line 38 are recoveredin theseparator 5i in admixture with tars` and oils. 'I'he mixture `containing solid particles is returned to the distillation zone through line 5l. Distillation and cracking of the tars and oils Aresults in formation of coke which increases the particle size of the fine material both by .accretion and by agglomeration. Thus, all of the particles fed into the distillation zone v eventually dropdownwardly through the conduit '9 into the gasification zone.

Gases discharged from the distillation zone vthroughline 38 may be recycled to the bottom ofthe fluidized-bed of solids by means not illustrated in the drawing. The recycled gas may be heated or cooled before introduction into the distillation zone. Further control of the temperature and upward velocity of the gases in the distillation `zone may be effected by this means.

The bed of solid particles in the distillation zone is subjectto constant agitation and mixing dueto the fluidizing action of the hot gases passing upwardly therethrough. `Some of the develatilized particles, or char, moving downwardly through the .distillation .zone are entrained in the relatively high velocity hot gas stream entering the bottom ofthe zone and carried upwardly into admixture with fresh coal feed. The bed is a composite mixture of coal in various stages of devolatilization with a somewhat higher concentration of fresh coal in the upper portion of the bed. The mixing action of the fiuidized bed helps prevent caking of the fresh feed with resulting plugging and bridging in the lower portion of the distillation zone. Where difficulty is encountered due to the agglomerating characteristics of the feed, the distillation zone may be readily cleared of agglomerates or coke deposits by simply interrupting the flow of coal, reducing the rate of gas withdrawal through valve 35, and allowing some of the steam and oxygen to flow from the gasication zone into the distillation zone for reaction with the interfering deposit.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

l. A process for the gasification of a solid carbonaceous material containing volatilizable constituents which comprises maintaining a dense phase uidized bed of particles of said solid carbonaceous material in a distillation zone wherein said volatilizable constituents are distilled therefrom, disposing said distillation zone u directly above a gasification zone and in direct communication therewith through an intermediate zone of restricted cross-sectional area permitting free fiow of particles of solid carbonaceous material from the lower portion of said fluidized bed into the upper portion of said gasification zone and free fiow of gas from said gasication zone to said distillation zone, introducing oxygen-containing gas into said gasification zone into contact with carbonaceous particles from said distillation zone effecting reaction with said carbonaceous particles in said gasication zone, passing gaseous reaction product from the upper portion of said gasication zone into the lower portion of said distillation zone through said intermediate zone countercurrent to the ow of said particles entering the gasication zone at a velocity such that said particles are admitted into said gasication zone at a limited rate, and withdrawing additional gaseous reaction product from the lower portion of said gasification zone.

2. A process as defined in claim 1 wherein hydrocarbon oil is sprayed onto the top of said luidized bed in said distillation zone.

3. A process for the gasification of a solid carbonaceous material containing volatilizable constituents which comprises maintaining a dense phase uidized bed of particles of said solid carbonaceous material in a distillation zone wherein said volatilizable constituents are distilled therefrom, disposing said distillation zone directly above a gasification zone and in direct communication therewith through an intermediate zone of restricted cross-sectional area permitting free flow of particles of solid carbonaceous material from the lower portion of said uidized bed into the upper portion of said gasification zone and free iiow of gas from said gasification zone to said distillation zone, introducing oxygen-containing gas into the upper portion of said gasification zone into contact with carbonaceous particles from said distillation zone effecting reaction with said carbonaceous particles dispersed in gas while passing said particles downwardly through said gasification zone, passing gaseous reaction product from the upper portion of said gasification zone into the lower portion of said distillation zone through said intermediate Zone countercurrent to the flow of said particles entering the gasication zone at a velocity such that said particles are admitted into said gasification zone at a limited rate, introducing steam into said gasication Zone below the point of introduction of said oxygen-containing gas and below the point of withdrawal of gaseous reaction product introduced into said distillation zone, and withdrawing additional gaseous reaction product from the lower portion of said gasification zone.

LEON P. GAUCHER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,394,043 Smith Oct. 18, 1921 1,866,399 De Baufre July 5, 1932 2,028,946 Niconoi Jan. 28, 1936 2,323,501 Tuttle July 6, 1943 2,408,600 Berg Oct. 1, 1946 2,429,359 Kassel Oct. 21, 1947 2,438,261 Utterback Mar. 23, 1948 2,445,328 Keith July 20, 1948 FOREIGN PATENTS Number Country Date 634,877 Germany Sept. 9, 1936

Claims (1)

1. A PROCESS FOR THE GASIFICATION OF A SOLID CARBONACEOUS MATERIAL CONTAINING VOLATILIZABLE CONSTITUENTS WHICH COMPRISES MAINTAINING A DENSE PHASE FLUIDIZED BED OF PARTICLES OF SAID SOLID CARBONACEOUS MATERIAL IN A DISTILLATION ZONE WHEREIN SAID VOLATILIZABLE CONSTITUENTS ARE DISTILLED THEREFROM, DISPOSING SAID DISTILLATION ZONE DIRECTLY ABOVE A GASIFICATION ZONE AND IN DIRECT COMMUNICATION THEREWITH THROUGH AN INTERMEDIATE ZONE OF RESTRICTED CROSS-SECTIONAL AREA PERMITTING FREE FLOW OF PARTICLES OF SOLID CARBONACEOUS MATERIAL FROM THE LOWER PORTION OF SAID FLUIDIZED BED INTO THE UPPER PORTION OF SAID GASIFICATION ZONE AND FREE FLOW OF GAS FROM SAID GASIFICATION ZONE TO SAID DISTILLATION ZONE, INTRODUCING OXYGEN-CONTAINING GAS INTO SAID GASIFICATION ZONE INTO CONTACT WITH CARBONACEOUS PARTICLES FROM SAID DISTILLATION ZONE EFFECTING REACTION WITH SAID CARBONACEOUS PARTICLES IN SAID GASIFICATION ZONE, PASSING GASEOUS REACTION PRODUCT FROM THE UPPER PORTION OF SAID GASIFICATION ZONE INTO THE LOWER PORTION OF SAID DISTILLATION ZONE THROUGH SAID INTERMEDIATE ZONE COUNTERCURRENT TO THE FLOW OF SAID PARTICLES ENTERING THE GASIFICATION ZONE AT A VELOCITY SUCH THAT SAID PARTICLES ARE ADMITTED INTO SAID GASIFICATION ZONE AT A LIMITED RATE, AND WITHDRAWING ADDITIONAL GASEOUS REACTION PRODUCT FROM THE LOWER PORTION OF SAID GASIFICATION ZONE.

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