US2965461A - Apparatus for gasification of solid materials - Google Patents

Description

Dec. 20, 1960 s. w. WALKER 2,965,461

APPARATUS FOR GASIFICATION OF' SOLID MATERIALS *i Original Filed Deo. 30, 1950 N N t0 10 L -\\\\\v\\` \\\\\\\\\\\\\\`H\`\\\\\\\ INVENTOR.

SCOTT W. WALKER Arm/mfr United States Patent() APPARATUS FOR GASIFICATON OF SOLID MATERIALS Scott W. Walker, Tulsa, Okla., assiguor to Pan American Petroleum Corporation,` a corporation of Delaware The present invention relates to an apparatus for the gasification of solid carbonaceous materials, such as bituminous coal, lignite coal, coke, etc., to produce fuel gas and synthesis gas (CO and H2). More particularly, it pertains to an apparatus lfor the production of gases of the aforesaid type in a manner such that maximum conversion of carbon into CO is achieved, while at the same time simplifying the procedure of removing the resulting ash from the gas generator.

Although gas generators for the production of fuel and synthesis gases have been employed for a number of years, `the problems of ash removal and economical utilization of the carbon to be converted have, to a large extent, exerted rather extreme limitations on the design of commercial gas generators. The'gas producer, Lurgi, Winkler, and other bed-type generators provide means for withdrawing the ash in the form of a solid. Other generators, such as the ThyssenGalocsy and Leuna gas generators, provide for Vremoval `of the ash in the form of molten slag. When a carbonaceous material, such as coal, is to be gasilied in a fluidized bed-type generator as employed in the Koppers design, the ash can be removed either as afsolid or as a molten slag. Gascationof carbonaceous materials by any of the above-mentioned methods presents some rather serious ditliculties; this is especially true` with the fluidized type generators where the solid ash is so finely divided that it gives rise to complicated dust removal problems. Also, where the operation is eected at high temperatures, line particles of slag coming in contact with the refractory of the combustion chamber roof and walls cause deterioration thereof. One of the chief reasons for the existence of these problems in the Ycase of currently designed generators resides in the fact that the coal or other solid carbonaceous raw material employed is ground to an extremely -ne particle size so that complete combustion can be obtainedin the spray-type burners now utilized. The ash particles resulting from this combustion are likewise very fine and, thus, become quite a problem to collect and separate from the generated gas.

`I have now'devised a methodand apparatus by which valuable gaseous products, such as fuel gas and hydrocarbon synthesis gas, can be produced readily and economically without the accompanying disadvantages of prior methods. In accordance with my invention, a solid carbonaceous fuel is broken into particles or small lumps ranging in size from about 3 to about 100 mesh,

after which the resulting comminuted fuel is mixed with a suitable driving gas such as, for example, steam or oxygen, and introduced into` the combustion zone of a gas generator. Air may be injected along with the steam instead of oxygen; however, regardless of its manner of introduction, sutiicient oxygen should be present in the combustion zone to insure satisfactory burning of the fuel particles at the temperature levels employed. Selection of fuel particles, having the average particle size given above, results in the effective reduction of ash lines since, by using initially the relatively large -fuel particles, the latter are only partially burned on exposure to; the combustion zone and -by gravity are removed therefrom together with slag impurities. Under the combustion conditions employed, the ash melts forming a fluid slag'on the lloor of the generator. In accordance with this method of effecting combustion of the fuel particles, I am able to control residence time and, in turn, the extent of combustion of said particles in the combustion zone. Thus, for any given Ifuel, I can readily determine the conditions under which combustion should be carried out inorder to elect only a partial burning of the particles and to allow the latter to retain sufficient mass to be carried out of the zone of combustion. The path or trajectory taken by the fuel particles is, of course, a function of ,their density and the pressure exerted by the driving gas employed. For a fuel of given density, the required force supplied by the driving gas to project particles of such fuel out of the combustion zone after only a partial burning thereof has occurred can be readily determined by simple experiment. The partially burned fuel particles are carried on the surface of this slag and react with primary products of combustion from the combustion zone to obtain further gasification of this carbonaceous material on the surface of the slag and shift the CO2 and water to CO and H2. Conversion of this partially burned carbon by CO2 and water to CO and H2 may be accomplished in a number of Ways. Generally, however, I prefer to allow the ash formed by this partial combustion or burning operation to be converted into a slag of` suitable viscosity, and thereafter impinge the gaseous products from the primary combustion zone onto the mixture of slag and solid fuel particles. In this manner, the carbonaceous fuel on the surface of the slag is converted into valuable gaseous products while the ash formed during this reaction as well as any ash from the primary combustion zone is taken up by the molten slag, thereby effecting separation of this undesirable material (ash) from the product gases. ln instances where the lumps or particles of partially burned carbonaceous fuel are intimately mixed with the slag, furtherreaction of such carbon with primary combustion zone gases can be effected by blowing the latter through said mixture in accordance with the general Bessemer converter technique. However, I ordinarily prefer to convert the carbon in mixtures of this type by flowing the latter `onto an inclined surface in a thin, extended iilm, and thereafter pass the primary combustion gases over it. Alternatively, I may withdraw the slag, allow it to solidify, crush it, and thereafter mix it with fresh solid fuel particles comprising the feed to the gas generator. By this means, the unburned carbon in the solid slag may be converted to useful products.

The size of the solid fuel particles employed may vary; however, in the majority of instances, I prefer to utilize solid fuels having a particle size of from about 5 to 15 mesh with the major portion of said particles being in the neghborhood of from about l0 to about 12 mesh. Fuel particles of greater or smaller size than those stated may be employed. However, I have found iii general that it is undesirable to use fuels having a particle size less than mesh or greater than 3 mesh. Moreover, for satisfactory operation it is generally undesirable to `have more than `5 percent of either the 3 mesh or the 100 mesh size fuel particles (l0 percent in the aggregate) in the fuel mixtures employed in my invention.

Figure l is a sectional elevational view of a form of apparatus which may be employed in carrying out the process of my invention while Figure 2 is a fragmentary view, partly in section, of burner 12 generally shown as a sectional view in Figure l.

Additional details of the apparatus of my invention generator. design is shown.

are illustrated by the following description of a preferred embodiment thereof as set 'forth in Figure 1 of the drawings wherein a sectional view of a preferred AsY illustrated in the drawing, the gas generatoryaccording to. my invention, has a generally horizontally. positioned combustionchamber 2, where'primary combustion of the solidfuel. particles occurs. The Walls `ofthe chamber, as well asV the iloor of the generator, chimney and ramp-like structure V4, are constructedof a suitable refractory material `6. Steam introduced through line 8 is mixed with. particles of. a solid fuel. (.10 .to` mesh) such as, for. example, coal, fed through line 1.0, and projectedthrough burner 12 equipped with jets 14 and supplied withoxygen through line 16. The temperature of the combustion zone may vary fromabout 2200 Eto `about 35.00 F.the residence time of theV coal and steam.mixture in the combustion zone being such that from about 25 to about 50 percent of the original carbon. inV said coal particles. is incompletely burned. The partially -burned coal being relatively dense carries the ash out of the combustion zone by gravity onto the floor of the generator where there is ultimately formed a slag bed 18'ofmolten ash with unburned coal particles floating on the surface thereof. The arcuate path of the partially burned coal particles from the burner to the surface of the molten slag is dened by lines 19. In the event that these coal particles tend to become suspended in the molten slag, further combustion of the coal can be eiected, if desired, by introducing additionalsteam or other suitable gas into chamber 2 through line 20 under relatively high pressure, whereby slag bed 1S is extended into a relatively thin film or sheet along the inclining surface of ramp 4. The pitch of ramp .4 may vary considerably; however, for eiicient contact of the combustion gases with the fuel particles, the sloping surface should not appreciably exceed an angle of about 30 degrees. The gases from the primary combustion zone are passed over the aforesaid lrn and the partially burned fuel particles converted into CO and H2. `Normally, little rdifficulty is experienced with the coal or other partially burned solid fuel particles sinking into the slag ,bed owing to the relatively wide difference in density between the latter and the said coal particles. The gases thus produced are free fromobjectionable quantities of ash and are withdrawn through chimney 3 Vat a temperature of from about 1800 F. to about 25.010 F. and passed through a waste heat boiler. capableY ofY supplying all steam .requirements of the generator. Thereafter, the gas may be puriiied in accordance with known procedures after which it is ready for use,` Asthe slag accumulates, it may be drawn oit periodically through tap 22. If desired, a layer` of chilled solid slag 24 may be provided in order to prevent excessive erosion of the refractory by the action of molten slag thereon. The aforesaid layer of solid slag located adjacent the floor of the combustion zone is formed by rapid withdrawalof heat from molten slag through cooling coils 26. Cooling in this manner may be effected by the use of materials, such as diphenyl, steam, water, etc.

Figure 2 is a more detailedV representation .of burner 12 showing a fragmentary end view thereof. In this particular burner design oxygen or other suitable combustible gas flows through pipe 16 into a hollow space between the interior. and exterior portions of burner 12. Oxygen introducedinto the burner in this manner ,is then conveyed to the open interior portion thereof passing throughV jets 14 asindicated by the arrows.

The ash content of a solid fuel, such as coal, is generally composed of aluminum oxide, ferrous oxide, calcium oxide and silicon ,dioxide and is usually high in the basic constituents, `thus resulting inrelatively viscous slag. The viscosity and melting point of .such a slag, however, may be readily reduced by the introduction of additional silicon dioxide. The resulting slagtypically contains 40 to 50 percent ferrous oxide, 20 to 25 percent calcium oxide,`and 2OV to 25 percent silicon dioxide. In general, it may be said that slags melting in the neighborhood of from about 1800 to 2000 F. are satisfacrtory for use in the process of ,my invention. Slags other than those speciiically mentioned above and having the aforesaiddesired properties may be selected from awide range of such materials employed in the non-ferrous metals art. Slags .having theproperdensity can. readily be determined experimentally. Other materials which contribute to the degree of viscosity and melting point of the slag such as, for example, sodium oxide and zinc oxide, may be added i-f desired. Also, it may generally be found desirable to ladd these viscosity and melting point depressants to the solid coal particles so that they are injected into the burner along'withthe coal particles and steam. By this means, the ash and slag-forming constituents are intimately mixed, passed through the -hot combustion zone and fall' to the floor of the generator at melting temperature. Y

The quantity of slag required to entrap the ash particles formed by the combustion process may be conveniently .controlled by pulverizing previously formed low-melting slag and mixing it with the coal or other solid fuel particles together with other slag-forming constituents, if desired. Normally, the quantity of slag mixed withthesolid fuel particles may vary considerably; however, in the majority of instances, from about 10 to about 25 Weightpercent of slag in the charge will be found adequate. This mixture of slag and fuel `particles is blown into. the .combustion chamber where the comminuted slag contained therein is rapidly melted forming liquid droplets which fall in a shower to effectively trap the ash particles thus formed so that the latter is incorporated into the slag bed. y With regard to the nature of the steam and CO2 mixtures employed, it may generally be said that the quantity of either of these materials utilized depends on the amount of oxygen present. The ratio of. steam and/or CO2 to oxygen is ordinarily preferably held at from about 1.0 to 3.0 butmay, in some instances, beras high as 6.0. In this connection, steam and CO2 may be considered asv equivalents inasmuch `as both of these `materials give` the sameyield of`H2 and CO withapproximately the same heat effect. AIt will be found that use of steam and/or CO2, in the concentrations just specified will result in steam and/or CO2 ratios to partially burned carbon in the combustion zone of ,from about 1.0 to about 3.0 mois per molof carbon.

One of the outstanding features of my invention is the fact that by the utilization thereofrIamable to employ any type of solid carbonaceous fuel without encountering the dicultiesexperienced with prior art procedures when employing coking coals and fuels ofrelatively low calorific content which, for Various reasons, have previously been considered undesirable. A further. advantage of my invention lies in the feature of recycling crushed slag to the regeneratorv since `this renders possible a substantial increase in the conversion of carbon over conversions obtainable by prior art procedures. Thus, the initially unburned carbon in .the primary slag is partially converted byl recycle thereby effecting, substantial carbon clean-up by recycleV ofthe .crushed slag.

Numerous changes` may be `made in the form. and structureof the apparatus as Wellasindetails of operation described herein. withoutd'eparting from the scope of the present invention.

This application. is. a .divisionof my copending application, U.S. Sen'alNo. 203,574iled December- 30, 1950, now ULS. 2,770,536. Y

I claim:

l. vIn an apparatus. for effecting combustion ofsolid combustible `materials to `,produce `both gaseous products of. combustion .and liquidv slag, the combination comprising; a1 combustion .chamber having a generally horizontal oor, means for horizontally injecting solid combustible particles into said chamber, a construction in said chamber opposite said injection means through wh ch products of combustion can pass, a passageway communicating with said construction and said chamber leading away therefrom, the floor of said passageway constituting an inclined surface having a grade not exceeding about 30 with respect to the horizontal, means for extending said liquid slag along said inclined surface, and means in said chamber for burning said particles, said burning means being adjacent said injection means.

2. In an apparatus for effecting combustion of solid combustible materials to produce both gaseous products of combustion and liquid slag, the combination comprising a combustion chamber having a generally horizontal oor, means for horizontally injecting said particles into said chamber, means in said chamber for burning said particles, said burning means being adjacent said injection means, a constriction in said chamber opposite said injection means through which products of combustion can pass, a passageway communicating with said constriction and said combustion chamber and leading away therefrom, an inclined surface within said passageway having a grade not more than about 30 with respect to the horizontal, and means for extending said liquid slag along said inclined surface.

References Cited in the le of this patent UNITED STATES PATENTS 909,920 Marconnet Ian. 19, 1909 1,039,398 Hirt Sept. 24, 1912 FOREIGN PATENTS 1,091 Great Britain Nov. 12, 1903 of 1903 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. fe

Scott W,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below'.

Column 5, lines 2 and 5v ier "soxstraetiem", oecurreaee, read eenstriotiom Signed and seaIeeI 'this 231th dey ef Iene IJI..

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents

Claims (1)

1. IN AN APPARATUS FOR EFFECTING COMBUSTION OF SOLID COMBUSTIBLE MATERIAL TO PRODUCE BOTH GASEOUS PRODUCTS OF COMBUSTION AND LIQUID SLAG, THE COMBINATION COMPRISING A COMBUSTION CHAMBER HAVING A GENERALLY HORIZONTAL FLOOR, MEANS FOR HORIZONTALLY INJECTING SOLID COMBUSTIBLE PARTICLES INTO SAID CHAMBER, A CONSTRUCTION IN SAID CHAMBER OPPOSITE SAID INJECTION MEANS THROUGH WHICH PRODUCTS OF COMBUSTION CAN PASS, A PASSAGEWAY COMMUNICATING WITH SAID CONSTRUCTION AND SAID CHAMBER LEADING AWAY THEREFROM, THE FLOOR OF SAID PASSAGEWAY CON-

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