US2751287A - Gasification of fuels - Google Patents

Description

June 19, 1956 E. E. DONATH 2,751,287

GASIFICATION OF FUELS Filed Oct. 25. 1952 2 Sheets-Sheet 2 IN VEN TOR. ,5 ZA/LST' .E Da/va TH- I j BY J57- M- United States l atent (3 GASIFIVCATION on FUELS Ernest Emanuel Donath, Pittsburgh, Pa., assignor to Koppers Company, Inc., a corporation of Delaware Application October 23, 1952, Serial No. 316,391

18 Claims. (CI. 4873) The present invention relates to improvements in processes-and/or apparatus for the production of useful gases, such as fuel gases and synthesis gases'for synthesis of chemical compounds, by the gasification of carbonaceous fuel. It further relates to such improvements in such processes and/or apparatus, whereby carbonized solid fuel, such as coke, which is suitable as a fuel or as feed material for standard fixed water bed machines is produced simultaneously with the production of said useful gases.

Modern coal chemistry calls for a process, which makes an inexpensive synthesis gas as a raw material for the manufacture of all kinds of synthetics, for example, synthetic fertilizers, fuels, plastics, hydrocarbons, and various other synthetics, which are derived from acetylene or other basic hydrocarbons. provement in the production of synthesis gas is of great importance to the chemical industry.

For the large amount of manufactured synthesis gas required by the chemical industry, coal and its derivatives are generally used. However, synthesis gas must be free from coal tar, because the presence of tar is prohibitive in many of the subsequent synthetic processes.

The complete removal of tar vapors from the manufactured gas is difficult and costly. Therefore, provisions have been made to avoid tar formation during gas production. This has been done in two different ways as follows:

1. Use of fuels like coke or char, from which all tar has been driven out in a previous treatment.

2. If tar-containing fuels like run-of-the-mine coal are used, operating conditions of gasification are so selected that all tar, which might be formed, is completely decomposed.

The operation of the standard water gas machine, utilizing a fixed bed of solid fuel, is a very well established process for producing synthesis gas with satisfactory performance. This process avoids tar formation and caking of the fuel bed, with resultant high pressure drops, by using coke or char as a raw material, from which all tar has been previously removed. However, the economical handicap of the process lies in the fact that the only fuels, which can be used are relatively expensive. As soon as the coke or char price is above one and onehalf times the coal price, the process cannot compete with other gas generating methods using coal or lignite as the raw materials, with steam and/or oxygen of high purity as gasifying agents. Such methods comprise what are known, and hereafter referred tom the present specification and claims, as dust gasification methods, wherein very finely-divided fuel is intimately contacted with gaseous gasification media, such as free oxygen and steam, whereby the oxygen exothermically reacts with a portion of the fuel to raise the temperature of the steam, the remaining fuel, and exothermic reaction products formed to temperatures favoring reaction of the same to form CO and H2. Among such dust gasi- 'cation" methods are included gasificationof finely-di- Therefore, every new im- 'than any process or apparatus known heretofor.

Patented June 19, 1956 vided fuel in suspension type gasifiers, such as vortex type gasifiers, fluidized bed gasifiers and gasifiers of the type described in copending U. S. applications 43,950, 43,952, and 43,953, filed August 12, 1948; U. S. application 131,008, filed December 3, 1949; U. S. application 226,792 filed May 17, 1951; and U. S. application 241,413, filed August 11, 1951; wherein a jet of finelydivided fuel suspended in an insuificient amount of oxygen to exothermically react with all of such fuel to form CO, is burned in a primary combustion zone, which is peripherally enveloped in a continuously, cocurrently flowing, annular stream of steam, the products from the combustion zone being commingled with the steam flowing from the envelope in a secondary endothermic reaction zone, where such steam endothermically reacts with unreacted fuel flowing from such combustion zone. In suspension type gasifiers, the very high temperatures at which the reaction is carried out, due to the rapid and intensive burning of fuel-oxygen suspension, causes the tar contained in the fuel to be completely decomposed and gasified. Furthermore, there are no fuel caking problems involved as in standard water gas equipment.

However, such dust gasification methods have certain-disadvantages in that,

1. It is difiicult, if not impossible, to force the endothermic steam-carbon reaction to the completion required to consume substantially all the fuel and to obtain sufficiently cooled exit gases, under conditions of gasification in presently known types of dust gasification equipment. Thus, off gases are exceedingly high in temperature and contain a considerable amount of unreacted steam, as well as dust containing, in addition to ash, considerable amounts of unreacted carbon. However, such dust is too poor in carbon content to be commercially utilizable as a fuel, and so, the carbon contained therein, is Wasted, in addition to the unreacted steam, thus reducing the efficiency of the gasifier.

2. Pure oxygen or oxygen-enriched air, both of which are very expensive to produce, must be utilized.

3. The reaction products emerge from the gasifier at extremely high temperatures, and thus, contain large amounts of sensible heat, a good deal of which must be wasted even with the use of expensive heat transfer equipment. Such heat is produced at the expense of increased fuel consumption and relatively expensive oxygen. consumption, thereby increasing costs considerably.

4. The eflicient removal of liquid slag, produced at the high temperatures required during the gasification, is very difficult, especially, when the dust gasification" is carried out at increased pressures. Such liquid slag is very corrosive and causes rapid equipment deterioration if not efficiently removed.

The present invention provides an improved dust gasification process and/or apparatus of the type described above, whereby many of the above disadvantages are avoided or reduced, so that the fuel is utilized with less oxygen and steam to produce more synthesis gases and less unreacted carbon-containing dust and less unreacted steam with more efficient slag removal and less equipment deterioration due to inelfciently removed slag, The present invention further provides such an improved process and/ or apparatus, wherein a useful, solid, carbonized fuel, suitable for use as a fuel or a starting material for standard water-gas generators, is produced from coal products simultaneously with and in cooperation with the above mentioned more eflicient production of synthesis gas.

The present invention further involves such an improved process and/or apparatus, wherein lumps of tarcontaining solid fuel of different size preferably of the size utilized in standard water gas generators, are carbonized and/or gasified in a fixed bed simultaneously with and in'cooperation with the above mentioned, improved efficient productionof synthesis gas, without caking of such fixed bed with resulting prohibitive pressure drops through-the bed, without contamination, with tarry matter, of the useful gases produced in 4 and passed through the bed, and with a widerange of fuel size used in the fixed bed. i

The present invention further involves an improved process'and/orapparatus for gasifying a fixed bed of solid carbonaceous fuel to produce synthesis gases without caking of such' fixed bed with resulting prohibitive pressure dropsthrough'the bed, without contamination,

with tarry matter, of the useful gases produced in and passed through the bed and with a wide range of fuel size of the fixed bed.

In accordance with the present invention, it has been found that the above disadvantages of prior art dust gasifiers can be avoided and the above improved processes can be carried out, by gasifying in a dust gasifier a finely-divided, carbonaceous fuel, with a chemically combined oxygen-containing fluid capable of reacting endothermically with the finely-dividedfuel, such as steam, and/or a free oxygen-containing gas, impinging the hot gaseous mixture of reaction products flowing from such dust gasifier, while still hot and untreated in any manner, upon a portion of one surfacerof a fixed bed of moving, solid, carbonaceous fuel, so that such bed is partially, but not completely,.penetrated by the impinging hot, gaseous mixture, at-least apart of the penetrated portion of the bed being converted into useful gaseous material during contact with the hot gaseous mixture and at least a part of the' fuel in the nonpenetrated portion of the bed being simultaneously carbonized by heat radiatedand conducted from the hot gaseous mixture to the nonpenetrated portion of the bed, removinggaseous material from the penetrated and nonpenetrated portions of the bed via the same surface upon a portion of which said hot gaseous mixture is impinged, without having penetrated the bed completely with the hot gaseous mixture and finally removing the refuse flowing from such fixed bed.

Fresh steam or other media as COz-can be continuously and simultaneouslyilowed through the bed of solid fuel from the surface of the bed opposite to the surface upon a portion of which the hot gaseous mixture is impinged, so as to flush gaseous material from the-nonpenetrated portion of the bed into the penetrated portion of the-bed, and thence, together with gaseous material present in the penetrated portion of the bed and along means for flowing therefrom hot reaction products, a

chamber connected at one of its ends with the dust gasifier outlet means, so that the hot gaseous mixture of reaction products from the dust. gasifier can be introduced directly into such one end of the chamber, means for introducing solid, carbonaceous fuel into the chamber and for maintaining a fixed bed of such solid fuel moving through such chamber, means for impinging the flow of hot gaseous mixture of: reaction products introduced into the chamber, onto a portion of a surface of the fixed bed of moving solid, carbonaceous fuel within such chamber, so as to partially, but not wholly penetrate the bed of solid fuel, means forthereafter flowing the hot gaseous mixture-impingedupon a portion of such. suructs which in addition to carbon monoxide and hydrogen contain carbon dioxide and unreacted carbon and steam issuing from known types of dust gasifiers are impinged upon a portion of the surface of a moving bed of preheated, solid, carbonaceous fuel, so as to partially enetrate the depth of such bed, and are, thereafter flowed either cocurrently with or countercurrently or cross-currently to such moving bed through a penetrated portion thereof and along such surface thereof, and are finally separated from such surface and penetrated portion of the bed without having penetrated its depth com pletely.

Simultaneously, flush steam is flowed through the bed from'the surface opposite to the impinged surface.

The relative thicknesses of the penetrated and nonpenetrated portions of the bed and the particular reactions occurring in each of said portions may be controlled by controlling the rates of flow of solid fuel through the chamber, hot reaction-products from the dust'gasifier and flush steam through the bed,,as well as the angle at which the hot reaction product is impinged upon the surface of the bed, the length of the bed, and the relative directions of flow of the solid flow and hot reaction products (for example, cocurrent, countercurrent, crosscurrent) and the size of the-fuel in this bed.

In that portion of the bed, which is penetrated by the hot reaction products, which is-primarily a gasification zone, the volatile matter is volatilized, and together with at least a portion of the total nonvolatile carbon contained in the dust gasification" products and carbonized fuel of the penetrated portion of the moving bed, is gasified by the carbon dioxide and unreacted steam in the dust gasification products as well as the flushing steam being flushed through such penetrated portion of the bed.

The high temperatures and large quantities of sensible heat in the dust gasification products provide the rcquired heat of gasification and volatilization in the penctratcd portion of the bed, the withdrawal of such heat by the volatilization and gasification in the fixed bed providing a very effective means for cooling the hot dust gasification reaction products. That portion of the bed. which is not penetrated by the hot product gases, which is primarily a carbonization zone, is subjected to heat radiated and conducted from the hot product gases and is carbonized or carbonized and gasified effectively thereby. The volatile matter volatilized by such carbonization is flushed into the penetrated portion of the moving bed by the flushing steam and becomes admixed with the gases produced or present in that portion of the bed, the resultingfmixture of gases being flushed out of the penetrated portion of the bed and finally out of the chamber by the flow of flushing steam.

Preferably, the rates of flow of hot product gases from the dustgasifier, flushing steam through the bed, and solid fuel through the chamber, as well as the depth and length of the bed and the angle of impingement of the hot reaction products on the surface of the bed, are controlled sothat the volatile matter volatilized in the nonpenetrated 'portion or carbonization zone of the bed is. gasified or reacted to form CO and hydrogen, as it is flushed through 'and from the nonpenetrated portion-to and through the penetrated portion of the bed, without any substantial gasification of the nonvolatile carbon of the carbonized fuel in the nonpenetrated portion of the bed. The above mentioned variables can also be controlled, so that part of or substantially all of the carbonized fuel in' the nonpenetrated portion of the bed is also gasified by the flush steam flowing therethrough, to form useful gases, which are flushed through and from the nonpenetrated portion of the bed to and through the penetrated portion of the bed and finally out of the chamber, or so that only volatile matter is volatilized and gasified or reacted in the penetrated portion of the bed with substantially no gasification of nonvolatile carbon in such penetrated portion, or when the flow of solid fuel is countercurrent to the flow of the hot gaseous mixture, so that volatile matter is volatilized in the penetrated and nonpenetrated portions of the bed with only a small part or substantially none of such volatile matter being gasified or reacted to form CO and hydrogen.

Ordinarily, the hot reaction products are impinged upon the top surface of a horizontally moving bed, whereas flush steam, if utilized, is flowed into the bottom surface of such horizontally moving bed. However, the invention is not limited to a horizontally moving bed.

The unreacted carbon and steam contained in the products issuing from the dust gasifier directly into the fixed bed of fuel commingle with the high carbon-containing penetrated portion of the fixed bed of carbonaceous fuel. The high carbon content of the resulting commingled mixture, as well as the increased surfaces presented by the fixed bed of fuel increases reaction between such carbon (the unreacted carbon from the dust gasifier and the carbon contained in the fuel of the penetrated portion of the fixed bed) and unreacted steam. The very high temperatures and hence large amounts of sensible heat in the dust gasification products, as they emerge from the dust gasifier, raises the temperature of that portion of the fixed bed, where such products penetrate, to very efficient gasification temperatures, high enough to gasify any tar or other volatile matter given off by the carbonaceous fuel in those cases where such fuel contains such tar or volatile matter. Furthermore, the heat radiated and conducted from such hot gases is sufficient to volatilize the volatile matter contained in the fuel in that portion of the fuel bed which is not penetrated by the hot reaction gases. As the hot dust gasification products flow cocurrently, countercurrently or crosscurrently with the moving fuel of the fixed bed, away from the point of introduction of such dust gasification products into such bed, both the fuel in the bed and the hot reaction gases are cooled due to the endothermic reactions occurring in the fixed bed, so that the refuse and gases finally removed from the fixed bed are relatively cool. In this way, the reaction products from the dust gasifier are cooled, resulting in less heat being discarded and therefore less oxygen and finely-divided fuel being consumed during the dust gasification, to produce the same amounts of useful gases, while at the same time, the unreacted materials (carbon and steam) contained in such reaction products are substantially completely reacted in the penetrated portion of the fixed bed or are rendered commercially utilizable in that the unreacted carbon present in too small amounts in the hot reaction products to even be useful as a fuel is either completely gasified with carbon dioxide and unreacted steam in the penetrated portion of the bed to form useful gases, or if not completely gasified, the nongasified portion of the unreacted carbon is added to the carbon of the fuel in the penetrated portion of the bed, the resulting residue having such a high carbon I content, as to be commercially utilizable as a fuel. Thus, the unreacted carbon, nonutilizable as it exists in the hot reaction products becomes utilizable when combined with the carbon of the fuel in the penetrated portion of the bed. Thus, less oxygen, steam, and pulverized fuel are wasted, reducing the cost of dust gasification operation considerably. Furthermore, capacity of the dust gasification equipment is increased considerably, thereby requiring ,less dust gasification equipment for the same gas output and hence, less labor costs.

At the same time, by means of the heat in the dust gasification reaction products, lumps of solid, carbonaceous fuel in the penetrated and nonpenetrated portions of the bed are completely devolatilized, the volatile matter in the penetrated and nonpenetrated portions of the bed being gasified or reacted to form carbon monoxide and hydrogen if desired. Furthermore, a portion of the carbonized fuel in the penetrated and/or nonpenetrated portion of the bed may be gasified. Thus, volatilization and gasification in a fixed bed is carried out in accordance with the present invention without the necessity of using valuable additional fuel and oxygen to provide heat for such volatilization and gasification, while at the same time dust gasification reaction products are effectively cooled and nonutilizable or unreacted materials contained therein are substantially completely reacted or made utilizable.

The carbon content of the refuse from the fixed bed depends upon the rates of flow of the carbonaceous fuel of the fixed bed, the reaction products from the dust gasifier and flush steam through the bed, as well as the length and width of such bed, the angle of impingement of the reaction products on the surface of the bed and the relative directions of flow of the solid fuel and hot reaction products. These variables can be so controlled that much of the carbon content of the penetrated portion of the bed, in addition to the unreacted carbon in the productsof the dust gasification are consumed, leaving only liquid slag, containing small amounts of carbon distributed therein, which liquid slag is absorbed by the nonpenetrated portion of the bed. Furthermore, these variables will determine the carbon content of the nonpenetrated 'portion of the bed. For instance, all the carbon in the nonpenetrated portion of the bed as well as in the penetrated portion can be consumed leaving only liquid slag. However, it is preferred to control these variables, so that the refuse flowing from the bed contains a sufficient amount of carbon to be utilizable commercially as a fuel and also as a raw material for standard water gasification products. In such case, the molten slag produced in the dust gasifier, as well as any molten slag produced in the fixed bed is or remains absorbed by the solid fuel of the fixed bed, thereby solidifying such slag and making its removal in solid form possible. This provides a novel way of slag removal during dust gasification, especially when carried out under pressure, and decreases refractory corrosion in the gasifier due to slag depositing therein.

The process and apparatus of the present invention are particularly advantageous in that the hot reaction gases from the dust gasifier do not penetrate the bed of fixed fuel. Ordinarily, in fixed bed gasifiers, the gases must pass completely through the bed and hence any caking in such bed due to the use of caking coals, results in prohibitive gas pressure drops and hence inoperable processes. Furthermore, the fuel size must not be too small, or else prohibitive pressure drops will result. In applicants present process and apparatus, since the gasifying media, the hot reaction gases, do not pass completely through the bed, caking of the fuel in the bed and fuel size present slight pressure drop difl'iculties whether the How of hot reaction products is cocurrent, countercurrent, or crosscurrent to the flow of fuel in the fixed bed. Although the flush steam must pass through the bed, the amount of such steam is so small that the problem of pressure drop is not pertinent. Furthermore, the use of flush steam is not essential to the present process and apparatus, although it is preferred in that it serves to keep the grate supporting the bed cool, to flush the gaseous material out of the bed and in some cases to gasify the fuel. Another advantage of the present invention in those cases where the flow of hot reaction products is cocurrent with the flow of solid fuel of the bed is that any tarry matter volatilized from'the'fuel in thepenetrated and nonpenetrated portions of the'bed'are-gasified-to-useful-gases, thus permitting tar containing-fu'elsto be'utilizedavithout contaminating the useful gases produced with tarry matter.

when the bed is supported on a rotary grate, considerable gasification 'ofthe'fuel' in the penetrated and nonpenetrated portions of the bed is obtained.

As stated above, the penetrated portion of'the bed is primarily a gasification .zone, while the nonpenctrated portion of the bed is primarily a carbonization zone. The size of these two zones depends on a number of variables, e. g., the depth of the total bed, the angle at which the reaction products are impingedup'on thesurface f the bed and the velocityof flow and temperature 'of the hot reaction products. If a maximum 'of low ash-containing coke is desired, the carbonization' zone should be maintained as large as possible, but not too large for heat to be radiated and conducted'thereto and the"gas'ification zone should be maintained as small as possible with a minimum of low temperature'fiush steam, whereas if a' maximum of useful gases is desired, the carbonization zone should be maintained as small as possible and the gasification zone maintained as'large as possible, with a maximum amount of flush steam being utilized at very high temperatures.

The hot products of dust gasification may be impinged perpendicularly upon the hot surface of -the bed or at any angle desired. When impinged perpendicularly upon the bed, the penetration of -the' bed is maximum, whereas if the product gases are impinged upon the top surface of the bed at an angle, penetration is less. Any degree of penetration can be obtained by selecting the proper ratio of the cross-section of the solid fuel bed to that of the free space available for the'fiow of gaseous products and by regulating theangle of impingement of the product gases upon the topsurface of the bed and the rate of flow of hot reaction products. 'The lessthe penetration of the bed, the more fuel is carbonized in the nonpenetrated portion of the bed.

The residue of the bed can be utilized as a fuel in producing and superheating steam for the "dust gasitier and for drying and preheating fuel for the dust gasification and for the fixed bed. If the rate of flow of the tarcontaining coal in the fixed bed is controlled so that only the volatile matter of such coal in addition to a small amount of the total carbon contained in the penetrated portion of the fuel bed and the products of the dust gasification, are gasified, the residue is suitable as a coke in slagging or nonslagging type gas generators at atmospheric or elevated pressures or in standard water gas machines, thereby increasing the efficiency of the dust gasification process while at the same time carbonizing coal. Undersized particles of this refuse can be recycled and used as a fuel for the dust gasification step. In those cases where very high carbon-containing bodiment of the present invention.

lit

"Figure-irepresents a modification of the upper portion of Figure 1 and shows diagrammatically an apparatus arranged for countercurrent flow.

' Figure 1 discloses carbonizer and secondary gasifier 41, connected with dust gasifier 40, so that hot dust gasification reaction products issuing from dust gasification reaction chamber 21 (Figure 3) are impinged upon a portion '49,'of the surface of a fixed bed 44, of solid carbonaceous fuel, supported on a moving grate 53. Carbonizer and gasifier 41 is connected with lump coal feed bin 47, through feeder '48 (star valve), so that lump coal can be fed into carbonizer and gasifier 41. Gasifier 41 has an exit gas outlet at46, and a refuse discharge feeder 50, through which refuse is discharged into refuse bin 51, from which it passesthrough conduit 52. Flush steam inlets 45 are spaced along the bottom of gasifier 41. Dust gasifier 40 is of the type described in copending U. S. application 241,413. With reference to Figure 2, such gasifier comprises a conically shaped gasification chamber 1, having fuel dust-oxygen suspension inlet nozzles 3, connected with fuel dust-oxygen supply pipes 14, and an annular steam inlet nozzle 4, having a venturi shape and surrounding the fuel dust-oxygen inlet nozzles 3, and being connected with steam passages 11, and steam distribution means 12. The

' outer circumference of annular nozzle 4 is surrounded by an annular cooling jacket 6, having a cool water inlet 7, and a hot water outlet 9. The inner walls of nozzle 4 have a second cooling jacket 5, cooperating therewith, with cold water inlet 8, and hot water outlet 10. Cooling jacket 5 surrounds nozzles 3, and acts as a cooling jacket therefor, as well as a cooling jacket for nozzle 4. Dust gasification chamber 1 is bounded by refractory walls 2. The dust gasifier of Figure 3 can be utilized in the apparatus combination disclosed in Figure 1, rather than the dust gasifier of Figure 2. The dust gasifier of Figure 3 comprises a conically shaped gasification chamber '21, having fueldust-oxygen suspension inlet nozzles 23, connected with fuel dust-oxygen supply pipes 35, and an annular steam nozzle 24, having the shape of a venturi and surrounding the fuel dust-oxygen inlet nozzle 23, and being connected with steam passages 32 and 31. Annular steam nozzle 24 is surrounded by an annular cooling jacket 26, having a cold water inlet 27, and a hot water outlet 29. The inner walls of nozzle 24 cooperate with cooling jacket 36, around the fuel dust-oxygen nozzles 23, so that such cooling jacket 36, around nozzles 23, acts as a cooling jacket for steam nozzle 24, as well as for fuel dustoxygen nozzles 23. Cold water is supplied to cooling jacket 36, through line 33, and hot water is removed through line 34. The coal-oxygen nozzles 23, with their surrounding cooling jacket 36, protrude into the conically shaped chamber 21, beyond the end wall thereof and beyond steam nozzle 24, to permit laminar flow, in substantially segregated streams, of steam issuing from nozzle 24, and of fuel dust and oxygen suspension issuing from -nozzles 23. Furthermore, the shape of nozzle 24. as Well as its positional relationship with respect to fuel dustoxygen nozzles 23, and the reaction chamber 21, is such as to cause a flow of steam into the reactor in a direction ranging from divergent from to parallel to the axis of flow of fuel dust and oxygen suspension into conical chamber 21. This is also true'of nozzle 4, with respect to nozzle 3, and chamber 1, in Figure 2. Dust gasification chamber 21, of Figure 3, is bounded by refractory walls 22.

'Figure 4 discloses yet another embodiment of the present invention. Dust gasifier 73, having steam line 61, oxygen line 62, and finely-divided fuel line 63, is connected-with-secondary gasifier and carbonizer 67, having .a lump coal; feed hopper-64, connected thereto through :feeder 65, a residue outlet 75, a make gas outlet 66, a rotating grate '11 supported onshaft 101 and flush steam inlets 72, distributed along the bottom.

In the-modificationshown-in Figure 5,-gas outlet- 46 9 is positioned adjacent coal feed bin 47 between the bin 47 and dust gasifier 40.

Exar; ple

A high volatile bituminous coal with a moisture content of 4% and pulverized so that 80% passes through a 200 mesh sieve is suspended in cubic feet of oxygen per pound of pulverized coal, and the suspension fed, at p. s. i. pressure, through pipes 35, and nozzles 23, into gasiiication chamber 21, in the form of a jet. Reaction chamber 21 has been previously heated to ignition temperatures of the coal-oxygen suspension, so that the coal and oxygen suspension, as it is jetted from nozzles 23, into gasification chamber 21, ignites and burns in a primary combustion zone within reactor 21. Steam, preheated to 950 F., at a rate of 0.2 lb. per pound of pulverized fuel, is fed through passages 31 and 32, and nozzle 24, into chamber 21. The comparative rates of flow of steam and coal-oxygen suspension, together with the particular design of the apparatus, causes the steam to issue from nozzles 24, in a direction ranging from parallel to, to divergent from, the axis of the coal-oxygen flow into the reactor, so that the steam flows along, around, and outside of the outer periphery of the jet, as it issues into the chamber and ignites and the combustion zone within the chamber, so as to form a continuously, cocurrently flowing envelope or curtain of steam surrounding the periphery of the jet, as it issues into the gasification chamber and ignites and the combustion zone, thereby acting as a protective layer of steam between walls 22, of the reaction chamber 21, and the heat produced in the combustion zone within the chamber. However, as the coal and oxygen burn, the jet expands with a mushrooming effect. The apparatus is so designed that the expanding jet of burning coal and oxygen will diffuse into and with the envelope of steam at completion of burning in the combustion zone, at which point, the hot unreacted carbon issuing from the combustion zone, endothermically reacts with the steam from the envelope in an endothermic reaction zone. The proportion of the coal and oxygen in the suspension introduced through nozzles 23, is such that only a portion of the total amount of oxygen required to convert all the coal to CO is used, the remaining coal being heated to very high temperatures. Water is flowed continuously from pipes 27 and 33, into cooling jackets 26 and 36, respectively, and thence, out through pipes 29 and 34, thus preventing the suspension of coal and oxygen from reaching high temperatures before entering .chamber 21. The gases in chamber 21 reach a temperature of about 3,050 F. and contain mainly CO and H2 with some CO2, dust containing unreacted carbon, and

16 in the products from chamber 21, and steam flowing through bed 44, from inlets 45, to form additional synthesis gases. Heat radiated and conducted from the hot reaction products to the nonpenetrated portion 43, of bed 44, rapidly heats and carbonizes the lump fuel in nonpenetrated portion 43, the volatile matter being volatilized by such carbonization endothermically reacting with steam from inlets 45, as it is flushed from and through nonpenetrated portion 43, of bed 44, into penetrated portion 42, and steam from inlets 45, as well as CO: and unreacted steam contained in the hot reaction products from gasifier 40, as it is flushed through and from penetrated portion 42. The carbonized fuel in nonpenetrated portion 43, reacts with steam from inlets 45, to produce CO and H2. The endothermic reactions occurring in bed 44 reduce the temperature of the exit gases emerging from outlet 46, to 1,650 F. Slag from dust gasifier 40, which is taken up by the solid fuel in bed 44,'moves also to the left, is cooled and solidified within the lump fuel and finally discharged as solid with the solid refuse of the bed through outlet feeder 50, into refuse discharge bin 51, from which the refuse with about 55% carbon content is' removed through line 52. About 92% of the total fuel is gasified. The yield of synthesis gases from 3.6 tons of coal is 280,000 cubic feet corresponding to 39 cubic feet of gas per pound of coal. The obtained synthesis gas from outlet 46, is cooled in a waste heat boiler and direct cooler (not shown). The obtained synthesis gas has the following analysis:

' The gas exit temperatures and the amount of fuel, which unreacted steam. The hot gaseous mixture from chamber 21 is introduced into secondary gasifier and carbonizer 41, so as to impinge upon a portion 49, of the top surface of a fixed bed 44, of 1 to 2 inch lumps of the same coal as was introduced into gasifier 40, moving-from right to left through chamber 41, by means of moving supporting grate 53. Lumps of coal are fed into chamber 41, from bin 47, through feeder 48. From a total feed rate of 3.6 tons of coal per hour, 74% is introduced into gasifier 40, through nozzles 23, in a finely-divided form and 26% is introduced into secondary gasifier and carbonizer 41, as lump fuel through feeder 48. Nine-tenths pound of steam preheated to 950 F. are continuously added through steam inlets 45, per pound of total coal feed. The hot gaseous mixture from gasifier 40, impinging upon portion 49, of bed 44, only partially penetrates the depth of bed 44, and thereafter flows through a penetrated portion 42 of such bed. The lump fuel beneath portion 49 is heated and carbonized very rapidly by the hot impinging products from chamber 21. The volatile matter volatilized by such carbonization and the resulting carbonized lump fuel in penetrated portion 42, as well as unreacted carbon in the hot products from gasifier 40, endothermically reacts with CO2 and undecomposed steam reacts with steam in chamber 41, depends on the size (width and length) of the fuel bed and the feed rates of the various reactants.

In the first zone (dust gasification) an oxygen coal ratio between 7 and 14 cubic feet per pound, preferably 9-12 cubic feet per pound, and a steam coal ratio between 0.1 and 1.0, preferably 0.2 to 0.6 pound per pound is used. The coal size can vary from very fine up to to or more passing a 200 mesh sieve to particles of about A; inch size. Preferred is coal that contains 80% material passing an 80-20() mesh screen. The residence time in this zone is 0.1 to 1.5 preferably 0.2 to 1 second. The ratio of coal feed in zones 1 and 2 (fixed bed) is between 90 to 10 and 40 to 60 preferably between 85 to 15 and 60 to .40 parts by Weight. The solid bed contains more than 10 preferably and more times the amount of fuel fed into zone 1 per second. Utilization of fuel for gasification increases with oxygen coal ratio, ratio of coal feed to zone 1 to that into zone 2, steam preheat temperature and fuel content of the solid bed. The amount of coke or char obtained from zone 2 increases in the opposite direction. The steam added into zone 2 amounts to 0.2 to 1.0 preferably 0.4 to 0.8 pound per pound of total coal feed. The total steam rate is preferably less than 1.2 pounds per pound of total coal feed. The fuel fed into zone 2 is larger than i inch preferably 1 to 4 inches size. It is advantageous to use the fines of run of mine coal if necessary after grinding in zone 1 and the lumps in zone 2, but different coal can be used in both zones. Steam can be saturated. Preferably superheated steam of 500 $62,000 'F., especially '800-1,600 F. is used.

The operating pressure may range from atmospheric to 50 atm., preferably from atmospheric to 30 atm.

Although the specific embodiment of the present invention described above discloses a particular preferred type of dust gasifier, it is pointed out that the present invention includes within its purview the use of any type of dust gasifier" utilizing carbon dioxide or steam and/0r 11 a free oxygen-containing gas as a gasification media, such as fluidized bed gasifiers, vortex type gasifiers, etc., as well as any other type gasifier, wherein the exit gases issue from the gasifier at very high temperatures and contain substantial amounts of carbon-containing dust.

Instead of utilizing steam in the dust gasifier, CO2 or any other chemically combined oxygen-containing fluid capable of reacting endothermically with carbon may be utilized.

Furthermore, instead of pure oxygen, oxygen enriched air may be utilized in the dust'gasifier.

Any type of pulverized carbonaceous fuel may be fed into the dust gasifier, such as lignite, high grade coals, low grade coals, high molecular weight hydrocarbon oils, such as heavy petroleum oils, pitch, tar, etc. Furthermore, hy--. drocarbon gases may be utilized as a fuel feed into the dust gasifier.

Any number of dust gasifiers can be connected with the chamber containing a fixed bed.

Although it is preferable to utilize a hot, dust gasification, gaseous, reaction mixture containing useful gases, any hot combustion gases, produced in any known manner, may be impinged upon the fixed bed of the present invention in the manner described, in order to carbonize and gasify the fuel of such fixed bed.

Although an attempt has been made to describe the theory involved in the present invention, it is not limited to such theory. I

It will be obvious to those skilled in the art that various modifications can be made in the several parts of the present apparatus and the several steps of the present process in addition to those enumerated hereinabove without departing from the spirit of the invention and it is intended to cover in the claims such modifications as are included in the scope thereof.

I claim:

1, A process for producing useful gases comprising carbon monoxide and hydrogen, said process comprising maintaining a fixed bed of moving solid carbonaceous fuel having two surfaces substantially parallel to the direction of movement of said bed, impinging a hot mixture of gaseous products flowing from a gasifierfor gasifying finelydivided carbonaceous fuel with oxygen and steam,- while said mixture is still hot and untreated in any manner, upon a portion of one of said surfaces so as to partially, but not completely, penetrate said bed, simultaneously flowing flush steam through said bed of solid fuel from the other of said surfaces to said surface upon a portion of which said hot mixture is impinged, removing useful gases comprising carbon monoxide and hydrogen from said bed via the same surface upon a portion of which said hot gaseous mixture is impinged and removing solid refuse from said bed.

2. The process of claim 1 wherein the direction of flow of said moving bed is cocurrent with the direction of flow of said hot gaseous mixture along the surface of said bed and through the penetrated portion of said bed.

3. The process of claim 1 wherein the direction of flow of said solid fuel in said bed is countercurrent to the flow of said hot mixture along said surface and through said penetrated portion.

4. The process of claim 1 wherein said bed is moved in a rotating direction by means of a rotating grate.

5. The process of claim 1 wherein at least a part of the fuel in the penetrated portion of said bed is carbonized and at least a portion of the volatile matter driven off gases produced in said bed via the same surface upon a portion of which said hot gaseous mixture is impinged.

7; The process of claim 6 wherein at least a portion of the total non-volatile carbon contained in the solid fuel of said penetrated portion of said bed and in said hot mixture is also gasified during contact of said penetrated portion of said bed with said hot gaseous mixture and said flush steam. v

8. The process of claim 7 wherein at least a portion of the volatile matter driven off from the fuel in the nonpenetrated portion of said bed is gasified during contact with said flush steam in said non-penetrated portion of said bed and with said flush steam and hot mixture in said penetrated portion of said bed.

9. The process of claim 8 wherein at least a portion of the non-volatile carbon in the non-penetrated portion of said bed is gasified during contact with said flush steam in said non-penetrated portion of said bed.

10. A process for producing useful gases comprising carbon monoxide and hydrogen, said process comprising maintaining a fixed bed of moving solid carbonaceous fuel having two surfaces substantially parallel to the direction of movement of said bed, impinging a hot mixture of gaseous products flowing from a gasifier for gasifying finely-divided carbonaceous fuel with oxygen and steam, while still hot and untreated in any manner, upon a portion of one of said surfaces so as to partially but not completely penetrate said bed, simultaneously flowing flush steam through said bed of solid fuel from the other of said surfaces to said surface upon a portion of which said hot gaseous products are impinged, the rate of flow of said moving fuel being controlled so that the volatile matter in said penetrated portion of said bed is volatilized and together with a part but not all of the total nonvolatile carbon content in said penetrated portion of said bed and said hot mixture is gasified by the unreacted steam in said hot mixture.

11. The process of claim 10 wherein the ungasifiable residue in said hot mixture and the ungasifiable residue in said fixed bed is removed in solid form together with the unreacted carbon in said bed.

12. The process of claim 10 wherein a portion but not 7 all of the non-volatile carbon of the non-penetrated portion of said bed is gasified by said flush steam to said useful gases which are thereafter flushed by said flow of flush steam into'said penetrated portion of said bed and thence out of said bed in admixture with other useful gases containing carbon monoxide and hydrogen produced in said bed.

13. The process of claim 12 wherein said finely-divided carbonaceous fuel comprises pulverized coal and said solid carbonaceous fuel of said fixed bed comprises coal.

14. The process of claim 10 in which said hot mixture of gaseous products is produced by burning a jet of finely-divided fuel suspended in a free oxygen-containing gas in a primary combustion zone, peripherally surrounding said jet by a continuously cocurrently flowing envelope of steam, the amount of free oxygen present in said suspension being insuflicient to react with all of the carbon in said fuel, so that only a portion of said fuel is consumed by burning, the remainder of said fuel being rapidly heated in said combustion zone to temperatures favoring reaction of the same to produce carbon monoxide, commingling the products resulting from said burning and flowing from said combustion zone with the steam flowing in said envelope in a secondary endothermic reaction zone to endothermically react substantially all of said remainder of said fuel with said steam.

15. Apparatus for producing useful gases from carbonaceous fuel comprising at least one primary dust gasi fier for gasifying finely-divided fuel with gasification media to produce a hot mixture of reaction products, a secondary gasifier comprising a chamber, means for continuously introducing solid fuel into said chamber, means for continuously moving said solid fuel in the form of a fixed bed having two substantially parallel surfaces through said chamber, an outlet for said primary gasifier for removing said hot mixture therefrom, said outlet being so positioned as to impinge said mixture upon a portion of one of said surfaces of said bed, means for flowing a stream of steam through said moving bed from the other of said surfaces to said surface upon which said hot mixture is impinged and an outlet for said chamber for removing product gases therefrom.

16. The apparatus of claim 15 in which said primary dust gasifier is positioned between said chamber outlet and said means for continuously introducing solid fuel.

17. The apparatus of claim 15 in which said chamber 14 outlet is positioned between said primary gasifier and said means for continuously introducing solid fuel.

18. The apparatus of claim 15 in which said means for continuously moving said solid fuel comprises a rotary 5 grate.

References Cited in the file of this patent UNITED STATES PATENTS 1,964,877 Hereng July 3, 1934 10 2,088,679 Yamakazi et al Aug. 3, 1937 FOREIGN PATENTS 373,835 Germany Apr. 19, 1923 268,480 Switzerland May 31, 1950

Claims (1)

15. APPARTUS FOR PRODUCING USEFUL GASES FROM CARBONACEOUS FUEL COMPRISING AT LEAST ONE PRIMARY DUST GASIFIER FOR GASIFYING FINELY-DIVIDED FUEL WITH GASIFICATION MEDIA TO PRODUCE A HOT-MIXTURE OF REACTION PRODUCTS, A SECONDARY GASIFIER COMPRISING A CHAMBER, MEANS FOR CONTINUOUSLY INTRODUCING SILID FUEL INTOSAID CHAMBER, MEANS FOR CONTINUOUSLY MOVING SAID SOLID FUEL IN THE FORM OF A FIXED BED HAVING TWO SUBSTANTIALLY PARALLEL SURFACES THROUGH SAID CHAMBER, AN OUTLET FOR SAID PRIMARY GASIFIER FOR REMOVING SAID HOT MIXTURE THERFROM, SAID OUTLET BEING SO POSITIONED AS TO IMPINGE SAID MIXTURE UPON A PORTION OF ONE OF SAID SURFACES OF SAID BED, MEANS FOR FLOWING A STREAM OF STEAM THROUGH SAID MOVING BED FROM THE OTHER OF SAID SURFACES TO SAID SURFACE UPON WHICH SAID HOT MIXTURE IS IMPINGED AND AN OUTLET FOR SAID CHAMVER FOR REMOVING PRODUCT GASES THEREFROM.

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