US2805188A - Process for producing synthesis gas and coke - Google Patents

Description

Sept. 3, 1957 M. JOSENHANS PROCESS FOR PRODUCING SYNTHESIS GAS AND COKE Filed Oct. 25, 1952 3 Sheets-Sheet J.

PREHEATED LUMP COAL HOPPER D v/ E 1:: mm R m M DN 1 1;: S m q No H A 2 AI S G Nln 5 E E .n 0 T P L V e f T S U U N S wn s r 1 o s a u M z u 5 9 a L .0 8 X C I, 2 P a o f 2 M US D s g G a n g -7L 7 r l a Y Q R 2 M n Nw A. 0 1 m a 2 5 a a 6 4 fr l I I I I I I I l l |hW|I| Sept. 3, 1957 M. JOSENHANS 2,805,138

PROCESS FOR PRODUCING SYNTHESIS GAS AND COKE Filed on. as, 1952 s Sheets-Sheet 2 PE BBLE ELEVATOR FLUEGAS TO WASTE HEAT born]:

, STEAM FROM STE-AM surznualman s'raem SUPERHEATER & USEFUL GASLS TO l wAs'rz HEAT PRIMARY INVENTOR. Max JosenhcmS United States Patent PROCESS FOR PRODUCING SYNTEESIS GAS AND COKE Max Josenhans, Gibsonia, Pa., assignor to Koppers Company, Inc., a corporation of Delaware Application October 23, 1952, Serial No. 316,451

3 Claims. (Cl. 202-9) 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 and 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 bed water gas machines is produced from coal simultaneously with the production of said useful gases.

Modern chemical industry 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 the various other synthetics, such as are derived from acetylene or other basic hydrocarbons. Therefore, improvements in the production of synthesis gas are of the utmost importance in 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 for use in many of the subsequent synthetic processes must be free from coal tar. The complete removal of tar vapors from the manufactured gas is difiicult and costly. Therefore, provisions have been made to avoid tar formation during gas production. This has been done in two difierent 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-rnine coal are used, operating conditions of gasification are so selected that all tar which might be formed is completely decomposed as formed.

The standard water gas generator is a very well established and satisfactory means for producing synthesis gas. The process avoids tar formation by using coke or char as a raw material, from which all tar has been previously removed. However, this process is handicapped by the fact that the only fuels, which can be used, are relatively expensive. As soon as the coke or char price is above 1.5 times the coal price, the process cannot compete in cost with other gas generating methods, using coal or lignite as raw materials, with steam and/ or oxygen of high purity as reactants for gasification. Such methods comprise what are known, and, hereafter re ferred to in the present specification and claims, as dust gasification methods, wherein very finely-divided pulverized fuel is intimately contacted with gasification media, such as a free oxygen-containing gas or a free oxygencontaining gas and steam, whereby the oxygen exothermically reacts with a portion of the fuel to raise the temperature of the remaining fuel and steam excessively high, at whichexcessively high temperature, the endo thermic reaction of the remainder of the fuel with the steam to form carbon monoxide is favored. Among such dust gasification methods are included gasification of finely-divided fuels in suspension type gasifiers such as vortex type gasifiers, fluidized bed type gasifiers, and

2 gasifiers of the type described and claimed in copending U. S. applications Ser. Nos. 43,950, 43,592, now abandoned, and 43,953, now U. S. Patent No. 2,670,280,

filed August 12, 1948,'U. S. application Ser. No. 131,008,

now abandoned, filed Dec. 3, 1949, U. 8. application Ser. No. 226,792, filed May 17, 1951, and U. S. application Ser. No. 241,413, filed Aug. 11, 1951, now U. S. Patent No. 2,751,286, all wherein a jet of finely divided fuel suspended in oxygen 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 hot 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 intensive burning of' the fuel-oxygen suspension, causes the tar contained in the fuel to bedecomposed and gasified to form useful gases containing carbon monoxide and hydrogen.

However, such dust vgasification or suspension gasification'methods have certain disadvantages in that,

1. It is difiicult, if not impossible, to force the endothermic steam-carbon reaction to the degree of completion required to consume substantially all the finelydivided fuel and to obtain sufiiciently'cooled exit gases,

1 under conditions of gasification in presently known types of dust gasification equipment. Thus, the off-gases are exceedingly high in temperature and contains a considerable amount of unreacted steam (reactant steam and steam formed during the dust gasification), as well as dust, containing, in addition to ash, considerable amounts of unreacted carbon. However, such dust is too poor in carbon to be commercially utilizable as a fuel, and so the carbon contained therein is wasted, in addition to the unreacted steam, thus reducing the efiiciency of the gasifier.

2. Pure oxygen or oxygen enriched air must be utilized for the gasification, which is very expensive. However, unless oxygen or oxygen enriched air is utilized, the required high temperatures cannot be obtained in the gasifier.

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. Such heat is produced by fuel and relatively expensive oxygen consumption, thereby increasing operation costs.

4. The eflicient removal of liquid slag, produced at the high temperatures required during the gasification, is very difiicult, especially, when the dust gasification is carried out at increased pressures.

Such liquid slag is very corrosive and causes rapid equipment deterioration if not efliciently 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 less fuel is-required with less oxygen and less steam to produce more synthesis gases, containing less carbon-containing dust and less unreacted steam than any process or apparatus known heretofore.

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 as a starting material for standard water gas generators, is produced from coal or coke simultaneously with and in cooperation with the above mentioned more eflicient production containing solid fuel of the size utilized in standard watera finely-divided, carbonaceous fuel with achemically con bined oxygen-containing 'fluid capable of reacting endothermically with thefi'nely-divided fuel, such as steam, and avfree oxygen-containing gas, introducing the reaction products from such dust gasifi'er, whilestill hot, into afixed bed of moving-solid, carbonaceous fuel, flowing such hoti reaction products cocurrentlywith the flow of the moving, solid, carbonaceous fuel' in. the. fixed bed, separating the refuse flowing from such fixed bed from useful gases admixed therewith.

The apparatus, in which the foregoing processof the present invention-is carried out, comprises, a dust gasifier having means for flowing therein reactants, and means for flowing therefrom hot reaction products, a secondary gasification chamber connected at one of its ends with the dust gasifier outlet means, sothatthe hot 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 same one end of said chamber and for maintaining a fixed bed of moving said solid fuel in said chamber, means for cocurrently flowing the hot dust gasification reaction products and the carbonaceous fuel in said fixed bed together, from the above mentioned one end of such secondary gasification chantber, to the other end of such chamber, where refuse and useful gases are separated and then removed or removed and then separated.

According to applicants present invention, hot reaction products, containing CO2, HzCO and unrcacted carbon and steam issuing from known types of dustgasifiers, are introduced into a moving bed of solid, carbonaceous fuel and are flowed cocurrently with such moving bed of fuel througha secondary gasifier, wherein gasification of the unreacted carbon-inthe dust gasification products as well as volatilization and gasification of the volatile matter inthe fuel, if such fuel contains volatile matter, as well as gasification of at least a part of the non-volatile portion of the fuel in the bed occurs with the unreacted steam and carbon dioxide in the dust gasification reaction products, the high. temperatures and large quantities of sensible heat in the dust gasification reaction products, providing the required endothermic heat of gasification in the secondary gasifier, the withdrawal of such heat by the endothermic volatilization and gasification in the secondary gasifier, resulting in comparatively cool refuse and gases issuing from the secondary gasifier.

The unreacted carbon and steam contained in the not products issuing from the dust gasifier directly into the fixed bed of fuel commingle with the high carbon-containing 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 and the turbulence caused by the contact of the gases with the lumps of the fixed bed, increases reaction between carbon (the unreacted carbon from the dust gashier plus the carbon contained in the fuel of the fixed bed) and unreacted steam as well as any carbon dioxide in the dust gasifier reaction products. 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 are introduced, to very efiicient gasification temperatures, high enough to decompose any tar or other volatile matter given oh? by the 4 carbonaceous fuel due to the application of heat thereto, in such cases where such fuel contains such tar or volatile matter. As the moving fuel of the fixed bed and the dust gasifier reaction products flow cocurrently away from the point of introduction of such dust gasification products into such bed, they are cooled due to the endothermic reactions occurring: inthe fixed bed between the steam and carbon dioxide and the carbon, so that the solid refuse and gases finally'removedfrom 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 fuel being consumed to produce the same: amount of synthesis gas, while at the same time the unreacted materials (carbon and steam) contained therein, are substantially completely reacted or rendered commercially utilizable. Thus, less oxygen, steam, and pulverized fuel are required, thereby reducing the cost of operation. considerably. Furthermore, dust gasification" capacity is increased considerably, thereby, requiringless dust gasification equipment for the same gas output. Furthermore, at the same time, Hz and C0 are produced in the solid bed reactor Without the expense of additional oxygen or steam.

The carbon content of the refuse removed from the moving fixed bed depends upon. the rate of flow of the carbonaceous fuel of the fixedbed, thelength of said bed, the temperature and rate of how of the hot dustgasification reaction products.

The contact or residence timeof the hot reaction products with the solid fuel, in the bed. can be controlled by controlling the rates of flow of. the fuel of the bed and the hot dust gasification reactionproducts, as Well as the length of the bed, so that. practically all of the carbon content of the carbonaceous fuel in the fixed bed as well as the unreacted carbon in the reaction products from the dust gasifier are consumed, leaving only liquidslag containing small amounts of carbon dissolved therein. However, it is muchmore preferred and efficient to control the rates of flow of the fuel of the fixed bed and'the hot dust gasification reaction products, and the length of the bed, so that the solid refuse flowing from the bed contains a suificient amount of carbon-to be utilizable commercially as fuel. In such case, themolten slag produced in the dust gasifier, as well asany slag produced in a fixed bed, is adsorbed and solidified on the solid fuel of the fixed bed, and making its removal in solid form possible. This provides a novel way of slag removal during dust gasifi-cation, especially, when carried out under pressure. Furthermore, the removal of slag in such a manner decreases refractory corrosion in the gasification apparatus due to slag, which isdepositedthereon.

The solid residue, in such case, can. be utilized as a fuel in producing and superheating steam for the: dust gasifier and for drying and preheating fuel for the dust gasification, as well as for preheating fuel for the fixed bed. Although the carbon in the reaction products from the usual dust gasifier is present in too small amounts to be utilized as a fuel, and thus must be Wasted,.the carbon contained in the solid refuse of the present invention can be utilized as a fuel. Hence, substantially none of the carbon is wasted.

. If tar-containing coal is utilized as a fuel for the fixed bed, its rate of flow can be so controlled thatsubstantially only the volatile matter of such coal is volatilized and gasified, the solid residue being suitable as a coke in slagging or non-slugging type gas generators at atmospheric or elevated pressures, or, in standard Water gas, machines, thereby increasing the efliciency of the dust gasification process, while at the same time carbonizing coal to produce coke for standard water gas machines. Undersized particles of this solid refuse can be recycled and used as a fuel for the dust gasification step while a part of the lump char may be recycled and introduced into the secondary gasifier. Furthermore, since, in such cases, it is desirable to have high fixed bed fuel rates, capacity is increased. It is pointed out that it is the cocurrent flow of dust gasification reaction products and the fuel of the fixed bed, which makes possible the use of tar-containing fuels for the fixed bed, without caking occurring in the bed with resultant high pressure drops, and without contamination with tarry matter of the useful gases produced in and passed through such bed.

Fig. l, diagrammatically discloses an embodiment of the present invention, applied to a dust gasifier of the type described in the above mentioned copending applications and more fully disclosed, in cross-section, in Figures 3 and 4.

Fig. 2, diagrammatically discloses yet another embodi ment of the present invention applied to a dust gasifier of the type described in the above mentioned copending application and more fully disclosed in cross-section, in Figures 3 and 4.

Fig. 3 discloses in vertical cross-section the dust gasifier of Figures 1 and 2.

Fig. 4 discloses, in vertical cross-section, another type of dust gasifier, which can be utilized in Figures 1 and 2.-

According to Fig. 1, a plurality of dust gasifiers 40, are located circumferentially around the top of secondary gasifier 44, so that hot reaction products flowing from such dust gasifiers, flow into a fixed bed of solid fuel 41, such as lump coal, flowing downwardly through such secondary gasifier. A solid fuel hopper 51, is located on top of the secondary gasifier and a conduit 52, and feeding valve 50, is provided for continuously feeding preheated solid fuel from hopper 51, into the top of secondary gasifier 44. The hot reaction products from reactors 40, containing carbon monoxide, carbon dioxide, hydrogen, and unreacted carbon particles and steam, flow cocurrently with the flow of solid fuel of the fixed bed, in intimate contact therewith, downwardly, through secondary gasifier 44, during which time, the coal is devolatilized and endothermic gasification of unreacted carbon in the reaction products from the dust gasifier 40, the volatile matter from the coal, and, if desired, according to the rate of flow of solid fuel through the secondary gasifier,

some of the devolatilized fuel in the fixed bed, occurs with the carbon dioxide and unreacted steam present in the dust gasification reaction products, to form useful gases containing carbon monoxide and hydrogen. The dust gasifier reaction products are simultaneously cooled by more than 1000 F. Make gas outlet 47, is provided at the bottom of the secondary gasifier 44, for removal of make gases containing carbon monoxide and hydrogen. Residue coke is removed from the fuel bed by means of cooled grate 48, and leaves the gasifier by means of feeder 49, and conduit 42. If desired, the solid residue can be cooled by water spray 53. Dust gasifiers 40, are of the type described in copending U. S. application Ser. No. 241,413. With reference to Figures 3 and 4, each respectively of such gasifiers comprises a conically shaped gasification chamber 1 or 21, having fuel dust-oxygen- suspension inlet nozzles 3 or 23, connected with fuel dust-oxygen suspension supply pipes 14 or 35, and annular steam inlet nozzle 4 or 24, having a venturi shape and surrounding the fuel dust- oxygen inlet nozzles 3 or 23, and being connected with steam passage 11 or 31 and steam distribution passage 12 or 32. The outer walls of annular nozzle 4 are surrounded by an annular cooling jacket 6 or 26, having a cool water inlet 7 or 27, and a hot water outlet 9 or 29. The inner walls of nozzle 4 or 24, have a second cooling jacket 5 or 36, cooperating therewith, having a cold water inlet 8 or 33, and a hot water outlet 10 or 34. The cooling jacket 5 or 36, surrounds nozzles 3 or 23, and acts as a cooling jacket therefor, as well as a cooling jacket for nozzle 4 or 24. The dust gasification chamber 1 or 21 is bounded by refractory walls 2 or 22.

Fig. 2 discloses yet another embodiment of the present invention, wherein a plurality of dust gasifiers 40, shown. in cross-section, in Figures 3 and 4 and described above,

are located circumferentially around the top of secondary gasifier 68, so that hot reaction products flowing from 1 feeder 72, through which hot residue coke is flowed into a blower 74, having a primary air inlet 73, for blowing such hot coke refusethrough line 75, and inlet 76, to refuse furnace 77, into which secondary air for completely burning such refuse is admitted through inlet 80. Ash is removed from refuse furnace 77, through feeder 78, and line 79. Hot flue gas lines 93 and 81, connect refuse furnace 77, with carbonizer 63, through line 67, and with pebble heater 90, through hot flue gas inlet and distribution means 92. Pebble heater 90, has a cooled flue gas outlet pipe 91, leading to a waste heat boiler, not shown, cold pebble bed inlet conduit 89, and hot peddle outlet conduit 94, leading into steam superheater 84. Steam superheater 84, has.

a superheated steam outlet pipe 83 and 82, leading to. the steam inlets of dust gasifier 40, a cold pebble outlet 85, and feeder 87, leading to conduit 95, and pebble' elevator 88, where pebbles are elevated to conduit 89, and a steam inlet pipe 86, leading from the waste heat boiler, not shown. Two suitable types of dust gasifiers 40, leading into secondary gasifier 68, are disclosed in Fgures 3 and 4, and have been described above.

Example Utilizing the apparatus of Figures 1 and 4, high volatile,

bituminous coal dried to 2.5% of water, ground so that 62% passes through a 200 mesh sieve is fed, together and in suspension with substantially pure oxygen in the ratio of 12.5 cu. ft. of oxygen per lb. of coal, into fuel-oxygen pipes 35, and, thence, into nozzles 23, from which such suspension of coal and oxygen are jetted into reactionreaction chamber 21, ignites and burns while flowing through a primary combustion zone in reaction chamber 21. The proportions of coal and oxygen are such that.

there is suflicient oxygen only to burn a portion, but not all of the coal to carbon monoxide. The heat generated by such burning heats the unburned remaining portion of coal to temperatures favoring reaction of the same with steam and oxygen to produce carbon monoxide and. hydrogen.

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 coaloxygen suspension from becoming too hot before entering chamber 21. Due to the partial combustion in the combustion zone, a reaction temperature of 3050 F. is obtained in reaction chamber 21. Simultaneously with the injection of the coal/ oxygen mixture into the reaction chamber 1.1 lbs. of steam superheated to 1500 F. are.

A car-' the end of combustion in the combustion zone, the products of combustion as Well as the hot unreacted carbon diffuse into the steam from the envelope and endothermic reactions occur in an endothermic reaction zone within the reaction chamber. Hot reaction products issue from.

the reaction chambers 21-, into the top of secondary gasifier 44, which contains a solid bed of /1 to 2' inch lumps of coal of the same type utilized in the coaloxygen suspension, having about 900 lbs. of coal per lb. of finely-dividedcoal fed per second into the dust gasifier. Such solid bed of lump coal is moving constantly downward and the hot reaction product gases from the dust gasifiers move cocurrently and downwardly with such moving coal bed. Lump coal is fed from hopper 51, feeder 50, and conduit 52, into the top of secondary gasifier 44, at the rate of 0.43 lb. of coal per lb. of coal fed into the dust gasifiersif This lump coal is rapidly carbonized on top of the fuel bed, where the hot gases from chambers 21, at temperatures of from 2,200 F. to 2,600 F. and above, are first contacted-therewith, and the volatile matter (tar, etc.) is practically completely converted into CO, H2 and CO2. In the coal bed, the unreacted carbon in the dust gasification reaction products from chambers 21, is retained and reacts with carbon dioxide and unreacted steam contained in the reaction products. Furthermore, the coal is volatilized and the volatile matter is gasified by the carbon dioxide and unreacted steam in the reaction products. Furthermore, depending on the rate ofiiow of coal and reaction products, the length of the bed and, thus, the contact time of the hot product gases with the bed, a part of the-carbon in the carbonized coal may or may not react with the carbon dioxide and unreacted steam. The high temperature of the product gases, as they contact the coal bed, heat the bed to suficient temperatures for these reactions and volatilization to occur. Hot make gases are removed at 47, and the solid residue is removed by Water cooledgrate 48, feed 49, and conduit 42. The height of the bed and the rate of'fiow'of solid fuel through the bed and, thus, the contact time of the hot reaction prodnets with the solid fuel of the bed is regulated by feeder 49, Which may be astar-valve or any other known typei The solid residue issuing'from 42,'is

41 cu. ft., having the following analysis: CO26.87%,.

CO51.4%, Pia-39.1%, N2+H2S2.7%. The reaction product gases from the dust gasifier, while flowing from the top of the fixed bed to the bottom of the fixed bed, cocurrently. with the coke, are cooled about l,300 F. by the endothermic reactions occurring in the bed, which endothermic reactions produce additional carbon monoxide-and hydrogen. The temperature of the gases, in line 47 is about 1,300 F. The make gases are led from line 47 to a cyclone separator for dust removal and thence to a waste heat boiler and direct cooler.

' If the apparatus of Figure 2 is utilized, lump coal is fed from hopper-6G, through feeder 61, and conduit 62, into carbonizer 63, where it is carbonized by hot flue gases introduced through line 67 and distributor 66. The volatile matter drawn off from the coal during carbonization escapes through line 65, and is led to a. tar recovery unit, not shown. Coke iiows from carbonizer 63, throughline 69, to secondary gasilier 63, in which it forms a fixed bed 70, ofjcoke moving cocurrently with hot, reaction product gases from dust gasifiers 4:0., producedinthe manner described above.

indiscussing'Figure l-. Useful gases are removed at 71, and hot refuse flows through feeder 72, to blower 74, into which-primary airis introduced from line:73. The primary air blows the refuse along line 75 and inlet- 76, to refuse furnace 77,'where secondary air is introduced through line Slhto completely burn such refuse to ash, which 'is removed through feeder 78, and 79. The hot flue gases formed in 77, are flowed throughline 8i and 93, to pebble-heater Maud inlet 67 of carbonizer-63 respectively; The-flue gas flowing to line 67, through line 93, is used to carbonize coal in carbonizer 63, while the line gas flowing to'pebbl'e heater V9.0,- through lines 81 and"distributor 92 is used to heat pebbles introduced into pebble heater from line 89." The spent flue gas is removed. from pebble heater. 98,-. through line $1 from whence it is flowed to a waste heat boiler. The hot pebbles fiow through conduit 93, to--'steam superheater 84, where they are contacted with steam. from 86, to superheat such steam. The superheated steam is flowed from steam superheater 84, through lines 82; to steam inlets 3f, (Figure'4) of the dust gasifiers 4i Spent pebbles are removed from steam superheater 84, through line 85, feeder 87-, and line 93 and are recycled to pebble heater 90;.to be reheated by'means of-pebble elevator 88, andline 89: It may be seenthat by utilizing the apparatus of Figure 2, all-the heat for producing steam and carbonized fuel for the-proce'ss; is o-btainedfrom the refuse removedfronr thesecondarygasifier.

Coke or other solid fuels, such as anthracite, bitumi nous, andv rnn-of-the-mine. coal, aswell as char and low temperature coke, can-be used as solid fuel for the secondary gasifier.

Usually, the. solids are fed into the top of the sec.- ondary gasifier andspent solids are removedat the bottom, so that the. solid fuel and. reaction products flow downwardly. However, solong as thefiow of hot reactiongases and the. fuel of the fixed. bed is cocurrent, it is not necessary that the flow befrom top ot bottom.

The residence time-in the dust gasifier should be sufficient to permit essentially complete consumption of the oxygenintroduced Withthe finely-divided coal or lignite. Aresidencetime below 1.2. seconds, preferably below 0.5 to-0.8 secondand. above 0.05 to 0.1 secondis sufficient. These residence times apply to gasification at atmospheric pressure... The processucan be used advantageously at higherpressuresup to about atmospheres, preferably at 5 to 20 atmospheres.- The residence time in this case has to be,inc reased,,roughly with the square root of the pressure.

V The amount ofoxygen used should permit gasification of atleast 50. to of the carbon of the coal, preferably. between 7O to 85%. For this to occur, oxygencoal ratios above 7' cu. ft. pcrvlb. of coal, preferably between 8 and 11 cu. ft.-of oxygen per lb. of coal, fed into the dust gasifiers are suitable.

The rate of steam flow into the dust gasifiers preferably ranges from 0.7 lb. to 1.1 lbs. of coal fedinto the dust gasifier."

For the, production of carbon monoxide and hydrogen-containing synthesis. gas, essentially pure oxygen is used. For ammonia synthesis gas, containing nitrogen, suitable mixtures of oxygen with air can be chosen.

The water. content of thefinely-divided coal should be below 5%. 7

Coal is ground, so that it can be fed in a. suspension with oxygen. Particlesbelow A3 in. are suitable. More finely ground. coal, for example 5.0 to passing through a 200 mesh sieve ispreferred. It permits use of residence times in the dust gasifiers near the lower limit given above.

' The-residence or contact-time of reaction gases in the secondary gasifier can be decreased with increase of average temperatures, the amount of carbon present and cases, it is desirable to have high fixed bed fuel rates, capacity is increased. It is pointed out that it is the cocurrent flow of dust gasification reaction products and the fuel of the fixed bed, which makes possible the use of tar-containing fuels for the fixed bed, without caking occurring in the bed with resultant high pressure drops, and without contamination with tarry matter of the useful gases produced in and passed through such bed.

Fig. 1, diagrammatically discloses an embodiment of the present invention, applied to a dust gasifier of the type described in the above mentioned copending applications and more fully disclosed, in cross-section, in Figures 3 and 4.

Fig. 2, diagrammatically discloses yet another embodiment of the present invention applied to a dust gasifier of the type described in the above mentioned copending application and more fully disclosed in cross-section, in Figures 3 and 4.

Fig. 3 discloses in vertical cross-section the dust gasifier of Figures 1 and 2.

Fig. 4 discloses, in vertical cross-section, another type of dust gasifier, which can be utilized in Figures 1 and 2.

According to Fig. 1,- a plurality of dust gasifiers 40, are locatedcircumferentially around the top of secondary gasifier 44, so that hot reaction products flowing from such dust gasifiers, flow into a fixed bed of solid fuel 41, such as lump coal, flowing downwardly through such secondary gasifier. A solid fuel hopper 51, is located on top of the secondary gasifier and a conduit 52, and feeding valve 50, is provided for continuously feeding preheated solid fuel from hopper 51, into the top of secondary gasifier 44. The hot reaction products from reactors 40, containing carbon monoxide, carbon dioxide, hydrogen, and unreacted carbon particles and steam, flow cocurrently with the flow of solid fuel of the fixed bed, in intimate contact therewith, downwardly, through secondary gasifier 44, during which time, the coal is devolatilized and endothermic gasification of unreacted carbon in the reaction products from the dust gasifier 40, the volatile matter from the coal, and, if desired, according to the rate of flow of solid fuel through the secondary gasifier, some of the devolatilized fuel in the fixed bed, occurs with the carbon dioxide and unreacted steam present in the dust gasification reaction products, to form useful gases containing carbon monoxide and hydrogen. The dust gasifier reaction products are simultaneously cooled by more than 1000 F. Make gas outlet 47, is provided at the bottom of the secondary gasifier 44, for removal of make gases containing carbon monoxide and hydrogen. Residue coke is removed from the fuel bed by means of cooled grate 48, and leaves the gasifier by means of feeder 49, and conduit 42. If desired, the solid residue can be cooled by water spray 53. Dust gasifiers 40, are of the type described in copending U. S. application Ser. No. 241,413. With reference to Figures 3 and 4, each respectively of such gasifiers comprises a conically shaped gasification chamber 1 or 21, having fuel dust-oxygen- suspension inlet nozzles 3 or 23, connected with fuel dust-oxygen suspension supply pipes 14 or 35, and annular steam inlet nozzle 4 or 24, having a venturi shape and surrounding the fuel dust- oxygen inlet nozzles 3 or 23, and being connected with steam passage 11 or 31 and steam distribution passage 12 or 32. The outer walls of annular nozzle 4 are surrounded by an annular cooling jacket 6 or 26, having a cool water inlet 7 or 27, and a hot water outlet -9 or 29. The inner walls of nozzle 4 or 24, have a second cooling jacket 5 or 36, cooperating therewith, having a cold water inlet 8 or 33, and a hot water outlet 10 or 34. The cooling jacket 5 or 36, surrounds nozzles 3 or 23, and acts as a cooling jacket therefor, as well as a cooling jacket for nozzle 4 or 24. The dust gasification- chamber 1 or 21 is bounded by refractory walls 2 or 22.

Fig. 2 discloses yet another embodiment of the present in cross-section, in Figures 3 and 4 and described above,

are located circumferentially around the top of secondary gasifier 68, so that hot reaction products flowing fromsuch dust gasifiers flow into a fixed bed of coke 70, flowing downwardly through such secondary gasifier. bonizer 63, is located above the secondary gasifier, such carbonizer having a fresh coal hopper 60, feeder 61, and inlet 62, a carbonized coal and coke outlet feeding into passage 69, which leads into secondary gasifier 68, an outlet 65, for removal of volatile matter and a hot'flue gas inlet 67, and distributor 66. Secondary gasifier 68, has a useful gas outlet 71 and residue coke outlet and feeder 72, through which hot residue coke is flowed into a blower 74, having a primary air inlet 73, for blowing such hot coke refuse through line 75, and inlet. 76, to refuse furnace 77, into which secondary air for completely burning such refuse 'is admitted through inlet 80. Ash is removed from refuse furnace 77, through feeder 78, and line 79. Hot flue gas lines 93 and 81, connect refuse furnace '77, with carbonizer 63, through line 67, and with pebble heater 90, through hot flue gas inlet and distribution means 92. Pebble heater 90, has a cooled flue gas outlet pipe 91, leading to a waste heat boiler, not shown, cold pebble bed inlet conduit 89, and hot peddle outlet conduit 94, leading into steam superheater 84. Steam superheater 84, has a superheated steam outlet pipe 83 and 82, leading to the steam inlets of dust gasifier 40, a cold pebble outlet 85, and feeder 87, leading to conduit 95, and pebble elevator 88, where pebbles are elevated to conduit 89,

and a steam inlet pipe 86, leading from the waste heat boiler, not shown. Two suitable types of dust gasifiers 40, leading into secondary gasifier 68,.are disclosed in Fgures 3 and 4, and have been described above.

Example Utilizing the apparatus of Figures 1 and 4, high volatile, bituminous coal dried to 2.5% of water, ground so that 62% passes through a 200 mesh sieve is fed, together and in suspension with substantially pure oxygen in the ratio of 12.5 cu. ft. of oxygen per lb. of coal, into fuel-oxygen pipes 35, and, thence, into nozzles 23, from which such suspension of coal and oxygen are jetted into reaction chamber 21, which has been previously heated to the ignition temperatures of the oxygen-coal suspension. The suspension of coal and oxygen, upon being jetted into reaction chamber 21, ignites and burns while flowing through a primary combustion zone in reaction chamber 21. The proportions of coal and oxygen are such that there is sufficient oxygen only to burn a portion, but not all of the coal to carbon monoxide. The heat generated by such burning heats the unburned remaining portion of coal to temperatures favoring reaction of the same with steam and oxygen to produce carbon monoxide and hydrogen.

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 coaloxygen suspension from becoming too hot before entering chamber 21. Due to the partial combustion in the combustion zone, a reaction temperature of 3050 F. is obtained in reaction chamber 21. Simultaneously with the injection of the coal/oxygen mixture into the reaction chamber 1.1 lbs. of steam superheated to 1500 F. are admitted through steam passages 31 and 32, and steam nozzles 24, per lb. of coal admitted through coal-oxygen nozzles 23. 'The steam, due to the rate'of flow of such steam compared to the rate of flow of the coal-oxygen suspension, as well as the design of chamber 21, and nozzles 23 and 24, issues into the chamber in the form of a cocurrently, contiuously flowing annular stream, completely enveloping the outer periphery of the jet of coal and oxygen as it issues into the reaction chamber A carand .ignites and theouter periphery of the combustion zone; Theannular streamofsteam, flowing inadirec the reaction chamber. Hotreaction products issue from.

the reaction chambers 21, into the top of secondarygasifier 44, which contains a solid bed of to- Z'inch lumps of'coal of the same type utilized in the coaloxygen suspension, having about 900 lbs. of coalperlb. of finely-dividedicoal fedper'second-into the dust gasifi'er. Such' solid bed of lump coal ismovingconstantly down- Ward and the hot reaction-product gases-from the dust gasifiers move cocurrently and downwardly with such moving coal bed. Lump coal is fed from hopper 51, feeder 50, and conduit 52, into the top of secondary gasifier 44, at the rate of 0.43 lb. of coal per lb. of coal fed into the dust gasifiers.. This lump coal is rapidly carbonized on topof the fuel bed, Where the hot gases from chambersll, at temperatures of from 2,200 F. to 2,600? P. and above, are first contactedtherewith, and the volatile matter (tar, etc.) is practically completely converted into CO, H2 and CO2. In the coal bed, the unreacted carbon in-the dust gasification reaction products from-chambers 21, is retained and reacts with carbon dioxide and unreacted steam contained in the reaction products. volatile matter is gasified by the carbon dioxide and unreacted steam in the reaction products. Furthermore, depending on the rate of flowof: coal and reaction products, the length of the bed and, thus, the contact time of the hot product gases with the bed, a partof the carbon inthe carbonized coal may or may not react With the carbon-dioxide and-unreacted steam. The high temperature of the product gases, as they contact the coal bed, heat the bedto sufiicient temperatures for'these reactions and volatilization to occur. Hot make gases are removed at 47, and the solid residue is removed by water cooledgrate 48, feed 49, and conduit: 42; The height of the bed and the rate of flowof solid fuel through the bed and, thus, the contact time of the hot reaction productswith the solid fuel of the bed is regulated by feeder 49, which may be a star valve or any other knowutype' The solid residue issuing'f'ronr 42, is"

product gases from the dust gasifier, while flowing from the top of the fixedbed' to thebottomof thefixed'bed, cocurren-tlywith'the coke, are cooled-about 1,300" F. by

the'endothermic reactions occurring in the bed, which.

endothermic reactions produce additional carbon monoxide and hydrogen. The temperature of the gasesin line 47 is about 1,300 F. The make gases are led from line 47 to a cyclone separator for dust removal and thence to a waste heat boiler anddirect cooler.

If the apparatus of Figure 2 is utilized, lump coal is fed from hopper 60, through feeder 6i, and'conduit 62, into carbonizer 63, where it is carbonized by hot flue gases introduced through line 67 and distributor 66. The volatile matter drawn off from thecoal dur ing carbonization escapes through line 65, and is led to a. tar recovery unit, not-shown. earbonizer 63; through line 69, to secondary gasifier 6.8,.in which itforms a fixed beditl, of coke moving Furthermore, the'coal is volatilized and the Coke flows fromcocurrently with hotreaction product gases fromdust gasifiers 40', produced. inthemanner described above:

in discussing figure. 1; Usefulgases. are removed at 71, and'hot refusefiows through feeder, 72, to blower-74,

' into whichprimary air is introduced from'line=73. The. primaryair: blowsythe refuse:along line-75 and inlet 76,

to refuse furnace 77,,where secondary air, is introduced. throughiline to completely burn such refuseto'ash, which is removed through-feeder73, and 79'. Thehot flue gases formedin 77, are'fiowed through line 8-1 and 93, to pebble heater 9ti-and inlet 67' of carboniZer-63 respectively. The'flue gas flowingto line 67, through line 93, is used to carbonize coal in carbonizer. 63, While the flue gas flowing; to, pebble- :heater;9tl; through; lines' Sl and distributor 92 is: used to heat pebbles introduced into pebbleheaterfrom. line;89. Thespent flue gas is removed. from pebble; heater 90, through line- 91- from whence it is flowed to a waste heat boiler. The hot pebbles; flow throughwonduit. 93, to. steam superheater 84, where they are contacted with steam from 86, to super-heat such steam.. The superheated-steam isfiowed from-steam superheater' 84-, through lines 82; to steam inlets 31, (Figure 4) of the-dust gasifiers 40. Spent pebbles are removed fromsteam-superheater 84, through line 85, feeder S7,.andline 93and are recycled to pebble heater 90; to be reheatedby means-of-pebble elevator 88, and line 89; It maybe seen-thatby-utilizing the apparatus of Figure 2,. all theheatfor producing steam and-car.- bonized fuel for the=process, isobtained from the refuse removed from: thesecondary gasifier.

:Coke. or otherv solid fuels, such asanthracite, bituminous, andJUn-Qf-the-mine coal, as .well as char and low' temperaturecokq:can:be used as solid fuel forthe secondary. gasifier.

Usually, the. solids: are fed intothe top. of the sec.- ondary gasifier. and. spent solids. are removed .at the bottom, sothatthe. solidfuel. and. reaction products How downwardly. However, solong as the flow of. hot reactiongases and therfuel of thefixedbed is cocurrent, it is not. necessary. that theflow be from top 0t bottom.

The residencetimedn the dust gasifier should be sufficient to permit essentially complete consumption of the oxygen introduced. withthe finely-divided coal, or llgnite. A.residence.-tirne below 1.2.seconds, preferably below 0.5 to.0..8 second.and.above.0.05 to.().-1.sec.ond,is suificient. These. residence times apply to gasification at atmospheric pressure. The processcan be usedadvantageously at-higherpressures up to about 40 atmospheres, preferably at 5 tor20 atmospheres. The residencetime in this case has tobeincreased, roughly with the square root of the pressure.

The amount of'oxygen used should permit gasification of at least. SOto 60% of thecarbon of the coal, preferably. between 70 to For this to occur, oxygen coal ratios above 7 cu. ft. per lb. of. coal, preferably between 8 andll cu. ft..of oxygen per lb. of coal, fed into the dust gasifiers are suitable.

The rate ofstearn flow into the dust gasifiers preferably ranges from 0.7"1b. to 1.1 lbs. of coal fed into the dust gasifier.

For the. production of carbon monoxide and hydro.- gen-containing synthesis. gas, essentially pure oxygen is used. For ammonia.synthesis gas, containing nitrogen, suitable mixtures of oxygen with air can be chosen.

The water content of the finely-divided coalv should be below 5%.

Coal is ground, so that it can be fed in. a. suspension with oxygen. Particles .below' /3 in. are suitable. More finely ground. coal, for example 5.0 to 70% passing through a 200mesh sieve is ,preferred. It permits use of residence times in the dust gasifiers near the lower limit given above;

The-residence or contact time of reaction gases in-the secondary gasifier can be decreased with increase of average temperatures, the amount of carbon present and the water and carbon dioxide content of the gases passing through this gasifier. Usually a retention time of gases in the secondary gasifier, depending on the total volume of the secondary gasifier may be from 0.2 to 3 seconds especially 0.4 to 1 second. The amount of carbon present in the secondary gasifier for 1 lb. of coal per second fed into the dust gasifiers should be above 50 lbs., preferably 200 to 1,500 lbs. or more.

The rate of flow of solid fuel into the secondary gasifier is preferably from 0.25 lb. to 0.5 lb. per pound of coal fed into the dust gasifiers.

The steam utilized in the present invention should be superheated to a temperature ranging from 800 F. to 2,000" F., preferably 1,000 F. to 1,600 F.

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 a free oxygen-containing gas or utilizing only a free oxgen-containing gas, or utilizing only steam or CO2, as a gasification media, such as a fluidized bed gasifier, a vortex type gasifier, etc., as well as any other type of gasifier, wherein the exit gases are at high temperatures and/or substantial amounts of carbon-containing dust are present in the off-gases.

Instead of utilizing steam or carbon dioxide, 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.

Any type of pulverized carbonaceous fuel may be fed into the dust gasifiers, such as lignite, high grade coals, low grade coals, high molecular weight hydrocarbon oils, heavy petroleum oils, pitch, tar, etc. Furthermore, hydrocarbon gases may be utilized as a fuel feed into the dust gasifiers, although the present invention is not so suitably adapted to processes wherein such gases are utilized.

Any number of dust gasifiers can be connected with the secondary gasifier, although it is preferred to have more than one.

If desired, steam and/or oxygen may be flowed directly into the fixed bed of solid fuel to increase gasification and temperatures in such beds.

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

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 present 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 synthesis gases, comprising, gasifying, in a dust gasifier, a finely-divided solid carbonaceous fuel with a chemically combined oxygencontaining fluid of the group consisting of the steam and CO2 capable of reacting endothermically with said finely-divided fuel and a free oxygen-containing gas of the group consisting of oxygen and oxygen enriched air, in proportions to produce a hot mixture of synthesis gases, unreacted carbonaceous fuel dust and fluid, filtering said hot mixture through a fixed bed of moving solid carbonaceous fuel while flowing cocurrently with the flow of said moving carbonaceous fuel in said fixed bed, the rate of flow of said moving fuel being controlled, so that only a portion, but not all, of the total carbon contained therein and in said unreacted fuel dust, is consumed to produce synthesis gases during said cocurrent flow of said moving fuel and said mixture, and separating said gases from the ungasified residue.

2; A process as claimed in claim 1 and in which the fuel in said bed is coal, and in which the rate of flow of said moving coal in the bed is controlled, so that the volatile matter contained in the coal is utilized and consumed to produce useful gases during said cocurrent flow, sufiicient carbon remaining in the coke resulting from the coal to permit its use commercially as a source of heat energy and separating said coke from the useful gases admixed therewith.

3. The process of claim 1, wherein said gasification step in said gasifier comprises burning a jet of said finely divided fuel suspended in said gas in a primary combustion zone, which is peripherally surrounded by a continuously, cocurrently flowing envelope of said fluid, said burning being controlled so that the constituents in said combustion zone are rapidly heated to temperatures favoring reaction of said fuel to form carbon monoxide, and so that only part of said fuel is consumed by said 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, including said heated remainder of said fuel, with the fluid flowing from said envelope in a secondary endothermic reaction zone to endothermically react said heated remainder of said fuel with said fluid.

References Cited in the file of this patent UNITED STATES PATENTS 247,333 Gearing Sept. 20, 1881 997,941 Doherty July 11, 1911 1,872,883 Byrne Aug. 23, 1932 2,088,679 Yamazaki et al. Aug. 3, 1937 2,311,140 Totzek et a1. Feb. 16, 1943 2,702,743 Totzek Feb. 22, 1955 FOREIGN PATENTS 288,491 Great Britain Apr. 12, 1928 661,148 Great Britain Nov. 14, 1951 486,354 Canada Sept. 9, 1952

Claims (1)

1. A PROCESS FOR PRODUCING SYNTHESIS GASES, COMPRISING, GASIFYING, IN A DUST GASIFIER, A FINELY-DIVIDED SOLID CARBONACEOUS FUEL WITH A CHEMICALLY COMBINED OXYGENCONTAINING FLUID OF THE GROUP CONSISTING OF THE STEAM AND CO2 CAPABLE OF REACTING ENDOTHERMICALLY WITH SAID FINELY-DIVIDED FUEL AND A FREE OXYGEN-CONTAINING GAS OF THE GROUP CONSISTING OF OXYGEN AND OXYGEN ENRICHED AIR, IN PROPORTIONS TO PRODUCE A HOT MIXTURE OF SYNTHESIS GASES, UNREACTED CARBONACEOUS FUEL DUST AND FLUID, FILTERING, SAID HOT MIXTURE THROUGH A FIXED BED OF MOVING SOLID CARBONACEOUS FUEL WHILE FLOWING COCURRENTLY WITH THE FLOW OF SAID MOVING CARBONACEOUS FUEL IN SAID FIXED BED, THE RATE OF FLOW OF SAID MOVING FUEL BEING CONTROLLED, SO THAT ONLY A PORTION, BUT NOT ALL, OF THE TOTAL CARBON CONTAINED THEREIN AND IN SAID UNREACTED FUEL DUST, IS CONSUMED TO PRODUCE SYNTHESIS GASES DURING SAID COCURRENT FLOW OF SAID MOVING FUEL AND SAID MIXTURE, AND SEPARATING SAID GASES FROM THE UNGASIFIED RESIDUE.

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