US2682457A - Gasification of carbonaceous solid fuels - Google Patents

Description

June 29, 1954 E. GORIN GASIFICATION OF CARBONACEOUS SOLID FUELS 4 Sheets-Sheet 1 Filed June 16, 1949 mmbwmumm INVENTOR EVERETT GORIN TEMPERATURE ('E) ATTORNEY June 29, 1.954 E. GORIN GASIFICATION 0F CARBONACEOUS SOLID FUELS 4 Sheets-Sheet 2 Filed June 16, 1949 TPRODUGT GAS MIXER .4 ":aTEAM 224 i AIR FIG. 2

'INVENTOR EVERETT GORIN BY BMW? ATTORNEY June 29, 1954 E. GORIN 2,682,457

GASIF'ICATION OF CARBONACEOUS SOLID FUELS Filed June 16, 1949 4 Sheets$heet 3 J2 PRODUCT GAS CHAR CRUSHING 88 GRINDING 50 (WATER SIEVING EQUIPMENT 9a 0 GD T A 62 I62 AIR a INVENTOR FIG. 3 EVERETT GORIN BY xwyq.

TTORNEY June 29, 1954 0 E. GORIN 2,682,457

GASIFICATION OF CARBONACEOUS SOLID FUELS Filed June 16, 1949 4 Sheets-Sheet 4 STEAM WATER PRODUCT 05 GAS 20? WA ER MR 251 2 24s z 2 0 w 240 z 2 00 V o o 2|4 STEAM E S M 232 ASH m 234 209 AIR 234 INVENTOR FIG. 4

EVER ETT GORIN ATTORNEY Patented June 29, 1954 UNITED STATES PATENT OFFICE GASIFICATION F CARBONACEOUS SOLID ELS Application June 16, 1949, Serial No. 99,563

2 Claims.

This invention relates to the gasification of carbonaceous solid fuels, and, more particularly, to methods of and apparatus for reacting carbonaceous solid fuels with steam.

The present application is a continuation-inpart of my copending application Serial Number 58,132, filed November 3, 1948, and now abandoned.

The primary object of this invention is to provide a new process for converting carbonaceous solid fuels into a gaseous product by reaction with steam.

Another object of this invention is to provide a process in which steam reacts with solid carbonaceous fuels to yield a gaseous product under such conditions that no heat need be added to the system to maintain the reaction, 1. e., under thermoneutral conditions.

A further object of this invention is to provide an improved process for making a high B. t. u. fuel gas which is rich in methane from the reaction between steam and carbonaceous solid fuels.

Still another object of my invention is to provide a method for converting carbonaceous solid fuels into a gas which is rich in hydrogen and which is substantially free of carbon dioxide.

For an understanding of my invention, reference should be had to the following description and to the accompanying drawings, in which:

Figure 1 is a graphical illustration of the critical relationship between temperature and pressure which governs the operation of my invention;

Figure 2 is a diagrammatic illustration of an apparatus comprising a one-vessel system adapted to carry out one embodiment of my invention;

Figure 3 is a diagrammatic illustration of an apparatus adapted to carry out the preferred embodiment of my invention; and

Figure 4 is a diagrammatic illustration of an apparatus adapted to carry out a modification of the preferred embodiment of my new process.

In accordance with my invention, I utilize the reaction between steam and carbon to convert solid carbonaceous fuels into a gaseous product in the presence of strontium oxide. I have discovered that when strontium oxide is mixed with carbonaceous solid fuels in the proper proportions and under certain critical conditions of temperature and pressure, the steam-carbon reaction is thermoneutral, i. e., no heat need be added to the system to maintain the reaction. In fact, the reaction may even be exothermic and capable of generating the steam necessary for the process. Moreover, it was found that under these thermoneutral conditions, gases which contained surprisingly high percentages of either methane or hydrogen can be selectively produced by operating under conditions lying within the critical range required to produce a thermoneutral reaction.

More specifically, my new process comprises the use of strontium oxide and finely divided carbonaceous solid fuels in the proportions of at least 220 parts by weight of strontium oxide to each parts by weight of carbon contained in the fuels. The mixture is reacted with steam at a temperature between 1550 and 2100 F. I have discovered, however that there is a minimum pressure at and above that which the overall reaction is thermally self-sufficient; i. e., at least thermoneutral and preferably exothermic. This minimum pressure is a function of the reaction temperature and, in the range from 1800 to 2100 F., is expressed by the empirical relation where p is the pressure in atmospheres and t is the reaction temperature in F. In the temperature range from l550 to 1800 F. the minimum pressure required to maintain a thermoneutral reaction is one atmosphere.

The gas producing process of my invention may be operated thermoneutrally provided that the pressure is maintained at or above the minimum value defined by Equation 1. However, I have found that when the operating pressure is increased above the minimum value at a constant temperature, the proportion of methane in the gas produced increases while the proportion of hydrogen correspondingly decreases. Thus at constant temperature, the composition of the product gas varies with the operating pressure.

If, then, a methane rich, high B. t. u. gas product is desired, there is a second minimum operating pressure, arbitrarily chosen, which must be exceeded in order that the heating value of the product gas (a measure of the methane content) will exceed 400 B. t. u. per cubic foot. This minimum pressure also can be expressed as an empirical function of the reaction temperature within the range 1550 to 2100 F. by the relation where p is the pressure in atmospheres and t is the temperature in F. In the temperature range 1550 to 1660" F., this empirical relation gives pressure values which are somewhat below the correct values which, however, can be readily established by a few tests.

Equations 1 and 2 are shown graphically in Figure 1. The improved process of my invention will produce a hydrogen rich gas when the op erating pressure lies between the curves representing Equations 1 and 2 as determined by the reaction temperature.

A methane rich, high B. t. u. gas can be produced when the operating pressure lies above the curve representing Equation 2 as determined by the reaction temperature. The process or my new invention will produce a methane rich gas within the temperature range from 1550 to 2100 F., but I prefer to produce methane rich gas within the temperature range from 1600 to 1700" F., and at a corresponding pressure ranging from five to fifty atmospheres, the pressure being in excess of that determined by Equation 2 depending upon the operating temperature.

A hydrogen rich gas can be produced in a thermoneutral reaction by my invention within the temperature range from l550 to 2100 F., but I prefer to produce hydrogen rich gas within the temperature range from 1'750 to l900 at a pressure corresponding to the reaction temperature, within the range from one to thirty atmospheres provided, however, that the pressure is at least that given by Equation 1 and is less than that given by Equation 2 according to the temperature employed.

In accordance with my invention, the reaction between steam and carbonaceous solid fuels is carried out in a single vessel system utilizing an on-and-ofi cycle. Steam is first passed through a bed of strontium oxide and the carbonaceous solids to produce a gas containing hydrogen, methane, carbon monoxide and carbon dioxide by the reaction between steam and carbonaceous solids. Simultaneously strontium carbonate is formed in the vessel from the reaction between strontium oxide and the carbon dioxide in the gas produced, there being suflicient oxide present to convert the carbon dioxide substantially cornpletely to carbonate. The reaction between the strontium oxide and carbon dioxide produced generates in situ the heat required to maintain the steam-carbon reaction under the conditions of temperature and pressure previously specified. During the oil cycle, air or any gas containing oxygen is circulated through the vessel to regenerate the strontium oxide from the carbonate. Suiiicient carbonaceous solids are oxidized during the regeneration cycle to raise the temperature of the strontium carbonate above its dissociation temperature so that the carbonate breaks down into strontium oxide and carbon dioxide.

While it is feasible to use a non-fluidized or fixed bed system, nevertheless I prefer to employ a fluidized system because the relatively high cost of strontium oxide necessitates an emcient operation to separate the strontium compound from unreacted carbonaceous solids and ash which is best performed in a fluidized system and also because the reactivity of the strontium oxide with the acidic components of the ash necessitates limiting the time of contact between the oxide and the ash.

In certain instances it may be desirable to accelerate the steam-carbon-strontium oxide reaction by the addition of catalytic materials. For example, the strontium oxide may be impregnated with amounts of the order of one to ten parts by weight of oxide of the transition group metals, such as iron, nickel, cobalt, manganese, etc.; or, on the other hand, small amounts of an alkali carbonate or other alkaline earth carbonate, such as sodium carbonate or barium carbonate may be employed.

In the following description of a specific embodiment of my invention, by way of example only, my new process is applied to the carbonaceous solid residue obtained by the low temperature distillation or carbonization of carbonaceous solid fuels such as the high volatile bituminous coal found in the Pittsburgh Seam. This residue, for the purpose of convenience, I shall hereafter refer to as char. It is to be understood, however, that the process is generally applicable to any carbonaceous solid fuels which react with steam to produce water gas. Among such carbonaceous solids are included all ranks of coal, lignite, oil shale, tar sands, coke from coal or petroleum pitch, solid tar, etc. Highly reactive solid fuels such as char and lignite are preferred when the process is operated at relatively moderate temperatures, i. e., below 1800 F.

The apparatus shown in Figure 2 and its operation will now be described. The preferred embodiment of my invention is shown in Figure 3, but because that shown in Figure 2 is simpler, it is considered first. A mixture of char and strontium oxide is introduced into a reaction vessel ID of any suitable type adapted to retain a bed of solids at elevated temperatures and high pressures. The mixture of strontium oxide and char is obtained by charging the oxide and char in the proper proportions from their respective supply hoppers l2 and M to a mixing chamber K5 in which the two batches of solids are thoroughly mixed. From the mixer It the solids are transferred to the vessel 10 through a conduit l8 by a motor driven screw feeder 20. The relative amounts of char and oxide in the mixture are regulated so that the resulting bed 22 in reaction vessel 10 contains at least 220 and preferably between 220 and 550 parts by weight of strontium for every parts by weight of carbon contained in the char. In order to raise the temperature of the bed to a point between l550 and 2100 F., air is introduced through suitably valved conduits 26. A small amount or" carbonaceous solids is burned by the air to attain the temperature of the bed previously specified.

When the temperature of the bed 22 has reached the desired range from 1550 to 2100 the how of air is discontinued and steam is introduced through suitably valved conduits 26. At the same time, a valve 28 in the gaseous product line 3 3 is set so that the pressure within vessel 10 will be at least one atmosphere or, in the temperature range from 1300" to 2100 F., will be at or above the minimum pressure calculated from Equation 1.

The pressure in vessel l0 should be at least that calculated from Equation 1 when a product is de sired with maximum hydrogen content and should lie within the area bounded by curves I and 2 of Figure l. The pressure is preferably within the range from one to thirty atmospheres for the production of a hydrogen rich gas. On the other hand, if a methane rich gas is desired, the pressure in vessel iii should exceed that given by Equation 2 and preferably should lie within the range of ten to forty atmospheres selected so that the pressure lies within the area above curve 2 as shown in Figure 1.

Steam passing up through bed 22 reacts with char to produce carbon monoxide, hydrogen, methane and carbon dioxide. Most of the carbon dioxide contained in the product gas reacts with the strontium oxide in bed 22 to produce stron- 6, as produced under different sets of temperature and pressure conditions. Under the heading (A) is shown the composition of the gas produced in the presence of strontium oxide under conditium carbonate and to liberate heat. Under the 5 tions of temperature and pressure favoring the critical conditions of temperature and pressure production of hydrogen rich gas. It should be determined by the relations above, the heat denoted that when strontium oxide is used in acveloped by the reaction of the carbon dioxide cordance with my invention, the hydrogen conwith the strontium oxide is sufficient to maintain tent is greatly increased. Heading (B) shows the temperature of the bed within the desired the composition of the gas produced in the presoperating range and to provide the heat necesence of strontium oxide under conditions favorsary for the endothermic reaction of the steam ing the production of methane rich gas. The with the char. When the steam has reacted with increase in methane content achieved by the substantially all the carbonaceous fuel in the bed method of my invention should be noted.

Twble WITHOUT ALKALINE EARTH OXIDES P t G H TGIIlgefitllre, ga gi e a ri i H, CH4 CO 002 ing valfiz V61 Absolute iim it. at 0 1 70 54.9 0.8 32.8 11.5 291 2o 70 44.9 as 30.6 15.7 334 28 70 45.6 7.5 33.7 13.2 332 10 70 52.0 1.8 37.5 8.7 308 WITH STRONIIUM OXIDE (A) AT PRESSURES SELEGTEDGKE) PRODUCE HYDROGEN RICH (B) AT HIGHER PRESSURESIIO PRgEUCE MEIHANE RICH, HIGH 22, the flow of steam through conduits 26 is discontinued, the pressure in the vessel is reduced to atmospheric, and air is introduced through conduits 24. The combustion of the remaining fuel with oxygen from the air provides the heat required to regenerate the strontium oxide by liberating carbon dioxide from the carbonate. The regenerated oxide and ash are then withdrawn from vessel I!) through conduit 32 by means of a motor driven screw feeder 34. The strontium oxide, after its separation from the ash by any suitably means, such as elutriation, is returned to hopper i2 for recirculation through the reaction zone. If desired, instead of an intermittent operation as described, the screws 20 and 34 may be operated continuously. In this case, the withdrawn carbonate is converted to oxide in a separate vessel by blowing air through a bed of withdrawn ash and carbonate; the regenerated oxide then is separated from the ash as before and returned to the oxide supply hopper l2.

The gas produced, with the exception of carbon dioxide, is conveyed through conduit to any Suitable point for further treatment or for immediate use or storage. It should also be pointed out that this product gas is relaitvely free from sulfur contamination because of the reaction of oxide with sulfur containing components of the gas producing solid sulfides which remain in vessel [0, The resulting sulfides are removed along with the ash through drawoff conduit 32.

e following table lists the percentages of each. at the components of the dry gas product The per cent steam conversion is given in each of the above examples in the table in order to permit a valid comparison to be made. The amount of this conversion is determined to a considerable extent by the residence time as is well known. However, where strontium oxide is employed under the conditions of my invention, a substantial increase in the maximum obtainable steam conversion is accomplished. In the cases where no oxide is present, the maximum steam conversion is of the order of 70430 per cent, while in those cases where strontium oxide is used, per cent conversion is approached.

It will thus be apparent that by proper selection of operating conditions within the above defined limits, it is possible to produce by my thermoneutral process a gas containing hydrogen, methane and carbon monoxide in a wide range of difierent relative proportions. Under certain of these conditions, a gaseous mixture may be produced in which the Hz/CO ratio is approximately 2/1. This mixture may be used as the synthesis gas for a Fischer-Tropsch conversion to liquid hydrocarbons.

In the operation of the apparatus shown in Figure 2 the regeneration of the strontium oxide was indicated as being carried out in a nonfluidized system. Whenever possible, however, it is desirable to regenerate the oxide in a fluidized operation to obtain good heat control. Furthermore, the reactivity of strontium oxide with acidic ash necessitates a minimum contact time between the oxide and the ash. Also the relatively high cost of strontium oxide requires an eflicient separation from the ash and maximum subsequent recovery which are best accomplished in a fluidized operation.

A system may accordingly be employed to accomplish these objectives in which the steamcarbon reaction and the strontium oxide regeneration are carried out under fluidized conditions. To facilitate separation of the reacted carbonaceous solids and strontium oxide or carbonate, it is possible to control their particle size to permit separation of the two kinds of solids by elutriation. Due regard must be given in selecting particle sizes to the fact that the strontium compounds have in general a higher density than the carbonaceous solids employed. A system employing this method is shown in Figure 3, the operation of which will now be described. This system is the preferred embodiment of the present invention, as previously stated.

Referring to Figure 3 of the drawings, char is fed to crushing, grinding and sieving equipment 50 which produces two different particle size range char fractions: a -l mesh fraction and a 35 to +100 mesh fraction. The relatively fine 100 mesh fraction is fed continuously through conduit 52 to a gasification reaction vessel 54 maintained at a temperature within the range of 1550 to 2100 F. Concurrently with the introduction of -100 mesh char into reaction vessel 54, strontium oxide of +150 mesh is discharged from regenerator 56 through valved discharge conduits 58 into screw feeder 60, whence it is picked up by steam circulating in steam conduit 62 and continuously charged to the reaction vessel 54 through conduit 62. At least 220 and pref erably between 220 and 550 parts by weight of strontium oxide are fed to the reactor for each 100 parts by weight of carbon contained in the char fed to the reactor.

In order to establish a temperature in the reactor within the range of 1550 to 2100 F., air is first introduced (not shown) instead of steam to oxidize a portion of the car in order to develop the necessary heat. Once this temperature has been established, steam replaces the air in order to carry out the steam-carbon reaction and, under the conditions maintained in the reactor, no further heat need be added to maintain the reaction. Water is converted to the steam required in the reaction by heat exchangers hereinafter to be described which utilize only heat developed during the reaction. The pressure in reactor G is maintained at a pressure in accordance with the previously expressed relations between the minimum pressure and temperature. Valve I0 in product gas line I2 serves to control the pressure in reactor 5Q. Product gas is conveyed from reactor 54 through a conduit 14 to a cyclone I6 where it is separated from entrained solids which fall through conduit Hi to a hopper 80. A portion of the separated solids is returned from hopper-8d to the bed 64 through conduit 82. The remaining solids are withdrawn from hopper 80 as ash through valved discharge conduit 34. Solid free product gas leaves the cyclone l6 through valved gas product line T2. The sensible heat contained in the product gas is utilized to generate steam in waste heat boiler 86. Cooled product gas leaves the waste heat boiler 35 through conduit 88 for immediate use or storage.

The reactions taking place in the reactor 54 are the same as those previously described in connection with Figure 2. In this instance, however, instead of regenerating the strontium oxide in vessel 54, a portion of the bed 54 overflows through a conduit 90 and settles into an elutriating bed 92 at the base of the reactor. Steam is introduced into bed 92 through conduit 68 at a linear velocity which depends upon the temperature, pressure and relative particle size but in general is in the range of 0.8 to 1.8 feet per second. The relatively fine char and char ash particles elutriated from bed 92 and suspended in fiuidizing steam pass up through porous plate 66 into the fluidized reaction bed 64 where the mesh char reacts with steam in the presence of strontium oxide. The strontium oxide concentration in the reaction bed 54 is maintained below about 30 weight per cent to minimize reactions between the oxide and the acidic components of the ash.

Strontium carbonate is withdrawn continuously from the elutriating section 92 of the reactor 54 through valved conduit 94 and introduced into a strontium oxide regenerator 56. Spent strontium carbonate is withdrawn from conduit 94 through valved discharge conduit 98. Strontium carbonate is regenerated in the fluidized regenerator 56 at atmospheric pressure by the heat developed in the oxidation of producer gas with air in the regenerator. Make up strontium oxide from a fresh storage hopper 98 is picked up by air circulating in conduit I00 and carried, suspended in the stream of air, into regenerator 56 through conduit I00. Flue gases from the regenerator are conducted through conduit I02 to a cyclone I04. Precipitated solids are returned to the regenerator bed I535 through a cyclone leg I08 while the solid free flue gases are vented through conduit I In. These hot gases may be passed in heat exchange relation with the cold inlet air entering the gas producer I22.

The regenerator is operated at atmospheric pressure and at a temperature of 2000 to 2250 F. Where the reactor 54 is operated above atmospheric pressure, two regeneration vessels connected in parallel are employed to operate alternately as regenerators and as lock hoppers for feeding strontium oxide under pressure to reactor 54. During one half of the operating cycle, strontium carbonate is introduced into and regenerated within one vessel while the other vessel, under a pressure equal to that employed in reaction vessel 54, supplies regenerated. oxide to the reaction zone. During the other half of the operating cycle, the lockhopper vessel becomes a regenerator, the pressure therein is reduced to atmospheric pressure, strontium carbonate, producer gas and air are introduced into the vessel. At the same time, the regenerator vessel becomes a lockhopper, introduction of strontium carbonate, air and producer gas is discontinued, the pressure within the vessel is raised to that in the reaction vessel and regenerated oxide is fed under pressure to the reaction vessel.

The +100 mesh char from the crushing, grinding and sieving equipment 50 is fed through con.- duit I I2 to a coarse char hopper I I4. Coarse char is fed continuously from hopper H4 through a screw feeder H6 whence it is picked up by a stream of air circulating through conduit I25} and carried into a fluidized producer gas generator I22, operating at atmospheric pressure and at temperature between 1700 and 1900 F. The superficial velocity of the air passing up through the char bed I24 is of the order of one foot per second to effect satisfactory fluidization of the char bed I24. Ash is withdrawn from the bed continuously through valved discharge conduit I 26. Producer gas is conducted from the generator I22 through conduit I28 to a cyclone I30. Precipitated solids return to the char bed I24 through cyclone return conduit I32 while the solid free producer gas leaves the cyclone through conduit I34. The solid free producer gas is conducted through conduit 34 to the regeneration vessel 55 where it is burned with air from conduit I to supply the heat necessary to regenerate the strontium oxide from the carbonate.

It will be seen that it is possible by the use of finely divided char particles and relatively heavy strontium oxide particles to produce the improved gas of my invention continuously in a fluidized operation with a minimum process loss of the relatively expensive strontium oxide. The arrangement and operation of equipment as shown in Figure 3 also provides sufficient contact time for the strontium oxide to react with substantially all of the carbon dioxide formed in the steam-carbon reaction but minimizes reactions between the strontium oxide and the acidic components of the ash.

An alternate method for accomplishing these same objectives is based on providing relatively coarse char particles of about -35 to +100 mesh along with relatively flne strontium oxide particles. Apparatus for carrying out my new process according to this method is illustrated in Figure 4 of the drawings, the operation of which will now be described.

Strontium oxide of relatively fine particle size, e. g., 200 mesh is stored in lockhopper 200. Steam circulating in conduit 202 picks up strontium oxide from hopper 200 and carries it into a fluidized gasification reaction vessel 204. Relatively coarse, i. e., -35 to +100 mesh char from char lockhopper 200 also is picked up by steam circulating in conduit 202 and is carried into a gasification reactor 204. The weight ratio of strontium oxide to char is at least 220/100 and preferably between 220/100 and 550/100. Reaction vessel 204 is maintained at a pressure determined by the empirical relations given above depending upon whether a hydrogen-rich or methane-rich gas product is desired. The pressure is maintained by adjusting valves 205, 207 and 209.

The reactions occurring in the gasification reaction are essentially the same as those de-- scribed in connection with Figure l. The linear velocity of the gases above the fluidized bed 208 is sufficient to carry overhead all the strontium carbonate formed during reactions in the bed but insuflicient to carry off the +100 mesh char or ash particles. Linear velocities in the range of 0.6 to 1.4 feet per second may be employed depending upon the conditions of temperature and pressure within the reactor.

Particles from the bottom of reaction bed 208 are continuously withdrawn from the reactor 204 through conduit 210 and sent into an elutriation vessel 2 I2, maintained at the same pressure as that in reactor 204. Steam entering the base of the elutriation vessel 2l2 through conduit 2M passes up through the bed 2"; maintained in the vessel at a linear velocity sufficient to carry overhead the relatively fine particles of strontium oxide (or carbonate) but insufficient to carry off the relatively coarse char or ash Particles. Strontium oxide (or carbonate) particles entrained in the elutriating steam leave the elutriator and return to the reactor 204 through conduit H8.

The reactions taking place in reaction vessel 204 are the same as those previously described in connection with Figure 2. The gas produced in the reactions has the same composition as that shown in the table when produced under the same conditions of temperature, pressure and steam conversion. Product gas together with entrained strontium carbonate particles from reactor 204 passes from the reactor through conduit 22a? to a waste heat boiler 222 where the sensible heat is utilized to generate steam used in the process and thence to a cyclone separator where the entrained strontium carbonate particles are removed from the product gas. Solid free product gas leaves the cyclone through conduit 22b for immediate use or storage. Precipitated solids pass from the cyclone 224 through conduit 228 to a depressurizing surge pot 200, maintained at atmospheric pressure by a conduit vent 23L Meanwhile coarse char and ash particles from the elutriation vessel 2I2 are continuously withdrawn from the base of bed 253 through conduit 232 and suspended in a stream of air in conduit 234 which carries them into a fluidized producer gas generator 236 operated at atmospheric pressure. Any l00 mesh char particles produced in the initial crushing and grinding operation may likewise be fed. to the producer gas generator. Ash is continuously withdrawn from the bed 238 in the generator through valved discharge conduit 240. Producer gas passes from the generator 236 through conduit 242 to a cycylone 244 from which solid fines entrained in the gas are returned to the bed 238 through cyclone leg 246. The producer gas leaves the cyclone 244 through conduit 243 and picks up strontium carbonate from the depressurizing surge pot 230, carrying the carbonate particles in suspension into a burner type oxide regeneration vessel 25!] operated at atmospheric pressure.

The producer gas which carries carbonate particles into the regenerator vessel is burned with air from conduit 252 to supply the heat necessary to convert the strontium carbonate to strontium oxide and to generate process steam. Flue gases and regenerated oxide leave the regenerator 250 through conduit 254 and enter cyclone 256 from which the solid free flue gases are conducted to any suitable place of disposition through a conduit 258. Separated strontium oxide particles are returned from the cyclone through conduit 260 to the strontium oxide lockhopper 200 to be recirculated in the process.

Thus it will be seen that by using finely divided particles of strontium oxide and relatively coarse particles of char in the apparatus shown diagrammatically in Figure 4, it is possible to produce continuously the improved gas of my invention in a fluidized operation with a minimum process loss of the strontium oxide.

It is to be understood that wherever the word char is used in the foregoing description and in the accompanying claims, it is intended to signify the carbon-containing residue obtained by the low temperature distillation of a carbonaceous solid fuel.

According to the provisions of the patent statutes, I have explained the principle, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced other-- 11 wise than as specifically illustrated and described.

I claim:

1. The process for making water gas which comprises charging finely divided carbonaceous solid fuel particles and finely divided particles of strontium oxide to a reaction zone under fluidized conditions in such size relation that the strontium oxide particles are separable by elutriation, maintaining a temperature within said reaction zone within the range of 1558 to 2100 F. and a pressure of at least one atmosphere when the temperature of the reaction zone is within the range of 1550 to 1800 F., and when the reaction zone temperature is within the range of 1800 to 2100 F. a pressure whose minimum value is determined by the expression where p is the pressure in atmospheres and t is the temperature in F., passing steam into said reaction zone in reactive relationship with said carbonaceous solids to produce a gas containing carbon dioxide, converting said strontium oxide to strontium carbonate by the reaction with said carbon dioxide, regulating the linear velocity of the fluidizing gas passing up through said reaction zone so that the strontium carbonate particles are carried up from the fluidized reaction bed and pass overhead to a regeneration zone, withdrawing from said reaction zone a portion of the relatively heavy carbonaceous solids and charging said carbonaceous solids to a producer gas generator, burning the resulting producer gas with air in said regeneration zone to provide the heat necessary to reconvert said withdrawn strontium carbonate to strontium oxide, withdrawing said reconverted strontium oxide from said regeneration zone and returning said reconverted strontium oxide to said reaction zone concurrently with the introduction of additional carbonaceous solids to said reaction zone in such proportion that there are at least 220 parts by weight of strontium charged to said reaction zone for each 100 parts by weight of carbon contained in the carbonaceous solids charged to said reaction zone, and recovering the gaseous products from said reaction zone.

2. The process for making water gas which comprises charging finely divided carbonaceous solid fuel particles and finely divided particles of strontium oxide to a reaction zone under fluidized conditions in such size relation that the strontium oxide particles are separable by elutriation, maintaining a temperature within said reaction zone within the range of 1550 to 2100 F. and a pressure or at least one atmosphere when the temperature of the reaction zone is within the range of 1550 to 1800 F., and when the reaction zone temperature is within the range of 1800 to 2100 F., a pressure whose minimum value is determined by the expression =1.05.9 X 10 (t-1800) +2.69 10-- (t-1800) 2 +0.958 X 10- (t1800) where p is the pressure in atmosphere and t is the temperature in F., passing steam into said reaction zone in reactive relationship with said carbonaceous solids to produce a gas containing carbon dioxide, converting said strontium oxide to strontium carbonate by the reaction with said carbon dioxide, regulating the linear velocity of the fiuidizing gas passing up through said reaction zone so that the strontium carbonate particles are carried up from the fluidized reaction bed and pass overhead to a regeneration zone, where the carbonate is reconverted to oxide, and returning said reconverted strontium oxide to said reaction zone concurrently with the introduction of additional carbonaceous solids to said reaction zone in such proportion that there are at least 220 parts by weight of strontium oxide charged to said reaction zone for each 100 parts by weight of carbon contained in the carbonaceous solids charged to said reaction zone, and recovering the gaseous products from said reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,687,118 Winkler Oct. 9, 1928 2,456,072 Marisic Dec. 14, 1948 2,538,235 Coffey Jan. 16, 1951 FOREIGN PATENTS Number Country Date 477,083 France June 28, 1915 284,816 Germany June 5, 1915 116,302 Great Britain June 13, 1918 372,089 Great Britain May 5, 1932 OTHER REFERENCES Mellor, Treatise on Inorganic and Theoretical Chemistry, vol. 3 (1923), page 837.

Claims (1)

1. THE PROCESS FOR MAKING WATER GAS WHICH COMPRISES CHARGING FINELY DIVIDED CARBONACEOUS SOLID FUEL PARTICLES AND FINELY DIVIDED PARTICLES OF STRONTIUM OXIDE TO A REACTION ZONE UNDER FLUIDIZED CONDITIONS IN SUCH SIZE RELATION THAT THE STRONTIUM OXIDE PARTICLES ARE SEPARABLE BY ELUTRIATION, MAINTAINING A TEMPERATURE WITHIN SAID REACTION ZONE WITHIN THE RANGE OF 1550* TO 2100* F. AND A PRESSURE OF AT LEAST ONE ATMOSPHERE WHEN THE TEMPERATURE OF THE REACTION ZONE IS WITHIN THE RANGE OF 1550* TO 1800* F., AND WHEN THE REACTION ZONE TEMPERATURE IS WITHIN THE RANGE OF 1800* TO 2100* F. A PRESSURE WHOSE MINIMUM VALUE IS DETERMINED BY THE EXPRESSION

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