US2659668A - Method for gasifying coals - Google Patents

Description

NOV. 17, 1953 MAYLAND 2,659,668

METHOD FOR GASIFYING GOALS Filed Sept. 12. 1949 K: k I II l I4 I r\ 'iHr 28 u L: 29 l 34 U 26 IN VEN TOR. B. J. MAYLAND BY WWW A TTORNEVS Patented Nov. 17, 1953 METHOD FOR GASIFYING GOALS Bertrand J. Mayland, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application September 12, 1949, Serial No. 115,209

4 Claims.

This invention relates to the gasification of organic so id materials. In one of its more specific aspects it relates to a method and apparatus for the gasification of coking and low ashfusion-temperature coals,

The gasification of coal can be represented by the reaction between steam and carbon, i. e.. C+H2O- CO+H2. This reaction takes places at temperatures in the neighborhood of approximately 1200 but in commercial operation it is ordinarily desirable to use higher temperatures so as to obtain a more rapid rate of reaction. Other reactions also occur in the gasification of coal, such as etc. The resulting gas, therefore, is a mixture of hydrogen. carbon monoxide, steam, carbon dioxide, and hydrocarbons. Hydrocarbons are also formed by thermally cracking the coal structure which is composed of complex molecules of primarily carbon anal hydrogen. The net gasifica- 'tion reaction is endothermic and most commercial processesvary mainly in their means of introducing heat of reaction for the gasification process. Some conventional processes use internally fired retorts. others provide for periodically blasting the bed of coal with air, and others provide for continually introducing oxygen to make the net reaction exothermic, thus highly super-heating steam which is added.

In conventional operation the coal is introduced into a gasification reactor and is heated by one of the above means to the reaction temperature. As the coal is heated, at number of things may happen. At temperatures in the neighborhood of between 4-00 and 500" the coal starts to lose its volatile matter, the first released material being mainly loosely bound water. As the temperature is increased, more violent thermal decomposition occurs and hydrocarbon fragments are given off as volatile matter. Larger hydrocarbon fragments, resulting either from cracking or polymerization of smaller hydrocarbon fragments remain in the coal and exert a solvent action thereon. When this occurs the coal goes through a plastic or semi-fluid state. The temperature at which the coal is converted to a plastic or semi-fluid state depends upon the particular coal which is being reacted. With a bituminous coal a plastic or semi-fluid state is encountered at temperatures in the nei hborhood-of between 800 F. and 1000 F. Certain types of coals, such as lignitic coal and high rank anthracite coal, do not go through the plastic state.

Goals which form a plastic state will, upon further heating, further decompose with the evo' lution of volatile matter and form a resulting solid coke residue.

Commercial gasification processes have heretofore utilized as a feed, coke and coals which do not pass through a plastic or semi-fluid state. Since these materials do not go through a plastic stage, no difficulty is encountered in the gasification thereof. A great deal of the coal which is available in the United States for gasification is of a coking variety, such as bituminous and subbituminous coals. When these coals are supplied to conventional commercial processes, considerable plugging difficulties are encountered in the feed entry and reaction chambers tend to become plugged because of caking on the walls of the chamber where the process utilizes a powdered coal as the feed and the formation of solid clinker-like plugs when the process utilizes a moving solid bed of coal. It has therefore been necessary, heretofore. to convert such coal to cake before supplying the material to a gasification system.

The present invention is devised to overcome the obstacles and difficulties described above which beset conventional gasification processes when utilizing coking and low ash-fusion-temperature coals. Broadly speaking, the invention comprises forming a coating of coke upon the surface of hot, small particles of solid heat exchange material. The coke encrusted solid heat exchange material is then passed to a gasification chamber wherein the coke encrusted solid heat exchange material is contacted with a mixture of steam and oxygen whereby the coke material is gasified. The solid heat exchange material is then removed from the gasification cham-- her and is heated once again for the purpose of supplying heat to coal which is mixed therewith so as to form a layer of coke on the particles of the solid heat exchange material.

An object of this invention is to provide improved means for gasifying organic solid rials. Another object of the invention is to provide an improved method for gasifying or anic solid materials. Another object of the invention is to provide a method for gasifying low ashfusion-temperature coals. Another object of the invention is to provide a method for gasifyins: organic solid materials and preventing the accumulation of coke on the walls of gasifying apparatus. Other and further objects and advantages of this invention will be apparent to those skilled in the art upon study of the accompanying disclosure.

Solid heat exchange material which may be utilized in the gasification system of this invention may be generally termed pebbles. The term pebbles as used herein denotes any substantially solid material of flowable size and form which has sufiicient strength to withstand me-- chanical pressures and the temperatures encountered Within the gasification system. These pebbles must be of such structure that they can carry large amounts of heat from one chamber to another without rapid deterioration or substantlal breakage. Pebbles which may be satisfactorily used in this gasification system may be substantially spherical in shape and range from about 2; inch to about 1 inch in diameter. The size of the pebbles which are used will generally be dependent upon the state of the organic solid material with which they are mixed. When the organic solid material is in a finely powdered state, the pebbles are preferably of a size Within the range of from A inch to A; inch in diameter. Materials which may used singly or in combination in the formation of such pebbles include among others alumina, silicon carbide, periclase, beryllia, mullite, nickel, cobalt, copper, iron, magnesia, and zirconia.

More complete understanding of the invention wil be obtained upon reference to the drawing which is a schematic representation of the device oi this invention.

Referring particularly to the drawing, heating chamber i l comprises a vertically disposed chamber l2 being closed at its upper and lower ends by closure-members i3 and I4, respectively. Peb ble inlet conduit i5 and eliluent outlet conduit 16 are provided in closure member l3. Pebble outlet conduit ll disposed in closure chamber E4.

Perlorate pebble support member l8 extends upwardly and outwardly from the inlet end of conduit H to the walls of shell l2. Member l8 forms a false bottom in the bottom of chamber I l and is perforate so as to-r-ermit drainage of liquid therethrough, but so as to prevent the passage of pebbles therethrough. Liquid ash outlet conduit [9 is provided in closure member l4 below support member i8. Fluid heat exchange material inlet conduit 2| is provided in the wall of shell l2, preferably in the lower portion thereof but above the rim of support member 18. Coking chamber 22 is a cylindrical shell 23 which is rotatably mounted at its ends in end closure members 24 and 25. Closure members 24 and 25 are maintained rigidly in place and permit shell 23 to rotate therein. Traction means, such as toothed member 26. is provided about the outer surface of shell 23 and is operatively connected. to drive means, such as motor 27. Coking chamber 22 is inclined from the horizontel at an angle of between 1 and It is preierred that the angle oi inclination be between fl and i5". Pebble outlet conduit [1 extends r rom the lower end of chamber II to the upper end. of chamber 22 and forms a pebble inlet conduit for the latter chamber. Conduit 28 is provided in closure member 24 so as to provide inlet mean for finely divided organic solid material. Effluent outlet conduit 29 extends from closure member 24 to condensation chamber 3!. Separation chamber 32 is connected to condensation chamber 3| by means of conduit 33. Condensate outlet conduit 34 extends from the bottom of separation chamber 32 and effluent outlet conduit 35 extends from the upper portion of separation chamber 32. Gasification chamber 36 comprises shell 3'! closed at its upper and lower ends by closure members 38 and 39, respectively. Pebble conduit 4| extends between closure member 25 at the lower end of coking chamber 22 and closure member 38 at the upper end of gasifioation chamber 36. Efiluent outlet conduit 42' extends u}.- wardly from closure member 38 and is connected to effluent outlet conduit 35 to form a common outlet conduit. The gasifying medium conduit 43 is provided in shell 31 adjacent its lower en Pebble outlet conduit 44 is provided in closure member 39 and extends to elevator 45. Elevator 45 is connected at its upper end to pebble inlet conduit 15 of heating chamber 1 I. Screen mem ber 46 is provided in the lower wall of a portion of pebble outlet conduit 44 and chamber 4'! is provided below screen member 46. Solid ash outlet conduit 48 is provided in the bottom of chamber 41.

In the operation of the device disclosed above. solid heat exchange material is introduced to pebble heating chamber II and is heated to a temperature of at least 1200 F. The pebbles are preferably heated to a temperature within the range of between 1200 F. and 2000 F. Heat is provided to the flowing bed of pebbles within chamber II by passing a fuel which may be a hydrocarbon liquid or gas into the chamber through inlet conduit 2|. The fuel is burned on the surface of the pebbles, providing heat to e pebbles, and the resulting combustion g" passed upwardly through the pebble bed and is removed from chamber ll through eflluent outlet conduit l6. This method of operation may be modified by passing a hot gas, such as hot oombustion gas, into chamber H through inlet conduit 2| rather than supplying a fuel therethrough. The heated pebbles are removed from the lower portion of chamber ll through pebble outlet con- .duit I! and are supplied to the upper portion or coking chamber 22.

Powdered organic solid material. such a ing or low ash-fusion-temperature coal, is to coking chamber 22 through inlet condu Shell 23 is rotated at a speed Within the range of from 1 to 30 revolutions per minute, prefer: ly at a speed of from 1 to 15 revolutions per minute. by the connection between motor 21 traction member 26, or any other conventional drive means. The powdered organic solid is mixed with the heated pebbles and receives suilicient sensible heat from the pebbles to convert it to a coke layer upon the surface of the pebbles. Loosely bound water and any hydrocarbon material which. is released is removed from chamber 22 through efduent outlet conduit 29. The efiiuent material is passed through condensation chamber 3! Where it is cooled so as to condense the water. The materials are then passed into separation cham ber 32 through conduit 33 and the condensed i1" terials are separated from the unoondensod F terials. The uncondensed hydrocarbon mater-m is are removed through conduit 35 and the com densed materials are removed through co?- duit 34.

The speed at which shell 23 is rotated wil pend generally upon the diameter of the The rotation of shell 23 is supplied only f o. purpose of insuring complete mixing of heated solid heat exchange material and the powdered organic solid material. The inclination of chamber 22 from the horizontal is sufficient to insure flow of the coke covered solid heat exchange material from the lower end of chamber the the 22 through conduit 4| into gasification chamber 36. The coated solid heat exchange material forms a flowing bed within chamber 36.

Oxygen and steam are supplied to the lower portion of chamber 36 through conduit 43 and is passed upwardly countercurrent the flow of the coated solid heat exchange material. The coke is gasified by the reaction with steam and the resulting gaseous materials are removed from chamber 36 through effluent outlet conduit 42. The hydrocarbons from conduit 35 are added to the gases in conduit 42 so as to enrich the gases therein. The cooled solid heat exchange material is removed from the bottom of chamber 36 through pebble outlet conduit 44 and passes over screen 46 to elevator 45. Any solid ash which has been separated from the surface of the solid heat exchange material is removed from the flowing mass of solid heat exchange material by allowing it to fall through screen 46 into chamber 41 from which it is removed through outlet conduit 48. The solid heat exchange material is elevated by elevator 45 to the upper portion of heating chamber ll. Any ash which remains on the surface of the solid heat exchange mate-' rial is melted by th application of heat to that solid heat exchange material in heating chamber H. The melted ash flows downwardly through the perforate support member I8 and is removed from the bottom of chamber through melted ash outlet conduit l9.

The description of the method of this invention is clearly applicable to the operation of the apparatus which is shown in the drawing. The scope of the method of gasifying the coking variety of coals which is disclosed herein is believed to be broader than the specific apparatus herein disclosed. It should be noted that the device of this invention could be modified by providing another type of tumbler device which would insure complete mixing of the coal and heated pebbles, but the device would not necessarily have to be rotated axially. A separation means, such as screen 46 and chamber 41, could be provided in pebble outlet conduit I1 and pebble support member It would therefore not be required. It is very important, however, that the coke be gasified while coating the solid heat exchange material and that a minimum of grinding be obtained in drum 22. By passing the pebbles and coke to the gasification chamber without separation, a greater overall heat efllciency is obtained and producer gas of higher calorific value is obtained.

The upper surface of support member I8 is preferably formed as an inverted com. the included angle within said cone being between 60 and 100. A support member which has such a slope on its upper surface will direct pebbles through its central inlet and substantially prevent the accumulation of stagnant pebbles on its upper surface.

Inert gas. such as steam, may be supplied to 6 pebble conduits I1 and 4| through conduits not shown. The inert gas will act as a choke means and will prevent eiiiuent gas from passing from one chamber upwardly through conduits l1 and 4| to another chamber.

Various other modifications of the invention will be apparent to those skilled in the art upon study of the above disclosure. It is believed that such modifications are within the spiritand the scope of the disclosure.

I claim:

1. An improved method for gasifying organic material which comprises the steps of heating solid heat exchange material in a heating zone; gravitating said heated solid heat exchange material into a coking zone; continuously tumbling said heated solid heat exchange material in said coking zone while adding organic material thereto; decomposing said organic material to coke on the surface of said solid heat exchange; material; gravitating said coke-covered solid heat exchange material into a gasification zone; passing steam and oxygen into contact with said coke-covered solid heat exchange material and gasifying said coked organic material; recovering resulting gaseous materials from said gasification zone; removing said solid heat exchang material from said gasification zone; and returning said solid heat exchange material to said heating zone.

2. The method of claim 1 wherein loose solid ash is separated from said coke covered solid heat exchange material after the gasification step but before the heating step.

3. The method of claim 1, wherein any solid ash remaining on said solid heat exchang material is melted in said heating zone; and separating resulting liquid ash from solid heat exchange material in said heating zone.

4. The process of claim 1 wherein said organic material is low ash-fusion-temperature coal; heating said solid heat exchang material in said heating zone to a temperature between 1200 F. and 2000 F.; and maintaining a ratio of the portion of said solid heat exchange material to said coal supplied to said coking zone within the range of from 1:1 to 10:1.

BERTRAND J. MAYLAND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,654,942 Nielsen et a1. Jan. 3, 1928 1,784,985 Davies, Jr. Dec. 16, 1930 1,977,684 Lucke Oct. 23, 1934 2,441,386 Berg May 11, 1948 2,519,340 Bailey Aug. 22, 1950 2,579,398 Roetheli Dec. 18, L

FOREIGN PATENTS Number Country Date 109,689 Australia Jan. 26, 1940 189,542 Great Britain --'Dec. 1, 1922

Claims (1)

1. AN IMPROVED METHOD FOR GASIFYING ORGANIC MATERIAL WHICH COMPRISES THE STEPS OF HEATING SOLID HEAT EXCHANGE MATERIAL IN A HEATING ZONE; GRAVITATING SAID HEATED SOLID HEAT EXCHANGE MATERIAL INTO A COKING ZONE; CONTINUOUSLY TUMBLING SAID HEATED SOLID HEAT EXCHANGE MATERIAL IN SAID COKING ZONE WHILE ADDING ORGANIC MATERIAL THERETO; DECOMPOSING SAID ORGANIC MATERIAL TO COKE ON THE SURFACE OF SAID SOLID HEAT EXCHANGE MATERIAL; GRAVITATING SAID COKE-COVERED SOLID HEAT EXCHANGE MATERIAL INTO A GASIFICATION ZONE; PASSING STEAM AND OXYGEN INTO CONTACT WITH SAID COKE-COVERED SOLID HEAT EXCHANGE MATERIAL AND GASIFYING ZONE; COKED ORGANIC MATERIAL; RECOVERING RESULTING GASEOUS MATERIALS FROM SAID GASIFICATION ZONE; REMOVING SAID SOLID HEAT EXCHANGE MATERIAL FROM SAID GASIFICATION ZONE; AND RETURNING SAID SOLID HEAT EXCHANGE MATERIAL TO SAID HEATING ZONE.

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