CA1119542A - System for the recovery of alkali metal compounds for reuse in a catalytic coal conversion process - Google Patents
System for the recovery of alkali metal compounds for reuse in a catalytic coal conversion processInfo
- Publication number
- CA1119542A CA1119542A CA000294728A CA294728A CA1119542A CA 1119542 A CA1119542 A CA 1119542A CA 000294728 A CA000294728 A CA 000294728A CA 294728 A CA294728 A CA 294728A CA 1119542 A CA1119542 A CA 1119542A
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- alkali metal
- water
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- calcium
- aqueous solution
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
- C10J3/46—Gasification of granular or pulverulent flues in suspension
- C10J3/54—Gasification of granular or pulverulent fuels by the Winkler technique, i.e. by fluidisation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/08—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal with moving catalysts
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
- C10J3/46—Gasification of granular or pulverulent flues in suspension
- C10J3/48—Apparatus; Plants
- C10J3/482—Gasifiers with stationary fluidised bed
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
- C10J2300/0903—Feed preparation
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
- C10J2300/0913—Carbonaceous raw material
- C10J2300/093—Coal
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
- C10J2300/0953—Gasifying agents
- C10J2300/0973—Water
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
- C10J2300/0983—Additives
- C10J2300/0986—Catalysts
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/18—Details of the gasification process, e.g. loops, autothermal operation
- C10J2300/1807—Recycle loops, e.g. gas, solids, heating medium, water
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/18—Details of the gasification process, e.g. loops, autothermal operation
- C10J2300/1807—Recycle loops, e.g. gas, solids, heating medium, water
- C10J2300/1823—Recycle loops, e.g. gas, solids, heating medium, water for synthesis gas
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/18—Details of the gasification process, e.g. loops, autothermal operation
- C10J2300/1853—Steam reforming, i.e. injection of steam only
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Combustion & Propulsion (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Processing Of Solid Wastes (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
- Catalysts (AREA)
Abstract
U.S. 762,548 ABSTRACT OF DISCLOSURE
In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by mixing them with calcium oxide or a solid calcium-containing compound that decomposes upon heating to from calcium oxide, and heating the resultant mixture of solids to a temperature sufficiently high to cause calcium oxide to react with water insoluble alkali metal aluminosilicates in the alkali metal residues to produce reaction produces containing water soluble alkali metal aluminates and water insoluble calcium silicates. The reaction products are contacted with water, which leaches the alkali metal aluminates and other water soluble alkali metal constituents from the solids. The pH of the resultant aqueous solution is lowered by contacting it with a carbon dioxide-containing gas under conditions such that carbon dioxide reacts with the alkali metal aluminates to form a water insoluble precipitate containing aluminum hydroxide and an aqueous solution containing water soluble alkali metal carbonates. The aqueous solution is recycled to the gasification process where the alkali metal carbonates serves as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. This process permits increased recovery of alkali metal constituents, thereby decreasing the overall cost of the gasification process by reducing the amount of makeup alkali metal compounds necessary.
In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by mixing them with calcium oxide or a solid calcium-containing compound that decomposes upon heating to from calcium oxide, and heating the resultant mixture of solids to a temperature sufficiently high to cause calcium oxide to react with water insoluble alkali metal aluminosilicates in the alkali metal residues to produce reaction produces containing water soluble alkali metal aluminates and water insoluble calcium silicates. The reaction products are contacted with water, which leaches the alkali metal aluminates and other water soluble alkali metal constituents from the solids. The pH of the resultant aqueous solution is lowered by contacting it with a carbon dioxide-containing gas under conditions such that carbon dioxide reacts with the alkali metal aluminates to form a water insoluble precipitate containing aluminum hydroxide and an aqueous solution containing water soluble alkali metal carbonates. The aqueous solution is recycled to the gasification process where the alkali metal carbonates serves as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. This process permits increased recovery of alkali metal constituents, thereby decreasing the overall cost of the gasification process by reducing the amount of makeup alkali metal compounds necessary.
Description
4~Z I
2 ` ~ l. Field of the Invention: This invention
3 relates to the conversion of coal and similar carbona-
4 ceous solids in the presence of alkali metal-containing catalysts and is particularly concerned with the recovery 6 of alkal~ metal constituents from spent solids produced i during coal gasification and similar operations and their 8 reuse as constituents of the alkali metal-containg cata-;
lysts.
2. Description of the Prior Art: Potassium 11 carbonate, cesium carbonate and other alkali metal com-12 pounds have been recognized as useful catalysts for the 13 gasification of coal and similar carbonaceous solids. The 14 use of such compounds in coal liquefaction, coal carboni-zation, coal combustion and related processes has also 16 been proposed. To secure the higher reaction rates made 1i possible by the presence of the alkali metal compounds it 18 has been suggested that bituminous coal, subbituminous -19 coal, lignite, petroleum coke, oil shale, organic wastes ~ and similar carbonaceous materials be mixed or impregnated 21 with potassium, cesium, sodium or lithium compounds, alone 22 or in combination with other metallic constituents, before 23 such materials are reacted with steam, hydrogen, oxy~en or 24 other agents at elevated temperatures to produce gaseous and/or liquid effluents. Studies have shown that a wide 26 variety of different alkali metal compositions can be used 27 ~or this purpose, including both organic and inorganic 28 salts, oxides, hydroxides and the like.
29 In general the above-described studies indicate that cesium compounds are the most effective gasification ~ 2 -~19~
.
:' . ' ' 1 catalysts followed by potassium, sodium and lithium com-2 po~nds, in that order. Because of the relatively high 3 cost of cesium compounds and the low effectiveness of 4 lithium compounds, most of the experimental work in this area that has been carried out in the past has been 6 directed toward the use of compounds of potassium and 7 sodium. This work has shown that the potassium compounds .
` 3 are substantially more effective than the corresponding . . .
' 9 sodium compounds. Attention has therefore been focused ... ~
on the use of potassium carbonate.
11 Coal gasification processes and similar opera-12 tions carried out in the presence of alkali metal com-13 pounds at high temperatures generally result in the forma-14 tion of chars and alkali metal residues. The chars normally include unconverted carbonaceous constituents of 16 the coal or other feed material and various inorganic con-17 stituents generally referred to as ash. It is generally 18 advisable to withdraw a portion of the char from the 19 reaction zone during gasification and similar operations in order to eliminate the ash and keep it from building 21 up within the reaction zone or other vessels in the system.
22 Elutriation methods and other techniques for separating 23 char particles of relatively high ash content and return-24 ing particles of relatively low ash content to the reaction zone in order to improve the utilization of car-26 bon in such processes have been suggested.
27 In gasification and other processes referred to 28 above that utilize alkali metal-containing catalystS, the 29 cost of the alkali metal constituents is a significant factor in determining the overall cost of the process.
1~9542 1 In order to maintain catalyst cost at reasonable levels, 2 it; is essential that the alkali metal constituents be 3 recovered and reused. There have been proposals for the 4 recovery of alkali metal constituents by leaching as
lysts.
2. Description of the Prior Art: Potassium 11 carbonate, cesium carbonate and other alkali metal com-12 pounds have been recognized as useful catalysts for the 13 gasification of coal and similar carbonaceous solids. The 14 use of such compounds in coal liquefaction, coal carboni-zation, coal combustion and related processes has also 16 been proposed. To secure the higher reaction rates made 1i possible by the presence of the alkali metal compounds it 18 has been suggested that bituminous coal, subbituminous -19 coal, lignite, petroleum coke, oil shale, organic wastes ~ and similar carbonaceous materials be mixed or impregnated 21 with potassium, cesium, sodium or lithium compounds, alone 22 or in combination with other metallic constituents, before 23 such materials are reacted with steam, hydrogen, oxy~en or 24 other agents at elevated temperatures to produce gaseous and/or liquid effluents. Studies have shown that a wide 26 variety of different alkali metal compositions can be used 27 ~or this purpose, including both organic and inorganic 28 salts, oxides, hydroxides and the like.
29 In general the above-described studies indicate that cesium compounds are the most effective gasification ~ 2 -~19~
.
:' . ' ' 1 catalysts followed by potassium, sodium and lithium com-2 po~nds, in that order. Because of the relatively high 3 cost of cesium compounds and the low effectiveness of 4 lithium compounds, most of the experimental work in this area that has been carried out in the past has been 6 directed toward the use of compounds of potassium and 7 sodium. This work has shown that the potassium compounds .
` 3 are substantially more effective than the corresponding . . .
' 9 sodium compounds. Attention has therefore been focused ... ~
on the use of potassium carbonate.
11 Coal gasification processes and similar opera-12 tions carried out in the presence of alkali metal com-13 pounds at high temperatures generally result in the forma-14 tion of chars and alkali metal residues. The chars normally include unconverted carbonaceous constituents of 16 the coal or other feed material and various inorganic con-17 stituents generally referred to as ash. It is generally 18 advisable to withdraw a portion of the char from the 19 reaction zone during gasification and similar operations in order to eliminate the ash and keep it from building 21 up within the reaction zone or other vessels in the system.
22 Elutriation methods and other techniques for separating 23 char particles of relatively high ash content and return-24 ing particles of relatively low ash content to the reaction zone in order to improve the utilization of car-26 bon in such processes have been suggested.
27 In gasification and other processes referred to 28 above that utilize alkali metal-containing catalystS, the 29 cost of the alkali metal constituents is a significant factor in determining the overall cost of the process.
1~9542 1 In order to maintain catalyst cost at reasonable levels, 2 it; is essential that the alkali metal constituents be 3 recovered and reused. There have been proposals for the 4 recovery of alkali metal constituents by leaching as
-5 they are withdrawn from the reaction zone with char
6 during operations of the type referred to above. Studies ~ 7 indicate that these constituents are generally present in part as carbonates and other water soluble compounds 9 which can be recovered by water washing. Experience has .
shown that only a portion of the potassium carbonate or 11 other alkali metal constituents is normally recovered and 12 that substantial quantities of makeup alkali metal com- ¦
13 pounds are therefore required. This adds appreciably to the cost of such operations.
SUMMARY OF THE INVENTION
16 The present invention provides an improved pro-17 cess for the recovery of alkali metal constituents from 18 char particles produced during coal gasification and other 19 conversion processes carried out in the presence of an alkali metal-containing catalyst. In accordance with the 21 invention, it has now been found that increased amounts 22 f alkali metal constituents can be effectively recovered 23 from particles containing alkali metal residues produced 24 during coal gasification and related high temperature conversion processes by mixing the particles with calcium 26 oxide or a solid calcium-containin~ compound that decom-27 poses upon heating to form calcium oxide, and heating the 28 resultant mixture of solids to a temperature sufficiently high to cause calcium oxide to react with water insoluble alkali metal aluminosilicates in the alkali metal residues ~i~gS4Z
1 to produce reaction products containing water insoluble 2 calcium silicates and water soluble alkali metal alumi-, 3 nates. The reaction products are contacted with water, 4 which leaches the alkali metal aluminates and other water soluble alkali metal constituents from the solids. The 6 pH of the resultant aqueous solution containing the water
shown that only a portion of the potassium carbonate or 11 other alkali metal constituents is normally recovered and 12 that substantial quantities of makeup alkali metal com- ¦
13 pounds are therefore required. This adds appreciably to the cost of such operations.
SUMMARY OF THE INVENTION
16 The present invention provides an improved pro-17 cess for the recovery of alkali metal constituents from 18 char particles produced during coal gasification and other 19 conversion processes carried out in the presence of an alkali metal-containing catalyst. In accordance with the 21 invention, it has now been found that increased amounts 22 f alkali metal constituents can be effectively recovered 23 from particles containing alkali metal residues produced 24 during coal gasification and related high temperature conversion processes by mixing the particles with calcium 26 oxide or a solid calcium-containin~ compound that decom-27 poses upon heating to form calcium oxide, and heating the 28 resultant mixture of solids to a temperature sufficiently high to cause calcium oxide to react with water insoluble alkali metal aluminosilicates in the alkali metal residues ~i~gS4Z
1 to produce reaction products containing water insoluble 2 calcium silicates and water soluble alkali metal alumi-, 3 nates. The reaction products are contacted with water, 4 which leaches the alkali metal aluminates and other water soluble alkali metal constituents from the solids. The 6 pH of the resultant aqueous solution containing the water
7 soluble alkali metal aluminates is sufficiently lowered
8 to cause aluminum hydroxide to precipitate, thereby
9 forming a solution containing alkali metal constituents substantially free of aluminum. These alkali metal con-11 stituents are then used as at least a portion of the 12 alkali metal constituents which co~prise the alkali metal-13 containing catalyst. Preferably, such use is achieved 14 by recycling the solution directly to the conversion pro-cess. If desired, however, the alkali metal constituents 16 may first be recovered from the solution and then used in 7 the conversion process.
~8 The invention is based in part upon studies of 19 the reactions that catalysts containing alkali metal con-stituents undergo during coal gasification and similar 21 operations. Coal and other carbonaceous solids used in 22 such operations normally contain mineral constituents 23 that are converted to ash during the gasification process.
24 Although the composition of ash varies, the principal con-stituents, expressed as oxides, are generally silica, 26 alumina and ferric oxide. The alumina-is usually present 27 in the ash in the form of aluminosilicates. Studies have 28 indicated that at least a portion of the alkali metal com-.
29 pounds, such as potassium carbonate, that are used as gasiflcation catalyst constituents react with the alumino-i~954Z
1 silicates and other ash constituents to form alkàli metal 2 residues containing water soluble alkali metal compounds 3 such as carbonates, sul~ates, sulfides, sulfites and the 4 like and water insoluble, catalytically inactive materials such as potassium aluminosilicates and other alkali metal 6 aluminosilicates. Unless the alkali metal constituents in 7 these insoluble aluminosilicates can be reco~ered, they 8 are lost from the process and must be replaced by makeup 9 alkali metal compounds. The process of this invention allows recovery of these alkali metai constituents and 11 thereby decreases the costs incurred by utilizing large 12 amounts of makeup alkali metal compounds. As a result, 13 the invention makes possible substantial savings in 14 gasification and other conversion operations carried out in the presence of alkali metal-containing catalysts and 16 permits the generation of product gases and/or liquids at 7 significantly lower cost than would otherwise be the case.
-19 The drawing is a schematic flow diagram of a ~ catalytic coal gasification process in which alkali metal 21 constituents of the catalyst are recovered and reused in 22 the process.
24 The process depicted in the drawing is one for the production of methane by the gasification of bitumi-26 nous coal, subbituminous coal, lignite or similar carbo-27 naceous solids with steam at high temperatures in the 28 presence of a carbon-alkali metal catalyst prepared by . .
29 impregnatin~ the feed solids with a solution of an alkali metal compound or a mixture of such compounds and there-' , ~11954Z
1 after heating the impregnated material to a temperature 2 sufficient to produce an interaction between the alkali . . ,: . .
3 metal and-the carbon present. It will be understood that 4 the alkali metal recovery system disclosed is not res-tricted to this particular gasification process and that 6 it can be employed in conjunction with any of a variety of 7 other conversion processes in which alkali metal compounds ; 8 or carbon-alkali metal catalysts are used to promote the 9 reaction of steam, hydrogen, oxygen or the like with car-bonaceous feed materials to produce a char, coke or similar 11 solid product containing alkali metal residues from 12 which alkali metal compounds are recovered for reuse as 13 the catalyst or a constituent of the catalyst. It can 14 be employed, for example, for the recovery of alkali ~ metal compounds from various processes for the gasifica-16 tion of coal, petroleum coke, lignite, organic waste 17 materials and similar solids feed streams which produce . ~ , 18 spent carbonaceous solids at temperatures below the ash 19 fusion point. Other conversion processes with which it may be used include operations for the carbonization of 21 coal and similar feed solids, for the liquefaction o~
22 coal and related carbonaceous feed materials, for the 23 retorting of oil shale, for the partial combustion of 24 carbonaceous feed materials, and the like. Such pro-cesses have been disclosed in the literature and will be 26 familiar to those skilled in the art 2? In the process depicted in the drawing, a solid 28 carbonaceous feed material such as bituminous coal, sub-29 bituminous coal, lignite or the like that has been crushed to a particle size of about 8 mesh or smaller on the U.S.
- 7 ~
1 Sieve Series Scale is passed into line lO from a feed pre-2 ; ;paration plant or storage facility that is not shown in the drawing. The solids introduced into line lO are fed 4 into a hopper or similar vessel ll from which they are passed through line 12 into feed preparation zone 14.
6 This zone contains a screw conveyor or similar device 15 7 that is powered by a motor 16, a series of spray nozzles 8 or similar devices 17 for the spraying of alkali metal-9 containing solution supplied through line 18 onto the solids as they are moved through the preparation zone by 11 the conveyor, and a similar set of nozzles or the like 12 l9 for the introduction of steam into the preparation 13 zone. The steam, supplied through line 20, serves to 14 heat the impregnated solids and drive off the moisture.
Steam is withdrawn from zone 14 through line 21 and 16 passed to a condenser not shown, from which it may be 17 recovered for use as makeup water or the like. The 18 majority of the alkali metal-containing solution is 19 recycled through line 79 from the alkali metal recovery section of the process, which is described in detail 21 hereafter. Any makeup solution required may be intro- ¦
22 duced into line 79 via line 13.
23 It is preferred that sufficient alkali metal-24 containing solution be introduced into feed preparation zone 14 to provide from about l to about 50 weight per-26 cent of the alkali metal compound or mixture of such . . , 27 compounds on the coal or other carbonaceous solids. From 28 about l to about 15 weight percent is generally adequate.
29 The dried impregnated solid particles prepared in zone 14 are withdrawn through line 24 and passed to a closed ~9S4~i~
., 1 hopper or similar vessel 25. From here they are dis-2 charged through a star wheel feeder or equivalent device 3 26 in line 27 at an ele~ated pressure sufficient to per-4 mit their entrainment into a stream of highpressure steam, S recycle product gas, inert gas or other carrier gas intro-6 duced into line 29 via line 28. The carrier gas and 7 entrained solids are passed through line 29 into manifold ; 8 30 and fed from the manifold through feed lines 31 and ; g nozzles, not shown in the drawing, into gasifier 32. In lieu of or in addition to hopper 25 and star wheel feeder 11 26, the feed system may employ parallel lock hoppers, 12 pressurized hoppers, aerated standpipes operated in 13 series, or other apparatus to raise the input feed solids 14 stream to the required pressure level.
~ It is generally preferred to operate the 16 gasifier 32 at a pressure between about 500 and about 17 2000 psig. The carrier gas and entrained solids will 18 normally be introduced at a pressure somewhat in excess 19 Of the gasifier operating pressure. The carrier gas may be preheated to a temperature in excess of about 300 F.
21 but below the initial softening point of the coal or 22 other feed material employed. Feed particles may be sus-23 pended in the carrier gas in a concentration between about 24 0.2 and about 5.0 pounds of solid feed material per pound of carrier gas. The optimum ratio for a particular system 26 will depend in part upon the feed particle size and den-`27 sity, the molecular weight of the gas employed, the tem-28 perature of the solid feed material and input gas stream, 29 the amount of alkali metal compound employed and other ~ factors. In general, ratios between about 0.5 and about 11195L~Z
1 4 0 pounds of solid feed material per pound of carrier 2 gas are pre~erred.
3 ~Gasifier 32 comprises a refractory-lined vessel 4 containing a fluidized bed of carbonaceous solids extend-ing upward within the vessel above an internal grid or 6 similar distribution device not shown in the drawing. The 7 bed is maintained in the fluidized state by means of 8 steam introduced through line 33, manifold 34 and peri-. 9 pherally spaced injection lines and nozzles 35 and by means of recycle hydrogen and carbon monoxide introduced 11 through bottom inlet line 36. The particular in~ection 12 system shown in the drawing is not critical and hence 13 other methods for injecting the steam and recycle hydrogen 14 and carbon monoxide may be employed. In some instances, ~ for example, it may be preferred to introduce both the 16 steam and recycle gases through multiple nozzles to 17 obtain more uniform distribution of the injected fluid 18 and reduce the possibility of channeling and related 19 problems. The space velocity of the rising gases within the fluidized bed will normally be between about 300 and 21 about 3000 volumes of steam and recycle hydrogen and 22 carbon monoxide per hour per volume of fluidized solids.
23 The injected steam reacts with carbon in the 24 feed material in the M uidized bed in gasifier 32 at a temperature within the range between about 800 F. and 26 about 1600 F. and at a pressure between about 500 and ?7 about 2000 psig. Due to the equilibrium condition exist-28 ing in the bed as a result of the presence of the carbon-29 aikali metal catalyst and the recycle hydrogen and carbon monoxide injected near the lower end of the bed, the 11~9~42:
1 reaction products will normally consist essentially of 2 m;ethane and carbon dioxide. Competing reactions, which 3 in the absence of the catalyst and the recycle gases ~
4 would ordinarily tend to produce additional hydrogen and carbon monoxide, are suppressed. The ratio of methane to 6 carbon dioxide in the raw product gas thus formed will 7 preferably range from about l to about 1.4 moles per mole, 8 depending upon the amount of hydrogen and oxygen in the ... . . . .
9 feed coal-or other carbonaceous solids. The coal employed may be considered as an oxygenated hydrocarbon for pur-11 poses of describing the reaction. Wyodak coal, for 12 example, may be considered as having the approximate for-13 mula CHo 84o 20' based on the ultimate analysis of mois-14 ture and ash-free coal and neglecting nitrogen and sulfur.
~ The reaction of this coal with steam to produce methane 16 and carbon dioxide is as follows:
17 . 4 H20(g) + l-8 CHo.84o 20 o-8 C02 + CH4-18 Under the same gasification conditions, coals of higher 19 oxygen content will normally produce lower methane to carbon dioxide ratios and those of lower oxygen content 21 will yield higher methane to carbon dioxide ratios.
22 The gas leaving the fluidized bed in gasifier 23 32 passes through the upper section of the gasifier~
24 which serves as a disengagement zone where particles too heavy to be entrained by the gas leaving the vessel are 26 returned to the bed. If desired, this disengagement 27 zone may include one or more cyclone separators or the 28 like for removing relatively large particles from the gas.
29 The gas withdrawn from the upper part of the gasifier through line 37 will normally contain methane and carbon 1 dioxide produced by reaction of the steam with carbon, 2 hvdrogen and carbon monoxide introduced into the gasifier 3 as recycle gas, unreacted steam, hydrogen sulfide, ammonia 4 and other contaminants formed from the sulfur and nitrogen contained in the feed material, and entrained fines. This 6 gas is introduced into cyclone separator or similar device 7 38 for removal of the larger fines. The overhead gas 8 then passes through line 39 into a second separator 41 ; 9 where smaller particles are removed. The gas from which the solids have been separated is taken overhead from 11 separator 41 through line 42 and the fines are discharged 12 downward through dip legs 4O and 43. These fines may be 13 returned to the gasifier or passed to the alkali metal ! ~ 14 recovery section of the process as discussed hereafter.
~ After entrained solids have been separated 16 from the raw product gas as described above, the gas 17 stream may be passed through suitable heat exchange equip-. ~ . .. .
18 ment for the recovery of heat and then processed for the 19 removal of acid gases. Once this has been accomplished, the remaining gas, consisting primarily of methane, 21 hydrogen and carbon monoxide, may be cryogenically 22 separated into a product methane stream and a recycle 23 stream of hydrogen and carbon monoxide, which is re-24 turned to the gasifier through line 36. Conventional gas processing equipment can be used. Since a detailed 26 description of this downstream gas processing portion of 27 the process is not necessary for an understanding of the 28 invention, it has been omitted.
The fluidized bed in gasifier 32 is comprised of char particles formed as the solid carbonaceous feed ~1954Z
1 material undergoes gasification. The composition of the 2 char particles will depend upon the amount of mineral 3 matter present in the carbonaceous material fed to the 4 gasifier, the amount of the alkali metal compound or mix-ture of such compounds impregnated onto the feed material, 6 and the degree of gasification that the char particles 7 undergo while in the fluidized bed. The lighter char 8 particles, which will have a relatively high content of ... . .
9 carbonaceous material, will tend to remain in the upper portion of the fluidized bed. The heavier char particles, 11 which will contain a relatively small amount of carbona-12 ceous material and a relatively large amount of ash and alkali metal residues will tend to migrate toward the 14 bottom of the fluidized bed. A portion of the heavier ~ char particles are normally withdrawn from the bottom 16 portion of the fluidized bed in order to eliminate ash 17 and thereby prevent it from buildling up within the gasi-18 fier and other vessels in the system.
19 Since the cost of the alkali metal constituents comprising the gasification catalyst is a significant fac-21 tor in determining the overall cost of the gasification 22 process, it is particularly important that these consti-23 tuents be recovered and reused. It has been proposed to 24 recover these alkali metal constituents as they are with-drawn from the gasifier with the char particles by leach-26 ing them out with water. Studies have indicated that . , .
27 these alkali metal constituents are generally present in 28 part as carbonates, sulfates, sulfides, sulfites and 29 other water soluble compounds that can be recovered by water washing. Experience has shown, however, that only ~.~1954Z :
1 a portion of the alkali metal carbonates or other alkali 2 ;~etal constituents is normally recovered and that a sub-3 stantial quantity of makeup alkali metal compounds is 4 therefore required.
The process of this invention is based in part 6 upon studies of the reactions that catalysts containing 7 alkali metal constituents undergo during coal gasifica-. . .. ~
8 tion and similar operations. Coal and other carbonaceous ,.. . , 9 solids used in such operations normally contain mineral i, . ~ 1 1~ constituents that are converted to ash during the gasi-11 fication process. Although the composition of the ash 12 varies, the principle constituents, expressed as oxides, I
13 are generally silica, alumina and ferric oxide. The J
14 alumina is usually present in the ash in the form of 1~ aluminosilicates. Studies have indicated that at least 16 a portion of the alkali metal compounds, such as potas- -17 sium carbonate, sodium carbonate and the like, that are 18 used as gasification catalyst constituents react with 19 the aluminosilicates and other ash constituents to form alkali metal residues containing water soluble alkali 21 metal compounds such as carbonates, sulfates, sulfides, 22 sulfites and the like and water insoluble, catalytically 23 inacti~e materials such as potassium aluminosilicates 24 and other alkali metal aluminosilicates.
It has been found that from about lO to about 26 5O percent by weight of the potassium carbonate or other 27 alkali metal compound employed to impregnate coal or 28 similar feed material prior to gasification will react 29 with the aluminosilicates in the ash during gasification to form water insoluble alkali metal aluminosilicates, ~19S4Z
1 which cannot normally be recovered from the ash by water 2 washing. Preliminary studies tend to indicate that when 3 potassium carbonate is utllized to impregnate the coal, 4 the major constituent of the water insoluble potassium aluminosilicates produced is a synthetic kaliophilite, which has the chemical formula KAlSiO4.
7 To improve the economics o~ the catalytic gasi-8 fication process described above and other catalytic con-..... . .
. 9 version processes where water insoluble alkali metal residues are formed, it is desirable to recover as much 11 as possible of the alkali metal constituents from the 3 12 insoluble residues and reuse them as catalyst constituents 13 in the conversion process, thereby decreasing the amount 14 f costly makeup alkali metal compounds needed. It has 1~ been found that a substantial amount of the alkali metal ~6 constituents in the water insoluble alkali metal residues 17 withdrawn with the char and ash from the gasifier of the 18 above described process or the reaction zone of other 19 conversion processes can be recovered for reuse in the conversion process by mixing the particles withdrawn 21 from the reaction zone with calcium oxide or a solid 22 calcium-containing compound that decomposes upon heating 23 to ~orm calcium oxide, and heating the resultant mixture 24 of solids to a temperature sufficiently high to cause calcium oxide to react with water insoluble alkali metal 26 aluminosilicates in the alkali metal residues to produce 27 reaction products containing water soluble alkali metal 28 aluminates and water insoluble calcium silicates. The 29 reaction products are contacted with water, which leaches the alkali metal aluminates and other water soluble alkali ~1954Z
1 metal constituents from the solids. The pH of the resul-2 tant aqueous solution containing the water soluble alkali 3 metal aluminates is sufficiently lowered to cause aluminum 4 hydroxide to precipitate, thereby forming a solution con-taining alkali metal constituents substantially free of 6 aiuminum. These alkali metal constituents are then used 7 in the conversion process as at least a portion of the 8 alkali metal constituents which comprise the alkali metal-.,, 9 containing catalyst. Preferably, such use is achieved by recycling the solution directly to the conversion process.
11 If desired, however, the alkali metal constituents may 12 first be recovered from the solution and then used in the 13 conversion process. -14 Referring again to the drawing, char particles 1~ containing carbonaceous material, ash and alkali metal 16 residues are continuously withdrawn through line 44 from 1~ the bottom of the fluidized bed in gasifier 32. The par-18 ticles flow downward through line 44 countercurrent to a 19 stream of steam or other elutriating gas introduced - 20 through line 45. Here a preliminary separation of solids 21 based on differences in size and density takes place.
22 The lighter particles having a relatively large amount of 23 carbonaceous material tend to be returned to the gasifier 24 and the heavier particles having a relatively high content of ash and alkali métal residues continue downward through 26 line 46 containing valve 55 into hopper 56. Char fines 27 recovered from the raw product gas through dip legs 4O
28 and 43, and line 57 may also be fed into the hopper.
29 Thè solid particles in hopper 56, which contain both water soluble and water insoluble alkali metal resi-- 16 - 1, ~19S4Z
1 dues, are passed into line 58 where they are mixed with a 2 calcium-containing compound introduced into line 58 from .
3 hopper 59 via line 60. The solid calcium-containing com-4 pound may be calcium oxide or any calcium compound that decomposes to form calcium oxide when subjected to rela-6 tively high temperatures~ The calcium-containing compound 7 may be inorganic or organic and may, for example, be cal-8 cium hydroxide, calcium acetate, calcium oxalate, calcium ... .
- 9 formate, calcium carbonate, dolomite and the like. The actual calcium-containing compound used will depend pri-11 marily upon its availability and cost. The amount o~ the 12 calcium-containing compound required will depend in part 13 on the amount of silicates in the particulate matter with ' 14 which it is mixed. If desired, a mixture of two or more 1-S calcium-containing compounds may be used in lieu of a 16 single compound.
- .
17 The mixture of char particles containin~ the 18 alkali metal residues and the calcium-containing compound 19 is passed through line 61 into rotary kiln or similar heating device 62 where it is subjected to temperatures 21 sufficiently high to cause the alkali metal aluminosili-22 cates in the residues to react with calcium oxide, which 23 is formed by the thermal decomposition of the calcium-24 containing compound unless that compound is calcium oxide itself. The reaction converts the water insoluble alkali .
26 metal aluminosilicates into reaction products containing 27 water insoluble calcium silicates and water soluble alkali 28 metal aluminates. The reaction products are subsequently 29 treated, as described hereafter, to recover alkali metal constituents that are recycled to the gasification ~954Z
1 process where they serve as at least a portion of the 2 ;-~;al~ali metal constituents which comprise the alkali 3 metal-containing catalyst.
4 The mixture of solids introduced into the rotary kiln will normally be subjected to a temperature 6 ranging from about 1600 F. to about 2600 F. Preferably, 7 the mixture is heated to the sintering temperature~ which 8 ~ causes the surface of the particles to soften thereby in-9 creasing the tendency of the particles to agglomerate or stick together. Sintering imparts mobility to the calcium 11 ions present and apparently enables them to easily satu-12 rate -the atomic structure of the alkali metal aluminosili-13 cates and displace alkali metal constituents and alumina 14 to form water insoluble calcium silicates. Sintering 1~ may be effectively accomplished in a countercurrent rotary 16 kiln in which the fuel is passed through the kiln in a 17 direction opposite to that in which the mixture of solids 18 is passed. In lieu of the rotary kiln any furnace or 19 similar heating device may be used as long as the required temperatures are obtainable. If desirable, the tempera-21 ture in the heating device may be raised above the sin-22 tering temperature to convert the mixture of solids into 23 a liquid mass in which the desired reactions will take 24 place more rapidly. This procedure, however, may not be advantageous since the liquid upon cooling will form a 26 glass-like solid from which it may be difficult to water 27 leach soluble alkali metal constituents.
28 An example of one reaction that is believed to 29 take place in rotary kiln 62 is set forth below. The symbol "M" is used to represent any alkali metal cation.
The actual alkali metal present will depend on the type 2 ;~;of alkali metal compound utilized as a constituent of 3 the al~ali metal-containing gasification catalyst.
4 ~AlSiO4 + 2CaO ~ MAlO2 + Ca2SiO4 As can be seen from the above equation, an alkali metal 6 aluminosilicate reacts wlth calcium oxide to produce an 7 alkali metal aluminate and dicalcium silicate. It will 8 be understood that the above equation represents only ~ one reaction that may occur in the rotary kiln. Other reactions involving more complicated aluminosilicates 11 and other insoluble constituents of the alkali metal 12 residues may also take place.
13 The sintered mixture of solids from rotary kiln 14 62 is cooled and passed through line 63 to ball mill or similar crushing device 64 where the solids are pulver-16 ized, ground, or otherwise crushed to a size suitable 17. for water leaching. It is desirable to produce rela-18 tively small particles since they will provide a high 19 surface area for more effective water leaching. The actual size is determined in part by balancing the cost 21 of crushing with the effectiveness of the water leaching.
22 Preferably, the particles will be crushed to a size 23 smaller than about 60 mesh on the U.S. Sieve Series 24 Scale.
The crushed solids are removed from ball mill 26 64 and passed through line 65 to water wash zone 66, 27 which will normally comprise a multistage countercurrent 28 extraction system in which the solids are countercur-29 rently contacted with water introduced through line 67.
The water leaches alkali metal aluminates and other ~9S4Z
il 1 water soluble alkali metal constituents from the solids, 2 ~ ; thereby producing an aqueous solution of such consti-3 tuents, which is removed from the water wash zone 4 thrpugh line 68 and will normally have a pH of about 12.0 or less. Spent solids are removed from the water 6 wash zone via line 69 and will contain, among other sub-7 stances, ash, calcium silicates and aluminum hydroxide.
8 These solids may be disposed of as land fill or further 9 processed to recover valuable components such as calcium silicates, which may subsequently be used in the manu-11 facture of cement.
12 The aqueous solution containing alkali metal 13 aluminates and other water soluble alkali metal consti-tuents removed from water wash zone 66 via line 68 is 1~ passed through line 70 to contactor or similar vessel 71.
16 Here the pH of the solution is lowered to a value in the 17 range between about lO.0 and about 4.0, preferably between 18 about 9.0 and about 5.0, by contacting it with a carbon ¦
19 dioxide-containing gas. The aqueous solution is passed downward through the contacting zone in contactor 71 21 where it comes in contact with an upflowing gas that con-22 tains carbon dioxide. The carbon dioxide-containing gas 23 is injected into the bottom of the contactor through line 24 72. As the carbon dioxide gas rises upward through the downflowing aqueous solution, the carbon dioxide in the 26 gas reacts with the alkali metal aluminates in the solu-27 tion to form alkali metal carbonates and water insoluble 28 aluminum hydroxide. If the partial pressure of carbon 29 dioxide is sufficiently high and the temperature in the contactor is low, alkali metal bicarbonates may also form.
l~l9S4~' .. . .
1 - A gas depleted in carbon dioxide is withdrawn 2 --overhead of contactor 71 through line 73 and either 3 vented to the atmosphere, further processed for the 4 recovery and reuse of carbon dioxide, or otherwise dis-posed of. Any carbon dioxide-containing gas, including 6 pure carbon dioxide and air, may be used. It is : 7 preferred, however, to utiliz~ the flue gas produced - 8 from the fuel combustion taking place in rotary kiln 62.
.... . !
9 The contacting vessel utilized does not necessarily have , .. .
to be of the type shown in the drawing but may be any - ~ 11 type of vessel that allows for fairly good contacting 12 between the carbon dioxide-containing gas and the aqueous 13 solution containing alkali metal aluminates. A tank in 14 which the carbon dioxide-containing gas is bubbled i5 through the aqueous solution may be sufficient for pur-16 poses of the invention.
17 The purpose of the above-described step of the 18 alkali metal recovery process is to lower the p~ of the 19 aqueous solution containing the alkali metal aluminates so that substantially all of the aluminum is removed 21 from the solution in the form of a water insoluble pre-22 cipitate of aluminum hydroxide, thereby leaving in solu- i 23 tion aluminum free alkali metal constituents that are 24 subsequently recovered and used as constituents of the gasification catalyst. Removal of aluminum from the 26 alkali metal constituents before their use in the gasi-27 fication catalyst is desirable to help avoid the possible 28 formation of additional alkali metal aluminosilicates in 29 the gasifier by the reaction of the aluminum with silica in the feed material and alkali metal constituents of 1~1954Z
1 the catalyst. It will be understood that for purposes 2 .;of the invention any method of lowering pH may be used.
3 For example, instead of contacting the aqueous effluent 4 from water wash zone 66 with a carbon dioxide-containing gas, the effluent may be mixed with sufficient quanti-6 ties of sulfuric acid, nitric acid or the like to lower 7 the pH to the desired value.
8 Referring again to the drawing, the effluent ..... . .
9 from contacting vessel 71, which contains alkali metal carbonates and other water soluble alkali metal consti-11 tuents, and aluminum hydroxide, is withdrawn from the 12 bottom of the vessel through line 74 and passed to rotary 13 filter or similar liquids-solids separation device 75 where the solid aluminum hydroxide is separated from the j~ aqueous solution and then passed through line 76 to 16 : rotary kiln or similar heating device 77 where it is cal-17 cined at high temperatures to produce alumina, which is 18 recovered via line 78 and may be soId as a byproduct.
19 The sale of this material may produce an additional return from the process and thus reduce the overall cost 21 of the product gas.
22 A solids-free aqueous solution containing 23 alkali metal carbonates and other water soluble alkali 24 metal compounds is removed from filter 75 through line 79 and recycled to feed preparation zone 14 via line 18 26 where the coal or similar carbonaceous feed material is 27 impregnated with the alkali metal compounds in the solu-2~ tion. If the concentration of alkali metal compounds 29 in the recycle solution is undesirably low, the solution may be concentrated by removing excess water before it ~9s~z 1 is returned to the feed preparation zone. It will be 2 understood that the exact alkali metal compound or com-3 pounds present in the recycled solution will depend on 4 the substance used to lower the pH of the aqueous efflu-.
ent from water wash zone 66. For example, if nitric acid 6 is used in lieu of a carbon dioxide-containing gas, the 7 recycled solution will contain alkali metal nitrates 8 instead of carbonates.
The embodiment of the invention shown in the . , , drawing and discussed above is one that allows for the 11 recovery of alumina as a byproduct of the alkali metal 12 recovery process. If recovery of alumina is undesirable 13 for any reason, the embodiment of the invention depicted 14 in the drawing may be simplified by eliminating water wash zone 66 and rotary kiln 81 and replacing contactor 16 71 with a series of stirred tanks through which water and the crushed solids from ball mill 64 are passed counter-:. . .
18 currently to the carbon dioxide-containing gas. The 1~ slurry effluent from the series of stirred tanks is then passed to rotary filter 75 where the solids are separated 21 from the aqueous solution, which is recycled to the feed 22 preparation zone. The solids, which will contain, among 23 other substances, ash, calcium silicates and aluminum 24 hydroxide, may be used as landfill or otherwise disposed of.
26 It will be apparent from the foregoing that the -~27 process of the invention provides an improved alkali metal 28 recovery system, which makes it possible to significantly 29 increase the amount of alkali metal constituents that are recovered from alkali metal residues produced during cata-- 2~ -11~954;~
, 1 lytic gasification and similar hi~h temperature catalytic .2 .~onversion processes. As a result, the need for costly 3 makeup alkali metal compounds is reduced, thereby lowering . 4 the overall cost of the conversion process.
. .
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`'" .` . " ' . .
~''".,, ' ' . ' ' '' , ..', ' ~', .
.
Il Il .
~8 The invention is based in part upon studies of 19 the reactions that catalysts containing alkali metal con-stituents undergo during coal gasification and similar 21 operations. Coal and other carbonaceous solids used in 22 such operations normally contain mineral constituents 23 that are converted to ash during the gasification process.
24 Although the composition of ash varies, the principal con-stituents, expressed as oxides, are generally silica, 26 alumina and ferric oxide. The alumina-is usually present 27 in the ash in the form of aluminosilicates. Studies have 28 indicated that at least a portion of the alkali metal com-.
29 pounds, such as potassium carbonate, that are used as gasiflcation catalyst constituents react with the alumino-i~954Z
1 silicates and other ash constituents to form alkàli metal 2 residues containing water soluble alkali metal compounds 3 such as carbonates, sul~ates, sulfides, sulfites and the 4 like and water insoluble, catalytically inactive materials such as potassium aluminosilicates and other alkali metal 6 aluminosilicates. Unless the alkali metal constituents in 7 these insoluble aluminosilicates can be reco~ered, they 8 are lost from the process and must be replaced by makeup 9 alkali metal compounds. The process of this invention allows recovery of these alkali metai constituents and 11 thereby decreases the costs incurred by utilizing large 12 amounts of makeup alkali metal compounds. As a result, 13 the invention makes possible substantial savings in 14 gasification and other conversion operations carried out in the presence of alkali metal-containing catalysts and 16 permits the generation of product gases and/or liquids at 7 significantly lower cost than would otherwise be the case.
-19 The drawing is a schematic flow diagram of a ~ catalytic coal gasification process in which alkali metal 21 constituents of the catalyst are recovered and reused in 22 the process.
24 The process depicted in the drawing is one for the production of methane by the gasification of bitumi-26 nous coal, subbituminous coal, lignite or similar carbo-27 naceous solids with steam at high temperatures in the 28 presence of a carbon-alkali metal catalyst prepared by . .
29 impregnatin~ the feed solids with a solution of an alkali metal compound or a mixture of such compounds and there-' , ~11954Z
1 after heating the impregnated material to a temperature 2 sufficient to produce an interaction between the alkali . . ,: . .
3 metal and-the carbon present. It will be understood that 4 the alkali metal recovery system disclosed is not res-tricted to this particular gasification process and that 6 it can be employed in conjunction with any of a variety of 7 other conversion processes in which alkali metal compounds ; 8 or carbon-alkali metal catalysts are used to promote the 9 reaction of steam, hydrogen, oxygen or the like with car-bonaceous feed materials to produce a char, coke or similar 11 solid product containing alkali metal residues from 12 which alkali metal compounds are recovered for reuse as 13 the catalyst or a constituent of the catalyst. It can 14 be employed, for example, for the recovery of alkali ~ metal compounds from various processes for the gasifica-16 tion of coal, petroleum coke, lignite, organic waste 17 materials and similar solids feed streams which produce . ~ , 18 spent carbonaceous solids at temperatures below the ash 19 fusion point. Other conversion processes with which it may be used include operations for the carbonization of 21 coal and similar feed solids, for the liquefaction o~
22 coal and related carbonaceous feed materials, for the 23 retorting of oil shale, for the partial combustion of 24 carbonaceous feed materials, and the like. Such pro-cesses have been disclosed in the literature and will be 26 familiar to those skilled in the art 2? In the process depicted in the drawing, a solid 28 carbonaceous feed material such as bituminous coal, sub-29 bituminous coal, lignite or the like that has been crushed to a particle size of about 8 mesh or smaller on the U.S.
- 7 ~
1 Sieve Series Scale is passed into line lO from a feed pre-2 ; ;paration plant or storage facility that is not shown in the drawing. The solids introduced into line lO are fed 4 into a hopper or similar vessel ll from which they are passed through line 12 into feed preparation zone 14.
6 This zone contains a screw conveyor or similar device 15 7 that is powered by a motor 16, a series of spray nozzles 8 or similar devices 17 for the spraying of alkali metal-9 containing solution supplied through line 18 onto the solids as they are moved through the preparation zone by 11 the conveyor, and a similar set of nozzles or the like 12 l9 for the introduction of steam into the preparation 13 zone. The steam, supplied through line 20, serves to 14 heat the impregnated solids and drive off the moisture.
Steam is withdrawn from zone 14 through line 21 and 16 passed to a condenser not shown, from which it may be 17 recovered for use as makeup water or the like. The 18 majority of the alkali metal-containing solution is 19 recycled through line 79 from the alkali metal recovery section of the process, which is described in detail 21 hereafter. Any makeup solution required may be intro- ¦
22 duced into line 79 via line 13.
23 It is preferred that sufficient alkali metal-24 containing solution be introduced into feed preparation zone 14 to provide from about l to about 50 weight per-26 cent of the alkali metal compound or mixture of such . . , 27 compounds on the coal or other carbonaceous solids. From 28 about l to about 15 weight percent is generally adequate.
29 The dried impregnated solid particles prepared in zone 14 are withdrawn through line 24 and passed to a closed ~9S4~i~
., 1 hopper or similar vessel 25. From here they are dis-2 charged through a star wheel feeder or equivalent device 3 26 in line 27 at an ele~ated pressure sufficient to per-4 mit their entrainment into a stream of highpressure steam, S recycle product gas, inert gas or other carrier gas intro-6 duced into line 29 via line 28. The carrier gas and 7 entrained solids are passed through line 29 into manifold ; 8 30 and fed from the manifold through feed lines 31 and ; g nozzles, not shown in the drawing, into gasifier 32. In lieu of or in addition to hopper 25 and star wheel feeder 11 26, the feed system may employ parallel lock hoppers, 12 pressurized hoppers, aerated standpipes operated in 13 series, or other apparatus to raise the input feed solids 14 stream to the required pressure level.
~ It is generally preferred to operate the 16 gasifier 32 at a pressure between about 500 and about 17 2000 psig. The carrier gas and entrained solids will 18 normally be introduced at a pressure somewhat in excess 19 Of the gasifier operating pressure. The carrier gas may be preheated to a temperature in excess of about 300 F.
21 but below the initial softening point of the coal or 22 other feed material employed. Feed particles may be sus-23 pended in the carrier gas in a concentration between about 24 0.2 and about 5.0 pounds of solid feed material per pound of carrier gas. The optimum ratio for a particular system 26 will depend in part upon the feed particle size and den-`27 sity, the molecular weight of the gas employed, the tem-28 perature of the solid feed material and input gas stream, 29 the amount of alkali metal compound employed and other ~ factors. In general, ratios between about 0.5 and about 11195L~Z
1 4 0 pounds of solid feed material per pound of carrier 2 gas are pre~erred.
3 ~Gasifier 32 comprises a refractory-lined vessel 4 containing a fluidized bed of carbonaceous solids extend-ing upward within the vessel above an internal grid or 6 similar distribution device not shown in the drawing. The 7 bed is maintained in the fluidized state by means of 8 steam introduced through line 33, manifold 34 and peri-. 9 pherally spaced injection lines and nozzles 35 and by means of recycle hydrogen and carbon monoxide introduced 11 through bottom inlet line 36. The particular in~ection 12 system shown in the drawing is not critical and hence 13 other methods for injecting the steam and recycle hydrogen 14 and carbon monoxide may be employed. In some instances, ~ for example, it may be preferred to introduce both the 16 steam and recycle gases through multiple nozzles to 17 obtain more uniform distribution of the injected fluid 18 and reduce the possibility of channeling and related 19 problems. The space velocity of the rising gases within the fluidized bed will normally be between about 300 and 21 about 3000 volumes of steam and recycle hydrogen and 22 carbon monoxide per hour per volume of fluidized solids.
23 The injected steam reacts with carbon in the 24 feed material in the M uidized bed in gasifier 32 at a temperature within the range between about 800 F. and 26 about 1600 F. and at a pressure between about 500 and ?7 about 2000 psig. Due to the equilibrium condition exist-28 ing in the bed as a result of the presence of the carbon-29 aikali metal catalyst and the recycle hydrogen and carbon monoxide injected near the lower end of the bed, the 11~9~42:
1 reaction products will normally consist essentially of 2 m;ethane and carbon dioxide. Competing reactions, which 3 in the absence of the catalyst and the recycle gases ~
4 would ordinarily tend to produce additional hydrogen and carbon monoxide, are suppressed. The ratio of methane to 6 carbon dioxide in the raw product gas thus formed will 7 preferably range from about l to about 1.4 moles per mole, 8 depending upon the amount of hydrogen and oxygen in the ... . . . .
9 feed coal-or other carbonaceous solids. The coal employed may be considered as an oxygenated hydrocarbon for pur-11 poses of describing the reaction. Wyodak coal, for 12 example, may be considered as having the approximate for-13 mula CHo 84o 20' based on the ultimate analysis of mois-14 ture and ash-free coal and neglecting nitrogen and sulfur.
~ The reaction of this coal with steam to produce methane 16 and carbon dioxide is as follows:
17 . 4 H20(g) + l-8 CHo.84o 20 o-8 C02 + CH4-18 Under the same gasification conditions, coals of higher 19 oxygen content will normally produce lower methane to carbon dioxide ratios and those of lower oxygen content 21 will yield higher methane to carbon dioxide ratios.
22 The gas leaving the fluidized bed in gasifier 23 32 passes through the upper section of the gasifier~
24 which serves as a disengagement zone where particles too heavy to be entrained by the gas leaving the vessel are 26 returned to the bed. If desired, this disengagement 27 zone may include one or more cyclone separators or the 28 like for removing relatively large particles from the gas.
29 The gas withdrawn from the upper part of the gasifier through line 37 will normally contain methane and carbon 1 dioxide produced by reaction of the steam with carbon, 2 hvdrogen and carbon monoxide introduced into the gasifier 3 as recycle gas, unreacted steam, hydrogen sulfide, ammonia 4 and other contaminants formed from the sulfur and nitrogen contained in the feed material, and entrained fines. This 6 gas is introduced into cyclone separator or similar device 7 38 for removal of the larger fines. The overhead gas 8 then passes through line 39 into a second separator 41 ; 9 where smaller particles are removed. The gas from which the solids have been separated is taken overhead from 11 separator 41 through line 42 and the fines are discharged 12 downward through dip legs 4O and 43. These fines may be 13 returned to the gasifier or passed to the alkali metal ! ~ 14 recovery section of the process as discussed hereafter.
~ After entrained solids have been separated 16 from the raw product gas as described above, the gas 17 stream may be passed through suitable heat exchange equip-. ~ . .. .
18 ment for the recovery of heat and then processed for the 19 removal of acid gases. Once this has been accomplished, the remaining gas, consisting primarily of methane, 21 hydrogen and carbon monoxide, may be cryogenically 22 separated into a product methane stream and a recycle 23 stream of hydrogen and carbon monoxide, which is re-24 turned to the gasifier through line 36. Conventional gas processing equipment can be used. Since a detailed 26 description of this downstream gas processing portion of 27 the process is not necessary for an understanding of the 28 invention, it has been omitted.
The fluidized bed in gasifier 32 is comprised of char particles formed as the solid carbonaceous feed ~1954Z
1 material undergoes gasification. The composition of the 2 char particles will depend upon the amount of mineral 3 matter present in the carbonaceous material fed to the 4 gasifier, the amount of the alkali metal compound or mix-ture of such compounds impregnated onto the feed material, 6 and the degree of gasification that the char particles 7 undergo while in the fluidized bed. The lighter char 8 particles, which will have a relatively high content of ... . .
9 carbonaceous material, will tend to remain in the upper portion of the fluidized bed. The heavier char particles, 11 which will contain a relatively small amount of carbona-12 ceous material and a relatively large amount of ash and alkali metal residues will tend to migrate toward the 14 bottom of the fluidized bed. A portion of the heavier ~ char particles are normally withdrawn from the bottom 16 portion of the fluidized bed in order to eliminate ash 17 and thereby prevent it from buildling up within the gasi-18 fier and other vessels in the system.
19 Since the cost of the alkali metal constituents comprising the gasification catalyst is a significant fac-21 tor in determining the overall cost of the gasification 22 process, it is particularly important that these consti-23 tuents be recovered and reused. It has been proposed to 24 recover these alkali metal constituents as they are with-drawn from the gasifier with the char particles by leach-26 ing them out with water. Studies have indicated that . , .
27 these alkali metal constituents are generally present in 28 part as carbonates, sulfates, sulfides, sulfites and 29 other water soluble compounds that can be recovered by water washing. Experience has shown, however, that only ~.~1954Z :
1 a portion of the alkali metal carbonates or other alkali 2 ;~etal constituents is normally recovered and that a sub-3 stantial quantity of makeup alkali metal compounds is 4 therefore required.
The process of this invention is based in part 6 upon studies of the reactions that catalysts containing 7 alkali metal constituents undergo during coal gasifica-. . .. ~
8 tion and similar operations. Coal and other carbonaceous ,.. . , 9 solids used in such operations normally contain mineral i, . ~ 1 1~ constituents that are converted to ash during the gasi-11 fication process. Although the composition of the ash 12 varies, the principle constituents, expressed as oxides, I
13 are generally silica, alumina and ferric oxide. The J
14 alumina is usually present in the ash in the form of 1~ aluminosilicates. Studies have indicated that at least 16 a portion of the alkali metal compounds, such as potas- -17 sium carbonate, sodium carbonate and the like, that are 18 used as gasification catalyst constituents react with 19 the aluminosilicates and other ash constituents to form alkali metal residues containing water soluble alkali 21 metal compounds such as carbonates, sulfates, sulfides, 22 sulfites and the like and water insoluble, catalytically 23 inacti~e materials such as potassium aluminosilicates 24 and other alkali metal aluminosilicates.
It has been found that from about lO to about 26 5O percent by weight of the potassium carbonate or other 27 alkali metal compound employed to impregnate coal or 28 similar feed material prior to gasification will react 29 with the aluminosilicates in the ash during gasification to form water insoluble alkali metal aluminosilicates, ~19S4Z
1 which cannot normally be recovered from the ash by water 2 washing. Preliminary studies tend to indicate that when 3 potassium carbonate is utllized to impregnate the coal, 4 the major constituent of the water insoluble potassium aluminosilicates produced is a synthetic kaliophilite, which has the chemical formula KAlSiO4.
7 To improve the economics o~ the catalytic gasi-8 fication process described above and other catalytic con-..... . .
. 9 version processes where water insoluble alkali metal residues are formed, it is desirable to recover as much 11 as possible of the alkali metal constituents from the 3 12 insoluble residues and reuse them as catalyst constituents 13 in the conversion process, thereby decreasing the amount 14 f costly makeup alkali metal compounds needed. It has 1~ been found that a substantial amount of the alkali metal ~6 constituents in the water insoluble alkali metal residues 17 withdrawn with the char and ash from the gasifier of the 18 above described process or the reaction zone of other 19 conversion processes can be recovered for reuse in the conversion process by mixing the particles withdrawn 21 from the reaction zone with calcium oxide or a solid 22 calcium-containing compound that decomposes upon heating 23 to ~orm calcium oxide, and heating the resultant mixture 24 of solids to a temperature sufficiently high to cause calcium oxide to react with water insoluble alkali metal 26 aluminosilicates in the alkali metal residues to produce 27 reaction products containing water soluble alkali metal 28 aluminates and water insoluble calcium silicates. The 29 reaction products are contacted with water, which leaches the alkali metal aluminates and other water soluble alkali ~1954Z
1 metal constituents from the solids. The pH of the resul-2 tant aqueous solution containing the water soluble alkali 3 metal aluminates is sufficiently lowered to cause aluminum 4 hydroxide to precipitate, thereby forming a solution con-taining alkali metal constituents substantially free of 6 aiuminum. These alkali metal constituents are then used 7 in the conversion process as at least a portion of the 8 alkali metal constituents which comprise the alkali metal-.,, 9 containing catalyst. Preferably, such use is achieved by recycling the solution directly to the conversion process.
11 If desired, however, the alkali metal constituents may 12 first be recovered from the solution and then used in the 13 conversion process. -14 Referring again to the drawing, char particles 1~ containing carbonaceous material, ash and alkali metal 16 residues are continuously withdrawn through line 44 from 1~ the bottom of the fluidized bed in gasifier 32. The par-18 ticles flow downward through line 44 countercurrent to a 19 stream of steam or other elutriating gas introduced - 20 through line 45. Here a preliminary separation of solids 21 based on differences in size and density takes place.
22 The lighter particles having a relatively large amount of 23 carbonaceous material tend to be returned to the gasifier 24 and the heavier particles having a relatively high content of ash and alkali métal residues continue downward through 26 line 46 containing valve 55 into hopper 56. Char fines 27 recovered from the raw product gas through dip legs 4O
28 and 43, and line 57 may also be fed into the hopper.
29 Thè solid particles in hopper 56, which contain both water soluble and water insoluble alkali metal resi-- 16 - 1, ~19S4Z
1 dues, are passed into line 58 where they are mixed with a 2 calcium-containing compound introduced into line 58 from .
3 hopper 59 via line 60. The solid calcium-containing com-4 pound may be calcium oxide or any calcium compound that decomposes to form calcium oxide when subjected to rela-6 tively high temperatures~ The calcium-containing compound 7 may be inorganic or organic and may, for example, be cal-8 cium hydroxide, calcium acetate, calcium oxalate, calcium ... .
- 9 formate, calcium carbonate, dolomite and the like. The actual calcium-containing compound used will depend pri-11 marily upon its availability and cost. The amount o~ the 12 calcium-containing compound required will depend in part 13 on the amount of silicates in the particulate matter with ' 14 which it is mixed. If desired, a mixture of two or more 1-S calcium-containing compounds may be used in lieu of a 16 single compound.
- .
17 The mixture of char particles containin~ the 18 alkali metal residues and the calcium-containing compound 19 is passed through line 61 into rotary kiln or similar heating device 62 where it is subjected to temperatures 21 sufficiently high to cause the alkali metal aluminosili-22 cates in the residues to react with calcium oxide, which 23 is formed by the thermal decomposition of the calcium-24 containing compound unless that compound is calcium oxide itself. The reaction converts the water insoluble alkali .
26 metal aluminosilicates into reaction products containing 27 water insoluble calcium silicates and water soluble alkali 28 metal aluminates. The reaction products are subsequently 29 treated, as described hereafter, to recover alkali metal constituents that are recycled to the gasification ~954Z
1 process where they serve as at least a portion of the 2 ;-~;al~ali metal constituents which comprise the alkali 3 metal-containing catalyst.
4 The mixture of solids introduced into the rotary kiln will normally be subjected to a temperature 6 ranging from about 1600 F. to about 2600 F. Preferably, 7 the mixture is heated to the sintering temperature~ which 8 ~ causes the surface of the particles to soften thereby in-9 creasing the tendency of the particles to agglomerate or stick together. Sintering imparts mobility to the calcium 11 ions present and apparently enables them to easily satu-12 rate -the atomic structure of the alkali metal aluminosili-13 cates and displace alkali metal constituents and alumina 14 to form water insoluble calcium silicates. Sintering 1~ may be effectively accomplished in a countercurrent rotary 16 kiln in which the fuel is passed through the kiln in a 17 direction opposite to that in which the mixture of solids 18 is passed. In lieu of the rotary kiln any furnace or 19 similar heating device may be used as long as the required temperatures are obtainable. If desirable, the tempera-21 ture in the heating device may be raised above the sin-22 tering temperature to convert the mixture of solids into 23 a liquid mass in which the desired reactions will take 24 place more rapidly. This procedure, however, may not be advantageous since the liquid upon cooling will form a 26 glass-like solid from which it may be difficult to water 27 leach soluble alkali metal constituents.
28 An example of one reaction that is believed to 29 take place in rotary kiln 62 is set forth below. The symbol "M" is used to represent any alkali metal cation.
The actual alkali metal present will depend on the type 2 ;~;of alkali metal compound utilized as a constituent of 3 the al~ali metal-containing gasification catalyst.
4 ~AlSiO4 + 2CaO ~ MAlO2 + Ca2SiO4 As can be seen from the above equation, an alkali metal 6 aluminosilicate reacts wlth calcium oxide to produce an 7 alkali metal aluminate and dicalcium silicate. It will 8 be understood that the above equation represents only ~ one reaction that may occur in the rotary kiln. Other reactions involving more complicated aluminosilicates 11 and other insoluble constituents of the alkali metal 12 residues may also take place.
13 The sintered mixture of solids from rotary kiln 14 62 is cooled and passed through line 63 to ball mill or similar crushing device 64 where the solids are pulver-16 ized, ground, or otherwise crushed to a size suitable 17. for water leaching. It is desirable to produce rela-18 tively small particles since they will provide a high 19 surface area for more effective water leaching. The actual size is determined in part by balancing the cost 21 of crushing with the effectiveness of the water leaching.
22 Preferably, the particles will be crushed to a size 23 smaller than about 60 mesh on the U.S. Sieve Series 24 Scale.
The crushed solids are removed from ball mill 26 64 and passed through line 65 to water wash zone 66, 27 which will normally comprise a multistage countercurrent 28 extraction system in which the solids are countercur-29 rently contacted with water introduced through line 67.
The water leaches alkali metal aluminates and other ~9S4Z
il 1 water soluble alkali metal constituents from the solids, 2 ~ ; thereby producing an aqueous solution of such consti-3 tuents, which is removed from the water wash zone 4 thrpugh line 68 and will normally have a pH of about 12.0 or less. Spent solids are removed from the water 6 wash zone via line 69 and will contain, among other sub-7 stances, ash, calcium silicates and aluminum hydroxide.
8 These solids may be disposed of as land fill or further 9 processed to recover valuable components such as calcium silicates, which may subsequently be used in the manu-11 facture of cement.
12 The aqueous solution containing alkali metal 13 aluminates and other water soluble alkali metal consti-tuents removed from water wash zone 66 via line 68 is 1~ passed through line 70 to contactor or similar vessel 71.
16 Here the pH of the solution is lowered to a value in the 17 range between about lO.0 and about 4.0, preferably between 18 about 9.0 and about 5.0, by contacting it with a carbon ¦
19 dioxide-containing gas. The aqueous solution is passed downward through the contacting zone in contactor 71 21 where it comes in contact with an upflowing gas that con-22 tains carbon dioxide. The carbon dioxide-containing gas 23 is injected into the bottom of the contactor through line 24 72. As the carbon dioxide gas rises upward through the downflowing aqueous solution, the carbon dioxide in the 26 gas reacts with the alkali metal aluminates in the solu-27 tion to form alkali metal carbonates and water insoluble 28 aluminum hydroxide. If the partial pressure of carbon 29 dioxide is sufficiently high and the temperature in the contactor is low, alkali metal bicarbonates may also form.
l~l9S4~' .. . .
1 - A gas depleted in carbon dioxide is withdrawn 2 --overhead of contactor 71 through line 73 and either 3 vented to the atmosphere, further processed for the 4 recovery and reuse of carbon dioxide, or otherwise dis-posed of. Any carbon dioxide-containing gas, including 6 pure carbon dioxide and air, may be used. It is : 7 preferred, however, to utiliz~ the flue gas produced - 8 from the fuel combustion taking place in rotary kiln 62.
.... . !
9 The contacting vessel utilized does not necessarily have , .. .
to be of the type shown in the drawing but may be any - ~ 11 type of vessel that allows for fairly good contacting 12 between the carbon dioxide-containing gas and the aqueous 13 solution containing alkali metal aluminates. A tank in 14 which the carbon dioxide-containing gas is bubbled i5 through the aqueous solution may be sufficient for pur-16 poses of the invention.
17 The purpose of the above-described step of the 18 alkali metal recovery process is to lower the p~ of the 19 aqueous solution containing the alkali metal aluminates so that substantially all of the aluminum is removed 21 from the solution in the form of a water insoluble pre-22 cipitate of aluminum hydroxide, thereby leaving in solu- i 23 tion aluminum free alkali metal constituents that are 24 subsequently recovered and used as constituents of the gasification catalyst. Removal of aluminum from the 26 alkali metal constituents before their use in the gasi-27 fication catalyst is desirable to help avoid the possible 28 formation of additional alkali metal aluminosilicates in 29 the gasifier by the reaction of the aluminum with silica in the feed material and alkali metal constituents of 1~1954Z
1 the catalyst. It will be understood that for purposes 2 .;of the invention any method of lowering pH may be used.
3 For example, instead of contacting the aqueous effluent 4 from water wash zone 66 with a carbon dioxide-containing gas, the effluent may be mixed with sufficient quanti-6 ties of sulfuric acid, nitric acid or the like to lower 7 the pH to the desired value.
8 Referring again to the drawing, the effluent ..... . .
9 from contacting vessel 71, which contains alkali metal carbonates and other water soluble alkali metal consti-11 tuents, and aluminum hydroxide, is withdrawn from the 12 bottom of the vessel through line 74 and passed to rotary 13 filter or similar liquids-solids separation device 75 where the solid aluminum hydroxide is separated from the j~ aqueous solution and then passed through line 76 to 16 : rotary kiln or similar heating device 77 where it is cal-17 cined at high temperatures to produce alumina, which is 18 recovered via line 78 and may be soId as a byproduct.
19 The sale of this material may produce an additional return from the process and thus reduce the overall cost 21 of the product gas.
22 A solids-free aqueous solution containing 23 alkali metal carbonates and other water soluble alkali 24 metal compounds is removed from filter 75 through line 79 and recycled to feed preparation zone 14 via line 18 26 where the coal or similar carbonaceous feed material is 27 impregnated with the alkali metal compounds in the solu-2~ tion. If the concentration of alkali metal compounds 29 in the recycle solution is undesirably low, the solution may be concentrated by removing excess water before it ~9s~z 1 is returned to the feed preparation zone. It will be 2 understood that the exact alkali metal compound or com-3 pounds present in the recycled solution will depend on 4 the substance used to lower the pH of the aqueous efflu-.
ent from water wash zone 66. For example, if nitric acid 6 is used in lieu of a carbon dioxide-containing gas, the 7 recycled solution will contain alkali metal nitrates 8 instead of carbonates.
The embodiment of the invention shown in the . , , drawing and discussed above is one that allows for the 11 recovery of alumina as a byproduct of the alkali metal 12 recovery process. If recovery of alumina is undesirable 13 for any reason, the embodiment of the invention depicted 14 in the drawing may be simplified by eliminating water wash zone 66 and rotary kiln 81 and replacing contactor 16 71 with a series of stirred tanks through which water and the crushed solids from ball mill 64 are passed counter-:. . .
18 currently to the carbon dioxide-containing gas. The 1~ slurry effluent from the series of stirred tanks is then passed to rotary filter 75 where the solids are separated 21 from the aqueous solution, which is recycled to the feed 22 preparation zone. The solids, which will contain, among 23 other substances, ash, calcium silicates and aluminum 24 hydroxide, may be used as landfill or otherwise disposed of.
26 It will be apparent from the foregoing that the -~27 process of the invention provides an improved alkali metal 28 recovery system, which makes it possible to significantly 29 increase the amount of alkali metal constituents that are recovered from alkali metal residues produced during cata-- 2~ -11~954;~
, 1 lytic gasification and similar hi~h temperature catalytic .2 .~onversion processes. As a result, the need for costly 3 makeup alkali metal compounds is reduced, thereby lowering . 4 the overall cost of the conversion process.
. .
.,'` ,, `, ' , .
.:.' - ' , ' ' . ,.' . :
`'" .` . " ' . .
~''".,, ' ' . ' ' '' , ..', ' ~', .
.
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Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the conversion of a solid carbon-aceous feed material in the presence of an alkali metal-containing catalyst into liquids and/or gases wherein particles containing alkali metal residues are produced, characterized by the following steps in combination:
(a) mixing said particles containing said alkali metal residues with a solid calcium-containing compound to form a mixture of solids, said calcium-containing compound selected from the group consisting of calcium oxide and a compound that decomposes upon heating to yield calcium oxide;
(b) heating said mixture of solids to a temperature sufficiently high to convert water-insoluble alkali metal constituents in said alkali metal residues into water-soluble alkali metal constituents including alkali metal aluminates;
(c) contacting said reaction products with water thereby forming an aqueous solution containing water-soluble alkali metal constituents including alkali metal aluminates;
(d) lowering the pH of said aqueous solution sufficiently to cause aluminum hydroxide to percipitate;
thereby forming an aqueous solution substantially free of aluminum; and, (e) using said alkali metal constituents from said aqueous solution formed in step (d) in said conversion process as at least a portion of the alkali metal constituents comprising said alkali metal-containing catalyst.
(a) mixing said particles containing said alkali metal residues with a solid calcium-containing compound to form a mixture of solids, said calcium-containing compound selected from the group consisting of calcium oxide and a compound that decomposes upon heating to yield calcium oxide;
(b) heating said mixture of solids to a temperature sufficiently high to convert water-insoluble alkali metal constituents in said alkali metal residues into water-soluble alkali metal constituents including alkali metal aluminates;
(c) contacting said reaction products with water thereby forming an aqueous solution containing water-soluble alkali metal constituents including alkali metal aluminates;
(d) lowering the pH of said aqueous solution sufficiently to cause aluminum hydroxide to percipitate;
thereby forming an aqueous solution substantially free of aluminum; and, (e) using said alkali metal constituents from said aqueous solution formed in step (d) in said conversion process as at least a portion of the alkali metal constituents comprising said alkali metal-containing catalyst.
2. A process as defined in claim 1 wherein said conversion process comprises gasification.
3. A process as defined in claim 1 wherein said conversion process comprises liquefaction.
4. A process as defined in claim 1 wherein at least a portion of said alkali metal-containing catalyst comprises potassium carbonate.
5. A process as defined in claim 1 wherein said calcium-containing compound comprises calcium hydroxide.
6. A process as defined in claim 1 wherein said calcium-containing compound comprises calcium carbonate.
7. A process as defined in claim 1 wherein said mixture of solids is heated to a temperature between about 1600°F
and about 2600°F.
and about 2600°F.
8. A process as defined in claim 1 including the additional step of converting said reaction products into solid particles of a predetermined size before contacting said reaction products with water.
9. A process as defined in claim 1 wherein said carbonaceous feed material comprises coal.
10. A process as defined in claim 1 wherein said aqueous solution formed in step (d) is recycled to said conversion process where said alkali metal constituents substantially free of aluminum are used as at least a portion of said alkali metal constituents comprising said alkali metal-containing catalyst.
11. A process as defined in claim 1 wherein the pH of said aqueous solution containing said water-soluble alkali metal aluminates is lowered by contacting said solution with a carbon dioxide-containing gas, thereby forming a water-insoluble precipitate containing aluminum hydroxide and an aqueous solution containing water-soluble alkali metal carbonates, and using said alkali metal carbonates as at least a portion of said alkali metal constituents comprising said alkali metal-containing catalyst.
12. A process for the gasification of coal in the presence of a carbon-alkali metal catalyst wherein particles containing alkali metal residues are produced, characterized by the following steps in combination:
(a) mixing said particles containing said alkali metal residues with a solid calcium-containing compound to form a mixture of solids, said calcium-containing compound selected from the group consisting of calcium oxide and a compound that decomposes upon heating to yield calcium oxide;
(b) heating said mixture of solids to a temperature in a range between about 1600°F and about 2600 F, whereby calcium oxide reacts with alkali metal aluminosilicates and other water-insoluble alkali metal constituents in said alkali metal residues to form solid reaction products containing water-soluble alkali metal constituents including alkali metal aluminates;
(c) contacting said solid reaction products with water, thereby forming an aqueous solution containing said soluble alkali metal constituents including said alkali metal aluminates;
(d) contacting said aqueous solution with a carbon dioxide-containing gas, thereby lowering the pH of said solution and forming a water-insoluble precipitate containing aluminum hydroxide and an aqueous solution containing water-soluble alkali metal carbonates; and, (e) recycling said aqueous solution containing said alkali metal carbonates to said conversion process where said alkali metal carbonates are used as at least a portion of the alkali metal-constituents comprising said carbon-alkali metal catalyst.
(a) mixing said particles containing said alkali metal residues with a solid calcium-containing compound to form a mixture of solids, said calcium-containing compound selected from the group consisting of calcium oxide and a compound that decomposes upon heating to yield calcium oxide;
(b) heating said mixture of solids to a temperature in a range between about 1600°F and about 2600 F, whereby calcium oxide reacts with alkali metal aluminosilicates and other water-insoluble alkali metal constituents in said alkali metal residues to form solid reaction products containing water-soluble alkali metal constituents including alkali metal aluminates;
(c) contacting said solid reaction products with water, thereby forming an aqueous solution containing said soluble alkali metal constituents including said alkali metal aluminates;
(d) contacting said aqueous solution with a carbon dioxide-containing gas, thereby lowering the pH of said solution and forming a water-insoluble precipitate containing aluminum hydroxide and an aqueous solution containing water-soluble alkali metal carbonates; and, (e) recycling said aqueous solution containing said alkali metal carbonates to said conversion process where said alkali metal carbonates are used as at least a portion of the alkali metal-constituents comprising said carbon-alkali metal catalyst.
13. A process as defined in claim 12 wherein said calcium-containing compound comprises calcium oxide.
14. A process as defined in claim 12 including the additional step of crushing said solid reaction products before they are contacted with water.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US76254877A | 1977-01-24 | 1977-01-24 | |
| US762,548 | 1977-01-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119542A true CA1119542A (en) | 1982-03-09 |
Family
ID=25065376
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000294728A Expired CA1119542A (en) | 1977-01-24 | 1978-01-11 | System for the recovery of alkali metal compounds for reuse in a catalytic coal conversion process |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS6039116B2 (en) |
| AU (1) | AU511653B2 (en) |
| BR (1) | BR7800385A (en) |
| CA (1) | CA1119542A (en) |
| DE (1) | DE2802825A1 (en) |
| FR (1) | FR2378085A1 (en) |
| GB (1) | GB1595612A (en) |
| ZA (1) | ZA78154B (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2083067B (en) * | 1980-09-02 | 1983-08-10 | Exxon Research Engineering Co | Recovery of alkali metal constituents from coal conversion residues |
| US4439304A (en) * | 1982-07-09 | 1984-03-27 | Conoco Inc. | Process for beneficiating high sulfur, high fluidity coal |
| JPS62149792A (en) * | 1985-12-25 | 1987-07-03 | Mitsubishi Heavy Ind Ltd | Gasifying device |
| JPS63716A (en) * | 1986-06-20 | 1988-01-05 | Matsushita Electric Works Ltd | Temperature controller for warm air blower |
| US7922782B2 (en) * | 2006-06-01 | 2011-04-12 | Greatpoint Energy, Inc. | Catalytic steam gasification process with recovery and recycle of alkali metal compounds |
| AU2008345189B2 (en) * | 2007-12-28 | 2011-09-22 | Greatpoint Energy, Inc. | Petroleum coke compositions for catalytic gasification |
| CN103952184B (en) * | 2014-05-14 | 2016-08-24 | 北京神雾环境能源科技集团股份有限公司 | Catalytic coal gasifaction prepares the method and system of shaft furnace reducing gases |
| CN104043485B (en) * | 2014-06-09 | 2016-03-23 | 新奥科技发展有限公司 | A kind of catalyst recovery and carrying method |
| CN110624581B (en) * | 2018-06-25 | 2022-04-15 | 中国石油化工股份有限公司 | Method for recovering coal gasification catalyst |
| US10464872B1 (en) | 2018-07-31 | 2019-11-05 | Greatpoint Energy, Inc. | Catalytic gasification to produce methanol |
| US10344231B1 (en) | 2018-10-26 | 2019-07-09 | Greatpoint Energy, Inc. | Hydromethanation of a carbonaceous feedstock with improved carbon utilization |
| US10435637B1 (en) | 2018-12-18 | 2019-10-08 | Greatpoint Energy, Inc. | Hydromethanation of a carbonaceous feedstock with improved carbon utilization and power generation |
| US10618818B1 (en) | 2019-03-22 | 2020-04-14 | Sure Champion Investment Limited | Catalytic gasification to produce ammonia and urea |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2141132A (en) * | 1936-06-11 | 1938-12-20 | Cowles Detergent Company | Process of treating siliceous materials |
| US3689240A (en) * | 1971-03-18 | 1972-09-05 | Exxon Research Engineering Co | Production of methane rich gases |
| US3998607A (en) * | 1975-05-12 | 1976-12-21 | Exxon Research And Engineering Company | Alkali metal catalyst recovery process |
-
1978
- 1978-01-10 ZA ZA00780154A patent/ZA78154B/en unknown
- 1978-01-11 CA CA000294728A patent/CA1119542A/en not_active Expired
- 1978-01-13 GB GB1408/78A patent/GB1595612A/en not_active Expired
- 1978-01-17 AU AU32499/78A patent/AU511653B2/en not_active Expired
- 1978-01-20 FR FR7801725A patent/FR2378085A1/en active Granted
- 1978-01-23 BR BR7800385A patent/BR7800385A/en unknown
- 1978-01-23 DE DE19782802825 patent/DE2802825A1/en not_active Ceased
- 1978-01-24 JP JP53005895A patent/JPS6039116B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1595612A (en) | 1981-08-12 |
| BR7800385A (en) | 1978-08-22 |
| JPS6039116B2 (en) | 1985-09-04 |
| DE2802825A1 (en) | 1978-07-27 |
| AU511653B2 (en) | 1980-08-28 |
| JPS5394305A (en) | 1978-08-18 |
| AU3249978A (en) | 1979-07-26 |
| FR2378085A1 (en) | 1978-08-18 |
| ZA78154B (en) | 1978-12-27 |
| FR2378085B1 (en) | 1983-11-25 |
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