CATALYTIC STEAM GASIFICATION PROCESS WITH RECOVERY AND RECYCLE OF ALKALI METAL COMPOUNDS

• US 20070277437A1
• Filed: 06/01/2006
• Published: 12/06/2007
• Est. Priority Date: 06/01/2006
• Status: Active Grant

• Current Assignee: Sure Champion Investments Limited
• Original Assignee: Great Point Energy Incorporated
• Inventors: Sheth, Atul C.
• Granted Patent: US 7,922,782 B2
• Time in Patent Office: Days
• US Class Current: 48/197.R
• CPC Class Codes: C10J 2300/0903 Feed preparation
• CPC Class Codes: C10J 2300/093 Coal
• CPC Class Codes: C10J 2300/0983 Additives
• CPC Class Codes: C10J 2300/0986 Catalysts
• CPC Class Codes: C10J 2300/1631 Ash recycling
• CPC Class Codes: C10J 2300/1696 with phase separation, e.g. after condensation
• CPC Class Codes: C10J 2300/1807 Recycle loops, e.g. gas, solids, heating medium, water
• CPC Class Codes: C10J 3/00 Production of combustible gases containing carbon monoxide from solid carbonaceous fuels destructive distillation processes C10B
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

A high efficiency gasification process for converting carbonaceous solids to methane and apparatus for its practice are described. The process includes reacting steam and carbonaceous solids comprising ash in the presence of alkali metal catalyst in a gasification reactor to produce combustible gases and char particles comprising ash and alkali metal catalyst constituents, treating a stream of such char particles in an alkali metal catalyst recovery system to recover the catalyst constituents as alkali metal compounds, and recycling such recovered compounds. Within the alkali metal catalyst recovery system the process includes quenching the stream of char particles with water whereby such particles are cooled and fractured, dissolving soluble alkali metal catalyst constituents from the fractured solids to form a first alkali metal catalyst solution and washed solids, optionally reacting the washed solids in alkaline solution to form a second alkali metal catalyst solution, upgrading said first and optional second alkali solution to recover the alkali metal catalyst constituents as said alkali metal compounds.

Claims

1. A coal gasification process comprising:

contacting coal particles with steam in the presence of an alkali metal catalyst in a reactor wherein raw product gases are formed and char particles are produced, said char particles containing carbon, inorganic constituents, and alkali metal catalyst constituents,

withdrawing a stream of said raw product gases from said reactor,

recovering a product gas stream from said stream of said raw product gases,

contacting a stream of char particles from said reactor with water in a fracturing unit whereby said char particles fracture and a portion of said alkali metal catalyst constituents dissolve into said water to form a fracturing unit solution and washed solids,

withdrawing from said fracturing unit a stream of said washed solids and a stream of said fracturing unit solution.

2. The process of claim 1 wherein

said stream of washed solids is reacted with a solution of alkaline earth compounds at a temperature in the range of about 50°

C. to about 300°

C. to form a slurry of spent solids, and the process further comprises;

combining said slurry of spent solids with said stream of fracturing unit solution to form a catalyst recovery stream,

filtering and carbonating said catalyst recovery stream to recover a stream of alkali carbonate compounds, and

recycling said alkali carbonate compounds for contacting with said coal particles.

3. The process of claim 2 wherein said slurry of spent solids is not treated to multi-stage water wash prior to recycling alkali carbonate compounds recovered therefrom.

4. The process of claim 1 further comprising:

filtering and carbonating said stream of fracturing unit solution to recover a stream of alkali carbonate compounds, and

recycling said alkali carbonate compounds for contacting with said coal particles.

5. The process of claim 4 wherein said stream of fracturing unit solution is not treated to multi-stage water wash prior to recycling alkali carbonate compounds recovered therefrom.

6. The process of claim 2 or 4 wherein said alkali carbonate compounds comprise potassium carbonate or sodium carbonate.

7. The process of claim 2 wherein said solution of alkaline earth compounds comprises calcium hydroxide, and

the molar ratio of calcium hydroxide to alkali metal in the washed solids is from about 5 to about 25.

8. The process of claim 2 or 4 wherein said carbonating follows said filtering.

9. The process of claim 2 or 4 wherein said carbonating is conducted by exposing said catalyst recovery stream to a stream comprising carbon dioxide.

10. The process of claim 1 wherein said product stream comprises methane.

11. The process of claim 1 wherein said product stream comprises syngas.

12. The process of claim 1 wherein said contacting a stream of char particles from said reactor with water in a fracturing unit comprises water jets impinging upon said stream of char particles.

13. The process of claim 1 wherein said contacting a stream of char particles from said reactor with water in a fracturing unit comprises said stream of char particles falling into a pool of water.

14. The process of claim 2 or 4 wherein said alkali carbonates are recycled as an aqueous solution.

15. The process of claim 2 or 4 further comprising drying said stream of alkali carbonate compounds and recycling said alkali carbonate compounds as solids.

16. The process of claim 1 wherein said stream of water washed solids is withdrawn at a temperature in the range of about 50°

C. to about 300°

C.

17. The process of claim 16 wherein said stream of water washed solids is withdrawn at a temperature in the range of about 50°

C. to about 95°

C.

18. The process of claim 16 wherein said stream of water washed solids is withdrawn at a temperature in the range of about 125°

C. to about 300°

C.

19. A process wherein carbonaceous solids containing alumina and silica constituents are reacted in the presence of alkali metal compounds to form char particles which comprise insoluble alkali compounds and soluble alkali compounds said process comprising:

contacting a stream of said char particles with water in a fracturing unit whereby said particles fracture and a portion of said soluble alkali compounds dissolve to form washed solids and a first solution comprising said portion of soluble alkali compounds, and wherein said washed solids settle,

digesting a stream of said settled, washed solids with a solution or slurry of alkaline earth compound in aqueous phase to form a slurry of spent solids comprising alkaline earth compounds in a second solution comprising a portion of said insoluble alkali compounds,

combining said a slurry of spent solids comprising alkaline earth compounds in said second solution with said first solution to form a catalyst recovery stream,

filtering and carbonating said catalyst recovery stream to recover a stream of alkali carbonate compounds, and

recycling said alkali carbonate compounds for use in said process.