IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0750757
(2013-01-25)
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등록번호 |
US-8674153
(2014-03-18)
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발명자
/ 주소 |
- Sellars, Brian G.
- Babicki, Matthew L.
- Keefer, Bowie G.
- Ng, Edson
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
0 인용 특허 :
67 |
초록
▼
A method for converting lignocellulosic biomass to a useful fuel is disclosed in a process sequence resulting in low levels of depositable tars in an output gas stream. One disclosed embodiment comprises performing a sequence of steps at elevated pressure and elevated hydrogen partial pressure, incl
A method for converting lignocellulosic biomass to a useful fuel is disclosed in a process sequence resulting in low levels of depositable tars in an output gas stream. One disclosed embodiment comprises performing a sequence of steps at elevated pressure and elevated hydrogen partial pressure, including fast (or flash) hydropyrolysis of a lignocellulosic biomass feed followed sequentially with catalytically enhanced reactions for the formation of methane operating at moderate temperatures of from about 400° C. to about 650° C. under moderately elevated pressure (about 5 atm to about 50 atm). A temperature rise in the catalyst above pyrolysis temperature is achieved without the addition of air or oxygen. Gas residence time at elevated temperature downstream of methane formation zones extends beyond the time required for methane formation. This sequence results in low tar deposit levels. The catalyst promotes preferential formation of methane and non-deposit forming hydrocarbons, and coke re-gasification.
대표청구항
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1. A method for converting biomass to methane and light hydrocarbons with low levels of depositable tars, comprising: a) performing a fast pyrolysis of lignocellulosic biomass by a process selected from flash pyrolysis, fast pyrolysis or rapid pyrolysis using a hydrogen-containing sweep gas at a tem
1. A method for converting biomass to methane and light hydrocarbons with low levels of depositable tars, comprising: a) performing a fast pyrolysis of lignocellulosic biomass by a process selected from flash pyrolysis, fast pyrolysis or rapid pyrolysis using a hydrogen-containing sweep gas at a temperature of between about 400° C. and about 600° C. and at an elevated pressure of about 3 atm to about 50 atm to produce a hot pyrolysis gas mixture and a by-product containing char and ash;b) passing the hot pyrolysis gas mixture containing hydrogen through a first section of a catalytic reactor to form a methane, steam and light hydrocarbon enriched gas stream at a temperature above step a) and less than about 650° C. without the addition of air or oxygen to induce the temperature rise;c) providing an extended gas residence time of from about 10 seconds to about 10 hours within a second section of the catalytic reactor and at temperatures above the temperature of step a) and below about 650° C.; andd) cooling and separating the gas stream to output a useful methane-rich fuel gas plus by-product condensed light hydrocarbons and light oxygenates. 2. The method of claim 1 where excess hydrogen gas is maintained in the catalytic conversion reactor, and where any hydrogen is recovered and recycled back to the process. 3. The method of claim 1 where thermal pyrolysis of biomass is performed using flowing hydrogen gas as a sweep gas, and wherein the hydrogen sweep gas is impure and contains significant fractions of hydrogen, steam, methane, carbon oxides or other non-oxygen gas. 4. The method of claim 1 where hydrogen is input in steps a) and b) separately. 5. The method of claim 1 where the thermal pyrolysis is induced by contacting pre-heated solid particles with biomass particles in an oxygen deficient atmosphere. 6. The method of claim 1 where thermal pyrolysis is performed using fluidized bed, bubbling fluidized bed or circulating fluidized bed pyrolysis processes. 7. The method of claim 1 where thermal pyrolysis is performed using ablative or rotating cone processes. 8. The method of claim 1 where pyrolysis vapor production is enhanced by using finely divided catalytic materials mixed with the input biomass feed. 9. The method of claim 8 where the pyrolysis vapor production is enhanced by catalytic or catalyst coated media within the pyrolysis reactor. 10. The method of claim 1 where one or more non-catalytic process steps are performed between steps a) and b) for the chemical removal of impurities in the hot pyrolysis gas mixture, or where one or more non-catalytic process steps are performed between steps a) and b) for the physical removal of impurities such as char and ash entrained in the hot pyrolysis gas mixture. 11. The method of claim 1 comprising: using a catalyst comprising nickel on an alumina support;using catalysts comprising supported catalysts incorporating metals, metal oxides or metal sulfides having enhanced methane forming activity and a support active for the cracking of oxygenated hydrocarbons, where the metal is selected from Ni, Pt, Rh, Ru, Pd, La, Co, Mo, Cr, Fe, W or mixtures thereof; orusing a catalyst promoted with alkali or alkali earth oxides, ceria, zirconia, hafnia or mixtures thereof with enhanced activity for coke gasification by steam. 12. The method of claim 1 where cooling is used after step b) to maintain reaction temperatures below about 650° C. 13. The method of claim 1 where steps b) and c) are performed with an H/C ratio of from greater than about 4 to about 5.5 to reduce coke formation. 14. The method of claim 1 where steps b) and c) are performed with an O/C ratio of less than about 2.5. 15. The method of claim 1 where steps b) and c) are performed in a single reactor or are performed in separate reactors. 16. The method of claim 1 where catalyst is circulated from reactor sections or a reactor performing step c) to reactor sections or a reactor performing step b). 17. The method of claim 1 where step b) is performed in a circulating fluidized bed or riser reactor. 18. The method of claim 1 where an additional catalyst bed is employed after step c) to perform additional hydrodeoxygenation of residual oxygenated aromatic or oxygenated hydrocarbon compounds remaining in the gas stream after step d), or where an additional catalyst bed is employed after step c) to perform partial steam reforming of the methane product with subsequent shift reaction to create hydrogen for recycle back to the process after product separation. 19. The method of claim 1 where hydrogen is input to step a) and/or step b) which includes hydrogen that is: recycled from subsequent stages of the process such as gas separation;generated by the steam reforming of hydrocarbon gas produced;generated by the steam reforming of waste gases from gas separation processes;generated by the gasification of char from pyrolysis;generated by steam reforming using heat from the combustion of char;generated by steam reforming using heat from the combustion of waste gases from gas separation processes;generated by steam reforming or gasification using water recovered from the methane forming reaction;is produced externally to the process; orany combination of the above. 20. A method of reducing tars in vapors produced by pyrolysis of biomass, comprising: adding hydrogen to a pyrolysis gas stream comprising biomass pyrolysis vapors, to provide an H/C ratio of at least 4;passing the pyrolysis gas stream comprising hydrogen through a first section of a catalytic reactor comprising a first catalyst, thereby methanating the pyrolysis vapors; andproviding an extended gas residence time of at least 5 seconds within a second section of the catalytic reactor comprising a second catalyst. 21. The method of claim 20, where the first and second catalysts are different or where the first and second catalysts are the same. 22. The method of claim 20, further comprising passing the pyrolysis gas stream comprising hydrogen through a third section of the catalytic reactor comprising a third catalyst. 23. The method of claim 20, further comprising adding additional hydrogen to the catalytic reactor. 24. The method of claim 20, further comprising cooling the gas stream output from the catalytic reactor in a stepwise fashion. 25. The method of claim 20, wherein the second section of the catalytic reactor is at a temperature of from about 450° C. to about 550° C. 26. The method of claim 20, wherein the pyrolysis vapors are produced by pyrolysis of bio oil. 27. The method of claim 20, further comprising exposing the biomass to a catalyst. 28. The method of claim 20, wherein one or more non-catalytic process steps to remove chemical and/or physical impurities from the pyrolysis gas stream are performed prior to methanating. 29. The method of claim 20, wherein the H/C ratio is from about 5 to about 6. 30. The method of claim 20, wherein the extended gas residence time in the second section of the catalytic reactor is from about 30 seconds to about 2 minutes. 31. The method of claim 20, wherein after adding the hydrogen the pyrolysis gas stream has an O/C ratio from about 1.5 to about 2. 32. The method of claim 20, further comprising regenerating the first catalyst and/or the second catalyst. 33. The method of claim 20, where the first catalyst and the second catalyst are in the same reactor or where the first catalyst and the second catalyst are in separate reactors. 34. The method of claim 20, wherein the H/C ratio is greater than about 5, the O/C ratio is less than about 2, and the temperature of the pyrolysis gas stream passing through the catalytic reactor is less than about 650° C.
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