Multi-reaction process for forming a product gas from solid carbonaceous material
A direct carbonaceous material to power generation system integrates one or more solid oxide fuel cells (SOFC) into a fluidized bed gasifier. The fuel cell anode is in direct contact with bed material so that the H 2 and CO generated in the bed are oxidized to H 2 O and CO 2 to create a push-pull or source-sink reaction environment. The SOFC is exothermic and supplies heat within a reaction chamber of the gasifier where the fluidized bed conducts an endothermic reaction. The products from the anode are the reactants for the reformer and vice versa. A lower bed in the reaction chamber may comprise engineered multi-function material which may incorporate one or more catalysts and reactant adsorbent sites to facilitate excellent heat and mass transfer and fluidization dynamics in fluidized beds. The catalyst is capable of cracking tars and reforming hydrocarbons.
1. A method of producing a final product gas from shredded and dried biomass, comprising:
(a) introducing shredded and dried biomass into a first stage gasifier having a first fluidized bed, to produce a first stage product gas comprising H 2 O, H 2 , CO, CO 2 and char;
(b) after step (a), introducing at least a portion of the first stage product gas to a first cyclone to separate fine char therefrom;
(c) after step (b), introducing the fine char separated from the first stage product gas to a second stage gasifier having a second fluidized bed, to produce a second stage product gas;
(d) after step (c), introducing at least a portion of the second stage product gas to a second cyclone to separate ash therefrom;
(e) after step (d), combining the first stage product gas from which the char was separated, with the second stage product gas from which ash has been separated, to produce a final product gas;
(f) after step (e), introducing the final product gas to a heat recovery steam generator (HRSG) to produce steam;
(g) after step (f), removing particulates from the final product gas with a venturi scrubber;
(h) after step (g), cooling the final product gas to condense excess steam; and
(i) after step (h), capturing CO 2 present in the final product gas;
wherein:
step (a) comprises operating during startup, pulse combustion heaters which protrude into the first stage gasifier;
the first fluidized bed is fluidized with superheated steam, CO2 and 02, and is maintained at a temperature ranging from 600° C. to 1,000° C.; and
the second fluidized bed is fluidized with O 2 produced by a VPSA oxygen separation system.
2. The method according to claim 1 , wherein:
step (a) comprises transferring shredded and dried biomass at atmospheric pressure into the first stage gasifier operating at a pressure between 1 and 15 bar gauge.
3. The method according to claim 2 , further comprising:
maintaining the temperature of the first fluidized bed with plurality of indirect heater conduits protruding into the first fluidized bed.
4. The method according to claim 3 , wherein:
the plurality of indirect heater conduits includes pulse combustion heaters.
5. The method according to claim 4 , wherein:
the pulse combustion heaters are driven by at least a portion of the final product gas.
6. The method according to claim 4 , further comprising:
providing a plurality of fuel cell elements which protrude into the first fluidized bed within the first stage gasifier.
7. The method according to claim 3 , wherein:
the plurality of indirect heater conduits includes electrical heaters.
8. The method according to claim 1 , wherein step (a) comprises:
(a1) introducing, into a drying and devolatilization zone of the first fluidized bed, the shredded and dried biomass and converting the shredded and dried biomass into H 2 O, H 2 , CO, CO 2 and char, the char comprising carbonaceous material; and
(a2) simultaneously, endothermically reacting: (i) superheated steam with some of the carbonaceous material to produce additional H 2 and additional CO; and (ii) CO 2 with some of the carbonaceous material, to produce additional CO.
9. The method according to claim 1 , wherein:
the shredded and dried biomass has a top size of 1 inch and a moisture content of 10%.
10. The method according to claim 1 , wherein the pulse combustion heaters do not play a role in sustaining gasification during steady state operations.
11. A method of producing a final product gas from shredded and dried biomass, comprising:
(a) introducing shredded and dried biomass to a first stage gasifier having a first fluidized bed, to produce a first stage product gas comprising H 2 O, H 2 , CO, CO 2 and char;
(b) after step (a), introducing at least a portion of the first stage product gas to a first cyclone to separate fine char therefrom;
(c) after step (b), introducing the fine char separated from the first stage product gas to a second stage gasifier having a second fluidized bed, to produce a second stage product gas;
(d) after step (c), introducing at least a portion of the second stage product gas to a second cyclone to separate ash therefrom;
(e) after step (d), combining the first stage product gas from which the char was separated, with the second stage product gas from which ash has been separated, to produce a final product gas;
wherein:
step (a) comprises operating during startup, pulse combustion heaters which protrude into the first stage gasifier;
the first fluidized bed is fluidized with superheated steam, CO 2 and O 2 , and is maintained at a temperature ranging from 600° C. to 1,000° C.; and
the second fluidized bed is fluidized with O 2 .
12. The method according to claim 11 , further comprising:
maintaining the temperature of the first fluidized bed with plurality of indirect heater conduits protruding into the first fluidized bed.
13. The method according to claim 12 , wherein:
the plurality of indirect heater conduits includes pulse combustion heaters.
14. The method according to claim 13 , wherein:
the pulse combustion heaters are driven by at least a portion of the final product gas.
15. The method according to claim 13 , further comprising:
providing a plurality of fuel cell elements which protrude into the first fluidized bed within the first stage gasifier.
16. The method according to claim 12 , wherein:
the plurality of indirect heater conduits includes electrical heaters.
17. The method according to claim 11 , wherein step (a) comprises:
(a1) introducing, into a drying and devolatilization zone of the first fluidized bed, the shredded and dried biomass and converting the shredded and dried biomass into H 2 O, H 2 , CO, CO 2 and char, the char comprising carbonaceous material; and
(a2) simultaneously, endothermically reacting: (i) superheated steam with some of the carbonaceous material to produce additional H 2 and additional CO; and (ii) CO 2 with some of the carbonaceous material, to produce additional CO.
18. The method according to claim 11 , further comprising;
(g) after step (f), removing particulates from the final product gas with a venturi scrubber;
(h) after step (g), cooling the final product gas to condense excess steam; and
(i) after step (h), capturing CO 2 present in the final product gas.
19. The method according to claim 11 , wherein:
the shredded and dried biomass has a top size of 1 inch and a moisture content of 10%.
20. The method according to claim 11 , wherein:
the second fluidized bed is fluidized with O 2 produced by a VPSA oxygen separation system.
21. The method according to claim 11 , wherein the pulse combustion heaters do not play a role in sustaining gasification during steady state operations.
22. A method of producing a final product gas from shredded and dried biomass, comprising:
(a) introducing shredded and dried biomass to a first stage gasifier having a first fluidized bed, to produce a first stage product gas comprising H 2 O, H 2 , CO, CO 2 and char;
(b) after step (a), introducing at least a portion of the first stage product gas to a first cyclone to separate fine char therefrom;
(c) after step (b), introducing the fine char separated from the first stage product gas to a second stage gasifier having a second fluidized bed, to produce a second stage product gas;
(d) after step (c), introducing at least a portion of the second stage product gas to a second cyclone to separate ash therefrom; and
(e) after step (d), combining the first stage product gas from which the char was separated, with the second stage product gas from which ash has been separated, to produce a final product gas;
wherein:
the first fluidized bed is fluidized with superheated steam and CO 2 and is maintained at a temperature ranging from 600° C. to 1,000° C.;
the second fluidized bed is fluidized with O 2 ;
step (a) comprises operating during startup, pulse combustion heaters which protrude into the first stage gasifier; and
step (a) further comprises:
(a1) introducing, into a drying and devolatilization zone of the first fluidized bed, the shredded and dried biomass and converting the shredded and dried biomass into H 2 O, H 2 , CO, CO 2 and char, the char comprising carbonaceous material; and
(a2) simultaneously, endothermically reacting: (i) superheated steam with some of the carbonaceous material to produce additional H 2 and additional CO; and (ii) CO 2 with some of the carbonaceous material, to produce additional CO.
23. The method according to claim 22 , wherein the pulse combustion heaters do not play a role in sustaining gasification during steady state operations.