Waste to energy conversion without CO
The invention provides a method for energy extraction from municipal and mixed waste streams. The method employs a three-stage pyrolysis to produce a hydrogen-rich pyrolysis gas, which maximizes energy extraction without releasing carbon dioxide into the atmosphere.
1. A process for obtaining energy from waste, which comprises:
(a) drying the waste;
(b) anaerobic pyrolysis of the waste at 300° C. to 600° C. to produce syngas, char, and bio-oil;
(c) anaerobic pyrolysis of the syngas in the presence of a portion of the bio-oil, a portion of the char, additional carbon dioxide, and added water, at 600° C. to 900° C., to produce a gas with increased hydrogen content and a product oil;
(d) anaerobic pyrolysis of the gas and product oil produced at (c), in the presence of additional water and additional carbon monoxide, at 800° C. to 1200° C. and about 20 atmospheres pressure, to further increase the hydrogen content of the gas;
(e) separating hydrogen, carbon dioxide and carbon monoxide from the gas produced at (d);
(f) using the separated carbon monoxide as the additional carbon monoxide in step (d); and
(g) using the separated carbon dioxide as the additional carbon dioxide in step (c).
2. The process of claim 1 , further comprising:
(h) fuelling a steam generator by combusting the hydrogen separated at (e).
3. A process for obtaining energy from waste, comprising:
(a) drying the waste:
(b) anaerobic pyrolysis of the waste at 300° C. to 600° C. to produce syngas, char, and bio-oil:
(c) anaerobic pyrolysis of the syngas in the presence of a portion of the bio-oil, a portion of the char, additional carbon dioxide, and added water, at 600° C. to 900° C., to produce a gas with increased hydrogen content and a product oil;
(d) anaerobic pyrolysis of the gas and product oil produced at (c) in the presence of additional water and additional carbon monoxide, at 800° C. to 1200° C. and about 20 atmospheres pressure, to further increase the hydrogen content of the gas;
(e) fuelling a fuel cell with the gas produced at (d);
(f) driving a steam generator with steam produced by the fuel cell;
(g) separating carbon dioxide and carbon monoxide from the effluent gases of the fuel cell;
(h) using the carbon monoxide as the additional carbon monoxide in step (c);
(i) using a portion of the carbon dioxide as the additional carbon dioxide in step (b).
4. The process of claim 3 , wherein the fuel cell is a solid oxide fuel cell (SOFC).
5. The process of claim 4 , wherein the SOFC and steam generator are an integrated SOFC/turbine system.