Heat recovery from sorbent-based CO
The present invention provides a method of increasing the efficiency of exothermic CO 2 capture processes. The method relates to withdrawing heat generated during the exothermic capture of CO 2 with various sorbents via heat exchange with a working fluid. The working fluid is provided at a temperature and pressure such that it is in the liquid state, and has a vaporization temperature in a range such that the heat arising from the reaction of the CO 2 and the sorbent causes a phase change from liquid to vapor state in whole or in part and transfers heat from to the working fluid. The resulting heated working fluid may subsequently be used to generate power.
1. A method for increasing energy efficiency of CO 2 capture from a fluid stream containing CO 2 , comprising:
contacting a CO 2 -containing fluid stream with a sorbent in an adsorber such that the CO 2 reacts with the sorbent so that at least a portion of the CO 2 is removed from the fluid stream and heat is generated;
withdrawing heat from the adsorber via heat exchange with a pressurized, liquid working fluid having a vaporization temperature in a range such that the heat in the adsorber arising from the reaction causes a phase change from liquid to vapor and transfers heat from the adsorber to the working fluid, thus forming a heated, vaporized working fluid.
2. The method of claim 1 , further comprising converting heat contained in the heated, vaporized working fluid to power.
3. The method of claim 2 , wherein said converting comprises expanding the heated, vaporized working fluid across a turbine.
4. The method of claim 2 , wherein the power produced is at least about 2% of net power production capacity of a power plant incorporating said method.
5. The method of claim 1 , further comprising one or both of cooling and pressurizing the heated working fluid such that it is converted into liquid form.
6. The method of claim 1 , wherein the working fluid comprises propane.
7. The method of claim 1 , wherein the working fluid is liquefied petroleum gas.
8. The method of claim 1 , wherein the vaporization temperature of the pressurized working fluid is from about 100° F. to about 180° F. at a pressure of from about 100 psia to about 500 psia.
9. The method of claim 1 , wherein the sorbent comprises a sodium carbonate-based sorbent.
10. The method of claim 1 , wherein the sorbent comprises an amine-enriched solid sorbent.
11. The method of claim 1 , wherein the working fluid is pressurized to a pressure of about 100 psia to about 500 psia.
12. The method of claim 1 , further comprising regenerating the sorbent.
13. The method of claim 12 , wherein additional heat is recovered by the heated, vaporized working fluid by heat exchange with a heated gas stream produced by regenerating the sorbent.