System and method for sulfur recapture in a chemical looping system

1. A method for recapturing sulfur in a chemical looping system, comprising the steps of:

receiving a flue gas stream containing a sulfur-containing species;

in a heat exchanger, reducing a temperature of the flue gas stream from about greater than 1700° F. to between approximately 1500° F. and 1650° F.;

introducing a calcium-based makeup material to the reduced temperature flue gas stream;

capturing the sulfur-containing species from the reduced temperature flue gas stream; and

recycling the sulfur-containing species to a reducer of the chemical looping system.

2. The method according to claim 1 , wherein:

the sulfur-containing species is sulfur dioxide.

3. The method according to claim 1 , wherein:

the flue gas stream is received from an oxidizer of the chemical looping system.

4. The method according to claim 3 , wherein:

the calcium-based makeup material is limestone.

5. The method according to claim 4 , wherein:

capturing the sulfur-containing species from the flue gas stream includes reacting the limestone with the sulfur dioxide in the flue gas stream to produce CaSO 4 ; and

wherein the CaSO 4 is recycled to the reducer.

6. The method according to claim 5 , wherein:

reducing the temperature of the flue gas stream and reacting the limestone with the sulfur dioxide takes place in a reactor.

7. The method according to claim 6 , wherein:

the reactor is a circulating fluidized bed reactor.

8. The method according to claim 6 , further comprising the step of:

mixing a portion of solids from the oxidizer with the flue gas stream to assist with sulfur recapture.

9. The method according to claim 6 , further comprising the step of:

recycling at least a portion of an output of the reactor through the heat exchanger.

10. A method for recapturing sulfur in a chemical looping system, comprising the steps of:

with a heat exchanger, receiving a flue gas stream having a temperature greater than 1700° F. from an oxidizer, the flue gas stream containing sulfur dioxide;

in the heat exchanger, reducing a temperature of the flue gas stream to produce a cooled flue gas stream having a temperature between approximately 1500° F. and 1650° F.;

with a reactor, receiving the cooled flue gas stream from the heat exchanger;

introducing limestone to the reactor;

in the reactor, reacting the makeup limestone with the sulfur dioxide to produce CaSO 4 ; and

transporting the CaSO 4 to a reducer of the chemical looping system.