Method and system of controlling sulfur oxides in flue gas from coal or oil-fired boilers
A method of removing SO 3 from a flue gas of a boiler. The method includes the following steps: injecting chloride salts into a stream of the flue gas at a position located downstream of an air pre-heater—the position is selected so that the flue gas has a temperature at the position of substantially between 100° C. and 400° C.; reacting chloride salts with the SO 3 to form a sulfate-containing reaction product; and collecting the sulfate-containing reaction product in a particulate collector downstream of the boiler. A purge stream from a wet flue gas desulfurization system may be used as a source of the chloride salts. Additional chlorides may be added to the purge stream as necessary.
1. A method of removing SO3 from a flue gas of a boiler, comprising:
injecting dry chloride salts into a stream of the flue gas at a position in a duct, said position being selected so that the flue gas has a temperature at said position of as low as about 100° C. or as high as about 400° C.;
reacting dry chloride salts with the SO3 to form a sulfate-containing reaction product; and
collecting said sulfate-containing reaction product in a particulate collector downstream of the boiler.
2. A method according to claim 1 , wherein said position is located either upstream or downstream of an air pre-heater.
3. A method according to claim 1 , wherein said dry chloride salts are one of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, and a combination thereof.
4. A method according to claim 1 , wherein the boiler is a coal or oil fired boiler.
5. A method according to claim 1 , wherein said particulate collector is a bag house.
6. A method according to claim 1 , wherein said dry chloride salts are obtained from a purge stream from a wet flue gas desulfurization system.
7. A method according to claim 6 , further comprising:
processing said purge stream to increase its chloride content.
8. A method of removing SO3 from a flue gas of a boiler, comprising:
providing a purge stream from a wet flue gas desulfurization system, said purge stream containing a solution of chloride salts;
injecting dry solid chloride salts obtained from said solution of chloride salts into a stream of the flue gas at a position located downstream of an air pre-heater, said position being selected so that the flue gas has a temperature at said position of as low as about 100° C. or as high as about 400° C.;
reacting said dry solid chloride salts with the SO3 to form a sulfate-containing reaction product; and
collecting said sulfate-containing reaction product in a particulate collector downstream of the boiler.
9. A method according to claim 8 , wherein said dry solid chloride salts are one of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, and a combination thereof.
10. A method according to claim 8 , wherein the boiler is a coal or oil fired boiler.
11. A system for removing SO3 from a flue gas of a boiler, comprising:
a supply of dry solid chloride salts;
a nozzle for injecting said dry solid chloride salts into a stream of the flue gas at a position in a duct, said position being selected so that the flue gas has a temperature at said position of as low as about 100° C. or as high as about 400° C.;
means for reacting said dry solid chloride salts with the SO3 to form a sulfate-containing reaction product; and
a particulate collector for collecting said sulfate-containing reaction product downstream of the boiler.
12. A system according to claim 11 , wherein said position is located either upstream or downstream of an air pre-heater.
13. A system according to claim 11 , wherein said dry solid chloride salts are one of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, and a combination thereof.
14. A system according to claim 11 , wherein said dry solid chloride salts are obtained from a purge stream from a wet flue gas desulfurization system.