Reduction of gaseous pollutants in combustion flue gas

Fuel burning apparatus adapted for reducing nitrogen oxides in its exhaust gas, comprising:

• a. means defining a primary combustion zone having an inlet for combustion supporting gas and an outlet for gaseous combustion products and having means for introducing fuel therein,
• b. a secondary combustion device disposed in a secondary combustion zone through which the gaseous combustion products flow from the primary zone,
• c. a source of combustion supporting gas,
• d. first flow control means constructed and arranged to conduct said gas to said primary combustion zone,
• e. second flow control means constructed and arranged to conduct said combustion supporting gas to said secondary combustion zone by way of said device,
• f. said secondary combustion device comprising a plurality of elongated hollow means having a plurality of openings for dispersing said combustion supporting gas into the gas stream flowing through said secondary combustion zone, said hollow means being supplied with gas through said second flow control means and being comprised of a porous material selected from the class consisting of ceramic, heat resistant metals and silicon carbide, and
• g. means for sensing the level of at least one of the gaseous combustion products downstream of said secondary combustion device, said sensing means being operatively coupled to said second flow control means, said sensing means being responsive to the sensed level of said at least one gaseous combustion product for operating said second flow control means to adjust the flow of said combustion supporting gas provided to said secondary zone.

Fuel burning apparatus adapted for reducing nitrogen oxides in its exhaust gas, comprising:

• a. means defining a primary combustion zone having an inlet for combustion supporting gas and an outlet for gaseous combustion products and having means for introducing fuel therein,
• b. a secondary combustion device disposed in a secondary combustion zone through which the gaseous combustion products flow from the primary zone,
• c. a source of combustion supporting gas,
• d. first flow control means constructed and arranged to conduct said gas to said primary combustion zone,
• e. second flow control means constructed and arranged to conduct said combustion supporting gas to said secondary combustion zone by way of said device,
• f. said secondary combustion device comprising a plurality of secondary air delivery elements including a hollow element having a plurality of holes therein for dispersing secondary combustion air in said gaseous combustion product stream, said air delivery elements being coupled to said second flow control means, and cooling means defining a cooling fluid flow space in conjunction with each said air delivery elements, and
• g. means for sensing the level of at least one of the gaseous combustion products downstream of said secondary combustion device, said sensing means being operatively coupled to said second flow control means, said sensing means being responsive to the sensed level of said at least one gaseous combustion product for operating said second flow control means to adjust the flow of said combustion supporting gas provided to said secondary zone.