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A system and a method for controlling NOX emissions from a boiler that combusts carbonaceous fuels. The method includes the steps of (a) introducing carbonaceous fuel and combustion air into a furnace of the boiler for combusting the carbonaceous fuel in oxidizing conditions and producing flue gas i

A system and a method for controlling NOX emissions from a boiler that combusts carbonaceous fuels. The method includes the steps of (a) introducing carbonaceous fuel and combustion air into a furnace of the boiler for combusting the carbonaceous fuel in oxidizing conditions and producing flue gas including NOX and CO, and (b) leading flue gas from the furnace to a catalyst section in a flue gas channel for converting, free from introducing an external agent for NOX reduction, NOX to N2 and CO to CO2 by using CO as the reductant of NOX on a catalyst in the catalyst section.

대표청구항 ▼

1. A method for controlling NOX emissions from a boiler that combusts carbonaceous fuels, the method comprising the steps of:(a) introducing carbonaceous fuel and combustion air into a furnace of the boiler for combusting the carbonaceous fuel in oxidizing conditions and producing flue gas that incl

1. A method for controlling NOX emissions from a boiler that combusts carbonaceous fuels, the method comprising the steps of:(a) introducing carbonaceous fuel and combustion air into a furnace of the boiler for combusting the carbonaceous fuel in oxidizing conditions and producing flue gas that includes NOX and CO, and adjusting the operating conditions in the furnace so as to decrease the molar concentration of NOX and to increase the molar concentration of CO at the furnace exit such that the molar concentration of CO at the furnace exit is at least 70% the molar concentration of NOX; and(b) leading flue gas from the furnace to a catalyst section in a flue gas channel for converting NOX to N2 and CO to CO2 by using CO as the reductant of NOX on a catalyst in the catalyst section,wherein no external reagent is introduced into the flue gas channel.2. A method according to claim 1, wherein the ratio of the molar concentrations of CO and NOX at the furnace is exit is above 0.7.3. A method according to claim 1, wherein the ratio of the molar concentrations of CO and NOX at the furnace exit is from about 1 to about 3.4. A method according to claim 1, further comprising controlling the operating conditions in the furnace by adjusting the amount of combustion air introduced into the furnace.5. A method according to claim 4, wherein the amount of combustion air introduced into the furnace is controlled so that the furnace excess air is from about 10% to about 20%.6. A method according to claim 5, wherein the furnace excess air is from about 13% to about 20%.7. A method according to claim 4, wherein the furnace excess air is below 10%.8. A method according to claim 7, wherein the fuel is liquid or gaseous fuel, and the furnace excess air is is below 5%.9. A method according to claim 8, wherein the fuel is fuel oil or natural gas.10. A method according to claim 1, further comprising controlling the molar concentration of CO at the furnace exit to a level at which it reduces on the catalyst most of the NOX generated during the combustion.11. A method according to claim 1, wherein the furnace parameters are adjusted so that in normal operating conditions of the furnace the molar concentration of CO at the furnace exit is at least 70% of the molar concentration of NOX.12. A method according to claim 1, wherein the active materials of the catalyst are selected from a group consisting of platinum, palladium, rhodium, and oxides of base transition metals, and mixtures thereof.