# US 6,682,709 B2 · Method for reducing NOx from exhaust gases produced by industrial processes > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,682,709 B2 - Document ID: US6682709B2 - Status: Granted - Kind: B2 - Application number: 09/898,280 - Filed: 2001-07-02 - Published: 2002-03-07 - Granted: 2004-01-27 - Earliest claimed: 1997-10-31 - Assignees: Noxtech, Inc. - Inventors: Bruce C. Sudduth; Ralph J. Slone; Vishwesh Palekar; Madhu Ramavajala - Web page: https://patentgrep.com/patent/US6682709B2 ## CPC - B01D 53/8625: {Nitrogen oxides} - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract Gas-phase methods and systems for reducing NOx emissions and other contaminants in exhaust gases, and industrial processes using the same, are disclosed. In accordance with the present invention, hydrocarbon(s) autoignite and autothermally heat an exhaust gas from an industrial process so that NH3, HNCO or a combination thereof are effective for selectively reducing NOx autocatalytically. Preferably, the reduction of NOx is initiated/driven by the autoignition of hydrocarbon(s) in the exhaust gas. Within the temperature range of about 900-1600° F., the introduced hydrocarbon(s) autoignite spontaneously under fuel-lean conditions of about 2-18% O2 in the exhaust gas. Once ignited, the reactions proceed autocatalytically, heating the exhaust gas autothermally. Under some conditions, a blue chemiluminescence may be visible. ## Claims ### Claim 1 A method for reducing NOx in an exhaust gas in an industrial process, comprising contacting the exhaust gas with a reductant effective for NOx reduction under autocatalytic conditions at a location in the exhaust gas flowpath where the exhaust gas is autothermally heated to achieve said autocatalytic conditions using one or more hydrocarbons, wherein the reductant comprises ammonia, wherein the industrial process comprises a combustion process including the generation of steam, mechanical work, electricity or the processing of petrochemicals, and wherein the combustion process utilizes an internal combustion engine, a boiler, a furnace, a heater or an incinerator. ### Claim 2 (depends on 1) The method of claim 1, wherein a pressurized gas is used to convey or atomize the reductant and/or the hydrocarbon(s) into the exhaust gas flowpath. ### Claim 3 (depends on 2) The method of claim 2, wherein the pressurized gas is selected from the group consisting of steam, compressed air, pressurized exhaust gas, a gaseous or vaporous form of the hydrocarbon(s) and a gaseous or vaporous form of the reductant. ### Claim 4 (depends on 3) The method of claim 3, wherein the pressurized gas is a gaseous or vaporous form of the hydrocarbon(s). ### Claim 5 (depends on 3) The method of claim 3, wherein the pressurized gas is a gaseous or vaporous form of the reductant. ### Claim 6 (depends on 1) The method of claim 1, wherein the content of NOx in the exhaust gas is reduced by 80-90% in nearly stoichiometric proportion to the amount of added reductant. ### Claim 7 (depends on 1) The method of claim 1, wherein the NOx in the exhaust gas is selectively reduced by as much as about 99%. ### Claim 8 (depends on 1) The method of claim 1, wherein the NOx in the exhaust gas is reduced to a level in the range of about 10-200 ppm. ### Claim 9 (depends on 1) The method of claim 1, wherein the autothermal heat release is initiated by autoignition of hydrocarbon(s) in the exhaust gas. ### Claim 10 (depends on 1) The method of claim 1, wherein the heat release is equivalent to a uniform adiabatic increase of about 50-5000° F. in the exhaust gas temperature. ### Claim 11 (depends on 1) The method of claim 1, wherein the CO is oxidized below a residual concentration of about 500 ppm. ### Claim 12 (depends on 1) The method of claim 1, wherein the hydrocarbon(s) comprise a member selected from the group consisting of natural gas, liquefied petroleum gas, alcohols, gasoline, diesel fuel, aviation turbine fuel, oxygenated hydrocarbons, hydrocarbon amines, methane, propane, methanol and ethanol. ### Claim 13 (depends on 1) The method of claim 1, wherein the hydrocarbon(s) are introduced throughout a cross-section or around a perimeter of the exhaust gas flowpath using one or more nozzles. ### Claim 14 (depends on 1) The method of claim 1, wherein the reductant is introduced throughout a cross-section or around a perimeter of the exhaust gas flowpath using one or more nozzles. ### Claim 15 (depends on 1) The method of claim 1, further comprising the steps of measuring a final temperature at one or more locations throughout the cross-section of the exhaust gas flowpath and controlling the amount of hydrocarbon(s) in the exhaust gas to maintain the measured temperature(s) at a level in the range of about 1400-1550° F. ### Claim 16 A method for reducing NOx in an exhaust gas in an industrial process, comprising contacting the exhaust gas with a reductant effective for NOx reduction under autocatalytic conditions at a location in the exhaust gas flowpath where the exhaust gas is autothermally heated to achieve said autocatalytic conditions using one or more hydrocarbons, and wherein the reductant comprises urea, wherein the industrial process comprises a combustion process including the generation of steam, mechanical work, electricity or the processing of petrochemicals, and wherein the combustion process utilizes an internal combustion engine, a boiler, a furnace, a heater or an incinerator. ### Claim 17 (depends on 16) The method of claim 16, wherein a pressurized gas is used to convey or atomize the reductant and/or the hydrocarbon(s) in to the exhaust gas flowpath. ### Claim 18 (depends on 17) The method of claim 17, wherein the pressurized gas is selected from the group consisting of steam, compressed air, pressurized exhaust gas, a gaseous or vaporous form of the hydrocarbon(s) and a gaseous or vaporous form of the reductant. ### Claim 19 (depends on 18) The method of claim 18, wherein the pressurized gas is a gaseous or vaporous form of the hydrocarbon(s). ### Claim 20 (depends on 18) The method of claim 18, wherein the pressurized gas is a gaseous or vaporous form of the reductant. ### Claim 21 (depends on 16) The method of claim 16, wherein the content of NOx in the exhaust gas is reduced by 80-90% in nearly stoichiometric proportion to the amount of added reductant. ### Claim 22 (depends on 16) The method of claim 16, wherein the NOx in the exhaust gas is selectively reduced by as much as about 99%. ### Claim 23 (depends on 16) The method of claim 16, wherein the NOx in the exhaust gas is reduced to a level in the range of about 10-200 ppm. ### Claim 24 (depends on 16) The method of claim 16, wherein the autothermal heat release is initiated by autoignition of hydrocarbon(s) in the exhaust gas. ### Claim 25 (depends on 16) The method of claim 16, wherein the heat release is equivalent to a uniform adiabatic increase of about 50-500° F. in the exhaust gas temperature. ### Claim 26 (depends on 16) The method of claim 16, wherein the CO is oxidized below a residual concentration of about 500 ppm. ### Claim 27 (depends on 16) The method of claim 16, wherein the hydrocarbon(s) comprise a member selected from the group consisting of natural gas, liquefied petroleum gas, alcohols, gasoline, diesel fuel, aviation turbine fuel: oxygenated hydrocarbons, hydrocarbon amines, methane, propane, methanol and ethanol. ### Claim 28 (depends on 16) The method of claim 16, wherein the hydrocarbon(s) are introduced throughout a cross-section or around a perimeter of the exhaust gas flowpath using one or more nozzles. ### Claim 29 (depends on 16) The method of claim 16, wherein the reductant is introduced throughout a cross-section or around a perimeter of the exhaust gas flowpath using one or more nozzles. ### Claim 30 (depends on 16) The method of claim 16, further comprising the steps of measuring a final temperature at one or more locations throughout the cross-section of the exhaust gas flowpath and controlling the amount of hydrocarbon(s) in the exhaust gas to maintain the measured temperature(s) at a level in the range of about 1400-1550° F. ### Claim 31 A method for reducing NOx in an exhaust gas in an industrial process, comprising contacting the exhaust gas with a reductant effective for NOx reduction under autocatalytic conditions at a location in the exhaust gas flowpath where the exhaust gas is autothermally heated to achieve said autocatalytic conditions using one or more hydrocarbons, wherein the reductant comprises HNCO, wherein the industrial process comprises a combustion process including the generation of steam, mechanical work, electricity or the processing of petrochemicals, and wherein the combustion process utilizes an internal combustion engine, a boiler, a furnace, a heater or an incinerator. ### Claim 32 (depends on 31) The method of claim 31, wherein a pressurized gas is used to convey or atomize the reductant and/or the hydrocarbon(s) into the exhaust gas flowpath. ### Claim 33 (depends on 32) The method of claim 32, wherein the pressurized gas is selected from the group consisting of steam, compressed air, pressurized exhaust gas, a gaseous or vaporous form of the hydrocarbon(s) and a gaseous or vaporous form of the reductant. ### Claim 34 (depends on 33) The method of claim 33, wherein the pressurized gas is a gaseous or vaporous form of the hydrocarbon(s). ### Claim 35 (depends on 33) The method of claim 33, wherein the pressurize gas is a gaseous or vaporous form of the reductant. ### Claim 36 (depends on 31) The method of claim 31, wherein the content of NOx in the exhaust gas is reduced by 80-90% in nearly stoichiometric proportion to the amount of added reductant. ### Claim 37 (depends on 31) The method of claim 31, wherein the NOx in the exhaust gas is selectively reduced by as much as about 99%. ### Claim 38 (depends on 31) The method of claim 31, wherein the NOx in the exhaust gas is reduced to a level in the range of about 10-200 ppm. ### Claim 39 (depends on 31) The method of claim 31, wherein the autothermal heat release is initiated by autoignition of hydrocarbon(s) in the exhaust gas. ### Claim 40 (depends on 31) The method of claim 31, wherein the heat release is equivalent to a uniform adiabatic increase of about 50-500° F. in the exhaust gas temperature. ### Claim 41 (depends on 31) The method of claim 31, wherein the CO is oxidized below a residual concentration of about 500 ppm. ### Claim 42 (depends on 31) The method of claim 31, wherein the hydrocarbon(s) comprise a member selected from the group consisting of natural gas, liquefied petroleum gas, alcohols, gasoline, diesel fuel, aviation turbine fuel, oxygenated hydrocarbons, hydrocarbon amines, methane, propane, methanol and ethanol. ### Claim 43 (depends on 31) The method of claim 31, wherein the hydrocarbon(s) are introduced throughout a cross-section or around a perimeter of the exhaust gas flowpath using one or more nozzles. ### Claim 44 (depends on 31) The method of claim 31, wherein the reductant is introduced throughout a cross-section or round a perimeter of the exhaust gas flowpath using one or more nozzles. ### Claim 45 (depends on 31) The method of claim 31, further comprising the steps of measuring a final temperature at one or more locations throughout the cross-section of the exhaust gas flowpath and controlling the amount of hydrocarbon(s) in the exhaust gas to maintain the measured temperature(s) at a level in the range of about 1400-1550° F. ### Claim 46 A method for determining if a pollutant in an exhaust gas stream in an industrial process has been depleted by an autocatalytic process, comprising: introducing one or more hydrocarbon(s) into the exhaust gas stream at a first location to autothermally heat the exhaust gas in the presence of a reductant effective for reduction of NOx in the exhaust gas; measuring CO at a second location in the exhaust gas stream downstream from the first location; determining if the level of CO at the second location exceeds a predetermined level that corresponds to a final temperature of the exhaust gas sufficient for autocatalytic depletion of the pollutant, wherein the industrial process comprises a combustion process including the generation of steam, mechanical work, electricity or the processing of petrochemicals, and wherein the combustion process utilizes an internal combustion engine, a boiler, a furnace, a heater or an incinerator. ### Claim 47 (depends on 46) The method of claim 46, wherein the level of CO measured at the second location is used to determine if NH3 breakthrough has occurred. ### Claim 48 (depends on 46) The method of claim 46, further comprising increasing the amount of hydrocarbon(s) introduced at the first location if the level of CO at the second location exceeds the predetermined level. ### Claim 49 (depends on 46) The method of claim 46, wherein the pollutant is CO. ### Claim 50 (depends on 46) The method of claim 46, wherein the pollutant is NH3. ### Claim 51 (depends on 46) The method of claim 46, wherein the pollutant is NOx. ### Claim 52 A method for determining a level of NOx depletion by an autocatalytic process in an exhaust gas stream in an industrial process, comprising: contacting the exhaust gas stream with one or more hydrocarbon(s) and one or more reductant(s) effective for reduction of NOx at a first location so that the exhaust gas is autothermally heated to autocatalytically deplete NOx in the gas stream; measuring the amount of NOx at a second location in the exhaust gas stream downstream from the first location, wherein the industrial process comprises a combustion process including the generation of steam, mechanical work, electricity or the processing of petrochemicals, and wherein the combustion process utilizes an internal combustion engine, a boiler, a furnace, a heater or an incinerator. ### Claim 53 (depends on 52) The method of claim 52, further comprising increasing the amount of said reductant(s) at the first location to lower the amount of NOx at the second location. ### Claim 54 (depends on 52) The method of claim 52, further comprising decreasing the amount of said reductant(s) at the first location to raise the amount of NOx at the second location. ### Claim 55 (depends on 52) The method of claim 52, wherein the NOx is measured continuously. ### Claim 56 (depends on 52) The method of claim 52, wherein the NOx is measured periodically.