An exhaust gas purification system for an internal combustion engine includes a dual passage portion having a first passage and a second passage which are connected in parallel to each other. In the first passage, a first catalyst constructed of lean NOx catalyst is located and further a second catalyst constructed of oxidizing catalyst or three-way catalyst is located downstream of the first catalyst. In the second passage, a third catalyst constructed of oxidizing or three-way catalyst is located. A flow switching valve is provided so as to switch the flow of exhaust gas between the first passage and the second passage. The flow switching valve is switched so that exhaust gas flows through the third catalyst when the engine is being warmed-up and flows through the first catalyst and the second catalyst after the engine has been warmed-up.

Exhaust gas purification system for an internal combustion engine

A safe, reliable SCR system for reducing NOx emissions from a lean-burn internal combustion engine utilizes urea in aqueous solution. A modular assembly is provided for mounting inside an urea reagent tank (30) which enables controlled feeding of an aqueous urea solution to an injector. The assembly includes a reagent quality sensor (152), a reagent temperature sensor (143), a reagent level sensor (154) and a pump (137).

Reducing NOx emissions from an engine by temperature-controlled urea injection for selective catalytic reduction

A safe, reliable SCR system for reducing NOx emissions from an internal combustion engine hydrolyzes urea or like reagent under sufficient pressure to assure generation of ammonia, without production of solids that could foul injectors or catalysts. The heat for hydrolysis can be provided by the exhaust or an auxiliary means.

Reducing no emissions from an engine by on-demand generation of ammonia for selective catalytic reduction

A method is provided for reducing NOx in a combustion exhaust gas stream from a boiler. The method includes the steps of converting an aqueous solution of urea to ammonia by heating the urea solution to a temperature of 350°-650° F. in an injection lance system. The urea solution is pressurized to the pressure required to keep urea reaction products in the liquid phase and is contacted for a selected time with a conversion catalyst selected from the group of metals, metal oxides, or metal compounds consisting of chromium or molybdenum to provide a converted urea solution. The converted urea solution is injected from the injection lance system into the combustion exhaust gas for reducing NOx.

Method for converting urea to ammonia

The NOx content in a flow of flue gas is reduced by passing the flue gas through a first treatment zone and a second treatment zone. A nitrogeneous treatment agent is introduced into the first treatment zone for the selective non-catalytic reduction of part of the NOx, and the flue gas is thereafter passed through the second treatment zone which includes a catalyst for further selective catalytic reduction of the NOx. Optionally, a second nitrogeneous treatment agent is added to the flue gas in the second treatment zone. The quantity of NOx in the flue gas is detected intermediate the first and second treatment zones and, optionally, after the flue gas has left the second treatment zone. The quantity of ammonia in the flue gas exiting from the second treatment zone is also detected. The amounts of the treatment agents added to the flue gas are controlled responsive to the variations and absolute levels determined by these measurements.

Control of nox reduction in flue gas flows

A process for reducing nitrogen oxides in a combustion effluent is presented. The process involves introducing a nitrogenous treatment agent into the effluent under conditions effective to create a treated effluent having reduced nitrogen oxides concentration such that ammonia is present in the treated effluent; and then contacting the treated effluent under conditions effective to reduce the nitrogen oxides in the effluent with a nitrogen oxides reducing catalyst.

Combined catalytic/non-catalytic process for nitrogen oxides reduction

A process for reducing nitrogen oxides in a combusiton effluent is presented. The process involves introducing a nitrogenous treatment agent into the effluent under conditions effective to create a treated effluent having reduced nitrogen oxides concentration such that ammonia is present in the treated effluent; and then contacting the treated effluent under conditions effective to reduce the nitrogen oxides in the effluent with a nitrogen oxides reducing catalyst.

Catalytic/non-catalytic combination process for nitrogen oxides reduction

Kombiniertes sncr und scr verfahren zur reduzierung der stickstoffoxyde

not available for EP0491726Abstract of corresponding document: US4978514A process for reducing nitrogen oxides in a combustion effluent is presented. The process involves introducing a nitrogenous treatment agent into the effluent under conditions effective to create a treated effluent having reduced nitrogen oxides concentration such that ammonia is present in the treated effluent; and then contacting the treated effluent under conditions effective to reduce the nitrogen oxides in the effluent with a nitrogen oxides reducing catalyst.

Bryan K. Luftglass

Papers

Combined catalytic/non-catalytic process for nitrogen oxides reduction

Catalytic/non-catalytic combination process for nitrogen oxides reduction

Kombiniertes sncr und scr verfahren zur reduzierung der stickstoffoxyde

Combined sncr and scr process for nitrogen oxides reduction