A system for vaporizing and optionally decomposing a reagent, such as aqueous ammonia or urea, which is useful for NOx reduction, includes a cyclonic decomposition duct, wherein the duct at its inlet end is connected to an air inlet port and a reagent injection lance. The air inlet port is in a tangential orientation to the central axis of the duct. The system further includes a metering valve for controlling the reagent injection rate. A method for vaporizing and optionally decomposing a reagent includes providing a cyclonic decomposition duct which is connected to an air inlet port and an injection lance, introducing hot gas through the air inlet port in a tangential orientation to the central axis of the duct, injecting the reagent axially through the injection lance into the duct; and adjusting the reagent injection rate through a metering valve.

Apparatuses, systems, and methods are disclosed for emissions control. An emissions monitor module measures at least one pollutant level for an exhaust gas flow produced by a combustion source and treated by a pollution control device. The at least one pollutant level may be controllable based on at least one combustion source operating parameter and at least one pollution control device operating parameter. A control module controls the at least one combustion source operating parameter and the at least one pollution control device operating parameter based on the at least one measured pollutant level.

There is provided: a NOx occlusion reduction-type catalyst that is provided in an exhaust passage of an internal combustion engine, occludes NOx in exhaust when the exhaust is in a lean state, and reduces and purifies the occluded NOx when the exhaust is in a rich state; an exhaust injector that is provided in the exhaust passage and is positioned further upstream than the NOx occlusion reduction-type catalyst; a NOx-purging control unit that performs NOx purging of reducing and purifying the NOx occluded in the NOx occlusion reduction-type catalyst by lowering the exhaust to a prescribed target lambda by fuel injection by the exhaust injector; and a NOx-purging-prohibition processing unit that inhibits performance of the NOx purging in a case where the exhaust cannot be lowered to the target lambda even if the fuel injection is performed at a maximum limit injection amount of the exhaust injector.

A metallic honeycomb body with channels through which a gas may flow, made up of layers of at least partially structured sheet metal, the layers of sheet metal having at least in subregions at least two different structures, of which the first structure, with a greater structure height (H), determines the size of the channels and the second structure has a much smaller structure height (h) between troughs and peaks and the form and/or the structure height (H) of the second structure being chosen such that a ceramic coating applied later may fill the troughs of the second structure on average to at least 10%, in particular at least 50%, of their structure height (h). With the honeycomb body according to the invention, more coating material per unit of volume is durably attached in a metallic honeycomb body without excessively increasing the pressure loss. This is of advantage particularly for applications for reducing nitrogen oxides (NOx) in diesel exhaust gases.

Methods and systems are provided for an exhaust gas arrangement. In one example, a system includes a lean-NO.sub.x trap arranged upstream of a selective-catalytic reduction device with an air supply device positioned to inject air therebetween, wherein the air supply device is activated in response to an exhaust gas being rich and an exhaust gas temperature exceeding a limit temperature.

A honeycomb structure body has an outer skin, cells arranged in an inside of the outer skin, and partition walls having pores. The partition walls are arranged in the inside of the outer skin. Each of the cells is surrounded by the partition walls. The pores have communicating pores which communicate with each other adjacent cells. Exhaust gas emitted from an engine passes adjacent cells through the communicating pores. The number of the communicating pores is at a density of not less than 18000 [pores/0.25 mm.sup.2] before a catalyst is supported in the pores. An exhaust gas purification filter having the honeycomb structure body with the catalyst is arranged in an exhaust gas pipe to purify exhaust gas containing PM emitted from an engine.

An exhaust gas treatment system for an internal combustion engine includes an exhaust gas pathway that receives exhaust gas from the engine, a temperature sensor configured to generate a temperature signal associated with a temperature of the exhaust gas at a position along the exhaust gas pathway, and a reductant source. The system also includes first and second injectors in fluid communication with the reductant source. The first and second injectors are configured to inject reductant into the exhaust gas pathway at first and second rates. The system also includes a first treatment element positioned downstream of the first injector and within the exhaust gas pathway, and a controller in communication with the temperature sensor. The controller is configured to receive the temperature signal from the temperature sensor and adjust at least one of the first rate or the second rate based at least in part on the temperature signal.

A reactor for reducing the concentration of NO.sub.x in a stream comprising: an inlet for the stream; an outlet for a stream containing a reduced concentration of NO.sub.x; one or more catalyst beds comprising a ceramic or metallic foam with a NO.sub.x reduction catalyst; one or more flow paths from the inlet to the outlet that passes through at least one catalyst bed wherein the catalyst beds are closed at the top and bottom so that the flow path through the catalyst bed passes through the sides of the catalyst bed in a lateral flow is described.

An after-treatment system includes a selective catalyst reduction on filter (SCRF) device in communication with exhaust gases from an engine yielding treated exhaust gases. A nitrogen oxides (NOx) sensor is configured to measure the treated exhaust gases and has an output signal that is NOx and ammonia (NH.sub.3) cross-sensitive. A NOx sensor model is coupled to receive the output signal and mass flow data for the treated exhaust gases and provides a NOx model signal to an electronic control unit (ECU) that is operatively associated with the after-treatment system and the engine. The NOx model signal represents an exhaust gas NOx concentration estimate based upon an actual NOx concentration and an actual NH.sub.3 concentration of the exhaust gas. The ECU is operable upon the NOx concentration estimate to control the after-treatment system and the engine to effect an overall reduction in actual NOx concentration of the treated exhaust gases.

An exhaust gas purification system for a construction machine prevents deterioration of an aqueous urea solution remaining in a conduit of an aqueous urea solution replenishing circuit after replenishment. An aqueous urea solution return circuit returns, to an aqueous urea solution tank, an excessive aqueous urea solution that has not been injected from an aqueous urea solution injection device into the exhaust gas, and is provided with a first return conduit that connects the aqueous urea solution injection device to the aqueous urea solution tank and a second return conduit that connects the aqueous urea solution injection device to a conduit of an aqueous urea solution replenishing circuit. An injection valve opening pressure of a first check valve provided in the first return conduit is set higher than an injection valve opening pressure of a second check valve provided in the second return conduit.