Presented is a process for the off-line regeneration of a deactivated nitrogen oxide decomposition catalyst of a selective catalytic reduction system that is a component of a flue gas treating system. The selective catalytic reduction system is isolated to allow for removal and replacement of deactivated SCR catalyst. The removed SCR catalyst may be regenerated off-line from the flue gas treating system. The off-line regenerated SCR catalyst can be used as a replacement SCR catalyst.

A compression ignition internal combustion engine system includes an engine and an exhaust system with an upstream exhaust conduit, and an oxidation catalyst device (DOC). Systems and methods of desulfating the oxidation catalyst by the injection of a lightoff fluid to promote ignition of uncombusted fuel in the exhaust stream are disclosed.

A controller for an internal combustion engine includes processing circuitry that performs a dither control process on condition that a temperature increase request of a catalyst is made. The processing circuitry operates fuel injection valves so that during the dither control process, one or more cylinders are lean combustion cylinders in a first period and another one or more cylinders are rich combustion cylinders and so that the average value of an exhaust gas-fuel ratio is a target air-fuel ratio in a second period including the first period. The dither control process is restricted in a manner that, on condition that the rich process is performed, the degree of richening of the richest exhaust gas-fuel ratio of exhaust gas-fuel ratios in the cylinders is reduced.

An exhaust purification system includes: an NOx reduction type catalyst; an MAF sensor; an SOx purge control unit that uses an air system control having an intake air amount feedback-controlled based on a target intake air amount and an injection system control for a target injection increase amount set based on the target intake air amount, and a fuel injection amount feedback-controlled based on the target injection increase amount; an SOx purge prohibition processing unit that prohibits an SOx purge control; and a warming mode control unit that open-loop controls an air system when the SOx purge control is prohibited, controls the fuel injection amount, and maintains the exhaust gas at a temperature. The SOx purge control unit executes the injection system control by switching the target intake air amount into an actual intake air amount when starting the SOx purge control after a warming mode control is ended.

Presented is a process for the off-line regeneration of a deactivated nitrogen oxide decomposition catalyst of a selective catalytic reduction system that is a component of a flue gas treating system. The selective catalytic reduction system is isolated to allow for removal and replacement of deactivated SCR catalyst. The removed SCR catalyst may be regenerated off-line from the flue gas treating system. The off-line regenerated SCR catalyst can be used as a replacement SCR catalyst.

An apparatus for reactivating a sulfur poisoned oxidation catalyst operating in the exhaust of a lean burn, methane source (as in natural gas) fueled combustion device as in an engine. The reactivation includes desulfation of the poisoned catalyst through the use of a CO supplementation apparatus in communication with the control unit that is adapted to supplement the CO content in the exhaust reaching the catalyst, while avoiding an overall rich exhaust atmosphere at the catalyst. An example includes the added supply of hydrocarbons to one or more, preferably less than all, of the lean burn engine's combustion chambers such as by an ECU controlled extra supply of NG (e.g., CNG) to some of the combustion chambers. Also featured is a method for desulfation of an oxidation catalyst of a lean burn CNG engine by supplying excess CO to the exhaust reaching the catalyst while retaining an overall lean state, and a method of assembling an apparatus for reactivating a sulfur deactivated lean burn NG engine catalyst by assembling a CO supplementation apparatus with a control unit.

A NOx sensor control device is connected to a NOx sensor mounted in an internal combustion engine. The NOx sensor has a detection cell configured to detect a NOx concentration and having a solid electrolyte body and a pair of electrodes provided on a surface of the solid electrolyte body and a heater heating the detection cell. The NOx sensor control device has a heater control unit. The heater control unit is configured to, at a time when an operation of the internal combustion engine stops, perform a recovery control of the NOx sensor which is an electric current control of the heater for removing SOx adsorbed to the NOx sensor.

An ECU 30 calculates a target temperature of a bed temperature of a DOC 22a under PM regeneration control at each control period by the elements M1 to M9. Among these elements, the estimating section M7 estimates a passing SO.sub.3 amount at each control period by using an inflow SOx amount and a representative temperature. The estimating section M8 estimates a SO.sub.2 reduction rate, which is a ratio of reduction from SO.sub.3 to SO.sub.2 in the DOC 22a. Then, the calculating unit M9 calculates an amount of SO.sub.3 that is allowed to desorb from the DOC 22a as an allowable desorption SO.sub.3 amount at each control period, by using a constrained SO.sub.3 amount which corresponds to a constraint concerning sulfate white smoke, the passing SO.sub.3 amount, and the SO.sub.2 reduction rate.

An exhaust purification system includes: an NOx reduction type catalyst, which is provided in an exhaust system; a temperature acquisition unit, which acquires a catalyst temperature of the NOx reduction type catalyst; and a regeneration treatment unit, which executes a catalyst regeneration to recover an NOx purification capacity, wherein the regeneration treatment unit alternately executes a rich control, in which an exhaust air fuel ratio is set to a rich state to raise a temperature of the NOx reduction type catalyst to a predetermined target temperature, and a lean control, in which the exhaust air fuel ratio is set to a lean state to lower the temperature of the NOx reduction type catalyst, and sets an execution period of the lean control based on a deviation between the catalyst temperature acquired by the temperature acquisition unit during the previous rich control and the target temperature.

An exhaust purification system includes a NOx reduction catalyst which is provided on an exhaust passage of an internal combustion engine, a SOx purging control module for executing a SOx purging control for restoring the NOx reduction catalyst from sulfur poisoning by increasing a temperature of the exhaust gas to a first target temperature at which SOx are desorbed through an injection system control to increase a fuel injection amount, a prohibition module for prohibiting an execution of the SOx purging control according to an operating state of the internal combustion engine, and a temperature retention mode control module for executing a temperature retention mode control for maintaining the temperature of the exhaust gas at a second target temperature which is lower than the first target temperature by controlling the fuel injection amount during a period of time during which the SOx purging control is prohibited.