An exhaust treatment system includes a dust-removal system. The dust-removal system has an electric field device (1021) and an exhaust cooling device. The electric field device (1021) includes an inlet of the electric field device, an outlet of the electric field device, a dust-removal electric field cathode (10212), and a dust-removal electric field anode (10211), the dust-removal electric field cathode (10212) and the dust-removal electric field anode (10211) being used for generating an ionization dust-removal electric field. The exhaust cooling device is used for reducing an exhaust temperature before the inlet of the electric field device. An exhaust dust-removal system facilitates to reduce greenhouse gas emission, and also facilitates to reduce hazardous gas and pollutant emission, so that gas emission is more environment-friendly.

A method of calculating a nitrogen oxide (NOx) mass adsorbed in a lean NOx trap (LNT) of an exhaust purification device includes calculating a NOx mass flow stored in the LNT, calculating a NOx mass flow thermally released from the LNT, calculating a NOx mass flow released from the LNT at the rich air/fuel ratio, calculating a NOx mass flow chemically reacting with the reductant at the LNT, and integrating a value obtained by subtracting the NOx mass flow thermally released from the LNT, the NOx mass flow released from the LNT at the rich air/fuel ratio, and the NOx mass flow chemically reacting with the reductant at the LNT from the NOx mass flow stored in the LNT.

Provided is a CO.sub.2 recovery device of an internal combustion engine capable of efficiently recovering CO.sub.2 emitted from an internal combustion engine or CO.sub.2 in the air, and of efficiently synthesizing methane using CO.sub.2. A CO.sub.2 recovery device of an internal combustion engine includes a CO.sub.2 capturing material disposed at a through channel of gas including CO.sub.2 to capture CO.sub.2 in the gas, and methanation catalyst to let CO.sub.2 desorbed from the CO.sub.2 capturing material react with H.sub.2 obtained from a H.sub.2 supply source to generate methane. The CO.sub.2 recovery device has a function to raise temperature of the CO.sub.2 capturing material using heat generated from the internal combustion engine to desorb CO.sub.2.

During execution of a first purification process of fluctuating a hydrocarbon concentration in exhaust gas flowing into a first catalyst with an amplitude within a prescribed range at a time interval within a prescribed range, when a switch request to a second purification process of purifying NOx in a second catalyst by adding urea water into the exhaust gas is generated, the switch to the second purification process is prohibited on the condition that a current NOx purification rate (a first purification rate R1) is higher than a purification rate (a second purification rate R2) on the assumption that the second purification process is executed, and an HC poisoning recovery stand-by process of reducing an additive amount of hydrocarbon per once in the first purification process is executed so as to reduce a slip amount of hydrocarbon into the downstream of the first catalyst.

In an internal combustion engine of the present invention, an exhaust purification catalyst (13) and a hydrocarbon supply valve (15) are disposed in an engine exhaust path, and NO.sub.x contained in exhaust gas is purified by injecting hydrocarbon from the hydrocarbon supply valve (15) at a predetermined cycle. With respect to the injection amount per unit time of the hydrocarbon from the hydrocarbon supply valve (15), there is a difference provided between the first half and the second half of one injection time period, and in the first-half injection time period (Y), the injection amount per unit time of hydrocarbon is made to be less as compared to the second-half injection time period (X).

In the case of a method for operating an exhaust gas aftertreatment system of a motor vehicle, the exhaust gas aftertreatment system comprises at least one NOx storage catalyst (10) and at least one SCR catalyst (30). According to the invention, when an inadequate function of the NOx storage catalyst (10) or of the SCR catalyst (30) is identified, at least one auxiliary measure is initiated which leads to a reduction of the NOx emissions of the motor vehicle.

In a failure diagnosis apparatus that carries out standard diagnosis processing in which a failure of the particulate filter is diagnosed by making a comparison between an output value of the PM sensor at the time when a predetermined period of time has passed from a point in time at which sensor regeneration processing for removing the particulate matter deposited on an insulation layer of the PM sensor has ended, and a predetermined threshold value, the standard diagnosis processing is carried out in the case where rich spike processing according to the in-cylinder rich control is not carried out during the predetermined period of time, whereas the rich spike processing according to the in-cylinder rich control is carried out during the predetermined period of time, the standard diagnosis processing is not carried out.

An exhaust-gas purification system and method are provided for an internal combustion engine having an NOx storage catalytic converter and a downstream SCR catalytic converter. The NOx storage catalytic converter can be supplied in a first operating mode with an oxidizing exhaust gas and in a second operating mode with a reducing exhaust gas. A third operating mode is provided between the first operating mode and the second operating mode, in which an exhaust gas which has a lower content of oxidizing constituents than the first operating mode and a lower content of reducing constituents than the second operating mode can be supplied to the NOx storage catalytic converter to improve NH.sub.3 production at the start of converter regeneration.

A chemical heat storage device includes a reactor disposed around an oxidizing catalyst and containing MgCl.sub.2 which chemically reacts with NH.sub.3 to generate heat, a storage connected to the reactor through a pipe to store NH.sub.3, an on-off valve disposed in the pipe, a temperature sensor detecting the temperature of the exhaust gas passing through the oxidizing catalyst, and a controller controlling the on-off valve based on the detected value of the temperature sensor. The controller controls the on-off valve such that the on-off valve unconditionally opens if the temperature of the exhaust gas is greater than a heat generating start temperature T.sub.L and is equal to or less than a heat generating end guide temperature T.sub.Q, and the on-off valve unconditionally opens if the temperature of the exhaust gas is greater than a regenerating temperature T.sub.H.

The present invention relates to the use of different regeneration strategies for nitrogen oxide storage catalysts (NOx storage catalyst, LNT or NSC), depending on the exhaust gas temperatures, to reduce in the total exhaust gas the greenhouse gas N.sub.2O (nitrous oxide) that is produced as a secondary emission during the regeneration of the storage catalyst. If the exhaust gas temperature is below 275° C.-290° C., regeneration takes place using a strategy with short pulses of around 2 seconds and λ Lambda 0.95 rich.