Nox catalyst regeneration method for nox purifying system and nox purifying system

Abstract

Provided is a method for regenerating the NOx catalyst of an NOx purifying system and an NOx purifying system enabling the suppression of discharge of NOx into the atmosphere when exhaust gas is temporarily brought into a rich condition to regenerate a catalyst to recover the NOx purifying ability of a direct reduction type NOx catalyst situated in the exhaust passage of an engine and capable of reliably recovering NOx purifying performance. In the method for regenerating the NOx catalyst in the NOx purifying system where the direct reduction type NOx catalyst to directly decompose NOx at a lean time and regenerate it at a rich time is situated in an exhaust passage, the control of a rich condition is prohibited when a temperature detected by a catalyst temperature detecting means is in a given temperature range.

Description

technical field [0001] The invention relates to a NOx catalyst regeneration method of a NOx purification system and the NOx purification system, which uses a direct reduction NOx catalyst to purify NOx (nitrogen oxides) in exhaust gas discharged from an internal combustion engine. Background technique [0002] Various researches and proposals have been made on catalyst-type exhaust gas purification devices that reduce and remove NOx from the exhaust gas of automobile internal combustion engines or stationary internal combustion engines, etc. In particular, the NOx adsorption reduction type is used for purifying exhaust gas of automobiles, etc. catalyst or three-way catalyst, etc. [0003] In an exhaust gas purifying device of an internal combustion engine in which such a NOx storage-reduction catalyst is arranged in the exhaust passage of the internal combustion engine, regeneration operation is performed, that is, when the air-fuel ratio of the inflowing exhaust gas is lean...

AI Technical Summary

Problems solved by technology

[0013] However, in this direct reduction type NOx catalyst, even if the rich mixture ratio condition control is performed, when the catalyst temperature enters a high temperature range, when the rich mixture ratio condition control is performed for the regeneration of the catalyst, the gas discharged into the atmosphere will be reversed. The amount of NOx increases, and since the catalyst cannot be regenerated, the purification performance cannot be restored, and there is a problem that the fuel cost is deteriorated

Images