Exhaust gas purifying device and method for calculating the mass of NOx, which is reduced in the lean NOx trap in the regeneration

A method for computing the nitrogen oxide (NOx) mass (LNT) is reduced in the regeneration of a lean NOx trap containing the calculation of C3H6 mass flow used for the reduction of NO x from flowing into the LNT an exhaust gas purification device C3H6 -Massenstrom, the calculation of the NH3 mass flow used for the reduction of NOx from the resulting in the LNT NH3 mass flow, calculating the reduced NOx mass flow on the basis of C3H6 mass flow and used for reducing the NOx of NH3 used for reducing NOx -Massenstroms and the calculation of the reduced mass of NOx reduced by integrating the NOx mass flow through the regeneration period.