Low quality reductant and catalyst degradation detection method in selective catalytic reduction systems

摘要

A method of controlling a selective catalytic reduction (SCR) system, comprising: determining a conversion efficiency of an SCR catalyst (36); determining an amount of ammonia slip over the SCR catalyst (36) when the conversion efficiency is less than a predetermined threshold; anddetermining a pass / fail status of a reducing agent supply (42) and the SCR catalyst (36) based on the amount of ammonia slip and at least one ammonia slip threshold (TH, TH); generating a first pass / fail status for the reducing agent supply (42) based on the amount of ammonia slip and a first ammonia slip threshold (TH); wherein generating the first pass / fail status includes generating a first fail status indicating a low quality reducing agent if the amount of ammonia slip is less than the first Ammonia slip threshold (TH); generating a second pass / fail status for the SCR catalyst (36) based on the amount of ammonia slip and a second ammonia slip threshold (TH); wherein generating the second pass / fail status is generating a second Failed status, which includes a deteriorated SCR catalyst (36) indicates when the amount of ammonia slip is greater than the second ammonia slip threshold (TH), the second ammonia slip threshold (TH) being greater than the first ammonia slip threshold (TH).