Ash deposited in diesel particular filter: a review

Diesel particle filter (DPF) is widely considered as the most effective approach to reduce and control particle matter (PM) emissions. However, with the continuous accumulation of particles, DPF has poor performance and has to burn PM, i.e. regeneration. Unlike soot, ash cannot be removed from DPF through burning, which shows a negative effect on DPF performance. Therefore, the recent research progress about ash deposited in DPF has been summarized. The chemical composition and formation process were analyzed. The effects of ash on the DPF performance were addressed. The results show that the ash is mainly generated from lubricating oil, and the chemical composition of ash mainly consists of Ca, Mg, P, and S. Meanwhile, the ash morphology and color depended on the ash chemical composition. The flow-induced transport and the regeneration-reduced transport alter the mobility of the ash from the channel walls to the plug. The ash cannot influence the DPF performace in the nomal condition while it has an important effect on back pressure and soot oxidation characteristics. Furthermore, there are still disagreements on the mechanism of the ash distribution process and the effect of the distribution form of ash deposits in the DPF channel on the pressure drop. In the future, the investigations on the ash physico-chemical property and the ash formation process will be helpful to elucidate the abovementioned problems. In addition, in order to reduce the ash deposited and ensure the DPF normal operation, the more strict lubricant regulations should be implemented in China.