Particulate Matter and NOx Reduction Techniques for Internal Combustion Engine: A Review

Abstract

Exhaust emission from vehicles contains toxic gases, such as carbon monoxide due to incomplete combustion; hydrocarbons from unburnt fuel; oxides of nitrogen due to higher temperatures in the combustion chamber; oxides of sulfur and particulate matter (mostly soot). These toxic pollutants are responsible for air pollution which further becomes the cause of respiratory diseases in living beings. To curb this problem of air pollution from vehicles, India is preparing to enforce Bharat Stage-VI norms by the year 2020. This policy to leapfrog to BSVI from BSIV, eliminating BS V emission standard, has inspired/challenged inventors to find new ways and means for reducing the levels of pollution drastically. In this paper, technology involved in reducing tailpipe emission mainly particulate matter (PM) and nitrogen oxides (NOx) are discussed. The reviewed NOx reduction techniques involve fuel blending, modified engine design/combustion process and after-treatment of exhaust gases, while for PM reduction, Catalytic convertor techniques PM traps/filters technique, PM centrifugal separators technique are analyzed. It is found through this review that for NOx reduction, SNCR—selective non-catalytic reduction technique is very useful, without any use of a catalyst as remarkable results have been obtained through treating exhaust gases with Urea. Diesel particulate filter (DPF) is the technique used at the commercial level wherein centrifugal particulate separator technique is under development stage.