Experimental evaluation of an ammonia-based post-combustion device for reduction of vehicular exhaust emissions

Exhaust emission from vehicles plays a vital role in urban air pollution and associated health and environmental problems. Despite the presence of strict emission norms, a considerable number of working vehicles continue to emit pollutants, sometimes even beyond permissible limits. The current paper reports the proof-of-concept experimental study on an advanced ammonia-based post-combustion emission control system where the exhaust gases are allowed to pass through a closed tank filled with liquid ammonia before being released into the atmosphere. Emission parameters were evaluated using standard Pollution Under Control (PUC) equipment for diesel and petrol cars in a five-day period, both with and without the device. Based on the experimental results, there was a substantial drop in emission levels. In case of diesel cars, average reductions of around 71 - 74% in CO, HC, and NOx emissions were observed. For petrol cars, the CO and HC emissions decreased by 40 - 62% and 64 - 74%, respectively, depending on the conditions. It was mainly attributed to the adsorption, neutralization reaction, and ammonia-induced reduction reactions occurring between gases and liquids. An initial qualitative GC-MS analysis of the spent ammonia solution was carried out to determine the properties of adsorbed compounds; however, it is considered an exploratory study. This study shows that the ammonia-based post-combustion technology can effectively serve as another emission reduction technique for in-service vehicles. This short-term and steady-state investigation clearly demonstrates the potential of this technology as a cost-effective and retrofittable measure for emission reduction from vehicles, which requires further research.