Enhancement of diesel particulate matter collection in an electrostatic water-spraying scrubber

Marine diesel engines are major sources of air pollution. They emit a large amount of pollutants, including diesel particulate matter (DPM), carbon oxide (CO _x ), unburned hydrocarbons (HC), nitrogen oxide (NO _x ), sulfur oxide (SO _x ), and other products of combustion. Among these, DPM may cause respiratory and mutagenic diseases in humans, including lung and bladder cancer (see Donaldson et al. J Aerosol Sci 29:553–560, 1998). In this study, experiments were performed with an electrostatic water-spraying scrubber (EWSS) to evaluate its effectiveness for the collection of mass- and number-based DPM emissions from a marine diesel engine. The results show that the collection efficiency of the scrubber increases as the engine load increases due to an increase in the large DPM concentration and an increase in the amount of DPM collected by the charged droplets. The effect of water spraying performance on DPM collection at constant engine load was investigated experimentally. The strength of the electrical attraction between the charged water droplets and the charged DPM within the scrubber led to a significant increase in total DPM collection efficiency (up to 4–7 times). In addition, the total DPM collection efficiency was found to be directly related to the corona power, the electrical properties of water, water spraying performance and engine load. The EWSS appears to be a promising alternative method for controlling mass-based as well as number-based DPM emissions.