Removal of polycyclic aromatic hydrocarbons emitted from diesel engine using an electrostatic precipitator and heat exchanger

Abstract

The aim of this study is to remove polycyclic aromatic hydrocarbons (PAHs) in a marine diesel emission using an electrostatic precipitator (ESP) and a heat exchanger. The experimental system consisted of a diesel engine, a heat exchanger and an ESP. Residue oil (S:0.61 %) was used as a test fuel oil. The heat exchanger can cool the exhaust gas from 130 °C to 20 °C. The ESP has a parallel plate electrode structure. The high-voltage electrode has saw-tooth edges on their upstream and downstream sides. The high-voltage electrode was supplied with negative DC high voltage to generate corona discharge. PAHs in the exhaust gas have two different states, which are particulate and gaseous matters. Their concentrations were measured using a filter, an absorbent, a soxhlet extraction and a gas chromatograph mass spectrometer (GCMS). A total of 24 kinds of PAHs were measured. As a result, it was shown that the gaseous PAHs transformed into particles due to the cooling of the exhaust gas in the heat exchanger. The removal efficiency for the particulate PAHs in the ESP reached 95 %. The removal efficiency for the gaseous PAHs increased with increasing applied voltage in the ESP, and reached 77 %. The overall efficiency for the particulate and the gaseous PAHs in the ESP with the heat exchanger reached 91 % and 69 %, respectively. It was indicated that the ESP with the heat exchanger is effective for removing any compound of PAHs in the diesel exhaust gas.