Control of diesel particulate and gaseous emissions using a single-stage tubular wet electrostatic precipitator

Long-term exposures to diesel particulate matter (DPM) emissions are linked to increasing adverse human health effects due to the potential association of DPM with carcinogenicity. Current diesel vehicular particulate emission regulations are based solely upon total mass concentration, albeit it is the submicrometer particles that are highly respirable and the most detrimental to human health.; In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESP) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NOx) from diesel exhaust emissions. The concentration of ozone (O3) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator utilizing a low sulfur diesel fuel (500 ppmw) operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low pressure impactor (ELPI) was used to quantify the DPM number concentration. The hydrocarbon (HC) compounds ( n-alkanes and 16 PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in HPLC grade dichloromethane with sonication. Gas chromatography/mass spectroscopy (GC/MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an ozone analyzer (Dasibi 1003AH) were used for quantifying the inlet and outlet concentrations of CO and NOx (NO+NO2 ), and O3 in the diesel exhaust stream, respectively.; The wESP was capable of removing ∼67% to ∼86% of mass- and number-based DPM at a 100% exhaust volumetric flowrate generated from 75- to 0-kW engine loads. At 75-kW engine load, increasing gas residence time from ∼0.1 to ∼0.4 sec led to a significant increase of DPM removal efficiency from ∼67% to >90%. The removal of n-alkanes and 16 PAHs, and CO in the wESP ranged from 31%-57%, and 5%-38%, respectively. The use of the wESP did not significantly affect NOx concentration in diesel exhaust. The O3 concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed. The particle collection model that takes into account for the effect of finite turbulent diffusivity induced by fluid flow and secondary flow (ion winds) was developed for effectively predicting the particle collection efficiency and the predicted results were compared with the experimental values.