Removal of diesel particulate matter (DPM) in a tubular wet electrostatic precipitator

In this study, experiments were performed with a tubular wet electrostatic precipitator (wESP) to evaluate its effectiveness for the removal of mass- and number-based DPM emissions. A nonroad diesel generator utilizing a low sulfur diesel fuel (500 ppmw) operating under varying load conditions was used as a stationary DPM emission source. The US EPA Method 5 “Sampling Method for Stationary Sources” and Method 1A “Sampling and Velocity Traverses for Stationary Sources with Small Stacks or Ducts” were adopted as reference methods for measurement of DPM mass concentration. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration in the diluted exhaust gas at each tested condition. The wESP was evaluated with respect to varying engine loads and to different operational control parameters, such as corona power and gas residence time, to determine their effect on overall removal efficiency. The results show that the removal efficiency of the wESP increased as the engine loads decreased principally due to an increase in gas residence time and a decrease in DPM concentrations. At a constant wESP voltage and engine load, the increase of gas residence time within the wESP led to a significant increase in total DPM removal efficiency. In addition, total DPM removal efficiency was found to be directly related to the corona power, with increasing removal efficiency measured for increases in corona power. The linear correlation of DPM effective migration velocity and superficial gas velocity was established and an empirical equation is given. The wESP appears to be a promising alternative method for control of mass-based as well as number-based DPM emissions.