| Abstract |
This project addresses the health and safety concerns of underground mine workers with respect to diesel particulate matter (DPM) exposure. The underground mine workers have higher DPM exposures due to the enclosed environment and the many diesel equipment used underground. DPM has been designated as carcinogenic and or mutagenic by various agencies including the National Institute for Occupational Safety and Health (NIOSH), the International Agency for Research on Cancer (IARC), the World Health Organization (WHO), the California Environmental Protection Agency (EPA), the U.S. EPA, and the National Toxicology Program. Comparing with on road diesel machines, the non-road ones are much less studied due to less visibility and more varieties. Therefore, it is essential to quantify the DPM composition in terms of OC (organic carbon), EC (elemental carbon) and PAH (polycyclic aromatic hydrocarbons) compounds from diesel fuel, engine oil and DPM. In this project, a nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The development of a condensation electrostatic precipitator (CESP) is to provide more effective DPM control without causing high back pressure as would the diesel particulate filters (DPF). This research revealed strong effects from engine operation conditions and sampling methods on the organic composition and formation mechanisms of DPM, as well as the compound distribution. Lower sampler temperature results in more DPM mass and higher concentrations of organic species. Higher engine loads caused the increase in DPM emission rate, its elemental carbon fraction, and the heavier components, which were formed during combustion processes, and may present greater health risks. The OC fraction, on the other hand, is higher at lower engine load. Results showed that, SO2 concentration increases as diesel sulfur content or engine load increases, similar to that of DPM. In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESP) and its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), CO, and NOx from diesel exhaust emissions was evaluated. The DPM mass was determined by a gravimetric method and the number concentration was quantified by an electrical low pressure impactor (ELPI). The wESP was capable of removing approximately 67% to approximately 86% of mass- and number-based DPM at a 100% exhaust volumetric flowrate from 0- to 75-kW engine loads. The removal of organic compounds and CO in the wESP ranged from 31%-57%, and 5%-38%, respectively. The wESP (wet ESP) was evaluated with respect to different operational control parameters such as applied voltage, gas residence time, etc., to determine their effect on overall collection efficiency, as well as particle size dependent collection efficiency. The increase of exhaust gas residence time within the wESP from 0.1 to 0.4 s led to a substantial increase in the collection efficiency from 67% to 96%. The collection efficiency was found to increase with increases in applied voltage. |
