FEASIBILITY OF CARBON-DIOXIDE MONITORING TO ASSESS AIR QUALITY IN MINES USING DIESEL EQUIPMENT.

摘要

Diesel-engine exhaust emissions are a major concern in underground mines. The operating mode and condition of the engine, the mine environment, and the operator's habits all influence the concentration and composition of the emissions. It is not practical to measure each exhaust pollutant in underground mines; therefore, a monitoring methodology is required. This dissertation investigates the feasibility of a monitoring methodology that uses carbon dioxide, CO{dollar}sb2{dollar}, as an indicator of mine air quality.; The methodology includes: (1) establishing pollutant to CO{dollar}sb2{dollar} ratios for in-service equipment, (2) estimating pollutant concentrations from the ratios and in-mine CO{dollar}sb2{dollar} measurements, and (3) using an air quality index to combine the pollutants into a single number, which indicates the health hazard associated with the pollutants.; For the methodology to be valid, the pollutant to CO{dollar}sb2{dollar} ratios must remain constant if engine operating conditions do not significantly change. However, due to the complex dynamics of the fuel injection system, the fuel-air combustion process, and the engine speed-load governing system, the pollutant to CO{dollar}sb2{dollar} ratios may vary during repetitive, but transient engine speed-and-load operation. These transient effects were investigated. In addition, the influence of changing engine conditions due to engine maladjustment, and a practical means to evaluate engine condition were investigated to advance the methodology.; The laboratory investigation determined that CO{dollar}sb2{dollar} is an effective indicator of engine exhaust pollutants. It was shown that the exhaust concentrations of carbon monoxide, carbon dioxide, oxides of nitrogen, hydrocarbons, and particulate matter do not significantly vary among repetitive, but transient engine speed-and-load duty cycles typical of in-service equipment. Based on an air quality index and threshold limit values, particulate matter exhibited the greatest adverse effect on air quality. Particulate mass was separated into volatile (organic soluble fraction) and nonvolatile (insoluble carbon fraction) components. Due to particulate concentrations, the engine operating conditions of overfueling and advanced injector timing had greater adverse effects on air quality than the conditions of retarded injector timing, intake air restriction, and Federal certification specifications. Finally, an exhaust smoke analysis that could be performed by mine workers to evaluate engine condition was proved ineffective.