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Show Environmental Assessment The project for environmental assessment of N0X control technologies has continued to evaluate all aspects of the problem associated with the application of combustion modifications for the control of N0X emissions from stationary combustion sources. The primary emphasis of this work has been .the evaluation of the environmental, economic, energy, and engineering implications of low N0X combustion modification technology in order to provide comparisons with the environmental impact of baseline (uncontrolled) operation. Testing of seven combustion sources has been carried out using EPA's IERL-RTP Level 1 and 2 procedures for sample collection and analysis. The sources selected for comprehensive testing included: a 180 MW tangential coal-fired utility boiler, a 500 MW horizontally-opposed coal-fired utility boiler, a 740 MW opposed-wall oil-fired utility boiler, two industrial stoker coal-fired watertube boilers, a blue flame oil-fired warm air furnace, and a 60 MW oil-fired gas turbine. Individual test reports are being prepared for each test site. Results for the 180 MW utility boiler showed that burners out of service and biased firing (staged combustion modification techniques) yielded N0X reductions of about 37 and 30 percent, respectively, compared to the baseline level (490 ppm @ 3% O2 dry). A summary of the data is shown in Table 3. A slight increase in boiler efficiency was observed and was attributed to lower excess air levels. Analysis of the results led to the conclusion that the flue gas stream from this series of tests dominated the environmental impact. Sulfur dioxide and N0X were the most significant gaseous species and potentially hazardous levels of arsenic, barium, beryllium, iron and sulfur were present. The solid effluents were estimated to be 1000 times less hazardous than the gaseous effluents. The N0X controls employed were generally beneficial in reducing the flue gas environmental impact since most species were either reduced or unaffected. Slight increases were observed for nitrogen-containing (e.g., NH3) and chloride species. There was negligible impact associated with the combustion modifications on the composition of the solid streams. Detailed analyses on the other units tested are in progress. However, based on overall considerations of the potential for adverse environmental impact, coal-fired boilers have the highest priority for improved control for stationary combustion sources. 3-53 53 |
