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LOW-SULFUR WESTERN COAL USE IN EXISTING SMALL AND INTERMEDIATE SIZE BOILERS
Citation:
Maloney, K., G. Moilanen, AND P. Langsjoen. LOW-SULFUR WESTERN COAL USE IN EXISTING SMALL AND INTERMEDIATE SIZE BOILERS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/7-78/153A.
Description:
The report gives results of testing of 10 representative coal-fired boilers in the Upper-Midwest, including an assessment of SOx, NOx, CO, unburned HC, and particulate emissions from these units, as well as an assessment of the operational impact of coal switching. The study showed that western subbituminous coals can be substituted for eastern bituminous coals as an industrial boiler fuel. Western coals are compatible with industrial coal-fired units of current design. Two unit types of older design (underfed and traveling grate stokers) experienced difficulty burning western coal. In some cases, the boiler's maximum load capacity had to be limited, a problem that can be eliminated by predrying the coal or by increasing superheat steam attemperation capacity. Western subbituminous coals were superior to eastern coals in terms of SOx, NOx, particulate, and unburned HC emissions. Western coals could be fired at lower excess air and exhibited substantially lower combustible losses than eastern coals. The size of delivered western coal was a problem in most of the stoker-fired units tested: it generally had too large a percentage of fine coal, caused by its poor weathering characteristics. Stoker performance on western coal can be improved by sizing the coal at the point of use, to reduce delivery distances to about 200 miles.