Study of Alkali Partitioning in a Bench-Scale, Pressurized Combustor Fired with a Coal-Water Mixture: Technical Note.

摘要

Two natural gas-fired and six coal-water mixture- (CWM) fired experiments were conducted with the bench-scale pressurized combustor (BSPC) at the Morgantown Energy Technology Center (METC). Two CWMs were prepared by AMAX from a Kentucky Hazard bituminous coal. One fuel was prepared from a physically cleaned coal and contained 2.4 percent ash on an as-fired basis. The second CWM was prepared from a coal that underwent both physical and chemical cleaning which reduced the ash content to 0.4 percent. The tests were designed to examine the partitioning of sodium and potassium between vapor and non-vapor products of combustion in the exhaust stream, and the distribution of total alkali between bottom ash and uncharacterized residual matter (including slag). Two on-line alkali monitors developed at METC were used to measure both the gaseous alkali and total alkali concentrations in the exhaust from the combustor. We found the proportion of alkali exiting the combustor in the vapor phase was small. Less than 1 percent of sodium and less than 5 percent of potassium that entered as part of the fuel left the combustor as a vapor. Most of the alkali leaving the combustor was associated with particle matter. On a per pound basis, burning the highly cleaned, low-ash CWM produced more alkali in the exhaust stream than burning the less processed, high-ash CWM. The additional cost of preparing the highly cleaned fuel yielded no benefit in terms of alkali reduction in the exhaust. The researchers recommend that investigations in the area of alkali reduction be directed toward removing the particles with which the majority of the alkali in the exhaust is associated. 15 refs., 8 figs., 13 tabs. (ERA citation 14:012554)