STATUS OF COAL ASH BEHAVIOR RESEARCH

The inorganic components contained in coal are converted to ash during combustion and gasification. The resulting ash can cause significant problems that include slag flow behavior, ash deposition, bed agglomer ation, corrosion and erosion of system parts, fine particulate that is difficult to collect, and blinding of hot-gas cleanup filters. The ty pe of problem and the degree of the problem are dependent upon coal co mposition, system operating conditions, and system design criteria. Mu ch research has been conducted on ash formation and behavior in pulver ized coal- and cyclone-fired utility boilers. Many of the mechanisms o f transformations and ash deposition have been worked out, and predict ive models have been developed. Ash behavior research in fluidized-bed combustion systems has been conducted to determine the effects of coa l quality and operating conditions on bed agglomeration and deposition on heat-transfer and other surfaces. Ash can also influence gasificat ion system operability. Problems such as maintaining slag flow and ash deposition have been encountered. In advanced power systems, hot-gas cleanup is a significant issue in which ash plays a significant role. The issues in hot-gas cleanup include ash deposition on filters, ash r emoval, and vapor-phase and ash-ceramic interactions. The chemical and physical characteristics of the ash also influence their ability to b e collected in air pollution control devices.