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Show LABORATORY-SCALE ASH DEPOSITION STUDIES OF A SIZEAND GRAVITY-FRACTIONATED COAL S.A. Benson, W.H. Puffe, and M.L. Jones Energy and Mineral Research Center University of North Dakota Box 8213 University Station Grand Forks, NO 58202 R.W. Borio and J.F. Durant Combustion Engineering Windsor, CN 06095-0500 A.K. Mehta Electric Power Research Institute Palo Alto, CA 94303 INTRODUCTION Paper No. 20 A major problem associated with the use of coals in utility boilers is the tendency to form deposits on fireside heat transfer surfaces. The formation of ash deposits is a complex problem that at the present time cannot be accurately predicted based on coal composition and combustion conditions. The formation of tenacious deposits involves the transformation of inorganic coal components during combustion and gas-cooling phases and the interaction of ash components upon deposition. In many cases, specific inorganic constituents associated with coals playa key role in the formation of ash deposits in coal-fired combustion systems. For example, iron-rich species have been correlated with the formation of slag deposits in the radiative sections of combustors (1) and alkali and alkaline earth elements contribute to the formation of fouling deposits in the convective passes of combustors (2). Pilot-scale furnaces are being used to determine the effects of coal composition and combustion conditions on ash deposition propensities of coal. Testing with these systems requires a significant degree of effort and cannot be conveniently used to determine the effects coal size or gravity fraction on ash deposition. Laboratory-scale devices, such as drop-tube furnaces equipped with deposition probes, can be used to combust coals and form deposits under closely controlled conditions. Drop-tube furnaces have been used to determine the types of particles that initiate ash deposit formation (3, 4) and to study deposit growth and the development of deposit strength (5, 6, 7, 8). The Electric Power Research Institute (EPRI) has sponsored a program with Combustion Engineering (CE) to test the combustion characteristics of coals of various qualities in -a pilot-scale combustion furnace. The objective is to extrapolate the results to predict full-scale boiler performance. As an adjunct to the CE program, EPRI has initiated another project with the University of North Dakota Energy and Mineral Research Center (EMRC). The objectives of the EMRC program are to investigate the feasibility of using a drop-tube furnace as a test to evaluate the slagging and fouling potentials of |