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Show 1.0 INTRODUCTION In the combustion of pulverized coal for applications such as MHD power generation or the retrofit of steam boilers designed for oil or gas burners, the rejection of major portions of the coal ash in the combustor is important. In the MHD case, current generator designs^ ' require a thin slag layer to protect the electrodes. However, this requirement can be met by the carry-over of < 20 percent of the slag from the burner. The carry-over of major portions of the slag would not necessarily affect the performance of the generator, per se, but it could present major problems to the downstream boilers and seed separation processes. For the application of retrofitting steam boilers designed for oil or gas firing, the tube spacing within such units is so close that it would lead to serious fouling problems if forced to operate under conditions of heavy slag carry-over from a conventional coal combustor. The work reported in this paper relates to the analysis of a series of tests carried out in Poland as part of an information exchange program between Poland ana the U.S.A. The tests were performed in a 4 MW cyclone design coal combustor at the Nuclear Research Institute in Swierk, Poland. The MHD Division of the Fossil Energy Branch of DOE was the cognizant U.S. agency. The program was designed to investigate the effects of various operating parameters on the performance of the cyclone burner. One operating parameter, coal particle size distribution, was found to have a dominant effect on one of the performance criteria, slag rejection, and it is this relationship that is addressed in this paper. (2) In their early experiments the Polish workers^ ' reported slag rejection levels of 70 to 75 percent when burning polish coals. In subsequent tests using Illinois No. 6 coal they were only able to achieve slag rejection (3) levels of between 25 and 40 percent/ ' A review of the properties of the (4) U.S. and Polish coals ' indicated that the difference in the rejection levels was most likely due to differences in particle size distribution as the U.S. coal was found to be a finer grind. -1- ^7AVCO EVERETT |