Slag Rejection in Cyclone 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 and the U.S.A. In their experiments the Polish workers reported slag rejection levels of 70 to 75 percent when burning Polish coals but only achieved rejection levels of between 25 and 40 percent when burning Illinois No. 6 coal. Review of the properties of the two coals indicated that the difference in slag rejection level was probably due to differences in particle size distributions. To be more definitive the effects of particle size on ash rejection was examined through the use of hydrodynamic and coal combustion computer models as applied to the case of the Polish combustor. The computed results indicate that for maximum ash rejection through the flow of slag down the cyclone walls the coal feed should have negligible mass in particles below 30 um and that the fuel rich combustion environment should be maintained as long as possible