Assessing Coal Blends for Ash Deposition and Thermal Performance

摘要

A method for estimating the ash deposition and thermal performance of blends on the basisof the Computer Controlled Electron Microscopy (CCSEM) analysis of parent coals isdescribed in this paper. The paper identifies that the non-additive behaviour of ashdeposition and thermal performance of a coal blend results from the interactions of ashparticles within the deposit. The non-linear thermal behaviour of ash particles in the depositinfluences the deposit growth and deposit structure that consequently influences thethermal performance.The ash deposition is strongly influenced by distribution of minerals in coal. Ashdeposition characteristics of coal blends are highly non-linear with respect to theproportions of coals used in a particular blend. Thus a mechanistic approach based onmineral distribution in coal blend (which is additive) has been discussed here. Themechanistic approach involves models for ash formation, ash transportation, stickinesscoefficient and a model for the deposit structure.For assessing the thermal performance of coal blends it is seen that the ash character andthe nature of ash particles can be interpolated linearly as the mineral matter of coal blend isadditive and the formation of one ash particle is not influenced by the presence of anotherash particle. The only interaction amongst the ash particles takes place within the deposit.The non-linearity in the behaviour of the deposit has been addressed using the viscosity ofthe deposit composition.This mechanistic approach based on CCSEM data and the mathematical models has beenproposed to assess the thermal performance for a number of coal blends for which the heatflux data is available from ACIRL test furnace. The deposit structure and its propertieshave been shown to influence the thermal performance significantly using deposit structureas a function of viscosity of bulk ash at deposit temperature.