Determination of optimum washing conditions for a lignite coal based on ash and sulfur content

Abstract

This study deals with the maximization of composite yield subjected to multiple product constraints simultaneously based on float–sink data of a lignite coal from Yozgat-Ayrıdam district of Turkey by using equal incremental product quality approach. Solver and Mathcad were used for determination of optimum separation densities for the coarser size fraction (130×18mm) and the finer size fraction (18×0.5mm) by Dense Medium Bath (DMB) and Dense Medium Cyclone (DMC), respectively. Four different cases were analyzed for the incremental product quality approach. In the first case, composite yield was maximized to 87.45% for the target composite ash of 18.26% with sulfur content of 0.98% when the incremental ashes were equalized by Solver. In the second case, yield maximized to 76.55% for the target sulfur of 0.83% with an ash content of 14.65% by Solver equalization of the incremental sulfur. In the third case, multiple product quality (ash and sulfur) was employed simultaneously by Solver. Yield was maximized only to 66.87% with ash and sulfur content of 11.12% and 0.74%, respectively. In the fourth case, multiple constraints were subjected to the maximization of the yield simultaneously using Mathcad. Yield was maximized to 66.33% with ash and sulfur content of 11.00% and 0.74%, respectively. The yield maximization was successfully achieved using Solver and Mathcad based on multiple product quality (ash and sulfur) constraints simultaneously as well as single product quality constraint.