Water recycling system in a coal beneficiation plant

Abstract

Indian coal in general, contains high percentage or non combustible materials. 30 to 40 percent of the run off mine coal consists of non coal matters, commonly categorized as ash. In order to comply with the specification or the steel plant it becomes essential to beneficiate the raw coal so as to reduce the ash percentage to an acceptable level. Beneficiation of coking coals has been a standard practice in India. Of late, the power plants, major consumer of non coking coal variety. are also becoming more specific towards the quality or coal in respect of ash percentage and such days are not far when coal of any variety will require washing prior to their use. Reduction or ash percentage in coal is realised by beneficiation processes. These processes require huge quantity of water. Almost 90 to 120 gallons of water is required for cleaning one tonne of raw coal. In these processes. 15 to 25 percent or water is lost and the rest of the quantity is recycled. Fresh water is required to be added to make up the loss in every cycle, thereby, requiring extra supply or water and extra consumption of energy. As is well known, fresh water is a scarcely available resource, moreover, thc lost water is always impregnated with ernuents and is a major source of water pollution, particularly when drained into natural streams. An efficient water cycling system should, therefore. be an integral part of any coal beneficiation plant both for minimising specific consumption of water and control of environmental pollution. In this paper, an attempt has been made to critically examine the coal beneficiation process with a special aim to scrutinise water cycle system. An analytical model has been developed to formulate the water cycle with a purpose of examining the scope of improvements in the existing system. Sudamdih coal washery unit of B.C.C.L. has been taken as a case under study.