Effect of coal size and process variables on coal cleaning efficiency in an air dense medium fluidized bed

Abstract

The quality of India coal is poor because of high ash content. Some improvement in its quality can be brought using different coal cleaning methods. Wet cleaning methods like Heavy media separator and jigging are extensively in use but they have some limitations like they produce large amount of coal slurry which is difficult to dispose and they degrade friable coal. To overcome these limitation dry cleaning method can be employed and air dense medium fluidized bed is one of the most economic and efficient method. The separation in the fluidized bed greatly depends on the process variables of the gas solid two phase flow. In this project the effect of coal size and process variables on the coal cleaning efficiency is studied using Basundhara coal and magnetite as bed material. The coal cleaning experiments were carried out on three size fraction of coal i.e. -12+10mm,-10+5mm and -4.75+1mm.The efficiency were expressed in terms of percentage enrichment, percentage ash rejection, percentage combustible recovery and separation efficiency. The maximum separation efficiency of 10.5% is achieved for -10+5mm size fraction. It was observed that batch should operate at a flow rate of 50-60lpm and between coal to magnetite weight ratio of 0.2 to 0.3 for maximum separation.