Artificial weathering of coal to enhance milling performance

The mined coal need to be comminuted to use as source of energy or reducing agent. This study is carried out to explore a process inspired from nature to soften the coal to enhance the energy efficiency of milling. Coal samples were artificially weathered for different time duration (3, 7, 10 days) using solutions of different pH (2, 7, 12). Thawing and freezing cause swelling and shrinking in the coal particles. Samples were passed through various thawing-freezing cycles (3, 6, 9 cycles) to estimate the effect of natural weathering which weaken the rocks. Experiments were carried out at pH of 7 using a cold cell and heating oven. Studies indicated that pH variation during artificial weathering can reduce average particle diameter by almost 8.8-21.4% more over the untreated coal samples for treatment pH range 2-12. Time also play critical role but increased time has negative effect on size reduction. Thawing and freezing physically degrade the coal and reduce average diameter by 16.45% lesser than untreated samples. In the current scenario low grade natural resources need to be comminuted into proper sizes for efficient utilization and proposed technique can improve energy efficient coal comminution.