Water and energy assessment for dewatering in opencast mines

Pumps are used in mines for dewatering and consume about 18% of the total energy usage in an opencast coal mine. Quantitative estimation of water removal rate in a mine is necessary for designing an effective dewatering system and to minimise energy consumption. In this paper, a generic model is proposed to estimate water and energy requirement for pumping in an opencast mine based on the mine excavation characteristics. The modelling framework is used to estimate specific water removal (SWR) and specific energy consumption (SEC) for water pumping in an opencast mine of a given topography, climatic condition and soil properties. A case study of water pumping of an opencast coal mine in India resulted in SWR of 22.8 m3/t and SEC of 8.97 kWh/t of coal for a maximum daily rainfall of 100 mm/d in the year 2010. The results show that the SEC increases by 34% from 3rd year in 1998 (6.65 kWh/t) to the 15th year (8.97 kWh/t), with progress of mining. The model can help the mine planner to decide the pump capacity and operating strategy for optimal energy usage.