Mine emissions reduction installations

Abstract

This paper presents two installation concepts intended to reduce emissions in hard coal mines: emissions of the gas which is high in methane from methane capture process, emissions of the ventilation air which is low in methane, and emissions of the saline mine water. In one concept, the heat from gas combustion in the ventilation air is used to generate superheated steam in a local steam boiler. The superheated steam in a turbine set with a backpressure turbine generates electricity, and the backpressure steam flows into a multi-stage evaporation station where it is used for desalination of portions of mine water. In the second concept, the stream of gas with a high content of methane is supplemented with hard coal in order to utilise the entire stream of mine water. Mathematical models of the component balance of heat and mass are developed for both installations, and calculations are performed using real emissions data from a selected coal mine. Results are shown in mass flow and energy flux Sankey diagrams. We find that full utilisation of the high-methane gas reduces emissions of mine ventilation air by 2.5% and of the saline mine water by 21%. Also, co-firing with supplementary coal ensures a 100% desalination of the mine water and 10% utilisation of the ventilation air.An approximate estimate of the economic evaluation and a sensitivity analysis are also presented for both concepts. Results indicate that the first concept is more profitable than the second concept. This is because the payback period (PP) is shorter (7.67 and 9.67 years, respectively), and the rate of return based on cash flows (ARRCF) is greater (13.03 and 10.36%, respectively) at an unchanged load factor of 90% and a 10-year life cycle. Also, the first concept is found to be significantly less risky. Technical and economic analysis of the proposed solutions shows that both solutions are useful; therefore, the most suitable solution should be chosen based on other conditions such as indicators of state environmental policy.