Waste heat recovery, utilization and evaluation of coalfield fire applying heat pipe combined thermoelectric generator in Xinjiang, China

Abstract

Coalfield subsurface fires can result in ecological disasters of global dimensions. These fires are difficult to control therefore can result in colossal wastage of resources (the coal itself but the resources devoted to suppression), a serious negative impact on the environment and acute health problems for large populations. However, if the heat can be effectively recycled and utilized, the combustion energy will be recovered but also heat extraction can promote suppression. Thus, leading not only to a positive energy impact but to a reduction polluting emissions and consequent health issues. This paper presents the results of a feasibility analysis of the overall recovery of underground thermal resources of a novel system of Waste Heat Recovery Units (WHRUS) that combines thermosyphon and thermoelectric technologies. Both thermal equivalent model and numerical assessment are presented. A series of realistic-scale field experiment conducted in the Xinjiang's fire zone for an extended period are discussed. Using a local geothermic assessment, the heat recovered from subsurface coal fire can be estimated as the summation of the convective and conductive components of the energy generated. The average heat generated for the fire district is estimated at approximately 495 W/m 2 and the average extraction efficiency at approximately 58%. The WHRUS shows and excellent heat transfer performance with an effective lower resistance of approximately 0.0049 W/°C and maximum thermal recovery rate greater than 90%. Finally, while the thermoelectric

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