Considerations to improve the recovery of the thermic component of the compressed air for compressor stations

The paper refers to energetic and ecological aspects in the operation of volumetric piston compressors used in compressor stations in mines. The applied analysis method is based on the generalization of the pinch technology and the use of Carnot temperature, also taking into account thermodynamics concepts in finite time. As a result of this analysis, a series of solutions for recovery and valorification of the thermal component in the compressed air energy on the following circuits are proposed: low pressure stage of the intermediate cooler compressor; and high pressure stage of the final cooler. Simultaneously, the effects of recovery on the humidity of compressed air, forced in the transport and distribution network are followed, paying attention to the aspects concerning the environmental pollution. This paper is justified by the big energy losses reported at coal mines compressor stations, where the installed power afferent to the compressors is of the order of thousands of kW and the delivered compressed air flows reach 1000-1500 m³ _N/min. The proposed recovery and valorification solutions are comparatively analyzed, advantages and disadvantages being pointed out. The proposed recovery solutions include: classic heat exchangers; heat exchangers with plates; heat exchangers with thermal tubes; and absorbtion heat pumps