Methods of waste heat recovery - A compressor station case study

This document deals with waste heat recovery from a natural gas compressor station driven by a set of 7 gas engines. Attention is paid to waste heat from engine exhaust gases. Possible options of energy recovery include: a) direct heat recovery with optional thermal energy storage, b) conversion of waste heat to electricity via an ORC module, or c) integration of gas expanders into the gas supply line in junction with waste heat recovery. Options for direct utilization of the recovered waste heat comprise: a) supply of heat for the in-house demand of the CS object, b) supply of heat of a larger residential consumer c) supply of heat for a dedicated consumer, intentionally located next to the CS. For external supplies heat can be supplied by pipeline or via a mobile PCM storage. The studied options were related with the possible pilot plant design bottoming 1 or 2 engines with a waste heat recovery system. For the potential pilot plant, the total rate of waste heat recovery from the CS is low, ranging from 3.1% to 11.6% for the studied cases. Effects related only to the given engine represent between 19.3 and 41.4% recovery rate. Simultaneously, these effects are significant for the studied consumers, being able to cover between 33.7 to even 98.1% of their demand from the waste heat recovery source. A PCM storage has a weak and non-uniform effect on system performance, depending on the profile of source and consumer. Direct heat recovery is recommended for a pilot plant, and the recovered quantity of waste heat may reach 900 MWh/year from a single engine if operated continuously. Electricity generation may reach 530 MWh year (gas expander system) or about 300 MWh/year (ORC system), however, the latter should be recommended for more than one engine as waste heat source. Intentional location of a heat consumer near the waste heat source as well as increasing the time of operation of the bottomed engine are two recommendations of this study.