Stirling Bottoming Cycle for the Gas Turbine Exhaust Streams of Pipeline Compressor Stations

In pipeline compressor stations natural gas fuelled aircraft derivative gas turbines are frequently used in conjunction with a power turbine to drive the large centrifugal compressors for ‘boosting’ the pipeline pressure. Typically two thirds of the energy provided to drive the turbine is carried off as heat in the exhaust stream. These hot exhaust streams, typically at temperatures around 500 K contain very substantial energies, 50 MW being not uncommon.

This paper summarises recent studies carried out to assess the feasibility and worth of applying Stirling power systems to generate electric power from these ‘waste’ streams. Both ‘bottoming’ and topping cycles are of interest and are briefly considered in this paper.

An elementary, but realistic, performance analysis indicates the possibility of recovering as much as 9 MW power from the exhaust of a gas compressor equipped with a Rolls-Royce RB 211 aircraft derivative gas turbine. There are approximately 6000 gas turbine/compressor units in 2750 gas pipeline compressor stations distributed throughout North America. On this basis it appears feasible that as much as 54,000 MW electric power may be generated from the existing turbine exhaust. It is anticipated the cost of the Stirling engine system would be about half the cost of the alternative Rankine cycle system.