Integration of a turbine expander with a synthesis gas process – Using process gas as a working fluid

Abstract

Synthesis gas production provides an excellent opportunity for integration of a turbine expander since the heat is available at very high temperatures (900–1400 °C). This case study considers the integration of a turbine expander with a synthesis gas production process that uses auto-thermal reforming for Fischer-Tropsch synthesis. Auto-thermal reforming technology is a commercialised technology that is well suited to large scale synthesis gas production processes. A methodology that was previously developed and published by the same author is applied in this case study, resulting in an improved flow sheet with significantly improved power output and thermal efficiency improvement. The new flow sheet comprises a unique power production system that uses synthesis gas as a working fluid and wherein the sequence of compression and expansion are reversed in position, compared to conventional power production systems. A conventional steam cycle is also coupled to this synthesis gas power production system to render a combined synthesis gas and steam power production arrangement.Simulation models were created of the conventional and new integrated flow sheets and the analysis focussed on pressure ratio variations across the turbine expander. It is shown how such variations affect other parameters in the system. In one of the cases a 37% improvement in net work was obtained from the new integrated flow sheet compared to the conventional flow sheet. The results are also compared to the results obtained in a recent study on integration of a turbine expander with a steam methane reformer, and further options to implement the synthesis gas power production system for a steam methane reformer are explored.