Low-grade heat utilization in the methanol-fired gas turbines through a thermochemical fuel transformation

Abstract

Methanol can be considered as an alternative fuel for different engines. This paper investigates the low-grade heat utilization in methanol-fired gas turbines. Two cases were analyzed: the first is low-grade heat utilization for steam generation, and the second is for methanol decomposition before its combustion. The concept of low-grade heat utilization via methanol decomposition is developed and described in details. The comparative thermodynamic analysis was performed via Aspen HYSYS under the wide ranges of the operational parameters: gas turbine inlet temperature of 800–1000 °C, compression/expansion ratio of 9–15. The temperature potential of low-grade heat was set from 200 to 400 °C. It was established that low-grade heat utilization via methanol decomposition is more efficient (up to 5%) in comparison to low-grade heat utilization via steam generation. Methanol decomposition before its combustion leads to an increase in the power output in the gas turbine. Simulation tests of various temperatures potential of low-grade heat showed that it does not play a significant role in the efficiency of utilization. However, it was determined that maximal methanol decomposition is observed at a temperature above 300 °C. The Sankey diagrams for the energy flows are depicted and analyzed. The future perspectives of the use of the low-grade heat utilization concept via fuel decomposition were described for carbon-free fuel–ammonia. • Low-grade heat utilization via methanol decomposition concept. • Chemical energy of methanol is converted into heat in two stages. • Efficiency of low-grade heat conversion to electricity is up to 36% • Heat utilization via methanol decomposition is up to 5% more efficiently than traditional ways. • Methanol decomposition before combustion is “chemical exergy pump”.