Cycle improvement and hydrogen steam superheating at Mutnovsky geothermal power plant

Abstract

This study is aimed at a possibility of hydrogen production and hydrogen steam superheating at a single-flash 50 MW Mutnovsky geothermal power plant stage 1. A modification by introduction of a low-pressure single-flash unit utilizing energy of the separated liquid is proposed, and the integrated single- and double-flash cycle is analyzed. The second flash process gives a maximum possible increase of the installed capacity on 11.1 MW for the flash temperature of 92 °C, and 9 MW for 120 °C. Currently the plant does not use 12.3% of the geothermal steam for electricity generation, partly due to demand side management from a grid operator. Excess power can be used for water electrolysis and for each 1% of saved steam 92 t of H2 can be produced annually. Hydrogen combustion in a high temperature hydrogen-oxygen steam generator can be used for steam superheating in a second flash process, achieving the increase of steam temperature at the low pressure turbine inlet by 20–30 K, and an increase of steam dryness at the turbine outlet by 2–4%. Additional available power rises by 5–10% (0.5–0.9 MW) and overall thermal efficiency of the plant can be increased from 10% to 12.5%.