Residual steam to energy: a project for Los Azufres geothermal field, Mexico

More than 500 t/h of residual steam are discharged into the atmosphere at Los Azufres geothermal field. Steam comes from nine back-pressure turbines that are at present generating 45 MW. A significant increase in output can be obtained if low pressure turbines are installed to expand residual steam from atmospheric pressure up to a vacuum pressure in condensing cycles. A net output optimization process for each unit in the condensing cycle is presented here. The exergy concept is also applied to compare efficiencies of back pressure cycles with new condensing schemes that include low pressure turbines. Results show that 27.8 MW of additional net output can be generated with the new schemes at competitive production costs and higher conversion efficiencies.