Evaluation of waste brine utilization from LHD unit III for electricity generation in Lahendong geothermal field, Indonesia

Abstract

The geothermal power plant (PLTP) LHD unit III in Lahendong geothermal field is scheduled to begin operation in 2008. The power plant and the piping are under construction. This plant is supplied from the wells in cluster-5 of Lahendong geothermal field. More than 600 tons/hr of separated water at a temperature of 180¢ªC will be reinjected directly into the reinjection well. The separated water comes from the separator which is supplied from 4 production wells in this cluster. These wells produce two-phase fluid with a wetness of 80%. The dry steam from the separator will be used to generate 20 MWe from a condensing turbine single-flash electric power plant which is to be operated by the state electricity company. The separated water will be reinjected. The paper discusses alternatives for possible additional electricity production from the separated water, which still contains high enthalpy, by using direct flashing of hot brine or using hot brine to heat the secondary fluid with a binary or Kalina cycle. These alternatives are tested by building a power plant model and doing model simulations. The rejected brine can generate 4.8 MWe using a flash system with a condensing turbine, and 4.57 MWe by using a binary cycle. The design considerations, utilization limits due to chemical problems, and the optimum parameters to get maximum electricity generation are also discussed.