A new preliminary system design of using geothermal well brine heater for desalination/nanofiltration process

Abstract

In this work, a novel system design of using geothermal well energy acting as a brine heater for desalination purposes has been numerically developed and investigated. The system contains a pumping unit, nanofiltration, flash evaporation unit, and end condenser for condensation and freshwater production. The system aimed to pump the pre-treatment brine flow into the geothermal well (abandoned oil well) benefiting from its energy considering the well as an underground brine heater. It is anticipated by the geothermal well to increase the brine temperature up to an optimized value (40–50 °C). A Flash evaporation tank has been used as a steam generator. The brine blowdown will be dumped into the sea. To prevent corrosion and tubes deterioration, the Nanofiltration system has been used as a pre-stage before pumping the saline flow into the geothermal well. Reducing the salinity gradient was considered an important issue during this study. The salt-free steam will be directly flowing towards the condenser unit for condensation and freshwater production. It is expected to produce an amount of freshwater in the range of 500 to 1500m3/day. Results reveal that the total hourly costs are 1.185$/h and total water price was in the range of 0.12$/m3 to 1.2$/m3 depending on the performance and salinity concentration of the Nanofiltration system.

Keywords

• Geothermal well
• Nanofiltration
• Desalination
• Direct vapor generation
• Brine heater
• Condensation