Use Of Waste Heat From Gas Turbine Modular Helium Reactor For Desalination

The Gas Turbine Modular Helium Reactor (GT-MHR) uses a direct closed Brayton cycle for power conversion. In the Brayton cycle, the heat is rejected in a precooler and intercooler at a relatively high temperature. In the reference design of the GT-MHR, the outlet temperature of cooling water used to reject the heat is about 60 deg. C. At this temperature level, rejected heat can be used for desalination of sea or blackish water very effectively. In the case of the GT-MHR, the desalination will be using the waste heat which has to be rejected to close the Brayton cycle. In most other power plants the steam, which could otherwise be used to produce power, is used for desalination. The Advanced Multi Effect Distillation (AMED) process can operate at lower temperatures and will be the most effective process for GT-MHR. The membrane driven desalination process [reverse osmosis (RO)] is very energy intensive requiring 4-6 kWh of energy per m³ of water produced. The power requirement for the RO process can be reduced in conjunction with the GT-MHR by using the waste heat from the Brayton cycle to preheat the sea water to 50 to 60 deg. C. This decreases the viscosity of the water and reduces the required pumping power by 15 to 20%. A 1200 MWe GT-MHR will produce 114,000 m³/day of fresh water with AMED system by using waste heat only. This compares with today's typical plant producing 40,000 m³/day and worldwide production of 34,000,000 m³/day. (author)