Review of performance improvement of energy recovery turbines in the reverse osmosis desalination

In reverse osmosis desalination industry, the reduction of energy consumption is always one of the hottest topics. In some cases the energy recovery technology can reduce the energy consumption of the reverse osmosis desalination system by 40%-50% [1]. There are mainly four kinds of energy recovery devices: Pelton wheel, reverse running pump, hydraulic turbo charger and pressure exchanger. Hydraulic turbo chargers, one main kind of energy recovery devices, have good applications in reverse osmosis desalination projects because of low initial cost, easy installation and maintenance, availability for a wide range of heads and flows, small footprint, low noise and acceptable efficiency. Moreover, it can be used as a pressure booster for the treatment process of the inter-stage pressurized wastewater reverse osmosis. Its best transfer efficiency reported is 82% [2]. With the popularizing of hydraulic turbo chargers, how to increase the efficiency of turbo chargers causes more and more attention. This paper reviewed kinds of methods to improve the efficiency and performance of hydraulic turbines in desalination industries. Based on computational fluid dynamics simulation and analysis, optimizing the design of the impeller and blade geometry to reduce the impact loss is one of the useful ways to increase the efficiency. Coating the wet surface of turbine plays an important role in improving the wear resistance in surfaces and extending the life of components. To improve the efficiency of turbine at part load, adjustable inlet guide vanes were studied and its inlet angle and outlet angle were optimized. Based on the previous research results and its limitation, future study for improvement and implementation of hydraulic turbine were also discussed.