Capacity Flexibility Test And Evaluation Of A Reciprocating-switcher Energy Recovery Device For SWRO System

Seawater reverse osmosis(SWRO)is one of the most important ways to solve the shortage of fresh water in the world.Most of the SWRO desalination systems adopt energy recovery devices(ERD)to reduce the energy consumption of permeating.Reciprocating-switcher energy recovery device(RS-ERD)is gradually been adopted by the desalination engineering for its high efficiency,good resistance to particles and low machine precision.Developing a RS-ERD with flexible capacity and large capacity for a single device has great significance on promoting the SWRO desalination technology.A SWRO desalination test platform was set up which can evaluate the ERD comprehensively.The research work in this paper includes two aspects.One is to investigate the adaptability and the capacity flexibility in SWRO desalination system.The other is to carry out the optimizing and amplifying design for RS-ERD according to the current existing problems.The existing problems on RS-ERD are systematically analyzed and solutions are proposed on the structure of valve plate and the hydraulic driving.The adaptability and the capacity flexibility of RS-ERD were tested in the SWRO desalination test platform.RS-ERD can be operated stably in signal control mode under the condition of 30m~3/h and 6.0MPa.The pressure and flow fluctuation amplitudes in high pressure brine are 0.5MPa and 0.7m~3/h,and the energy recovery efficiency is 97.37%,which shows good adaptability to the SWRO desalination system.The capacity flexibility test of RS-ERD is investigated under the capacity of20m~3/h,25m~3/h,30m~3/h,35m~3/h,40m~3/h,45m~3/h respectively.The research results show that the high pressure fluid keeps stable in the test range and the maximum fluctuation amplitudes in pressure and flow are 0.5MPa and 0.8m~3/h.There is a small increase in high pressure loss and the pressure loss increases from 0.024MPa to0.068MPa.The internal leakage increases from 0.79m~3/h to 1.18m~3/h and the leakage ratio decreases from 3.95%to 2.62%when the capacity increases from 20m~3/h to45m~3/h.The energy recovery efficiency remains at above 96.50%and mixing degree remains at below 1.5%in the test range.The performance keeps stable in the varying flow rate,which shows flexible capacity from the comprehensive indicators.An optimizing and amplifying RS-ERD is designed on the basis of the original device.The design capacity is 65m~3/h and the design working pressure is 6.5MPa.The synthetical structure of pre-plates and main-plates is conducive to reduce the shunt volume and the fluctuations.The hydraulic cylinder in new type and the vertical installation appear in the new designing.All these changes will promote the performance and operation in engineering for RS-ERD.