Performance Tests And Scale-up Design Of Self-boost Energy Recovery Device For Seawater Desalination System

Energy Recovery Device(ERD)can reduce the specific energy consumption and cost of permeate,which is the key equipment of membrane desalination system.Positive displacement(PD)ERD is the main body of popularization and application.Based on the Fluid-Switcher Energy Recovery Device(FS-ERD),this paper introduces a self-boost energy recovery device(SB-ERD).The pressure-differential hydraulic cylinder has replaced the original hydraulic cylinder,which reduces the cost of equipment investment and simplifies the system process.A self-boost energy recovery device(SB-ERD)is firstly introduced,and the structure characteristics and working principle of the SB-ERD are introduced in detail.Then apply it to a nanofiltration seawater desalination system.The performance of ERD and energy-saving contribution are tested and evaluated in the nanofiltration seawater desalination system.The coupling of SB-ERD and nanofiltration desalination unit is studied under the pressure of 1MPa,1.5MPa and 2MPa.The results indicate that the step-up ratio is 1.19,the maximum pressure fluctuation of high pressure brine is 0.06 MPa,the energy recovery efficiency reached up to 92.3% under the operating pressure of 1.00 MPa.The step-up ratio is 1.19,the maximum pressure fluctuation of high pressure brine is 0.17 MPa,the energy recovery efficiency reached up to 96.5% under the operating pressure of 1.5MPa.The step-up ratio is 1.20,the maximum pressure fluctuation of high pressure brine is 0.24 MPa,the energy recovery efficiency reached up to 98.7% under the operating pressure of 1.00 MPa.Comparative analysis of the energy consumption of the nanofiltration desalination system with SB-ERD and with FS-ERD is studied under the pressure of 1MPa,1.5MPa and 2MPa.The SB-ERD keeps good energy-saving contribution.The reductions of energy consumption are 0.062 kW,0.088 kW and 0.081 kW respectively.The nanofiltration desalination system coupled with SB-ERD not only reduces the cost of equipment investment and simplifies the system process,but reduces the energy consumption of the system in a way.To study the flexibility of the SB-ERD coupled in the nanofiltration desalination system,experiment is carried out under different pressure and concentration of the seawater.The results indicate that the running time of the piston reduced from 9 seconds to 8 seconds with the increase of operating pressure.The running times of the piston are 8 seconds and 7 seconds with the water conductivity are 24.7ms/cm and 34.2ms/cm under the operating pressure of 2MPa.The SB-ERD can adapt to the changes of the system flexibly under the control mode of double in place.Based on the performance of the SB-ERD,a new self-boost energy recovery device is designed whose capacity is 15t/h and the operating pressure is 6.5MPa.In order to improve the operation stability of the device,the internal structure of the fluid switcher is optimized.A new pressure-differential hydraulic cylinder in the form of piston rod are connected at one end of the piston is proposed,which will avoid the happening of the different piston speeds.The step-up ratio also can be adjusted to adapt to the seawater desalination systems with different pressure losses.