Investigation on the operating capacity expansion through parallel schemes of reciprocating-switcher energy recovery device for desalination: Simulation, verification and parameterization

Abstract

Parallel operation is a significant and feasible method to compensate the insufficient capacity of single reciprocating-switcher energy recovery device (RS-ERD) in membrane desalination system. To grasp the operating characteristics in capacity expansion, three parallel schemes of RS-ERD, single-operation scheme, two-parallel scheme and three-parallel scheme, are investigated through the numerical simulation, experimental verification and theoretical parameterization. Results indicate that, the two-parallel scheme and three-parallel scheme achieve the flowrate continuity of low-pressure seawater and the flowrate fluctuation amplitudes in parallel RS-ERDs decrease by 50 % and 83 % respectively when compared with single-operation scheme. Parallel operation schemes also broaden the flowrate range with high efficiency for RS-ERD. To ensure the 95 % energy recovery efficiency, two-parallel and three-parallel schemes expand the maximum flowrates to 140 m3/h and 210 m3/h in contrast with the 70 m3/h of single-operation scheme. In addition, the two-parallel and three-parallel schemes of RS-ERD realize the much lower specific energy consumption (SEC) of 2.11 kWh/m3 and 2.09 kWh/m3 than the 2.23 kWh/m3 in single-operation scheme which contributes to the operating costs savings about 63,830 CNY and 75,778 CNY in one year. This research provides a new perspective in capacity expansion through the parallel operation of energy recovery devices.