Shichang Xu

Experimental studies on dynamic process of energy recovery device for RO desalination plants

A two-chamber hydraulic energy recovery unit with a programmable controller and a data acquisition system was set up. Tap water was used as the working fluid instead of the actual seawater and concentrate in SWRO desalination plants. Experimental results were obtained on the fluctuations of the pressure and flow rate to and from the energy recovery unit. Characteristics of the pressure at the chamber ends were discussed at the conditions of the chambers set horizontally or vertically, with and without pistons.

Polypyrrole/polyaniline composites with enhanced performance for capacitive deionization

AbstractPolypyrrole/polyaniline (PPy/PANI) composites used for capacitive deionization were synthesized by in situ chemical oxidation polymerization method. The preparation parameters including the acid type, the acid concentration and the oxidant concentration were investigated and optimized in terms of the textual properties, the cyclic voltammetry tests, and the electrochemical impedance spectroscopy measurements. The obtained PPy/PANI composites present relatively uniform nanorod morphology with an average pore diameter of 13.1 nm. The specific capacitance of the composites under the optimal conditions is up to 341.4 F/g, which is approximately thrice that of pure PPy and twice that of pure PANI. The saturated adsorption capacity of the PPy/PANI–carbon nanotube (CNTs) cell was obtained as high as 197.8 mg NaCl/g, which is approximately 1.7 times of the PPy–CNT cell and 2.1 times of the PANI–CNT cell, respectively.

Development and stand tests of reciprocating-switcher energy recovery device for SWRO desalination system

AbstractIn this paper, a novel piston exchanger—reciprocating-switcher energy recovery device (RS-ERD) was introduced and developed. The RS-ERD adopts the unique open/close plate design, which not only ensures a perfect sealing effect and high efficiency of the device, but also favors avoiding the destruction of micro-particles in the liquid occasionally. For proving the operating performances of the RS-ERD, an emulating RO-ERD desalination platform was established and the testing conditions were regulated as ERD capacity of 30 m3/h and operating pressure of 6.5 MPa. The experimental results indicate that the operating stability of the RS-ERD is good. The leakage ratio of the device is lower than 1.7% and the energy recovery efficiency is above 98%, which can satisfy the industrial requirements of the SWRO plant.

Pilot tests of fluid-switcher energy recovery device for seawater reverse osmosis desalination system

Abstract Energy recovery devices (ERDs) reduce the power consumption of seawater reverse osmosis (SWRO) systems greatly by recovering the pressure energy in the retentate brine. There are basically two types of ERD in the market, the isobaric type and the centrifugal type. Of which the former achieves rapid progress and holds the leading position in recent years due to its high efficiency. In this article, a pilot-scale fluid-switcher ERD (FS-ERD, isobaric type) was designed and tested under the capacity of 30 m3/h and the operating pressure of 6.0 MPa. The fluid dynamics performances and the efficiency of the device were studied and evaluated. The demonstration shows that the FS-ERD presents good stability with negligible pressure pulsations and high energy recovery efficiency of about 95.9%, which paves the way for the application of FS-ERD in SWRO plants.

Transport mode of membrane distillation process and the VMD method to determine the membrane configurational number

Abstract A vacuum membrane distillation (VMD) method was employed for the direct determination of configurational number rϵ gt for porous membranes used in the MD process. For the same purpose, the transport mode was investigated experimentally. Results showed that mass transfer of the MD process is predominated by Knudsen diffusion in our experimental system. Although greatly discrepant from the predicted value based on assumption, the directly obtained rϵ gt value correlates well with flux, pressure and temperature.