Waste energy recovery in seawater reverse osmosis desalination plants. Part 2: Case study

Abstract

The present study is a continuation of a previous work which dealt with the performance evaluation of seawater reverse osmosis SWRO plants equipped with energy recovery devices (ERDs). Energy recovery devices are an important part of any seawater reverse osmosis system, and any future decrease in specific energy consumption is dependent upon the future development and improvement of such devices. The present study is applied on the 252 m3/h seawater reverse osmosis (SWRO) desalination plant that is currently under operation in Egyptian propylene & polypropylene (EPP) Company located in Port Said city, Egypt. The EPP seawater RO plant consists of five major systems: seawater supply, seawater pretreatment, high pressure pumping with energy recovery devices, RO modules, and permeate post treatment. The plant is made up of two stages of RO membrane systems. The first stage consists of three similar trains of 94 m3/h capacity each and the fourth train of 124 m3/h capacity. The output water salinity from the first stage is 238 ppm, measured as total dissolved solids (TDS). Then the output flow from the first stage is treated again in the second stage RO units (three trains of 84 m3/h capacity each) to achieve salinity of 8 ppm. The objective is to present field results of the EPP-SWRO plant operation in order to measure and evaluate the performance improvement due to using two different types of energy recovery devices (ERDs). The results showed that, for the first pass, the effect of using ERDs leads to reduction in the SPC for all trains which varies between 6 and 7 down to 3:4 kWh/m3. The resultant energy saving is 41:42%. While the SPC is found to be 1.6:1.7 kWh/m3 for the second pass. On the other hand, the actual recovery is between 31 and 34%, and 91 and 93% for the first and second passes respectively. Finally, an acceptable agreement between actual and design results has been noticed. © 2012 Elsevier Ltd. All right reserved.