Simultaneous CO2 treatment and blue energy generation from wasted industrial streams

Abstract

In the last decade, there has been an increased global need for finding bright solutions to tackle industrial wastes and emissions release. Herein, this work explores the utilization of a compact Reverse Electrodialysis (RED) system that transforms the chemical potential energy of mixing an ammonia based purified industrial wastewater stream (low concentration stream - LC), with an effluent high salinity RO brine stream (High concentration-HC) into viable electrical energy. The LC and HC streams are directed from ammonia production plants and seawater reverse osmosis desalination plants, respectively. The acquired electrical energy from this RED process is simultaneously used to power an Electrochemical (EC) system. The electrochemical system utilizes two critical waste streams produced from ammonia production plants. One being a wastewater stream that is purified in the anode chamber of the cell via the use of active chlorine species, and the other being the huge amount of emitted CO2 that is directed into the cathode chamber and there converted to value added chemicals. The purified wastewater stream coming out of the EC system is used as the aforementioned LC stream in the RED process, hence, forming an integrated RED-EC system that manages industrial waste streams, minimizes liquid discharge & CO2 emissions, and employs a sustainable internal energy production process. In this study, the RED system is first optimized to attain the maximum power density through exploring the influence of concentrate and dilute stream concentrations, compositions and flowrates. In addition, to the number of membrane pairs needed to produce desired voltages. The RED cell gave a maximum power density of 3.25 Wm-2 with 20 membrane pairs and a salinity gradient of 0.98M between a concentrated brine stream and a mixed NaCl/(NH4)2SO4 stream. Furthermore, around 15 cell pairs were needed to provide -1.5 V of energy to drive CO2 conversion to formate.