(166c) Modeling of reverse electrodialysis for waste heat recovery
AIChE Annual Meeting
2016
2016 AIChE Annual Meeting
Transport and Energy Processes
Modeling, Economics, and Technologies for Sustainable Energy and Advanced Systems II
Monday, November 14, 2016 - 1:20pm to 1:40pm
Reverse electrodialysis (RED) harnesses salinity gradient energy by controlling the ion transport through ion exchange membranes. Natural resources such as sea and river water can be used in the RED process, thus sodium chloride has been commonly used for a variety of the RED researches. However, those resources require the repetitive shipping and pretreatment cost and can act as a locational limitation for installation of the RED plant. A closed-loop RED, which uses thermolytic solution, can solve these issues as well as generate electricity. In recent yea rs, ammonium bicarbonate (NH4HCO3), which can be separated by relatively low temperature around 60â??, has been investigated as a promising solute that enables the system closed-loop. Therefore, the closed-loop system keeps the salinity gradient by solute separation and recapturing process.
In this study, we developed a numerical NH4HCO3-RED model for the investigation of the RED performance. Because of the unclarified electrochemical information of NH4HCO3 in solution, such as activity and equilibrium constant, the Planck-Henderson equation was used to approximate the membrane potential. And, solution resistance was experimentally calculated by the definition of the molar conductivity. Moreover, permselectivity that has been assumed either as a unity or some constant value in previous researches was also experimentally obtained to estimate the performance more precis ely.
We found the developed NH4HCO3-RED model was in great accordance with the experimental results under various operating conditions. Using the developed model, we also characterized the net power density, which considers the pumping loss. In our system, the maximum net power density of 0.84 W/m2 was obtained at an optimum operating conditions that the intermembrane distance of 0.1 mm, the concentration ratio of 200 (2.0 M/ 0.01 M), and the flow rate of 3 mL/min. We believe that this study will improve our understanding of the NH4HCO3-RED system for& nbsp;a novel waste heat recovery technology.
In this study, we developed a numerical NH4HCO3-RED model for the investigation of the RED performance. Because of the unclarified electrochemical information of NH4HCO3 in solution, such as activity and equilibrium constant, the Planck-Henderson equation was used to approximate the membrane potential. And, solution resistance was experimentally calculated by the definition of the molar conductivity. Moreover, permselectivity that has been assumed either as a unity or some constant value in previous researches was also experimentally obtained to estimate the performance more precis ely.
We found the developed NH4HCO3-RED model was in great accordance with the experimental results under various operating conditions. Using the developed model, we also characterized the net power density, which considers the pumping loss. In our system, the maximum net power density of 0.84 W/m2 was obtained at an optimum operating conditions that the intermembrane distance of 0.1 mm, the concentration ratio of 200 (2.0 M/ 0.01 M), and the flow rate of 3 mL/min. We believe that this study will improve our understanding of the NH4HCO3-RED system for& nbsp;a novel waste heat recovery technology.