Simulation and experiment for flux and power density of Pressure Retarded Osmosis (PRO) with tubular module

• Main Authors: Shih-Kai Hung, 洪士凱
• Other Authors: Ching-Jung Chuang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/fvh2yv

碩士 === 中原大學 === 化學工程研究所 === 106 === Over the last few decades, access to fresh water and energy resources became one of the most important issues in the world due to the rapid growth in world’s population, the serious change in global environment and the decline in available energy. Renewable energy has been growing since it can reduce the environmental impact of energy generation. The Pressure Retarded Osmosis (PRO) process is one of the emerging green energy technologies. PRO saves the operating space since it uses membrane technology, and it is not affected by the climate and has high stability to produce energy for it uses osmotic pressure difference as a driving force. Briefly, PRO is a process that has a great potential in producing green energy. In this study, simulation models are established to estimate the flux and power density of PRO, and a self-assembly TFC tubular membrane module is used to conduct PRO experiment. The effect of different operating parameters, such as temperature, concentration and flow rate on the PRO process performances are analyzed. Firstly, simulations based on the characteristics of membranes and modules from two literatures are carried out and compared with its experimental data. Results show that the relative differences between both are in a range from 3.46 ~ 23.68 %, respectively. As for the experiment with TFC tubular membrane module, the fluxes are found to be 1.93 ~ 3.01 and 3.66 ~ 3.27 kg/m2·hr, and the power density are 0 ~ 0.25 and 0 ~ 0.27 W/m2, respectively, when 1 and 2 M sodium chloride solution are used as draw solutions. The experimental data compared with simulation results shows a relative difference to be ranging from 0.37 ~ 4.43 and 0.72 ~ 8.67 %, respectively. The influence of concentration polarization on PRO is analyzed and concluded that the internal concentration polarization is the main factor affecting the performance, and the external concentration polarization has only a little effect. Experiment of PRO with three different draw solutions based on the same osmotic pressure as 1 M sodium chloride solution showed the sodium chloride solution has the best performance, followed by magnesium chloride and sodium sulfate solution, because of their respective solute diffusion. The maximum power density could be 1.85, 1.12 and 0.84 W/m2,respectively. Finally, using the membrane parameters from literature to simulate the power density of PRO with high salt concentration seawater brine as draw solution is discussed. Assume that draw solution is the brine from SWRO+MD process to reach 60 and 80 % water recovery, respectively. When the temperature is in between 35 ~ 55 ℃, the maximum power density calculated is in a range from 55.81 to 79.89 and 157.36 to 237.29 W/m2, respectively. However, to obtain this high power density, the hydraulic difference most reach 47 to 48 and 106 to 111 bar. Whether the membrane tube strength and module design can withstand this high pressure is another problem that must be considered in engineering applications.