Abstract:

Compared with single-stage reverse electrodialysis, multi-stage reverse electrodialysis (MSRED) has more advantages in the output power of reverse electrodialysis heat engine, because it can convert more salinity gradient energy into electricity. In order to further improve the output power of MSRED, the total net output power of the device when used as the MSRED working solution was compared between the previously developed LiCl-NH₄Cl aqueous solution (mass molar ratio of 2∶8) and the traditional NaCl aqueous solution. The parameters include current density, initial molality concentration of feed solution and the flow velocity of feed solution. The results show that MSRED with LiCl-NH₄Cl aqueous solution can achieve higher current output, and the total net output power of MSRED can be increased by up to 28.6% compared with that of NaCl aqueous solution with the same mass molar concentration. In addition, no matter how the relevant operating parameters change, the MSRED using LiCl-NH₄Cl aqueous solution can obtain higher total net output power than that of NaCl aqueous solution with the same mass molar concentration. At the same time, the number of stacks employed in the system is smaller, which can save equipment costs and reduce the volume of the device.

Key words: multi-stage reverse electrodialysis, salinity gradient energy, solution, heat engine, mixtures, ion exchange

摘要：

与单级逆电渗析相比，多级逆电渗析（multi-stage reverse electrodialysis，MSRED）在逆电渗析热机输出功率方面更具有优势，因其可将更多的溶液盐差能转换为电能。为进一步提高MSRED 的输出功率，对比研究了先前开发的LiCl-NH₄Cl水溶液（质量摩尔比为2∶8）与传统NaCl水溶液在作为MSRED工作溶液时装置的总净输出功率。结果表明，采用LiCl-NH₄Cl水溶液的MSRED能够实现大电流输出，且与等质量摩尔浓度的NaCl水溶液相比，MSRED的总净输出功率最高提升28.6%。另外，无论相关工况参数如何变化，采用LiCl-NH₄Cl水溶液的MSRED均能获得比等质量摩尔浓度的NaCl水溶液条件下更高的总净输出功率；同时系统所使用的电堆数量更少，从而可节省设备成本并减小装置体积。

关键词: 多级逆电渗析, 盐差能, 溶液, 热机, 混合物, 离子交换