Wang Hongsheng, Kong Hui, Wang Jian, Liu Mingkai, Su Bosheng, Lundin Sean-Thomas B
MOE Key Laboratory of Hydrodynamic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China.
Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Molecules. 2021 Nov 22;26(22):7047. doi: 10.3390/molecules26227047.
Solar fuel generation from thermochemical HO or CO splitting is a promising and attractive approach for harvesting fuel without CO emissions. Yet, low conversion and high reaction temperature restrict its application. One method of increasing conversion at a lower temperature is to implement oxygen permeable membranes (OPM) into a membrane reactor configuration. This allows for the selective separation of generated oxygen and causes a forward shift in the equilibrium of HO or CO splitting reactions. In this research, solar-driven fuel production via HO or CO splitting with an OPM reactor is modeled in isothermal operation, with an emphasis on the calculation of the theoretical thermodynamic efficiency of the system. In addition to the energy required for the high temperature of the reaction, the energy required for maintaining low oxygen permeate pressure for oxygen removal has a large influence on the overall thermodynamic efficiency. The theoretical first-law thermodynamic efficiency is calculated using separation exergy, an electrochemical O pump, and a vacuum pump, which shows a maximum efficiency of 63.8%, 61.7%, and 8.00% for HO splitting, respectively, and 63.6%, 61.5%, and 16.7% for CO splitting, respectively, in a temperature range of 800 C to 2000 °C. The theoretical second-law thermodynamic efficiency is 55.7% and 65.7% for both HO splitting and CO splitting at 2000 °C. An efficient O separation method is extremely crucial to achieve high thermodynamic efficiency, especially in the separation efficiency range of 0-20% and in relatively low reaction temperatures. This research is also applicable in other isothermal HO or CO splitting systems (e.g., chemical cycling) due to similar thermodynamics.
通过热化学水分解或一氧化碳分解来产生太阳能燃料，是一种在无碳排放情况下获取燃料的有前景且具吸引力的方法。然而，低转化率和高反应温度限制了其应用。在较低温度下提高转化率的一种方法是，将氧渗透膜（OPM）应用于膜反应器配置中。这能实现对生成氧气的选择性分离，并使水分解或一氧化碳分解反应的平衡正向移动。在本研究中，对通过带有OPM反应器的水分解或一氧化碳分解来进行太阳能驱动的燃料生产进行了等温运行建模，重点在于计算该系统的理论热力学效率。除了反应高温所需的能量外，为去除氧气而维持低氧渗透压力所需的能量，对整体热力学效率有很大影响。使用分离火用、电化学氧泵和真空泵来计算理论的第一定律热力学效率，结果表明，在800℃至2000℃的温度范围内，水分解的最大效率分别为63.8%、61.7%和8.00%，一氧化碳分解的最大效率分别为63.6%、61.5%和16.7%。在2000℃时，水分解和一氧化碳分解的理论第二定律热力学效率均为55.7%和65.7%。一种高效的氧分离方法对于实现高热力学效率极其关键，尤其是在0 - 20%的分离效率范围内以及相对较低的反应温度下。由于热力学相似，本研究也适用于其他等温的水分解或一氧化碳分解系统（如化学循环）。
