硫碘循环制氢中电化学Bunsen反应的动力学及流动、传质与反应特性研究

The electrochemical Bunsen reaction has advantages in reducing the excess iodine and realizing the separation of produced acids, and favoring the simplification of system flow and reduction of system energy consumption in the sulfur-iodine cycle for hydrogen production. Intensive study of the electrochemical Bunsen reaction kinetics and the characteristics of flow, mass transfer, and reaction inside the cell, is favorable for guiding the design and optimization of cell structure, and realizing the scale-up application of the electrochemical Bunsen reaction. In this work, the research methods and contents include: explore the generating performance of hyper-azeotropic HI solution for the electrochemical Bunsen reaction using basic tests, and then propose the optimum operating condition range for generating hyper-azeotropic HI solution with low-energy consumption, so as to provide support data for the following theoretical research; establish the electrochemical Bunsen reaction kinetic model and clarify the reaction kinetic mechanism based on the electrochemical workstation measuring method; on this basis, establish the mathematical mechanism model of flow, mass transfer, and reaction process inside the cell, and then illuminate the characteristics of flow, mass transfer, and reaction using the numerical simulation, and clarify their effects on cell performance. The project intends to make breakthrough in the key scientific issues of the electrochemical Bunsen reaction based on the experimental exploration, theoretical analysis, and computing simulation, so as to provide theoretical support for the application of the electrochemical Bunsen reaction in the sulfur-iodine cycle, and even contribute to achieving the ultimate goal of large-scale, high-efficient, and low-cost sulfur-iodine cycle for hydrogen production in the future.

电化学Bunsen反应既可减少过量碘，又能实现酸分离，有利于简化硫碘循环制氢系统流程并降低系统能耗。深入开展电化学Bunsen反应动力学和电池内部流动、传质与反应过程特性的研究，可指导电池结构的设计优化，实现电化学Bunsen反应的规模化应用。本研究拟通过电化学Bunsen反应的基础实验探索超恒沸HI溶液生成特性，并提出低能耗生成超恒沸HI溶液的最优工况范围，为后续理论研究提供支撑数据；结合电化学工作站测量方法构建电化学Bunsen反应动力学模型并解析动力学机理；在此基础上，通过电池内部流动、传质与反应过程的数学机理模型建立和数值模拟，揭示流动、传质与反应特性，并阐明其对电池性能的影响。本研究力求结合实验探索、理论分析和计算模拟等手段在电化学Bunsen反应的关键科学问题上取得突破，为其在硫碘循环中的应用提供理论支撑，将有助于硫碘循环大规模高效低成本制备氢气这一终极目标的实现。

为解决电化学Bunsen反应动力学机理及电解池内流动、传质与反应特性这两个关键科学问题，推进电化学Bunsen反应在硫碘循环中的应用，克服当前硫碘循环系统流程复杂且能耗较高的难题。本项目首先研究了电化学Bunsen反应超恒沸HI溶液生成特性，通过基础实验探讨了两极溶液组分浓度在电解过程中的变化规律，考察入口流速和电流密度对物质转化和能耗的影响，提出了0.2m/s、25℃、5A/dm2、初始H2SO4质量浓度30%、HI质量浓度55%为获得高浓度H2SO4和HI，尤其是超恒沸HI溶液的最佳工况条件。其次研究了电化学Bunsen反应动力学，基于电化学工作站测定了电化学Bunsen反应电极电流-电压特性，并应用Tafel法计算电极反应的交换电流密度、Tafel斜率、不对称因子、活化能和指前因子等动力学参数，解析了电化学Bunsen反应动力学规律，发现提高温度可增加电荷传递速率，而初始SO2浓度为1.509mol/L和I2/HI摩尔比为0.5时可以获得电极高反应速率。在实验基础上，对电解池内部流动、传质与反应过程的特性进行了数值研究，开发了电化学Bunsen反应二维、稳态、层流和恒温数学模型，揭示了电解池流道内物质转化特性和反应速率变化机制，提高电流密度、温度或流速有利于加快反应，但温度或流速提高会减少物质转化，电流密度或流速增大会增加耗电量。进一步考虑流道结构的影响，设计了多种流道结构并建立了电化学Bunsen反应二维/三维物理和数学模型，揭示了流场、电场和浓度场等多物理场分布规律，提出采用单蛇形流道的电解池且控制初始硫酸浓度在40wt%左右，可以使电化学Bunsen反应获得最佳的流动和反应性能以及较低能耗。最后将电化学Bunsen反应引入硫碘循环，设计了新型硫碘循环制氢流程，通过物理和数学建模并结合化工流程模拟，分析了各单元物质和能量平衡，采用能量梯级利用原则进行系统内部热量交换，提高了能量利用效率，热效率达到42-50%。本研究为电化学Bunsen反应的优化和应用提供实验和理论依据，将有助于硫碘循环制氢大规模、可再生和高效制氢的实现。