基于选择性膜分离的太阳能热化学系统研究

发布时间：2018-09-06 07:17

【摘要】：环境污染及化石能源的有限储量,使得寻找无污染、可再生的清洁能源成为日益紧迫的任务。太阳能以其储量丰富、环境友好等特点有望成为化石能源的理想替代能源。但太阳能能量密度较低,不稳定等问题成为目前制约太阳能快速发展的瓶颈。因此,将太阳能转化为氢能等容易储存、能量密度高、清洁环保的二次能源成为能源领域研究的热点之一。基于选择性膜分离的太阳能热化学方法通过选择性地分离产物,促使反应向正向进行,提高反应物转化率并降低太阳能燃料的制取温度。本学位论文依托国家自然科学基金、国家重点研发计划等科研课题,基于能的品位概念,探索太阳能到化学能的低温高效转换方法。对基于选择性膜分离的太阳能热化学利用过程的转化机理、能量品位提升规律以及能量效率趋势进行综合研究,并进行实验验证。本文的主要内容及结论如下:(一)针对选择性膜分离的高温太阳能热化学分解水或二氧化碳制取氢气或一氧化碳过程进行热力学分析和模拟研究。提出基于真空泵辅助的透氧膜反应器系统和基于甲烷辅助的透氧膜反应器系统的能量效率变化趋势,其中基于真空泵辅助的透氧膜反应器系统能量利用效率为2.9%;基于甲烷辅助的透氧膜反应器系统太阳能至化学能转换效率可达63%。该部分理论分析为基于选择性膜分离的高温太阳能热化学实际应用奠定理论基础。(二)对上述传统膜反应器进行改进,提出交替式透氢膜透氧膜反应器,可以在较低温度下大幅提高太阳能热化学分解水的转化率和能量利用效率,例如在1500℃时,水蒸气转化率从"等温法"热化学循环的1.26%提升至99.99%,太阳能至化学能转换效率从2.9%提升至42.6%。新型等温交替透氢透氧系统为太阳能分解水制氢的应用提供有价值的研究和应用方向。(三)针对太阳能分解水温度高、聚光成本高的缺点,将传统甲烷重整反应与选择性膜分离结合,提出基于透氢膜和透二氧化碳膜的新型中低温太阳能甲烷重整系统。系统可以在300-400℃实现甲烷的完全转化(工业甲烷重整反应需要在800-1000℃才能达到甲烷的完全转化),大幅度提高能量利用效率,并可能带来太阳能燃料成本的显著降低。最后,从催化剂制备、反应器设计、实验台搭建、系统流程设计等方面对该模型进行实验研究。实验结果表明,通过交替填充催化剂和氢氧化钙模拟交替分离氢气和二氧化碳的甲烷重整实验在400℃时具有88.02%的甲烷转化率。实验验证本文提出模型的可行性,为未来甲烷重整和槽式太阳能集热器结合奠定基础。
[Abstract]:Environmental pollution and the limited reserves of fossil energy make it an increasingly urgent task to find clean and renewable energy sources without pollution. Solar energy is expected to be an ideal alternative to fossil energy because of its rich reserves and environmental friendliness. However, the low energy density and instability of solar energy become the bottleneck of solar energy development. Therefore, converting solar energy into hydrogen energy, such as easy storage, high energy density, clean and environmentally friendly secondary energy has become one of the research hot spots in the field of energy. The solar thermochemical method based on selective membrane separation promotes the reaction forward by selectively separating the products, increases the conversion of the reactants and lowers the preparation temperature of solar fuel. This dissertation is based on the National Natural Science Foundation and the National key R & D projects. Based on the concept of energy grade, this thesis explores the low-temperature and high-efficiency conversion method from solar energy to chemical energy. The conversion mechanism, energy grade enhancement law and energy efficiency trend of solar thermochemical utilization process based on selective membrane separation were studied and verified by experiments. The main contents and conclusions of this paper are as follows: (1) Thermodynamic analysis and simulation study on the thermochemical decomposition of water or the production of hydrogen or carbon monoxide from high temperature solar energy by selective membrane separation is carried out. The energy efficiency change trend of oxygen permeable membrane reactor system based on vacuum pump and methane assisted oxygen permeable membrane reactor system is presented. The energy utilization efficiency of the oxygen-permeable membrane reactor system based on vacuum pump is 2.9, and the conversion efficiency from solar energy to chemical energy of the oxygen-permeable membrane reactor system based on methane is 63. The theoretical analysis provides a theoretical basis for the practical application of high temperature solar thermochemistry based on selective membrane separation. (2) to improve the traditional membrane reactor mentioned above, an alternative hydrogen permeable membrane reactor is proposed, which can greatly improve the conversion rate and energy utilization efficiency of solar thermochemical decomposition water at low temperature, for example, at 1500 鈩，

本文编号：2225643