【作者】 韩涛；

【导师】 金红光； 洪慧；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2012， 博士

【摘要】 传统解决能源利用与环境污染之间矛盾的思路往往局限于“先污染,后治理”的链式思路,即化石燃料燃料采用简单的直接燃烧方式转换成热能,然后再组织热力循环实现热转功。对于化石燃料燃烧产生的污染物则采用基本独立于热转功过程之外的化工分离过程进行处理。由于化石燃料在能源系统中转化利用后所排放的C02浓度很低,而且CO2的处理量大,导致CO2减排能耗过高,减排成本居高不下。本论文围绕多能源互补回收CO2的化学链燃烧,以太阳能与燃料化学能综合梯级利用为突破口,将中温太阳能热化学过程与化学链燃烧过程相结合,从太阳能驱动化石燃料转化与CO2产生源头着手,实现中温太阳能高效热发电和动力系统中C02零能耗捕集。本文从太阳能与化石燃料互补回收CO2的化学链燃烧机理研究、实验验证和新型氧载体的制备与系统集成三个方面开展了相关工作。在燃料化学能梯级利用与CO2分离一体化理论的基础上,建立了燃料转化过程Gibbs自由能变化、燃料化学能梯级利用程度和CO2浓度富集度的关联式,探索了化学链燃烧过程的能量释放机理；通过与燃烧前分离CO2的能量释放过程的对比,指出化学链燃烧过程具有燃料化学能梯级利用与CO2零能耗捕集的一体化特征。探讨了中温太阳能热化学过程与化学链燃烧过程的耦合作用机制,阐明了化学链燃烧过程对中温太阳能集热品位的内在提升作用,揭示了太阳能与化石能源互补回收CO2的综合效应。对化学链燃烧过程进行了相关实验研究,采用溶解法制备了基于Fe、Ni、Co的不同氧载体材料,分析比较了各氧载体的反应性能,分析了反应温度、反应气组分、氧载体粒径等关键参数对CoO/CoAl2O4氧载体反应性能的影响,研究了反应气加湿对积碳的抑制作用以及氧载体的循环再生能力,拓展了化学链燃烧在替代燃料和新能源领域中的利用。为进一步提高氧载体的反应速率,缩短反应时间,通过考察不同助剂对氧载体反应性能的影响,研究制备了一种中温条件下具有高还原反应性能的新型氧载体材料(CoO+PtO21.0%)/CoAl2O4。研究结果表明,新材料与DME还原反应过程的表观活化能为85kJ/mol,相比CoO/CoAl2O4材料降低了43kJ/mol,还原反应速率相应地提高了近4倍之多,通过对助剂含量对氧载体反应特性影响的研究发现,(CoO+PtO2)/CoAl2O4氧载体中助剂PtO2的理想含量应为1.0%,新材料与DME还原反应的最佳加湿比为H2O/DME=1.0,低于CoO/CoAl2O4还原反应过程的加湿比(H2O/DME=2.0)。基于中低温太阳能和燃料化学能综合互补利用的原则,提出了一种利用中低温太阳热能驱动甲醇化学链燃烧动力系统,探讨了燃料化学能与物理能综合梯级利用的多能源互补动力系统的集成机制,揭示了中低温太阳能集热品位提升和热转功效率提高的本质,分析了新系统特性规律和关键参数对循环性能的影响。本论文的研究上作为从多能源互补综合梯级利用和新型燃烧方式耦合的角度实现低能耗回收CO2提供了理论和实验支撑。更多还原

【Abstract】 The traditional solution for the problem of energy utilization and environmental pollution often follows the way of’treatment after pollution’, where the chemical energy of the fossil fuel is converted into thermal energy through direct combustion with air to drive the thermal cycle, and the produced pollutants are treated with chemical separation method independent of the energy conversion process. This direct combustion of fossil fuel causes CO2diluted by N2, resulting in a large amount of flue gas to be treated, and leading to the increase in the energy penalty and the cost for CO2reduction.This dissertation focuses on the research of CO2control with multi-energy input, and originally integrates the mid-temperature solar thermochemical process with the chemical-looping combustion (CLC) to simultaneously achieve a high net solar-to-electric efficiency and zero energy penalty for CO2separation in the power cycle. The research work was carried out from three aspects including the mechanism study, the experimental validation and the system integration.Based on the principle of the chemical energy cascade utilization integrated CO2capture, the correlationship among the Gibbs free energy change△G, the degree of chemical energy cascade utilization k and the relative enrichment of CO2concentration λ was built, and the mechanism of fuel chemical energy release in CLC was explored. By comparing with the energy conversion process with CO2separation before combustion, it was proved that the CLC process can realize the cascade utilization of fuel chemical energy integrated CO2separation with minus energy penalty. The coupling of mid-temperature solar thermal chemical process and CLC was also explored, a phenomenon of the upgrade of the energy level of the mid-temperature solar thermal energy was found, and the synthetic effect of CO2control with hybridization of solar thermal energy and fossil fuel was revealed. Experiments on the CLC process were carried out on the TGA reactor. Oxygen carriers, with Fe2O3, NiO, and CoO as solid reactants and Al2O3, MgAl2O4, and YSZ as binders, were prepared by dissolution method. The reactivity of the oxygen carriers was compared, and the effects of the reaction temperature, the gas composition and the particle size were studied. Carbon deposition in the reduction process of DME with CoO/CoAl2O4was completely suppressed by adding water vapor to the gaseous reactant, and the optimal value of H2O/DEM is around2.0. These research findings validate the feasibility of the integration of mid-temperature solar thermochemical process and CLC, and bring the CLC technology into utilization of renewable energy and alternative fuel for CO2mitigation.The effects of different additives on the reactivity of the oxygen carrier CoO/CoAl2O4were studied, and a new kind of oxygen carrier (CoO+1.0%PtO2)CoAl2O4was developed. Compared with CoO/CoAl2O4, the activation energy of the reduction of (CoO+1.0%PtO2)/CoAl2O4with DME was lowered by about43kJ/mol, and the reaction rate was dramatically improved by about4times. The effect of PtO2content on reactivity showed that the suitable PtO2content was1.0%. By adding water vapor into the fuel reactor, carbon deposition was completely avoided, and the appropriate mole ratio of H2O/DEM was around1.0. This value was lower than that of CoO/CoAl2O4, which can significantly reduce the water consumption, as well as the energy consumption of the CLC process.Based on the synthetic utization of the solar thermal energy and the chemical energy of fossil fuel, a new solar-hybrid thermal cycle, integrating CLC with mid-and-low temperature solar thermal energy has been proposed. The thermodynamic performance of the proposed cycle was evaluated, the characteristics were identified with the aid of graphical exergy methodology, and the effects of the key parameters on the system performance were analysed. The results showed that, the exergy efficiency of the proposed solar thermal cycle would be expected to be58.4%at a turbine inlet temperature (TIT) of1673K, and the net solar-to-electric efficiency can reach as high as30.1%. The promising results obtained here indicate that this solar-hybrid combined cycle not only offers a new approach for highly efficient use of middle-and-low temperature solar thermal energy to generate electricity, but also provides the possibility of simultaneously utilizing renewable energy and alternative fuel for CO2capture with low energy penalty. The research work of this dissertation offers both theoretical and experimental support for CO2control with the synthetic cascade utilization of multi-energy.更多还原