基于修饰铁矿石载氧体的煤催化燃烧

Chemical looping combustion (CLC) of coal is a novel technology that can be used to meet the demand on energy production, leading it to be a promising way of combustion. In the process of using CLC technology for coal, the coal gasification process is expected to be the slower step in the fuel reactor as compared to the reduction reaction of oxygen carriers, therefore resulting in a low CO2 capture efficiency. Thus, the response involving the controlling and coupling reactions in the processes of coal gasification and oxygen carrier reduction, has become to be one of the key technology in the CLC of coal. Due to abundant reserves and low cost, iron ore as oxygen carrier has been developed to replace the synthetic oxygen carriers, leading it to be an attractive and suitable material for the future CLC application of coal. Therefore, it is especially significant to carry out the research and investigation on the adaption of coal CLC process with iron ore as oxygen carrier. In this project, the iron ore will be directly decorated with catalysts to accelerate the coal gasification rate. The carbon conversion efficiency should be improved for the efficient use of coal in CLC process. In traditional coal catalytic gasification process, to obtain good catalytic activity in the steam gasification of coal, catalyst must be atomically dispersed throughout the coal or coal char, which is not the case in the CLC process. Thus, in this project, the catalytic gasification reaction mechanism between the decorating iron ore oxygen carrier particles and coal particles will be revealed, at which the catalysts aren't atomically dispersed throughout the coal or coal char particles. Also, the coupling reaction mechanism between the coal catalytic gasification products and oxygen carriers, the transfer process of coal gasification products in the subtle channels of oxygen carriers, the regular patterns involving weight transfer, heat transfer and momentum transfer in the multiphase flow and multiphase complex chemical reaction system will be obtained. Furthermore, the mechanism of collaborative control of pollutants in coal/coal char conversion will be investigated.

煤化学链燃烧是一个基于零排放理念的先进发展方向，具有很好应用前景的燃烧方式。在煤化学链燃烧过程中，与载氧体的还原反应相比，煤气化反应速率缓慢，导致CO2捕集效率差；因此，燃料反应器内煤气化和载氧体还原反应之间的调控与耦合成为煤化学链燃烧的技术关键之一。铁矿石储量丰富、价格低廉，使得它极有可能取代人工制备的载氧体，成为未来煤化学链燃烧的主流载氧体，研究开发铁矿石载氧体对煤化学链燃烧技术尤为重要。本项目直接对铁矿石载氧体进行催化修饰，催化煤化学链燃烧过程中煤气化反应速率，提高煤化学链燃烧过程中碳转化率，实现煤炭高效利用。揭示在煤化学链催化燃烧过程中，催化剂不与以原子形式附着在煤颗粒条件下煤/煤焦催化气化反应机理；获得煤催化气化产物与载氧体之间的耦合反应机理，载氧体细微通道内传递过程和化学反应机理、多相流动与多相复杂化学反应体系中质量、热量和动量传递理论和相互作用规律，污染物协同控制机理。

煤化学链燃烧（CLC）是一种新型的燃烧方式，其通过不同品位能的梯级利用，具有比传统燃烧方式更高的能源利用效率，而且将新型能源转换与CO2富集、污染物脱除过程有机结合起来。铁矿石储量丰富、价格低廉，成为未来煤化学链燃烧的主流载氧体，研究开发铁矿石载氧体对煤化学链燃烧技术尤为重要。但是，天然铁矿石作为载氧体存在化学反应活性较低，载氧率较小等缺点，有必要对其进行提质处理。碱金属和碱土金属（Na、K、Ca）和过渡金属（Fe、Co、Ni）是煤催化气化的催化剂。因此，本项目以廉价铁矿石为载氧体，采用修饰铁矿石的方法提高铁矿石载氧体对应的煤气化反应速率，以打破基于铁矿石载氧体化学链燃烧系统的整体效率偏低的瓶颈。基于铁矿石修饰的煤化学链催化燃烧包含两个方法，其一：通过向基于铁矿石载氧体的煤化学链燃烧过程中机械混合含有催化活性的催化剂，如：Ni基催化剂，石灰石，CaO等；其二：将含有催化活性的碱金属，碱土金属等负载于铁矿石表面，在此过程中，煤催化气化反应催化剂修饰的载体由传统的煤转变为铁矿石，负载催化活性的铁矿石参与化学链燃烧过程。鉴于CaO是良好的煤气化催化剂和脱硫剂，添加CaO对铁矿石进行修饰，并利用小型流化床反应器以及1 kWth串行流化床反应器进行了煤化学链燃烧试验。与铁矿石相比，采用水泥/CaO-铁矿石能有效提高燃料反应器中的碳转化率及煤气化产物向CO2和H2O的转化率，且在高温运行过程中，载氧体颗粒表面没有发生烧结现象。将含K和Na等碱金属通过浸渍的方法负载与铁矿石表面，利用流化床反应器进行煤化学链燃烧实验。与铁矿石相比，采用K和Na修饰铁矿石均能有效提高可燃气体的转化率，但在高温（高于950℃）情况下，Na修饰铁矿石会产生烧结现象。总之，采用碱金属和碱土金属（K、Na、Ca）对铁矿石进行修饰，可显著提高载氧体的反应活性。