化学链燃烧作为一种新型无焰燃烧技术，可以实现低能耗捕集CO2。目前，固体燃料化学链燃烧技术正处于实验室研究到工程示范的过渡阶段，面临着系统循环流率低和设计理论不完善的问题。本文围绕实现高通量系统循环流率和建立化学链燃烧反应器系统设计理论的目标，从试验和模型两个方面进行了研究。提出了下部为湍动流化床、中部为提升管、上部为下行床的复合床燃料反应器，并采用溢流返料将物料从燃料反应器返回至空气反应器。针对提出的设计理念，搭建了1.5MWth冷态试验台。采用压力波动法测量了转变气速，探究了不同影响因素下燃料反应器自循环回路和溢流循环回路的流态化特性，并验证了经验关联式的准确性。结果表明燃料反应器自循环流率最易受到湍动流化床气速的影响，溢流循环流率最高能达到148.66kg/(m2·s)，而床料高度应高于溢流口以防其成为物料循环的限制因素。最后，建立了溢流模型来预测溢流循环流率。针对化学链燃烧需要较高系统循环流率的问题，提出了循环方式为空气反应器顶部返料与燃料反应器溢流返料耦合的化学链燃烧双流化床系统，并搭建了1.5MWth冷态试验台，实现了稳定的物料循环和合理的压力分布。针对空气反应器气速、总床料量等7个影响系统流态化特性的主要参数进行了试验研究，发现系统循环流率最高能达到66.33kg/(m2·s)，燃料反应器停留时间大于189s。根据冷态试验结果，提出了实现高通量系统循环流率的调控方法和双流化床的控制策略。建立了基于轴向固含率分布模型、压力平衡和质量平衡的化学链燃烧系统全回路流态化模型。利用冷态试验数据验证了模型固含率、压力和床料量的分布特征，结果表明基于模型计算的固含率和床料量与冷态试验结果吻合良好，系统压力计算值与试验数据也具有较好的一致性，偏差在0.01~0.2kPa之间。最后，运用模型讨论了总床料量和颗粒粒径对系统流态化特性的影响规律。在全回路流态化模型的基础上耦合质量平衡、热量平衡、反应动力学和反应器模型，建立了化学链燃烧反应器系统设计理论并编写了热力计算程序，实现了3MWth煤化学链燃烧热态示范装置的设计计算。结果表明钙钛矿、锰矿石和钛铁矿的系统循环流率分别为10.1、6.9和6.8kg/(MWth·s)，均能够维持系统的自热运行；采用钛铁矿为载氧体时系统碳捕集效率最高，达到了79.35%。该项工作为化学链燃烧热态示范装置的建立和运行奠定了基础。
As a new flameless combustion technology, chemical looping combustion (CLC) can capture CO2 with low energy penalty. Presently, solid-fuel CLC technology is in the transition stage from laboratory research to engineering demonstration, and it is faced with the problems of low solid circulation rate and imperfect design theory. In order to achieve the high solid circulation rate and obtain the CLC design theory, the experimental and modeling study was used for CLC unit in this paper.A compound bed fuel reactor (FR) with turbulent fluidized bed (TFB) at the bottom, riser at the middle and downer reactor at the top was designed, and the overflow return from fuel reactor to air reactor (AR) was proposed. According to the developed design concept, a 1.5MWth cold flow model was designed and built. The pressure fluctuation method was used to measure the transition velocity. The fluidization characteristics and overflow characteristics of the FR were investigated, and the accuracy of empirical correlation was verified by using the experimental data. The results showed that the FR solid circulation rate was most easily affected by the TFB gas velocity. The maximum solid circulation rate could reach 148.66kg/(m2·s), and the bed material height in the TFB should be higher than the overflow port to prevent it from becoming a constraint factor on the solid circulation. Additionally, an overflow model was established to predict the solid circulation rate.In order to solve the problem that the CLC unit requires a high solid circulation rate, the dual fluidized bed CLC unit with AR top return and FR overflow return was proposed, and a 1.5MWth cold flow model was built. Stable solid circulation with a reasonable pressure profile was realized in the 1.5MWth cold flow model. The effect of seven vital parameters on the fluidization characteristics were studied. It was found that the maximum solid circulation rate could approach 66.33kg/(m2·s) and the FR residence time was higher than 189s. Based on the experimental results, the control method of high solid circulation rate and the control strategy of the dual fluidized bed were proposed.Based on the axial solid fraction profile model, pressure balance and mass balance, the whole loop fluidization model of the CLC unit was established. The distribution characteristics of the solid fraction, pressure and bed inventory were verified by using the experimental data. The results showed that the solid fraction and bed inventory calculated by the fluidization model were in good agreement with the experimental data. The calculated pressure values were also in consistent with the experimental data, and the deviation was normally between 0.01 and 0.2k Pa. Finally, the effects of total bed inventory and particle size on the fluidization characteristics were discussed by using the fluidization model.Based on the developed fluidization model, coupled with mass balance, heat balance, reaction kinetics and reactor model, the CLC design theory was proposed and the thermodynamic calculation program was compiled. A coal-fired CLC unit with thermal input of 3MWth was designed by using the developed thermodynamic calculation program. The results showed that the solid circulation rates of perovskite, manganese ore, and ilmenite were 10.1, 6.9, and 6.8kg/(MWth·s), respectively, and the auto-thermal operation of the CLC unit could be achieved. When ilmenite was used as the oxygen carrier, the carbon capture efficiency was the highest and the value reached 79.35%. This work lays a foundation for the construction and operation of 3MWth coal-fired CLC demonstration unit.
