基于四流化床煤/生物质共水蒸气气化的清洁发电系统研究

A novel coal/biomass based clean power generation system is proposed in this work. The methodologies including process modeling, numerical simulation and experimental research are adopted, and the characteristics of the integrated system and the gasification units in the system are investigated in depth. With respect to the process modeling, the thermodynamic model for the entire system is built, and the kinetic model for the gasification units is set up. The property of the quadruple fluidized bed (QFB) gasifier composed of a bubbling fluidized bed (BFB) gasifier, a circulating fluidized bed (CFB) calciner, a CFB oxidation reactor and a BFB reduction reactor is studied. The effects of key operating conditions on the system energy efficiency, exergy efficiency, CO2 sequestration rate and the speciation of the major pollutants are also detected. With respect to the numerical simulation, a solver capable of addressing the dense phase particulate flow, the turbulent flow, the turbulence-reaction interaction, the particle surface reaction, the inter-phase heat and mass transfer and the radiation heat transfer is built based on the multiphase particle in cell (MP-PIC) approach. Then, numerical simulations are implemented for the quadruple fluidized bed gasifier, which helps the design and optimization of the QFB reactors. To calculate the radiation heat transfer more accurately in the numerical simulations, a method which can properly predict the effective absorption coefficients in a wide range of pressures and temperatures for gas mixtures containing multiple radiative species is also proposed. With respect to experiments, a cold-state QFB testbed is built, and the coupling properties of the four fluidized bed reactors and the particulate flow hydrodynamics in them are further studied.

本课题提出一种新型煤/生物质双燃料基清洁发电系统，采用流程仿真、数值模拟和实验研究相结合的方法，对系统整体运行特性及其中气化环节进行深入探析。在流程仿真方面，建立全系统热力学模型和气化环节动力学模型，深入研究系统内由气化炉、煅烧炉、氧化炉和还原炉构成的四流化床反应器的耦合运行方式，并研究不同关键参数对系统能量效率、㶲效率、CO2捕集率及其他污染物形态演化的影响。在数值模拟方面，基于多相流质点网格法建立耦合浓相颗粒流动、气相湍流流动、湍流-化学反应、颗粒表面反应、气固传热传质以及辐射传热等过程的求解器，对四流化床反应器进行数值模拟，为反应器设计和优化提供参考。为数值计算需要，还提出一种能在较宽压力和温度范围下对包含多种辐射吸收性组分混合气的有效辐射吸收系数进行预测的方法。在实验方面，建立四流化床反应器耦合运行冷态实验台，进一步研究四个流化床的耦合运行特性及反应器内颗粒流动动力学特性。

本课题提出一种新型煤/生物质双燃料基清洁发电系统，采用理论研究、流程仿真、数值模拟和实验研究相结合的方法，对系统整体运行特性及其中气化环节进行深入探析。在理论研究方面，建立了煤-生物质共气化动力学模型，该模型考虑了共气化协同效应、颗粒内扩散以及颗粒外层剥落对气化速率的影响。在流程仿真方面，首先，基于本课题所建立的煤-生物质共气化动力学模型，并耦合流化床内流体动力学一维模型，建立了双流化床气化炉内煤-生物质共气化一维动力学模型，利用该模型对双流化床共气化特性进行了分析。随后，结合Aspen Plus和本课题所建立模型，建立了完整的四流化床反应器模型，并利用该模型对四流化床气化炉的运行特性进行了一系列预测。在数值模拟方面，基于多相流质点网格法建立耦合浓相颗粒流动、气相湍流流动、湍流-化学反应、颗粒表面反应、气固传热传质以及辐射传热等过程的求解器，对四流化床反应器进行数值模拟，为反应器设计和优化提供参考。为数值计算需要，还提出一种能在较宽压力和温度范围下对包含多种辐射吸收性组分混合气的有效辐射吸收系数进行预测的方法。在实验方面，建立四流化床反应器耦合运行冷态实验台，利用所搭建的冷态四流化床反应器对不同空塔速度、床料量等情况下流化床内部流体动力学进行了详细研究，绘制了四流化床内部循环压力回路。