加压流化床内介尺度颗粒聚团和气泡的研究

Abstract: Fluidized bed technology is an effective way in gasification of high-ash-fusion coal, increase of the operating pressure and obtaining ideal coal gasification efficiency per furnace is the key issue to be solved of this technology at present. This project takes the motion and transfer of particle clusters and bubbles in meso-scale as the research objects, combining with the optical fiber probe and high speed camera technologies, studies the effect of pressure on the particle concentration in clusters, cluster size, cluster velocity as well as temporal and spatial distributions of clusters in pressurized fast fluidized bed, and establishes quantitative correlations between particle clusters and local macro parameters. In the pressurized bubbling fluidized bed, adopts the particles with wide diameter distributions as the fluidizing materials, studies the formation and evolution rules of meso-scale bubbles under different pressure,establishes multi-scale cluster drag model and bubble drag model to suit for the pressuring process by considering the pressure and added mass force effect,simulates gas-solid flow hydrodynamics in pressurized fast fluidized bed and bubbling fluidized bed. Combining with the heat and mass transfer models, studies the evolution rules of meso-scale particle clusters and bubbles under the dual effects of pressure and reactions in pressurized fluidized bed. On the basis of experimental and simulated studies, this project aims to obtain the directional control mechanism of pressure and operating conditions upon the formation,evolution and distribution of particle clusters and bubbles, to provide theoretical basis for the operation,scaling and optimization of pressurized fluidized bed.

流化床技术是一种解决高灰熔点煤气化的有效途径，提高操作压力继而获得理想的单炉煤处理量是目前该技术亟待解决的关键问题。本项目以加压下流化床内介尺度颗粒聚团和气泡为研究对象，采用光纤探针和高速摄像相结合的方式，在快速床上研究压力对颗粒聚团内部浓度、尺寸、速度以及时空分率沿轴向和径向分布规律的影响，并建立颗粒聚团与当地流动参数的定量关系；用宽粒径分布颗粒组成鼓泡床床料，研究不同压力下介尺度气泡的形成、演变和分布规律；考虑压力和附加质量力的影响，建立适用于加压过程的多尺度曳力计算模型，并模拟加压快速床和鼓泡床内的气固流动特性。结合已有的多尺度气固传热传质和反应模型，模拟研究加压流化床内压力和反应共作用下介尺度颗粒聚团和气泡的变化规律。在实验和模拟研究基础之上，获得压力和操作条件对介尺度聚团和气泡（形成、演变及分布）的定向调控和控制机理。为加压流化床的运行、放大和优化等提供理论依据。

煤炭气化是煤炭清洁高效利用的核心和龙头技术，开发大型加压流化床气化技术，并满足未来大规模气化的需求，对我国能源利用结构调整具有重要的战略意义。本项目通过实验和模拟相结合的手段，研究了加压下介尺度聚团和气泡（形成、演变及分布）的定向调控和控制机制。首先，在所搭建的加压流化床实验平台上测量了压力对基础流化特性、介尺度颗粒聚团的运动演化、介尺度气泡的运动演化的影响和调节机理；其次，针对介尺度颗粒聚团并考虑压力和附加质量力的影响，建立了基于颗粒聚团的加压Cluster-based EMMS/PFB模型；再次，结合实验测量的气泡拟合关联式和多尺度能量最小化原理，考虑压力对介尺度气泡的影响，建立了基于气泡的加压Bubble-based EMMS/PFB模型；最后，采用所建模型对加压多段分级转化流化床气化炉进行模拟计算，预测了多段床下段鼓泡床和上段快速床的气固流体动力学特性。通过本项目的研究结果，可为加压大型流化床的运行、放大和优化等提供理论参考。