能量消耗机制对卧式循环床内颗粒聚团特性的影响

Horizontal circulating fluidized bed (HCFB) is regarded as a promising technology that offers an alternative solution to small capacity industrial boilers burning low grade solid fuels. Since HCFB is operated under fast fluidization, it is required to understand the particle clusters characteristics for the device design and operation. Unfortunately, existing drag models fail to describe the particle cluster characteristics. Therefore, based on the energy-minimization multi-scale (EMMS) theory, our objective is to investigate the effect of dominate energy consumption mechanisms on the cluster size, cluster concentration, etc. Two types of energy consumption mechanisms: energy consumption for suspending and transporting with respect to unit mass of particles Nst, energy consumption due to inelastic collisions between particles Nd will be calculated by using computational fluid dynamic combined with discrete element method (CFD-DEM). Material balance, operation conditions and particle physical properties are three key factors that dominate the share of each energy consumption mechanism on total. By taking account the influence of operation condition, classification efficiency of two-stage separation and comminution of solid material, we will propose a particle population balance model to describe the material balance in the HCFB device. Eventually, a meso-scale drag model for two fluid method (TFM) will be established based on a stability criteria that involves minimization of two types of energy consumption mechanisms. Outcome of this research and extension of meso-scale theory will increase the accuracy of gas-solid flow simulation in the HCFB device featured with multi-pass and two-stage separation. All in all, this research will help to improve, extend and advance the fundamental meso-scale theory application in the industrial area.

卧式循环床（HCFB）在中小型燃劣质固体燃料的工业锅炉领域具有良好的应用前景，掌握装置内颗粒聚团特性的控制机制是设计和运行的基础。针对现有曳力模型未能准确描述颗粒聚团特性的问题，本课题在能量最小多尺度（EMMS）理论基础上，采用计算流体力学与离散单元法（CFD-DEM）研究悬浮输送能耗Nst和颗粒非弹性碰撞及摩擦能耗Nd两种能量消耗机制的相互作用对颗粒聚团的尺寸、颗粒浓度等特性的影响规律。物料平衡特性、操作条件、物料颗粒物性等是影响两种能量消耗机制占总能量消耗份额的主要因素。通过理论与实验相结合，研究操作条件、两级分离的分级分离效率和物料颗粒磨耗特性等因素对物料平衡特性的影响规律，并构建颗粒群平衡模型。并以能量消耗机制的稳定性为判据，建立适用于双流体模型（TFM）的介尺度颗粒聚团曳力模型。研究成果可提高HCFB这类多流程、两级分离的装置气固流动模拟的准确性，并推进介尺度理论的发展和完善。

为了应对世界范围内的能源危机和环境污染问题，必须采取可靠的技术措施节能减排或者寻找可再生能源，例如，开发节能高效燃烧设备、开发可再生能源利用技术等。本课题主要研究燃劣质固体燃料的卧式循环床（HCFB）锅炉，研究床内的气固流动特性，特别是掌握床内的颗粒聚团特性的控制机制，为设计清洁高效的卧式循环流化床燃烧技术提供理论基础。.卧式循环床（HCFB）燃尽室和副燃室内沿重力方向的稀相气固流动能自发形成颗粒聚团局部非均匀结构。从实验、理论和数值模拟三个方面研究了颗粒聚团对气固脉动特性的影响规律。建立了气固气固逆流床模拟实验装置，采用相位多普勒激光测速仪(PDA)测量气固逆流床槽道内颗粒相速度分布。针对颗粒相随机脉动速度分布呈各向异性的特点，以颗粒动理学方程为基础，发展了二阶矩方法。以OpenFOAM®为平台，采用分辨率为Δx = 1:75dp 的网格和Stokes 曳力模型，模拟三维周期条件下颗粒相平均体积分数为0.01 的稀相气固流动。以颗粒相非均匀程度为参数，建立了漂移速度代数模型。.通过实验、工程实践和理论分析，具体掌握了操作条件、两级分离的分级分离效率和物料颗粒磨耗特性等因素对卧式循环流化床物料平衡特性的影响规律，并用数值模拟方法对卧式循环流化床锅炉进行了模拟。.上述研究成果为能量最小多尺度（EMMS）理论应用到卧式循环流化床锅炉（HCFB）奠定了基础，促进了介尺度理论的发展和应用。.另外，在可再生能源（生物质和废弃轮胎等）气化方面，进行了生物质高温气化制氢、生物质低温催化重整制氢、废弃轮胎临界水解等方面的探索。研究了水蒸气温度、流量等对气化产氢效果的影响。用组分(木质素、纤维素和半纤维素）的气化特性数据拟合了实际生物质的气化产物及产氢特性。基于合成气高、低温变换制氢工艺路线，研究了Fe-Cr高温变换与Cu-Zn低温变换催化剂对产H2的影响。.共发表SCI源刊论文6篇，EI收录论文1篇（不包括可同时被SCI收录的论文），申请发明专利1项。培养博士生3人、硕士生4人、博士后1人。在本研究理论的指导下，清洁高效多流程循环流化床燃烧获得中国节能协会技术发明一等奖。