烧结矿余热回收竖罐内气固动量传输机理及颗粒运动规律研究

The vertical tank recovery process is a revolutionary waste heat recovery process proposed by the applicant's team. The power generation per ton of sinter is expected to double though replacing traditional waste heat recovery process by vertical tank. However, the unsmooth movement of sinter and uneven distribution of air flow in the tank are the bottleneck problems in the current engineering implementation. The key scientific issue are the gas-solid momentum transmission mechanism and particle movement law of the large particle in vertical moving bed. Moreover, the contact force of particle-particle and particle-wall are complicated due to factors such as wide particle size distribution and complex shape, etc. However, the relevant research is still blank until now. In this research, based on the requirements of experimental and numerical calculation methods, the cross-scale Euler-Lagrange method is adopted to study the momentum transmission mechanism of gas-solid and the movement process of sinter particles. The main innovational findings are: 1) a novel test scheme of the basic mechanics and thermodynamic parameters of sinter is designed; 2) a revised drag force model and a coupled CFD-DEM model and simulation scheme are constructed to realize gas-solid momentum transmission by using Lagrange method based on particle level to describe particle motion and Euler method based on macroscopic level to describe gas flow in vertical tank; 3) a visual experimental platform and experimental verification method are developed for validation of the simulation results.

竖罐式回收工艺是申请者所在团队提出的一项变革性余热回收工艺，其吨矿发电量有望翻倍，目前处于工程化实施初步阶段。烧结矿在罐体内运动不畅以及气流分布不均是目前工程化实施的瓶颈问题，其关键科学问题是大颗粒竖式移动床层气固两相动量传输机理及颗粒运动规律，迄今相关研究尚属空白。本研究针对烧结矿粒径分布广、形状复杂等因素导致气固两相受力复杂等难点，基于实验和数值计算方法构建的需求，采用跨尺度的Euler-Lagrange方法研究气固两相动量传输机理，进而研究烧结矿运动规律。主要工作及创新：1）获得烧结矿力学和热学基础数据测试方法；2）采用基于颗粒层面的Lagrange方法研究颗粒运动，采用基于宏观层面的Euler方法研究气体流动，修订曳力模型，构建曳力耦合的CFD-DEM模型实现气固两相动量传输耦合；3）研制可视化实验平台，提出气固动量传输和颗粒运动模拟结果的实验验证方法。

“竖罐式冷却回收烧结矿显热”是申请人所在团队2008年提出的烧结过程余热资源高效回收利用的一项新技术，该工艺核心目标是在对烧结矿冷却时实现烧结矿显热的高效回收，同时规避了环冷、带冷等传统冷却工艺密封困难、扬尘、散热损失严重等缺点。.为此，本项目从工程背后的科学问题出发，采用可视化实验与CFD-DEM模拟计算相结合的方法，研究烧结矿颗粒在竖罐内的运动规律及其对气流分布规律的影响，从而研究竖罐结构参数和操作参数对烧结矿颗粒运动规律和气流分布规律的影响，进而给出满足烧结矿顺行以及气流分布均匀的竖罐结构参数和操作参数。解决困扰竖罐式烧结矿余热回收技术工程化的两大瓶颈问题，为工程实践提供理论支撑。.主要结果如下：.1）10-20 mm、20-30 mm、30-40 mm、40-50 mm粒径烧结矿颗粒的密度分别为2953 kg/m³、2968 kg/m³、2999 kg/cm³、3041 kg/m³，随粒径逐渐增大；弹性模量分别为2.14 GPa、2.16 GPa、2.22 GPa、2.28 GPa，随粒径逐渐增大；颗粒间弹性恢复系数分别为0.19、0.18、0.15、0.13，随粒径增大逐渐减小；静摩擦系数分别为1.15、1.21、0.86、0.77，随粒径增大呈下降趋势；动摩擦系数分别为0.08、0.12、0.13、0.16，随粒径逐渐增大；.在余热回收过程中，运行参数和结构参数对㶲，电耗和无量纲㶲的影响也很明显。当其他参数恒定时，基于出口气体的最大㶲，冷却气体的最佳质量流量为85 kg/s。随着高度，冷却段直径和烧结矿质量流量的增加，出口气体的㶲逐渐增加。增加冷却气体的质量流量，冷却段的高度和烧结矿的质量流量会导致冷却风扇功耗的增加，而增大直径的效果却相反。