【作者】 卢海波；

【导师】 陈作炳；

【作者基本信息】 武汉理工大学 ， 机械设计及理论， 2006， 硕士

【摘要】 预分解新型干法水泥生产技术是目前水泥生产的最先进的技术,分解炉是新型干法水泥生产线上预分解技术的核心设备和关键技术装备之一,其性能优劣直接影响到系统能耗、环保排放以及整个系统的生产效率。分解炉系统内部的流场非常复杂,燃料燃烧和生料分解这两个反应是悬浮于气流中进行的,各过程相互制约,使得分解炉系统的设计和开发具有很大的难度。长期以来,分解炉的设计方法主要是依靠试验及由大量实验数据归纳出的经验公式。 以计算流体力学(Computational Fluid Dynamics,CFD)为理论基础的数值模拟技术能对流动、传热、燃烧、化学反应、多相流等问题进行准确的预测,因此在工程中得到越来越多的推广和应用。将数值模拟方法应用于分解炉的流场研究,进而优化其结构和操作参数,提高其各项性能,可以节省大量的开发费用,还能大大缩短研发周期,这对于分解炉的开发具有重要的理论意义和工程应用价值。 本文采用CFD数值模拟的方法对2500t/d强化悬浮式分解炉(Reinforced Suspension Precalciner,RSP)内三维湍流流场进行了研究。在建立模型过程中,基本保证了分解炉几何结构的完整真实性。在划分计算网格时,采用了混合网格生成技术,并对细小的结构进行了网格的局部细化。这些措施都保证了计算结果能够更加真实的描述分解炉流场中的各种流动特征。对气相流场描述时,采用了重整化群(renormalization group,RNG)k-ε双方程湍流模型,该模型对于分解炉内部的强旋流动模拟更合理。对炉内生料及煤粉颗粒的运动则采用随机颗粒轨道模型进行模拟。该模型的优点是能够模拟有复杂经历的颗粒相,并且能够模拟颗粒的湍流扩散和气固相之间的耦合作用。对煤粉的燃烧模拟则采用了非预混燃烧模型,对挥发份的燃烧采用概率密度函数模型,焦碳的燃烧采用表面反应模型,挥发份的析出模型选用两步竞争反应模型,燃烧的辐射传热采用P-1模型。在数值计算时,对气体的控制方程采用控制容积法进行离散,差分格式为二阶迎风差分,离散方程组的压力速度耦合采用SIMPLE算法,求解方程采用TDMA逐面迭代和低松弛因子。对于颗粒的常微分控制方程组则采用数值积分的方法求得解析解。更多还原

【Abstract】 Dry-process precalciner kiln technology is the most advanced technology in cement manufacture at present, and precalciner is one of the hard core and key technology equipment in it. The performance of precalciner has great effect on energy consumption, pollutants discharge and producing efficiency of the system. The flow field in precalciner system is very complex as well as the reactions of fuel combustion and raw materials decomposing, which are influenced by each other, are taken place in suspension of the air flow. For these reasons, it is difficult to research and develop the precalciner system. In the past years, design of the precalciner system depends mainly on experimental data and empirical formula.The numerical simulation based on the Computational Fluid Dynamics (CFD) is applied widely in the engineering field due to its accurate numerical prediction for the flow, heat exchange, chemistry reaction and multiphase flow. So numerical simulation on the turbulence flow is adopted to investigate the flow character in the precalciner to optimize system structure and improve system performance. This method can save the R&D cost and time so that it is significant in the engineering application.In this dissertation, CFD numerical simulations of three-dimensional turbulent flow in 2500t/d Reinforced Suspension Precalciner were studied. The integrity and authenticity of geometry structure of the precalciner is ensured at model establishing process. Mixed gridding technology is applied at gridding drawing process, and the gridding of small structure is minished. All of this measure ensures the reality of the results. The gas phase is expressed with renormalization group (RNG) k-ε two-equation model. This model is more reasonable to strong eddy flow in precalciner. Movement of raw material and coal particle is simulated by the particle stochastic trajectory model. This model is capable in simulating particle with complicated experience. It also enables to simulate coupling interaction between gas phase and particle phase, turbulence diffusion of particle is also regarded in this model. Non-premixed combustion model is adopted in simulating coal combustion;volatilescombustion is expressed with the probability density function model;char combustion is expressed with the surface reaction model;released rate of the volatiles is expressed with the two competing rates model;radiation of the combustion is expressed with the P-l radiation model. At calculating process, Control Volume Method (CVM) is applied in discretizing the gas phase control equation. The difference format applied is second order upwind difference. Coupling between pressure and velocity is solved by the SIMPLE arithmetic. Tri-Diagonal Matrix Algorithm (TDMA) method and low relaxing factor are also applied in solving the control equation.The simulating result predicts the flow field, the particle movement and the coal combustion, which is coincident with the flow tendency. The result provides useful information for analyzing the kinetics regulation and reaction in precalciner, and also gives important theoretical basis for structure optimizing and practical operation parameter selecting of the precalciner.更多还原