基于油页岩气流干燥的CFD模拟和实验研究

发布时间：2018-03-05 08:01

  本文选题：油页岩　切入点：计算流体力学　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：油页岩作为一种“非常规油气资源”,是本世纪重要的接替能源之一,因储量丰富受到全球的广泛关注。但由于油页岩孔隙发达、含水量高的特点,在干馏过程中常出现很多不利于生产的问题,所以,在油页岩热裂解前必须对其进行干燥脱水处理。而气流干燥因其处理量大、设备简单、投资低等优点在干燥处理中有着广泛应用。本文采用了流体动力学模拟新技术,对油页岩的气流干燥过程进行了模拟研究,揭示了干燥过程中各种流场的详细分布情况和变化趋势,同时,通过Fluent软件中的用户自定义(user defined functions)功能对软件中的物理模型进行二次开发,创建了更符合油页岩气流干燥过程的传热、传质计算模型。对模拟结果进行系统分析的同时,还分别进行了冷态下的中试实验和热态下的实验室实验,将气流管动力学模拟、气流干燥过程热力学模拟的模拟结果分别和实验结果进行对比,模拟结果和实验数据吻合较好,证明了模拟结果的可靠性和自建模型的正确性。对气流干燥管的动力学模拟和实验研究表明：对料气质量比非常低的稀相输送状态而言,可认为颗粒之间没有相互干扰和影响,所以应使用欧拉-拉格朗日算法来模拟颗粒的运动特性,即Fluent当中的离散相模型(DPM);将进气方式改为两侧进气,或者在气流管底部增加倾斜角度合适的倒锥形缩孔,均可明显改善单侧进气时易出现的偏流现象,但缩孔结构也会大幅增加设备的局部压力损失。对气流干燥管的热力学模拟和实验研究表明：气流干燥过程对应两阶段干燥动力学模型(two-stage drying kinetics model)中的第一个阶段,也进一步证明了气流干燥过程中的水分蒸发主要发生在恒速干燥阶段；油页岩气流干燥过程中,计算传热系数的Nu～Re的经验关联式为J.Baeyens经验关联式：Nu=0.15Rep。用该关联式计算得到的模拟结果与实验结果的相对误差如下：气相出口温度(℃)的相对误差为-2.9%；物料最终温度(℃)的相对误差为-8.9%；气相出口湿度的相对误差为35%；平均传热系数的相对误差为-2.8%。
[Abstract]:Oil shale, as a kind of "unconventional oil and gas resource", is one of the important alternative energy sources in this century, and has attracted worldwide attention because of its rich reserves. However, because of the developed porosity and high water content of oil shale, In the process of distillation, there are many problems which are not conducive to production. Therefore, the oil shale must be dried and dehydrated before it is pyrolyzed, and the airflow drying process is simple because of its large amount of treatment and simple equipment. The advantages of low investment are widely used in drying treatment. In this paper, a new hydrodynamic simulation technique is used to simulate the flow drying process of oil shale. The detailed distribution and variation trend of various flow fields in the drying process are revealed. At the same time, the physical models in the software are redeveloped through the user-defined user defined functionsfunction in the Fluent software. A model of heat and mass transfer is established, which is more consistent with the process of oil shale airflow drying. While the simulation results are systematically analyzed, pilot experiments under cold state and laboratory experiments in hot state are carried out, and the dynamics of airflow tube is simulated. The simulation results of the thermodynamic simulation of airflow drying process are compared with the experimental results, and the simulation results are in good agreement with the experimental data. It is proved that the reliability of the simulation results and the correctness of the self-built model. The dynamic simulation and experimental study of the airflow drying pipe show that there is no interference and influence between the particles for the rare-phase transport state with very low mass ratio of solid to gas. Therefore, the Euler-Lagrangian algorithm should be used to simulate the motion characteristics of the particles, that is, the discrete phase model in Fluent; the intake mode should be changed to two sides of air intake, or an inverted conical shrinkage hole with a suitable tilt angle should be added to the bottom of the airflow pipe. All of them can obviously improve the phenomenon of bias which is easy to appear in the air intake on one side. However, the shrinkage pore structure also increases the local pressure loss of the equipment. The thermodynamic simulation and experimental study on the airflow drying tube show that the gas drying process corresponds to the first stage of the two-stage drying kinetics model. It is further proved that the evaporation of water in the process of airflow drying mainly takes place in the stage of constant speed drying, while in the process of gas flow drying of oil shale, The empirical correlation formula of Nu~Re for calculating heat transfer coefficient is J. Baeyens empirical correlation formula: 0.15 Rep. the relative error between the simulated and experimental results calculated by this correlation formula is as follows: the relative error of gas phase exit temperature (鈩，

本文编号：1569391