粉粒喷动床半干法烟气脱硫反应的数值模拟及气固两相流动PIV实验

发布时间：2019-03-29 15:47

【摘要】：二氧化硫排放量的90%来自于燃煤,排入空气中,在适当气象条件下氧化成硫酸和硫酸盐,形成了雾霾天气,还会造成严重的酸雨问题。目前,各国学者先后研究出了各种脱硫技术。粉-粒喷动床半干法烟气脱硫技术具有脱硫率高,吸收剂利用率高,对环境污染小等优点,成为一种极具有前景的脱硫技术。本文根据实验过程中喷动床进行数值模拟分析。在喷动床内半干法烟气脱硫过程中建立水发生汽化的数学模型来研究该过程中的传质传热,采用双流体模型最终获得粉-粒喷动床内水汽化结果。表明,喷射区和环隙区外侧是发生水汽化最主要的两个区域,在喷射区和环隙区外侧产生的气相水随着气流进入床周围区域,在料浆入口处和喷泉区顶部水相体积分数较大。气体温度在入口处最高,其次是喷射区、喷泉区外侧和环隙区外侧。分析了脱硫反应过程中各个步骤,通过简化假设脱硫反应过程将整个过程转化为两个相之间的传质控制过程,并建立反应模型来研究半干法烟气脱硫过程中的脱硫反应特性,采用双流体模型模拟粉-粒喷动床内脱硫反应过程,模拟结果与实验结果进行对比。结果表明,液相水分布最多的区域在环隙区,脱硫反应发生的最主要的区域也在环隙区。反应产物在环隙区和喷动床出口处有所堆积。反应达到稳定时,反应脱硫效率比文献模拟值稍微有所增加,但是仍略低于实验值,仍需进一步改进优化模型来提高计算的准确性。将纵向涡流发生器引入喷动床内的气固两相流动体系,期望气相经过纵向涡流发生器产生纵向涡,从而带动颗粒相实现涡流运动,以期达到强化喷动床内喷射区及环隙区内气体、颗粒的横向混合。并利用PIV技术对加有纵向涡发生器的喷动床进行实验研究。结果表明,纵向涡发生器强化了喷射区及环隙区内气体、颗粒的横向混合。在相同扰流元件直径条件下,球体扰流元件对颗粒径向运动的强化效应好于圆柱体扰流元件。在喷动床有限的结构空间内存在着最佳的扰流元件设计尺寸(直径、安装间距),使得纵向涡流对喷动床内颗粒径向运动的强化效果达到最佳。
[Abstract]:90% of sulfur dioxide emissions come from coal burning, discharged into the air, oxidized to sulfuric acid and sulfate under appropriate meteorological conditions, forming haze weather and causing serious acid rain problems. At present, scholars from all over the world have developed various desulfurization technologies. The semi-dry flue gas desulfurization (FGD) technology with powder-particle spray bed has the advantages of high desulphurization rate, high absorption efficiency and low environmental pollution. It has become a promising desulfurization technology. In this paper, numerical simulation analysis is carried out according to the spray bed during the experiment. A mathematical model of water vaporization in the process of semi-dry flue gas desulfurization (FGD) in the spray bed was established to study the mass transfer and heat transfer in this process. Finally, the results of water vaporization in a powder-particle spray bed were obtained by using a two-fluid model. The results show that the injection zone and the outer part of the annular zone are the two most important areas for the occurrence of water vaporization. The gas water generated at the injection zone and the outer side of the annular zone enters the area around the bed with the air flow, and the volume fraction of the water phase at the inlet of the slurry and the top of the spring area is higher than that at the inlet of the slurry and the top of the spring. The gas temperature is the highest at the inlet, followed by the spray zone, the spring area and the annular zone. By simplifying the assumed desulfurization reaction process, the whole process was transformed into a mass transfer control process between the two phases, and a reaction model was established to study the desulfurization reaction characteristics in the semi-dry flue gas desulfurization process. A two-fluid model was used to simulate the desulfurization process in a powder-particle spray bed, and the simulation results were compared with the experimental results. The results show that the region with the largest distribution of liquid phase water is in the annular zone, and the main area of desulfurization reaction is also in the annular zone. The reaction products accumulate in the ring gap region and the outlet of the spray bed. When the reaction is stable, the desulfurization efficiency of the reaction is slightly higher than the simulated value in the literature, but it is still a little lower than the experimental value. It is still necessary to improve the optimization model to improve the accuracy of the calculation. The longitudinal eddy current generator is introduced into the gas-solid two-phase flow system in the jet bed, and the gas phase is expected to produce the longitudinal vortex through the longitudinal eddy current generator, thus driving the particle phase to realize the eddy current movement. In order to enhance the transverse mixing of gas and particles in the injection zone and annular zone of the spray bed. The spray bed with longitudinal vortex generator was studied by PIV technique. The results show that the longitudinal vortex generator enhances the transverse mixing of gas and particles in the injection and annular regions. When the diameter of the spoiler element is the same, the reinforcement effect of the spherical spoiler on the radial motion of the particle is better than that of the cylindrical spoiler. In the finite structure space of the spray bed, there is the optimum design size (diameter, installation distance) of the spoiler element, which makes the longitudinal eddy current enhance the radial motion of the particles in the spray bed to the best effect.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701

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