选煤厂转载点煤流撞击作用下粉尘逸散与分布特性模拟研究

Simulation study on dust emission and distribution characteristics of dust under the impact of coal flow at the transpersite of coal preparation plant

  • 摘要: 选煤厂煤炭输运系统中的转载点是产尘的重要源头。煤炭在转载点由于落差等作用产生大量粉尘,引发粉尘污染等问题。为抑制转载过程中的粉尘逸散,探究粉尘分布特征以控制粉尘污染,基于某选煤厂现场实际,构建了等比例的煤炭转载点三维结构,研究了煤流对冲、撞击状态下的粉尘扩散过程。首先,依据相似理论,构建了缩尺比为3∶14的转载点模型实验台,研究了转载过程典型位置的风场分布特征,发现在高度方向上两侧风速较高,可达6 m/s左右,而中上部风速偏低,且模拟与实验研究结果一致性较好,验证了数值模拟方法及其相关结论的有效性。同时,基于CFD–DDPM方法,考虑了颗粒间的碰撞,对转载过程撞击作用下的粉尘撞击与扩散过程进行了可视化研究,发现粉尘撞击区两侧及其底部区域均存在一对旋涡,对粉尘分布影响较大;不同粒径的粉尘在不同区域的分布差异较大,水平输送段封闭侧出现质量浓度高达9000 mg/m3的区域,此处宜加强密封防止粉尘泄露。基于Visual Basic自主开发了后处理程序,分析了不同粒径粉尘在不同区域的占比。比较发现,PM10~PM40气流跟随性好,PM50~PM100沉积显著。针对粉尘浓度较高的区域设计除尘方案以减少粉尘污染,在竖直落料段上方安装抽吸风机,其抽吸风速对竖直落料段粉尘分布影响显著,当抽吸风速为15 m/s时,高速气流促进粉尘往中上部区域聚集,粉尘质量浓度高达6 mg/m3,为优化转载结构、抑制转载过程的粉尘逸散提供了理论指导。

     

    Abstract: The transpersite in the coal transportation system is an important source of dust production in coal preparation plants. The coal produces a large amount of dust under the action of the drop of the transpersite, causing dust pollution and other problems. In order to inhibit the dust emission during the transfer process and explore the dust distribution characteristics to control dust pollution, based on the actual situation of a coal preparation plant, a three-dimensional structure of coal transpersite with equal proportion is constructed, and the dust diffusion process in the state of impinge and impact of coal flow is studied. Firstly, according to the similarity theory, a transpersite model test bench with a scale ratio of 3∶14 is constructed, and the wind field distribution characteristics of typical positions in the transfer process are studied. It is found that the wind speed on both sides of the wall in the height direction is high, up to about 6 m/s, while the wind speed in the middle and upper parts is low, and the simulation results are in good agreement with the experimental results, which verified the numerical simulation method and its related conclusions. At the same time, based on the CFD–DDPM method, considering the collision between particles, the dust impact and diffusion process under the impact of the transfer process is visually studied. It is found that there are a pair of vortices on both sides of the dust impact zone and its bottom area, which have a great influence on the dust distribution. The distribution of dust with different particle sizes in different regions is quite different. The concentration of dust in the closed side of the horizontal conveying section is as high as 9000 mg/m3, and this area needs to strengthen its sealing to prevent dust leakage. Based on Visual Basic, a post-processing program is developed independently, and the proportion of dust with different particle sizes in different regions is analyzed. It is found that the PM10–PM40 airflow follows well, and the PM50–PM100 deposition is significant. The dust removal scheme is designed for the area with high dust concentration to reduce the dust pollution, the suction fan is installed above the vertical blanking section, and the suction wind speed has a significant effect on the dust distribution in the vertical blanking section. When the suction wind speed is 15 m/s, the high-speed airflow promotes the dust to gather in the middle and upper regions, and the dust concentration is as high as 6 mg/m3, which provides theoretical guidance for optimizing the transfer structure and inhibiting the dust emission in the transfer process.

     

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