褐煤磨煤机干燥模拟及传热传质分析
发布时间：2018-11-05 17:07
【摘要】：本文以含水量29.86%的蒙东褐煤为研究对象,以褐煤工业分析和热重分析为基础,建立了低温热烟气快速干燥系统,以褐煤自身燃烧产生的热烟气为干燥介质,在磨煤机内破碎与干燥同时进行,既保证了褐煤的干燥品质,同时具备环保、节能的特点。为了进一步研究低温热烟气快速干燥系统的干燥机理,提高干燥效率,本课题利用Fluent软件建立了磨煤机干燥场的等比例三维模型。通过对磨煤机内不同时刻颗粒分布、颗粒速度、停留时间等特征的模拟,研究干燥过程中原料煤的流动特性,避免煤粉堆积、出粉不利等恶劣情况的发生。通过改变主轴转速、褐煤粒径以及烟气流量等影响因素,发现在一定范围内煤样粒度越大,流动状况越好;主轴转速维持在500-700r/s时出粉较快。根据磨煤机内颗粒温度、水分含量以及传热系数的模拟结果,发现褐煤粒度越小干燥越彻底,但出粉效率越低,3mm粒径的褐煤能够满足出粒顺畅和干燥彻底两方面的要求;选用200℃的热烟气能够在保证褐煤不发生热解的情况下显著降低提质褐煤的含水率。烟气流量的改变对流动状况和干燥效果影响不大。为了更深层次的研究褐煤脱水过程的传热传质机理,结合在恒温条件下热风干燥实验结果,建立了一维球坐标下褐煤蒸发界面由外向内迁移的单颗粒干燥数学模型,获得蒙东褐煤热风干燥水分有效扩散系数为1.24×10-10-5.097×10-9。
[Abstract]:In this paper, based on the industrial analysis and thermogravimetric analysis of lignite, a rapid drying system of low temperature and hot flue gas is established, and the hot flue gas produced by the combustion of lignite itself is taken as the drying medium, taking the lignite with water content of 29.86% as the research object. Crushing and drying simultaneously in the mill not only ensures the drying quality of lignite, but also has the characteristics of environmental protection and energy saving. In order to further study the drying mechanism of low temperature hot flue gas drying system and improve the drying efficiency, the equal proportion three-dimensional model of coal mill drying field was established by using Fluent software. By simulating the characteristics of particle distribution, particle velocity and residence time in the mill at different times, the flow characteristics of raw coal in the drying process are studied to avoid coal powder accumulation and unfavorable coal production. By changing the main shaft speed, lignite particle size and flue gas flow rate, it is found that the larger the coal sample size in a certain range, the better the flow condition, and the faster the pulverized coal is produced when the spindle speed is maintained at 500-700r/s. According to the simulation results of particle temperature, moisture content and heat transfer coefficient of coal mill, it is found that the smaller the grain size of lignite is, the more thorough drying is, but the lower the pulverization efficiency is, the more smooth and dry the lignite particle size of 3mm can be. The moisture content of lignite can be significantly reduced by using 200 鈩，
本文编号：2312732
[Abstract]:In this paper, based on the industrial analysis and thermogravimetric analysis of lignite, a rapid drying system of low temperature and hot flue gas is established, and the hot flue gas produced by the combustion of lignite itself is taken as the drying medium, taking the lignite with water content of 29.86% as the research object. Crushing and drying simultaneously in the mill not only ensures the drying quality of lignite, but also has the characteristics of environmental protection and energy saving. In order to further study the drying mechanism of low temperature hot flue gas drying system and improve the drying efficiency, the equal proportion three-dimensional model of coal mill drying field was established by using Fluent software. By simulating the characteristics of particle distribution, particle velocity and residence time in the mill at different times, the flow characteristics of raw coal in the drying process are studied to avoid coal powder accumulation and unfavorable coal production. By changing the main shaft speed, lignite particle size and flue gas flow rate, it is found that the larger the coal sample size in a certain range, the better the flow condition, and the faster the pulverized coal is produced when the spindle speed is maintained at 500-700r/s. According to the simulation results of particle temperature, moisture content and heat transfer coefficient of coal mill, it is found that the smaller the grain size of lignite is, the more thorough drying is, but the lower the pulverization efficiency is, the more smooth and dry the lignite particle size of 3mm can be. The moisture content of lignite can be significantly reduced by using 200 鈩，
本文编号：2312732
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