【摘要】：本文以含水量29.86%的蒙東褐煤為研究對象,以褐煤工業(yè)分析和熱重分析為基礎(chǔ),建立了低溫熱煙氣快速干燥系統(tǒng),以褐煤自身燃燒產(chǎn)生的熱煙氣為干燥介質(zhì),在磨煤機內(nèi)破碎與干燥同時進行,既保證了褐煤的干燥品質(zhì),同時具備環(huán)保、節(jié)能的特點。為了進一步研究低溫熱煙氣快速干燥系統(tǒng)的干燥機理,提高干燥效率,本課題利用Fluent軟件建立了磨煤機干燥場的等比例三維模型。通過對磨煤機內(nèi)不同時刻顆粒分布、顆粒速度、停留時間等特征的模擬,研究干燥過程中原料煤的流動特性,避免煤粉堆積、出粉不利等惡劣情況的發(fā)生。通過改變主軸轉(zhuǎn)速、褐煤粒徑以及煙氣流量等影響因素,發(fā)現(xiàn)在一定范圍內(nèi)煤樣粒度越大,流動狀況越好;主軸轉(zhuǎn)速維持在500-700r/s時出粉較快。根據(jù)磨煤機內(nèi)顆粒溫度、水分含量以及傳熱系數(shù)的模擬結(jié)果,發(fā)現(xiàn)褐煤粒度越小干燥越徹底,但出粉效率越低,3mm粒徑的褐煤能夠滿足出粒順暢和干燥徹底兩方面的要求;選用200℃的熱煙氣能夠在保證褐煤不發(fā)生熱解的情況下顯著降低提質(zhì)褐煤的含水率。煙氣流量的改變對流動狀況和干燥效果影響不大。為了更深層次的研究褐煤脫水過程的傳熱傳質(zhì)機理,結(jié)合在恒溫條件下熱風干燥實驗結(jié)果,建立了一維球坐標下褐煤蒸發(fā)界面由外向內(nèi)遷移的單顆粒干燥數(shù)學模型,獲得蒙東褐煤熱風干燥水分有效擴散系數(shù)為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，

本文編號：2312732