本文選題：油頁巖 + CFD　； 參考：《大連理工大學》2015年碩士論文

【摘要】：能源是一個社會和國家發(fā)展壯大的基石和支柱,伴隨著石油使用量的增加,石油資源僅能維持70年左右就會枯竭。應對石油枯竭危機、尋找新生能源,成為各個國家面臨的重大議題。油頁巖富含有機質,可以通過干餾等方式產生油和可燃氣體,也可以用來燃燒發(fā)電。隨著技術的進步,油頁巖干餾生產頁巖油生產成本的降低,而且其己探明總儲量要比石油還要大,油頁巖資源正漸漸成為石油的替代品。大部分油頁巖含水率較高,造成能耗增大、油質下降等不利影響。干餾之前,要使用高溫氣體將油頁巖的水分蒸發(fā)掉。流化床干燥器以其高效的傳熱、傳質特點正越來越多的應用到油頁巖的干燥過程。對油頁巖在流化床中行為和機理研究對于更加高效地進行油頁巖的干燥,提供了良好的理論基礎,將來可以更好地利用油頁巖資源。受實驗條件的限制,油頁巖顆粒在流化床干燥中的行為和機理不能進行有效地監(jiān)測和測量。本文以雙流體模型和顆粒動力學理論為基礎建立流化床模型,使用流體力學軟件耦合用戶自定義函數(UDF)的方法,對顆粒在流化床中最小流化速度、床層膨脹高度、初始氣泡尺寸、床層壓降、氣固傳熱等進行了研究,并得到了以下結論：小顆粒的完全流化速度和最小鼓泡速度的差要比大顆粒的要大；計算了不同速度下的床層膨脹高度并且與經驗關聯(lián)式進行了比較,發(fā)現隨著氣速的增大,床層的膨脹高度近乎呈線性增加；增加氣速,氣泡的初始尺寸也增大,振動有著抑制氣泡增大的作用,提高振動頻率氣泡尺寸減小,提高振幅氣泡尺寸略有增加；床層壓降隨著氣速的增大呈現先下降后上升的趨勢；在加入振動后,發(fā)現隨振動強度的增大壓降變化不大,壓降標準差曲線隨壓降的增大逐漸變大；床層高度的增加,床層壓降也逐漸增大,而且在床層完全流化后床層高度對壓降的影響最大。氣固傳熱系數在近布風板區(qū)域主要受氣固兩相的溫差控制,在遠離布風板區(qū)域主要受顆粒濃度的控制；在床層所有區(qū)域,顆粒濃度對氣固兩相的熱交換系數都起著重要作用；在近布風板區(qū)域,煙氣的溫度受壁面溫度的影響呈現兩側低中間高的趨勢,而在遠離布風板的區(qū)域溫度沿徑向分布比較均勻。進氣溫度越高流化床的干燥能力越強。干燥在初始階段主要受外部煙氣溫度控制,干燥在后半段主要受內部毛細空隙水分擴散控制。本文研究了油頁巖顆粒在流化床中流動特征參數和氣固傳熱傳質的規(guī)律,為流化床的設計和油頁巖干燥機理進一步深入研究奠定了基礎。
[Abstract]:Energy is the cornerstone and pillar of the development and expansion of a society and country. With the increase of oil use, oil resources can only be exhausted for about 70 years. To deal with the crisis of oil exhaustion and to find new energy sources, it has become a major issue for all countries. Oil shale is rich in machinery and can produce oil and flammable by dry distillation. Gas can also be used to burn electricity. With the progress of technology, the production cost of shale oil production in oil shale dry distillation is reduced, and its proven total reserves are larger than oil. Oil shale resources are becoming a substitute for oil. Most oil shale has high water cut, resulting in higher energy consumption, lower oil quality and other adverse effects. A fluidized bed dryer has been applied to the drying process of oil shale with its high heat transfer and mass transfer characteristics. The study on the behavior and mechanism of oil shale in the fluidized bed provides a good theoretical basis for the more efficient drying of oil shale, which will be possible in the future. Better use of oil shale resources. Limited by the experimental conditions, the behavior and mechanism of oil shale particles in fluidized bed drying can not be effectively monitored and measured. In this paper, a fluidized bed model is built on the basis of two fluid model and particle dynamics theory, and the method of coupling user custom function (UDF) with fluid mechanics software is used. The minimum fluidization velocity in the fluidized bed, the height of the bed expansion, the initial bubble size, the bed pressure drop and the gas solid heat transfer have been studied. The following conclusions are obtained: the difference between the complete fluidization velocity of the small particles and the minimum bubble velocity is larger than that of the large particles; the height of the bed expansion at different speeds is calculated and the correlation with the empirical formula is calculated. It is found that the expansion height of the bed is almost linearly increased with the increase of gas velocity, and the initial size of the bubble increases with the increase of gas velocity. The vibration has the effect of inhibiting the increase of bubbles, increasing the bubble size of the vibration frequency and increasing the size of the amplitude bubble, and the pressure drop of the bed layer decreases first with the increase of gas velocity. After the vibration, it is found that the pressure drop varies little with the increase of the vibration intensity, the standard deviation curve of the pressure drop increases gradually with the increase of the pressure drop; the bed height increases, the bed pressure drop increases gradually, and the height of the bed layer has the greatest influence on the pressure drop after the bed layer is completely fluidizing. The heat transfer coefficient of the gas solid is in the near distribution wind plate area. The temperature difference control of the main gas-solid two phases is mainly controlled by the particle concentration in the area far away from the distribution wind plate. In all areas of the bed, the concentration of particles plays an important role in the heat exchange coefficient of the gas-solid two phases; in the near distribution wind plate area, the temperature of the flue gas is under the influence of the wall temperature at the lower middle height, but is far from the air distribution. The region temperature of the plate is more uniform along the radial distribution. The higher the air inlet temperature is, the stronger the drying capacity of the fluidized bed. The drying is mainly controlled by the external flue gas temperature in the initial stage, and the drying is mainly controlled by the internal capillary void diffusion in the second half. This paper studies the characteristics of the flow characteristics and the heat and mass transfer in the fluidized bed. The rule laid a foundation for further study of fluidized bed design and oil shale drying mechanism.
【學位授予單位】：大連理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TE662

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