【摘要】：隨著細粒煤入洗比例的逐年提高以及高硫煤市場銷售的限制,尋找更有效的細粒煤脫硫降灰新技術(shù)乃是當前煤炭工業(yè)的迫切任務(wù)和難題。采用離心力場分選的Falcon離心分選機在細粒煤的高效脫硫降灰中具有明顯的優(yōu)勢。本論文主要利用數(shù)值計算以及CFD模擬研究Falcon離心分選機的流場特性,其中結(jié)合高速動態(tài)拍攝技術(shù)對流場進行實際觀測,進而保證數(shù)值計算及模擬的有效應(yīng)用。論文綜述了細粒煤重選及目前選礦設(shè)備發(fā)展現(xiàn)狀,闡述了適用于Falcon離心分選機數(shù)值模擬的多相流模型、湍流模型以及曳力模型,綜述了目前多相流流場觀測與CFD模擬的發(fā)展現(xiàn)狀。整理并完善了關(guān)于Falcon離心分選機的計算理論,建立了分層區(qū)與分選區(qū)的流膜厚度計算公式,反沖水流量公式以及流膜分選下限計算公式,并進行了實驗驗證。通過研究得到:分層區(qū)流膜厚度與給料速度成正比,與離心機轉(zhuǎn)速成反比,且流膜呈反比例函數(shù)曲線分布;分層區(qū)流膜厚度與反沖水壓成正比和轉(zhuǎn)速成反比;反沖水流速主要和水壓和孔口結(jié)構(gòu)有關(guān);Falcon離心分選的分選下限受到顆粒極限脈動高度和表面波的雙重限制。利用高速動態(tài)技術(shù)對離心分選機流場進行測試,獲得流場流態(tài)以及流速信息,通過觀查和實測發(fā)現(xiàn):分層區(qū)流膜分布與數(shù)值計算分析吻合,且流膜厚度計算公式較為準確;采用雷諾應(yīng)力模型模擬Falcon離心分選機流場流速與實測結(jié)果偏差不大,因此該模型具有良好的適用性;流場內(nèi)存在霧化現(xiàn)象,會造成一定回流。CFD模擬中采用歐拉模型為多相流模型,雷諾應(yīng)力模型為湍流模型,模擬得到離心分選機分層區(qū)與分選區(qū)內(nèi)顆粒運動情況,切向、徑向、軸向三向速度的分布情況,以及湍流場的分布情況。經(jīng)研究發(fā)現(xiàn):顆粒運動軌跡呈三維螺旋結(jié)構(gòu)且來復(fù)圈內(nèi)伴有一定的繞流運動;分層區(qū)速度分布與其他離心分選機相差不大,但分選區(qū)特別是來復(fù)圈內(nèi)速度分布則大不相同;反沖水的引入使得分選區(qū)的湍流強度明顯增加,但高強度湍流區(qū)域集中在近壁面薄層。此外,結(jié)合模擬得到的相關(guān)流場信息并利用模擬應(yīng)用于實際問題,將CFD數(shù)值模擬應(yīng)用于離心分選機分選機制和結(jié)構(gòu)改造等方面。
[Abstract]:With the increasing of fine coal washing ratio year by year and the restriction of high sulfur coal market sales, it is an urgent task and difficult problem to find more effective desulfurization and ash reduction technology for fine coal. Falcon centrifugal separator with centrifugal force field separation has obvious advantages in high efficiency desulphurization and ash reduction of fine coal. In this paper, the flow field characteristics of Falcon centrifuge are studied by numerical calculation and CFD simulation. The flow field of Falcon centrifuge is observed in combination with high speed dynamic shooting technology, so as to ensure the effective application of numerical calculation and simulation. This paper summarizes the development of fine coal gravity separation and its equipment at present, and expounds the multiphase flow model, turbulence model and drag model suitable for numerical simulation of Falcon centrifuge separator. The development of multiphase flow field observation and CFD simulation is reviewed. The calculation theory of Falcon centrifugal separator is sorted out and improved. The formula of the thickness of flow film, the formula of backwash water flow and the calculation formula of lower limit of separation of flow film are established, and the experimental results are verified. The results show that the thickness of the flow film in the stratified zone is directly proportional to the feed speed and inversely proportional to the speed of the centrifuge, and the flow film is distributed in an inverse proportional function curve, and the thickness of the flow film in the stratified zone is directly proportional to the backwash water pressure and the speed of the flow film is inversely proportional to the speed of the centrifuge. The velocity of recoil water is mainly related to water pressure and pore structure, and the lower limit of separation for Falcon centrifugal separation is limited by the limit of particle pulsation height and surface wave. The flow field of centrifugal separator was measured by high speed dynamic technology, and the flow state and velocity information were obtained. Through observation and measurement, it was found that the flow film distribution in the stratified zone was in agreement with the numerical analysis, and the formula for calculating the thickness of the flow film was more accurate. The Reynolds stress model is used to simulate the flow velocity of Falcon centrifuge. The phenomenon of atomization exists in the flow field, which will cause a certain reflux. In the CFD simulation, the Euler model is used as the multiphase flow model, the Reynolds stress model is the turbulence model, and the movement of the particles in the stratified zone and the separation zone of the centrifugal separator is obtained by simulation, which is tangential and radial. The distribution of axial three direction velocity and the distribution of turbulent field. It is found that the velocity distribution of the stratified zone is not different from that of other centrifugal separators, but the velocity distribution in the sub-area, especially in the inner ring, is quite different from that of the other centrifugal separators, and the velocity distribution in the stratified zone is similar to that of the other centrifugal separators, and the velocity distribution in the stratified zone is different from that of other centrifugal separators. With the introduction of recoil water, the turbulence intensity of the subdistrict is increased obviously, but the high intensity turbulence region is concentrated near the wall layer. In addition, the CFD numerical simulation is applied to centrifuge sorting mechanism and structural modification by combining the relevant flow field information obtained from the simulation and the application of the simulation to practical problems.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TD455.5

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