流化床內(nèi)固液兩相流特性及底板布孔優(yōu)化的模擬研究
發(fā)布時間：2018-08-05 18:27
【摘要】：隨著經(jīng)濟社會的發(fā)展,環(huán)境問題已成為制約我國社會發(fā)展的重要問題之一,而在諸多的環(huán)境問題中水污染問題又最為突出和嚴重,尤其是城市的快速發(fā)展產(chǎn)生了大量的生活污水,而這些生活污水大多都不經(jīng)處理直接排放到自然界的水體中,對河流、湖泊、海洋等的環(huán)境造成了嚴重的污染,要想恢復(fù)到自然狀態(tài)是十分困難的。水資源在我國并不豐富,而各種水體的污染,將使可利用的水資源進一步減少,影響人民的正常生活及工農(nóng)業(yè)的生產(chǎn)。要想實現(xiàn)水資源的可持續(xù)利用,就必須對工業(yè)和生活污水進行凈化處理,發(fā)展建立一整套經(jīng)濟實用的污水處理設(shè)備和方法,而在眾多的污水處理方法中生物膜污水處理技術(shù)由于其操作方便,運行成本較低,而使其成為最重要的污水處理方法之一。本文采用RNG k-ε湍流模型結(jié)合歐拉-歐拉多相流模型對一典型的液流動力流化床進行數(shù)值模擬研究,比較了不同分布板開孔形式下的多種物理量,從而確定出合理的流化床進口分布板的布孔形式,分析了不同載體屬性及操作條件下流化床內(nèi)的固體體積分數(shù)、流場流態(tài)、湍動能及其湍動能耗散率等物理參量,從而確定了流化床的最優(yōu)操作參數(shù),發(fā)現(xiàn)不同運行工況的優(yōu)缺點,從而使讀者可以根據(jù)需要選擇適合自己工況的分布板布孔方式、載體屬性及操作參數(shù)。通過分析比較,得出如下結(jié)論:(1)通過對模型驗證一的比較分析,發(fā)現(xiàn)采用歐拉-歐拉多相流模型輔以RNGk-ε湍流模型可以很好的模擬流化床內(nèi)的固液兩相流。通過模型驗證二對所選用的多相流模型、湍流模型及其邊界條件和數(shù)值求解方法進行了驗證,模擬值與試驗數(shù)據(jù)吻合較好,得出:所選數(shù)學(xué)模型、數(shù)值求解方法及邊界條件可較好地模擬出流化床內(nèi)固液二相流的流動特性。(2)通過與布設(shè)其他形式的載體分布板相比,布設(shè)分布板A時載體顆粒在流化床內(nèi)處于完全流化狀態(tài),形成均一流動層,無局部高濃度區(qū)域,軸向濃度有波動但是不明顯,流化床內(nèi)濃度分布最為均勻。載體在流化床內(nèi)軸向速度分布較均勻,無過大的速度產(chǎn)生,沿軸向和徑向軸向速度梯度變化較小。布設(shè)分布板A時,載體徑向速度分布范圍明顯大于布設(shè)其他分布板的情況,最大徑向速度為0.17m/s,在徑向上載體顆粒之間的碰撞與摩擦程度更為激烈。(3)在其他初始條件不變的情況下,隨載體粒徑的增大,流化床內(nèi)載體體積分數(shù)和軸向速度均減小,床層的膨脹高度也明顯減小,流速均勻性和流態(tài)都變差。隨載體密度的增大,流化床內(nèi)載體體積分數(shù)相應(yīng)變大,床層膨脹率和軸向速度均減小,流速均勻性變差,流態(tài)也變得不穩(wěn)定。隨載體初始填充高度的增大,流化床內(nèi)載體體積分數(shù)相應(yīng)變大,軸向速度減小,床層膨脹率有小幅波動,流速均勻性和流態(tài)都變差。。隨流化床入口處液體速度的增大,流化床內(nèi)載體體積分數(shù)減小,床層膨脹率和軸向速度均有明顯增大,流速均勻性變差。(4)通過對流化床內(nèi)的載體體積分數(shù)、載體軸向速度分布及流速不均勻系數(shù)等的分析比較后得出:載體顆粒的密度為1500kg/m3,載體粒徑為1mm,載體初始填充高度為0.3m,流化床入口處液體速度為0.15m/S時為所給定生物流化床的最優(yōu)載體屬性和運行參數(shù)。對提高流化床的污水處理效率最為有利。
[Abstract]:With the development of economy and society, environmental problems have become one of the most important problems that restrict the development of our society. In many environmental problems, water pollution is the most prominent and serious problem. In particular, the rapid development of the city has produced a large number of domestic sewage, and most of these domestic sewage are not treated directly to the water in the natural world. In the body, it has caused serious pollution to the environment of rivers, lakes and oceans. It is very difficult to restore to the natural state. Water resources in our country are not rich, and the pollution of various water bodies will make the available water resources further reduced, affecting the people's normal life and the production of industry and agriculture. To realize the sustainable benefit of water resources. It is necessary to purify industrial and domestic sewage and develop a complete set of economical and practical sewage treatment equipment and methods. In many sewage treatment methods, the biofilm sewage treatment technology is one of the most important sewage treatment methods because of its convenient operation and low operating cost. This paper uses RNG k- e turbulence. The flow model is combined with the Euler Orla multiphase flow model to simulate a typical fluid flow dynamic fluidized bed. A variety of physical quantities are compared in the opening form of different distributed plates, thus the pore form of a reasonable fluidized bed inlet distribution plate is determined, and the solid volume in the fluidized bed is analyzed under the different carrier properties and operating conditions. The physical parameters such as fraction, flow flow, turbulent kinetic energy and turbulent energy dissipation rate have been determined, and the optimal operating parameters of the fluidized bed are determined. The advantages and disadvantages of different operating conditions are found, so that readers can choose the distribution pattern of distribution plates suitable for their own working conditions according to their needs, the carrier and the operating parameters. Through analysis and comparison, the following conclusions are drawn. (1) through the comparison and analysis of the model verification one, it is found that the Euler Euler multiphase flow model can be used to simulate the solid and liquid two phase flow in the fluidized bed with the RNGk- epsilon turbulence model. Through the model verification, two models of the selected multiphase flow, the turbulence model and its boundary conditions and numerical solution methods are verified, the simulation values and the experiments are carried out. The data are in good agreement, and the mathematical model, numerical solution and boundary condition can be used to simulate the flow characteristics of solid-liquid two-phase flow in the fluidized bed. (2) the carrier particles in the fluidized bed are completely fluidizing in the fluidized bed, forming a homogeneous flow layer, and there is no local flow layer. (2) compared with other forms of carrier distribution plate, the carrier particles are in the fluidized bed. In the high concentration region, the axial concentration fluctuates but is not obvious, the concentration distribution in the fluidized bed is the most uniform. The axial velocity distribution of the carrier is more uniform in the fluidized bed, and the velocity gradient along the axial and radial direction changes little. When the distribution plate A is set up, the distribution of the radial velocity of the carrier is obviously larger than that of the other distribution plates. The maximum radial velocity is 0.17m/s, and the collision and friction between the carrier particles in the radial direction is more intense. (3) in the case of the other initial conditions, the volume fraction and axial velocity of the carrier in the fluidized bed decrease with the increase of the carrier particle size, and the expansion height of the bed layer decreases obviously, the velocity uniformity and the flow state of the fluidized bed are all worse. With the increase of carrier density, the volume fraction of carrier in the fluidized bed becomes larger, the expansion rate and axial velocity of bed layer decrease, the velocity uniformity becomes worse and the flow state becomes unstable. With the increase of the initial filling height of the carrier, the volume fraction of carrier in the fluidized bed is correspondingly larger, the axial velocity decreases, the bed expansion rate has small amplitude fluctuation and the flow velocity is uniform. With the increase of the liquid velocity at the entrance of the fluidized bed, the volume fraction of the carrier in the fluidized bed decreases, the bed expansion rate and the axial velocity are obviously increased and the velocity uniformity becomes worse. (4) the analysis and comparison of the carrier volume fraction in the fluidized bed, the axial velocity distribution of the carrier and the non uniform velocity coefficient of the flow velocity are compared. The density of the body particles is 1500kg/m3, the carrier particle size is 1mm, the initial filling height is 0.3m, and the liquid velocity at the inlet of the fluidized bed is 0.15m/S, which is the best carrier property and operating parameter for the given biological fluidized bed. It is the most favorable for improving the efficiency of the sewage treatment in the fluidized bed.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X703
本文編號：2166622
[Abstract]:With the development of economy and society, environmental problems have become one of the most important problems that restrict the development of our society. In many environmental problems, water pollution is the most prominent and serious problem. In particular, the rapid development of the city has produced a large number of domestic sewage, and most of these domestic sewage are not treated directly to the water in the natural world. In the body, it has caused serious pollution to the environment of rivers, lakes and oceans. It is very difficult to restore to the natural state. Water resources in our country are not rich, and the pollution of various water bodies will make the available water resources further reduced, affecting the people's normal life and the production of industry and agriculture. To realize the sustainable benefit of water resources. It is necessary to purify industrial and domestic sewage and develop a complete set of economical and practical sewage treatment equipment and methods. In many sewage treatment methods, the biofilm sewage treatment technology is one of the most important sewage treatment methods because of its convenient operation and low operating cost. This paper uses RNG k- e turbulence. The flow model is combined with the Euler Orla multiphase flow model to simulate a typical fluid flow dynamic fluidized bed. A variety of physical quantities are compared in the opening form of different distributed plates, thus the pore form of a reasonable fluidized bed inlet distribution plate is determined, and the solid volume in the fluidized bed is analyzed under the different carrier properties and operating conditions. The physical parameters such as fraction, flow flow, turbulent kinetic energy and turbulent energy dissipation rate have been determined, and the optimal operating parameters of the fluidized bed are determined. The advantages and disadvantages of different operating conditions are found, so that readers can choose the distribution pattern of distribution plates suitable for their own working conditions according to their needs, the carrier and the operating parameters. Through analysis and comparison, the following conclusions are drawn. (1) through the comparison and analysis of the model verification one, it is found that the Euler Euler multiphase flow model can be used to simulate the solid and liquid two phase flow in the fluidized bed with the RNGk- epsilon turbulence model. Through the model verification, two models of the selected multiphase flow, the turbulence model and its boundary conditions and numerical solution methods are verified, the simulation values and the experiments are carried out. The data are in good agreement, and the mathematical model, numerical solution and boundary condition can be used to simulate the flow characteristics of solid-liquid two-phase flow in the fluidized bed. (2) the carrier particles in the fluidized bed are completely fluidizing in the fluidized bed, forming a homogeneous flow layer, and there is no local flow layer. (2) compared with other forms of carrier distribution plate, the carrier particles are in the fluidized bed. In the high concentration region, the axial concentration fluctuates but is not obvious, the concentration distribution in the fluidized bed is the most uniform. The axial velocity distribution of the carrier is more uniform in the fluidized bed, and the velocity gradient along the axial and radial direction changes little. When the distribution plate A is set up, the distribution of the radial velocity of the carrier is obviously larger than that of the other distribution plates. The maximum radial velocity is 0.17m/s, and the collision and friction between the carrier particles in the radial direction is more intense. (3) in the case of the other initial conditions, the volume fraction and axial velocity of the carrier in the fluidized bed decrease with the increase of the carrier particle size, and the expansion height of the bed layer decreases obviously, the velocity uniformity and the flow state of the fluidized bed are all worse. With the increase of carrier density, the volume fraction of carrier in the fluidized bed becomes larger, the expansion rate and axial velocity of bed layer decrease, the velocity uniformity becomes worse and the flow state becomes unstable. With the increase of the initial filling height of the carrier, the volume fraction of carrier in the fluidized bed is correspondingly larger, the axial velocity decreases, the bed expansion rate has small amplitude fluctuation and the flow velocity is uniform. With the increase of the liquid velocity at the entrance of the fluidized bed, the volume fraction of the carrier in the fluidized bed decreases, the bed expansion rate and the axial velocity are obviously increased and the velocity uniformity becomes worse. (4) the analysis and comparison of the carrier volume fraction in the fluidized bed, the axial velocity distribution of the carrier and the non uniform velocity coefficient of the flow velocity are compared. The density of the body particles is 1500kg/m3, the carrier particle size is 1mm, the initial filling height is 0.3m, and the liquid velocity at the inlet of the fluidized bed is 0.15m/S, which is the best carrier property and operating parameter for the given biological fluidized bed. It is the most favorable for improving the efficiency of the sewage treatment in the fluidized bed.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X703
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