本文選題：氣固反應流 + 格子氣自動機　； 參考：《重慶大學》2015年碩士論文

【摘要】：氣固反應流是石油、化工以及冶金工業(yè)中常見的現(xiàn)象。由于大多數(shù)反應是一個復雜的非線性過程,其中包含了流動、傳熱、傳質(zhì)及化學反應等環(huán)節(jié),易受體系波動的影響,因此這一過程很難用標準方法從理論上加以有效分析。研究氣固反應流的方法包括實驗方法和數(shù)值模擬方法兩大類。由于實驗方法成本較高,且受到檢測手段的限制而難以獲得反應中的細節(jié)數(shù)據(jù),加之近些年來計算機技術(shù)的飛速發(fā)展,使得數(shù)值模擬方法開始成為與實驗方法同等重要的技術(shù)手段。氣固反應流數(shù)值模擬問題對反應器設(shè)計有重要作用,但由于研究問題的復雜性而成為反應器理論及應用研究的難點。目前,氣固反應流數(shù)值模擬方法通常從宏觀層面出發(fā),基于流動、傳質(zhì)、傳熱及反應相關(guān)過程的耦合建立數(shù)理模型或半經(jīng)驗模型,采用計算流體動力學(Computational Fluid Dynamics,CFD)中的有限差分、有限體積等方法對模型求解,涉及到流動、傳質(zhì)、傳熱以及反應等環(huán)節(jié)的復雜耦合,并且在邊界處理、算法設(shè)計以及并行處理上較為困難。而格子氣自動機(Lattice Gas Automata,LGA)是一種在介觀層面上基于時間、空間以及流體離散的簡化分子動力學模型,既具有微觀方法下假設(shè)條件較少的特點,又具有宏觀方法難以涉及分子或粒子層次微觀細節(jié)的優(yōu)勢,并可通過模型演化和統(tǒng)計而得到體系在宏觀上的非線性行為,整個過程以離散粒子的一系列自組織演化規(guī)則替代了對機理模型的復雜求解,并且在處理復雜邊界以及反應流中各環(huán)節(jié)的耦合方面也顯得更為高效。為模擬氣固相反應流問題,本文根據(jù)固體顆粒的未反應核理論,基于格子氣自動機方法,構(gòu)建了包含多物質(zhì)、多能量狀態(tài)的氣固反應流LGA模型。通過對不同組分、不同能量狀態(tài)的氣體粒子的屬性標記,根據(jù)物質(zhì)組分的濃度梯度設(shè)計了碰撞方式選擇概率表達式,以控制多種物質(zhì)粒子間的擴散遷移,并引入了熱交換過程的能量傳遞規(guī)則;參照反應速率方程結(jié)構(gòu),設(shè)計了氣固反應的概率表達式,并依照熱力學原理進行了反應熱效應的量化描述。以Visual Studio 2005為平臺開發(fā)了氣固反應流模型的仿真軟件,實現(xiàn)了反應過程的人機交互以及模擬結(jié)果的可視化,為模擬結(jié)果的定量分析提供了幫助。根據(jù)文獻中Bohna等人的實驗條件,分別在等溫和非等溫條件下,利用所建立的氣固反應流LGA模型模擬了CO與Fe2O3顆粒還原生成Fe3O4的過程,結(jié)果表明:在同一時刻,與等溫條件相比,非等溫條件下反應轉(zhuǎn)化率平均提高了約6.92%,且模擬結(jié)果位于Bohna實驗結(jié)果的誤差上下限范圍內(nèi),所建立的反應流模型有效;同時,反應流模型能夠有效地描述出反應過程中的速度場、溫度場以及濃度場的變化細節(jié)。此外,在此基礎(chǔ)上還分別模擬了不同反應條件下CO與Fe2O3顆粒的還原反應過程,結(jié)果表明:氣體溫度、濃度、顆粒粒徑以及孔隙率對顆粒反應過程均有顯著性影響。構(gòu)造具有不同空隙率的Fe2O3多顆粒體系,利用反應流模型模擬了CO與Fe2O3多顆粒體系的還原反應過程,并對體系中的速度場、溫度場以及濃度場分布情況進行了研究分析。結(jié)果表明:反應流模型可以有效地捕捉到多顆粒體系中的流動、傳質(zhì)、傳熱以及反應等細節(jié);多顆粒體系中的反應過程具有不均勻性,增大流體流速以及空隙率有利于提高整個體系的反應效率,這與客觀規(guī)律是相一致的。構(gòu)造填充床反應器,床中采用隨機方法生成一系列大小不一、位置分布不均勻的Fe2O3固體顆粒群體,采用反應流模型模擬了床中的反應過程。結(jié)果表明:受壁面效應、固體顆粒體系分布以及傳熱、熱效應規(guī)則的影響,床層中的速度場、溫度場以及濃度場的分布呈現(xiàn)出不均勻性。此外,在此基礎(chǔ)上,根據(jù)實際冶金填充床中的黑白像素圖,模擬了填充床中局部的反應過程,并成功得到了其中反應流現(xiàn)象。
[Abstract]:Gas-solid reaction flow is a common phenomenon in petroleum, chemical and metallurgical industries. Because most reactions are a complex nonlinear process, including flow, heat transfer, mass transfer and chemical reactions, it is easily affected by the fluctuation of the system. Therefore, it is difficult to analyze the gas solid reaction in theory by the standard method. The method of flow includes two kinds of methods: the experimental method and the numerical simulation method. Because of the high cost of the experiment method and the restriction of the detection means, it is difficult to obtain the detailed data in the reaction. In addition, the rapid development of computer technology in recent years makes the numerical simulation method become the same important technical means as the experimental method. The problem of flow numerical simulation plays an important role in the design of reactor. However, due to the complexity of the research problems, it has become a difficult problem in the theoretical and applied research of the reactor. At present, the numerical simulation method of gas solid reaction flow is usually based on the macro level, based on the coupling of flow, mass transfer, heat transfer and reaction related processes to establish a mathematical model or a semi empirical model. The model is solved by finite difference and finite volume method in Computational Fluid Dynamics (CFD). It involves complex coupling of flow, mass transfer, heat transfer and reaction, and it is difficult to deal with boundary processing, algorithm design and parallel processing. The lattice gas automata (Lattice Gas Automata, L) GA) is a simplified molecular dynamics model based on time, space and fluid dispersion at the mesoscopic level. It has the characteristics of less hypothetical conditions under the microscopic method, but also has the advantage that macro methods are difficult to involve the microcosmic details of molecular or particle levels, and can be obtained by model evolution and statistics. The whole process takes a series of self organized evolution rules of discrete particles to replace the complex solution of the mechanism model, and is more efficient in dealing with complex boundary and coupling of each link in the reaction flow. The LGA model of gas solid reaction flow including multi matter and multi energy state is constructed. By marking the properties of different components and energy states, the probability expression of the selection probability is designed according to the concentration gradient of the material components to control the diffusion and transfer between various material particles, and the heat exchange process is introduced. According to the reaction rate equation structure, the probability expression of gas solid reaction is designed, and the quantitative description of the reaction heat effect is described in accordance with the principle of thermodynamics. The simulation software of the gas solid reaction flow model is developed with Visual Studio 2005 as the platform. The human-computer interaction and the visualization of the simulation results are realized. According to the experimental conditions of Bohna et al. In the literature, the LGA model of gas solid reaction flow is used to simulate the reduction of CO and Fe2O3 particles by the established gas solid reaction flow model under the conditions of the isothermal and non isothermal conditions. The results show that, at the same moment, the reaction is compared with the isothermal condition in the same temperature condition. The average increase of the rate is about 6.92%, and the simulation results are within the range of the error of the Bohna experiment. The model of the reaction flow is effective. At the same time, the reaction flow model can describe the velocity field, the temperature field and the concentration field in the reaction process effectively. In addition, the different reaction strips are simulated on this basis. The reduction reaction process of CO and Fe2O3 particles shows that the gas temperature, concentration, particle size and porosity have significant effects on the reaction process. The structure has a Fe2O3 multi particle system with different void fraction, and the reaction flow model is used to simulate the reduction reaction process of CO and Fe2O3 multiple grain systems, and the velocity in the system is also simulated. The field, the temperature field and the distribution of the concentration field have been studied and analyzed. The results show that the reaction flow model can effectively capture the details of flow, mass transfer, heat transfer and reaction in the multi particle system, and the reaction process in the multi particle system is inhomogeneity, and the increase of the flow velocity and the void ratio is beneficial to the improvement of the reaction of the whole system. Efficiency, this is in accordance with the objective law. In a packed bed reactor, a random method is used to generate a series of Fe2O3 solid particle groups with different size and uneven distribution. The reaction flow model is used to simulate the reaction process in the bed. The results show that the effect of wall surface effect, the distribution of solid particle system and heat transfer, the rule of heat effect. The velocity field, the temperature field and the distribution of the concentration field in the bed are not uniform. On the basis of this, according to the black and white pixels in the actual metallurgical packed bed, the local reaction process in the packed bed is simulated, and the reaction flow phenomenon is successfully obtained.
【學位授予單位】：重慶大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ052

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