本文選題：微觀混合　切入點(diǎn)：攪拌槽反應(yīng)器　出處：《中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院過(guò)程工程研究所)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：攪拌槽作為工業(yè)上廣泛使用的混合設(shè)備,其內(nèi)部的流動(dòng)和傳遞特性將直接關(guān)系到產(chǎn)品的特性以及生產(chǎn)過(guò)程的經(jīng)濟(jì)性。對(duì)于混合敏感的快速?gòu)?fù)雜反應(yīng)過(guò)程,如果加入攪拌槽的物料無(wú)法快速地實(shí)現(xiàn)分子尺度的混合,那么進(jìn)料位置處反應(yīng)物的局部混合狀態(tài)將會(huì)決定主產(chǎn)物收率、產(chǎn)品質(zhì)量以及操作穩(wěn)定性。因此,深入了解攪拌槽內(nèi)各尺度的混合特性,尤其是直接影響化學(xué)反應(yīng)進(jìn)程的微觀混合,將有助于工業(yè)規(guī)模反應(yīng)器的設(shè)計(jì)、工程放大、操作優(yōu)化及過(guò)程強(qiáng)化�；诖�,本文采用數(shù)值模擬方法對(duì)單相以及多相攪拌槽內(nèi)湍流反應(yīng)流進(jìn)行了系統(tǒng)的研究,考察了微觀混合對(duì)混合敏感的化學(xué)反應(yīng)體系選擇性的影響,并將模型方法應(yīng)用到實(shí)際反應(yīng)體系及其現(xiàn)象的分析。具體工作以及主要成果如下:(1)使用混合分?jǐn)?shù)及其方差描述了物料宏觀以及微觀尺度的離集狀況,提出了一種CFD耦合卷吸模型(E-model)的新方法,數(shù)值研究了單進(jìn)料、半連續(xù)攪拌槽內(nèi)微觀混合對(duì)酸堿中和/氯乙酸乙酯水解平行競(jìng)爭(zhēng)反應(yīng)體系以及碘化物/碘酸鹽平行競(jìng)爭(zhēng)反應(yīng)體系選擇性的影響。結(jié)果表明,本文提出的CFD耦合卷吸模型的新方法可以很好地預(yù)測(cè)出離集指數(shù)隨攪拌轉(zhuǎn)速、進(jìn)料位置、進(jìn)料濃度等條件的變化,且該方法的模型方程簡(jiǎn)單、計(jì)算時(shí)間短,不需要任何實(shí)驗(yàn)數(shù)據(jù)作為模型參數(shù),適用于工業(yè)規(guī)模反應(yīng)器的診斷和優(yōu)化。(2)基于"Eulerian-Eulerian"的多流體模型觀點(diǎn),將本文提出的適用于均相體系的CFD耦合卷吸模型的新方法進(jìn)行了擴(kuò)展,數(shù)值研究了氣液以及固液攪拌槽內(nèi)微觀混合對(duì)碘化物/碘酸鹽平行競(jìng)爭(zhēng)反應(yīng)體系選擇性的影響。采用歐拉多相流模型以及k-ε多相湍流模型數(shù)值計(jì)算流場(chǎng),在模擬氣液宏觀流場(chǎng)時(shí)還添加了可變氣泡尺寸模型。結(jié)果表明,針對(duì)多相體系擴(kuò)展得到的CFD耦合卷吸模型的新方法,可以較好地預(yù)測(cè)出離集指數(shù)隨惰性相相含率、攪拌轉(zhuǎn)速、進(jìn)料位置等條件的變化。對(duì)于氣液攪拌槽,增加氣速可以顯著增加液面附近流體的湍動(dòng)程度,使得每一份進(jìn)料的消耗時(shí)間縮短,但對(duì)于靠近槳葉附近的進(jìn)料位置,氣速對(duì)離集指數(shù)的影響較小;對(duì)于固液攪拌槽,相含率很高時(shí)形成固體云,在清液層進(jìn)料時(shí),離集指數(shù)顯著增大。(3)基于CFD耦合卷吸模型,通過(guò)求解平均混合分?jǐn)?shù)及其方差的輸運(yùn)方程,數(shù)值研究了攪拌槽進(jìn)料管的返混,定性地描述了返混發(fā)生時(shí)進(jìn)料管出口附近物料流動(dòng)和混合特征。結(jié)果表明,當(dāng)進(jìn)料管發(fā)生返混時(shí),從速度矢量圖上可以清晰看到管口處產(chǎn)生旋渦,且旋渦尺寸隨著返混程度的增加而增大,返混最嚴(yán)重時(shí)旋渦占據(jù)了整個(gè)進(jìn)料管出口;從平均混合分?jǐn)?shù)及其方差分布圖可以看到,返混發(fā)生時(shí),進(jìn)料管出口內(nèi)側(cè)混合分?jǐn)?shù)值明顯小于1,方差最大值所在的區(qū)域也位于進(jìn)料管出口內(nèi),隨著進(jìn)料速度增加或者進(jìn)料管直徑的減小,返混逐漸減弱,方差最大值所在的區(qū)域逐漸由管內(nèi)側(cè)轉(zhuǎn)移到管口外;不發(fā)生返混時(shí),方差最大值所在的區(qū)域即離集大的區(qū)域則位于管口外側(cè)。(4)將 CFD 耦合 DQMOM-IEM(Direct quadrature method of moments combining with the interaction by exchange with the mean micro-mixing model)微觀混合模型用于研究攪拌槽內(nèi)微觀混合對(duì)酸堿中和/氯乙酸乙酯水解平行競(jìng)爭(zhēng)反應(yīng)體系產(chǎn)物分布的影響。計(jì)算結(jié)果表明:DQMOM-IEM微觀混合模型可以成功地預(yù)測(cè)離集指數(shù)隨攪拌轉(zhuǎn)速以及進(jìn)料時(shí)間的變化。攪拌轉(zhuǎn)速越高,流體湍動(dòng)程度越大,充分的微觀混合抑制了副產(chǎn)物的生成;進(jìn)料時(shí)間越長(zhǎng),加入攪拌槽內(nèi)的新鮮物料越容易與攪拌槽內(nèi)反應(yīng)物充分混合,反應(yīng)區(qū)體積越小且越集中于進(jìn)料管出口,離集指數(shù)也越小。(5)采用CFD耦合DQMOM-IEM微觀混合模型,數(shù)值計(jì)算了攪拌槽內(nèi)的反應(yīng)PLIF(Planar laser-induced fluorescence)過(guò)程。針對(duì)該真實(shí)反應(yīng)體系的特征,詳細(xì)推導(dǎo)了以混合分?jǐn)?shù)和反應(yīng)進(jìn)度變量所表示的化學(xué)反應(yīng)過(guò)程,考察了攪拌槳轉(zhuǎn)速以及安裝高度對(duì)同時(shí)進(jìn)行的混合和快速化學(xué)反應(yīng)過(guò)程的影響。該方法不僅適用于反應(yīng)PLIF過(guò)程的計(jì)算,還可以數(shù)值模擬其他混合敏感的化學(xué)反應(yīng)體系。模擬結(jié)果表明:在獲得宏觀流場(chǎng)的基礎(chǔ)上,通過(guò)求解兩環(huán)境DQMOM-IEM微觀混合模型,成功地預(yù)測(cè)了反應(yīng)PLIF過(guò)程,獲得了熒光示蹤劑羅丹明B濃度的時(shí)空分布。隨著攪拌轉(zhuǎn)速的增加,物料混合速率加快,物理混合時(shí)間以及反應(yīng)混合時(shí)間均減小;改變攪拌槳的安裝高度,攪拌槽內(nèi)不同位置的湍動(dòng)程度以及流動(dòng)主體方向均會(huì)發(fā)生相應(yīng)變化,從而影響了反應(yīng)混合進(jìn)程。此外,如果在數(shù)值計(jì)算中不耦合微觀混合模型,則預(yù)測(cè)的反應(yīng)混合時(shí)間遠(yuǎn)小于實(shí)驗(yàn)值以及使用DQMOM-IEM模型獲得的模擬值,因此在對(duì)混合敏感的反應(yīng)體系進(jìn)行模擬時(shí),微觀混合作用顯著,添加微觀模型可以獲得更加準(zhǔn)確的預(yù)測(cè)結(jié)果。
[Abstract]:Mixing equipment in stirred tank is widely used as the industry, its internal flow and transfer characteristics will be directly related to the characteristics of products and production process of the economy. The rapid reaction process for mixed complex and sensitive, if adding stirring tank material can not achieve rapid mixing into scale, local mixing state will then feed the position of the reactants decided the main product yield, product quality and operation stability. Therefore, in-depth understanding of the mixing characteristics of each scale in a stirred tank, especially micro mixing directly affects the chemical reaction process, will be helpful to design, industrial scale reactor scale-up, operation optimization and process intensification. Based on this, this paper by using the numerical simulation method of single-phase and multiphase turbulent reacting flow in stirred tank were studied. Effects of micromixing on mixed sensitive chemical reaction system. Effect of selective, and the analysis model is applied to the actual reaction and phenomena. The specific work and main results are as follows: (1) using the mixture fraction and its variance is described from the set of materials macro and micro scale, proposes a CFD coupled entrainment model (E-model) of the new method, numerical study the single feed semi continuous stirred tank micro mixing of neutralization / ethyl chloroacetate hydrolysis parallel reaction system and iodide / iodate parallel competition selective reaction system. The results show that the CFD coupling the volume of new method of absorbing model can well predict the segregation index with stirring speed change, feed position, feed concentration and other conditions, the model equation and the method is simple, the computation time is short, do not need any experimental data as the model parameters for industrial scale reaction diagnosis and device Optimization. (2) based on the "Eulerian-Eulerian" model, a new method of CFD coupled to a homogeneous system entrainment model is proposed in this paper will be extended, numerical study of gas-liquid and Solid-Liquid Stirred Tank micro mixing of iodide / iodate parallel competitive selective reaction system. Using the European pull multiphase flow model and k- e turbulent multiphase numerical model in the simulation of gas-liquid flow field, macroscopic flow field also adds a variable bubble size model. The results show that the new method for CFD coupled system extended entrainment model, can better predict the segregation index with inert phase holdup, stirring change speed, feed location and other conditions. For the gas-liquid stirred tank, increase in gas velocity can significantly increase the level of fluid near the turbulence degree, makes every feed consumption time is shortened, but close to the blade of Feed location near, gas velocity has little effect on the segregation index; for Solid-Liquid Stirred Tank, phase holdup is very high in the clouds to form a solid, liquid feed layer, the segregation index increased significantly. (3) CFD coupled entrainment model based on the average and variance of the mixture fraction by solving the transport equation numerical study on the mixing tank, feeding back mixing tube, qualitatively describes the backmixing occurs when the feed pipe near the exit of material flow and mixing characteristics. The results show that when the feed back mixing tube, from the velocity vector diagram, you can clearly see the vortex nozzle, and the vortex size with backmixing the extent of the increase, mixing the most serious vortex occupies the entire feed pipe outlet; from the mean mixture fraction and its variance distribution map can be seen, backmixing occurs when the feeding pipe of the inner side of the outlet of mixed value is less than 1, the maximum variance region is located in the feed The outlet, with the decrease of feed rate increase or feed pipe diameter, mixing gradually weakened, the variance maximum value area gradually from inside the tube to tube mouth; no backmixing, variance maximum region from the region is located in the mouth outside the master. (4) CFD DQMOM-IEM (Direct quadrature method of coupled moments combining with the interaction by exchange with the mean micro-mixing model) model is used to study the micro mixing in a stirred tank of micromixing on neutralization / ethyl chloroacetate hydrolysis reaction system affect the parallel competing product distribution. The calculation results show that the DQMOM-IEM micro hybrid model can successfully predict the segregation index change the stirring speed and the feeding time. The stirring speed is higher, the greater the degree of fluid turbulence, micro mixing fully inhibited the formation of by-products; feed The longer, stirring fresh materials groove more easily fully mixed and stirred tank reaction, the reaction zone and the smaller and more concentrated in the feed outlet, the segregation index is smaller. (5) using CFD coupled DQMOM-IEM micro hybrid model, numerical calculation of the mixing reaction tank PLIF (Planar laser-induced fluorescence). According to the characteristics of the real reaction system, deduced the chemical reaction with the mixture fraction and the reaction progress variable is represented, the effects of stirring speed and installation height of mixed and rapid simultaneous reaction process. The calculation method is not only applicable to the reaction process of PLIF also, the numerical simulation of other mixed sensitive chemical reaction system. The simulation results show that: Based on the macroscopic flow field obtained by solving two DQMOM-IEM micro environment, hybrid model successfully predicts the reverse PLIF process, temporal and spatial distribution of fluorescent tracer rhodamine B concentration was obtained. With the increase of stirring speed, mixing speed, mixing time and mixing time of physical reaction decreased; change the installation height of the agitator tank in different position of the turbulence degree and the flow direction of the main body will change, thus affecting the the reaction mixture process. In addition, if not in the calculation of micro mixing in the numerical model of coupling reaction, mixing time prediction is much smaller than the experimental values and simulation values obtained using the DQMOM-IEM model, so the simulation of reaction system of mixed sensitive, micro mixing effect, adding micro model can obtain more accurate forecasting results.

【學(xué)位授予單位】：中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院過(guò)程工程研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ051.72

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