攪拌式厭氧發(fā)酵反應(yīng)器的CFD模擬及應(yīng)用研究
發(fā)布時間：2018-07-28 08:56
【摘要】：厭氧發(fā)酵技術(shù)是廢棄物資源化利用的核心技術(shù)之一,具有廣闊的應(yīng)用前景。本文以計算流體力學(xué)(CFD)為研究方法,系統(tǒng)研究了厭氧發(fā)酵體系物料混合過程的流體力學(xué)特征,為合理的工藝參數(shù)值選取及工業(yè)應(yīng)用提供依據(jù)。本文選擇玉米秸稈和牛糞的厭氧發(fā)酵體系為目標,建立了基于CFD的攪拌式厭氧發(fā)酵反應(yīng)器數(shù)學(xué)模型;從物料性質(zhì)、攪拌槳種類、攪拌設(shè)計參數(shù)等方面,模擬研究了攪拌混合體系的流場分布、固相濃度分布,以及發(fā)酵體系的能量產(chǎn)出與消耗。開展的創(chuàng)新性研究工作及取得的成果如下:首先,針對所研究的多相攪拌發(fā)酵反應(yīng)器,建立了固(F)-固(S)-液三相CFD模型,通過速度場、矢量分布和局部顆粒濃度的對比,驗證了所建CFD模型的可靠性;模擬研究了顆粒密度、顆粒直徑和固體含量等因素對固相濃度分布的影響,結(jié)果表明,當(dāng)顆粒密度大于液相時,固體會在反應(yīng)器底部圍繞釜底中心位置發(fā)生沉積;反之,則在近液面處圍繞攪拌軸發(fā)生上浮積聚。顆粒的上浮和下沉現(xiàn)象隨固體顆粒直徑的增大而加劇;隨著下沉顆粒S固含量由2.5%提高到10%,顆粒濃度的標準偏差變小,總體懸浮狀況變好。之后,通過對所研究三相體系中RB槳、HE槳、PBU槳和PBD槳的數(shù)值模擬,研究了攪拌槳種類及其設(shè)計參數(shù)(攪拌槳直徑、離底高度、葉片寬度)對流場的影響,得到了不同攪拌體系內(nèi)流場的分布規(guī)律。研究結(jié)果表明,在攪拌反應(yīng)器內(nèi)采用不同槳型會產(chǎn)生不同的流場和流型:RB槳呈現(xiàn)典型的徑流槳特征;HE、PBU和PBD在特定的幾何結(jié)構(gòu)配置下,出現(xiàn)主循環(huán)和二次循環(huán)流;攪拌槳葉直徑變化直接導(dǎo)致釜內(nèi)流場速度和流型均發(fā)生變化;攪拌槳離釜底高度變化,導(dǎo)致流場的排出位置隨之改變:HE和PBD槳離底高度降低抑制了二次循環(huán)流,PBU槳的離底高度降低影響主循環(huán)流;葉片寬度變化直接影響流場速度分布,但流型不變。在湍流流域內(nèi),RB槳的功率準數(shù)Np最大,是PBU和PBD槳的1.6倍,HE槳的3.2倍。第三,系統(tǒng)研究了上述四種攪拌槳及其設(shè)計參數(shù)對固-固-液混合流場固相分布的影響,得到了上浮和下沉顆粒共存體系內(nèi)固相分布規(guī)律:在攪拌槳下部反應(yīng)釜的中心區(qū)域顆粒S發(fā)生沉積,顆粒F在液面附近圍繞攪拌軸的中心區(qū)域發(fā)生積聚,顆粒S在流場中的混勻性優(yōu)于顆粒F;軸向流動速度增大利于固體顆粒的均勻懸浮。隨著攪拌轉(zhuǎn)速的增加,上浮顆粒F和下沉顆粒S的懸浮均勻性提高。當(dāng)轉(zhuǎn)速為210 rpm時,固相F的混合優(yōu)劣順序為PBU PBD HE RB,而固相S的混合優(yōu)劣順序為PBD≈PBURBHE。在PBU攪拌體系中,根據(jù)CFD切線交匯法模擬得到上浮顆粒F和下沉顆粒S的臨界懸浮轉(zhuǎn)速分別為119 rpm和117 rpm,并分別推導(dǎo)出三相體系中下沉顆粒的臨界離底懸浮轉(zhuǎn)速Njs和上浮顆粒的臨界下拉懸浮轉(zhuǎn)速Njd的關(guān)聯(lián)方程。第四,建立CFD模擬與析因分析相結(jié)合的方法,以攪拌槳直徑、離底距離、槳葉寬度為設(shè)計因子,以上浮顆粒的懸浮質(zhì)量σF、下沉顆粒的懸浮質(zhì)量σS和能量輸入MEL為響應(yīng)值,經(jīng)過系列化模擬研究,分別確定了四種攪拌體系中上浮顆粒與下沉顆粒懸浮質(zhì)量的顯著影響因子,并建立了攪拌槳設(shè)計因子與響應(yīng)值間的關(guān)聯(lián)方程。更加深入的模擬研究結(jié)果表明,在四種攪拌體系中,顯著影響上浮顆粒/下沉顆粒懸浮質(zhì)量的設(shè)計因子各自不同;而影響攪拌槳輸入功率的設(shè)計因子均為槳葉直徑、槳葉寬度和二者的交互作用值。對比PBD槳和RB槳的CFD模擬值與關(guān)聯(lián)方程預(yù)測值,誤差在1.6%～8.6%范圍,關(guān)聯(lián)方程可信�；谏鲜龇治鼋⒘笋詈夕褾、σS和MEL三個響應(yīng)值的無因次優(yōu)化函數(shù),并據(jù)此獲得了四種攪拌槳體系中適合固-固-液三相體系的最優(yōu)設(shè)計方案:采用PBU攪拌槳,槳葉直徑、離底距離和槳葉寬度分別控制在0.1 m、0.078 m和0.04 m。最后,建立了一個適合厭氧發(fā)酵非牛頓體系的攪拌反應(yīng)器數(shù)值模型,對玉米秸稈(CS)和牛糞(CM)的單一發(fā)酵體系及兩者混合發(fā)酵體系的流場和能量消耗進行深入研究,提出了“凈能量產(chǎn)出”指數(shù)概念,并獲得了相應(yīng)表達式。研究發(fā)現(xiàn),在CS和CM單一發(fā)酵體系和二者混合發(fā)酵體系(CS+CM)反應(yīng)器內(nèi)流場的均勻程度為:CM CS+CM CS;本文提出的“凈能量產(chǎn)出”指數(shù)可以用來優(yōu)化發(fā)酵體系的投料比,對于連續(xù)攪拌、間歇攪拌INTER Ⅰ、間歇攪拌INTER Ⅱ三種攪拌方式的最優(yōu)投料比分別為1:1,1:1和1:3。混合發(fā)酵體系的能量產(chǎn)出可以通過優(yōu)化攪拌形式和投料比來提高。
[Abstract]:Anaerobic fermentation technology is one of the core technologies of waste resource utilization and has a broad application prospect. In this paper, the hydrodynamic characteristics of the material mixing process in anaerobic fermentation system are systematically studied by using computational fluid dynamics (CFD). This paper provides a basis for the selection of reasonable process parameters and the application of industrial application. The anaerobic fermentation system of stalk and cow dung is the goal. A mathematical model of stirred anaerobic fermentation reactor based on CFD is established. The flow field distribution, the distribution of solid state concentration and the energy production and consumption of the fermentation system are simulated and studied in the aspects of the material properties, the type of agitator and the parameters of the mixing design. The results are as follows: firstly, a solid (F) - solid (S) - liquid three phase CFD model is established for the multiphase stirred fermentation reactor studied. The reliability of the built CFD model is verified by the velocity field, the vector distribution and the local particle concentration, and the particle density, the particle diameter and the solid content are studied in the simulation. The effect of concentration distribution shows that when the particle density is larger than the liquid phase, the solid will be deposited around the bottom of the reactor at the bottom of the reactor, and on the contrary, the floating and the sinking of the particles are increased with the increase of the solid particle diameter at the near liquid surface. With the solid content of the sinking particle S, the solid content is raised by 2.5%. As high as 10%, the standard deviation of the particle concentration is smaller and the overall suspension condition becomes better. After the numerical simulation of the RB paddles, HE paddles, PBU paddles and PBD paddles in the three phase system, the influence of the type of impeller and its design parameters (impeller diameter, bottom height and blade width) on the flow field is studied, and the flow field in different mixing systems is obtained. The distribution rule. The results show that different flow fields and flow patterns are produced in the mixing reactor: RB propeller presents typical characteristics of runoff propeller; HE, PBU and PBD appear main circulation and two circulation flow under specific geometric configuration; the change of impeller diameter changes directly in the flow velocity and flow pattern in the reactor; The change of the height of the agitator at the bottom of the tank leads to the change of the discharge position of the flow field. The height of the HE and PBD oars decreases with the decrease of the two circulation flow, and the decrease of the height of the PBU paddle affects the main circulation. The blade width change directly affects the velocity distribution of the flow field, but the flow pattern is unchanged. In the turbulent basin, the maximum power of the RB paddle is Np, which is a PBU and PBD oar. 1.6 times and 3.2 times of HE paddle. Third. The effects of the above four agitators and their design parameters on the solid solid liquid mixed flow field are studied. The solid phase distribution in the coexistence system of the upper floating and sinking particles is obtained. The particle S is deposited in the central region of the bottom reaction kettle of the stirred propeller, and the particle F is around the mixing axis near the liquid surface. The agglomeration of the central region occurs. The mixing of particle S in the flow field is better than that of the particle F, and the axial flow velocity increases for the uniform suspension of solid particles. With the increase of the stirring speed, the suspension uniformity of the floating particles F and the sinking particle S increases. When the rotational speed is 210 rpm, the sequence of the mixing of the solid phase F is PBU PBD HE RB, while the solid phase S is the same. The sequence of mixing is PBD PBURBHE. in the PBU mixing system. The critical suspension speed of the floating particles F and the sinking particle S is 119 rpm and 117 RPM respectively according to the CFD tangent intersection method. The correlation between the critical off bottom suspension speed Njs and the critical drop off speed Njd of the floating particles in the three-phase system is deduced respectively. Fourth, the method of combining the CFD simulation with the factorial analysis is established, with the diameter of the impeller, the distance from the bottom, the blade width as the design factor, the suspended mass of the floating particles, the suspended mass of the floating particles, the mass of the suspended particles Sigma S and the energy input MEL as the response value. After a series of simulation studies, the floating particles in the four kinds of mixing systems are determined respectively. The correlation equation between the design factor of the impeller and the response value is established. The more in-depth simulation results show that in the four kinds of mixing systems, the design factors that significantly affect the suspension mass of the floating particles and the suspended particles are different, and the design factors that affect the input power of the agitation propeller Both the diameter of the blade, the width of the blade and the interaction value of the two, compared the CFD simulation value of the PBD paddle and the RB paddle with the predictive value of the correlation equation, the error is 1.6% to 8.6%, the correlation equation is credible. Based on the above analysis, the dimensionless optimization functions of the three response values of the coupling Sigma F, sigma S and MEL are established, and the suitable four kinds of stirred oar systems are obtained accordingly. The optimal design scheme of solid solid liquid three phase system: using PBU mixing paddle, blade diameter, bottom distance and blade width controlled at 0.1 M, 0.078 m and 0.04 M., a numerical model of stirred reactor suitable for anaerobic fermentation and non Newtonian system, a single fermentation system for corn straw (CS) and cow dung (CM) and their mixed hair, was established. The flow field and energy consumption of the fermentation system are deeply studied. The concept of "net energy output" is proposed and the corresponding expression is obtained. It is found that the uniformity of the flow field in the CS and CM single fermentation system and the two mixed fermentation system (CS+CM) reactor is CM CS+CM CS, and the "net energy output" index proposed in this paper can be used in this paper. In order to optimize the feeding ratio of the fermentation system, the energy output of the mixed fermentation system of 1:1,1:1 and 1:3. is improved by optimizing the mixing form and feeding ratio for the continuous stirring, intermittent stirring INTER I and the optimal feeding ratio of the batch mixing INTER II three mixing methods respectively.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：X71
[Abstract]:Anaerobic fermentation technology is one of the core technologies of waste resource utilization and has a broad application prospect. In this paper, the hydrodynamic characteristics of the material mixing process in anaerobic fermentation system are systematically studied by using computational fluid dynamics (CFD). This paper provides a basis for the selection of reasonable process parameters and the application of industrial application. The anaerobic fermentation system of stalk and cow dung is the goal. A mathematical model of stirred anaerobic fermentation reactor based on CFD is established. The flow field distribution, the distribution of solid state concentration and the energy production and consumption of the fermentation system are simulated and studied in the aspects of the material properties, the type of agitator and the parameters of the mixing design. The results are as follows: firstly, a solid (F) - solid (S) - liquid three phase CFD model is established for the multiphase stirred fermentation reactor studied. The reliability of the built CFD model is verified by the velocity field, the vector distribution and the local particle concentration, and the particle density, the particle diameter and the solid content are studied in the simulation. The effect of concentration distribution shows that when the particle density is larger than the liquid phase, the solid will be deposited around the bottom of the reactor at the bottom of the reactor, and on the contrary, the floating and the sinking of the particles are increased with the increase of the solid particle diameter at the near liquid surface. With the solid content of the sinking particle S, the solid content is raised by 2.5%. As high as 10%, the standard deviation of the particle concentration is smaller and the overall suspension condition becomes better. After the numerical simulation of the RB paddles, HE paddles, PBU paddles and PBD paddles in the three phase system, the influence of the type of impeller and its design parameters (impeller diameter, bottom height and blade width) on the flow field is studied, and the flow field in different mixing systems is obtained. The distribution rule. The results show that different flow fields and flow patterns are produced in the mixing reactor: RB propeller presents typical characteristics of runoff propeller; HE, PBU and PBD appear main circulation and two circulation flow under specific geometric configuration; the change of impeller diameter changes directly in the flow velocity and flow pattern in the reactor; The change of the height of the agitator at the bottom of the tank leads to the change of the discharge position of the flow field. The height of the HE and PBD oars decreases with the decrease of the two circulation flow, and the decrease of the height of the PBU paddle affects the main circulation. The blade width change directly affects the velocity distribution of the flow field, but the flow pattern is unchanged. In the turbulent basin, the maximum power of the RB paddle is Np, which is a PBU and PBD oar. 1.6 times and 3.2 times of HE paddle. Third. The effects of the above four agitators and their design parameters on the solid solid liquid mixed flow field are studied. The solid phase distribution in the coexistence system of the upper floating and sinking particles is obtained. The particle S is deposited in the central region of the bottom reaction kettle of the stirred propeller, and the particle F is around the mixing axis near the liquid surface. The agglomeration of the central region occurs. The mixing of particle S in the flow field is better than that of the particle F, and the axial flow velocity increases for the uniform suspension of solid particles. With the increase of the stirring speed, the suspension uniformity of the floating particles F and the sinking particle S increases. When the rotational speed is 210 rpm, the sequence of the mixing of the solid phase F is PBU PBD HE RB, while the solid phase S is the same. The sequence of mixing is PBD PBURBHE. in the PBU mixing system. The critical suspension speed of the floating particles F and the sinking particle S is 119 rpm and 117 RPM respectively according to the CFD tangent intersection method. The correlation between the critical off bottom suspension speed Njs and the critical drop off speed Njd of the floating particles in the three-phase system is deduced respectively. Fourth, the method of combining the CFD simulation with the factorial analysis is established, with the diameter of the impeller, the distance from the bottom, the blade width as the design factor, the suspended mass of the floating particles, the suspended mass of the floating particles, the mass of the suspended particles Sigma S and the energy input MEL as the response value. After a series of simulation studies, the floating particles in the four kinds of mixing systems are determined respectively. The correlation equation between the design factor of the impeller and the response value is established. The more in-depth simulation results show that in the four kinds of mixing systems, the design factors that significantly affect the suspension mass of the floating particles and the suspended particles are different, and the design factors that affect the input power of the agitation propeller Both the diameter of the blade, the width of the blade and the interaction value of the two, compared the CFD simulation value of the PBD paddle and the RB paddle with the predictive value of the correlation equation, the error is 1.6% to 8.6%, the correlation equation is credible. Based on the above analysis, the dimensionless optimization functions of the three response values of the coupling Sigma F, sigma S and MEL are established, and the suitable four kinds of stirred oar systems are obtained accordingly. The optimal design scheme of solid solid liquid three phase system: using PBU mixing paddle, blade diameter, bottom distance and blade width controlled at 0.1 M, 0.078 m and 0.04 M., a numerical model of stirred reactor suitable for anaerobic fermentation and non Newtonian system, a single fermentation system for corn straw (CS) and cow dung (CM) and their mixed hair, was established. The flow field and energy consumption of the fermentation system are deeply studied. The concept of "net energy output" is proposed and the corresponding expression is obtained. It is found that the uniformity of the flow field in the CS and CM single fermentation system and the two mixed fermentation system (CS+CM) reactor is CM CS+CM CS, and the "net energy output" index proposed in this paper can be used in this paper. In order to optimize the feeding ratio of the fermentation system, the energy output of the mixed fermentation system of 1:1,1:1 and 1:3. is improved by optimizing the mixing form and feeding ratio for the continuous stirring, intermittent stirring INTER I and the optimal feeding ratio of the batch mixing INTER II three mixing methods respectively.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：X71
【參考文獻】
相關(guān)期刊論文 前7條
1 王超;李園;李志鵬;高正明;;固液攪拌反應(yīng)器數(shù)值模擬研究進展[J];北京化工大學(xué)學(xué)報(自然科學(xué)版);2016年01期
2 高凱旋;;關(guān)于攪拌在沼氣發(fā)酵過程中的作用[J];中國沼氣;2015年03期
3 吳攀;夏敏;楊雄;皮科武;;基于Design-Expert構(gòu)建煙堿浸提率預(yù)測模型的研究[J];山東化工;2014年12期
4 閆金定;;我國生物質(zhì)能源發(fā)展現(xiàn)狀與戰(zhàn)略思考[J];林產(chǎn)化學(xué)與工業(yè);2014年04期
5 李良超;徐斌;楊軍;;基于計算流體力學(xué)模擬的下沉與上浮顆粒在攪拌槽內(nèi)的固液懸浮特性[J];機械工程學(xué)報;2014年12期
6 賈敬敦;孫康泰;蔣大華;魏s，
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