旋转带蒸馏塔的流体力学性能测试
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摘要
旋转带蒸馏技术是基于蒸馏技术和真空技术在上个世纪中期发展起来的,最初用于分析,近几年才发展成可以商业化分离的一种新型分离技术。这种技术具有等板高度值低、持液量小、压降小、分离效率高等优点,它能在高真空和高理论塔板数的条件下对液体状态下沸点很近或具有热敏性的混合物进行分离。蒸馏时旋转带在中空的塔中高速旋转,通过带片对塔壁面上液膜不断的刮擦作用使气液两相不断紧密接触,增加表面更新速度,可以达到极佳的分离效果。然而,目前人们对旋转带蒸馏的流体力学性能研究很少,率先对旋转带蒸馏装置进行基础理论研究,将会对了解这项先进的分离技术起到积极作用。
通过实验考察了旋转带蒸馏塔内由于液相的存在引起的压降随着旋转带转速、液相速度和气相速度的变化情况,并对塔内不同流动状态进行了分析研究,并分析所得数据得到恒持液量区、载液区压降的计算式。用计算流体力学软件Fluent模拟塔内压降值,比较模拟值与实验值,可以看出模拟值与实验值吻合良好。
通过实验研究塔内动持液量随气相速度、液相速度、旋转带转速等因素的变化;得出了气相载点速度与旋转带转速和液速的关系:随着旋转带转速的增大,在特定的液速下,气相的载点速度会变小,在转速较低时,这种趋势更明显;得出了塔内恒持液量区、载液区动持液量计算式,并将模拟值与实验值进行了比较,两者吻合良好。
采用Fluent软件对塔内液体的停留时间分布进行模拟。对于现有设备,旋转带适宜的转速为1000-2500rpm,在此范围内增加旋转带的转速,液相的平均停留时间增大,塔壁面同一横截面不同位置处液相停留时间分布均匀。平均停留时间随旋转带转速增大的趋势会变小;随液相进料速度的增大,液体的平均停留时间变小;液速越小,停留时间分布曲线分布越宽,峰值越低;气相速度的改变对液体停留时间的影响相对于液相进料速度而言,影响很小,其它条件不变的条件下,改变气相进料速度,平均停留时间会在1±7%范围内波动。并通过实验选取几种工况,验证了Fluent模拟的正确性。
Spinning band distillation technology has developed basing on the distillation and vacuum technologies since the middle period of last century, which was mainly applied for analyses then. Until recently, it has successfully gained commercial applications as a new separation technology. The spinning band column has advantages such as low HETP value (height equivalent to a theoretical plate), small holdup, low pressure drop, particularly high efficiency and so on. It has been widely used to separate liquid mixtures with approximate boiling points or thermo-sensitive substances. Both high vacuum and high numbers of theoretical plates could be achieved within this new device. When it worked, the spinning band rotated in the column at high speeds and wiped the liquid film on the column wall to make the effective liquid/gas contact possible, thus increasing surface renewal frequency to achieve higher separation efficiency. However, reports on the hydrodynamic capabilities of this device have not been available so far. So taking the lead in studying this apparatus would help us to know about this advanced technique.
The work investigated the change in pressure drop caused by the existence of liquid phase in spinning band column with varying the rotating speeds, liquid and gas flow rates, and the physical processes that underlay this behavior by experiments analyses. The flow regimes included pre-loading, loading and flooding. Correlations were developed for each regime and the simulation results were compared with the experiment and proved to be acceptable.
The dynamic holdup was studied. The influence of different operating parameters such as the gas and liquid velocity, the rotating speeds of the spinning band on the dynamic holdup were analyzed and the correlation of gas loading point with rotating speeds and liquid velocity was developed according to the experimental data. The gas loading point decreased at higher rotating speeds, which became more obvious at lower rotating speeds. The correlations of dynamic holdup were developed in the pre-loading, loading and flooding regimes. And the simulations were proved to be incredible to their experimental counterparts.
The liquid residence time distribution (RTD) in the column was simulated with Fluent. The appropriate rotating speeds were determined to be 1000-2500rpm in the currently available apparatus. Increasing the rotating speeds in the range of 1000rpm to 2500rpm, the liquid’s mean residence time became longer and the liquid film was more uniform at the same cross-section of the column. The mean residence time increased slowly as the increase of the rotating speeds. The mean liquid residence time decreased as the liquid velocity increased, and the shift and width of the RTD curves showed that, at lower liquid loads, the variation of the residence time was larger, and the residence time was longer than at higher flow rates. The influence of gas velocity on RTD was relatively small to the liquid velocity and the mean residence time fluctuated in the range of 1±7% changing gas velocity. And the simulation results accorded well with their experimental counterparts.
通过实验考察了旋转带蒸馏塔内由于液相的存在引起的压降随着旋转带转速、液相速度和气相速度的变化情况,并对塔内不同流动状态进行了分析研究,并分析所得数据得到恒持液量区、载液区压降的计算式。用计算流体力学软件Fluent模拟塔内压降值,比较模拟值与实验值,可以看出模拟值与实验值吻合良好。
通过实验研究塔内动持液量随气相速度、液相速度、旋转带转速等因素的变化;得出了气相载点速度与旋转带转速和液速的关系:随着旋转带转速的增大,在特定的液速下,气相的载点速度会变小,在转速较低时,这种趋势更明显;得出了塔内恒持液量区、载液区动持液量计算式,并将模拟值与实验值进行了比较,两者吻合良好。
采用Fluent软件对塔内液体的停留时间分布进行模拟。对于现有设备,旋转带适宜的转速为1000-2500rpm,在此范围内增加旋转带的转速,液相的平均停留时间增大,塔壁面同一横截面不同位置处液相停留时间分布均匀。平均停留时间随旋转带转速增大的趋势会变小;随液相进料速度的增大,液体的平均停留时间变小;液速越小,停留时间分布曲线分布越宽,峰值越低;气相速度的改变对液体停留时间的影响相对于液相进料速度而言,影响很小,其它条件不变的条件下,改变气相进料速度,平均停留时间会在1±7%范围内波动。并通过实验选取几种工况,验证了Fluent模拟的正确性。
Spinning band distillation technology has developed basing on the distillation and vacuum technologies since the middle period of last century, which was mainly applied for analyses then. Until recently, it has successfully gained commercial applications as a new separation technology. The spinning band column has advantages such as low HETP value (height equivalent to a theoretical plate), small holdup, low pressure drop, particularly high efficiency and so on. It has been widely used to separate liquid mixtures with approximate boiling points or thermo-sensitive substances. Both high vacuum and high numbers of theoretical plates could be achieved within this new device. When it worked, the spinning band rotated in the column at high speeds and wiped the liquid film on the column wall to make the effective liquid/gas contact possible, thus increasing surface renewal frequency to achieve higher separation efficiency. However, reports on the hydrodynamic capabilities of this device have not been available so far. So taking the lead in studying this apparatus would help us to know about this advanced technique.
The work investigated the change in pressure drop caused by the existence of liquid phase in spinning band column with varying the rotating speeds, liquid and gas flow rates, and the physical processes that underlay this behavior by experiments analyses. The flow regimes included pre-loading, loading and flooding. Correlations were developed for each regime and the simulation results were compared with the experiment and proved to be acceptable.
The dynamic holdup was studied. The influence of different operating parameters such as the gas and liquid velocity, the rotating speeds of the spinning band on the dynamic holdup were analyzed and the correlation of gas loading point with rotating speeds and liquid velocity was developed according to the experimental data. The gas loading point decreased at higher rotating speeds, which became more obvious at lower rotating speeds. The correlations of dynamic holdup were developed in the pre-loading, loading and flooding regimes. And the simulations were proved to be incredible to their experimental counterparts.
The liquid residence time distribution (RTD) in the column was simulated with Fluent. The appropriate rotating speeds were determined to be 1000-2500rpm in the currently available apparatus. Increasing the rotating speeds in the range of 1000rpm to 2500rpm, the liquid’s mean residence time became longer and the liquid film was more uniform at the same cross-section of the column. The mean residence time increased slowly as the increase of the rotating speeds. The mean liquid residence time decreased as the liquid velocity increased, and the shift and width of the RTD curves showed that, at lower liquid loads, the variation of the residence time was larger, and the residence time was longer than at higher flow rates. The influence of gas velocity on RTD was relatively small to the liquid velocity and the mean residence time fluctuated in the range of 1±7% changing gas velocity. And the simulation results accorded well with their experimental counterparts.
引文
[1] Lesesne S D, Lochte H L, Ind. Eng. Chem., Anal. Ed., 1938, 10, 450
[2] Pease W F, Gilbert A H, Arno Cahn, Improved stirrer and bearing for spinning band distillation columns, Anal. Chem., 1960, 32(7):894~895
[3] Freeman S J, Nerheim A G, A macro spinning-band distillation column, Anal. Chem., 1959, 31(11):1929~1930
[4] Baner R H, Barkenbus C, Roswell C A, A large spinning-band fractionating column for use with small quantities of liquids, Ind. Eng. Chem., 1940, 12(8):468~471
[5] Jentoft R E, Doty W R, Gouw T H, Spinning band distillation column still heads, Anal. Chem., 1969, 41(1):223~224
[6] Freeman S J, Nerheim A G, A Macro Spinning-Band Distillation Column, Anal. Chem., 1959, 31(11):1929
[7] Nerheim A G, Analytical Distillation in Miniature Columns: Design and Testing of Teflon Spinning Band, Anal. Chem., 1957, 29(10): 1546~1548
[8] Nerheim A G, Dinerstein R A, Analytical Distillation in Miniature Columns: Performance under Total and Partial Reflux, Anal. Chem., 1956, 28(6): 1029~1033
[9]许松林,王燕飞,新型分离技术—旋转带蒸馏,化工机械,2006, 33(4):191~194
[10] Baner R H, Barkenbus C, Roswell C A, A large spinning-band fractionating column for use with small quantities of liquids, Ind. Eng. Chem., 1940,12(8):468~471
[11] Nester R G, Spinning-band fractionation column, US Patent, 2712520, 1955-7-5
[12] Foster N G, Green L E, Anal. Chem., 1952,24,1869
[13] Birch S F, Gripp V, Nathan W S, Soc. Chem. Ind., 1947, 66,33~40
[14] Nester R G, Separator, US Patent, 3372095, 1968-3-5
[15] Nerheim A G, Fractionator with plastic spinning band, US Patent, 3080303, 1963-3-5
[16] Nerheim A G, Head for spinning band fractionator, US Patent, 2764534, 1956-9-5
[17] Mayo, Dana W, Pike, et al., Spinning band fractionating column, US Patent, 4770746, 1988-9-13
[18] Roark S, Roger R, Spinning band, US Patent, 5603809, 1997-2-18
[19] Roark S, Roger R, US Patent 5472574, 1995
[20] Gerhard Kl?sel, Opladen, Rotor for Thin Layer Evaporator. US Patent, 3423782.1963
[21] Nairmen Mina-Camilde, David L C, Carlos M I, FT-IR spectroscopy in liquid xenon solution, ab initio calculations, normal coordinate analysis, and vibrationalassignments of meso-2, 4-dichloropentane and racemic-2, 4-dichloropentane, Spectrochimica Acta Part A, 1998, 54: 419~437
[22] Manzanares C E, Reynolds D, Lewis E K, et al., Matrix isolation FT-IR, FT-Raman spectroscopy, conformational ab initio calculations, and vibrational frequencies of meso andracemic-2, 4-pentanediol, Journal of Molcular Structure, 2004, 689:183~190
[23] Petrov V A, Frederic D, Bruce E S, Quadricyclane-trermal cycloaddition to polyfluorinated carbonyl compounds A simple synthesis of polyfluorinated 3-oxatricyclo[4.2.1.02,5]non-7-enes, Journal of Fluorine Chemistry, 2004, 125:1543~1552
[24] Feiring A E, Rozen S, Wonchoba E R, Synthesis of arylperfluoroalkyl ethers by direct fluorination, Journal of Fluorine Chemistry, 1998, 89:31~34
[25] Hoffsommer, R B, Jr., M.S.thesis, Pennsylvania State University, 1956
[26] Nerheim A G, Improved Head and Flask for Miniature Distillation, Anal.Chem., 1959, 31(12):2114
[27] Murray K E, Amer J, A Modified Spinning-Band Column for Low Pressure Fractionation. Oil Chemists’Soc., 1951, 28(1):235~239
[28] Ralph G, Nester E, Spinning Band Still for Vacuum Operation, Anal. Chem., 1956, 28(2):278~279
[29]傅德熏,马延文,计算流体力学,北京:高等教育出版社, 2002
[30]刘顺隆,计算流体力学,哈尔滨:哈尔滨工程大学出版社, 1998
[31]杨友麒,项曙光,化工过程模拟与优化,北京:化学工业出版社,2006
[32]王瑞金,张凯,王刚,Fluent技术基础与应用实例,北京:清华大学出版社,2007
[33] Fluent Inc., FLUENT User’s Guide. Fluent Inc., 2003
[34] Fluent Inc., FLUENT User Defined Function Manual. Fluent Inc., 2003
[35] Fluent Inc., Gambit Modeling Guide. Fluent Inc., 2003
[36]王福军,计算流体动力学分析—CFD软件原理与应用,北京:清华大学出版社,2004
[37] Lanzani A, Journal of the American Oil Chemists’Society, 1994, 71(6): 609~614
[38] Versteeg H K, Malalasekera W, An Introduction to Computational Fluid Dynamics: The Finite Volume Method. Wiley, New York, 1995
[39] Schlichting H, Boundary Layer Theory,8th ed.McGrawHill, New York,1979
[40]陶文铨,数值传热学,西安:西安交通大学出版社,2001
[41] Shih T H, Liou W W, Shabbir A, e tal., A new eddy viscosity model for high Reynolds number turbulent flows, Comput Fluids., 1995,24(3):227~238 k ?ε
[42]董丽萍,旋转带蒸馏塔的计算流体力学模拟:[硕士学位论文],天津:天津大学,2007
[43] Xien X, Zhihai Z, Songjiang T, Study on catalytic distillation processes: Prediction of pressure drop and holdup in catalyst bed, Trans. IChemE (A), 1997,75, 625～629
[44]周爱月,化工数学,北京:化学工业出版社,2002
[45] Ludovic R, Isabelle H, Studies of gas-liquid flow through reactors internals using VOF simulation, Chem. Eng. Sci., 2001, 56: 6385～6391
[46]韩占忠,王敬,兰小平,FLUENT—流体工程仿真计算实例与应用,北京:北京理工大学出版社, 2004
[47]杨忠华,规整填料在多种压力条件下混合特性的实验研究:[硕士学位论文],天津:天津大学,2001
[48]戚以政,汪叔雄,生化反应动力学与反应器,北京:化学工业出版社,2003
[49]余国琮,黄洁,张泽庭等,大型塔板的液体停留时间分布与数学模型,天津大学学报,1985, NO.4:P1
[50]罗康碧,罗明河,李泸萍,反应工程原理,北京:科学出版社,2005
[51]鲁文华,旋转带蒸馏塔流场的CFD模拟:[硕士学位论文],天津:天津大学,2007
[2] Pease W F, Gilbert A H, Arno Cahn, Improved stirrer and bearing for spinning band distillation columns, Anal. Chem., 1960, 32(7):894~895
[3] Freeman S J, Nerheim A G, A macro spinning-band distillation column, Anal. Chem., 1959, 31(11):1929~1930
[4] Baner R H, Barkenbus C, Roswell C A, A large spinning-band fractionating column for use with small quantities of liquids, Ind. Eng. Chem., 1940, 12(8):468~471
[5] Jentoft R E, Doty W R, Gouw T H, Spinning band distillation column still heads, Anal. Chem., 1969, 41(1):223~224
[6] Freeman S J, Nerheim A G, A Macro Spinning-Band Distillation Column, Anal. Chem., 1959, 31(11):1929
[7] Nerheim A G, Analytical Distillation in Miniature Columns: Design and Testing of Teflon Spinning Band, Anal. Chem., 1957, 29(10): 1546~1548
[8] Nerheim A G, Dinerstein R A, Analytical Distillation in Miniature Columns: Performance under Total and Partial Reflux, Anal. Chem., 1956, 28(6): 1029~1033
[9]许松林,王燕飞,新型分离技术—旋转带蒸馏,化工机械,2006, 33(4):191~194
[10] Baner R H, Barkenbus C, Roswell C A, A large spinning-band fractionating column for use with small quantities of liquids, Ind. Eng. Chem., 1940,12(8):468~471
[11] Nester R G, Spinning-band fractionation column, US Patent, 2712520, 1955-7-5
[12] Foster N G, Green L E, Anal. Chem., 1952,24,1869
[13] Birch S F, Gripp V, Nathan W S, Soc. Chem. Ind., 1947, 66,33~40
[14] Nester R G, Separator, US Patent, 3372095, 1968-3-5
[15] Nerheim A G, Fractionator with plastic spinning band, US Patent, 3080303, 1963-3-5
[16] Nerheim A G, Head for spinning band fractionator, US Patent, 2764534, 1956-9-5
[17] Mayo, Dana W, Pike, et al., Spinning band fractionating column, US Patent, 4770746, 1988-9-13
[18] Roark S, Roger R, Spinning band, US Patent, 5603809, 1997-2-18
[19] Roark S, Roger R, US Patent 5472574, 1995
[20] Gerhard Kl?sel, Opladen, Rotor for Thin Layer Evaporator. US Patent, 3423782.1963
[21] Nairmen Mina-Camilde, David L C, Carlos M I, FT-IR spectroscopy in liquid xenon solution, ab initio calculations, normal coordinate analysis, and vibrationalassignments of meso-2, 4-dichloropentane and racemic-2, 4-dichloropentane, Spectrochimica Acta Part A, 1998, 54: 419~437
[22] Manzanares C E, Reynolds D, Lewis E K, et al., Matrix isolation FT-IR, FT-Raman spectroscopy, conformational ab initio calculations, and vibrational frequencies of meso andracemic-2, 4-pentanediol, Journal of Molcular Structure, 2004, 689:183~190
[23] Petrov V A, Frederic D, Bruce E S, Quadricyclane-trermal cycloaddition to polyfluorinated carbonyl compounds A simple synthesis of polyfluorinated 3-oxatricyclo[4.2.1.02,5]non-7-enes, Journal of Fluorine Chemistry, 2004, 125:1543~1552
[24] Feiring A E, Rozen S, Wonchoba E R, Synthesis of arylperfluoroalkyl ethers by direct fluorination, Journal of Fluorine Chemistry, 1998, 89:31~34
[25] Hoffsommer, R B, Jr., M.S.thesis, Pennsylvania State University, 1956
[26] Nerheim A G, Improved Head and Flask for Miniature Distillation, Anal.Chem., 1959, 31(12):2114
[27] Murray K E, Amer J, A Modified Spinning-Band Column for Low Pressure Fractionation. Oil Chemists’Soc., 1951, 28(1):235~239
[28] Ralph G, Nester E, Spinning Band Still for Vacuum Operation, Anal. Chem., 1956, 28(2):278~279
[29]傅德熏,马延文,计算流体力学,北京:高等教育出版社, 2002
[30]刘顺隆,计算流体力学,哈尔滨:哈尔滨工程大学出版社, 1998
[31]杨友麒,项曙光,化工过程模拟与优化,北京:化学工业出版社,2006
[32]王瑞金,张凯,王刚,Fluent技术基础与应用实例,北京:清华大学出版社,2007
[33] Fluent Inc., FLUENT User’s Guide. Fluent Inc., 2003
[34] Fluent Inc., FLUENT User Defined Function Manual. Fluent Inc., 2003
[35] Fluent Inc., Gambit Modeling Guide. Fluent Inc., 2003
[36]王福军,计算流体动力学分析—CFD软件原理与应用,北京:清华大学出版社,2004
[37] Lanzani A, Journal of the American Oil Chemists’Society, 1994, 71(6): 609~614
[38] Versteeg H K, Malalasekera W, An Introduction to Computational Fluid Dynamics: The Finite Volume Method. Wiley, New York, 1995
[39] Schlichting H, Boundary Layer Theory,8th ed.McGrawHill, New York,1979
[40]陶文铨,数值传热学,西安:西安交通大学出版社,2001
[41] Shih T H, Liou W W, Shabbir A, e tal., A new eddy viscosity model for high Reynolds number turbulent flows, Comput Fluids., 1995,24(3):227~238 k ?ε
[42]董丽萍,旋转带蒸馏塔的计算流体力学模拟:[硕士学位论文],天津:天津大学,2007
[43] Xien X, Zhihai Z, Songjiang T, Study on catalytic distillation processes: Prediction of pressure drop and holdup in catalyst bed, Trans. IChemE (A), 1997,75, 625～629
[44]周爱月,化工数学,北京:化学工业出版社,2002
[45] Ludovic R, Isabelle H, Studies of gas-liquid flow through reactors internals using VOF simulation, Chem. Eng. Sci., 2001, 56: 6385～6391
[46]韩占忠,王敬,兰小平,FLUENT—流体工程仿真计算实例与应用,北京:北京理工大学出版社, 2004
[47]杨忠华,规整填料在多种压力条件下混合特性的实验研究:[硕士学位论文],天津:天津大学,2001
[48]戚以政,汪叔雄,生化反应动力学与反应器,北京:化学工业出版社,2003
[49]余国琮,黄洁,张泽庭等,大型塔板的液体停留时间分布与数学模型,天津大学学报,1985, NO.4:P1
[50]罗康碧,罗明河,李泸萍,反应工程原理,北京:科学出版社,2005
[51]鲁文华,旋转带蒸馏塔流场的CFD模拟:[硕士学位论文],天津:天津大学,2007