错流旋转填料床气相压降特性

旋转填料床的气相压降是旋转填料床应用和设计的一项重要指标。在气液两相错流流动条件下，利用空气-水系统对错流旋转填充床的气相压降进行分段模型化和实验研究。按照错流旋转填料床气体流动的路径将气相压降分为进口压降、填料层压降、集气段旋转动能转化压降和出气段压降。推导出压降与操作工况的关联式，其计算值与实测值吻合较好。实验表明错流旋转填料床的气相总压降与气体流量、旋转床转速、液体流量有关。在高转速和小气量的条件下，气相压降随气量增大先下降后上升；其他情况随气量增大而上升。错流旋转填料床气相压降随转速上升而下降，在小气量情况下转速对气相压降有明显影响。气相压降随进液量的增大而增大，当旋转填料床在低转速时进液量对气相压降有明显影响。     

动-静填料旋转床内部气相流场CFD模拟研究

通过对动-静填料旋转床进行简化,建立了二维物理模型,采用计算流体力学软件Fluent中多孔介质模型对旋转填料床内部流场进行了模拟研究。通过对旋转填料床进口结构形式、填料层厚度、动填料转速及进气速度对气相压降和速度分布影响的模拟研究,得出切向进口旋转填料床内气体分布更均匀;保持填料外径不变,增大填料层厚度,气相压降随之降低;气相压降随动填料转速和进气速度的增加而增大,这与常规的整体填料旋转床保持一致。     

三角形螺旋填料旋转床气相压降特性

为深入了解三角形螺旋填料旋转床气相压降的影响因素及规律,以空气-水为实验物系进行了实验和模型研究。改变气、液流量及转速测定气相压降的实验结果表明,气体流量和转速的增大均使干、湿床气相压降增大;液体流量增大时湿床气相压降先减小,而后基本保持不变;该旋转填料床具有气相压降小、操作弹性大的优点。按照气相压降产生的机理,将其分为局部压降、离心压降、转子外内腔压降和填料主体压降4部分进行模型研究,其中用旋涡理论描述转子外内腔压降、用简化的模型描述填料主体压降是新提出的方法,且所建模型能较好地描述气相压降的规律。     

超重力旋转床气相压降模型研究进展

超重力旋转床是一种高效的气液接触设备,可极大地强化气液传质过程,在化工、材料、冶金、能源、环保等领域有着广泛的应用前景。气相压降是超重力旋转床设计、选型时需要考虑的一项重要指标。自从超重力旋转床问世以来,人们对其气相压降进行了较为广泛的研究。对近年来国内外超重力旋转床的气相压降模型研究进展进行了综述。分别从逆流式旋转填料床、错流式旋转填料床、折流式旋转床3方面具体介绍了各压降模型的研究方法并进行了对比,最后对超重力旋转床气相压降模型研究的方向与重点做了简要分析。     

错流旋转填料床气相压降特性研究

旋转床的气相压降是旋转床工程设计的一项重要指标。笔者利用空气,水系统对错流旋转填料床的气相压降进行实验研究。结果表明：在实验范围内,错流旋转床压降是逆流旋转床的十分之一;对错流旋转床压降影响较大的是转速和气量,与液流量几乎无关。     

并流旋转床压降与传质特性的研究

利用水-空气系统对并流旋转床的气相压降进行了研究,并与逆流旋转床气相压降进行了对比。研究结果表明：并流较逆流旋转床的气相压降低;并流旋转床的气相压降随气体流量的增大而增大,随液体流量的增大而减小,随转速的增大明显降低;而逆流旋转床的气相压降随转速的增大明显升高。利用水吸收SO2的实验对并流旋转床的传质特性进行了研究。研究结果表明：并流旋转床填料层内各点的体积传质系数随着气体流量、液体流量和转速的增大而增大;填料层半径由70mm增大至90mm时,并流旋转床的体积传质系数迅速增大,而后并流旋转床的体积传质系数随半径的增大而减小。对并流和逆流旋转床填料层内体积传质系数进行了对比。结果表明：填料层半径由70mm增大至130mm时,并流旋转床的体积传质系数较逆流时大;当半径大于130mm后,逆流旋转床的体积传质系数大于并流旋转床的体积传质系数,且随半径增大而增大。根据研究结果,提出了降低系统压降的设想,即并流与逆流旋转床串联操作。     

折流式超重力旋转床转子结构对气相压降的影响

折流式超重力旋转床是继旋转填料床之后出现的一种新型高效的气液传质设备.今采用空气-水系统对折流式旋转床进行了气相压降实验,考查了折流式转子结构对气相压降的影响,建立了折流式旋转床干床气相压降的理论模型.实验结果表明:折流式旋转床转子结构对气相压降影响较大,在动静折流圈结构不变的情况下,动静盘垂直间距存在某一最优值,通过实验得到了实验中所用的折流式旋转床的最佳转子高度为90 mm,实验也验证了旋转床设计时采用的等通流面积原则是符合气体运动规律的;干床压降理论模型的计算结果与实验值符合较好,为建立湿床压降模型奠定了基础.     

蒸馏过程中旋转填料床的传质和流体力学特性

建立了一套完整的精馏实验装置,以甲醇-水溶液为物系,在常压、全回流操作条件下,研究了旋转填料床的传质和流体力学性能. 结果表明,旋转填料床的理论塔板数随超重力因子和气相动能因子的增大出现峰值,理论塔板高度最小为0.0109 m;气相压降随气相动能因子、超重力因子的增大而增大. 在实验基础上应用最小二乘法建立了旋转填料床的传质、压降实验关联式.     

网板填料复合旋转床的流体力学与传质性能

开发了一种新型的气液接触设备——网板填料复合旋转床。常压下以空气-水物系和乙醇-水物系在网板填料复合旋转床中进行流体力学与传质性能实验,考察了气液流量和转子转速对网板填料复合旋转床压降和传质性能的影响。实验结果表明,气体流量和转子转速的增大均使干、湿床气相压降增大;液体流量的增加对湿床压降的影响不明显。回流量和转速的增加均使等板高度减少至一定值后几乎不变。网板填料复合旋转床具有通量大、效率高、压降小的特点。     

碟片填料旋转床气阻与气液传质实验研究

实验测量了超重力旋转床气液传质反应器在采用同心环波纹碟片填料的时的气相压降和气液传质特性,对不同转速,气流量,液流量条件下的气相阻力与气液传质性能进行了实验研究和分析,结果表明干床的气相压降是相同状态下采用金属丝网填料的气相压降的６０％左右。     

规整丝网填料旋转填充床的气相压降特性及脱硫性能

采用空气-水体系,对装有4种不同规格规整丝网填料的旋转填充床的压降特性进行了实验研究,考察了转速、气体流量、液体流量等操作参数及填料特性对气相压降的影响规律,并与传统不锈钢波纹丝网填料旋转填充床压降进行了比较. 结果表明,装有规整丝网填料的旋转填充床压降可降低35%~70%. 进一步采用压降较低的规整丝网填料以(NH4)2SO3为吸收剂进行氨法脱硫性能研究,结果表明,随转子转速和(NH4)2SO3浓度增大,SO2脱除率升高;随进气口SO2浓度升高及气液比增大,SO2脱除率降低;SO2脱除率最高可达97%,可满足国家排放标准.     

Experimental researches on mass and heat transfer in new typical cross-flow rotating packed bed

New typical cross-flow Rotating Packed Bed(RPB)called multi-pulverizing RPB was manufactured.There is enough void in multi-pulverizing RPB,where liquid easily flows and is repeatedly pulverized by light packing,which decreases the material consumed,lightens the weight,and compacts the structure.Mass and heat transfer property in the new type PRB were studied by two experimental models.In the mass transfer model,the axial fan pumping gas press is only 100 Pa,mass transfer coefficient and volumetric mass transfer coefficient are similar to countercurrent RPB,which are an order quantity lager than that in the conventional packed tower.In the heat transfer experiment,the axial fan pumping gas press is only 120 Pa;volumetric heatwhich especially suits the treatment of large gas flow and lower gas pressure drop.     

Computational fluid dynamic simulation of fluid flow in a rotating packed bed

Rotating packed bed (RPB) has been widely used in absorption, desorption, distillation, oxidation, crystallization, precipitation, polymerization, and production of nanoparticles. RPB utilizes centrifugal acceleration to intensify the mixing and mass-transfer processes. Under high-gravity, molecule diffusions are much faster than under normal gravity. With the centrifugal force generated by rotation, RPBs have considerable high mass-transfer and micromixing performance. However, because of the complexity of fluid flow inside the RPB, the flow experiments do not easily lead to the deeper understanding on the fluid dynamics in an RPB. In this paper, computational fluid dynamics model and two-, three-dimensional physical models have been developed to describe the RPB. Numerical simulation of the fluid flow and pressure drop in dry bed in an RPB using commercial software, Fluent, as a computational platform has been carried out. Different fluid flow rates, rotator speeds and gas flow rates have been systematically investigated. The preliminary simulation results show that the models used to describe the RPB can give rise to better understanding of the flow in an RPB.     

Analysis of flow in rotating packed beds via CFD simulations—Dry pressure drop and gas flow maldistribution

Three-dimensional unsteady-state turbulent rotating single-phase flows were simulated in rotating packed beds (RPB) and were validated using overall dry pressure drop measurements for three RPB designs [Liu, H.-S., Lin, C.-C., Wu, S.-C., Hsu, H.-W., 1996. Characteristics of a rotating packed bed. Industrial and Engineering Chemistry Research 35, 3590-3596; Sandilya, P., Rao, D.P., Sharma, A., Biswas, G., 2001b. Gas-phase mass transfer in a centrifugal contactor. Industrial and Engineering Chemistry Research 40, 384-392; Zheng, C., Guo, K., Feng, Y.D., Yung, C., 2000. Pressure drop of centripetal gas flow through rotating bed. Industrial and Engineering Chemistry Research 39, 829-834]. Analysis of the radial and tangential velocities highlighted the impact of gas feed entrance effects on the peripheral gas maldistribution in the rotating packing module. Recommendations were formulated for an optimum design with the aim to reduce gas flow maldistribution in RPBs. Breakdown of the overall pressure drop in its modular components for the housing, the rotating packing module, the free inner rotational zone, and the gas disengagement showed that the dissipation in the rotating packing could be a minor contributor to the overall pressure drop which may be undesirable in terms of RPB mass transfer and reaction efficiencies. Analysis of the simulated pressure drops allowed development of CFD-based Ergun-type semi-empirical relationships in which the gas-slip and radial acceleration effects, the laminar and inertial drag effects, and the centrifugal effect were aggregated additively to recompose the pressure drops in the rotating packing module.     

翅片导流板填料应用于旋转填料床的特性

For an alcohol/water system and with fin baffle packing, continuous distillation experiments were carried out in a rotating packed bed (RPB) system at atmospheric pressure. The effects of the average high gravity factor (β), liquid reflux ratio (R) and feedstock flux (F) on the momentum transfer and mass transfer were investigated. The gas phase pressure drop of RPB increased with the average high gravity factor, liquid reflux ratio and feedstock flux, which was 13.55-64.37 Pa at β of 2.01-51.49, R of 1.0-2.5, and F of 8-24 L&;#8226;h－1 for a theoretical tray in the RPB with fin baffle packing. The investigation on the mass transfer in the RPB with different packings showed that the number of transfer units of RPB with a packing also increased with the average high gravity factor, reflux ratio and feedstock flux. It is found that the fin baffle packing (packing III) presents the best mass transfer performance and lowest pressure drop for the height equivalent to a theoretical plate (HETP), which is 6.59-9.84 mm.     

基于离散相模型的旋转填充床内的流场分析

利用CFD软件Fluent初步模拟了旋转填充床(Rotating Packed Bed,RPB)内的流体流动.计算中气相采用RNGk-ε湍流模型,液相采用拉格朗日离散相模型(DPM).通过一定简化后建立了旋转填充床二维模型,考察了液体颗粒在填充床内的速度分布,以及转速对液体颗粒速度的影响.结果显示液滴速度随转速的增加而增加,转速对液滴径向速度的影响不大.此外还针对转速、气体进口速度对干床压降的影响做了一定的研究,发现压降随转速的增加而增加,但其影响没有气体进口速度对压降的影响明显.填料的内缘处存在剧烈的端效应,模拟结果表明,端效应区的湍动强度明显大于其他区域.     

分层填料对旋转填料床气相流场影响的数值模拟

通过设计简化的分层填料旋转床(SP-RPB)模型，采用计算流体力学方法(CFD)对比同尺寸旋转填料床(RPB)的稳态气相流场。分析转速和进料速度对气相压力、相对速度及湍动能分布的影响，同时还考察了单位丝网圈上的压降情况。结果表明，在气体进入各级填料位置的相对速度出现峰值，湍动能分布与之相同，各峰的出现位置仅由填料位置决定，两者共同表明SP-RPB具有多个端效应区域。转速增加对相对速度峰值大小有更明显的提升，较大的进料速度使填料内气体的速度波动更大，也使湍动能的峰值有所增加。由于SP-RPB内填料厚度较RPB变薄，从整个设备范围上看，SP-RPB表现出更低的压降。进气速度提高和转速降低使SP-RPB两层填料间的高压范围变窄，但SP-RPB的单位丝网圈数压降更大。