A novel unified correlation model using ensemble support vector regression for prediction of flooding velocity in randomly packed towers

Traditional empirical correlations and models have found insufficient to predict the flooding velocity accurately mainly because there are many kinds of random packings which exhibit different characteristics. In this work, a novel data-driven modeling method, i.e. ensemble least squares support vector regression (ELSSVR), is proposed to construct a unified correlation for prediction of the flooding velocity for packed towers with random packings. The flooding data are first clustered into several classes by the fuzzy c-means clustering algorithm. Then, several single LSSVR models can be trained using each sub-class of samples to capture the special characteristics. Moreover, a weighted least squares approach is adopted to integrate these single LSSVR models. Consequently, the ELSSVR model can extract the feature information of flooding data effectively and improve the prediction performance. The proposed ELSSVR method is applied to construct a unified correlation for prediction of the flooding velocity in randomly packed towers. The obtained results for several kinds of random packings demonstrate that the ELSSVR-based correlation can obtain better prediction performance, compared with the traditional semi-empirical correlations and artificial neural networks-based models. Finally, a database containing the modeling information of flooding velocity in randomly packed towers of China is provided for academic research.     

散装填料层泛点和压降的新关联

在理论分析的基础上 ,导出了散装填料层泛点气体速度和压降的新关联式 ,由实验数据计算了常用填料新关联式的液泛填料因子和压降常数。新泛点关联式对 8种填料泛点气速的计算值与实验数据的总平均计算误差为 3.5 2 % ;新压降关联式对各种填料的压降平均计算误差一般在 10 %以下。关联值与实验数据吻合很好 ,计算准确性优于文献公式 ,且比文献公式计算简便。     

A Shortcut Method for the Estimation of Structured Packings HEPT in Distillation

A shortcut method to calculate HETP for metal structured packings is proposed. The method is a simplification and extension of Lockett's equation for sheet packings, based on the Bravo, Rocha and Fair model. It is applicable at vacuum or pressure distillation of organic or aqueous mixtures in columns of sheet and gauze packings. The necessary variables are specific surface of packing, density of vapor and liquid and flow (when gauze packings are being considered). No estimation of hydrodynamic conditions is necessary.     

Correlation of HETP and experimental variables in preparative liquid chromatography

HETP (Height Equivalent to a Theoretical Plate) is widely designated as the column efficiency in Chromatographic separations. The effects of experimental variables such as concentration, injection volume, flow rate and composition of the mobile phase, column diameter, and column length on HETP were investigated by preparative liquid chromatography. Water and methanol as an organic modifier were used as the mobile phase. A sample of thymidine was injected into C₁₈ columns with different dimensions. From fifty experimental runs, it was shown that the larger amounts of sample and higher flow rates increased HETP and an optimum HETP existed at a column diameter of 7.8 mm for preparative packings used in this experiment. The experimental values of HETP were correlated into a quadratic equation with the interaction terms based on the logarithmic experimental values of the experimental variables ; its regression coefficient was 0.952. The experimental variables were simulated from the correlation equation, and their effects on HETP were discussed.     

Determination of flooding gas velocity and liquid hold-up at flooding in packed columns for gas/liquid systems

A new model of suspended bed of droplets for describing the vaour or gas the vapour or gas velocity at the flooding point in packed of columns for rectification and absorption under vacuum and normal pressure is presented metallic, ceramic and plastic packings with diameters of 8–90 mm as well on sheet metal and gauze packings, in a wide range of liquid and vapour loads. Approximately 650 literature measurements and own data were evaluated. The mean relative error in determining the gas velocity at flooding point is less than ±5%. On the basis of the double layer model, a new equation was derived for the hold-up at flooding point, which is needed for the calculation of the flooding gas velocity. An example of calculations for sample applications is also included.     

Extruded monoliths for gas separation processes: Height equivalent to a theoretical plate and pressure drop correlations

Extruded monoliths are generally adopted in the chemical industry for the advantage of reduced pressure drops at high throughput, but a systematic procedure to evaluate their performance is not readily available. Key performance indicators for a monolith are the height equivalent to a theoretical plate (HETP) and the pressure drop of its channels. This contribution presents for the first time a systematic approach to the analysis of several extruded monoliths of industrial relevance. A procedure to derive the HETP correlation for an arbitrary extruded monolith is presented, and pressure drop correlations from literature are reviewed. The HETP correlations have been validated against three dimensional (3D) numerical simulations. A reduced-order model is derived from the HETP and is shown to capture the overall dynamics of the 3D simulations with high accuracy without adjustable parameters. Finally, a comparison between the extruded monoliths and packed beds is reported and includes pressure drops.     

旋转填料床连续精馏实验研究

The performance of a rotating packed bed （RPter solutioB） with three kinds of packings was investigated using alcohol/wan under continuous distillation conditions at atmospheric pressure. The effects of average high gravity factor （β）, reflux ratio （R）, and feedstock flux （F） on mass-transfer in distillation were examined separately. Experimental results indicated that the total number of theoretical units （NTU） of RPB increased with β, R, and F.Of the three kinds of packings, the wave thread packing of stainless steel （Packing-Ⅲ）-had the best mass transfer efficiency with the height equivalent of a theoretical plate （HETP） of approximately 7.35 mm- 23.58 ram, whereas the corrugated disk pacing of stainless steel,（Packing Ⅰ） had the worst one with the HETP of about 13.4 mm-48.07 mm.Correlations were cleveloped to describe the mass transfer efficiency for packings Comparing.experimental data with the data calculated by correlation, the average deviate obtained for each packing was 0.72%, 1.98%, and 2.7%, respectively, implying that the accuracy of correlations developed was reasonable.     

三种开孔环形填料传质性能的研究

本文介绍了在φ600mm的实验装置内,对Dg50mm聚丙烯鲍尔环（井）、聚丙烯鲍尔环（米）、聚丙烯阶梯环（Ⅰ）填料,用空气脱吸CO_2水溶液,测得的传质性能数据,并用此数据对液膜传质系数的不同关联方法进行了核算、对比。认为:恩田等所提出的计算液膜传质系数的关联式,在计算新型开孔环形填料时偏差较大,主要是由于他们所提出的形状系数a_td_p,未能反映这些新型填料的形状特征对其传质性能的影响。本文用形状修正系数ψ来代替a_td_p,这样恩田等的计算液膜传质系数的关联式,其应用范围被扩展到新型开孔环类型填料的范围。 采用新的形状修正系数ψ后,液膜传质系数的计算式改写为 k_L(ρ_L/μ_(Lg))~1/3=0.0095(L_G/a_ωμ_L)~2/3(μ_L/ρ_LD_L）~(-1/2)ψ~0.4对各种不同类型填料其形状修正系数值为 本式可适用于Dg50mm以下的上述各类填料的计算。     

Process intensification of distillation using a microwick technology to demonstrate separation of propane and propylene

Process intensification (PI) of distillation using a microchannel distillation (MCD) device successfully reduced the height of a theoretical plate (HETP) in separating propane and propylene to 1.2 cm, representing 10 theoretical stages. Mass transfer is enhanced using thin wicking structures that are 0.17 mm thick in counterflow with vapor. Liquid is segregated in the wicks by applying a siphon relative to the vapor phase, which also enables the device to operate horizontally. A scalable device containing 11 wicks was operated cryogenically in total reflux. The HETP varied between 1.2 and 4.5 cm, representing a dramatic reduction over commercial structured packings and comparable to other PI approaches. Significant improvements are expected with further development. Potential application for intensified distillation processes include distributed manufacturing and difficult separations involving close boiling compounds and meeting high purity specifications. The ultimate application is isotopic enrichment, where the number of stages required is typically multiple thousands. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3690–3699, 2018     

高压下高比表面丝网规整填料传质性能的测试

引言 20世纪70年代以来,填料塔已广泛地应用于精馏、吸收、解吸和萃取等工业分离过程.     

Comparison of the effective area of some highly effective packings

The effective area a_e of three types of highly effective packings such as Raschig Super-Ring, IMTP and Ralu-Flow made from stainless steel and from plastic with nominal size from 20 to 70 mm, are investigated using the Danckwerts method with absorption of CO₂ in NaOH by pseudo-first-order fast chemical reaction. The liquid superficial velocity L varied between 5 and 200 m³/(m²h). The comparison of the obtained data shows the following:

Among all investigated packings at comparable values of the specific area and the liquid superficial velocities, the metal Raschig Super-Rings (RSR) have the highest effective area. They have also the lowest pressure drop versus effective area, at the same gas velocity.

At comparable values of the specific area and the liquid superficial velocities the effective areas of the plastic Ralu-Flow and plastic RSR are practically the same, but the first of them have lower pressure drop versus effective area, at the same gas velocity.

As it is to be expected, all metal packings have greater effective area than all plastic ones with the same specific area. That means among all investigated 14 packings, the metal RSR have the greatest effective area.     

浮选柱中液相轴向返混的研究

An experimental study on the axial dispersion of liquid was carried out in a 0.382-m-ID flotation column packed with different structured packings or free of packings. The correlations of axial Peclet numbers with the liquid and gas superficial Reynolds numbers were developed for various packings. Among the packings tested, it is found that in the column packed with 250Y or 350Y packings the axial dispersion is the lowest. The addition of frother can decrease the axial dispersion. By the simulation analysis of the one-dimension dispersion model of packed flotation column, it is found that small axial dispersion, high collection rate constant and low axial liquid velocity can increase the collection zone recovery.     

不锈钢填料表面处理前后的性能

本文采用液相化学对不锈钢填料进行表面处理,并对处理前、后的填料抗腐蚀性能、传质性质进行了测试。结果表明：填料经综合处理后,其抗腐蚀性能、传质性能均有较大的提高。对于分离普通有机物以及高表面张力物系,其等板高主ＨＥＴＰ分别下降约２０％和３０％。     

Hydrodynamic‐Analogy‐Based Modeling Approach for Distillative Separation of Organic Systems with Elevated Viscosity

A modeling approach based on hydrodynamic analogies is applied to predict the influence of elevated viscosity on the separation efficiency of distillation processes in structured packed columns. An advantage of this approach compared to traditional models based on the film theory is that separation columns can be described without empirical mass transfer coefficient correlations. The separation efficiency was evaluated for two systems with distinct viscosities at different gas and liquid loads and various operating pressures. Simulated concentration profiles and height of a theoretical plate (HETP) values were compared with the data obtained from own experiments. The developed model is capable of correctly predicting the differences in the HETP values of the two evaluated systems.     

A physical model for the prediction of liquid hold-up in two-phase countercurrent columns

This contribution presents the determination of liquid hold-up in gas/liquid two-phase countercurrent columns filled with random or structured packings. The equations resulting from the established physical relationships are varified against the values for liquid hold-up determined experimentally on 56 different column packings and 16 gas/liquid systems. The experimental and calculated results agree well, with only slight deviations. This also applies to the range between the loading and flooding points for two-phase countercurrent flow.     

Influence of non-wetted fluored polymer packings in distillation columns—I Hydrodynamics

Packing wettability has a noticeable influence on the hydrodynamics of columns. Non wetted fluored polymer packings are studied in order to determine the pressure drops and flooding conditions compared with wetted glass packing. Experimental results and correlations established will enable a more precise design of industrial columns.     

On packed column hydraulics

Packed columns are normally operated countercurrently in the vapor‐continuous regime. At specific combinations of liquid and vapor loads these columns flood. This article proposes that flooding is a form of second order (or “continuous”) phase transition from vapor‐continuous to liquid‐continuous operation. Thus, flooding is unambiguously defined to be the set of those vapor/liquid flow combinations, {C_L, C_Sf}, that cause a liquid cluster to form that spans the diameter of column. These statements imply that a law of corresponding hydraulic states exists for packed columns. By this, we mean that sets of {C_L, C_S, (Δp/Z)_2?} data taken with a specific packing and a specific vapor/liquid system exhibit a significant collapse when they are renormalized to {f_L, (Δp/ρ_LgZ)_2?} (where f_L is the fractional approach to flood at constant liquid load). The renormalized dataset then applies to any vapor/liquid system using that particular packing. Renormalization thus forms the basis of a method for predicting column pressure drops and flood points for any column using the particular packing being studied. We demonstrate how the renormalization procedure is carried out by analyzing readily available air/water data for a number of different packings. We then show that a version of the Wallis equation can be used to correlate packed column flooding data successfully. Further, we demonstrate that the variation of the Wallis parameters with the equivalent diameters of packings in a geometrically similar family leads to a complete characterization of the effects of the physical properties of liquid on the flooding locus for these packings through the Bond number. This last result is a direct result of generalized homogeneity considerations. Finally, we show that there exists an even more general formulation of the law of corresponding hydraulic states that applies to all packings regardless of type, size, or material of construction. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1671–1682, 2012     

固定床吸附柱放大效应考察─—理论板当量高度分析

从色谱塔板理论公式出发，推导出实测理论板公式及理论极当量高度和吸附热力学、吸附动力学参数之间的关系，并对模型的选择、优化操作线速的选取作了讨论。实验测定了ｄ＿ｐ／ｄ＿ｔ＝４．０／２０．０时，吸附柱内的轴向扩散系数及流体传质系数，并加以关联。对不同压力、流量下的理论板当量高度也进行了检验。     

Performance characteristics of a packing with boundary layer turbulizers. IV. Gas-film controlled masstransfer

The gas-film controlled mass-transfer rate in a honeycomb packing, with stamped groove turbulizers (Turbo-Pack) which affect the region of the boundary layer, has been studied. An equation for determining the mass-transfer coefficient as a function of gas velocity and the geometrical dimensions of the packing has been derived. It is found that the effect of the height of packing blocks is far less than that forecast by Zhavoronkov's equation which was derived for packings with a much higher wall thickness. Comparison of experimental data relevant to the novel design with reference packings cited in the literature shows that as far as its low values of pressure drop per mass transfer unit are concerned the Turbo-Pack packing is superior to all other known packings.     

固定床吸附柱放大效应考察─—理论板当量高度分析

从色谱塔板理论公式出发，推导出实测理论板公式及理论极当量高度和吸附热力学、吸附动力学参数之间的关系，并对模型的选择、优化操作线速的选取作了讨论。实验测定了ｄ＿ｐ／ｄ＿ｔ＝４．０／２０．０时，吸附柱内的轴向扩散系数及流体传质系数，并加以关联。对不同压力、流量下的理论板当量高度也进行了检验。