Tray Efficiency Research Articles

Experimental Quantification of Point Efficiency of Sieve Trays at Elevated Viscosity under Non-Total Reflux Conditions

Experimental Quantification of Point Efficiency of Sieve Trays at Elevated Viscosity under Non-Total Reflux Conditions

Simulation of extractive distillation of C6 components from Fischer‐Tropsch Synthesis oil

AbstractExtractive distillation is used for separating oxygenates from other components in the C6 cut oil from Fischer‐Tropsch Synthesis followed by separating 1‐hexene from N‐hexane using the same solvent as the extractant. Furfural (FUR) is identified as an excellent solvent for extractive distillation of the C6 cut from FTS oil for separating oxygenates from other components as well as for separating 1‐hexene from N‐hexane via searching from more than 100 solvents by simulation using Aspen Plus. The behavior of the newly found solvent FUR is compared with that of the reported best solvent N‐methyl‐2‐pyrrolidone (NMP) and the results show that FUR scheme has the advantages of lower market price, lower dosage needed, less reboiler duty required and higher overall tray efficiency for fulfilling the same separation task.

Parametric studies on fractionation column design for the separation of plastic waste pyrolysis oil into valuable fuels

The increased global consumption of plastics prompts concerns about disposal methods and management. The castoff plastics (of any kind) majorly end up in landfills or are incinerated or disposed of into the oceans. However, these methods are not sustainable in the long run and harm the ecosystem. A better approach to tackle these wastes is the need of the hour, as the climate change crisis negatively impacts the environment. In this work, a process is ideated and implemented in Aspen Plus® V12.0, which involves the simulation of a fractionation column with a feed that is obtained by the pyrolysis of the waste plastic to yield an array of distillate cuts consisting of different hydrocarbon mixtures. Analysis of the fractionation column performance with sieve and bubble-cap tray configurations and the effect of tray efficiency, temperature, pressure, and other factors on the composition of the hydrocarbon mixture in different product streams were studied and outlined with the equilibrium tray and rate-based calculation mode. A techno-economic analysis of the process was also performed, and the relevant comparative analyses were illustrated and outlined.

Effects of non-uniform weeping distributions on tray and point efficiencies

Weeping is known to significantly reduce tray and point efficiencies in distillation tray columns. When designing distillation columns, conservative rules of thumb are applied to account for the effect of weeping on separation efficiency, while assuming uniform weeping distribution. However, experimental studies and CFD simulations generally reveal non-uniform weeping. The current study addresses this discrepancy, providing an experimental approach for simultaneously determining tray and point efficiencies at weeping conditions. The proposed approach is able to account for a non-uniform weeping distribution. This work evaluates the effect of several non-homogeneous weeping distribution patterns on tray and point efficiencies. In particular, state-of-the-art non-uniform weeping distributions, which have low spatial resolution, have been compared with arbitrarily assumed high resolution weeping distributions. A comparison with uniform weeping distribution is also provided. The results illustrate that assuming uniform weeping distribution leads to significant under- or overestimation of the tray and point efficiencies, depending on the real weeping distribution. In addition, high resolution weeping data can massively improve the quantification of separation efficiencies, allowing to confidently operate distillation columns at weeping conditions.

Hydrodynamic and mass transfer correlations for SiC ceramic foam monolithic trays used in distillation column

AbstractBACKGROUNDCellular foam materials are excellent engineering materials for many applications in chemical engineering, especially process intensification of chemical conversions and separation. Recently, a silicon carbide (SiC) ceramic foam monolithic tray was developed as an excellent mass transfer tool to improve distillation and it showed an improved operational flexibility. Previous studies have revealed the effects of open cell diameter and tray thickness on the hydraulic performance and mass transfer efficiency of SiC foam monolithic trays, but relevant correlations are still missing, limiting their practical uses.RESULTSIn this study, based on the published experimental data, empirical correlations were developed to predict the hydrodynamic performance and mass transfer efficiency of SiC ceramic foam monolithic trays. The new correlations include the influence of the tray structure parameters, such as open cell (or pore) diameter and tray thickness, and of the operation conditions (such as the liquid and vapor volumetric flow rates), and the data obtained agree well with the experimental results.CONCLUSIONThe availability of such empirical correlations can be beneficial for the chemical engineering design of practical distillation processes based on SiC foam monolithic trays. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

A MODEL FOR PREDICTING THE NUMBER OF MASS-TRANSFER UNITS AND THE EFFICIENCY OF SIEVE TRAYS IN RECTIFICATION

The design of rectification columns is based on the method of thetheoretical tray and the actual setupof real trays is carried out with the help of various kinetic characteristics, such as tray efficiency. The relation between local and integral efficiency is a complex function of geometric, physicochemical and hydrodynamic factors. A theoretical method for calculating the tray efficiency has not yet been proposed, because of the complex hydrodynamic setting and the influence of a number of factors. Empirical correlations for calculating the local or integral efficiency of the traycan be found in the literature. The aim of the present work is to make a comparison between the calculated local efficiency data by means of a model known from the literature and the experimentally obtained data from the rectification of a model Tetrachloromethane-Toluene binary mixture in a laboratory single-sieve tray column. Among the tasks of the currentwork is also to determine the parameters of the applied model. The proposed method is semi-empirical and allows for the calculation of the number of mass-transfer units and, therefore,of the local efficiency.

Mechanism-based deep learning for tray efficiency soft-sensing in distillation process

Mechanism-based deep learning for tray efficiency soft-sensing in distillation process

Energy saving in distillation by combining vortex contact device and thermal effects

• Energy efficiency assessment of the thermal distillation in the column apparatuses is presented. • Heat extra removed from the upper tray of the column leads to a decrease in heat flows by 9–12%. • Vortex contact devices provide an increase in the mole fraction of the light-volatile component in the liquid by 5.61%. Thermal effects are proposed to improve the efficiency of heat and mass transfer phenomena in distillation columns. The new design of the vortex contact device is developed. The paper investigates a combined use of the vortex devices that act as the contact stages of the distillation column and heat removal from the upper contact stage. Theoretical results on the distribution of vapor and liquid flows on each tray of the vortex device are obtained. The mass flow rate of the liquid phase as a result of the partial condensation of vapors is determined based on the amount of heat removed and the location of the tray with additional heat removal. A reduction in the mass flow rate of reflux during thermal distillation is experimentally established. The dependence of the average Murphree tray efficiency of the vortex contact stage is obtained depending on the reflux ratio at thermal distillation, which is confirmed experimentally. Experimental study shows an increase in the average efficiency of the stage by 10.6% compared to the adiabatic column without heat removal. A distillate mass fraction of 0.884 in the liquid phase is achieved at the outlet of the column when using 10 vortex contact stages and the working reflux ratio of 1.83. The comparative analysis of the use of the developed vortex contact devices in the thermal distillation process is performed in terms of the separation quality of the ethanol–water mixture, energy costs for the supply, and removal of heat.

Comparative techno-economic evaluation of potential processing schemes for petroleum crude oil distillation

The two most commonly used schemes for crude oil distillation in operating refineries have been compared with two new schemes using two different crude oils for the energy consumption and energy cost parameters. Seven cases for each crude were conceptualized to carry out a realistic techno-economic evaluation of these schemes. Study results reveal the scope to reduce the ADC bottom stripping steam in 32.7–75% for the proposed scheme–I and 100% for scheme II. The furnace duty is reduced ~ 4.3–4.7% for the scheme–I and ∼ 4.6–6.15% for the scheme–II. Overall, the energy cost for crude oil distillation can be reduced in the range of 7.3–9.4% with scheme-I and 10.7–16.3% with scheme-II by implementing proposed schemes for revamping the existing and designing the new CDUs. The lower vapour rate in the rectification section and higher vapour rate in the stripping section of ADC in the proposed schemes compared to the conventional schemes suggests an opportunity to either increase the throughput without revamping the ADC or implement the proposed schemes to revamp existing AVUs without ADC modification and assistance in addressing the challenges associated with poor vapour liquid contact, lower tray efficiency, and fouling on tray decks. The structural topology of new schemes is similar to existing schemes, which ensure their easy and practically possible implementation for revamping the existing and designing the grass-root units CDUs to reduce energy costs and emissions significantly.

Nye tray vs sieve tray: A comparison based on computational fluid dynamics and tray efficiency

AbstractNye and sieve trays were hydrodynamically simulated and compared. The simulations were performed in a Eulerian‐Eulerian framework under unsteady (transient) conditions at industrial scale. Conducted on an air‐water system, the simulations included three dimensions and two phases. The velocity distribution across the tray, the height of clear liquid, the froth height, and the pressure drop were investigated and compared with experimental data. Péclet number was calculated using hydrodynamic and geometric parameters. The tray efficiencies were also predicted to further compare the two trays. The results showed that the liquid flow was steadier on the Nye tray rather than the sieve tray, possibly because of the special structure of the liquid and gas inlets for the Nye tray.

Uncertainty quantification and global sensitivity analysis of continuous distillation considering the interaction of parameter uncertainty with feed variability

In this work, uncertainty and sensitivity analyses were applied to study the joint effects of model parameter uncertainty and feed variability on the response of a computational code for methanol–water continuous distillation. First, model parameter uncertainty (liquid–vapour equilibrium (VLE), enthalpy and tray efficiency) was characterised using existing experimental data. Afterwards, three tower configurations working at two operational modes (fixed product composition and fixed operation conditions) were studied at three feed variability levels. Morris analysis revealed the high importance of the VLE and efficiency-related factors. Sobol sensitivity analysis determined with more precision the sensitivity of the response to the parameters and detected non-linear effects and interactions. The Monte Carlo propagation method allowed obtaining the uncertainty margins as a function of feed variability. The results showed high impact of the model parameter uncertainty and encourage the use of the methods shown to obtain robust designs and quantify simulation accuracy.

Hydrodynamics and mass transfer performance analysis of flow-guided trapezoid spray packing tray

Distillation is the most common separation technology utilized in the petroleum and chemistry industries. Due to the wide usage of the distillation column, even a small improvement in performance may result in significant energy cost savings. Aiming to improve the hydrodynamics and mass transfer performance, the flow-guided trapezoid spray-packing tray (FTS-PT) was designed by combining flow-guided holes and trapezoidal caps with structured packing. And the experimental measurements of the FTS-PT, including pressure drop, clear liquid height, weeping, entrainment, and tray efficiency, were conducted in a 500 mm diameter plexiglass column with the air-water-oxygen system. Moreover, the performance of the FTS-PT was compared with that of new vertical sieve tray (New VST) and F1 valve tray. The results show that FTS-PT has a significant advantage in pressure drop, entrainment, and capacity. Furthermore, the calculation model of the pressure drop was derived and used for the FTS-PT with a relative deviation of less than 5%.

Direct Tray and Point Efficiency Measurements Including Weeping Effects through a Convenient Add-On for Air–Water Simulators

A direct approach for determining the tray and point efficiencies of an industrial-scale distillation tray is proposed. The stripping of isobutyl acetate from an aqueous solution with air was used,...

Experimental Fluid Dynamics Study of a New Fractal Dual-Flow Tray

Countercurrent flow in conventional dual-flow trays results in segregation in liquid and vapor flow, reducing tray efficiency. Therefore, a new dual-flow tray with fractal geometry was experimental...

Point efficiency of sieve trays at elevated liquid viscosities

Liquid viscosity plays a major role in determining the mass transfer efficiency in distillation through its contribution to the liquid-phase mass transfer coefficient, interfacial area of mass transfer, and vapor and liquid phase residence times. Most of the distillation efficiency correlations in the literature were developed or validated based on efficiency data at liquid viscosities less than 1.5mPas. However, distillation at liquid viscosities greater than 1.5mPas is encountered in practice in the chemical process industry. Therefore, distillation efficiency data at liquid viscosities greater than 1.5mPas are required to accurately quantify the effect of liquid viscosity on distillation efficiency and to develop improved efficiency correlations. Point efficiency defines the most fundamental mass transfer efficiency for distillation trays upon which tray and column efficiencies are calculated. In this paper, the effect of liquid viscosity on point efficiency of sieve trays is reported with new data for four different test systems at liquid viscosities ranging from 0.2 to 4.2mPas. These new data are critical for evaluating the validity of the existing tray and point efficiency correlations and for extending the existing correlations or developing new correlations for distillation column design at elevated liquid viscosities.

Evaluation of the validity of tray and point efficiency correlations at elevated liquid viscosities and proposal of an improved point efficiency correlation

The accuracy of the distillation efficiency correlations plays a critical role in cost-effectively designing distillation columns. Liquid viscosity is considered to be a major factor that influences distillation efficiency through its contribution to the liquid-phase mass transfer coefficient, interfacial area of mass transfer, and vapor and liquid phase residence times. Nearly all of the distillation efficiency correlations in the literature were developed or validated on the basis of efficiency data at liquid viscosities less than 1.5mPas. However, distillation at liquid viscosities greater than 1.5mPas is encountered in several cases in the chemical process industry. In this paper, the evaluation of three different tray and point efficiency correlations using Oldershaw column data at liquid viscosities from 0.2 to 4.2mPas is presented. In addition, we propose an improved point efficiency correlation, based on the Duss and Taylor correlation, with a modified liquid viscosity exponent for the liquid-phase mass transfer coefficient. The proposed correlation was validated with commercial sieve tray efficiency data and Oldershaw column data. This proposed correlation will aid in the cost-effective design of distillation columns, especially at elevated liquid viscosities.

Design and proof of concept of a continuous pressurized multi-stage fluidized bed setup for deep sour gas removal using adsorption

Pressure swing adsorption (PSA) processes are frequently used in the (petro)chemical industry, but they suffer from ineffective use of the sorbent and slow heat transfer. A pressurized multi-stage fluidized bed (MSFB) for continuous PSA is proposed in this work to overcome these drawbacks. A one stage fluidized bed adsorber was used to determine minimum fluidization velocities of the used amine sorbent at various pressures up to 10 bara. The design of a pilot scale experimental setup is described, together with supporting experiments to show the proof of concept. Removal from 37,000 mol ppm CO2 to <10 mol ppm CO2 in a few seconds was demonstrated in the pressurized MSFB adsorber. The tray efficiencies were high: often larger than 0.85. Using a numerical particle model, it was concluded that the CO2 adsorption rate is controlled via intraparticle mass transfer.

Efficiency Estimation of Tray Columns Based on Flow Profiles and Vapor–Liquid Equilibrium Characteristics of Binary Mixtures

A new systematic approach for estimating the section and column efficiencies based on flow profiles and vapor-liquid equilibrium (VLE) characteristics of binary mixtures exclusively for each tray is proposed. A novel iterative technique for approximating the slope of the VLE curve and the tray efficiency is also developed. For demonstrating the predictive capabilities of the new approach, two case studies are formulated in this work - one with a theoretical column processing selected binary mixtures at total reflux, and the other involving an industrial column whose performance data is acquired from the literature. An in-depth analysis of theoretical column study reveals the superiority of the new approach over the most applied method. In the case study of industrial column, the new approach predicts the section efficiency accurately, unlike the efficiency underestimation from the most applied method. Such an approach would allow a priori calculation of the section and column efficiencies in the tray and ...

CFD Modeling to Predict Mass Transfer in Multicomponent Mixtures

Abstract A novel three-dimensional computational fluid dynamics mass transfer (CMT) model in Eulerian–Eulerian frame work is deploys for investigating the concentration profiles, and trays efficiencies in multicomponent distillation columns. The proposed model is based on Maxwell Stefan equations, and CFD was employed as a powerful tool to model the hydrodynamics and mass transfer. The two phases are modelled as two interpenetrating phases with interphase momentum, heat and mass transfer. The Closure model is developed for mass interphase transfer rate in ternary mixtures. The predictability of the mass transfer behaviours of multicomponent can result in a more efficient and predictable design of distillation trays. Two non-ideal ternary mixtures were studied. The tray geometry and operating conditions are based on the experimental works of Kalbassi and the composition profiles, tray efficiencies, and point efficiencies of mixtures were presented. The obtained results were confirmed by the experimental data. The results indicate that the values of individual component tray efficiencies and point efficiencies for these multicomponent systems were considerably different which confirm the interactive nature of the mass transfer in multicomponent mixtures. These mixtures also illustrated different point efficiencies across the tray because of the composition dependency of these mixtures. The average relative error for the prediction of efficiencies is about 8 %, which indicates the accuracy of the model.

A paper about the slope of the equilibrium line

There is no simple definition of the slope for multicomponent systems because the vapour liquid equilibrium is represented by a surface (which lies in hyperspace for more than 3 compounds). Thus, for multicomponent systems any pseudo-binary method for estimating tray efficiencies and HETP must rely, in part, on an approximate method of estimating the slope.The objective of this paper is to present a new method of approximating the slope in multicomponent systems based on differentiation of the phase equilibrium surface with respect to the mole fraction of the design component, defined as that compound we seek to eliminate from the mixture in a particular section of the column. There is only one design compound per column section. The approach presented here can be easily applied to absorber and stripper columns, where the concept of key components is not applicable.Two analytical approximate methods of estimating the design slope are shown to be in good agreement with the rigorous calculation even in cases where the relative volatility is not constant. These simple approximations, which need nothing beyond what is readily available from any column simulation program are adequate for design and can be programmed easily in any spreadsheet.