Packing Pressure Drop Research Articles

Three-dimensional gas–liquid flow simulation of a rotating packed bed using Eulerian porous media models

The rotating packed bed (RPB) is a typical equipment in chemical process intensification technology due to its excellent mass transfer performance. In this paper, a three-dimensional full-scale model was established based on the Eulerian two-fluid method to study the gas–liquid two-phase flow in RPBs. Three different single-phase wire screen packing pressure drop models coupled with the interfacial area model were used to construct resistance calculation methods for porous media, respectively. The results show that simulation deviations of the liquid holdup and the pressure drop of the m-K model range from 0.92 % to 27.61 % and 1.63 % to 34.59 %, respectively. In addition, the simulation accuracy of the liquid holdup of three models was obviously influenced by the rotational speed (N). The m-K model has the highest prediction accuracy at N = 500 ∼ 1500 rpm. At N = 2000 ∼ 2500 rpm, the B model has the highest prediction accuracy. Characteristics of gas–liquid flow under different conditions and nozzle designs were obtained. In particular, the impact of different nozzle designs on liquid distribution has been investigated using a new method based on user-defined functions (UDFs). A more homogeneous distribution of liquid within the packing can be achieved by increasing nozzle height, decreasing nozzle size, and increasing the number of nozzles.

Design optimization of a rotating packed bed based on dry hydraulic performance

The current study focuses on enhancing the fidelity of the hydraulic performance of Rotating Packed Beds (RPB) by modifying the conventional geometrical construction of the inner cavity, outlet pipe, and its packing. RPB technology has been playing an increasing role in intensifying different petrochemical processes, such as CO2 capture, due to the potential of a several-order-of-magnitude mass transfer enhancement induced by the HiGee field. In this context, four novel geometries of the RPB are proposed and analyzed using a validated CFD model that utilizes the porous media approach to model the pressure losses in the RPB packing. The impact of liquid distributor was also investigated and compared to the original design. Results of the modified geometries conclude that optimizing the flow pattern at the exit of the packing by modifying the inner cavity's shape reduces the total pressure drops by up to 22%. At the same time, it is found that a further decrease of 13% in the pressure drop can be achieved by attaching a nozzle at the entry of the outlet pipe. On the other hand, the modified packing that imposes a constant radial flow velocity increases the packing's pressure drop by 10%. Furthermore, the data analysis show that a lower pressure drop within the inner cavity could be achieved, in principle, by regulating the exit packing velocity or raising the free vortex pressure. Finally, it is noted that the gross pressure drop reduction, which is be obtained from combining the two former modifications, can reach up to 33% at the high gas volume flow rates. This reduction accounts for 60% of the inner cavity pressure drop, which can help avoid costly and complicated engineering designs.

Rigorous Tritium Wet Scrubber Column Modeling and Design

The rigorous steady-state equilibrium stage Tritium Wet Scrubber Column model has been developed. The model includes the six water isotopologues H2O, HDO, HTO, D2O, DTO, and T2O; heat balance; and packing pressure drop. Heat balance is particularly important in wet scrubber calculations due to evaporative cooling of air with less than 100% relative humidity. Evaporative cooling is generally beneficial, but freezing is possible with very cold dry air, making it important to understand operating limits. The pros and cons of precooling and saturation of the airstream are discussed. The Tritium Wet Scrubber Column model has been applied to scrubbing airstreams containing tritiated light water vapor and for tritiated heavy water vapor in CANDU® heavy water applications. Deuterium and tritium are recovered at slightly different efficiencies, and because of differences in the latent heat of vaporization for H2O and D2O, liquid and vapor compositions affect the column heat balance. Case studies are presented for tritiated light water vapor air detritiation and also for tritiated heavy water vapor air detritiation to provide guidance for design. Further, practical aspects of the wet scrubber column construction and operation are discussed.

Characteristic analysis of heat and mass transfer process within structured packing humidifier

Humidifiers are the important devices for humidifying the air both in life and industrial production. This paper focuses on the heat and mass transfer processes inside the counter-flow packing humidifier at atmospheric pressure. Based on mass and energy balance, the mathematical model for the humidifier is established. The finite difference method is first adopted to calculate the specific scales of the packing and the relevant state distribution of the gas–liquid species at on-design conditions. Thus, the heat and mass transfer performance of the humidifier is also carried out at off-design conditions. The simulation results show that the required packing height at the design parameters is 3.38 × 10−1 m, while the supersaturation phenomenon begins at Z = 5.76 × 10−2 m, and the humidity ratio and supersaturated humidity ratio at humidifier outlet are 1.69 × 10−1 kg/kg and 1.64 × 10−3 kg/kg, respectively. In addition, for off-design analysis, as the liquid–gas ratio increases, the outlet water temperature and outlet air temperature increase by 14.3% and 7.47%, respectively, and the humid air reaches saturation earlier as the saturation point falls from 5.76 × 10−2 to 2.7 × 10−2 m. Within the range of the simulation conditions, the maximum account of droplets entrained in the humid air reaches 1.72 × 10−3 kg/kg, while the total packing pressure drop increases with the decrease in liquid–gas ratio. The effect of liquid–gas ratio and wet-bulb temperature of inlet air on the humidifier under design parameters can provide great reference significance for the design, optimization and regulation of humidifiers.

Process design for CO2 absorption from syngas using physical solvent DMEPEG

Pre-combustion IGCC is one of the leading technologies having potential for effective control of greenhouse gas emission. Process design for CO2 Capture from power plant is becoming increasingly important in the past decades in view of the need for optimization of Capital Cost and Utility consumption. In this article, a configuration of the process design for CO2 absorption using physical solvent DMEPEG is proposed, which is described using the process flow diagram (PFD) and the Flowsheet. CO2 absorption performance of DMEPEG solvent is assessed based on a rate based mass transfer model using ProTreat® simulation software. The rate based mass transfer simulation by ProTreat software adds to the reliability of the simulation result (as evident by its acceptance within industry). The trade-off between H2 recovery (by syngas recycle) and CO2 re-absorption is described which reveals that more than 55% H2 recovery may significantly increase the load on the system (in terms of syngas processing and CO2 re-absorption).Objective of this research is to develop a detailed process model for CO2 absorption by DMEPEG solvent (to enable detailed techno-economic assessment by bottom up approach). In the second section of this article, the process of CO2 capture by physical solvent DMEPEG is explained. In the fourth section, the boundary conditions such as the inlet pressure, temperature and composition of syngas and solvent feed are defined. In the fourth and fifth section, the design and performance of the packed tower is described and the utility consumption is estimated. Moreover, the outlet condition of the solvent is described and its saturation (by CO2) is estimated. In the fourth section, the strategy of solvent heating to recycle the syngas to CO2 absorber (for H2 recovery) is described. Importance of CO2 absorption in solvent (at high concentration) for minimization of equipment size and utility consumption for CO2 capture is explained.Using RSR packing (6.4m Dia., 16m Ht. (9+6+1)) results in 90.7% CO2 absorption and 89% saturation of CO2 dissolved in DMEPEG solvent. Out of 3.34 kmol/s H2 fed to the CO2 Absorber (as part of syngas), 1.464% (equivalent 5.9 MW power generation by Gas Turbine in open cycle) is co-absorbed (along with CO2) in DMEPEG solvent. Out of this co-absorbed H2, 55.7% is recovered which is equivalent to 3.267 MW Power Generation.In terms of hydraulic design, the CO2 Absorber using RSR packing operating at 72.5% flood condition results in packing pressure drop of 87.5Pa/m (1.4kPa). Packed section diameter and height is suggested for various random packing materials (tower internal) to achieve almost comparable gas absorption performance.

Packing with Stamped Horizontal Lamellae Operating at Extremely Low Liquid Loads – III. Packing Pressure Drop

AbstractIt has been discussed in previous papers [1–7] that the design of packings capable of operating at extremely low liquid superficial velocity allows the development of effective countercurrent flow packed bed columns even if the concentration of the absorbed component is very low, the absorption is an equilibrium process, and the gas is well soluble in the liquid phase. The construction of the new packing is described in [7]. The present paper reports the results of an investigation of the pressure drop for dry and irrigated packings up to a gas velocity equal to 3 m/s (FG factor equal to 3.3 kg1/2 m–1/2 s–1) as well as the equations for its calculation.

CO oxidation over structured carriers: A comparison of ceramic foams, honeycombs and beads

This work aims an experimental comparison of different packings on the basis of their pressure drop, mass and heat transfer properties. Ceramic foams, beads and a honeycomb monolith were used as carriers in the oxidation of carbon monoxide. The carriers were coated with active Pt/SnO 2. The CO oxidation rate was measured in the regime of external diffusion control at superficial gas velocities between 1 and 10 m/s. The volumetric rate coefficients and the pressure drop of packings with similar geometric surface area decreased in the sequence particles > foams > honeycomb. The magnitude of the temperature gradient along the catalytic bed decreased as going from honeycomb over larger particles to foams and small particles. Foams were superior over particle beds from the viewpoint of combined high mass transfer and low-pressure drop. The main advantage of foams as compared to honeycomb resided in the radial mixing enabling a better heat transfer to the reactor walls.

Process Tomography: An Option for the Enhancement of Packed Vapor−Liquid Contactor Model Development

A multitude of packed vapor−liquid contactor mass-transfer and hydraulic models exist in the literature. With few exceptions, the development of these models has been based on a very limited understanding of the microscale hydraulic phenomena inside the contacting column. Recently, the use of X-ray tomography has been shown to be an effective technique for imaging flow patterns in multiphase contactors. This paper describes the potential benefits that X-ray tomography analysis can bring to the understanding and modeling of the vapor−liquid contacting process. The technology has significant potential for enhancing the prediction of both mass-transfer efficiency and packing pressure drop of commercial packed columns.

Pressure drop of arranged packings with vertical walls

Among the known types of packings, arranged packings with vertical walls have the lowest pressure drop for one transfer unit at comparable free volume as well as the highest efficiency at a given pressure drop. Reliable equations are derived for pressure drop determination in industrial apparatuses filled with this kind of packing. The pressure drop is presented as a sum of two terms-pressure drop (in the vertical channels) of the packing rows themselves and local pressure drop of the boundary sections between the rows. The experimental data for dry packing pressure drop, available in the literature and newly obtained, are described by new equation with mean deviation of 9.3%. Equations for determination of wetted packings pressure drop up to the loading point and above it are obtained, too. The proposed equations can also be used to determine the loading point.

Performance characteristics of a packing with boundary layer turbulizers. III. Liquid film controlled mass transfer

Liquid film controlled mass transfer in a novel design of a honeycomb packing (Turbo-Pack) with turbulizers in the region of the boundary layer has been studied. For comparison, packings without turbulizers have also been investigated. Dimensionless equations for evaluation of mass transfer are proposed and their constants have been analyzed statistically. It is shown that the presence of turbulizers leads to an increase of the mass-transfer coefficient by up to 55% and to a decrease of up to 4.5-times in the packing pressure drop per mass transfer unit. A comparison over the most effective packings known from the literature shows that, as far as its low pressure drop per mass transfer unit is concerned, the novel packing is superior to all other packings.