Modeling and Experimental Studies of Mass Transfer in Cotton Fabrics

Chemical Engineering Science, 1989

Correlations for predicting gas-liquid and liquid-solid mass-transfer coefficients in rotating packed beds are developed. They are based on laminar liquid film flow on a rotating blade and rotating disk, and the assumed random distribution of surfaces in the rotating bed. Both penetration theory and the complete convection-diffusion model are used and the results are compared. The use of penetration theory at lower rotational speed is justified by this comparison. Similarities and differences with gravity film flow and conventional packed beds are outlined. The superior performance of rotating beds is predicted.

Chemical Engineering Science, 1997

Hydrodynamics and mass transfer characteristics in a cross-flow rotating packed bed (RPB) were studied. Models describing the liquid film flowing on the wire gauze packing, the liquid droplet size in the voids, the gas pressure drop, the gas pressure and velocity radial distribution and liquid flow direction have been established. Three different types of mass transfer processes in cross-flow RPB were studied. Mass transfer model was established based on surface renewal model. The calculated results agree well with that of experiments. Experiments show that: The gas flow rate can be as high as 15 m:s and even higher, therefore the diameter of RPB can be greatly reduced compared to that of counter-current RPB; For the liquid side controlling processes, the height of mass transfer unit is 2.5-4 cm, which is close to that of countercurrent flow RPB..

Industrial & Engineering Chemistry Research, 2001

A model for the concentration of the solute in the gas in a packed column with a countercurrent flow of gas and liquid was developed. The mass-transfer coefficient was needed for the model solution. A 0.61 m diameter column filled with 38-mm ceramic Intalox saddles was used to measure mass-transfer coefficients of air-water and air-carboxymethylcellulose (CMC) solution systems. A 1.2 m diameter column filled with 50-mm ceramic Intalox saddles was also used with an air and calcium chloride solution. For varied flow rates of air from 1422 to 8017 kg m -2 h -1 and water (or the CMC solution) from 3888 to 15 516 kg m -2 h -1 , the measured concentrations of water vapor in air at the bed exit were within 2% with the model prediction. For the aircalcium chloride solution with air flow rates of 1872-7740 kg m -2 h -1 and liquid rates of 12 276-45 980 kg m -2 h -1 , the average deviation between the measured concentrations and the predicted values was about 9%.

Nucleation and Atmospheric Aerosols, 2023

The article presents the results of the study of the laws of motion of cotton particles in the working chamber of the separator, located along the inlet pipe of the vacuum valve. When the change in the displacement of the cotton pieces in the horizontal and vertical directions over time was studied, it was found that the cotton pieces entering from the inlet pipe fell into the vacuum valve in about 0.4 s. From the results obtained, it can be seen that the main part of the cotton pieces falls on the front of the vacuum valve. The established laws can be used in the design of new constructions of cotton separators.

International Journal of Heat and Mass Transfer, 2022

A mathematical model describing the erosion or leaching of a solid material by a flowing fluid in a column is developed. This involves an advection-diffusion equation coupled to a linear kinetic reaction describing the mass transfer between the solid and fluid. Two specific cases are analysed, the first where the extracted material has the same saturation solubility and rate of mass transfer throughout the process, the second where the solubility switches after a certain amount of erosion. In the first case there are only two model unknowns, the solubility and mass transfer coefficient, in the second there is a third unknown, the second solubility. Exploiting the fact that erosion is a slow process (relative to the flow rate) a perturbation solution based on the smallness of the amount removed is developed to describe the concentration and radius throughout the column. From this an analytical expression for the extracted fraction is obtained. The extracted fraction has a large linear section which results in a simple calculation to estimate the initial solubility from a very few or even a single data point. The remaining unknowns may also be easily calculated from the formula and later data points. A numerical solution, using finite differences, is developed to verify the perturbation solution. The analytical solution is also verified against experimental data for the removal of lanolin from wool fibres with a supercritical CO 2 /ethanol solvent. Values for the mass transfer rate and two solubilities are obtained for different pressures and shown to provide excellent agreement with a series of experimental results for the extracted fraction.

Journal of the Taiwan Institute of Chemical Engineers, 2009

Rotating packed bed (RPB) in which the centrifugal force is employed plays an important role in the field of process intensification. With the help of centrifugal force, the wider operating range and the better mass transfer efficiency could be expected. Experimental results showed that the gas-phase mass transfer coefficient (K G a) increased with increasing rotational speeds, gas flow rates and liquid flow rates, but decreased with increasing the liquid viscosity. However, with the comparison of K G a in an RPB and the traditional packed columns, the enhancement of mass transfer coefficient was remarkable, up to 193-fold mass transfer efficiency in the viscous media.

Chemical Engineering Science

h i g h l i g h t s A 2D CFD model is built using a fine grid to resolve the liquid flow in an RPB. The model predictions are in reasonable agreement with observations. On increasing the MEA concentration, the degree of liquid dispersion decreases. High rotational speed decreases the holdup and increases the liquid dispersion. At a high contact angle, more liquid droplets are formed but holdup decreases.

Industrial & Engineering Chemistry Research, 2011

The flooding and mass transfer characteristics of a rotating packed bed (RPB) incorporating the split packing design innovation is studied. The air-water system is used for characterizing the flooding behavior, while mass transfer is studied for the chemisorption of CO 2 in aqueous NaOH. Danckwert's chemical method is used to infer the effective specific interfacial area (a e) for mass transfer. The variation in the liquid side volumetric mass transfer coefficient (k L a e) with operating conditions is also measured. Consistently higher values of a e and k L a e are observed for counter-rotation of the adjacent packing rings compared to co-rotation. The flooding and mass transfer results are compared with existing literature data on packed columns and conventional HiGee to evaluate the process intensification potential of the novel HiGee. The flooding limits are comparable to conventional HiGee, while the reported a e and k L a e values are higher.

Sustainability

The aim of this review is to investigate a kind of process intensification equipment called a rotating packed bed (RPB), which improves transport via centrifugal force in the gas–liquid field, especially by absorption. Different types of RPB, and their advantages and effects on hydrodynamics, mass transfer, and power consumption under available models, are analyzed. Moreover, different approaches to the modeling of RPB are discussed, their mass transfer characteristics and hydrodynamic features are compared, and all models are reviewed. A dimensional analysis showed that suitable dimensionless numbers could make for a more realistic definition of the system, and could be used for prototype scale-up and benchmarking purposes. Additionally, comparisons of the results demonstrated that Re, Gr, Sc, Fr, We, and shape factors are effective. In addition, a study of mass transfer models revealed that the contact zone was the main area of interest in previous studies, and this zone was not e...

Industrial & Engineering Chemistry Research, 2006

Liquid-to-packing local mass-transfer coefficients (LMTC) were measured in a 0.3 m diameter column with a bed height of 5.5 times the column diameter using the limiting-current technique. Several electrodes were placed at various radial and axial positions (packing heights) in the bed. Measurements were conducted at various liquid flow rates with two different liquid distributor designs: multipoint (MPLD) and single-point (SPLD) distributors. For shallow beds, mass-transfer variation with radial location and liquid flow rate using MPLD was less than that for SPLD. However, for larger bed depths, the local mass-transfer coefficient became less dependent on liquid flow rate with both liquid distributors. A mathematical model for the LMTC in a packed bed was also developed, taking into account the axial and radial positions in the bed. The model predicts the LMTC well with the root-mean-square errors (RMS) of predicted and measured values of 0.07 and 0.08 for the multipoint and single-point liquid distributors, respectively.