Liquid viscosity and flow rate effects on interfacial area in packed columns

The effective interfacial area for chemical absorption in a laboratory column has been reported to be a function of liquid viscosity and gas superficial velocity. In this study, liquid viscosity was varied in the range of 0.95 × 10−3 to 4.5 × 10−3 Pa·s, while gas superficial velocity encompassed the range of 48.0 × 10−3 to 173.0 × 10−3 m/s. A transition in the formation of the effective interfacial area was observed and related to the interaction between liquid viscosity and gas flow conditions. A correlation effectively predicting this transition behavior is developed on the basis of the liquid phase capillary number and the gas phase Reynolds number.

Experimental study on the spray characteristics of an internal-mixing gas-liquid injector

Experimental studies on simultaneous removal of CO2 and SO2 in a polypropylene hollow fiber membrane contactor

Impact of physico-chemical properties on falling liquid films flow over flat and corrugated surfaces

In contrast to gas absorption, the most expensive part of the gas purification process, the stripping of dissolved gases from spent chemically reactive absorbing solutions has received remarkably little attention from either a fundamental or a practical view point. The effect of operating variables on the plate efficiency or packed height of regenerators is largely unknown and no design procedures are available for their estimation. In this thesis an extensive set of measurements of mass transfer coefficients obtained in a pilot scale regenerator using the Carbon dioxide-Monoethenolamine system have been obtained. The desorption column was of 0.152 m (6 in.) in diameter and packed with 0.0127 m (1/2 in.) Raschig rings to a height of 1.64 m. The effect of five operating variables: liquid flow rate; vapour flow rate; pressure; (or temperature) carbonation ratio and MEA concentration on mass transfer coefficients has been investigated.Equilibrium solubility data for Carbon dioxide - Monoethanolamine - Water system has been correlated. It has been found that the equilibrium partial pressure of carbon dioxide is independent of monoethanolamine concentration below a carbonation ratio of about 0.45 and depends only on carbonation ratio and temperature. For carbonation ratios of greater than about 0.45, the equilibrium partial pressure of carbon dioxide also depends on monoethanolamine concentration. This is also in conformance with the reaction mechanism of carbon dioxide with monoethanolamine. The results reported here represent the first comprehensive investigation of the influence of plant operating variables on the performance of a solvent regeneration column of semi-commercial scale. The key finding is that the 173 experimentally determined measured mass transfer coefficients are predictable from first principles to within + 25% on average. Stripping process appear to be controlled entirely neither by the gas nor the liquid film resistances; rather, each is important with the dominance of one over the other varying with the vertical position in the column.The overall mass transfer coefficient based on the liquid phase was found to increase with increasing liquid flow rate for most of the operating conditions. The effect of liquid flow rateis carbonation ratio dependent. The effect is stronger at high carbonation ratios and becomes weaker at low carbonation ratios. It is particularly interesting to note that for very low carbonation ratios, increasing liquid flow rate can actually decrease the overall mass transfer coefficient.Carbonation ratio has a very strong effect on the overall mass transfer coefficient. The effect of carbonation ratio is gas rate dependent; at lower gas rate, the effect is strongerand at igh rates the effect is moderate. Over the range of operating variables investigated, an increase in vapour flow rate increases the overall mass transfer coefficient.The dependence of vapour flow rate is a function of carbonation ratio; being stronger at lower carbonation ratios and weaker at high carbonation ratios.The influence of pressure is peculiar: the gas film resistence decreases and the liquid film resistance increases as the pressure is increased. Thus, exhibiting a minimum value of the overall mass transfer coefficient. An increase in monoethanolamine concentration results in a decrease of overall mass transfer coefficient. The effect of reboiler efficiency on the overall mass transfer coefficient has also been evaluated. An increase in the reboiler efficiency decreases the performance of the desorption column but the overall performance increases as the efficiency of the reboiler increases. However, the effect of the reboiler efficiency is very mild.Two models, referred to as the physical and the chemical model, based on the two film theory were proposed to explain the effect of various operating variables on the mass transfer coefficient. The chemical model is found capable of correctly predicting the magnitude and trend of KOLa a with changing operating conditions within the accuracy of the experimental data. The effect predicted by the physical model on the other hand is higher by a factor of about 2 as compared with the experimental findings.Finally, a detailed procedure for the design of desorption columns and the evaluation of the performance of existing desorption columns for CO2-MEA-H2O system based on the chemical model is presented. Only fundamental physico-chemical data are required for the design and this permits optimum conditions for packed regenerators to be chosen. Computer programs for rigorous design and evaluation of existing desorption columns are also presented.

Results of experimental study of the effect of initial maldistribution of structured packing irrigation on efficiency of binary mixture separation are presented in this article. The studies were carried out in the experimental distillation column with the diameter of 0.9 m using the R114 and R21 freon mixture. Experiments were performed on the structured Mellapak 350.Y packing of stainless steel 316L, containing 19 layers with the total height of 4.016 m at the ratio of mole liquid and vapor flow rates L/V = 1 and 1.7, respectively, and the pressure in the upper part of the column ptop = 3 bars. Nonuniformity at the packing inlet was generated via the blocking of some holes in the liquid distributor. Here, we present some results on efficiency of mixture separation, pressure drop on the packing, distribution of local liquid flow rate under the packing over the cross‐section and on the column wall within the range of vapor loading factor (0.69 < Fv < 1.61 Pa0.5), as well as experimental data on distribution of local concentration of the low‐boiling component over the cross‐section and along the height of the structured packing. It is found out that significant maldistribution of mixture concentration and liquid flow rate over the cross‐section slightly changes along the height in the lower part of the column at a change in the degree of packing irrigation nonuniformity at the inlet. It is shown that efficiency of mixture separation depends considerably on the value of parameter L/V, vapor flow factor Fv, and size of the zone underirrigated by liquid at the inlet. In the studied range of liquid and vapor flow rates, the relative pressure drop on the packing does not depend on the ratio of liquid and vapor flow rates L/V and degree of irrigation maldistribution. © 2013 American Institute of Chemical Engineers AIChE J 60: 690–705, 2014

Residue particles with volume median diameters ranging from 23 to 68 nm were made by dispersing KNO3 or MnCL2 · 4H20 solutions with commercially available pneumatic nozzles at liquid flow rates of 0.07 and 0.021 cm3/s and atomizing air pressures (gauge) ranging from 276 to 3447 kPag. Droplets with median diameters of 1.5 ± 0.3 μm were made at the 0.07 cm3/s liquid flow rate, which represents a nearly 10-fold increase in liquid flow rate achieved with Collison atomizers used to generate droplets of similar sizes under conditions specified by their manufacturers.

Droplet disintegration behavior on slender cylindrical objects is critical in various applications. This work investigates droplet impact dynamics on hydrophilic cylindrical glass fibers by using a high-speed imaging method. The influences of liquid viscosity, surface roughness, and surface tension are examined, revealing two distinct disintegration patterns: T-shaped and wing-like. T-shaped disintegration is a never-reported phenomenon that only occurs under very low viscosities, whereas wing-like disintegration tends to appear under higher viscosities and challenges the previous understanding that high viscosity promotes liquid wrapping on fibers. A regime map is constructed by varying impact velocity and liquid viscosity, and an empirical threshold model is proposed. Besides, surface roughness can also enhance wing-like disintegration, equivalent to the effect of directly increasing liquid viscosity. Additionally, a second regime map is developed by varying impact velocity and surface tension, and a theoretical threshold model based on the Plateau-Rayleigh theory is established. This work extends the understanding of droplets impacting fibers, illustrating that droplet disintegration is not necessarily favored by low-viscosity droplets or by surface hydrophobicity.

Cocurrent gas—liquid flow in packed columns

Volatile organic compounds (VOCs) emissions can cause environmental problems and public health. Absorption is an effective method to reduce VOCs emission because it provides high capacity and low operating costs. In this work, microchannel was applied to increase mass transfer and interfacial area between the gas and liquid solvent. Moreover, a stainless steel mesh was used to prevent dispersion of one phase into the other. The stainless steel mesh was placed between two channels gas- and liquid-sides of the channel. The stainless steel mesh size was varied by using stainless steel mesh number 100, 200, and 300. Toluene was used as a representative of VOC and vegetable oil was used as a liquid solvent. The result of this work was found that the gas to liquid solvent flow rate ratio was a factor to control separation of gas and the liquid solvent. Moreover, size and surface property of stainless steel mesh played a crucial role in keeping gas and the liquid solvent separated. In addition, the removal efficiency of toluene depended on the influence of gas flow rate, liquid flow rate, channel length, channel thickness, mesh size and inlet gas concentration. Moreover, the removal efficiency of toluene was up to 97 % in this work. Finally, the liquid-side volumetric mass transfer coefficients in this work were calculated and found to be as high as 0.00165 s-1.

Investigation of liquid flow morphology inside a structured packing using X-ray tomography

Hydrodynamics characteristics of HDS trickle bed test reactor

Liquid flow distribution has been a major concern when scaling up random packed columns. This study concerns the measurements of liquid flow distribution in a large scale column packed with 25.4 mm stainless steel Pall rings. The liquid flow distribution was studied with packed bed height from 0.9 to 3.5 m, liquid flow rate from 2.91 to 6.66 kg/m2·s, and gas flow rate from 0 to 3.0 kg/m2·s. In addition, three systems, water/air, aqueous detergent solution/air and Isopar/air, were used to study the effect of liquid physical properties on liquid flow distribution, and two different liquid distributors were employed to test the effect of liquid distributor design. It was found that liquid flow distribution was strongly influenced by liquid distributor design, packed bed height, gas flow rate and liquid viscosity, slightly influenced by liquid flow rate, but not by liquid surface tension.

A novel process for oxygen absorption from air using hollow fiber gas-liquid membrane contactor

The dependence has been measured of the interfacial area and the number of transfer units for gas side resistance controlled absorption on the flow rate of gas and liquid at counter- and cocurrent flow arrangement. The measurements have been carried out for a vertical expanded metal sheet packing exhibiting a strong dependence of the interfacial area on the density of irrigation. The interfacial area has been measured by absorption of carbon dioxide into a solution of sodium hydroxide under the conditions of the pseudo first order reaction. The number of transfer units has been measured by absorption of sulphur dioxide also into a solution of sodium hydroxide. In addition, the pressure drop has been correlated against the flow rate of gas and liquid.