Gas-side Mass Transfer Coefficient Research Articles

Process Intensification in Distillation using HiGee Rotating Packed Bed

For decades, improving the gas-side mass transfer coefficient in rotating packed beds has been a formidable challenge. Distillation, often limited by gas-phase resistance, requires substantial innovation to enhance these coefficients. Rotating packed beds offer a distinct advantage over conventional columns, primarily due to the intense micro-mixing within fluid channels. This micro-mixing significantly boosts mass transfer between phases and facilitates rapid attainment of steady-state conditions, making them a superior choice for processes where gas-side resistance is the bottleneck. The current study emphasis on the mass transfer performance of rotating packed for acetone water system with two different packing materials viz., wire mesh and ceramic beads. Working principle of HiGee, typical flow pattern, modeling equations have been discussed in this paper. The effects of rotational speed, gas flow rates and radial thickness of the packing on mass transfer performance were also investigated. The mass transfer coefficients of the rotating packed bed HiGee were increased with increasing the rotational speed. The Height Equivalent to Theoretical Plates (HETP) of the rotating packed bed used in this study was 5-6 times less than the conventional packed columns. This study contributes to significantly advancing the industrial applications of rotating packed beds.

Enhancing NOx removal in a high-gravity rotating packed bed with gaseous ClO2 oxidation-absorption: Kinetic, mass transfer, and cost analysis

The application of ClO2(g) for NO oxidation presents a promising approach to improving air pollution control technology. In this study, an integration of ClO2(g) with absorption using a high-gravity rotating packed bed (HiGee RPB) was proposed for NOx removal. The results showed that ClO2(g) has a comparable oxidation efficiency (close to 100%) to O3 in converting NO to NO2, while the dosage of ClO2(g) required was two times smaller than that of O3. The gas-phase oxidation kinetic analysis between ClO2(g)-NOx, using an ideal plug flow model, simulated the potential amount of NOx species produced in a short reaction distance in the pipeline. Furthermore, at higher gas-liquid ratios and in high-gravity fields, the effective mass transfer interfacial area for NO2 absorption was mainly controlled by the liquid film rather than droplet behavior, resulting in decreased absorption capacity. The empirical model for predicting the gas-side mass transfer coefficient confirmed that the interaction between mass transfer performance and chemical absorption was independent. Therefore, selecting the appropriate absorbent is a key factor in achieving high-loading NO2 concentrations after oxidation by ClO2(g). Another interesting finding is that balancing system energy consumption and the target treated NOx concentration played a critical role in enhancing the NOx absorption capacity. The cost analysis showed that substituting existing scrubbers with RPB processes could facilitate NOx absorption capacity (g-NOx/kWh) with cost-effectiveness. Overall, this study provides valuable insights into the development of effective and efficient NOx removal technologies, and future research in this area can build on these findings.

A model for the absorption rate in electrically charged droplets

Charged droplets are produced by electrosprays or sometimes generated by natural phenomena, and nowadays their application is also investigated as a tool for process intensification in heat and mass transfer processes typical of chemical engineering. This paper analyses the absorption of slightly soluble trace gases into electrically charged droplets: it reports a new mass transfer model taking into account the electrophoretic motion of gas molecules and the possible alteration of the interfacial properties induced by the imposed electric charges. The model is successfully validated against existing experiments on the absorption of SO2 into electrified water droplets. These experiments are useful both for the robustness of data available for the SO2-air-water system and for its significance in atmospheric chemistry and physics, and chemical engineering applications.Considering the same SO2-air-water system as a case study, the model predicts that the absorption rate for a droplet produced with a conventional electrospray is up to 42% faster than that of an uncharged droplet with the same size and morphology, while the electrophoretic drift provides an improvement of the gas-side mass transfer coefficient mainly for droplets finer than 500 µm.

NOx removal and copper recovery from the leaching process for waste printed circuit boards: performance evaluation and potential environmental impact assessment.

Resource recovery is crucial for small- and medium-sized enterprises to attain a circular economy. The economic benefits of recovering precious metals from electronic waste, such as waste printed circuit boards (WPCBs), are hindered by secondary pollutant emissions from pretreatment processes. This study aims to recover copper from the WPCB acid leaching process and reduce NOx emissions through the use of a high gravity rotating packed bed (RPB). The results indicate that the copper recovery ratio increases to 99.75% through the displacement reaction between iron powder and copper nitrate. The kinetic analysis of copper dissolution was employed to simulate the NOx emissions during acid leaching, with an R-squared value of 0.872. Three oxidants, including H2O2(aq), ClO2(aq), and O3(g), with pH adjusted to different NaOH concentrations, were used to remove NOx. The greatest NOx removal rate was achieved using a 0.06M NaOH solution, with a removal rate of 91.2% for ozone oxidation at a 152-fold gravity level and a gas-to-liquid (G/L) ratio of 0.83. The gas-side mass transfer coefficients (KGa) for NOx range from 0.003 to 0.012 1/s and are comparable to previous studies. The results of a life cycle analysis indicate that the NOx removal rate, nitric acid recycling rate, and copper recovery rate are 85%, 80%, and 100%, respectively, reducing the environmental impact on the ecosystem, human health, and resource depletion by 10% compared to a scenario with no NOx removal.

Experimental and numerical investigation of gas-side mass transfer in Taylor flow

Taylor flows are of great interest for industrial application where efficient gas absorption is needed. Literature however scarcely relates to the gas-side mass transfer coefficient kG in Taylor flows. In this work, the authors selected and developed an experimental method, based on bubble expansion record, to estimate kG value in a millimetric channel of circular section, fed with nitrogen gas and pure ethyl acetate (EA). The experiments provided an order of magnitude of a few mm.s−1 at least for kG, for a two-phase velocity UTP ∼ 0.1 m.s−1.CFD simulations completed the experimental investigation and further estimated the order of magnitude, with kG∼10-2 m.s−1 when 0.09<UTP<0.18 m.s−1. The transport of EA inside the bubble suggests a significant contribution of diffusion in regard with the convective effects. kG is found to be sensitive to UTP, and to the temperature via the gas diffusivity and also via the bubble expansion leading to an increase in bubble velocity. The dependence of the gas-side Sherwood number to the Péclet number is similar to previously reported observations concerning a spherical bubble freely rising in quiescent liquid.This study thus provides the means to evaluate the gas-side resistance for any gas–liquid system in Taylor flows, a resistance that was usually simply dismissed in previous works. As an example, the authors demonstrated that, in Taylor flows, for a gas–liquid system of industrial interest (diluted CO2 in 30 wt.% N-methyldiethanolamine aqueous solution), gas-side mass transfer resistance is lower than the liquid-side one by at least one order of magnitude.

Process intensification through the application of centrifugal field: An experimental study of absorption processes using the falling film microreactor

In this work, liquid and gas side mass transfer characteristics were investigated within a centrifugal field using the falling film microreactor (FFMR). Enhancement in mass transfer rates were assessed by relating the absorption efficiency of the processes conducted within the centrifugal field to those in which liquid flows are purely-driven by gravity. The liquid side rotational mass transfer coefficients (kL) determined were considerably higher than those without rotation. Similarly, relative increase in rotational gas side mass transfer coefficient (kG) was also significantly high (up to 42%).The liquid side experimental data were well predicted by the modified correlation (a power law equation modified to consider the effect of the applied external force, geometry of the system, hydrodynamic characteristics and physical properties of the fluids employed) at lower rotational speed but deviated considerably at higher rotational speeds while, the gas side experimental data were well predicted by the correlation.

Development of an innovative process for post-combustion CO2 capture to produce high-value NaHCO3 nanomaterials

• An innovative process using SG for CO 2 capture from flue gas was developed in aspen plus v.10. • The flue gas flow rate used in the process was 44.75 tph and contained 0.0023 mol% SO 2 and 13.33 mol% CO 2 . • The process was designed to remove all SO 2 , and capture 90 mol% of CO 2 from the flue gas to produce valuable NaHCO 3 nanoparticles. • The hydraulics and mass transfer of the gas-liquid systems were obtained and the CAPEX, OPEX, and LCOC of the process were calculated. • The process was able to capture 8.144 tph of CO 2 and produce 15.545 tph of NaHCO 3 nanoparticles. An innovative post-combustion process using aqueous sodium glycinates solutions (SGS) for CO 2 capture from a split flue gas stream emitted from the 600 MWe coal power plant, used in the Wolverine Clean Energy Venture (WCEV) project, was developed in Aspen Plus v.10. The flue gas flow rate used in the process was 12.43 kg/s (at 353.15 K and 101.33 kPa) and contained 0.0023 and 13.33 mol% of SO 2 and CO 2 , respectively. The overall process includes 5 main units designed to remove all SO 2 and capture more than 90 mol% of CO 2 in the flue gas stream, while producing high-value, salable sodium bicarbonate (NaHCO 3 ) nanomaterials to offset the total process costs. The hydraulics, mass transfer characteristics, and process performance obtained using Aspen Plus were discussed. Also, the capital expenditure (CAPEX), operating expenditure (OPEX), and Levelized cost of CO 2 capture (LCOC) were calculated to assess the feasibility of this process. The hydraulics in the SO 2 washing and CO 2 capture units showed a pressure drop of 12 and 1 kPa, respectively, and the behaviors of the liquid holdup and normalized packing specific wetted surface area were similar in both units. The gas-side mass transfer coefficients were orders of magnitude greater than the liquid-side mass transfer coefficients. The process was able to capture 2.352 kg/s of CO 2 and produce 4.486 kg/s of valuable NaHCO 3 nanomaterials. Also, the calculated CAPEX, OPEX, and LCOC of the process for a 30-year plant lifetime were ($4,450,552), (233.00 $/h) and (35.49 $/ton of CO 2 captured), respectively.

Study on the Effective Mass Transfer Area and the Local Gas-Side Mass Transfer Coefficient in a Rotor–Stator Reactor

Study on the Effective Mass Transfer Area and the Local Gas-Side Mass Transfer Coefficient in a Rotor–Stator Reactor

New electroscrubbing process for desulfurization

A new process for removing sulfur from gas using electricity is presented. The process combines electrochemical production of active oxidizing species with an oxidative scrubber for desulfurization. Reactions for the electrochemical cell and the scrubbing tower are presented and a scrubbing set-up with a continuous electrolyte recirculation is validated on synthetic biogas. The test shows that a gas flow of 200 L/h with 1330 ppm H 2 S can be cleaned down to non-detectable levels of sulfur in a single step, at a current efficiency of 29%. This is a very high removal percentage for a high concentration of H 2 S. Solid sulfur can be removed from the system after the experiments. The sulfur has traces of NaClO and no other products were detected. A simple model based on estimated gas side mass transfer coefficients were used to estimate a scrubber height of only a few centimeters. The experiments supports the model. This technology allows for a robust implementation of sulfur free applications in a future green fuel and green chemistry like Power-to-X (PtX) and carbon capture and utilization (CCU). Sulfur compounds are poison for most heterogeneous catalysts, thus for carbon utilization, the carbon gas source has to be desulfurized .

Modelling atmospheric emissions from wastewater treatment plants: Implications of land-to-water roughness change

Atmospheric emissions from passive liquid surfaces, such as wastewater treatment plants (WWTP), are common sources of impacts to the environment and to the health of communities, due to odours, greenhouse gases and other air pollutants. Emission models have been broadly employed for assessing these emissions, with the wind friction velocity (u∗) being a key variable. The usual practice in the context of WWTP is to parametrise u∗ based on reference wind speeds measured over the land, without considering the internal boundary layer (IBL) development due to the change in aerodynamic roughness as the wind blows from the land to the liquid surface, nor the stability of the wind flow. The potential consequences of these conceptual inconsistencies are major knowledge gaps in emission modelling. Addressing these, a customised computation was implemented to couple the wind friction parametrisation with the evolution of the IBL downwind of the land-to-water roughness change. A sensitivity analysis with different emission models, considering ranges of fetch, wind speed and surface roughness encompassing typical conditions in WWTP, showed that not incorporating the roughness change leads to systematic overestimation of u∗ and the overall mass transfer coefficient KL for two compounds analysed (liquid phase and gas phase-controlled volatilisation). A modelling approach was devised, comprising the u∗ parametrisation that incorporate the roughness change combined with the Prata-Brutsaert emission model and alternative calculation of the gas-side mass transfer coefficient kG from local IBL variables. Evaluation against experimental data and physical considerations support the adoption of this approach for modelling the volatilisation of compounds from passive liquid surfaces in WWTP. A simplified equation to approximate u∗ after a change in roughness is presented, which can be used for quick emission modelling of liquid phase-controlled compounds. Furthermore, a preliminary exploration demonstrated that the effects of atmospheric stability on the response of u∗ to the land-to-water roughness change can be substantial under certain conditions.

A machine learning model for predicting the mass transfer performance of rotating packed beds based on a least squares support vector machine approach

Rotating packed beds (RPBs) have been widely noted due to its superior gas-liquid mass transfer performance compared to conventional packed bed for CO2 absorption. The overall volumetric gas-side mass transfer coefficient (KGa) is selected as one of the key parameters for the screening and evaluation of RPBs. Existing theoretical and semi-empirical models for the KGa are easy to be used but have a poor accuracy and generalization ability. In this paper, a machine learning model based on least squares support vector machine (LSSVM) is developed to predict the KGa more accurately for CO2-NaOH chemical absorption system in different types of RPBs. Unlike the conventional prediction models, the input parameters are selected by multiple correlation analysis in the model establishment. Then, the proposed model is comprehensively evaluated by using four evaluation indicators, including determination coefficient, mean relative error, Root mean square error and standard deviations. The results show that the proposed model has the prediction performance with R2 = 0.9808 and RMSE = 0.0055 for testing set. In addition, the model performance is compared with the multiple nonlinear regression and artificial neutral networks. The results show that the proposed model has a superior performance for predicting the KGa of CO2 absorption in RPBs.

Modeling and analysis of CO2 capture by aqueous ammonia + piperazine blended solution in a spray column

Chemical scrubbing using NH3/PZ solution is a promising pathway for mitigating CO2 emission from fossil-fuel combustion. Herein, we developed an advanced model that can predict CO2 absorption using the blended solvent in a spray column. The model was established in the computational fluid dynamics framework coupled with the properties of the blended solvent. The blended properties were evaluated using the linear combination of each single solvent. The established model was also verified by our previous experimental results. The deviations were found to be within ±15%. Further case studies revealed crucial characteristics of the scrubbing process. Due to the entrainment effect, intensive back-mixing behavior was observed in the gas flow. Energy analysis showed that the heat for water warming-up and evaporation mainly comes from the heat released by the CO2 absorption. The profiles of the gaseous species demonstrated that gaseous concentrations of NH3 and H2O vapor quickly approached their equilibrium values, whereas gaseous CO2 concentration exhibited different variation trends along the column. We also found that the gas-side mass-transfer coefficient was two orders of magnitude greater than the liquid-side. Moreover, the spatial separation of the maximum mass-transfer coefficients and the driving force led to a low CO2 absorption rate. The comparisons of the upward and downward spraying schemes indicated that the upward spraying can mitigate the spatial separation and increase droplet residence time and volume fraction, significantly improving the CO2 removal efficiency from 48.2% to 55.9%.

Enhanced mass transfer and reduced pressure drop in a compound rotating zigzag bed

A rotating zigzag bed (RZB) had achieved the commercial application of Higee in continuous distillation processes, and then a compound rotating zigzag bed (CRZB) was developed from the RZB. The CRZB rotor was composed of a disk layer including several perforated concentric circular ripple disks fixed on a perforated rotating ring at the inner part of the rotor and several coupled rotational-stationary baffles at the outer part of the rotor. And a stationary four-arm liquid distributor was located at the eye of the CRZB rotor. The effective interfacial area (ae) and local liquid-side mass transfer coefficient (kL) of the CRZB rotor were measured by experiments of a chemical absorption of CO2 in NaOH solution, and the local gas-side mass transfer coefficient (kG) of the CRZB rotor was measured by experiments of a stripping of ethanol from an ethanol-water mixture by air. The gas pressure drop across the CRZB was measured with air-water system. Effects of gas flow rate, liquid flow rate and rotational speed on these mass transfer parameters and gas pressure drop were investigated. The stationary four-arm liquid distributor led to stronger end effect of the CRZB rotor than that of the RZB rotor. The end effect of the CRZB rotor had significant effect on the ae and kL of the rotor. The ae of the CRZB rotor was much higher than that of the RZB rotor because the total space in the disk layer of the CRZB rotor served as mass transfer zones and the CRZB rotor had stronger end effect than the RZB rotor. The local volumetric liquid- and gas-side mass transfer coefficients (kLae and kGae) of the CRZB rotor reached 2.3 times higher than those of the RZB rotor at a higher liquid flow rate and a rotational speed of 1200 rpm. The gas pressure drop across the CRZB was lower than that across the RZB, because the coupled rotational-stationary baffles were abandoned at the inner part of the CRZB rotor, which reduced the gas flow resistance and led to a lower pressure drop compared to the RZB. Thus, mass transfer was enhanced and gas pressure drop was reduced in the CRZB compared to the RZB, which showed the CRZB had excellent potential as a representative of the second-generation RZB for commercial applications.

Hydraulic and Mass Transfer Performances of a Commercial Hybrid Packing: The RSP200X-Key Modelling Parameters for Gas Treatment Applications

The use of the last generation of Raschig’s structured packings, Raschig SuperPack (RSP) has been investigated for scrubbing columns operating at high liquid loads, for their potential to increase capacity while maintaining mass transfer efficiencies at high levels. IFPEN has measured pressure drops, flooding limits, liquid and gas side mass transfer coefficients and interfacial areas for the RSP 200X. Flooding limits were in agreement with literature, however at high liquid loads and for tested X-Style RSP they were 30-40% lower than those calculated with the Winsorp Software. This indicates that extrapolation of flooding models should be used with caution to size column diameters for fluid systems and liquid loads that differ from those from which these models were derived. With the support of the present results a modified version of Winsorp has been elaborated for high liquid loads and X-Style RSP. RSP 200X develops a high interfacial area, close to the one of a standard 250 m2/m3 structured packing. One important difference however has been noted about the impact of the gas flowrate on the interfacial area. While for standard packings the gas flow rate is often considered to have only a small effect on area when operating below the loading point, the effect measured on RSP200X is significant and of the same order as for liquid load. Measurements of kLae further confirm that these latest generations of packings show different trends when compared to standard structured packings. Detailed characterization tests are therefore highly recommended to estimate the performances of these packings in terms of hydraulics and mass transfer properties. In some distant future, it is believed that CFD calculations (gas and gas/liquid) will help to better understand and model such phenomena.

Simultaneous absorption–oxidation of nitric oxide and sulfur dioxide using ammonium persulfate synergistically activated by UV-light and heat

Simultaneous absorption–oxidation process of nitric oxide (NO) and sulfur dioxide (SO2) from flue gas using aqueous ammonium persulfate synergistically activated by UV-light and heat in a novel UV-impinging stream reactor was developed. The main influencing factors, products and active species of NO and SO2 simultaneous removal were studied. The mass transfer and kinetics of NO absorption–oxidation were also investigated. The present studies show that SO2 is very easy to remove because of its very high solubility in water (SO2 removal efficiencies reach 100% under most of experimental conditions). Increasing S2O82− concentration, UV radiation power, activation temperature or liquid–gas ratio promotes absorption–oxidation of NO. Increasing solution pH, concentrations of NO and SO2 or flue gas flow inhibits absorption–oxidation of NO. The contents of O2 and CO2 have no significant effect on removal of NO. The highest simultaneous removal efficiency for NO and SO2 is 96.1% and 100%, respectively. OH and SO4− are the key oxidizers for NO removal. Absorption–oxidation process of NO meets a fast pseudo-first order reaction for NO, and can be enhanced by increasing the gas-side mass transfer coefficient and interfacial area.

Mass-transfer characteristics in a rotating zigzag bed as a Higee device

Abstract A rotating zigzag bed, as a Higee device, has successfully achieved the industrialization of Higee in the commercial continuous distillation process. To increase applicability of rotating zigzag bed in the gas-liquid mass-transfer processes, the mass-transfer characteristics of the rotor of rotating zigzag bed were examined. The effective interfacial area ( a e ) and local liquid-side mass-transfer coefficient ( k L ) were measured using a chemical absorption of CO 2 in NaOH solution. Based on two-film theory, the local gas-side mass-transfer coefficient ( k G ) was obtained from the overall volumetric gas-side mass-transfer coefficient ( K G a e ) which was measured using a stripping of ethanol from an ethanol-water mixture by air. The effects of rotational speed, liquid volumetric flow rate and gas volumetric flow rate on these mass-transfer parameters were investigated. Compared to the conventional rotating packed bed, the k L of the rotor of rotating zigzag bed was as about 2.5 times higher as that of conventional RPB rotor, and the a e and k G of the rotor of rotating zigzag bed matched with those of the rotor of conventional rotating packed bed. Therefore, rotating zigzag bed has good mass-transfer performance with a great potential for the industrial application.

Numerical simulation for mass transfer characteristics of CO2 capture in a rotating packed bed

Rotating packed bed (RPB) has owned the significant advantages for gas-liquid mass transfer process intensification. This study presented a mathematical model for mass transfer characteristics of CO2 capture in a RPB, which involved diffusion and reaction process. In current setup, main focus was given on analysis of local liquid-side mass transfer coefficient (kL), which was applied to obtain overall gas-side mass transfer coefficient (KGa) and CO2 absorption efficiency (E). The effects of operating parameters, such as Higee factor, temperature, pressure, gas and liquid flow rate, on KGa and E were investigated. The results indicate that KGa increases with increasing Higee factor, temperature and liquid flow rate and decreasing gas flow rate but is independent on pressure; E is positively dependent on Higee factor, temperature, liquid flow rate and pressure but negatively dependent on gas flow rate. Meanwhile the numerical simulation exhibits that transient droplet lifetime is the essence of process intensification for RPBs. Furthermore, the simulated values of E have satisfactory agreement with experimental and published data with maximum deviations within ±20%, which recommends this model suitable for providing the theoretical basis for future design and application of RPBs.

Modeling study on CO2 and H2S simultaneous removal using MDEA solution

This study presents a rate-based model of an absorber packed column for simultaneous absorptions of acid gases into methyldiethanolamine (MDEA) aqueous solution. The model is in good agreement with experimental data. The parametric study showed that the concentration of acid gases in the sweet gas stream increases by decrease in the specific surface area of packing. The peak of selectivity factor decreases with the increase in the mole ratio of CO2/H2S in the gas feed along the packed column. The sensitivity analysis reveals that selecting the accurate correlations of the gas-side mass transfer coefficient and specific surface area is vital.

Proton Transfer Reaction-Mass Spectrometry (PTR-MS) as a tool for the determination of mass transfer coefficients

We present an alternative technique for the measurement of mass transfer coefficients for bubble columns from the gas phase with the mass spectrometric technique of Proton Transfer Reaction-Mass Spectrometry (PTR-MS). Instead of liquid phase measurements, we apply gas phase measurements of the effluent gas phase with the PTR-mass spectrometer. The method is based on the inert gas stripping approach for the determination of Henry׳s law constant. Therein gas is bubbled through a liquid-water-compound mix, and the declining concentration of the compound in the gas phase is measured over time. For the determination of the mass transfer coefficients, the concentration over time profile is used. Experiments for determination of mass transfer coefficients were carried out in small lab scale under controlled isothermal (thermostated) conditions and with a glass frit sparger. In principle this setup could be performed offline with any detector that has a linear signal dependence over a wide concentration range. PTR-MS has the advantages of low limit of detection (ppt(v)–ppq(v)), wide linear range, and split second detection. We review the formulas for the determination of mass transfer coefficients. The relation with the equilibrium Henry׳s law constant is pointed out (extrapolation to origin considering gas holdup). We determine the overall volumetric mass transfer coefficient KLa, and moreover apply a method for the additional estimation of the liquid-side and gas-side mass transfer coefficients from KLa. Correlations of the superficial gas velocity to the gas holdup ε, the overall volumetric mass transfer coefficient KLa, the liquid side and gas phase volumetric side mass transfer coefficients kLa and kGa, as well as the ration kLa /ε are reported. The results demonstrate the suitability of PTR-MS to the determination of mass transfer coefficient for bubble columns.

Kinetics of CO2 Absorption in Aqueous Potassium L-prolinate Solutions at Elevated Total Pressure

Amino acid salts are promising absorptions for CO2 capture. This work investigated six common potassium amino acid solutions: L-proline, sarcosine, glycine, β- alanine, taurine, and L- threonine solutions using wetted-wall column at 313K and atmospheric pressure (1bar). We found potassium L-proline solution has significant mass transfer properties similar to 30 wt% MEA. The influence of total pressure in wetted-wall column on CO2 absorption rate in potassium L-prolinate solutions is determined. It is found that elevated total pressure has positive effect on CO2 absorption rate. The CO2 absorption flux increases approximately by 40% from 1bar to 3bar when CO2 inlet concentration is 10%. What's more, the gas side mass transfer coefficient is found not only dependent on the hydrodynamic conditions of wetted-wall column, but also the total pressure in the apparatus. The analytical relations between the hydrodynamic conditions of the column and kg in wetted-wall column at different pressures are got in this work, and the gas mass transfer coefficient kg is found decreases by 86% from 1bar to 3bar.