Gas Phase Mass Transfer Coefficient Research Articles

Performance and reaction kinetics of NO absorption by Fe(II)EDTA in a multistage zeolite absorption column-H2-MBfR system

Efficient NOX complexation absorption is a key to biological flue gas denitrification. In this study, the influencing factors, efficiency, and kinetic parameters of Fe(II)EDTA absorption of NO in a multistage zeolite absorption column were evaluated. The response surface methodology (RSM) was used to determine the ideal absorption conditions. Based on these results, a combined process of a multistage zeolite absorption column and a hydrogen-based membrane biofilm reactor (H2-MBfR) was built to verify the efficiency of denitrification. The optimal conditions for achieving maximum efficiency in the absorption of NO by Fe(II)EDTA were obtained as pH of 6.5, Fe(II)/EDTA molar ratio of 1:1.1, and temperature of 30 ℃. The kinetic parameters, including liquid phase mass transfer coefficient (KNO,L) and gas phase mass transfer coefficient (KNO,G), all increased with temperature, while the NO interfacial-area concentration (aNO) exhibited the opposite trend. The reaction for Fe(II)EDTA absorption of NO was a conjugation reaction, and its activation energy was 50.38kJ·mol-1. More than 90% of NO in flue gas on 14 days was removed in the combined multistage zeolite absorption column-H2-MBfR process, which provided a sustainable NO treatment solution without secondary pollutants or CO2 emissions and demonstrated its potential for NO removal in industrial applications.

Ammonia absorption by water droplet in a small controlled atmosphere wind tunnel

The mass transfer characteristics during ammonia absorption into a sessile water droplet in a small controlled-atmosphere wind tunnel were investigated using particle tracking velocimetry (PTV) with polystyrene microspheres. The results showed that the flow field inside the droplet transformed from Marangoni convection to Rayleigh convection in the absence of gas flow. As the gas velocity increased, the drag force-induced circulation inhibited the Marangoni convection in the initial stage of the mass transfer process and Rayleigh convection in the advanced stage. However, the suppressed Marangoni convection cells recurred at high initial ammonia concentrations. Compared with the initial ammonia concentration in the wind tunnel and droplet size, the gas velocity significantly increased the gas-phase mass transfer coefficient. Furthermore, a calculation model for ammonia absorption by a moving droplet was derived based on the Colburn analogy and the two-film theory. The gas-phase mass transfer coefficients calculated using the model coincided with the experimental results. These results will help the design of water curtains.

Perspectives on the green hybrid blend of diethanolamine-glycerol for post-combustion carbon dioxide capture via a Y-type micro-reactor

CO2 capture by aqueous primary and secondary alkanolamine solutions is a recognized technology in industrial CO2 separation processes. Yet, certain obstacles caused by high-energy consumption due to the amine regeneration demands, and the formation of thermally stable salts require to be overcome for the development of these solvents. In this paper, glycerol, as a beneficial by-product of biodiesel production, has been introduced as a second promising CO2 absorbent for aqueous diethanolamine solution in a Y-type micro-reactor with dimensions of 800 µm × 4 cm × 19 cm. The experiments of CO2 capture into the hybrid blend of DEA-Glycerol were investigated at ambient pressure and the operating temperature of 25–45 °C, volumetric gas flow rate of 100–300 ml/min, DEA concentrations of 1.5–2.5 M, and glycerol concentrations of 5–15%wt. Experimental results demonstrated that adding 10 wt% glycerol in the aqueous blend of 2.5 M DEA-Glycerol boosts the CO2 removal percentage, RP, up to 96.89%, and enhances the volumetric overall gas-phase mass transfer coefficient, KGaV, and volumetric mass transfer flux, NAaV, to 34.89 kmol/m3.h.kPa and 88.04 kmol/h.m3, respectively. Furthermore, based on the Box-Behnken statistical responses, under the constant concentration of 2 M of DEA, increasing the presence of glycerol from 5 to 10 wt% in the hybrid blend of DEA-Gly can intensify the CO2 RP, KGaV, and NAaV values by 2.12% and 8.66%, and 1.80%, respectively, illustrating the glycerol contribution on the CO2 capture process.

A green amino acid-based solvent blended with diethanolamine solution for CO2 capture using micro-contactor

The current research aims at developing an amino acid-based green technology containing a secondary alkanolamine (DEA) and L-arginine amino acid (ARG) for CO2 capture process from a gas stream in a T-type micro-contactor. To strengthen the understanding of the mass transfer of biodegradable green ARG in the micro-reactor, the mass transfer performance of CO2 absorption has been experimentally assessed under liquid flow rate (QL: 3.0–9.0 ml/min), gas flow rate (QG: 120.0–300.0 ml/min) at a constant temperature of 45 °C, and atmospheric pressure. The aqueous composition of the blended solution was DEA-ARG (35–0 wt%), DEA-ARG (31–4 wt%), DEA-ARG (27–8 wt%), and DEA-ARG (23–12 wt%). It was found that an increase in the solvent flow rate from 3.0 to 9.0 ml/min enhanced the CO2 absorption efficiency (θ), volumetric gas-phase mass transfer coefficient (KGaV), and volumetric molar flux (NGaV) by 2.5, 12.8, and 2.6%, respectively. However, an increase in the gas flow rate from 120.0 to 300.0 ml/min reduces the efficiency by 6% but improves the KGaV and NGaV by 88% and 225%, respectively. Additionally, the KGaV values followed a declining trend as the contribution of the DEA in the blended solution increased. Employing response surface methodology (RSM), the optimized values for CO2 absorption efficiency and KGaV were attained 92.93% and 69.40 kmol/m3 h kPa for QL of 9.0 ml/min, QG of 263.4 ml/min, and DEA-ARG concentration, CDEA-ARG of (23–12 wt%). Comparing the gas–liquid mass transfer characteristics of the aqueous DEA-ARG mixture with the traditional aqueous amine solutions, it was illustrated that the presence of L-arginine amino acid with high composition of 12 wt%, as a substitute organic promoter in aqueous DEA 35 wt%, can boost the performance of CO2 absorption process.

Modeling of NO mass transfer characteristics absorbed in sodium persulfate solution with a bubble reactor

ABSTRACT: Sodium persulfate solution is considered as an effective wet denitrification medium, however, it is unclear that the influence of the operating conditions on mass transfer characteristics parameters during the absorption of NO with sodium persulfate solution. To determine the key mass transfer characteristics parameters, the specific interfacial area and the mass transfer coefficients were determined based on the Danckwerts method during CO2 absorption in a bubble column. and were calculated by correlations between the mass transfer coefficients of NO and CO2. Results showed that the specific interfacial area increased 77.64 m−1, the liquid phase mass transfer coefficient increased 2.49 × 10−4 m·s−1, and the gas phase mass transfer coefficient increased 0.71 × 10−5 mol·Pa−1·s−1·m−2 with superficial gas velocity increasing from 0.6 to 1.4 L·min−1. With the temperature of sodium persulfate solution increasing from 293 to 333 K, the specific interfacial area decreased 42.66 m−1, while the liquid phase mass transfer coefficient and the gas phase mass transfer coefficient increased 3.89 × 10−4 m·s−1 and 1.18 × 10−5 mol·Pa−1·s−1·m−2, respectively. The experiments results determined the correlations of and with the temperature of the absorption phase and the superficial velocity of the gas. It can serve as a guide to the enhancement of the sodium persulfate wet denitrification process.

Carbon dioxide capture by the green aqueous sodium hydroxide-glycerol solution in a gas-liquid microchannel contactor

Although organic solutions of alkali metal hydroxides have been considered a well-established technology for CO2 capture, they impose energy loss and a high corrosion rate due to the lack of suitable inhibitors. In this context, glycerol, as an abundant waste by-product of the biodiesel industry, was proposed to explore the CO2 absorption potential in the aqueous solution of sodium hydroxide-glycerol in a T-shaped microchannel contactor with an internal diameter of (ID=800 µm). Applying Response Surface Methodology (RSM), the CO2 absorption experiments were performed under temperatures of 25–45℃, with NaOH+Gly concentrations ranging from (0.2–0.8 M)+ (4–12 wt%), and the inlet gas flow rate of 100–300 ml/min. NaOH concentration was identified as a significant decisive variable on the CO2 absorption efficiency (η) and the overall gas-phase mass transfer coefficient (KGaV). The CO2 absorption efficiency of the developed hybrid solution was reported in the range of 29.28–98.40%. Besides, at concentrated alkali solution, adding glycerol from 4 to 12 wt% will raise the value of KGaV by more than 5.2 folds. This implies that the presence of glycerol in the aqueous NaOH solution not only intensifies the mass transfer performance but also declines the prevailing pollution and hazard wastes.

Simultaneous absorption of SO2 and NO from flue gas by ammonia solution with a wetted-wall column

In a self-designed wetted column, the effects of absorption concentration, initial pH, liquid-gas ratio, SO2 inlet concentration, NO inlet concentration on desulfurization and denitration efficiency were studied with ammonia solution. The results show that the removal efficiency of SO2 and NO can be improved by increasing the concentration of absorption liquid and liquid-gas ratio. The presence of SO2 can promote the removal of NO. Increasing SO2 concentration and NO concentration are not conducive to removing SO2. The liquid-phase and gas-phase mass transfer coefficients of SO2 in the system were determined. The results demonstrate that when inlet concentration of SO2 and NO is about 1100 mg/m3 and 500 mg/m3 respectively, the best technical parameters are 4 to 5 L/m3 for the liquid-gas ratio, 6.0 to 7.0 for the pH of absorption, 3%(wt) for Ammonia concentration. Under the best experimental conditions, the removal efficiency of SO2 can reach above 99%, and that of NO can reach above 50%.

Process Modeling of CO2 Absorption with Monoethanolamine Aqueous Solutions Using Rotating Packed Beds

A first-principle process simulation model is presented for the chemical absorption of carbon dioxide (CO2) with monoethanolamine (MEA) aqueous solutions using rotating packed beds (RPB). Built on a proven rate-based packed bed absorber model, the RPB model rigorously simulates the phase and chemical equilibria at the vapor–liquid interface, the heat and mass transfer across the gas and liquid films, the fast reactions between MEA and CO2 in the liquid film, and the RPB hydraulics. Estimation of the rate of transfer of mass across the liquid film is central to accurate simulation of the CO2 absorption process with MEA aqueous solutions. We show that the literature lab-scale RPB data for CO2 removal efficiency can be satisfactorily correlated by introducing a correction factor for the effective packing surface area predicted by the Onda correlation. Given the validated RPB model, we further show that, among the gas-phase mass transfer coefficient, the liquid-phase mass transfer coefficient, and the reaction rate constant for the reaction between amine and CO2, the reaction rate constant is the controlling step with the greatest potential to enhance the CO2 absorption performance in RPB.

Process intensification of SO2/CO2 co-capture using microscale vortex flow contactor: Mass transfer behaviors, performance modeling, and flow simulation

To achieve the simultaneous desulfurization and decarbonization by a simple, compact, and low-energy-consumption way, a microscale vortex flow contactor was developed to determine the mass transfer performances of SO2/CO2 co-capture with NaOH solution. Their mass transfer behavior in varying operating parameters was examined in terms of the overall gas-phase mass transfer coefficient (Kga). It was found that the Kga ranges from 3.04 × 10−3 − 1.46 × 10−2 kmol/m3·s·kPa for SO2 capture and from 8.80 × 10−4 − 3.81 × 10−3 kmol/m3·s·kPa for CO2 capture, respectively. The Kga was mainly affected by the absorbent concentration, CO2 concentrations, and liquid–gas flow rates. Furthermore, a semi-empirical correlation was proposed to model their mass transfer performances. It showed the agreement between the measurement and prediction with R2 = 0.9851 for SO2 capture and R2 = 0.9904 for CO2 capture. Finally, the gas flow pattern inside the contactor was simulated using the computational fluid dynamics approach to address the role of gas vortex flow in mass transfer enhancement.

Joint Method for the Experimental and Computational Characterization of Ammonia Absorption Columns

AbstractWell‐designed absorption columns are indispensable to industry. A prototypical system is the absorption of gaseous NH3. This experiment employed the method of transfer units where collection of vapor (V) and liquid (L) flow rates and concentrations enabled the characterization of the number of transfer units (NTU), height of transfer unit (HTU), and overall gas phase mass transfer coefficient (Ky). A nonmonotonic relationship between V, L, NTU, and HTU values was found; Ky showed a monotonic relationship with V and L. Computer‐simulated, correlation‐based, and experimental NTU, HTU, and Ky values demonstrated close numerical similarities. This experiment highlighted the importance of a combined empirical, theoretical, and simulation approach in achieving more reliable results from absorption column analysis.

The effect of alkanolamine mixtures on CO2 absorption efficiency in T-Shaped microchannel

In this investigation, removal of CO2was carried out using aqueous mixtures of MEA + DEA and MEA + TEA in a T-shaped microchannel. For this purpose, the effect of parameters temperature, amine concentration in the solvent, the volume percent of amines in the solvent, the gas flow rate, and the liquid flow rate was investigated by the central composite design method. The results of experiments indicated that increasing the operating temperature did not have a significant effect on CO2 removal efficiency in both mixtures. However, the CO2 removal efficiency increases with increasing amine concentration, the volume percent of the amine in the solvent, and the liquid flow rate, but the CO2 removal efficiency decreases significantly as the gas flow rate increases. Under optimal conditions, the maximum removal coefficient of CO2 obtained by MEA +DEA and MEA+TEA aqueous mixtures is 97.9% and 91.9%, respectively. Besides, the maximum volumetric overall gas-phase mass transfer coefficient under operation condition of the experiment was obtained to be 110 and 67.5 (kmol/ m3 h kpa), respectively It indicates that compared to other mass transfer devices, using microchannel in the CO2 absorption process significantly increases the volumetric overall gas-phase mass transfer coefficient and provides a new approach to obtained high absorption percentage.

Intensification of HCl removal from flue gas using a rotor-stator reactor

The emission of HCl in flue gas causes serious environmental problems and its removal methods have attracted wide attention. This work investigated the intensification of HCl removal from flue gas in a rotor–stator reactor. The effects of high gravity factor, gas flow rate, water flow rate, temperature and inlet concentration of HCl on the removal efficiency of HCl, overall volumetric gas-phase mass-transfer coefficient (KGa) and height of a transfer unit in the removal of HCl by water in the rotor–stator reactor were investigated. Comparisons with conventional column indicated that the rotor–stator reactor had better mass-transfer performance and may have economic advantages in HCl removal. Comparison experiments showed that KGa and height of a transfer unit in the rotor–stator reactor were 10.9–45.2% higher and 41.5–55.7% lower, respectively, than those in a rotating packed bed, indicating that rotor–stator reactor has a superior capability for the removal of HCl in flue gas and other processes controlled by gas-side mass transfer. An artificial neural network model was established to predict the KGa of HCl removal from flue gas by water in the rotor–stator reactor. This work demonstrates that rotor–stator reactor is an effective process intensification technology for the removal of HCl from flue gas.

The contribution of l-Arginine to the mass transfer performance of CO2 absorption by an aqueous solution of methyl diethanolamine in a microreactor

The current study investigates the effect of adding l-arginine as a potential promoter for the conventional methyl diethanolamine (MDEA) in the carbon dioxide (CO2) capture process in a T-junction microreactor. The overall gas-phase mass transfer coefficient (KGaV) and CO2 absorption efficiency (ef) were evaluated under distinct operating conditions, including total amine + amino acid concentration of 50 wt%, the liquid flow rate of 3–9 mL min−1, and gas flow rate of 120–300 mL min−1. The composition of different concentrations in the mixture were as MDEA (50%), MDEA + ARG (46 + 4%), MDEA + ARG (42 + 8%),MDEA + ARG (38 + 12%). The impact of amino acid concentration on the physical properties of the aqueous MDEA solution was also compared in four solutions. The results indicated that increasing the arginine concentration from 4 wt% to 12 wt% intensifies the ef values from 78.91 to 92.7%, while the solution density and viscosity grows slightly. Furthermore, the values of the KGaV in the CO2 absorption enhanced from 14.34 kmol/(m3 kPa h) in aqueous MDEA (50%) solution to 63 kmol/(m3 kPa h) in MDEA + ARG (38 + 12%). It confirmed that arginine could apply as a potential chemical activator in the mixture of MDEA-ARG to intensify the absorption of CO2 in the post-combustion CO2 capture processes.

Effect of smelting temperature and CO2 gas flow rate on decarburization kinetics between CO2 gas and liquid Fe-C alloy

ABSTRACT The effect of smelting temperature and CO2 flow rate to decarburization kinetics between CO2 and liquid Fe-C alloy were investigated. The decarburization rate caused by CO2 increases with smelting temperature. Compared with low carbon condition (near 0.45 wt pct), the effect of temperature on decarburization rate is more significant under high carbon condition (near 3.5 wt pct). At high carbon content, the decarburization rate increases linearly with CO2 flow rate. And a CO2 decarburization kinetics model considering the influence of bubble diameter, bubble generation frequency, rising velocity and rate controlling step was established. When CO2 transfer in gas phase boundary layer is rate controlling step, the calculated data are in good agreement with the experimental data. It was also found that the effect of CO2 flow rate on the decarburization rate was mainly affected by the reaction surface area, but less on gas phase mass transfer coefficient in current experimental situations.

Enhancing carbon dioxide absorption performance using the hybrid solvent: Diethanolamine-methanol

In this study, to appraise the performance of hybrid Diethanolamine-methanol solvent for the CO2 absorption process in the packed bed, the volumetric overall gas phase mass transfer coefficient (KGaV) and the absorption percentage (η) under different operating conditions were investigated including inlet solvent temperature 25–65 °C, reboiler temperature 75–115 °C, the inlet CO2 concentration 5–15 vol%, solvent flow rate 0.50–1.50 lit/min, gas flow rate 50–100 lit/min and solvent concentration 10–30 wt%. The results show that by reducing the reboiler temperature from 115 to 95 °C, the mass transfer coefficient reduces 1%, but the reboiler temperature reduces 17% instead. This issue has a great effect on energy saving in the desorption section. Moreover, by adjusting the operating condition, the maximum KGaV and η were 4.69 (kmol m−3 h−1. kPa−1) and 99.9%, respectively. The results of this study indicate that the use of DEA-methanol solution had equal and even higher absorption percentage (up to 99.9%) than the conventional MEA aqueous solution in addition to the lower regeneration temperature.

Mass transfer coefficient for PZ + CO2 + H2O system in a packed column

The gas-phase mass transfer coefficient is one of the significant parameter for the determination of mass transfer in absorption columns. A novel correlation was obtained for the calculation of the gas phase mass transfer coefficient in the current research study based on the theoretical investigation and experimental data. Buckingham pi-theorem was utilized to develop an overall dimensionless correlation. The correlation was derived based on the experimental data conducted at the operating conditions’ range of temperature 40–100 °C, CO2 partial pressure of 18-66 kPa, and piperazine (PZ) concentration of 2-8 M. The correlation was validated using the experimental data with an acceptable error of 7.47%. The results showed that the gas-phase mass transfer coefficient was increased by enhancing the amount of holdup and Schmidt number (Sc) at different temperatures and PZ concentrations. Furthermore, by comparing the Sc number with holdup, it was observed that a higher temperature resulted in a higher hold-up amount in the gas-phase of the absorption column.

Mass transfer performance of carbon dioxide absorption in a packed column using monoethanoleamine-Glycerol as a hybrid solvent

Environmental concerns caused by chemical solvents need be managed through the advantages of hybrid bio-sourced solvents for CO2 capture. On the other side, to accurately predict the height of a CO2 absorption packed column, it is essential to estimate the mass transfer coefficients. This paper provides the experimental results of mass transfer performance of the aqueous mixture of MEA + Glycerol, as an industrially eco-friendly hybrid solvent, instead of a typical commercial alkanolamine solvent for CO2 capture in a laboratory-scale absorption packed column. For the first time, a predictive statistical model was built to investigate the influence of process variables, involving absorption temperature (30−45 °C), inlet gas flow rate (4−6 L/min), the initial solvent concentration of glycerol (5−15 wt %), and MEA (10−30 wt %) on the CO2 removal efficiency (ef), and the volumetric overall gas-phase mass transfer coefficient (KGaV) in the CO2+MEA + Glycerol system. The results of CO2-absorption showed that rising the glycerol concentration from 5 % to 15 % enhances the values of ef and KGaV by 4.5 % and 24.62 %, respectively, when the other three variables are considered fixed at their midpoints. Therefore, the presence of glycerol, as the promoter in a hybrid mixture of MEA-Gly, significantly gives rise to the mass transfer coefficient and CO2 removal efficiency.

Mass transfer performance and correlation for CO2 absorption into aqueous 3-diethylaminopropylamine solution in a hollow fiber membrane contactor

3-Diethylaminopropylamine (DEAPA), a diamine with high reaction rate and large absorption capacity, was investigated in this work to evaluate its CO2 absorption mass transfer performance in a hollow fiber membrane contactor in terms of the CO2 absorption flux (JCO2). A series of experiments were conducted at various operation conditions and the effects of several influential parameters on JCO2 were examined and discussed in detail, including the liquid flow rate, the inlet gas flow rate, amine concentration, feed liquid temperature, CO2 partial pressure, lean CO2 loading, and membrane contactor height. Experimental results indicated that lean CO2 loading and membrane contactor height have negative effect on the total mass transfer performance since the value of JCO2 decreases with the increase of these two factors, while the other five parameters exhibit positive effect and their increase lead to the increase of JCO2 values. In addition, a numerical correlation was established to predict the overall gas phase mass transfer coefficient and the CO2 absorption flux, and the average absolute deviation (AAD) is 6.84%.

Wet flue gas desulfurization using micro vortex flow scrubber: Characteristics, modeling and simulation

It has been a great concern that the process intensification and the system complexity for wet flue gas desulfurization (wet-FGD) with chemical absorption. To enhance the mass transfer performance of the De-SO2 process under the simple conditions, a micro-vortex-flow based scrubber was designed to investigate the characteristics of the wet-FGD with K2CO3 solution. The effects of the key operating parameters on De-SO2 performances were comprehensively examined, including absorbent concentration, inlet SO2 concentration, and liquid–gas flow rate. It was found that the De-SO2 efficiency increased generally with the increasing K2CO3 concentration, inlet SO2 concentration, and liquid flow rate but decreased with increasing gas flow rate. However, the overall gas-phase mass transfer coefficient increased as these parameters increase. Within the measured range, the overall gas-phase mass transfer coefficient varied from 2.88 × 10−3 to 1.13 × 10−2 kmol/m3·kPa·s, and the De-SO2 efficiency was observed in the range of 75.1% to 91.8%. On this basis, a semi-empirical correlation for predicting the vortex-flow-based De-SO2 mass transfer performance was developed with R2 = 0.958. Finally, the computational fluid dynamics (CFD) simulation was employed to explore the relationship between the vortex flow and the principle of process intensification. The results may provide a positive reference for the industrial application of De-SO2 with the micro vortex flow scrubbing.

Enhanced performance on simultaneous removal of NOx-SO2-CO2 using a high-gravity rotating packed bed and alkaline wastes towards green process intensification

In order to intensify the gas-liquid absorption processes in the field of energy and environment, high-gravity rotating packed bed (HiGee RPB) has been successfully applied in the multiple air pollutants abatement and CO2 capture by mineralization. Since the mass transfer and chemical reaction through gas-liquid absorption were found to be the key factors affecting acid gas removal, a mass transfer model based on the two-film theory for simultaneous removal of NOx-SO2-CO2 in an RPB was developed in this study. The mass transfer parameters including overall gas-phase mass transfer coefficient (KGa), height of a transfer unit (HTU), liquid mass transfer rate (kL) and enhancement factor (E) were theoretically determined from the experimental data. The effect of key dimensionless operating factors such as high gravity factor (β), gas-to-liquid ratio (GLR), and liquid-to-solid ratio (LSR) on mass transfer parameters were evaluated. Based on the results obtained in this study, the enhancement of high gravity filed on mass transfer and removal efficiencies of NOx and CO2 were significantly higher than that of SO2. It was inferred that the carbonation reaction could compensate the removal efficiency of acid gaseous pollutants at the lower mass transfer rate. The relationship between mass transfer rate and energy consumption for the multiple air pollutant control via a HiGee process was established. The favorable operating factors for NOx-SO2-CO2 simultaneous removal in an RPB were suggested as β of 233.8, GLR of 69.5 and LSR of 40.