Wetted Wall Column Research Articles

Phase separation behavior and CO2 absorption kinetic analysis of DETA/DEA/DMAC biphasic absorbent

Lower regeneration energy and superior cyclic capacity have enabled biphasic absorbents great potential in the area of flue gas CO2capture. The liquid film mass transfer coefficient(kL) is a vital parameter in the development of absorbents with efficient CO2 absorption mass transfer performance, while the phase separation behavior of biphasic solutions could be an essential factor for the absorption mass transfer and the stability of absorber. However, systemic kinetic research towards biphasic absorbents, especially the impact of phase separation behavior, is limited. In this study, a typical amide-based biphasic absorbent diethylenetriamine(DETA)/diethanolamine(DEA)/N, N-dimethylacetamide(DMAC) which has achieved great reduction in regeneration energy, was selected as the subject of kinetic investigation in a wetted wall column. The CO2 overall mass transfer coefficient(KG) of DETA/DEA/DMAC exceeded other biphasic solvents, blended amine solution, and 40% K2CO3 solution, with 3 times that of 40% K2CO3 solution. Moreover, various operational conditions including absorption temperature, gas flow rate, and water content of solution were taken into account to build a multiple-condition kinetic mechanism to offer guidance for biphasic absorbents. Furthermore, phase separation behavior was revealed as the main blame for the deterioration in the liquid film chemical mass transfer process of biphasic solvents in the CO2 absorption process, resulting in the kL of DETA/DEA/DMAC before phase separation decreased by 75.3% at the phase separation stage. Therefore, it is crucial to ensure that the CO2 loading of the solution entering absorber is lower than the phase separation point in applications. After phase separation, DETA/DEA/DMAC split into the organic and aqueous phases, the kL of the aqueous phase gradually exceeded that of the organic phase as CO2 loading increased for its higher chemical enhancement factor(E).

CO2 absorption mechanism and kinetic modeling of mixed amines with ionic liquid activation

AbstractIonic liquid (IL) can not only serve as solvents to reduce carbon capture energy consumption, but also may activate the CO2 absorption of amine solutions. Here, the absorption mechanism and kinetic modeling of IL‐activated single and mixed amines were studied in wetted wall column. N‐(2‐aminoethyl) ethanolamine (AEEA) and N,N‐diethylethanolamine (DEEA) were used as representatives to evaluate the IL activation effects on primary and tertiary amines. It was found that IL activated the reaction process of primary amine, but had no activation effect on tertiary amine. The activation energy of AEEA‐IL‐CO2 was 22.2 kJ/mol, which was 21.0% lower than AEEA‐CO2. Kinetic modeling of IL‐activated AEEA and mixed amines was established. Besides, the density functional theory calculations showed that IL can form hydrogen bonding and other interactions with AEEA and CO2 to activate the absorption reaction, which can reduce 29.3% activation energy during the zwitterion formation stage.

Mass transfer and kinetic measurement and modeling for CO2 absorption into aqueous EAE and water-lean EAE/NMP solvents

Chemical absorption using amine solvent is currently available technology for CO2 capture from post-combustion flue gas. It is hindered by high operating cost and high capital cost due to high regeneration energy and slow CO2 absorption rate of amine solvent. Water-lean solvent of 2-(ethylamino) ethanol (EAE)/1-methyl-2-pyrrolidinone (NMP)/water could be a potential solution as it achieved significantly low regeneration energy of 2.3 GJ/tCO2 tested in a pilot plant. However, kinetics of CO2 reaction with EAE and mass transfer rate of CO2 absorption into EAE/NMP solvent are not fully understood. In this work, kinetics of CO2 absorption into unloaded aqueous EAE in 1–5 mol/L at 300–313 K and mass transfer of CO2 absorption into CO2-loaded EAE/NMP water-lean solvent in 5 mol/L with equilibrium CO2 partial pressure (PCO2*) range of 0.3–7 kPa at 312 K were studied in a wetted wall column. Kinetic data of aqueous EAE is interpreted by zwitterion mechanism, and the reaction is of first order with respect to EAE concentration in 1–5 mol/L at 300–313 K. CO2 absorption rate (kg’) of EAE/NMP water-lean solvent is 1.3–2.1 times greater than aqueous EAE due to the greater CO2 physical solubility. At lean and rich loading conditions, 5 M EAE in 3NMP/1water and 9NMP/1water show 2–7 times faster kg’ than 30 % MEA, and 1.4–2.5 times faster kg’ than 30 % PZ. It is found that EAE activity coefficient may increase in the presence of NMP in the solvent, and the estimated EAE activity coefficient in 1NMP/1water, 3NMP/1water, and 9NMP/1water are 2.13, 3.50, and 4.72, respectively. CO2 capacity of EAE/NMP solvent is 2–3.7 times greater than 30 % MEA and 1.2–2 times greater than 30 % PZ.

Experimental study for the effect of changing flow on absorption in wetted wall column

Gas absorption is the unit operation in which one or more soluble components of gas mixture are dissolved in a liquid. The absorption may be a purely physical phenomenon or may involve chemical reaction with one or more constituents in the liquid solution. In order to obtain the highest rate of absorption, gas and liquid streams flow in opposite directions in counter-current flow. The unit in this work has been designed to help grasp the basic principles of the chemical and physical aspects involved in absorption. This study unit is made of borosilicate transparent glass in order to show the water spread in the column and get the visual distribution of fluids behavior which helps to fully understand the phenomenon. In this work, the wetted wall column is used to determine gas/liquid mass transfer coefficients, which is essential to design absorption towers. This study investigates the absorption of oxygen from air into deoxygenated water (prepared by nitrogen sparing) in liquid film controlled absorption experiment. The liquid film mass transfer coefficients calculated at various mass flow rates of water and air. This work also studies the effect of water flow(expressed by Sherwood number) and air flow (expressed by Reynolds number)on oxygen concentration in the oxygenation and de-oxygenation process so affect on absorption process. From results, found that relation between Reynolds and Sherwood in wetted wall column been proportional this mean when we increase flow rate of water from 4 to 12 L/hr or air from 60 to 180 L/hr in wetted wall; concentration of oxygen in water out increase which mean absorption is better. Also, the final equation shows linear relation between Reynolds and Sherwood in wetted wall column. All these result help in understanding absorption process and factors influence in efficiency of towers used in real plant and helpful in design absorption tower.

Evaluation of potassium glycinate as a green solvent for direct air capture and modelling its performance in hollow fiber membrane contactors

Current direct air capture (DAC) technology is largely cost-prohibitive for large scale implementation due to the excessive energy required to operate a combined absorption–desorption cycle. As the desorption process consumes much of the supplied energy, there is a demand to find more sustainable sorbent materials that maintain high absorptive capacities yet can be regenerated at lower working temperatures. This work evaluates potassium glycinate (GlyK) as one such alternative absorbent. Through conducting vapor–liquid equilibria and wetted wall column kinetic studies, GlyK is found to have comparable working capacities and liquid mass transfer coefficients to those reported for the industrial standard, monoethanolamine (MEA), yet outperforms it with regards to its distinctly low regeneration temperature. To further understand how GlyK would perform in an industrial scale DAC system, an Aspen Custom Modeler® (ACM) model is developed that integrates the experimentally obtained equilibria and kinetic data with the performance characteristics of a gas-solvent hollow fiber membrane contactor (HFMC). Full-scale simulations show that via implementing a 20°–90 °C absorption–desorption cycle, GlyK can capture up to 83 % of the CO2 in atmospheric air and be 55 % regenerated within a single membrane contactor pass. As these low working temperatures vastly outperform the conventional ∼ 40°–140 °C temperature swing currently implemented in industrial CO2 processing, GlyK is concluded to be a viable and sustainable option for use within energy-efficient DAC technology whereby renewable heat sources can be used.

Mass transfer and reaction mechanism of CO2 capture into a novel amino acid ionic liquid phase-change absorbent

In order to overcome high heat duty and poor regeneration efficiency of existing chemical absorbent, a novel aqueous amino acid ionic liquids (AAILs) phase change absorbent with tetraethylenepentamine (TEPA) as cation, L-proline (L-Pro) as anion and N-propanol (NPA) as phase separator was proposed in this study. [TEPAH][Pro]/NPA/H2O owned the maximum absorption loading of 2.01 mol CO2·mol absorbent−1, and the rich phase viscosity was only 8.06 mPa·s. Moreover, its desorption efficiency was 84.4% while the 5th cyclic loading kept above 1.61 mol CO2·mol absorbent−1. With the presence of NPA, the rich phase only accounted for 41% of the total volume while it contained 99.3% of CO2 products. The heat duty was only 2.39 GJ·t CO2-1, which was 37% lower than that of 30 wt% ethanolamine (MEA) aqueous solution. Meanwhile, the reaction mechanism and product distribution were revealed by 13C NMR and the mass transfer kinetics was investigated using the wetted wall column. The products in the rich phase mainly consisted of carbamate, hydrogen carbonate, propyl carbonate and water while the main component of the lean phase was NPA. The reaction followed a fast pseudo-first order reaction. At 313.15 K, the rate constant of fresh absorbent was 51346 s−1, which showed a decreasing trend with the increase of absorption loading at 313.15 K. The second order reaction rate was calculated by: k2 = 9.88 × 109exp(-3591.2/T), where the reaction activation energy was only 29.86 kJ·mol−1.

Preventing crystallization at high concentrated 2-amino-2-methyl-1-propanol for energy-saving CO2 capture

2-amino-2-methyl-1-propanol (AMP) combines the advantages of the faster reaction rate of primary/secondary amines and the high absorption capacity of tertiary amines, making it a highly promising alternative to monoethanolamine (MEA). However, at high AMP concentrations, the absorption products are prone to solid crystallization, resulting in unstable operation of the carbon capture system. In this work, by adding a small amount of diethylenetriamine (DETA) to AMP, the crystallization of reaction products can be effectively controlled and AMP-DETA absorbent possesses a high absorption rate, low regeneration energy, and low metal corrosion rate. Wetted-wall column tests were performed to comprehensively evaluate the mass transfer kinetics and the effect of crucial conditions, and the diffusion coefficient, gas–liquid mass transfer coefficient, enhancement factor, and mass transfer resistance distribution were obtained. The effect of the addition of DETA on the solubility of HCO3− was verified. DETA carbamate was more likely to form intermolecular hydrogen bonds with HCO3−, thus reducing the formation of dimeric or multichain macromolecules between HCO3− molecules through hydrogen bonds and inhibiting the crystallization of high concentration HCO3−. HCO3− can accelerate the desorption rate by participating in the deprotonation of protonation amines. The results demonstrated that the average regeneration energy of the AMP–DETA absorption system was reduced by 21.2 % relative to that of 5 M MEA, and its metal corrosion rate was 0.07 mm/a, which was only 7.9 % of MEA under the same conditions. The results contribute to the industrial application of AMP–DETA.

Absorpsi CO2 Pada Wetted Wall Column dengan Variasi Laju Alir NaOH dan Konsentrasi Methyldiethanolamine

This research describes the biogas purification process by reducing CO2 content using NaOH solution as an absorbent and methyldiethanolamine (MDEA) as a promoter in Wetted Wall Column (WWC). The purpose of this study was to determine the effect of MDEA concentration and flow rate of NaOH + MDEA solution on CO2 absorption. The column is made of acrylic material with a diameter of 4.5 cm, height 50 cm, equipped with a tube with a diameter of 1.27 cm, height 45 cm. The tube is in the center of the column. The flow rate of absorbent solution for each run was varied as 150, 200, 250 and 300 ml/min and the concentration of MDEA for each run was 4% wt and 6% wt in 1 M NaOH. The biogas flow rate was 6 L/min, which was fed from the bottom of the column. The samples were analyzed by Gas Chromatography 2014 AT (SHIMADZU Corp 08128). The results showed that at 6% NaOH + MDEA solution, the solution flow rate of 150 mL/min was the best. Under these conditions, the output CO2 content is 13.306% and the output CH4 content is 81.737%. The results of the output CO2 content did not reach the 90% target because the biogas was contaminated by gas from the environment and the lack of control over the condition of the equipment during the absorption process.

Kinetics and Thermodynamics of CO2 Absorption in Aqueous 3-Dimethylaminopropylamine and Its Blend with Poly(ethylene glycol) Dimethyl Ether Using a Wetted Wall Column Reactor

Biphasic solvent 3-dimethylaminopropylamine (DMAPA)/poly(ethylene glycol) dimethyl ether (NHD)/H2O solution is a promising absorbent for CO2 capture. The kinetics of CO2 absorption in both DMAPA/NHD/H2O system and DMAPA/H2O systems was investigated and compared in a wetted wall column reactor with different CO2 loadings at different CO2 partial pressures from 30 to 70 °C. The equilibrium CO2 loadings were also determined. Meanwhile, the density and viscosity for both systems were measured. In both systems, the mass transfer flux of CO2 increases linearly with the increase of CO2 partial pressure. The kinetic data were interpreted by the zwitterion mechanism. The overall mass transfer constant was determined according to the absorption rate experiments performed in the pseudo-first-order regime. The overall mass transfer resistances increase with the increase of CO2 loading and decrease with the increase of temperature. The addition of NHD decreases the equilibrium CO2 loadings at the same CO2 partial pressure and temperature. However, it increases the enhancement factor significantly and can promote both the absorption and the desorption process. It provides basic information not only for the further utilization of DMAPA/NHD/H2O solution, which is helpful for the design of absorption reactor, but also for developing new phase-change absorbents for CO2 capture.

Mechanism of CO2 capture by ethanol-biochar functionalized cross-linking enhanced ammonia

CCUS technology is an important means to achieve carbon neutralization of energy utilization, in which the ammonia CO2-capture method is a relatively mature technology, with some problems (such as low CO2 absorption efficiency and serious ammonia escape). An ethanol/biochar synergistic ammonia carbon capture technology is proposed, and the mass transfer coefficient is studied by wetted-wall column, so as to assist in proving that biochar and ethanol have synergistic effect on the absorption of CO2 by ammonia. The simulation shows that the micropores in biochar adsorb and enrich CO2, the mesopores and macropores diffuse and transport CO2, and dynamically retain free NH3, thereby enhancing the mass transfer capacity of CO2 in the carbon capture system. And the experiment shows that the mass transfer efficiency of biochar-ethanol to the reaction solution is increased by 15.4%, which is higher than that of ethanol (7.1%),but biochar can make ammonia escape seriously. If the ammonia concentration can be maintained constant, the enhancement effect of the pore structure of biochar on the diffusion of CO2 into ammonia will provide a new direction for the improvement of CO2 capture by ammonia method.

Piperazine-activated diethanolamine formulation for post-combustion CO2 capture

Although activated alkanolamine based solvents had great potential for energy-efficient post-combustion CO2 capture, yet these suffers from disadvantageous due to high capital cost of the process. In this research we developed and discussed the overall reaction scheme between CO2 and activated solvents. We investigated the kinetics of CO2 into piperazine (PZ) activated aqueous diethanolamine (DEA) by wetted-wall column contactor at (298–323) K, (5–15) kPa and fixed 3.0 kmol∙m−3. Physicochemical properties of such systems were determined while detailed uncertainty analysis were conducted. In thermodynamics point of view, liquid–liquid interaction were explored and evaluated by related parameters. The kinetics rate parameters for such activated solvents were interpreted based on kinetic study affording to the pseudo-first-order reaction method. At various temperature, kov of (PZ + DEA + H2O) were considerably larger than reported (AMP + PZ + H2O) systems. The results of kinetics study demonstrated that rate of CO2 in solvents were enhanced substantially as compared to DEA due to the addition of low quantity (0–0.45 kmol∙m−3) PZ into solvents. Besides, physicochemical properties were measured in terms of different models with absolute average deviation (AAD) < 5 %. Ultimately, (PZ + DEA + H2O) may be considered as vital solvents in amine scrubbing due to lower energy requirement for CO2 capture compared to (PZ + MEA + H2O).

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%.

Experimental study and modified modeling on effect of SO2 on CO2 absorption using amine solution

Understanding the competitive mechanism in absorption process between SO2 and CO2 is essential for simultaneous absorption of SO2 and CO2. In this study, the effect of SO2 on CO2 absorption using amine solution was studied experimentally and theoretically. The CO2 absorption rates in MEA/MMEA/MDEA solutions were determined using wetted wall column. Results showed that the reduction of flue gas temperature was beneficial for CO2 absorption at the typical coal-fired flue gas CO2 concentration. On this basis, the effect of SO2 on CO2 absorption performance was studied. Firstly, the overall CO2 mass transfer coefficient decreased under exposure to SO2. Secondly, in the presence of SO2, pH variation of amine solution increased. In addition, the saturated CO2 capacity largely decreased when SO2 was continuously bubbled into the solution. Furthermore, the quantum chemical calculation showed that CO2 had little effect on the absorption performance of SO2 whereas SO2 greatly weakened the interaction between CO2 and amines. The overall CO2 mass transfer coefficient was modified considering the effect of SO2. The competitive absorption factor, χ, was introduced to modify the CO2 liquid phase diffusion coefficients. The average deviation of overall CO2 mass transfer coefficient narrowed to 1.76 % (0.5 mol/L MEA), 1.13 % (1.0 mol/L MEA), 1.88 % (1.0 mol/L MMEA) and 1.43 % (1.0 mol/L MDEA) respectively, which agreed well with the experimental results.

Experimental Study for The Effect of Changing Flow on Absorption in Wetted Wall Column.

Gas absorption is the unit operation in which one or more soluble components of gas mixture are dissolved in a liquid. The absorption may be a purely physical phenomenon or may involve chemical reaction with one or more constituents in the liquid solution. In order to obtain the highest rate of absorption, gas and liquid streams flow in opposite directions in counter-current flow. The unit in this work has been designed to help grasp the basic principles of the chemical and physical aspects involved in absorption. This study unit is made of borosilicate transparent glass in order to show the water spread in the column and get the visual distribution of fluids behavior which helps to fully understand the phenomenon. In this work, the wetted wall column is used to determine gas/liquid mass transfer coefficients, which is essential to design absorption towers. This study investigates the absorption of oxygen from air into deoxygenated water (prepared by nitrogen sparing) in liquid film controlled absorption experiment. The liquid film mass transfer coefficient is calculated at various mass flow rates of water and air. This work also studies the effect of water flow and air flow on oxygen concentration in the oxygenation and de-oxygenation process so affect on absorption process .

Experimental Study for The Effect of Changing Flow on Absorption in Wetted Wall Column.

Gas absorption is the unit operation in which one or more soluble components of gas mixture are dissolved in a liquid. The absorption may be a purely physical phenomenon or may involve chemical reaction with one or more constituents in the liquid solution. In order to obtain the highest rate of absorption, gas and liquid streams flow in opposite directions in counter-current flow. The unit in this work has been designed to help grasp the basic principles of the chemical and physical aspects involved in absorption. This study unit is made of borosilicate transparent glass in order to show the water spread in the column and get the visual distribution of fluids behavior which helps to fully understand the phenomenon. In this work, the wetted wall column is used to determine gas/liquid mass transfer coefficients, which is essential to design absorption towers. This study investigates the absorption of oxygen from air into deoxygenated water (prepared by nitrogen sparing) in liquid film controlled absorption experiment. The liquid film mass transfer coefficient is calculated at various mass flow rates of water and air. This work also studies the effect of water flow and air flow on oxygen concentration in the oxygenation and de-oxygenation process so affect on absorption process .

Absorption of Carbon Dioxide into Glycine Activated Methyldiethanolamine (MDEA) Comparing with Diethanolamine (DEA)

It is widely accepted that increasing carbon dioxide (CO2) emissions to our atmosphere is the major contributor to global climate change, which pollutes environment. The chemical absorption using tertiary alkanolamines solution is one of most important method, which have been proposed and studied for the removal of carbon dioxide because the MDEA solvent has low cost, low corrosive tendencies, high stability, low viscosity, low tendency to foam, and low flammability, however it has low reaction rate. Therefore, we added glycine promoter to conventional solvents to increase the rate of the reaction because glycine is a primary amine compound which is reactive. Moreover, glycine has resistance to high temperatures; so, it will not easy to degrade making it not suitable for application in industry. The main purpose of this study was to provide reaction kinetics data of CO2 absorption into glycine promoted methyldiethanolamine (MDEA) by using laboratory scale wetted wall column equipment at the atmospheric pressure by varying temperature from 303.15 to 328.15 and glycine concentration from 1% to 3%, while the carbon dioxide absorption rate was measured by titration of liquid effluent. Based on the result of this study, we observed that by increasing temperature and concentration of glycine, the absorption rate of carbon dioxide in MDEA solution was increase. In addition, the reaction rate constant will be affected by the temperature and the concentration of promoter. The correlation of reaction rate constant (k glycine) was: k glycine = 5.3409E+13exp(-3251.9/T) with the activation energy for glycine promoter is 27.0363kJ/kmol, indicating it a very influencing, compared to diethanolamine (DEA).

Mass transfer coefficients of carbon dioxide in aqueous blends of monoethanolamine and glycerol using wetted-wall column

There is an urgent need for CO2 capture development because of the global warming crisis. Recently CO2 absorption by the mixture of monoethanolamine (MEA) and glycerol, as an eco-friendly solvent, has been considered due to its promising performance and low technical and environmental impacts. However, more aspects of this process, especially mass transfer coefficients, need to be studied further. In this work, a bench-scale wetted-wall column was used to find the CO2 mass transfer coefficients in the aqueous blends of MEA (25 wt%) and glycerol (5–20 wt%). The experiments were performed nearly to the industrial conditions of flue gas at atmospheric pressure and three different temperatures (313, 323, and 333 K). The gas flow rate was maintained around 0.17 ± 0.01 stdL/s, and the CO2 partial pressure was in the range of 1–15 kPa. The findings revealed that increasing the glycerol to 10 wt% improves the overall mass transfer (KG), and adding more glycerol up to 20 wt% decreases the KG. The gas-side mass transfer resistance (1/kg) found to be negligible. Thus, the primary mass transfer resistance was in the liquid phase. It is also found that the solution with 10 wt% glycerol and 25 wt% MEA (10G25M) had the highest liquid-side mass transfer coefficient (kg′) among the other solutions. The 10G25M showed a comparable and even better absorption rate than solutions with a higher concentration of MEA studied in the literature. Compared with industrial-grade, the kg′ of the 10G25M was over two times higher than the 30 wt% MEA solution.

Thermodynamic and kinetic modeling of a novel polyamine-based solvent for energy-efficient CO2 capture with energy analysis

Polyamine-based solvents (PSs) are regarded to be emerging energy-efficient alternatives to conventional solvents for use in absorption-based CO2 capture. In this paper, we propose a novel polyamine, 3,3′-iminobis (N,N-dimethylpropylamine) (IBDMPA), based aqueous amine solution. The solvent was composed of 45 wt% IBDMPA and 48 wt% water, with a non-amine chemical making up the rest of the mixture. Thermodynamic modeling work of CO2 solubility was carried out using Aspen Plus® V10, and the Elec-NRTL model with the Redlick-Kwong equation was integrated with the equilibrium model. For CO2 solubility modeling, measurement data was obtained from the equilibrium cell and 1H/13C nuclear magnetic resonance and used to validate the CO2 solubility modeling. Kinetic modeling of the proposed PS was conducted using a tertiary amine reaction mechanism, and the measurement data for the overall mass transfer coefficient was obtained using a wetted wall column. PS has cyclic capacity of approximately 1.05 mol-CO2/mol-IBD and overall mass transfer coefficient of 2.51e-03 mol m−2 kPa−1 sec−1, which is much higher than that of conventional MEA 30 wt% solution (0.35 mol-CO2/mol-MEA and 1.05e-03 mol m−2 kPa−1 sec−1). As a result, the minimum energy required for reboiler was calculated to be 2.3 GJ t-CO2−1 at 1 bara of the desorber pressure. Such a low energy demand value supports the commercial feasibility of polyamine-based solvents for large-scale CO2 capture.

Design of a water wash column in the CO2 capture process using a polyamine-based water-lean solvent

Amine-based water-lean solvents (WLSs) have been studied as energy-saving alternatives to existing aqueous amine solvents for the capture of CO2. However, despite the low energy requirements of WLS-based processes, WLSs are susceptible to amine vaporization loss due to the high amine concentration. In addition, the water content of WLSs is apt to increase, which is caused by the low vaporization pressure of water from the solvent due to the low water content of the solvent. When this happens, it is expensive to return the water content of the solvent to its original state. To address these problems, in this study, we investigated the design of a water wash section for a CO2 capture process based on a WLS consisting of 60 mass% of 3,3′-iminobis (N,N-dimethylpropylamine) (IBDMPA), 10 mass% of water, and a non-amine chemical as the final content. The heat and mass balance around the water wash section was analyzed, including the IBDMPA/water transfer from gas phase to liquid (water) phase within the water wash bed. To achieve this, the mass transfer coefficients of the IBDMPA and water were measured in a modified wetted wall column system, and the binary and ternary vapor–liquid equilibria for the WLS were also measured and modeled. The computation using the ASPEN Plus® simulator showed that IBDMPA emissions of less than 1 ppm and water balance in the WLS could be successfully achieved through the appropriate design of the water wash section.

Experimental and numerical mass transfer study of carbon dioxide absorption using Al2O3/water nanofluid in wetted wall column

In this study, the CO2 absorption by Al2O3/water nanofluid was investigated in laboratory-scale wetted wall column. Effects of important operation parameters such as, nanoparticle volume fraction, fluid flow rate and temperature on the mass transfer coefficient have been studied under laminar conditions and steady state. According to the experimental results, the mass transfer coefficient of nanofluid is higher than base fluid water and the mass transfer coefficient increases with the increase of nanoparticle concentration, temperature, and fluid flow rate. The mass transfer coefficients Al2O3/water nanofluid were increased by 40.3% and 67.16% with addition of 0.0125 and 0.025 %v/v nanoparticle, respectively. Then, the mass transfer behavior of Al2O3/water nanofluid in an axi-symmetric two dimensional domains was simulated by applying computational fluid dynamics considering Brownian motion mass diffusion coefficient in nanofluid. The CFD results have a good agreement with experimental results. Also, results have shown that the dimensionless CO2 concentration in film layer clearly increases with an increase in nanoparticle volume fraction and the temperature; but when the fluid flow rate increases, the CO2 concentration decrease.