CO2 Absorption Performance Research Articles

Assessment of mass transfer intensification potential for a CO2 capture process using three-phase fluidized bed

In order to assess the post-combustion CO2 capture intensification potential, a detailed mathematical model was developed for a three-phase fluidized bed. As solvents, various aqueous solutions were used e.g. NaOH and MEA with and without glycerol addition. An innovative mass transfer equipment is presented, a three-phase gas-solid-liquid fluidized bed absorber, in which the bed of low-density inert solid particles is fluidized by the counter current flow of gas as a continuous phase and liquid as a dispersed phase. Experimental data from a pilot plant was used to validate the developed model. The hydrodynamic parameters determined were the followings: fluidized bed expansion ratio, liquid holdup and bed pressure. The most important efficiency parameter, the effective mass transfer area, was assessed. The results show that by using a three-phase fluidization column, the mass transfer parameters exhibit significant increases (8–10 times) in comparison to conventional packed beds. In addition, introducing glycerol to NaOH and MEA solutions was investigated as a potential method to further improve the overall CO2 absorption performance. As the results show, the glycerol addition intensifies the CO2 absorption process by about 10 %.

State-of-the-art of CO2 capture with amino acid salt solutions

Abstract The emission of large amounts of CO2 into the atmosphere is believed to be a major reason behind climate change, which has led to increased demand for CO2 capture. Postcombustion CO2 capture with chemical solvent is considered one of the most important technologies in order to reduce CO2 emission. Amino acid salt solutions have attracted special attention in recent years due to their excellent physicochemical properties, e.g., low volatility, less toxicity, and high oxidative stability, as well as capture performance comparable with conventional amines. In this study, physicochemical properties of 20 amino acids are reported and their CO2 absorption performance discussed. The topics covered in this review include the most relevant properties of amino acids including CO2 loading capacity, cyclic capacity, equilibrium constant, density, viscosity, dissociation constant, CO2 solubility, CO2 diffusivity, reaction kinetic between CO2 and amino acid salts, reaction rate constant, surface tension, heat of CO2 absorption, precipitation, toxicity, solvent degradation, and corrosion rate. This review provides the most recent information available in the literature on the potential of using amino acid salts as a solvent for CO2 capture which can help improve the performance of the CO2 capture process from flue gas streams.

Correlation of CO2 absorption performance and electrical properties in a tri-ethanolamine aqueous solution compared to mono- and di-ethanolamine systems.

The study investigates the correlation of CO2 absorption performance and electrical properties in a tri-ethanolamine (TEA) aqueous solution compared to the mono-ethanolamine (MEA) and di-ethanolamine (DEA) systems. While the absorption rate of the MEA and DEA systems varies with amine concentration, and the maximum rate is observed at 30.0 and 50.4 wt% amine solution, respectively, the rate of the TEA system according to concentration follows a parabolic curve and the maximum rate is observed at 15.0 wt% solution. The ionic conductivity of carbamic acid in the TEA system is estimated to be the smallest with 37.60 S cm2/mol z and the decreasing ratio of ionic activity coefficient according to the concentration is the largest. The results are mostly attributed to differences in amine molecular structure and the unique reaction mechanism. Finally, based on these values, the correlation equations are obtained to estimate CO2 absorption capacity by measuring electrical conductivity in situ.

Enhanced research of absorption by mass transfer promoters

Activators such as piperazine (PZ) are widely used to increase the CO2 absorption rate of aqueous methyldiethanolamine (MDEA) solutions by accelerating reaction. However, a big difference (1 to 2 orders of magnitude) in the enhancement of absorption rate with the addition of PZ was obtained in different studies. In this work, it was proved that mass transfer is the rate-limiting step in the above process and in most cases enhancing mass transfer is quite essential. Some low-polar solvents were screened as “mass transfer promoters (MTPs)” to enhance mass transfer by inducing interfacial turbulence, which markedly improved the CO2 absorption performance of MDEA solutions. The individual addition of PZ and MTPs to the MDEA solution, which correspond to the reaction enhancement and the mass transfer enhancement, increased the absorption rate by 131% and 33%–319%, respectively. The co-effects of enhancing both reaction and mass transfer (in the presence of activators and MTPs) can lead to 2 to 10-fold increase in the absorption rate. Furthermore, MTPs could increase the CO2 cyclic loading and desorption rate by 27% and 100%, respectively, indicating that the MDEA/MTPs had significant advantages for reducing the energy consumption in CO2 capture applications.

Heat of absorption of CO2 in aqueous solutions of DEEA and DEEA + MAPA blends—A new approach to measurement methodology

The heat of absorption is an important parameter that affects the CO2 absorption and stripping performance of amine-based CO2 capture. The present paper aims at development of the experimental method of determining the heat of absorption using a batch reaction calorimetry. A prospective high‐capacity CO2‐capturing solvent based on an aqueous solution of N,N-diethylethanolamine (DEEA) blended with small concentrations of 3-(methyloamino)propylamine (MAPA) is therefore studied. The differential and integral heat of absorption of CO2 was measured at 40 °C and 60 °C using single DEEA and amine blends. Experiments show that the heat of absorption in DEEA and DEEA + MAPA blends depends both on loading and temperature, though the temperature dependency is not as high as reported earlier. Increasing the MAPA/DEEA concentration ratio increased the heat of absorption in the amine blends.

Elucidating the performance of (N-(3-aminopropyl)-1, 3-propanediamine) activated (1- dimethylamino-2-propanol) as a novel amine formulation for post combustion carbon dioxide capture

The exploration of energy-efficient amine solvents for CO2 removal from fluegas streams has been adopted as a key strategy for the wide implementation of CO2 capture technology in fossil fuel-based power plants for post-combustion CO2 capture. The current study entails an insight into the CO2 absorption performance of a novel aqueous amine blend of N-(3-aminopropyl)-1,3-propanediamine (APDA) and 1-dimethylamino-2-propanol (1DMAP) with special emphasis to the investigation of CO2 solubility at equilibrium state. In order to investigate the effect of promoter addition, the concentration of APDA has been gradually increased from 0.02 w to 0.10 w in the mixed solvent blend. The generated solubility data are correlated using two different modeling approaches viz., equilibrium based modified form of Kent-Eisenberg (KE) thermodynamic model and feed-forward neural network model. The model prediction is further extended to estimate pH and the overall speciation profile of all the molecular as well as ionic species prevailing in the solvent system. The CO2 solubility data are also analyzed in view of estimating the heat duty requirement for the absorption process. The heat of absorption of CO2 in aqueous (APDA + 1DMAP) blend has been calculated using theGibbs-Helmholtz equation. Along with solubility measurement, important thermophysical properties such as density and viscosity of the aqueous amine solution are also measured and correlated using established Redlich-Kister and Grunberg Nissan models.

CO2 absorption into aqueous diethanolamine solution with nano heavy metal oxide particles using stirrer bubble column: Hydrodynamics and mass transfer

Abstract In this research, the TiO2, ZnO, and ZrO2 nanofluids based on the DEA solution were provided exploiting the ultrasonic dispersion system to investigate the impact of the nano-particles on the CO2 absorption in a continuously stirred bubble column. The nano-particle concentration was determined in the range 0.01−0.10 wt%,. Bubble size distribution along column axis measurements was carried out using the high-speed digital camera. The influences of several factors such as CO2 partial pressure, solid loading, nanoparticle type, and stirring speed on the hydrodynamic characteristics and CO2 absorption performance were examined in detail. The presence of nanoparticles increased the gas holdup and interfacial area up to optimum value and then had a negligible effect. The stirrer speed increased the gas holdup and interfacial area up to optimum value and then decreased. Furthermore, the results showed that the adding nanoparticles in the range of 0.01−0.1 wt% increased CO2 absorption efficiency between 25.2–43.8% and the optimum value of nanoparticles can be an effective key parameter at the absorption phenomena into a dilute amine solution. Also, it was determined that at optimum stirrer speed, the removal efficiency of ZnO, TiO2, and ZrO2 nanofluids was caused an increase of about 12.1 % 8.0 %, and 13.3 %, respectively.

Effect of partial pressure on CO2 absorption performance in piperazine promoted 2-diethylaminoethanol and 1-dimethylamino-2-propanol aqueous solutions

Piperazine (PZ) was used to enhance the absorption of CO2 in 2-diethylaminoethanol (DEAE) and 1-dimethylamino-2-propanol (DMA2P) aqueous solutions. The mole fraction of CO2 in N2-balanced gas mixtures ranged from 0.1 to 0.8. The mass fractions of amine and PZ ranged from 0.300 to 0.500 and from 0.050 to 0.075, respectively. The experiments were performed at 313.2 K. The absorption capacity and absorption rate under a series of conditions were illustrated, and the effect of CO2 partial pressure on the absorption performance was demonstrated. At a given CO2 partial pressure, the CO2 absorbed by the PZ promoted DEAE and DMA2P aqueous solutions increases with the mass fraction of the mixed aqueous solutions, and it increases with the CO2 partial pressure at a given mass fraction. The absorption capacity of the DMA2P-PZ aqueous solution is slightly higher than that of the DEAE-PZ aqueous solution. In addition, the absorption rate depends on the competitive effects of the mass fractions, solution viscosity and the partial pressure of CO2.

Mass Transfer Performance Study for CO2 Absorption into Non-Precipitated Potassium Carbonate Promoted with Glycine Using Packed Absorption Column

The removal of carbon dioxide (CO2) at offshore operation requires an absorption system with an environmentally friendly solvent that can operate at elevated pressure. Potassium carbonate promoted with glycine, PCGLY, is a green solvent that has potential for offshore applications. For high solvent concentrations at elevated pressure, the by-product of CO2 absorption consists of precipitates that increase operational difficulty. Therefore, this study was done to assess the CO2 absorption performance of non-precipitated PCGLY with concentration 15wt%PC+3wt%GLY, which is known to have comparable solubility performance with MDEA. A packed absorption column was used to identify the CO2 removal efficiency, mass transfer coefficient in liquid film, k l a e , and overall volumetric mass transfer coefficient, K G a v . A simplified rate-based model was used to determine k l a e and K G a v based on the experimental data with a maximum MAE value, 0.057. The results showed that liquid flow rates and liquid temperature gives significant effects on the k l a e and K G a v profile, whereas gas flow rate and operating pressure had little effect. The CO2 removal efficiency of PCGLY was found to be 77%, which was only 2% lower than 1.2 kmol/m3 MDEA. K G a v of PCGLY is comparable with MDEA. The absorption process using PCGLY shows potential in the CO2 sweetening process at offshore.

Efficient and Reversible Chemisorption of Carbon Dioxide with Dianionic-Functionalized Ionic Liquid-Based Solvents

Developing carbon dioxide (CO2) capture technologies has caused worldwide interest because of the baneful influence of CO2 on climate change as a main greenhouse gas. Ionic liquids (ILs) are considered as potential absorbents for CO2 capture because of their unique properties compared with current amine-based solvents. In this work, new dianionic-functionalized IL-based solvents, bi­(1,8-diazabicyclo[5.4.0]­undec-7-ene) dimethylhydantoin/ethylene glycol ([(DBUH)2]­[Dhyd]/EG), were designed and prepared for efficient and reversible chemisorption of CO2. Among the absorbents, [(DBUH)2]­[Dhyd]/EG with a mass ratio of 5:5 exhibited not only a high CO2 absorption capacity of 0.11 g CO2/g absorbent at 20 °C and 0.10 MPa but also good recyclability. Spectroscopic characterizations and simulation calculations confirmed that the superior CO2 capacity may be attributed to the simultaneous reaction of CO2 with both the [Dhyd]2– anion and deprotonated EG. The excellent CO2 absorption and regeneration performance imply that [(DBUH)2]­[Dhyd]/EG solvents may have great industrial application potentials.

Evaluation of CO2 absorption performance by molecular dynamic simulation for mixed secondary and tertiary amines

CO2 emission to the atmosphere is the most prominent cause of climate change and a major risk to environmental health. Although several techniques are very promising to reduce the CO2 emission from central emission points, the CO2 absorption by amines remains the most mature and reliable technology. Yet, there is more potential to improve absorption performance by choosing suitable solvents. Thus, the present research is intended to explore a better solvent combination for CO2 absorption by adopting the amine absorption process using molecular dynamic simulation. The study is designed to compare the intermolecular interactions of NC and NH bond between single 2EAE, DMAE (or 2DMAE), and blended solvent, i.e., 2EAE/PZ, 2DMAE/PZ with carbon dioxide and water and then to catch the effect of piperazine on these amines. The molecular dynamic simulations were performed by using the Material Studio application. The solvent concentration, 30 wt% under the condition of 313 K temperature at 0.1 MPa pressure, was taken for solvent systems. The results were interpreted by the Radial Distribution Function analysis. It was found that the blend of secondary and tertiary amines with piperazine 2EAE/PZ, DMAE/PZ reflect higher intermolecular interaction with CO2 as compared to single DMAE & 2EAE. This finding shows that piperazine acts as a promoter on 2EAE and 2DMAE when interacting with CO2.

CO2 solubility in some amino acid-based ionic liquids: Measurement, correlation and DFT studies

The solubility of carbon dioxide (CO2) gas in three amino acid–based ionic liquids (AAILs), 1–butyl–3–methylimidazolium glycinate ([BMIm][Gly]), 1–butyl–3–methylimidazolium alaninate ([BMIm][Ala]), and 1–butyl–3–methylimidazolium valinate ([BMIm][Val]) has been experimentally investigated by quartz crystal microbalance (QCM). Solubility of CO2 has been evaluated at temperatures from 288.15 to 318.15 K and pressures up to 4 bars. According to the sorption mechanism, CO2 solubility in AAILs was correlated by a reaction equilibrium thermodynamic model. The thermodynamic parameters including Henry's constant, reaction equilibrium constant, enthalpy of physical dissolution, and the chemical reaction were calculated and compared with assess the CO2 absorption performance in AAILs. The obtained results indicate that glycinate anion ([Gly]) has more CO2 sorption capacity compared to alaninate ([Ala]) and valinate ([Val]). The chemical sorption of CO2 via carbamate formation was confirmed using FT-IR spectroscopy. Furthermore, density functional theory (DFT) calculations have been performed to investigate the interactions between the amino acid anion–based ionic liquids and CO2.

Microwave Synthesis of MCM-41 and Its Application in CO2 Absorption by Nanofluids

Microwave synthesis method is a green chemical process with mild reaction conditions, fast reaction, and low energy consumption. In this work, an order mesoporous silica material MCM-41 was synthesized by microwave technology. Functionalized MCM-41 was prepared by wet impregnation with polyethyleneimine (PEI). XRD, SEM, TEM, DLS, N2 adsorption-desorption, FTIR, and TG were used to characterize the physicochemical properties of samples. Furthermore, CO2 absorption performance in water in the presence of uncalcined MCM-41 and PEI-MCM-41 nanoparticles was evaluated. In addition, the mechanisms of enhanced absorption were also elaborated. The experimental results indicated that the optimum conditions for preparation of MCM-41 were the microwave time of 15 min, microwave temperature of 100°C, and microwave power of 200 W. Under this condition, MCM-41 with narrow particle size distribution, average diameter of 50 nm, and SBET of 1210.3 m2g-1 was obtained. The enhancement effect of PEI-MCM-41 nanoparticles was more obvious than that of uncalcined MCM-41. PEI-MCM-41 as a promoter not only increased the CO2 diffusion rate but also enhanced the adsorption capacity due to the fact that it owns more active sites that may react with CO2. The CO2 absorption improvement of PEI-MCM-41 (0.1 wt%)/H2O was 25.35% higher than that of water.

Effects of bubble coalescence and breakup on CO2 absorption performance in nanoabsorbents

The complexity and dynamics of bubble coalescence and breakup have fascinated scientists for decades. In this study, we performed experiments and simulations involving successively rising bubbles in a rectangular bubble column for carbon dioxide absorption in nanoabsorbents (methanol with various concentrations of alumina nanoparticles). The variations of the bubble behavior were captured by a high-speed camera in experiments and simultaneously visualized via simulations. Firstly, we distinguished the orifice region and the bulk liquid region. The bubble diameter was determined by only the gas flow rate and orifice diameter in the orifice region; however, it changed significantly in the bulk liquid region, experiencing approximately four stages. Wake entrainment and eddy capture dominated the bubble coalescence in the bulk liquid region; however, the bubble breakup was mainly caused by eddy collision and the coalescence of two bubbles with a small surface tension force. Both coalescence and breakup were more likely to occur in liquids with a higher concentration of nanoparticles. Additionally, we considered the mass transfer coefficient in the liquid phase and found that it can be enhanced by the coalescence and breakup, through the generation of polydisperse bubble swarms. A correlated parameter was deduced that can be substituted in the Hughmark equation to predict the mass transfer coefficient of the CO2–methanol–nanoparticle system.

Research progress of CaO-based absorbents prepared from different calcium sources

CaO-based absorbent have been regarded as an ideal high-temperature CO2 absorbent. However, as the number of cycles increases, the CO2 absorption performance gradually decreases. In order to maintain high CO2 removal efficiency, a large amount of fresh absorbent is required, resulting in a significant increase in economic costs and equipment load. Therefore, it is urgent to reduce the raw material cost of the CaO-based absorbent and maintain a high cycle absorption efficiency and stability by modification. Firstly, the decarburization principles of CaO-based absorbent and the reasons for absorption performance degradation were analyzed. Then, the main modification methods and thee respective effects of CaO-based absorbents prepared using different calcium sources (natural minerals, chemical agents, bulk industrial solid waste) were summarized, from the aspects of enhancing absorption efficiency, improving cycling stability and reducing costs. The results show that the CaO-based absorbent prepared by industrial solid waste with high calcium content has good CO2 absorption efficiency and cycle stability. A small amount of impurities in the solid waste may help to improve the corrosion resistance and wear resistance of CaO-based absorbent. In addition, the production cost of CaO-based absorbents can be minimized through the integration with industrial production.

Effect of different nitrogen ratio on the performance of CO2 absorption and microalgae conversion (CAMC) hybrid system

CO2 absorption hybrid with microalgae conversion (CAMC) could be a promising alternative for the conventional CO2 capture technologies. The hybrid process could avoid the challenges of thermal energy consumption in the conventional desorption process and nutrition consumption in the typical algae cultivation process. In this work, the influence of different nitrogen ratio (NH4HCO3:NaNO3) on the performance of the proposed hybrid CAMC process was investigated. Experimental results indicated that adding NH4HCO3 into cultivation solution could promote Spirulina platensis growth. When the ratio of NH4HCO3 and NaNO3 was set at 1:4, carbon utilization efficiency of the hybrid process could achieve 40.45%, which was higher than the conventional microalgae CO2 fixation processes (around 10%–30%). In addition, carbon sequestration capacity increased to 178.46 mg/L/d. It could be observed that CO2 absorption-microalgae conversion (CAMC) hybrid system has the potential for cost-effective CO2 capture and utilization.

Mechanism study on CO2 capture by [TETAH][HCOO]-PEG200 mixed system

CO2 is a greenhouse gas that contributes a lot to the global warming. Ionic liquid is a kind of green solvent that shows great potential in CO2 capture. The functionalized ionic liquid [TETAH][HCOO] was synthesized in this study, and CO2 absorption performance by the mixture system made up from [TETAH][HCOO] and polyethylene glycol 200 (PEG200) was investigated. Results showed that there was a significant synergistic effect between [TETAH][HCOO] and PEG200 on CO2 capture. PEG200 not only helped to increase CO2 absorption capacity, but also shortened the absorbing time. When the mass concentration of ionic liquid was 20 % and the temperature was 25 °C, CO2 absorption capacity in [TETAH][HCOO]-PEG200 system reached 1.340 mol CO2/mol IL, and its absorption rate was up to 12.768 mmol CO2/(mol IL•min). CO2 absorption in [TETAH][HCOO]-PEG200 system was mainly concentrated in the first 30 min, and CO2 absorption capacity accounted for about 80 % of the total during this period. The effects of temperature and PEG200 concentration on viscosity of [TETAH][HCOO]-PEG200 were investigated, which indicated that the effect of temperature on viscosity was greater than that of PEG200. Regeneration performance of [TETAH][HCOO]-PEG200 showed that the fifth CO2 absorption still retained 70.10 % of the original performance.

The CO2 Absorption in Flue Gas Using Mixed Ionic Liquids.

Because of the appealing properties, ionic liquids (ILs) are believed to be promising alternatives for the CO2 absorption in the flue gas. Several ILs, such as [NH2emim][BF4], [C4mim][OAc], and [NH2emim[OAc], have been used to capture CO2 of the simulated flue gas in this work. The structural changes of the ILs before and after absorption were also investigated by quantum chemical methods, FTIR, and NMR technologies. However, the experimental results and theoretical calculation showed that the flue gas component SO2 would significantly weaken the CO2 absorption performance of the ILs. SO2 was more likely to react with the active sites of the ILs than CO2. To improve the absorption capacity, the ionic liquid (IL) mixture [C4mim][OAc]/ [NH2emim][BF4] were employed for the CO2 absorption of the flue gas. It is found that the CO2 absorption capacity would be increased by about 25%, even in the presence of SO2. The calculation results suggested that CO2 could not compete with SO2 for reacting with the IL during the absorption process. Nevertheless, SO2 might be first captured by the [NH2emim][BF4] of the IL mixture, and then the [C4mim][OAc] ionic liquid could absorb more CO2 without the interference of SO2.

Selection of efficient absorbent for CO2 capture from gases containing low CO2

Amine-based absorption processes are widely used in natural gas processing, but recently they have been considered for CO2 capture from flue gas emitted from thermal power plants. The main issue of amine used in the CO2 capture process is the high cost of solvent regeneration. So, this issue can be solved by using efficient amine absorbent. The amine type absorbents employed in the experimentation were an aqueous blend of 2-(Diethylamino)ethanol (DEEA) with different types of diamine activators such as piperazine (PZ), 2-(2-aminoethylamino)ethanol (AEEA), hexamethylenediamine (HMDA), ethylenediamine (EDA), and 3-(Dimethylamino)-1-propylamine (DMAPA). An absorption experiment was performed to evaluate the CO2 absorption performance in terms of CO2 loading, absorption capacity, and absorption rate. The experiment was performed to assess the CO2 desorption performance in terms of desorption capacity, desorption rate, cyclic capacity, and regeneration efficiency. From the results of absorption-desorption and comparison with benchmark amine absorbent MEA, the aqueous blend of DEEA and HMDA indicated the best performance for CO2 capture applications among all the tested amine blends.

Correlating Physicochemical Properties of Commercial Membranes with CO2 Absorption Performance in Gas-Liquid Membrane Contactor

The gas-liquid membrane contactor (GLMC) is a promising alternative gas absorption/desorption configuration for effective carbon dioxide (CO2 ) capture. The physicochemical properties of membranes may synergistically affect GLMC performances, especially during the long-term operations. In this work, commercial polypropylene (PP) and polyvinylidene fluoride (PVDF) hollow fiber (HF) membranes were applied to explore the effects of their physicochemical properties on long-term CO2 absorption performances in a bench-scale GLMC rig. PP membranes with pore size of 19 nm, thickness of 0.046 mm, and porosity of 58% achieved high CO2 flux when feeding pure CO2 (5.4 and 24.4×10-3 mol/m2 .s using absorbents of water and 1M monoethanolamine (MEA), respectively) whereas PVDF membranes with pore size of 24 nm, thickness of 0.343 mm, and porosity of 84% presented a good CO2 separation performance from the simulated biogas using 1M MEA (6.8×10-3 mol/m2 .s and 99.9% CH4 recovery). When using water as absorbent, the coupled phenomena of membrane wetting and fouling restricted CO2 transport and resulted in continuous flux loss during the long-term operations. When using MEA as absorbent, both PP and PVDF membranes suffered dramatic flux decline. A series of membrane characterization tests revealed that the morphology, pore size, hydrophobicity, and stability of selected commercial membranes were greatly affected by MEA attack during long-term operations. Therefore, the selection criterion of microporous membranes for high-efficiency and long-term stable CO2 absorption in GLMC processes was proposed. It is envisioned that this study can shed light on improving existing membrane fabrication procedures and the application of novel membrane surface modification techniques to facilitate practical applications of the GLMC technology.