Potassium Glycinate Research Articles

Modeling of CO2 absorption capabilities of amino acid solutions using a computational scheme

AbstractIn this communication, modeling of carbon dioxide absorption by various amino acid solutions is presented as a function of operational parameters using the Least‐Squares Support Vector Machine (LSSVM) algorithm integrated with three different evolutionary algorithms, namely Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Hybrid GA and PSO (HGAPSO). A databank containing 255 data of carbon dioxide absorption by amino acids of potassium taurate, potassium glycinate, potassium prolinate, and potassium lysinate at different temperatures, partial pressures, and concentrations was prepared from different sources to train and test the proposed algorithms. The models were applied to estimate carbon dioxide absorption by amino acid solutions in terms of temperature, molar concentration, equilibrium partial pressure, molecular weight, number of hydrogen bond donor, number of hydrogen bond acceptor, and number of rotatable bond. The R2 values of LSSVM optimized by HGAPSO, PSO, and GA are 0.9944, 0.9915, and 0.9891, respectively, and the various errors were determined close to zero. On the other hand, the visual comparison of models outputs and actual carbon dioxide adsorption data was used to clarify performances of the models. By comparison analysis, it was found that the LSSVM‐HGAPSO is the most accurate model for estimation of carbon dioxide loading. Also, comparison of our proposed models results with previously reported artificial neural network results indicates the impressive estimation capability of LSSVM algorithm. According to sensitivity analysis, it becomes obvious that pressure is the most effective parameter on carbon dioxide absorption.

Absorption of CO2 from flue gas under oscillating gas flow conditions in gas-solvent hollow fibre membrane contactors

Membrane gas-solvent contactors are a viable approach for the absorption of carbon dioxide (CO2) into solvents, such as potassium glycinate, compared to traditional solvent absorption. The hollow fibre membrane design does have limitations, as the presence of the membrane adds extra resistance to mass transfer compared to traditional solvent absorption. To reduce the impact of this extra resistance it is necessary to increase mass transfer in the solvent and gas phase boundary layers. This investigation aimed to increase mass transfer in the gas phase boundary layer of a membrane contactor process by applying oscillating gas flow conditions. For an asymmetric polydimethylsiloxane membrane contactor undergoing oscillating gas flow conditions, an average increase of 19% in overall mass transfer coefficient (KG) compared to non-oscillating gas flow was observed, for 15 wt% potassium glycinate solvent. The oscillating frequency of the gas phase had only a minor impact on performance, above 2 Hz, implying that oscillation of the gas phase was important for mixing, not the rate of the oscillation. Alternatively, KG approximately doubled in value as a function of increased oscillating amplitude. This was due to the resulting pressure wave producing localized increases in the partial pressure driving force for mass transfer across the membrane. For the membrane contactors studied, mass transfer correlations, in terms of Sherwood number, were proposed for the oscillating and non-oscillating flow conditions and fitted to the experimental data. This outcome highlighted the importance of inducing mixing within the gas phase to maximise mass transfer in membrane contactors.

Mass transfer characteristics of a continuously operated hollow-fiber membrane contactor and stripper unit for CO2 capture

Mass transfer performance of a polypropylene hollow-fiber membrane contactor as part of a continuously operated CO2 capture unit with amino acid salt (potassium glycinate) absorbent and vacuum solvent regeneration was studied. The effects of key operating parameters on the absorption mass transfer characteristics were explored. Without vacuum stripping, absorption rate was found to be limited by low CO2 desorption efficiency from the loaded absorbent solution in the stripping unit, resulting in high solvent CO2 loadings and limited chemical absorption rates. Introduction of vacuum stripping greatly improved desorption performance, resulting in improved steady-state absorption performance. The overall mass transfer coefficient increased at higher stripping temperatures and lower vacuum pressures in the range of 60−80 °C and 300−800 mbar (abs). The overall mass transfer coefficient increased with increasing liquid flow rate, and the highest value reached was 1.8 ∙ 10−4 m s-1. The individual mass transfer coefficients in absorption were calculated based on mass transfer correlations and experimental data, including estimation of the enhancement factor for chemical absorption. The overall mass transfer resistance was found to be dominated by the liquid-side resistance, at almost 90 % of the total resistance. The estimated membrane mass transfer coefficient was low compared to a theoretical value assuming non-wetted operation, suggesting potential partial wetting of the membrane. Stable performance of the unit and the membrane contactor was demonstrated during a stability test with over 30 h of operation.

Modeling and Simulation of the Simultaneous Absorption/Stripping of CO2 with Potassium Glycinate Solution in Membrane Contactor.

Global warming is an environmental problem caused mainly by one of the most serious greenhouse gas, CO2 emissions. Subsequently, the capture of CO2 from flue gas and natural gas is essential. Aqueous potassium glycinate (PG) is a promising novelty solvent used in the CO2 capture compared to traditional solvents; simultaneous solvent regeneration is associated with the absorption step. In present work, a 2D mathematical model where radial and axial diffusion are considered is developed for the simultaneous absorption/stripping process. The model describes the CO2/PG absorption/stripping process in a solvent–gas membrane absorption process. Regeneration data of rich potassium glycinate solvent using a varied range of acid gas loading (mol CO2 per mol PG) were used to predict the reversible reaction rate constant. A comparison of simulation results and experimental data validated the accuracy of the model predictions. The stripping reaction rate constant of rich potassium glycinate was determined experimentally and found to be a function of temperature and PG concentration. Model predictions were in good agreement with the experimental data. The results reveal that the percent removal of CO2 is directly proportional to CO2 loading and solvent stripping temperature.

Chemical Capture of CO2 by Glycine Salt Solution

The role of carbon dioxide in global warming is one of the contemporary environmental issues and it is, therefore, necessary to have available technology to capture the released CO2 into the atmosphere. Amino acids have the same amine functionality as alkanolamines with similar behavior towards CO2 absorption. The solubility of carbon dioxide in potassium glycinate (KG) solutions with different concentrations at various temperatures was measured. The results showed that the mole of CO2‌‌ adsorbed, increases both by temperature and the concentration of KG. The against the KG concentration at different temperatures was fitted with a sigmoidal function so that the moles of CO2‌‌ adsorbed can be reproduced in the temperature range of 300.15 to 327.15 K and the concentrations of 0.01-1.00 M of KG within the experimental errors.

Direct Air Capture of CO2 with Aqueous Amino Acids and Solid Bis-iminoguanidines (BIGs)

We report a bench-scale direct air capture (DAC) process comprising CO2 absorption with aqueous amino acid salts (i.e., potassium glycinate, potassium sarcosinate), followed by room-temperature reg...

Precipitation study of CO2-loaded glycinate solution with the introduction of ethanol as an antisolvent

Focused beam reflectance measurement (FBRM) and 13C nuclear magnetic resonance (13C NMR) analysis were used to study the precipitation process of CO2-loaded potassium glycinate (KGLY) solutions at different CO2 loadings, during the addition of ethanol as an antisolvent at a rate of 10 mL·min−1. The volume ratio of ethanol added to the KGLY solution (3.0 mol·L−1, 340 mL) ranged from 0 to 3.0. Three solid-liquid-liquid phases were formed during the precipitation process. The FBRM results showed that the number of particles formed increased with CO2 loading and ethanol addition for CO2-unsaturated KGLY solutions, whilst for CO2-saturated KGLY solution it first increased then decreased to a stable value with ethanol addition. 13C NMR spectroscopic analysis showed that the crystals precipitated from the CO2-unsaturated KGLY solutions consisted of glycine only, and the quantity crystallised increased with CO2 loading and ethanol addition. However, a complex mixture containing glycine, carbamate and potassium bicarbonate was precipitated from CO2-saturated KGLY solution with the maximum precipitation percentages of 94.3%, 31.4% and 89.6%, respectively, at the ethanol volume fractions of 1.6, 2.5 and 2.3.

Development of aqueous-based phase change amino acid solvents for energy-efficient CO2 capture: The role of antisolvent

The energy penalty is a primary limitation for the implementation of the aqueous solvents for large-scale post-combustion CO2 capture processes. In this study, a novel aqueous-based phase change solvent, composed of potassium glycinate (GlyK, reactive species), water (H2O, solvent) and dimethylformamide (DMF, antisolvent) was developed to improve the energy efficiency of CO2 capture. To examine the role of the antisolvent, a series of aqueous-based amino acid solvents (GlyK-X) with different DMF:H2O (X) volume ratios was prepared, fully characterized and assessed. It was observed that a CO2-free phase appeared at the top of the aqueous-based amino acid GlyK-X solvents after CO2 absorption which can be easily separated and recycled to the absorption column and save energy. The results showed that the GlyK-60 solvent with DMF:H2O volume ratio of 60:40 had a very high CO2-free phase volume (63%). Moreover, the GlyK-60 solvent exhibited 26.1% (0.433–0.546 mol CO2/mol GlyK) enhancement in CO2 absorption capacity, 38.5% (130–80 min) decrease in regeneration time and 59.1% reduction in relative heat duty compared to the conventional aqueous GlyK solvent. Overall, the outcomes confirmed that the aqueous-based phase change GlyK-60 solvent is a viable solvent option for large-scale CO2 capture with extra-low energy consumption and a key to the success of Paris Climate Accord.

Insights into a membrane contactor based demonstration unit for CO2 capture

A continuously operated CO2 capture unit, based on absorption in a membrane contactor and low-temperature vacuum desorption, is demonstrated. The major advantage of membrane contactors is their high specific interfacial area per unit volume. The unit is designed to be modular to allow different absorption membrane modules and stripping units to be tested, with the aim of capturing CO2 from simulated flue gases at concentrations down to the ambient concentration. In addition, desorption can be performed under vacuum to improve the desorption efficiency. The experimental unit incorporates comprehensive measurements and a high level of automation, with heat integration and continuous measurement of electricity consumption providing real-time estimates of the energy consumed in the capture process.In preliminary tests, the results of which are described herein, a 3 M Liqui-Cel™ polypropylene hollow-fiber membrane module and a glass vacuum chamber were used for absorption and desorption, respectively, along with a potassium glycinate amino acid salt absorbent solution. This solution has high surface tension and is fully compatible with the polypropylene membrane unit used. In preliminary tests, the highest observed CO2 flux was 0.82 mol m−2 h−1, with a CO2 product purity of above 80%. The calculated overall mass transfer coefficient was comparable to reference systems. The performance of the unit in its current setup was found to be limited by the desorption efficiency. Due to the low desorption rates, the measured specific energy consumption was exceedingly high, at 4.6 MJ/mol CO2 (29.0 MW h/t) and 0.8 MJ/mol CO2 (5.0 MW h/t) of heat and electricity, respectively. Higher desorption temperatures and lower vacuum pressures enhanced the desorption efficiency and reduced the specific energy consumption. The energy efficiency could be improved via several methods in the future, e.g., by applying ultrasound radiation or by replacing the current vacuum chamber stripping unit with a membrane module or some other type of desorption unit.

Mass Transfer Performance and Empirical Correlations of CO2 Absorption from CO2-Rich Gas Stream in a Random Packed Column

CO2 chemical absorption from the gas streams featured with high CO2 concentration into diethanolamine (DEA), potassium glycinate (PG) and potassium L-argininate (PA) was investigated in a random packed column. Effects of main operation parameters including absorbent concentration, solvent flow rate, solvent temperature, the initial CO2 loading, gas flow rate and CO2 partial pressure on CO2 mass transfer performance were experimented according to the overall volumetric gas phase mass transfer coefficient (KGae) . Based on the experimental data, the empirical correlations for easily predicting the KGae value were proposed for all the three solvents, and most of the calculated KGae values are in agreement with the experimental KGae values with an average absolute deviation less than 8%. PA can obtain the highest KGae value than PG and DEA. According to the empirical correlations of KGae, the most significant influence factor to KGae is the solvent temperature for PG, the solvent flow rate for PA and the active absorbent concentration for DEA, respectively.

Experimental studies on carbon dioxide absorption using potassium carbonate solutions with amino acid salts

Absorption and desorption of CO2 using K2CO3 solutions promoted by three amino acid salts (AASs), potassium glycinate (PG), potassium lysinate (PL) and potassium L-argininate (PA), were evaluated using 40% CO2 at 40 °C and with pure N2 at 80 °C, respectively. The addition of all 3 AASs clearly enhanced both absorption and desorption of CO2 compared to single K2CO3 solution. PA + K2CO3 solution showed the highest CO2 cyclic capacity of 0.678 mol CO2/mol absorbent, while the highest CO2 absorption and desorption rates of 39.8 and 17.6 mol CO2 L−1 s−1 were achieved by PG + K2CO3 solution. Finally, simulated biogas containing 40% of CO2 and 60% of CH4 was used as test gas in a hollow fiber membrane contactor. PG and PA promoters presented higher CO2 absorption flux and removal efficiency than PL promoters in K2CO3 solution within low Gas/Liquid ratio region. Stable CO2 removal performances for all three promoters were observed at elevated temperature and pressure for 60 min operation.

Thin-film-composite hollow fiber membranes containing amino acid salts as mobile carriers for CO2 separation

In this work, defect-free thin-film-composite (TFC) hollow fiber membranes containing various amino acid salts as CO2 facilitated transport carriers were fabricated via dip-coating. Four different amino acid salts, i.e., potassium prolinate (ProK), potassium argininate (ArgK), potassium glycinate (GlyK) and potassium cysteinate (CysK), were selected and embedded within polyvinyl alcohol (PVA) matrix. TGA, FTIR, SEM and humid mixed gas permeation test were used for the evaluation. Experiments show that adding amino acid salts into the PVA matrix significantly increases the CO2 permeance with little influence on the CO2/N2 selectivity. ProK was found the most effective within the four investigated mobile carriers; The addition of 40% ProK into the PVA matrix nearly doubled the CO2 permeance (from 399 to 791 GPU). The PVA/amino acid salt membranes also exhibited good long-term stability, in which both CO2 permeance and CO2/N2 selectivity remained nearly unchanged in a 20-h test and after a two-week shutdown period.

Virgin coconut oil (VCO) and potassium glycinate (PG) mixture as absorbent for carbon dioxide capture

In this work, the performance of potassium glycinate (PG) and virgin coconut oil (VCO) mixture as potential green solvent for carbon dioxide (CO2) capture was investigated. The mixture was prepared by mixing PG with 50 weight percent (w/w%) VCO and characterised using density meter, tensiometer and Fourier Transform Infrared (FT-IR) spectrometer. The densities of PG, VCO and PG-VCO mixtures measured from 303.15 to 333.15 K were fitted against an empirical correlation. Viscosities of pure VCO and PG-VCO mixtures were measured at 308.15 K. The solubility of absorbents were studied by bubbling CO2 directly into the solution and measuring mass increase of the solution. Experimental results showed that the density of PG, VCO, and PG-VCO mixtures decreased with increase in temperature and increased with increase in PG concentration. On the other hand, the viscosity of PG-VCO mixtures were reduced by approximately half compared to pure VCO. Moreover, the addition of VCO into the PG solution enhanced the solubility of CO2 in the mixture due to the additional physical interaction between VCO and CO2 molecules. Maximum CO2 absorption of 3.942 mol CO2/mol of PG was observed for 0.1 M PG-VCO mixture. A mechanism study also revealed that the presence of VCO contributed to the formation of bicarbonate ion and protonated potassium glycinate after the CO2 absorption.

Modeling and simulation of CO2 separation from CO2/CH4 gaseous mixture using potassium glycinate, potassium argininate and sodium hydroxide liquid absorbents in the hollow fiber membrane contactor

The emission of CO2 greenhouse gas is one of the most momentous causes of environmental problems such as global warming. Hence, the sequestration of CO2 acid gas from gaseous streams is considered as a mandatory process to control the detrimental impressions of CO2 emission. In the present investigation, a mathematical modeling and a two dimensional comprehensive simulation is developed with the aim of evaluating the removal performance of CO2 acid gas from CO2/CH4 gaseous mixture. As the novelty, potassium argininate (PA), potassium glycinate (PG) and sodium hydroxide (NaOH) are used as promising liquid solvents in the hollow fiber membrane contactor (HFMC) and the best absorbing agent for capturing CO2 is introduced. The validation of model predictions is implemented based on the comparison of simulation results of CO2 and experimental data using sodium hydroxide (NaOH) in a wide range of absorbent temperature and liquid velocity. Comparison of experimental data and simulation results for CO2 flux in wide ranges of absorbent (NaOH) temperature and absorbent velocity illustrates excellent agreements with average deviations of less than 4% and 3.7%, respectively. On the basis of simulation results, potassium argininate (PA) shows higher CO2 separation efficiency compared with the other liquid solvents. The order for CO2 separation rate is PA > PG > NaOH. The results imply that increment in the operational parameters such as porosity, module length and liquid absorbents velocity positively affect the separation percentage of CO2 while, increasing in gas velocity, membrane tortuosity and initial concentration of CO2 deteriorate the separation efficiency of CO2, considerably.

Molecular Dynamics Study on Carbon Dioxide Absorbed Potassium Glycinate Aqueous Solution

Molecular dynamics (MD) simulations have been performed to investigate the effects on structure, transport properties, and dynamical properties in the potassium glycinate aqueous solution caused by carbon dioxide (CO2) absorption. The optimized structure and charges of constituents of the solution, such as the glycine zwitterion, have been determined by Gaussian09 using the density functional theory. The obtained pair distribution functions, g ij (r)’s, show the significant distribution difference of bicarbonate ion, $${\text{HCO}}_{3}^{ - }$$ , around the glycine anion and glycine zwitterion. The shear viscosity and diffusion coefficient obtained by MD show different CO2 concentration dependences. The frequency dependent diffusion coefficient D i (ν) for N and C in glycine ions are mainly influenced by the cage effect of surrounding water molecules, whereas D i (ν) for H show the characteristic vibration due to the structure difference of the glycine ions.

A robust predictive tool for estimating CO 2 solubility in potassium based amino acid salt solutions

Abstract The acid gas absorption in four potassium based amino acid salt solutions was predicted using artificial neural network (ANN). Two hundred fifty-five experimental data points for CO2 absorption in the four potassium based amino acid salt solutions containing potassium lysinate, potassium prolinate, potassium glycinate, and potassium taurate were used in this modeling. Amine salt solution's type, temperature, equilibrium partial pressure of acid gas, the molar concentration of the solution, molecular weight, and the boiling point were considered as inputs to ANN to prognosticate the capacity of amino acid salt solution to absorb acid gas. Regression analysis was employed to assess the performance of the network. Levenberg–Marquardt back-propagation algorithm was used to train the optimal ANN with 5:12:1 architecture. The model findings indicated that the proposed ANN has the capability to predict precisely the absorption of acid gases in various amino acid salt solutions with Mean Square Error (MSE) value of 0.0011, the Average Absolute Relative Deviation (AARD) percent of 5.54%, and the correlation coefficient (R2) of 0.9828.

Mathematical Modeling and Numerical Simulation of CO2 Removal by Using Hollow Fiber Membrane Contactors

Abstract In this study, a mathematical model is proposed for CO2 separation from N2/CO2 mixtureusing a hollow fiber membrane contactor by various absorbents. The contactor assumed as non-wetted membrane; radial and axial diffusions were also considered in the model development. The governing equations of the model are solved via the finite element method (FEM). To ensure the accuracy of the developed model, the simulation results were validated using the reported experimental data for potassium glycinate (PG), monoethanol amine (MEA), and methyldiethanol amine (MDEA). The results of the proposed model indicated that PG absorbent has the highest removal efficiency of CO2, followed by potassium threonate (PT), MEA, amino-2-methyl-1-propanol (AMP), diethanol amine (DEA), and MDEA in sequence. In addition, the results revealed that the CO2 removal efficiency was favored by absorbent flow rate and liquid temperature, while the gas flow rate has a reverse effect. The simulation results proved that the hollow fiber membrane contactors have a good potential in the area of CO2 capture.

The use of monoethanolamine and potassium glycinate solvents for CO2 delivery to microalgae through a polymeric membrane system

We have previously shown that a combined system involving solvent absorption, membrane desorption and microalgal cultivation can provide an effective approach to carbon dioxide capture and utilisation (Energy Environ. Sci., 2016, 9, 1074). In this article, we evaluate aqueous solutions of monoethanolamine (MEA) and potassium glycinate (PG) for membrane desorption of CO2, and compare these with our previous work using potassium carbonate (K2CO3). Enhanced growth of Chlorella sp. was observed with 20wt%PG at 0.5 CO2 loading (moles of CO2 absorbed per mol solvent) relative to a baseline control in which carbon dioxide was only available from atmospheric diffusion. Similar growth rates to the control were observed for PG at 0.2 loading. For MEA, algal growth was accelerated at 0.5 loading but was inhibited at 0.2 loading. This was related to the volatile MEA crossing the membrane and poisoning the algae. Considering the kinetics of CO2 absorption into the solvent, the improvement of microalgal growth and the system stability in case of solvent leakage, amino acids such as PG are the ideal solvent for this application.

Recent Progress on the Performance of Different Rate Promoters in Potassium Carbonate Solvents for CO2 Capture

Over recent years our research group has examined the performance of a range of rate promoters in potassium carbonate solvent for carbon dioxide absorption. Promoters including boric acid, potassium glycinate, potassium prolinate, potassium sarcosinate and a thermally stable carbonic anhydrase enzyme have been studied either with the stopped flow technique, a wetted wall column or in the pilot plant located at The University of Melbourne in Australia. The carbonic anhydrase enzyme was shown to have the best promotion performance. However, improvements are required in further improving thermal stability and recycling options in order for the enzyme to be applied in industrial solvent absorption processes. Amino acid salts including potassium sarcosinate, prolinate and glycinate were proven to have high promotion performance at bench scale. Pilot plant results showed that the promotion performance of boric acid was poor, while potassium glycinate was a good rate promoter with an increase in absorption rate of up to 5–6 times when adding 10 wt. % glycinate into 40–45 wt. % potassium carbonate solvent.

Experimental and correlation study of corrosion rate, absorption rate and CO2 loading capacity in five blend solutions as new absorbents for CO2 capture

In this study, trisodium phosphate (TSP) was selected as a base absorbent and five additives, including triethylenetetramine (TETA), 2-methylpiperazine (2-MPZ), 2-Amino-2-methyl-1-propanol (AMP), potassium glycinate (K-Gly) and potassium prolinate (K-Pro) were added to improve the absorption performance in terms of corrosion rate, absorption rate and CO2 loading capacity. The absorption experiments of various blend solutions have been carried out using a vapor-liquid equilibrium apparatus at additive mole fraction range from 0.2 to 0.4, CO2 partial pressures up to 50 kPa and at temperatures 303.15, 313.15 and 323.15 K. The results indicated that all the evaluated TSP + additives solutions have higher CO2 solubility and lower corrosion rate compared to MEA. However, the only TETA + TSP showed a better absorption rate than MEA. Moreover, the absorption rate for TSP mixtures containing amine additives were all faster than the single TSP. Finally, ANOVA analysis was employed for all the blend solutions and a correlation for predicting CO2 solubility was successfully developed.