The solubility of carbon dioxide and hydrogen sulfide in a 35 wt% aqueous solution of methyldiethanolamine

The solubility of hydrogen sulfide and carbon dioxide in an aqueous solution containing 35 wt% methyldiethanolamine (MDEA) (3.04 kmol/m³, 4.52 mol/kg) has been measured at 40° and 100°C at partial pressures of the acid gas up to 530 kPa. Some data for hydrogen sulfide in a 50 wt% solution of MDEA (4.38 kmol/m³, 8.39 mol/kg) were also obtained. Also, densities of CO₂-aqueous MDEA solutions were measured at 40°C.     

Aqueous Membranes for the Separation of Gaseous Mixtures

Abstract

Gas mixture separation characteristics of aqueous surfactant films were studied. Permeation constants of carbon dioxide, oxygen, nitrogen, helium, and propane through aqueous films of 2 wt% Ivory Liquid and of 2 wt% Duponol WN were determined. Binary gas mixtures of carbon dioxide-nitrogen and carbon dioxide-propane were enriched in one of the components using a thermally induced driving force.     

Investigation on kinetics of carbon dioxide absorption in aqueous solutions of monoethanolamine + 1, 3-diaminopropane

ABSTRACT

Environmental concerns from global warming and climate change demand carbon dioxide separation from post-combustion gases. Important parameters are involved in choosing the suitable solvent for carbon dioxide separation, including the reaction rate of carbon dioxide and the solvent. In this paper, the kinetics of carbon dioxide (CO₂) absorption in aqueous solutions of Monoethanolamine (MEA) + 1,3-Diaminopropane (DAP), a diamine containing two primary amino group, was developed. The measurements were performed in a stirred cell with a horizontal gas-liquid interface in the temperature range of 313.15–333.15 K and aqueous solutions of 10 wt% MEA + 5 wt% DAP and 12.5 wt% MEA + 2.5 wt% DAP. Experiments were conducted in an isothermal batch reactor with a horizontal gas-liquid interface under pseudo-first-order conditions, enabling the determination of the overall kinetic rate constant from the pressure drop method. Second-order reaction rate constants of CO₂ absorption in amine solutions were estimated using the calculated initial absorption rate. It was found that the rate constants in MEA+ DAP solutions were greater than in MEA solutions which means that DAP increases the reaction rate.     

Modification of ABS Membrane by PEG for Capturing Carbon Dioxide from CO2/N2 Streams

Carbon dioxide capture and storage (CCS) has been propounded as an important issue in greenhouse gas emissions control. In this connection, in the present article, the advantages of using polymeric membrane for separation of carbon dioxide from CO₂/N₂ streams have been discussed. A novel composition for fabrication of a blend membrane prepared from acrylonitrile-butadiene-styrene (ABS) terpolymer and polyethylene glycol (PEG) has been suggested. The influence of PEG molecular weight (in the range of 400 to 20000) on membrane characteristics and gas separation performance, the effect of PEG content (0–30 wt%) on gas transport properties, and the effect of feed side pressure (ranging from 1 to 8 bar) on CO₂ permeability have been studied. The results show that CO₂ permeability increases from 5.22 Barrer for neat ABS to 9.76 Barrer for ABS/PEG20000 (10 wt%) while the corresponding CO₂/N₂ selectivity increases from 25.97 to 44.36. Furthermore, it is concluded that this novel membrane composition has the potential to be considered as a commercial membrane.     

Equilibrium solubility of H2S and CO2 and their mixtures in a mixed solvent

The solubility of hydrogen sulphide, carbon dioxide, and their mixtures has been measured at 40° and 100°C in a mixed solvent consisting of 20.9 wt% MDEA (methyldiethanolamine), 30.5 wt% sulfolane (tetrahydrothiophene-1, 1-dioxide), and 48.6 wt% water. The results have been compared with those for aqueous 2.0 mol/dm³ MDEA and an analogous mixed solvent, containing AMP (2-amino-2-methyl-1-propanol), which are available in the literature. These data were used to modify the solubility model of Deshmukh and Mather (1981) to account for the mixed solvent effects on the system thermodynamics. Results show that the model is useful as a first approximation in predicting acid gas solubilities; agreement with experiment was generally found to be within £15%.     

A comparative study of carbon dioxide capture capabilities between methanol solvent and aqueous monoethanol amine solution

Simulations have been performed to compare the performance of CO₂ capture power between 98.5 wt% methanol solvent and 30 wt% MEA aqueous solution. A general purpose chemical process simulator, PRO/II with PROVISION release 8.3 was used for the modeling of CO₂ capture process. For the simulation of CO₂ capture process using methanol as a solvent, NRTL liquid activity coefficient model was used for the estimation of the liquid phase non-idealities, Peng-Robinson equation of state model was selected for the prediction of vapor phase non-idealities, and Henry’s law option was chosen for the prediction of the solubilities of light gases in methanol and water solvents. Amine special thermodynamic package built-in PRO/II with PROVISION release 8.3 was used for the modeling of CO₂ capture process using MEA aqueous solution. We could conclude that the 30 wt% of MEA aqueous solution showed better performance than the 98.5 wt% methanol solvent in CO₂ capture capability. Through this study, we tried to compare the differences between the two processes from the aspects of capital and operating costs using a commercial process simulator. This will guide the optimal process design in the carbon dioxide capture process.     

Wastepaper gasification with CO2 or steam using catalysts of molten carbonates

In this paper, wastepaper gasification with carbon dioxide or steam has been investigated in the presence of molten carbonate catalysts. The reactions of wastepaper with steam or carbon dioxide have been compared. Hydrogen was the main product on the condition of steam used as reactant gas, but in the case where carbon dioxide was used, the amount of carbon monoxide generated from wastepaper gasification greatly increased via the Boudouard reaction. Different ratios of mixtures of lithium, sodium and potassium carbonates as the catalysts have been tested; the lithium carbonate was found to play a critical role. The reaction rate of carbon conversion was approximately first order for low carbon conversions. Both the rate constants and the activation energies have been calculated at different temperatures (923–1023 K). In additions, the flexibility of this technique was examined with three different types of wastepaper. The results suggest that this process can promote effective use of wastepaper and recovery of carbon dioxide. At 1023 K, a high value of cold gas efficiency of about 95% was acquired.     

The absorption rate of CO2/SO2/NO2 into a blended aqueous AMP/ammonia solution

The Inter-governmental Panel on Climate Change (IPCC) reported that human activities result in the production of greenhouse gases (CO₂, CH₄, N₂O and CFCs), which significantly contribute to global warming, one of the most serious environmental problems. Under these circumstances, most nations have shown a willingness to suffer economic burdens by signing the Kyoto Protocol, which took effect from February 2005. Therefore, an innovative technology for the simultaneously removal carbon dioxide (CO₂) and nitrogen dioxide (NO₂), which are discharged in great quantities from fossil fuel-fired power plants and incineration facilities, must be developed to reduce these economical burdens. In this study, a blend of AMP and NH₃ was used to achieve high absorption rates for CO₂, as suggested in several publications. The absorption rates of CO₂, SO₂ and NO₂ into aqueous AMP and blended AMP+NH₃ solutions were measured using a stirred-cell reactor at 293, 303 and 313 K. The reaction rate constants were determined from the measured absorption rates. The effect of adding NH₃ to enhance the absorption characteristics of AMP was also studied. The performance of the reactions was evaluated under various operating conditions. From the results, the reactions with SO₂ and NO₂ into aqueous AMP and AMP+NH₃ solutions were classified as instantaneous reactions. The absorption rates increased with increasing reaction temperature and NH₃ concentration. The reaction rates of 1, 3 and 5 wt% NH₃ blended with 30 wt% AMP solution with respect to CO₂/SO₂/NO₂ at 313 K were 6.05～8.49×10^?6, 7.16–10.41×10^?6 and 8.02～12.0×10^?6 kmol m^?2s^?1, respectively. These values were approximately 32.3–38.7% higher than with aqueous AMP solution alone. The rate of the simultaneous absorption of CO₂/SO₂/NO₂ into aqueous AMP+NH₃ solution was 3.83–4.87×10^?6 kmol m^?2s^?1 at 15 kPa, which was an increase of 15.0–16.9% compared to 30 wt% AMP solution alone. This may have been caused by the NH₃ solution acting as an alternative for CO₂/SO₂/NO₂ controls from flue gas due to its high absorption capacity and fast absorption rate.     

Experimental study on CO2 hydrate formation in the presence of TiO2, SiO2, MWNTs nanoparticles

ABSTRACT

A series of experiments on CO₂ hydrate formation were carried out in the presence of titanium dioxide (TiO₂), silicon dioxide (SiO₂), multi-walled carbon nanotubes (MWNTs) nanoparticles. The effects of these nanoparticles on induction time, final gas consumption, and gas storage capacity have been investigated at the temperature of 274.15 K and the initial pressure of 5.0 MPa.g. The induction time of CO₂ hydrate formation was remarkably shortened to 12.5 min in the presence of 0.005 wt% MWNTs nanoparticles. The high thermal conductivity and heat capacity of MWNTs nanoparticles presented better heat transfer, and large surface area provided more suitable sites for heterogeneous nucleation of CO₂ hydrate.     

Linear relationships for modeling CO2 absorption in aqueous alkanolamine solutions in a thermodynamically consistent way

A thermodynamically consistent model for the carbon dioxide (CO₂) absorption in aqueous alkanolamine system is of great importance in the research and development of a CO₂ capture process. To facilitate the development of thermodynamic models, linear Gibbs free energy, enthalpy, and heat capacity relationships using well-known amines as reference are used to correlate the standard reference state properties of ionic species with those of molecular species in the electrolyte system, which has been approved to provide a reliable and consistent way to estimate required parameters when there is minimal or no appropriate experimental data available. The proposed relationships have been applied to the development of an electrolyte nonrandom two liquid (NRTL) activity coefficient model for CO₂ absorption in aqueous 1-amino-2-propanol (A2P) solution, as an example to demonstration the methodology. With limited vapor–liquid equilibrium data and other thermodynamic properties, the parameters in the electrolyte NRTL model are identified with good accuracy.     

NEW MODIFIED KENT-EISENBERG MODEL FOR PREDICTING CARBON DIOXIDE SOLUBILITY IN AQUEOUS 2-AMINO-2-METHYL-1-PROPANOL (AMP) SOLUTIONS

A new concept of using multiple apparent constant parameters plus sensitivity analysis was developed based on a modified Kent-Eisenberg model for predicting the carbon dioxide (CO₂) solubility in aqueous 2-amino-2-methyl-l-propanol (AMP) solutions. Three apparent constants of amine protonation, dissociation and physical dissolution of C02 were identified to be the most significant parameters in the system. Previously published data were used to determine these three constants utilizing a nonlinear least-squares technique. The predictions from the present model agree well with all 121 experimental measurements available in the open literature     

The physical solubilities and diffusivities of N<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> in aqueous ammonia solutions on the additions of AMP,glycerol and ethylene glycol

Carbon dioxide (CO₂) is a major greenhouse gas, the emissions of which should be reduced. There are various technologies for the effective separation of CO₂. Of these, chemical absorption methods are generally accepted as the most effective. The monoethanolamine (MEA) process is an effective way to remove CO₂, but is an expensive option for the separation of CO₂ from massive gas-discharging plants. Therefore, ammonia solution, which is less expensive and more effective than MEA, was used for the removal of CO₂. In this study, the physical solubility of N₂O in (ammonia+water), (ammonia+2-amino-2-methyl-1-propanol+water), (ammonia+glycerol+water) and (ammonia+ ethylene glycol+water) was measured at 293, 303, 313, 323 K. Additive concentrations of 1, 3, and 5 wt% AMP, glycerol and ethylene glycol were added for each 9 wt% ammonia solution. A solubility apparatus was used to investigate the solubility of N₂O in ammonia solutions. The diffusivity was measured with a wetted wall column absorber. The “N₂O analogy” is used to estimate the solubility and diffusivity of CO₂ in the aqueous ammonia solutions. OriginPro 7.5 was used to correlate the solubility and diffusivity of N₂O in ammonia solutions. The parameters of the correlation were determined from the measured solubility and diffusivity.     

Effect of acid gases on the solubility of n-propylmercaptan in 50 wt% methyl-diethanolamine aqueous solution

In this communication, we have measured the solubility and partition coefficient of n-propylmercaptan in 50 wt% MDEA aqueous solution at 366 K in the presence of single and mixed acid gases (CO₂ and H₂S). A static analytic method was used for performing all the measurements. Methane was used to maintain the total pressure of the system in equilibrium cell. The concentration of n-propylmercaptan in aqueous phase was in the 50–1000 ppm (mole) range. The effect of acid gas loadings on the physical and chemical solubility of n-propylmercaptan is discussed.     

Determination of kinetics of CO2 absorption in solutions of 2‐amino‐2‐methyl‐1‐propanol using a microfluidic technique

The kinetics for the reactions of carbon dioxide with 2‐amine‐2‐methyl‐1‐propanol (AMP) and carbon dioxide (CO₂) in both aqueous and nonaqueous solutions were measured using a microfluidic method at a temperature range of 298–318 K. The mixtures of AMP‐water and AMP‐ethylene glycol were applied for the working systems. Gas‐liquid bubbly microflows were formed through a microsieve device and used to determine the reaction characteristics by online observation of the volume change of microbubbles at the initial flow stage. In this condition, a mathematical model according to zwitterion mechanism has been developed to predict the reaction kinetics. The predicted kinetics of CO₂ absorption in the AMP aqueous solution verified the reliability of the method by comparing with literatures’ results. Furthermore, the reaction rate parameters for the reaction of CO₂ with AMP in both solutions were determined. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4358–4366, 2015     

Simultaneous absorption of CO<Subscript>2</Subscript> and SO<Subscript>2</Subscript> into aqueous AMP/NH<Subscript>3</Subscript> solutions in binary composite absorption system

To enhance the absorption rate for CO₂ and SO₂, aqueous ammonia (NH₃) solution was added to an aqueous 2-amino-2-methyl-1-propanol (AMP) solution. The simultaneous absorption rates of AMP and a blend of AMP+ NH₃ for CO₂ and SO₂ were measured by using a stirred-cell reactor at 303 K. The process operating parameters of interest in this study were the solvent and concentration, and the partial pressures of CO₂ and SO₂. As a result, the addition of NH₃ solution into aqueous AMP solution increased the reaction rate constants of CO₂ and SO₂ by 144 and 109%, respectively, compared to that of AMP solution alone. The simultaneous absorption rate of CO₂/SO₂ on the addition of 1 wt% NH₃ into 10 wt% AMP at a p _A1 of 15 kPa and p _A2 of 1 kPa was 5.50×10⁻⁶ kmol m⁻² s⁻¹, with an increase of 15.5% compared to 10 wt% AMP alone. Consequently, the addition of NH₃ solution into an aqueous AMP solution would be expected to be an excellent absorbent for the simultaneous removal of CO₂/SO₂ from the composition of flue gas emitted from thermoelectric power plants.     

Simultaneous absorption of carbon dioxide,sulfur dioxide and nitrogen dioxide into aqueous 2-amino-2-methy-1-propanol

The absorption mechanism of three acidic gases in alkali solution, such as the system of carbon dioxide, sulfur dioxide, and nitrogen dioxide in 2-amino-2-methyl-1-propanol (AMP), was used to predict the simultaneous absorption rates using the film theory. Diffusivity, Henry constant and mass transfer coefficient of each gas were used to obtain the theoretical enhancement factor of each component. The theoretical molar fluxe of each gas was obtained by an approximate solution of mass balances with reaction regions of the first order reaction of CO₂ and instantaneous reactions of SO₂ and NO₂ in CO₂-SO₂-NO₂-AMP system. From the comparison between the theoretical total fluxes of these gases and the measured ones, the solubility and the reaction rate between each gas and AMP influenced its molar flux.     

Reaction kinetics of 2‐((2‐aminoethyl) amino) ethanol in aqueous and non‐aqueous solutions using the stopped‐flow technique

Observed pseudo‐first‐order rate constants (k_o) for the reaction between CO₂ and 2‐((2‐aminoethyl) amino) ethanol (AEEA) were measured using the stopped‐flow technique in an aqueous system at 298, 303, 308 and 313 K, and in non‐aqueous systems of methanol and ethanol at 293, 298, 303 and 308 K. Alkanolamine concentrations ranged from 9.93 to 80.29 mol m^?3 for the aqueous system, 29.99–88.3 mol m^?3 for methanol and 44.17–99.28 mol m^?3 for ethanol. Experimentally obtained rate constants were correlated with two mechanisms. For both the aqueous‐ and non‐aqueous‐AEEA systems, the zwitterion mechanism with a fast deprotonation step correlated the data well as assessed by the reported statistical analysis. As expected, the reaction rate of CO₂ in the aqueous‐AEEA system was found to be much faster than in methanol or ethanol. Compared to other promising amines and diamines studied using the stopped‐flow apparatus, the pseudo‐first‐order reaction rate constants were found to obey the following order: PZ (cyclic‐diamine) > EDA (diamine) > AEEA (diamine) > 3‐AP (primary amine) > MEA (primary amine) > EEA (primary amine) > MO (cyclic‐amine). The reaction rate constant of CO₂ in aqueous‐AEEA was double that in aqueous‐MEA, and the difference increased with an increase in concentration. All reaction orders were practically unity. With a higher capacity for carbon dioxide and a higher reaction rate, AEEA could have been a good substitute to MEA if not for its high thermal degradation. AEEA kinetic behaviour is still of interest as a degradation product of MEA. © 2012 Canadian Society for Chemical Engineering     

Analysis of the heat of reaction and regeneration in alkanolamine-CO<Subscript>2</Subscript> system

The estimation of regeneration heat of absorbent is important because it is a key factor that has an effect on the process efficiency. In this study, thermal stability and regeneration heat of aqueous amine solutions such as monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), N-methyldiethanolamine (MDEA), and 1,8-diamino-pmenthane (KIER-C3) were investigated by using TGA-DSC analysis. The thermal characteristics of the fresh and CO₂ rich amine solutions were estimated. The CO₂ rich amine solutions were obtained by VLE experiments at T=40 °C. The regeneration heat of aqueous MEA solution was 76.991–66.707 kJ/mol-CO₂, which is similar to heat of absorption. The reproducibility of the results was obtained. The regeneration heat of aqueous KIER-C3 20 wt% solution (1.68 M) was lower than that of aqueous MEA 30 wt% solution (4.91 M). Therefore, the KIER-C3 can be used as an effective absorbent for acid gas removal.     

脱碳MEA/叔胺的性能

应用于工业烟气的CO₂吸收剂以一乙醇胺（MEA）为主,改进MEA使其成为更高效的吸收剂是吸收脱CO₂的关键之一。本文对相同浓度的MEA和3种不同结构的叔胺：即N,N-二乙基乙醇胺（DEAE）、N,N-二甲基乙醇胺（DMAE）和N-甲基二乙醇胺（MDEA）水溶液,以及MEA与这3种叔胺的混胺水溶液（MEA/叔胺）对CO₂的吸收和再生性能开展了实验研究,以期达到改进MEA性能的目的。结果表明,叔胺与MEA的吸收行为完全不同;MEA吸收性能好,叔胺再生性能强。MEA/多胺的吸收初期速率下降,但是再生量和再生率都较MEA高。叔胺与MEA在吸收和再生过程中都存在交互作用,交互作用与叔胺种类及吸收时间有关,其中MDEA与MEA之间的协同作用最强。     

填料塔中混合胺吸收二氧化碳的研究

在填料塔中考察了常压下混合胺吸收剂[20%乙醇胺(MEA)+2% N-甲基二乙醇胺(MDEA),20%羟乙基乙二胺(AEE)+2% MDEA]对CO_2的吸收与解吸效果.同时测得了AEE+MDEA混合胺体系吸收剂脱除空气中体积分数约10%的CO_2的体积总传质系数K_Ga_v的近似值,并考察了进口气体中CO_2摩尔流量、气体流量、液体流量等因素对K_Ga_v的影响.实验结果表明,AEE+MDEA吸收效果明显好于MEA+MDEA,并且二者解吸效果相同;K_Ga_v随CO_2摩尔流量、气体流量、液体流量增大而增大.