Absorption of carbon dioxide in aqueous MDEA solution coupling dust suppression under atomization

ABSTRACT

Large amounts of CO₂ and dust particles coming from power plant flue need to be captured and removed before flue is discharged into the air. In present work, absorption of carbon dioxide in aqueous N-methylidiethanolamine (MDEA) solution coupling dust suppression has been studied in an atomization absorption column, with MDEA concentrations ranging from 0.1 to 0.5mol/L, and with atomization frequencies ranging from 50 to 80 HZ. The obtained experimental results show that absorption rate of CO₂ in aqueous MDEA solution can be enhanced when the absorption process couples a dust suppression one under the condition of atomization. The reason for it is attributed to the adsorption of droplets on the solid particles which restrains the amount of entrainment and makes more droplets contact with gas so as to increase effective mass transfer area, thus resulting in the increase of CO₂ absorption rate. The range of obtained enhancement factor is from 1.1 to 1.7. Mass transfer enhancement factor increases with the increase of MDEA concentration and atomization frequency at a certain range. Effective mass transfer areas and entrainment ratios suppressed have been calculated based on theoretic research. The results calculated agree with our experimental phenomena, and support the enhancement mass transfer mechanism proposed.     

Absorption of carbon dioxide into aqueous methyldiethanolamine

Gas absorption rates in a laminar liquid jet were measured for carbon dioxide in methyl- diethanolamine (MDEA) solutions. It was found that for the short contact times (<0.012s) of these absorption experiments there is only a small effect of any reaction between carbon dioxide and MDEA. Solubilities and molecular diffusivities for carbon dioxide in aqueous MDEA are estimated from measurements with nitrous oxide. The absorption rate data are described well using the solubilities and diffusivities measured in this work. Solubilities were measured over the temperature range 15 to 35°C and for MDEA concentrations up to 40%. Diffusion coefficients and viscosities were measured over the same temperature range and MDEA concentrations up to 20%.     

Influence of polyethylene oxide on absorption of carbon dioxide into aqueous <Emphasis Type="Italic">N</Emphasis>-methyldiethanolamine solution

Carbon dioxide was absorbed into aqueous polyethylene oxide (PEO) solution containing N-methyldiethanolamine (MDEA) in a flat-stirred vessel to investigate the effect of non-Newtonian rheological behavior of PEO on the chemical absorption rate of CO₂, where the reaction between CO₂ and MDEA was assumed to be a first-order reaction with respect to the concentration of CO₂ and MDEA, respectively. A unified correlation equation containing the Deborah number, which reflects the viscoelastic properties of a non-Newtonian liquid, was used to obtain the volumetric liquid-side mass transfer coefficient of carbon dioxide in aqueous PEO solution. The elastic properties of PEO accelerated the absorption rate of CO₂ compared with that of a Newtonian liquid based on the same values of viscosity.     

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.     

MDEA溶液吸收CO_2动力学研究

采用圆盘塔,在常压、温度30～70℃、MDEA浓度1.75～4.28kmol/m~3条件下,以流动循环法测定了MDEA水溶液吸收CO_2的速率.利用自吸式搅拌鼓泡反应器测得的气液平衡关系整理数据,所有吸收速率数据均可用假一级快速可逆反应的吸收速率表达式来描述,即N_(co_2)=H_(co_2)(D_(co_2l)k_2c°_(Am)(1-a)~(1/2)(p_(co_2)-p_(co_2l)~*)式中k_2=5.86×10~6exp(-3984/T)并由此求得表观活化能为33.13kJ/mol.本文还讨论了温度、转化度和MDEA浓度对CO_2吸收速率的影响.     

The development of kinetics model for CO2 absorption into tertiary amines containing carbonic anhydrase

CO₂ absorption into aqueous solutions of two tertiary alkanolamines, namely, MDEA and DMEA with and without carbonic anhydrase (CA) was investigated with the use of the stopped‐flow technique at temperatures in the range of 293–313 K, CA concentration varying from 0 to 100 g/m³ in aqueous MDEA solution with the amine concentration ranging from 0.1 to 0.5 kmol/m³, and CA concentration varying from 0 to 40 g/m³ in aqueous DMEA solution with the amine concentration ranging from 0.05 to 0.25 kmol/m³. The results show that the pseudofirst‐order reaction rate (k_{0, amine}; s^?1) is significantly enhanced in the presence of CA as compared with that without CA. The enhanced values of the kinetic constant in the presence of CA has been calculated and a new kinetics model for reaction of CO₂ absorption into aqueous tertiary alkanolamine solutions catalyzed by CA has been established and used to make comparisons of experimental and calculated pseudo first‐order reaction rate constant (k_{0, with CA}) in CO₂‐MDEA‐H₂O and CO₂‐DMEA‐H₂O solutions. The AADs were 15.21 and 15.17%, respectively. The effect of pKa on the CA activities has also been studied by comparison of CA activities in different tertiary amine solutions, namely, TEA, MDEA, DMEA, and DEEA. The pKa trend for amines were: DEEA > DMEA > MDEA > TEA. In contrast, the catalyst enhancement in amines was in the order: TEA> MDEA> DMEA> DEEA. Therefore, it can be seen that the catalyst enhancement in the amines decreased with their increasing pKa values. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

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.     

Simultaneous Absorption of H2S and Co2 Into Aqueous Methyldiethanolamine

Abstract

The tertiary araine methyldiethanolamine (MDEA) is finding increasing application as a chemical solvent for selective absorption of hydrogen sulfide from gases containing hydrogen sulfide and carbon dioxide. Gas streams of this type include some natural gases, synthetic gases from coal and heavy oil gasification and tail gases from sulfur plants. Selectivity for H2S is needed either to enrich Glaus sulfur plant feed in H2S or to remove only H₂S when CO₂ removal is not necessary or economic. For the absorption of hydrogen sulfide into MDEA, the reaction which occurs can be considered to be instantaneous while carbon dioxide undergoes a second-order reaction with MDEA.

In this work, the simultaneous absorption of two gases into a liquid containing a reactant with which both gases react is modelled using the film theory. Physical properties and kinetic rate parameters used in the model have been measured in our laboratory. The model is used to study the effect of process variables on the selectivity of MDEA for H₂S over C0₂. The simultaneous absorption of H₂S and CO₂ gases into aqueous MDEA is studied experimentally using a continuous stirred tank absorber. Experimental absorption rates are compared to predictions based on a multicomponent mass transfer model. The average deviations of the theoretical calculations from the experimental results are 10.2% and 12.9% for C0₂ and H₂S, respectively.     

ABSORPTION OF CARBON DIOXIDE INTO AQUEOUS DIETHANOLAMINE SOLUTIONS

The rates of absorption of pure carbon dioxide into aqueous diethanolamine solutions were measured at 25^°C in a liquid-jet column and a wetted-wall column. Experimental results were analyzed with the chemical absorption theory based on the penetration model. Physical solubility of carbon dioxide in aqueous diethanolamine solutions was determined from the absorption rates measured in a near pseudo first-order reaction regime and was found to show a salting-out effect. The measured absorption rates were in good agreement with the theoretical predictions for gas absorption with an irreversible third-order reaction.     

Absorption of Carbon Dioxide into Aqueous Solution of Sodium Glycinate

Abstract

Carbon dioxide was absorbed into aqueous solution of sodium glycinate (SG) at different SG concentrations, CO₂ partial pressures, and temperatures in the range of 0.5–3.0 kmol/m³, 25–101.3 kPa, and 298–318 K, respectively, using a stirred semi-batch vessel with a planar gas-liquid interface. Both the reaction order and rate constant are determined from gas absorption rates under the fast reaction regime. The reaction was found to be first order with respect to both CO₂ and SG. The activation energy for the CO₂-SG reaction has been found to be 59.8 kJ/mol. The second-order reaction rate constants were used to obtain the theoretical values of absorption rate based on the film theory.     

Absorption of co2 into aqueous tertiary amine/mea solutions

Absorption rates for CO₂ into aqueous solutions of TEA, MDEA and blends of MEA with MDEA and TEA were measured in a stirred cell by a method similar to that used by Laddha and Danckwerts (1981). Second order rate constants for CO₂-TEA and CO₂-MDEA were obtained from the single amine data for temperatures in the range of 25-60°C. A modified pseudo first order model based on the film theory is used to predict the rate of absorption of CO₂ into mixed amine solutions. This model accounts for the variation of amine concentration in the film and assumes a shuttle mechanism for rate enhancement. Bulk liquid concentrations of the various species present are obtained from a simplified thermodynamic model. The model predicts absorption rates that are in agreement with experimental measurements.     

Interfacial area in three-phase fluidized beds

On the basis of mass transfer models and the results of our previous investigations, Danckwerts' pseudo-first order reaction method was adapted for the determination of interfacial area in a three-phase fluidized bed. The results of our experimental investigations on the absorption of carbon dioxide in aqueous sodium hydroxide are presented. The works of other authors are analysed.     

Effects of piperazine concentration and operating conditions on the solubility of CO2 in AMP solution at low CO2 partial pressure

In this study, new equilibrium solubility data for carbon dioxide in aqueous solutions of 2-amino-2-methyl-1-propanol and piperazine (PZ) are provided. The two famous Deshmukh–Mather and Kent Eisenberg thermodynamic models are utilized to predict the CO₂ absorption. The experimental data show that the solubility of CO₂ decreases as the temperature increases. Our data suggest that the addition of PZ has different effects on CO₂ absorption under different partial pressure of the CO₂ in the gas stream. For high partial pressure, the addition of PZ promotes the absorption performance. However, at low CO₂ partial pressure, PZ addition results in less saturated CO₂ loading. The Deshmukh–Mather model can provide an accurate prediction of the experimental data at high partial pressure of CO₂ (i.e. AAD = 3.4%) whereas the modified Kent–Eisenberg model can capture the inverse effects of the PZ at low partial pressure and provides a relatively good approximation of experimental data at low partial pressure (i.e. AAD = 10%).     

CO2 absorption into a phase change absorbent: Water-lean potassium prolinate/ethanol solution

Phase change solvents are attractive energy-efficient absorbents for carbon dioxide (CO₂) capture due to CO₂-rich phase formation. Potassium prolinate + water + ethanol (ProK/W/Eth) solution has shown good capture characteristics as a promising one in our previous work. In this work, absorption rate of CO₂, solubility of N₂O, and heat of absorption for ProK/W/Eth solution were investigated using a stirred cell reactor and a CPA201 reaction calorimeter and these results were also compared with the aqueous ProK and 30 mass% MEA solutions. Using ethanol as a solvent can substantially increase the CO₂ physical solubility and the absorption rate of CO₂ in ProK/W/Eth solutions is far higher than that in aqueous 30 mass% MEA solutions especially at a low CO₂ loading range. Solid precipitation, obtained from the liquid-to-solid phase change absorption, was analyzed by ¹³C NMR and DSC-TGA. The enthalpy change for ProK/W/Eth solutions at various CO₂ loading was also discussed.     

Absorption Rate of CO_2 into MDEA Aqueous Solution Blended with Piperazine and Diethanolanline

Absorption rate of CO2 into aqueous solution of N-methyldiethanolamine (MDEA) blended with di-ethanolamine (DEA) and piperazine (PZ) was studied and a kinetic model was established. It is shown that homogeneous activation mechanism could explain this absorption process. The absorption rate coefficients of carbon dioxide into MDEA aqueous solution blended with DEA, PZ or DEA+PZ were compared with each other. The results demonstrated that the different activation effect of DEA, PZ and DEA+PZ on the carbon dioxide absorption comes from the difference in CO2 combination rate, transport of PZ and DEA to MDEA and the regeneration rate of PZ and DEA.     

Application of Gas Absorption Theories to o-Cresol Ozonation in Water

The reaction rate between ozone and o–cresol in aqueous solution at pH 2 has been studied. According to the absorption theories, the kinetic regime of the process in the experimental conditions investigated, corresponds to an irreversible fast pseudo-first order reaction between non-dissociated o-cresol and ozone. Similar values for the rate constant are deduced from the different theories. Therefore the film theory, having a simple mathematical basis, seems to be the most appropriate model for this kinetic study.     

Chemical Absorption of Carbon Dioxide into Aqueous Solution of Potassium Threonate

Carbon dioxide was absorbed into aqueous solution of potassium threonate (PT) at different concentrations of PT and CO₂, and temperatures in the range of 0.1–1.0 kmol/m³, 10.1–101.3 kPa, and 293-313 K, respectively, using a stirred semi-batch vessel with a planar gas-liquid interface. Both the reaction order and rate constant were determined from gas absorption rates under the fast pseudo-first-reaction regime. The reaction was found to be first order with respect to both CO₂ and PT, and its activation energy has been found to be 40.6 kJ/mol. From a comparison of the reaction kinetics by the overall reaction scheme with those by the elementary reaction scheme based on the zwitterions mechanism, the overall reaction between CO₂ and PT has been found to be equivalent to the formation of zwitterions.     

Mass transfer of carbon dioxide in aqueous polyacrylamide solution with methyldiethanolamine

Carbon dioxide was absorbed into aqueous polyacrylamide (PAA) solution containing methyl-diethanolamine (MDEA) in a flat-stirred vessel to investigate the effect of non-Newtonian rheological behavior of PAA on the rate of chemical absorption of CO₂, where the reaction between CO₂ and MDEA was assumed to be a first-order reaction with respect to the molar concentration of CO₂ and MDEA, respectively. The liquid-side mass transfer coefficient (k_L), which was obtained from the dimensionless empirical equation containing the viscoelasticity properties of a non-Newtonian liquid, was used to estimate the enhancement factor due to chemical reaction. PAA with elastic property of non-Newtonian liquid made the rate of chemical absorption of CO₂ accelerate compared with a Newtonian liquid     

MDEA-MEA混合有机胺水溶液吸收CO_2

研究了N-甲基二乙醇胺(MDEA)和一乙醇胺(MEA)混合有机胺水溶液吸收CO_2的过程.根据双膜理论,导出了简化近似宏观动力学模型,用以预测混合有机胺水溶液吸收CO_2的速率.该模型考虑了化学反应之间的交互作用,用三次多项式近似表示反应组分在膜中的浓度分布.在各种条件下测定了搅拌反应器内MDEA/MEA水溶液吸收CO_2的速率.模型计算值与实验测定值符合良好.     

Hydrothermal synthesis of multiwalled TiO2 nanotubes and its photocatalytic activities for Orange II removal

The solvothermal synthesis of multiwalled TiO₂ nanotubes (MWTNTs) with the reaction of titanium dioxide (TiO₂) nanoparticles and sodium hydroxide aqueous solution at moderate temperature is presented. The kinetic and isotherm studies were investigated for Orange II removal mechanism. MWTNTs were prepared in length 70–200 nm, average diameter 4–10 nm, and inter-shell spacing 0.78 nm. Different characterizations were performed to confirm anatase and mesoporous structure of MWTNTs. An improvement in properties as compared to commercial TiO₂ was observed; specific surface area 244.81 m²/g and band gap 3.0 eV. An excellent photocatalytic activity for Orange II removal was exhibited using synthesized MWTNTs.