Monoethanolamine System Research Articles

Structure–activity relationship of a dual-function amine-based electrolyte for integrated CO2 capture and electrochemical conversion

Integrated carbon dioxide (CO2) capture and electrocatalytic reduction processes through dual-function amine-based electrolytes and their integration into a single reactor can lead to significant energy savings, simplified process flow, and reduced transportation risks. This work investigates the structure–activity relationship of dual-functional amine-based electrolytes for CO2 capture and electrocatalytic reduction and develops an efficient dual-functional amine-based electrolyte system. We investigated 10 different amine-based solutions for their CO2 capture and reduction performances. The substituents on the nitrogen atom of the intermediate carbamate and the positions of the hydroxyl and branched groups affect the capture and electrochemical reduction. The 1,3-propanediamine system demonstrated enhanced CO2 solubility uptake (58.1 %), Faradaic efficiency (10.6 %), and current density (52.1 %) compared with the monoethanolamine system, indicating its potential as a dual-function amine-based electrolyte. Furthermore, density functional theory calculations indicated that the charge distribution of carbamate and the dissociation of C–N bonds directly influence the adsorption of carbamates on the electrode surface and the Faradaic efficiency of the reduced products. In addition, reaction path analysis based on the zwitterionic mechanism indicated that intermediates (carbamate R1R2NCOO-) with higher electronegativity are more conducive to adsorb onto the electrode surface and inhibit hydrogen generation from protonated amines (R1R2NHH+). The results suggest that the selection or design of dual-functional amine-based electrolytes should prioritize amines with straight alkanol chains rather than branched ones, which do not form intramolecular hydrogen bonds or heterocyclic structures. This work provides directions and guidance for designing and developing dual-functional electrolytes for integrated carbon capture and electrocatalytic conversion technologies.

Process simulation and optimization for post-combustion CO2 capture pilot plant using high CO2 concentration flue gas as a source

This work mainly focuses on process simulation and optimization of a high-concentrated CO2 chemical absorption process using aqueous amine solutions based on both pilot plant data and process modeling. To optimize operating parameters for reducing energy consumptions, this study explores the influence of process structure and operational parameters on the product purity, capture rate, and energy consumption, which would provide theoretical and technical support for optimizing high-concentration CO2 capture. At first, the rate-based absorption/desorption models are established and well-verified by a total of 25 sets of pilot plant data, which shows high accuracy for reliable model predictions. Under an annual absorption capacity of 50 tons at a 90% capture rate and 95% product purity, the optimal case using Monoethanolamine (MEA) solution shows an increased CO2 capture rate of 12.37% and a decreased unit energy consumption of 22.5%. After flowsheet optimization, a new system of blended MEA, Methyl diethanolamine (MDEA), and 2-Amino-2-methyl-1-propanol (AMP) solution is designed to capturing high-concentrated CO2 under the same conditions. Compared with the MEA system, its specified energy consumption is reduced by 10.35% and its CO2 capture capacity increases by 11.6 tons annually.

Potassium β–alanine – A promising agent for reducing carbon capture cost via electrochemically mediated amine regeneration

Electrochemically mediated amine regeneration (EMAR) for CO2 capture is a promising substitute for traditional organic amine–based CO2 capture by replacing the thermal process with electricity. To avoid problems such as oxidative degradation, toxicity, volatilization, and precipitation of organic amine absorbent, potassium β–alanine was suggested as an absorbent using EMAR process for the first time in this study. The CO2 absorption performance under different copper loading and chemical reactions were studied, and cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry and the Taffel extrapolation method were used to study the electrochemical characterization. Compared to the benchmark monoethanolamine (MEA) system, a smaller potential difference between oxidation and reduction peak was acquired in the potassium β–alanine system, of which the energy consumption was only 44.1% of the MEA system at the current of 100 A/m2. The cathode Faraday efficiency in the potassium β–alanine system was 101.9% higher than that in the MEA system at the current density of 25 A/m2. Furthermore, the result of scanning electron microscope of the electrode surface after desorption showed that potassium β–alanine absorbent improved the inhomogeneity of the electrode surface and was in favor of uniform current distribution. Overall, potassium β–alanine can be used as a more environmentally friendly absorbent in the EMAR system and has great potential to further reduce the actual energy consumption and improve the Faraday efficiency and cycling performance.

Corrosion performance of carbon/stainless steel in amine‐based solvents under different conditions for CO2 chemical absorption process

AbstractThe overall corrosion behavior of S304 stainless steel and A3 carbon steel in 30 wt.% MEA (monoethanolamine) and AMP/MEA (2‐amino‐2‐methyl‐1‐propanol / monoethanolamine) blended amine solutions at 40–100°C was investigated. The characterization analysis of the corroded material surfaces was performed, and the changes in the properties of both solvents after long‐term immersion corrosion were measured, including the accumulation of heat stable salts (HSS) and viscosity changes. The results of the long‐term immersion corrosion experiments showed that the corrosion rate of S304 stainless steel was significantly lower than that of A3 carbon steel in both amine solutions. However, the corrosion rate of both materials exhibited a similar trend, initially decreasing and then stabilizing over time. Due to the higher concentration of carbonate ions in the AMP/MEA system, it exhibited better overall corrosion resistance and degradation resistance compared to the MEA system. The main component of the corrosion product on carbon steel was identified as Fe2(OH)2CO3. The electrochemical test results showed that the corrosion current of S304 stainless steel was much smaller than that of A3 carbon steel, and its charge transfer resistance was much higher, indicating that it was less prone to electron loss in the organic amine solutions. Additionally, the AMP/MEA system exhibited superior corrosion resistance. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

IR spectroscopic study of the hydrogen bond network in the water–3-amino-1-propanol system and its comparison with the spatial network of hydrogen bonds in the water–monoethanolamine system

IR spectroscopy was used to explore the water–3-amino-1-propanol (3AP) system in the range of 400–4000 cm-1. Based on the stretching vibrations of OH, NH2 and CH groups and skeletal bending vibrations of 3AP it was concluded that mixed spatial networks are formed in the water–3AP system that predominate at medium 3AP concentrations. The obtained results are similar to the IR spectroscopic data for the water–monoethanolamine system, viz., the networks of both amino alcohols are incorporated into the spatial

Determination of mass transfer coefficient from biogas purification process by mono ethanol amine (MEA)

Biogas is a renewable energy source, which can be produced from organic waste such as palm oil mill effluent (POME), through an anaerobic fermentation process. Biogas requires a purification process to remove the content of hydrogen sulfide (H2S) and carbon dioxide (CO2). The purpose of this study is to calculate the value of mass transfer coefficient in biogas purification process, namely in the process of chemical absorption of H2S and CO2 gases in raw biogas by monoethanolamine (MEA) absorbent. Biogas purification was carried out using a bubble column absorber, where raw biogas was flowed into a column containing a MEA absorber of 0.678 L. The biogas content from the column was analyzed using biogas content measuring device (Biogas 5000 ©). The overall mass transfer coefficient values in gas phase obtained from this study are 0.182–1.027 s−1 for H2S – MEA system, and 0.674–3.993 s−1 for CO2 –MEA system. The overall mass transfer coefficient of CO2 – MEA from this study is greater than that of previous studies.

Technical and economic analysis of retrofitting a post-combustion carbon capture system in a Thai coal-fired power plant

Mitigating CO2 emissions is an important clean energy research topic. Post-combustion carbon capture is a well established and vital carbon capture technology for existing fossil-fueled power plants. In this work, monoethanolamine (MEA) based carbon capturing unit was designed using AspenPlus V.10 software for a 300 MWe power unit of Mae Moh power plant in Thailand. Technical and economic analysis of retrofitting a lean aqueous MEA system was investigated. From the simulation study, it was revealed that the optimal lean CO2 feeding for the amine-based carbon separation plant was about 0.2 mol/mol using packed columns with Sulzer Mellapak 250Y product. The optimal liquid-to-gas ratio with a flue gas containing 15% CO2 was approximately 3.0. Furthermore, the optimal total costs of the plants were less than 55 $/ton of CO2 captured.

Force-Field-Based Computational Study of the Thermodynamics of a Large Set of Aqueous Alkanolamine Solvents for Post-Combustion CO2 Capture.

The ability to predict the thermodynamic properties of amine species in CO2-loaded aqueous solutions, including their deprotonation (pKa) and carbamate to bicarbonate reversion (pKc) equilibrium constants and their corresponding standard reaction enthalpies, is of critical importance for the design of improved carbon capture solvents. In this study, we used isocoulombic forms of both reactions to determine these quantities for a large set of aqueous alkanolamine solvent systems. Our hybrid approach involves using classical molecular dynamics simulations with the general amber force field (GAFF) and semi-empirical AM1-BCC charges (GAFF/AM1-BCC) in the solution phase, combined with high-level composite quantum chemical ideal-gas calculations. We first determined a new force field (FF) for the hydronium ion (H3O+) by matching to the single experimental pKa data point for the well-known monoethanolamine system at 298.15 K. We then used this FF to predict the pKa values for 76 other amines at 298.15 K and for all 77 amines at elevated temperatures. Additionally, we indirectly relate the H3O+ hydration free energy to that of H+ and provide expressions for intrinsic hydration free energy and enthalpy of the proton. Using the derived H3O+ FF, we predicted the pKa values of a diverse set of alkanolamines with an overall average absolute deviation of less than 0.72 pKa units. Furthermore, the derived H3O+ FF is able to predict the protonation enthalpy of these amines when used with the GAFF. We also predicted the carbamate reversion constants of the primary and secondary amine species in the data set and their corresponding standard heats of reaction, which we compared with the scarcely available experimental data, which are often subject to significant uncertainty. Finally, we also described the influence of electronic and steric effects of different molecular fragments/groups on the stabilities of the carbamates.

The effect of the nature of the сhalcogen atom on the extraction and adsorption characteristics of chalcogen-containing oligomers based on chlorex

The extraction and adsorption characteristics of chalcogen-containing oligomers derived from chlorex and elemental chalcogens in the hydrazine hydrate–base systems were studied. Sulphur- and selenium-containing oligomers synthesised in hydrazine hydrate–monoethanolamine systems are soluble in organic solvents. The as-obtained solutions are capable of extracting the following ions from water solutions: Hg2+, Cd2+, Zn2+, Pb2+, Cu2+ and Ni2+. Oligomers synthesised in the hydrazine hydrate–water–KOH system (sulphur- and selenium-containing oligomers) and a tellurium-containing oligomer obtained in the hydrazine hydrate–KOH system were used as adsorbents. It was assumed that the extraction and adsorption of metal ions by chalcogen-containing oligomers is carried out through the formation of complexes in which the chalcogen atoms act as ligands. The effect of the nature of chalcogen atoms on the possibility of forming complexes, i.e. on the extraction and adsorption properties of the oligomers used, was considered using the theory of hard and soft acids and bases (HSAB). According to this theory, the cations Hg2+ and Cd2+ belong to soft acids, while the cations Zn2+, Pb2+, Cu2+ and Ni2+ belong to acids of intermediate hardness. Chalcogen atoms are classified as soft bases. The conducted experiment showed that Hg2+ and Cd2+ ions are easily extracted and adsorbed by all the oligomers used, while the intermediate-hardness cations most easily interact with the sulphur-containing oligomers. The formation of oligomer–metal complexes was confirmed by analysing IR and 77Se NMR spectra recorded for sulphur- and selenium-containing oligomers before and after the extraction. The recorded IR spectra contained obvious changes in the nature of the absorption bands due to the stretching vibrations of the C–S and C–Se bonds. An additional signal of de-screened selenium nuclei was observed in the 77Se NMR spectrum. An insignificant change in the nature of the IR spectra in the region of stretching C–O vibrations indicated a weak participation of oxygen in the formation of complexes. It can be assumed that the role of oxygen in maintaining the high rates of extraction and adsorption is associated with an increase in the flexibility of macromolecules, which ensures a more favourable geometry for complex formation.

Flexible Operation of the Potassium Taurate Solvent Absorption Section for CO2 Removal in a Coal-Fired Power Plant

To reduce global warming effects due to the increase of the carbon dioxide concentration in the atmosphere, CO2 can be removed from large emitting industrial sources as power production stations with several available technologies. Among these, the most common one is chemical absorption with aqueous amines. The benchmark solvent is MonoEthanolAmine (MEA), though presenting a few disadvantages such as being corrosive and toxic and requiring large amounts of energy for its regeneration. An aqueous solution of potassium taurate has the potential to replace MEA because of degradation resistance, low toxicity and low energy requirements. In addition, at specific conditions, it can enhance the chemical absorption of carbon dioxide by precipitating and forming a slurry with presence of solid taurine. The considered process scheme is similar to the one for the MEA system (basically composed of absorption column and stripping or distillation column), with the addition of a heat exchanger for the dissolution of any solid particle present in the system before being fed to the regeneration section. When applied to a power plant, CO2 removal decreases the revenues from the sale of electricity. Indeed, the requirement of thermal energy for running the reboiler of the regeneration section and of electrical energy for compressing the separated CO2 are some of the main drawbacks of the application of Carbon Capture and Storage (CCS) and may result in a significant decrease in the power output and profit. Operating the CO2 removal section in flexible mode significantly reduces effects on the profit and CO2 emissions. The research reported here focuses on determining the best operating conditions for the potassium taurate solvent absorption section with the aim of limiting the impact of the CO2 capture operation and maintaining a substantial reduction of CO2 emissions in a coal-fired power plant. The process of post-combustion scrubbing is well-suited for operation in flexible mode because it is located downstream of the power production system. For simulating the process, a tool previously developed and based on the commercial software ASPEN Plus® has been employed. The process simulator had been user customized for the representation of the chemical reacting system of carbon dioxide with potassium taurate, which is not present by default in the database. The Vapor-Liquid-Solid Equilibrium (VLSE) is considered in the thermodynamic model and rate-based simulations, also taking into account the kinetics, have been performed. An in-house tool, taking as input the data for electricity demand and price and the result of simulations in ASPEN Plus®, has been then used for analyzing the flexible operation of the plant. The study of a flexible solution for carbon dioxide removal has been carried out in this work, considering the amount of electricity sold during the day for which data are available from the Italian national service institution.

IR Spectroscopy of Solutions of Dimethylsulfoxide in Monoethanolamine

Solutions of dimethylsulfoxide (DMSO) in monoethanolamine (MEA) are studied via IR spectroscopy on a Bruker Tensor 37 FT-IR spectrometer in the wavenumber range of 900–4000 cm−1. The concentrations of DMSO are 2–66 mol %. The region of the stretching vibrations of hydrogen-bonded OH and NH2 groups (2800–4000 cm−1) and the region of the S=O vibrations of DMSO (900–1100 cm−1) are studied in detail. The obtained data are compared to the IR spectra of solutions of DMSO in ethylene glycol in the regions of OH and S=O stretching vibrations. The effect the NH2 group in the MEA molecule has on the interaction in the DMSO–MEA system and the physicochemical properties of this system as compared to ethylene glycol solutions of DMSO are discussed.

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.

Modelling and simulation of a biomass-based integrated gasification combined cycle with carbon capture: comparison between monoethanolamine and potassium carbonate

There are global efforts to reduce the impacts from climate change by limiting increases in temperature to 1.5 °C until 2030, and achieve carbon neutrality by 2050. Thus, it is necessary to design new neutral processes and systems that can meet the varying and growing demands of the population in terms of energy, water and food. One of the main carbon emitters and contributors to climate change is the energy industry, which primarily uses oil and natural gas as an energy source. Fortunately, alternative resources are available such as renewable energies that assemble various environmental and economic benefits. However, more work is necessitated to efficiently utilise these resources by designing, analysing, and optimising existing and new renewable energy-based processes. Therefore, this study proposes a net negative carbon emissions energy system that utilises waste biomass as a feedstock. A biomass based integrated gasification combined cycle combined with a post combustion carbon capture unit by means of chemical absorption is designed and analysed. Two different chemical solvents are used for comparison: Monoethanolamine (MEA) and potassium carbonate. The proposed integrated system is modelled and simulated in Aspen Plus software, and is analysed thermodynamically in terms of energy and exergy efficiencies. A sensitivity analysis is also conducted to assess the effect of varying operating conditions such as flowrate, and temperature of the lean solvent, and the pressure inside the stripper. At design conditions with 80% carbon capture, the system generates 419 kW of electricity and operates at -0.32 kg/kWh of CO2 for both the potassium carbonate and MEA systems.

Modelling and simulation study of CO2 capturing process in coal fired power plant using various amine solvents

In the present world, Scientists are very much concern on to reduce the concentration level of carbon dioxide in environment to save the world. In the present work, the CO2 capturing efficiencies of three different amine solvents were analyzed. The selected solvents were mono-ethanol amine (MEA), solvent containing mixture of methyl diethanol amine (MDEA) and piperazine (PZ) called activated -MDEA and aqueous ammonia (NH3) solution. Rigorous simulation method was considered in the current study. The effects of different key parameters for different solvents on the CO2 removal efficiency were analyzed. Packing height, solvent temperature and absorber height were the significant influential parameters for MEA system whereas for activated-MDEA (a-MDEA), those are the ratio of the solvent to feed quantity and the mixed solvent PZ concentration level. For aqueous NH3 solution, absorber and stripper’s temperature, CO2 loading, concentration of NH3, height of the absorber, lean and rich solvent flow rate, boil up ratio, regeneration energy, temperature of the condenser, and duty of the reboiler were considered. The comparative study showed that MEA process recovered the maximum CO2 from flue gas. But it was suffered by the maximum regeneration duty. a-MDEA with PZ recovered 91% CO2. Overall, technically, a-MDEA was the best choice as solvent. Compared to a-MDEA and MEA, aqueous ammonia was identified as more propitious and environment friendly solvent due to its satisfactory performance and easy availability.

Regulating Phase Separation Behavior of a DEEA-TETA Biphasic Solvent Using Sulfolane for Energy-Saving CO2 Capture.

Biphasic solvents containing mixed amines have a phase separation behavior and energy-efficient regeneration for CO2 capture. However, the trade-off between the CO2 absorption capacity and the volume ratio of the CO2-rich phase presents a critical challenge to the reducing potential in regeneration energy consumption. In this study, sulfolane was proposed to regulate the phase separation behavior of a N,N-diethylethanolamine (DEEA)-triethylenetetramine (TETA) biphasic absorbent by simultaneously decreasing the volume ratio and increasing the CO2 loading of the rich phase, without sacrificing the high CO2 capacity. In the DEEA-TETA-sulfolane biphasic absorbent, sulfolane acted as a phase splitter and physical activator. The replacement of a part of H2O by hydrophobic sulfolane contributed to a substantial decrease in the volume ratio of the rich phase from 83 to 39% and an increase in CO2 loading of the rich phase from 3.10 to 4.92 mol/L. The regeneration heat decreased to 1.81 GJ/t CO2, 26.4% less than DEEA-TETA, and 54.6% less than the 5 M monoethanolamine system. Moreover, by promoting the mass transfer coefficient of CO2 in DEEA-TETA-sulfolane to 1.8 times the original DEEA-TETA system, sulfolane was validated as a physical activator. Our study provides a promising strategy for regulating the phase separation behavior of biphasic solvents and enhancing the regeneration energy efficiency for CO2 capture.

Моделирование процесса адсорбции в системе жидкость – твердое тело: регрессионный анализ извлечения меди из водных растворов цеолитом Холинского месторождения, модифицированным серосодержащим полимером

This article describes the formation of an effective sorbent for heavy metal ions by modifying natural zeolite (clinoptilolite type, Kholinskoye deposit). The modification was carried out by applying the network of a sulphur-containing polymer on the zeolite surface. For the formation of a polymer network, elemental sulphur was dissolved in the hydrasine hydrate–monoethanolamine system to generate polysulphide anions (in particular, S2 2- ). During the contact of the obtained sulphur solution with zeolite, polysulphide anions and the monoethanolamine entering the zeolite pores were concentrated on the surface. Further polycondensation of S2 2- anions with 1,2,3-trichloropropane (epichlorohydrine production waste) resulted in the formation of a reticulated sulphur-containing polymer covering the zeolite surface. Such a sorbent provides immediate solution to the problems concerned with utilisation of organochlorine wastes and purification of technological media containing heavy metals. Extraction of metals by the obtained sorbent was studied using model solutions with a metal concentration of 5000 mg/L. Encouraging results were obtained for five metals. Detailed information on the extraction of copper ions from aqueous solutions is presented. Experimental data was obtained on the effect of pH on the sorption efficiency of copper ions, as well as on the thermodynamic and kinetic characteristics of adsorption under static and dynamic conditions. The complex coordination mechanism of Cu (II) sorption by modified zeolite was confirmed using IR-spectroscopy. Since the thermodynamic and kinetic dependencies frequently deviate from the classical laws during sorption by the complex coordination mechanism, regression analysis was used to process the experimental data. As the result, nonlinear models were obtained fairly accurately describing experimental data on the extraction of copper ions by modified zeolite. The obtained regression models can be applied in further research of the new sorbent and in designing installations for extracting copper compounds from technological media.

Comparison of life-cycle assessment between bio-catalyzed and promoted potassium carbonate processes and amine-based carbon capture technologies

Up until today, the technology used for the capture and production of pure CO2 in post-combustion applications for both use and sequestration relies primarily on the use of chemical amine solvents such as monoethanolamine (MEA). However, these solvents require significant amounts of valuable, high-grade process heat for solvent regeneration and suffer from substantial operational and environmental issues including degradation, toxic aerosol emissions, sensitivity to flue gas contaminants, and corrosivity. CO2 Solutions Inc (CSI) recently developed and deployed a new technology to solve these challenges by employing a non-toxic low-cost, stable salt solution as an absorption solution and the carbonic anhydrase enzyme as a catalyst for carbon management. The result is both fast CO2 absorption kinetics and significantly reduced energy costs by allowing to use low-grade heat to drive the solution regeneration. This study aims to analyze and compare the environmental profile of capture processes such as CSI, MEA and UNO MK3 (a precipitating potassium carbonate separation process). The context of the study is CO2 capture from the flue gas stream of a 550 MW coal-fired power station in the midwestern USA. To fulfill the objective, we performed an attributional cradle-to-gate LCA comparing the three systems. This study was conducted according to the requirements of ISO 14040 & 14044 and reviewed by an independent panel which concluded that “The LCA requirements of ISO 14040 and ISO 14044 have been answered in the best possible manner.”Data were mainly based on process simulation of the three technologies. The impact assessment was carried out with the Impact 2002+ method. This method considers four indicators at endpoint level (Climate change, Human health, Ecosystem quality and Resources) and sixteen indicators at midpoint level (for instance Aquatic Acidification or Ozone formation).Results show that the CSI carbon capture unit has significantly lower potential impacts than the MEA and UNO MK3 units. The CSI system presents lower scores than the MEA and the UNO MK3 systems for all midpoint and endpoint indicators. The operation stage, and more especially its energy consumption, is the main contributor to the environmental profile of all three systems. The CSI system differs radically from the MEA and UNO MK3 systems as it can use hot water instead of steam for its regeneration step. Hot water is a waste from the power plant, whereas steam consumption reduces the production of electricity at the power plant, which needs to be compensated elsewhere. In this study, it is considered that these losses of electricity production will affect the regional market in which the power plant is located, and therefore the lost electricity is produced by an average electricity grid mix coming from this regional market.Other inputs do not contribute significantly to the environmental profile of the systems at endpoint level. Among them, chemical inputs are the top contributors. However, the midpoint category where CSI technology differentiates itself the most from other technologies is when comparing the MEA Respiratory Organics score, which is 3.5 times higher than CSI. The several sensitivity analysis conducted typically do not affect the conclusion.

The retrofitting of a coal-fired subcritical steam power plant for carbon dioxide capture: A comparison between MCFC-based active systems and conventional MEA

The major technological driver in energy and industrial sectors is the reduction of CO2 emissions. Huge technological effort is ongoing towards efficiency improvement of conversion systems, to reduce fossil fuel consumption. Capture and sequestration of CO2 on the flue gases represents an invaluable technology and among the only ones able to sustain the fossil fuel energy economy which cannot be replaced in short-term.In many cases, it produces significant energy penalties on the reference plant, being implemented through passive systems. In other cases, defined as active systems, it fulfils the goal of carbon capture without energy consumption or with energy production. In this regard, Molten Carbonate Fuel Cell (MCFC) concentrates CO2 at the anode exhaust, making easier the separation phase and increasing, also, electrical energy production.Therefore, a physically-based model of the MCFC was developed to assess the positive aspects related to the CO2 remover application, when it is integrated to a 250 MW coal-fired power plant. The removal capacity has been evaluated up to 95% and the calculated additional electricity produced can increase the overall efficiency of about 4% with respect to original value. The steam needed by the fuel cell can be extracted from the original steam power plant or it can be produced by a dedicated steam generator. These two options have been compared in terms of energetic and environmental performance. A cost analysis has been done in order to evaluate the best integration opportunity and to provide a comparison to a more conventional MEA (monoethanolamine) system.

Nonaqueous amine-based absorbents for energy efficient CO2 capture

High energy consumption for CO2 capture using aqueous amines is still a major drawback limiting its deployment on a global scale. In this work, the absorption-desorption performance of CO2 into several blends of monoethanolamine (MEA) or diethanolamine (DEA) with glycol ethers (2-methoxyethanol (2ME) and 2-ethoxyethanol (2EE)) as nonaqueous solvents has been investigated at ambient pressure. Reaction mechanisms and the relative heat duty for these nonaqueous systems were also explored and compared with those of the aqueous MEA. Results showed that the nonaqueous absorbents with 5.0 M MEA had comparable absorption capacity with aqueous 5.0 M MEA and higher desorption efficiency resulting in a larger cyclic capacity (1.45 mol kg−1). Higher partial pressure ratio of CO2 to solvent vapor under the desorption conditions was also observed for these nonaqueous systems. 13C NMR, FTIR spectra and online conductivity analysis provided evidences that CO2 can react with MEA in nonaqueous solvents forming the ionic couples (i.e. protonated MEA and carbamate) as well as carbamic acid at high CO2 loading. The mixture of MEA and 2ME or 2EE could significantly reduce the energy consumption by about 55% as compared to the benchmark aqueous 5.0 M MEA system.

Volumetric properties of monoethanolamine and alcohol binary mixtures at different temperatures and 0.1 MPa

In this experimental, the densities of monoethanolamine (MEA) + alcohol binary mixtures were measured at temperatures from (293.15 to 333.15) K at 0.1 MPa. The studied alcohols include straight-chain ones, ethanol, n-propanol and n-butanol, and branched-chain ones, isopropanol, isobutanol and tertbutanol. From the experimental density values, we calculated the molar volume (Vm), the thermal expansion coefficient (αp) and excess molar volume (VmE). The VmE values for the six binary systems are all negative ranging from (−1.020 to −0.064) cm3·mol−1. For straight-chain alcohol mixtures, the VmE values follow the increasing order of ethanol < n-propanol < n-butanol. And for the branched-chain alcohol mixtures, the VmE values follow the increasing sequence of tertbutanol < isobutanol < n-butanol. All these result from the intermolecular interactions and structural characteristics. For smaller ethanol molecule and MEA, the molar volume is quite similar to each other. However, VmE value for ethanol + MEA system is the most negative. Therefore, the formation of hydrogen bonds plays a leading role for excess molar volume in small molecule alcohol systems. On the other hand, for larger butanol molecule + MEA systems, steric effect leads to a decrease in excess molar volume with the increase in butanol molar volume. Furthermore, the VmE values were correlated with Redlich-Kister polynomial equation with the largest deviation of 0.048.