Benchmark Monoethanolamine Research Articles

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.

Harvesting CO2 reaction enthalpy from amine scrubbing

Amine-based CO2 capture technology suffers high energy consumption, of which the exergy loss of CO2 absorption enthalpy is a significant contributor to the process irreversibility. Recovery and utilisation of CO2 absorption enthalpy is therefore of paramount significance to advance amine technology towards low capture cost. The present study proposed a reaction enthalpy harvesting amine process (REHA) with the purpose to directly utilise the CO2 absorption enthalpy for building heating. In the REHA process, we redefine the operational conditions of CO2 capture process with dual targets of high capture performance as well as high enthalpy recovery. It is revealed that using the benchmark mono-ethanolamine (MEA) absorbent 1.62 GJ/tonne CO2 could be harvested though process modification and multiple heat extraction, enabling a high energy recovery efficiency of 82%, whilst maintaining 90% absorption efficiency and low heat requirement of 2.6 GJ/tonne CO2. Integration of REHA with CO2 capture process enables an appreciable cost of CO2 avoided decreased from $63.5/tonne to $54/tonne CO2 (16% reduction) at a heat price of $7/GJ and 5-months heat supply. The economic viability of REHA process is anticipated to be further promoted with the rise of heating price and increasing demand of space heating.

Performance and mechanism of the functional ionic liquid absorbent with the self-extraction property for CO2 capture

Regarding the bottleneck of high regeneration consumption for the amine absorbents, it was innovatively proposed in this work to construct a novel functional ionic liquid absorbent (3-Dibutylamino-propylamine-imidazole, [DBAPAH][Im]) with the self-extraction property for CO2 capture. The solvent changed from liquid-liquid two-phase to homogeneous as absorption loading increased, and it returned to a two-phase after desorption. The absorption loading of [DBAPAH][Im]-H2O solution for CO2 capture was 1.49 mol mol−1, and its regeneration efficiency was found to be 92.09% for the first regeneration and remained at 81.34% even after six cycles with a low regeneration temperature of 98 °C. It was found that this ionic liquid featured a reversible polarity, for which the polarity of [DBAPAH][Im] was much lower than that of water before absorption. The solvent changed from liquid-liquid phase to homogeneous as absorption loading increased because the polarity of the carbamate product and the Van der Waals interaction between carbamate and water were all increased. After desorption, the ionic liquid resumed with the low polarity and was not miscible in water to form an organic extraction phase, which promoted the rapid separation of the ionic liquid from the main solution and finally achieved the purpose of low temperature regeneration. Due to the coordination between cations and ions, the desorption free energy of the products formed by [DBAPAH][Im] and CO2 was very low (7.56 kJ mol−1). Furthermore, the energy consumption was estimated as 1.83 GJ t−1 CO2, which was much lower than that of benchmark monoethanolamine (MEA; 3.8 GJ t−1 CO2), and finally achieve the purpose of low regeneration temperature and low energy consumption regeneration.

Kinetics of novel non-corrosive amino functionalized ionic liquid organic solution for CO2 capture

Extensive energy consumption is a challenge for developing industrial carbon capture absorbents. A novel amino functionalized ionic liquid (AFIL) organic solution, tetraethylene pentamine 5-amino-4-imidazolecarboxamide/n-propanol/ethylene glycol ([TEPAH][AICA]/NPA/EG), is considered as a promising absorbent due to its high CO2 absorption capacity and low energy consumption. However, its industry application potential still needs to be further evaluated for carbon capture process. In this work, thermodynamics, kinetics and corrosive behavior of [TEPAH][AICA]/NPA/EG solution were investigated. The regeneration energy consumption was 2.30 GJ⋅t−1 CO2, which was 39.5% lower than the benchmark monoethanolamine (MEA) solution. The mass transfer reaction kinetic model was established, showing that the reaction between CO2 and [TEPAH][AICA]/NPA/EG solution followed fast pseudo-first-order. The enhancement factor and reaction rate constant increased with the increase of absorption temperature, while they showed a decreasing trend with the increase of absorption loading. The relationship between the second-order rate constant and temperature was expressed as k2=7.2075×108exp-3093.5T. The activation energy was 25.72 kJ·mol−1. During absorption process, the dominant mass transfer resistance gradually changed from gas phase to liquid phase. In addition, the absorbent presented non-corrosive behavior after saturated absorption, which was superior than the MEA absorbent for storage and transportation in the carbon capture technology. To be concluded, the above results showed that the [TEPAH][AICA]/NPA/EG solution owned great potential for future industrial application.

Comparative mass transfer performance of CO2 absorption using highly-concentrated AMP-PZ-MEA ternary amines solvent

Mass transfer performance of CO2 absorption is based on selecting an effective amine solvent, hence, an examination of the overall mass transfer coefficient (KGav) and CO2 removal efficiency, is significant for obtaining the most favorable CO2 capture performance. This study compared KGav and CO2 removal efficiency of the highly concentrated ternary amines solvent at various concentrations with the benchmark monoethanolamine (MEA) in a laboratory scale CO2 absorption packed-column. The six blends of 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ), and MEA are formulated as ternary solvents at high PZ/AMP molar ratio (1.25–3.75) and total amine concentration (6M and 7M). Be noted that the solvent precipitation was not observed in this study. The absorption experiment was operated at 303 K temperature, 12% CO2 by volume, and CO2 loading of 0.25 mol CO2/mol amine. The experimental results showed that KGav and CO2 removal efficiency for AMP-PZ-MEA and MEA solvents increased as total amine concentration increased. Also, KGav and CO2 removal efficiency of the PZ-AMP-MEA solvent are greater than those of 5M MEA. An increase of PZ/AMP molar ratio had a positive influence on the absorption performance for ternary amines. In comparison with the benchmark 5M MEA, all the studied AMP-PZ-MEA solvents showed an outperformance. The two suggested formulae, which are 0.95:3.55:1.5 (6M) and 0.95:3.55:2.5 (7M), possessed approximately 1.5 and 2.5 times higher KGav and 17.34% and 17.63% greater CO2 removal efficiency compared with the benchmark 5M MEA.

Machine learning-driven assessment of relationship between activator properties in phase change solvent and its absorption performance for CO2 capture

Amine-based phase change solvents are recognized as an energy saving alternative to the benchmark solvent, mono-ethanolamine (MEA), for CO2 capture owing to their unique phase separation behavior and low energy penalty. However, screening of the phase change solvents is labor intensive via the experimental analysis. To address this issue, this work intends to develop a machine learning-driven assessment system to screen promising phase change solvents via exploring the relationship between activator properties and absorption performance. Based on the machine learning and quantum calculation, the relationships between 11 properties of 30 activators and 6 performance parameters were observed. Subsequently, the sensitive analysis was conducted via focusing on 5 key activator properties, such as alkalinity, hydrophobicity, molar refraction index, molar volume and the ADCH charge of N atom. Based on the proposed assessment system, 4 phase change solvents with potential excellent performance were screened, and kinetics and thermodynamics were further verified by experimental results. Among them, the regenerative heat of diethylenetriamine/N,N-Diethylethanolamine (DETA/DEEA) was around 2.44 GJ t−1, which is ∼ 34 % lower than that of benchmark MEA solvent. It is believed that the assessment system developed in this work can deepen the understanding of screening and practical application of phase change solvents.

Techno-economic assessment of enzymatic CO2 capture in hollow fiber membrane contactors with immobilized carbonic anhydrase

CO2 capture technologies to reduce greenhouse gas emissions are widely studied and techno-economic assessments (TEA) are needed to assess their feasibility in industrial applications. The current benchmark technology is using amine-based solvents, such as monoethanolamine (MEA), in packed-bed columns because of their high CO2 selectivity and fast absorption rate. However, the capture process is energy extensive and costly, so an alternative must be found. In the present study, a TEA is performed to analyze a novel enzymatic capture process in a 685 MWe coal-fired power plant. Hollow fiber membrane contactors are used as an alternative to packed-bed columns due to their compactness, and ease of operation and to scale up. The carbonic anhydrase enzyme promotes the hydration of CO2 in water in the presence of a buffer and is immobilized on the membranes to increase its stability under harsh industrial conditions. The use of this benign solvent reduces the energy consumed for its regeneration and is non-corrosive. It was found that the energy consumption of the capture and compression unit was reduced by 43%, its capital cost by 31% and OPEX by 28% compared to a benchmark MEA process for a 90% capture rate. A capture cost of 38.5 $/t CO2 was estimated, representing a 44% reduction over the MEA process. To optimize the process, this study also focuses on sensitive parameters that have a significant impact on the capture cost. Particular attention was made toward the cost, lifetime and dimensions of the membranes, gas and liquid velocity, and the enzyme lifetime to be competitive with existing technologies. Overall, enzymatic CO2 capture in membrane contactors is a green, energy-efficient, non-toxic, and low-cost technology that holds promise for industrial applications.

Regulatory mechanism of a novel non-aqueous absorbent for CO2 capture using 2-amino-2-methyl-1-propanol: Low viscosity and energy efficient

The large-scale deployment of non-aqueous amine solution for carbon dioxide (CO2) capture is mainly limited by its high viscosity, even insoluble substances in saturated solution, which may result in equipment fouling and pipeline blockage. To avoid this problem, the polyamine 1,5-diamino-2-methyl-pentane (DA2MP) was screened as the main absorbent to ensure the high absorption load. While 2-amino-2-methyl-1-propanol (AMP) was used as the regulator to reduce the viscosity and eliminate insoluble substances, which dissolved in n-propanol (PrOH) to from the novel non-aqueous absorbent for CO2 capture. The CO2 absorption load of the novel absorbent was 0.95 mol·mol−1, and the viscosity of saturated solution was only 15.00 mPa·s, remarkably lower than that of the solution without AMP regulation. The solution maintained 97% of its initial CO2 absorption capacity after fourth regeneration cycle. The regulation mechanism was investigated using 13C nuclear magnetic resonance (NMR) and quantum chemical calculations. It was proved that a strong and dense hydrogen bond network between DA2MP-carbamates was formed due to the self-deprotonation process, leading to insoluble products in the saturated DA2MP/PrOH solution. Through AMP regulation, there was another type of DA2MP-carbamates deprotonated by AMP formed in the solution with less hydrogen bond network, which could further react with PrOH to produce alkyl carbonates, achieving the elimination of insoluble products and reducing viscosity. Overall, the total regeneration energy consumption was 1.86 GJ·ton−1 CO2, only 50.27% of that of the benchmark monoethanolamine (MEA)-based solution, which would be a promising candidate for CO2 capture.

Thermodynamics and kinetics of novel amino functionalized ionic liquid organic solvent for CO2 capture

The main disadvantage of commercial absorption solution for CO2 capture from flue gas is extensive energy consumption. A novel amino-functionalized ionic liquid (AFIL) organic solution of tetraethylene pentamine 2-methylimidazolium/N-propanol/ethylene glycol ([TEPAH][2-MI]/NPA/EG) is considered as a promising candidate absorption system because of its efficient CO2 capture performance and low energy consumption. The thermodynamics and kinetics studies are very essential for evaluating the absorbent and its potential of future practical industrial application. In this work, the performance in these two aspects of [TEPAH][2-MI]/NPA/EG solution were investigated. The regeneration energy consumption was 2.98 GJ·t−1 CO2, which was 21.6% lower than that of benchmark monoethanolamine (MEA) aqueous solution, and the energy saving advantage was embodied in sensible heat and latent heat. Kinetic analysis showed that chemical reaction of CO2 absorption into [TEPAH][2-MI]/NPA/EG solution took place in the pseudo-first-order reaction. The reaction rate constant and enhancement factor increased with the increase of absorption temperature, while those showed a decreasing trend with the increase of absorption loading. The relation between the second-order rate constant and temperature was expressed as k2=5.6192×108exp-3111.6T, and the activation energy was further calculated as 25.87 kJ·mol−1. Compared with those of MEA and several traditional ionic liquid solutions, these parameters indicated a stronger reaction ability of the novel system. Moreover, the mass transfer resistance of gas and liquid phase changed constantly during the absorption process, and the dominant role of mass transfer resistance gradually changed from the gas phase to liquid phase. The thermodynamics and kinetics of CO2 capture revealed that the [TEPAH][2-MI]/NPA/EG solution had an excellent application potential in the future.

Investigation into simulating Selective Exhaust Gas Recirculation and varying Pressurized Hot Water temperature on the performance of the Pilot-scale Advanced CO2 Capture Plant with 40 wt(%) MEA

The concentration of an aqueous solution of amine affects the solvent regeneration energy requirement in the Post-combustion CO2 Capture (PCC) process. Therefore, this study investigates the performance of the impact of Selective Exhaust Gas Recirculation (S-EGR) under the influence of 40 wt(%) MEA i.e. 10 % above the benchmark Monoethanolamine (MEA) concentration and at 90 % CO2 capture efficiency due to its potential to reduce the Normalized Specific Reboiler Duty (N-SRD) of the CO2 capture process. The experimental research work was carried out at the United Kingdom Carbon Capture Storage Research Centre - Pilot-scale Advanced CO2 Capture Technology (UKCCSRC-PACT) National Core Facility, UK. The S-EGR was proposed as a means of CO2 enhancement at the inlet of the absorber column to expedite the driving force of CO2 absorption and consequently reduce the N-SRD. CO2 concentrations from 5.0 to 9.9 vol(%) of CO2 were studied. Also, this experiment studied the influence of the Pressurized Hot Water (PHW) inlet temperature at the reboiler on the performance of the CO2 capture process that includes the CO2 recovery rate, CO2 loadings and N-SRD of the Solvent-based CO2 Capture Plant (SCCP) in order to study the variation of N-SRD with varying reboiler thermal inlet temperature at 9.0 vol(%) CO2.It is found that a pilot-scale CO2 capture process under the influence of simulated S-EGR reduces the N-SRD by 25.1 % under the test condition at 6.6 vol(%) CO2. This test condition was observed to have lower N-SRD as with regards to the other tests with different CO2 concentrations, below and above which the N-SRD begins to lose its value. It was also established that within the boundary of the process conditions used in these tests, the impact of the PHW temperature on the CO2 capture efficiency increases with increasing the PHW temperature, but at the detriment of N-SRD, which begins to increase above 125 °C despite more CO2 being captured.

Reducing the energy penalty and corrosion of carbon dioxide capture using a novel nonaqueous monoethanolamine-based biphasic solvent

To advance carbon dioxide (CO2) capture technology by simultaneously reducing the energy penalty and mitigating equipment corrosion, a novel nonaqueous biphasic solvent comprising monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), dimethyl sulfoxide (DMSO), and N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) was proposed for CO2 capture in this study. The performance testing results demonstrated that the MEA-AMP-DMSO-PMDETA (M-A-D-P) biphasic solvent with the optimal composition could realize a high CO2 loading of 0.88 mol·mol−1 and that its rich phase stored 95.3% of the absorbed CO2 but constituted only 56.8% of the total volume. 13C NMR analysis and quantum chemical calculations showed that both MEA and AMP could absorb CO2 to form carbamate and carbamic acid species, with the latter being the dominant reaction product. Since the products were polar and could form hydrogen bonds with polar DMSO, the two had satisfactory mutual solubility, while less polar PMDETA was isolated, thereby leading to a phase change. After phase separation, only the CO2-rich phase required regeneration. Consequently, M-A-D-P significantly reduced the sensible heat and vaporization heat by 63.1% and 94.8%, respectively, compared to the benchmark MEA solution. Moreover, the results of the corrosion test demonstrated that M-A-D-P was virtually noncorrosive to carbon steel; thus, it clearly outperformed the MEA solution. Therefore, the novel M-A-D-P biphasic solvent may be a promising candidate for advancing energy-efficient and noncorrosive CO2 capture.

Novel biphasic amino-functionalized ionic liquid solvent for CO2 capture: kinetics and regeneration heat duty.

Amino-functionalized ionic liquid biphasic solvents present excellent absorption capacity, regeneration ability, and energy consumption savings, which make them a possible candidate for CO2 capture. The kinetics and regeneration heat duty of the [TETAH][Lys]-ethanol-water system capturing CO2 were investigated in this work. The mass transfer and kinetic parameters, including the overall reaction rate constant (kov), the reaction rate constant (k2), and the enhancement factor (E), were assessed at diverse concentrations and temperatures. At 303.15K, the k2 of CO2 capture into the [TETAH][Lys]-ethanol-water solution was 58,907.30m3kmol-1s-1. The Arrhenius equation was introduced to evaluate the relations between k2 and the reaction temperature, which can be presented as [Formula: see text] The regeneration heat duty of the novel biphasic solvent was 35.5 and 62.39% lower than those of [TETAH][Lys]-water and the benchmark monoethanolamine solution, respectively. An efficient absorption performance and lower energy requirement indicate the great potential for this application.

2-Amino-2-methyl-1-propanol based non-aqueous absorbent for energy-efficient and non-corrosive carbon dioxide capture

The large-scale deployment of carbon dioxide (CO2) capture using aqueous amines is mainly limited by its intensive energy penalty. In this regard, non-aqueous amine solutions have high energy-saving potential because organics have lower heat capacity and vaporization enthalpy than water. In this study, 2-amino-2-methyl-1-propanol (AMP) coupled with activators in an inert organic solvent (N-methyl pyrrolidone, NMP) is proposed for energy-efficient CO2 capture. The relationships between activator properties and CO2 capture performance, such as absorption capacity, regeneration efficiency, and corrosion behavior, were investigated. The results showed that the non-aqueous AMP-AEEA (2-(2-aminoethylamino)ethanol)-NMP solution not only possessed high CO2 capacity (1.65 mol·kg−1 solution) but also retained nearly 90% of its initial CO2 capacity after the 4th cycle of regeneration. Moreover, it presented a non-corrosive behavior after saturated absorption, clearly showing its superiority over the benchmark monoethanolamine (MEA) solution. The 13C nuclear magnetic resonance (NMR) spectra provided evidence of CO2 reacting with AMP-AEEA in NMP to form carbamates, which could be easily regenerated under thermal desorption. The specific solvent loss was 0.14 kg⋅kg−1 CO2 and the total heat duty of AMP-AEEA-NMP solution was only about half that of the MEA solution, which can be attributed to the absence of water and properties of the inert organic solvent. With the perfect CO2 capture performance, non-corrosive behavior, and significant reduction of energy consumption, the novel solution is a promising candidate for CO2 capture.

Energy harvesting from amine-based CO2 capture: proof-of-concept based on mono-ethanolamine

Amine-based processes are the leading technology for CO2 capture, but their commercial deployment is hindered by their large energy requirement. In practice, the energy consumption of this CO2 capture process is a result of an inability to offset the energy required for CO2 desorption against the enthalpy released in CO2 absorption. Here, we propose a metal-mediated CO2-regenerative amine-based battery (CRAB) to directly convert the CO2-reaction enthalpy into electrical energy. Using the benchmark mono-ethanolamine (MEA) absorbent, we developed and validated a CRAB process model that is used to predict the energy harvesting performance. We then harvested an electrical energy of 8.3 kJe/mol CO2 from the lab-scale flow battery, demonstrating the proof-of-concept of energy harvesting from amine-based CO2 capture. Techno-economic analysis indicates that the CRAB energy harvesting system improved the power generation efficiency by 1.75% and decreased the CO2 avoided cost when integrated with a coal-fired power station, suggesting its potential to improve the techno-economic competitiveness of amine-based CO2 capture process.

Biphasic solvent for CO2 capture: Amine property-performance and heat duty relationship

The main issue related to the deployment of the absorption based technology for CO2 capture is the intensive energy penalty. Biphasic solvent is regarded as a promising candidate for CO2 capture due to its potential in significant reduction of the energy consumption. However, currently, the development of biphasic solvents relies on the intensity of solvent screening work. To address this issue, this work investigated the relationships between the solvent properties and CO2 capture performance such as absorption capacity, phase separation behavior, kinetics, and thermodynamics. Ten primary/secondary amines and eight tertiary amines with different alkalinity (pKa) and hydrophobicity (Log P) were used as the main components of the biphasic solvent. Experimental results revealed that the tertiary amine’s alkalinity determines the absorption capacity of the biphasic solvent. The maximum CO2 absorption capacity was achieved by the tested biphasic solvent with a tertiary amine of a pKa around 9.8. Compared with the tertiary amine, the primary amine’s hydrophobicity was more sensible to the phase separation behavior of the solvent. The low Log P value of the primary amine and the high Log P value of the tertiary amine befitted the phase separation. Kinetic analysis indicate that the total mass transfer resistance of the rich solution decreased with the increase in the Log P value of the tertiary amine. Interestingly, the highest enhancement factor was achieved by the tertiary amine (2-(diethylamino)ethanol) with the pKa of 9.79. Further increase of the tertiary amine’s pKa decreased the enhancement factor of the biphasic solvent. This was attributed to the limitation of mass transfer of tertiary amine from the upper phase to lower phase. Furthermore, thermodynamic analysis showed that the sensible heat and the latent heat of the solvents decreased and increased, respectively, with the increase of log P value of the tertiary amines. The lowest reaction enthalpy and heat duty of the tested biphasic solvents were 45.8% and 52% lower than those of the benchmark monoethanolamine solution, respectively. Overall, compared with the primary amine, the selection of the tertiary amine is more important to achieve a great performance for CO2 capture. Therefore, the tertiary amine with a moderate pKa and Log P is beneficial to achieve a high absorption capacity, fast absorption rate, and low heat duty of the biphasic solvent.

Kinetics, Thermodynamics, and Mechanism of a Novel Biphasic Solvent for CO2 Capture from Flue Gas.

The main issue related to the deployment of the amine-based absorption process for CO2 capture from flue gas is its intensive energy penalty. Therefore, this study screened a novel biphasic solvent, comprising a primary amine e.g., triethylenetetramine (TETA) and a tertiary amine e.g., N, N-dimethylcyclohexylamine (DMCA), to reduce the energy consumption. The TETA-DMCA blend exhibited high cyclic capacity of CO2 absorption, favorable phase separation behavior, and low regeneration heat. Kinetic analysis showed that the gas- and liquid-side mass transfer resistances were comparable in the lean solution of TETA-DMCA at 40 °C, whereas the liquid-side mass transfer resistance became dominant in the rich solution. The rate of CO2 absorption into TETA-DMCA (4 M, 1:3) solution was comparable to 5 M benchmark monoethanolamine (MEA) solution. Based on a preliminary estimation, the regeneration heat with TETA-DMCA could be reduced by approximately 40% compared with that of MEA. 13C NMR analysis revealed that the CO2 absorption into TETA-DMCA was initiated by the reaction between CO2 and TETA via the zwitterion mechanism, and DMCA served as a CO2 sinker to regenerate TETA, resulting in the transfer of DMCA from the upper to lower phase. The proposed TETA-DMCA solvent may be a suitable candidate for CO2 capture.

Study of the Post-combustion CO2 Capture Applied to Conventional and Partial Oxy-fuel Cement Plants

The present work was focused on the application in the cement industry of the post-combustion CO2 capture technology using amine-based chemical absorption. Besides conventional conditions, investigations were performed on a concept called “partial oxy-fuel combustion” applied to cement kilns leading to more CO2-concentrated flue gas (yCO2 up to 60%) and allowing to reduce the solvent regeneration energy consumption. The purpose of the study was to highlight and evaluate this reduction. Firstly, the performances of several solvents were evaluated thanks to screening tests at lab (results with a cables-bundle contactor) and micro-pilot (absorption-regeneration unit) scales considering different CO2 contents (yCO2,in = 20-60 vol.%). Simple and blended solvents were tested in such conditions, such as primary and secondary alkanolamines (benchmark Monoethanolamine (MEA), Diethanolamine (DEA) and cyclical di-amine (Piperazine (PZ)). It was shown that the use of activated solutions (such as DEA 30 wt.% + PZ 5 wt.%) presented particularly high absorption performances both in conventional and high CO2 contents conditions. Secondly, Aspen HysysTM simulations were carried out considering cement plant flue gas. For MEA 30 wt.% an increase of yCO2 from 20% to 44% leads to a 26% decrease of the regeneration energy (from 3.36 to 2.48 GJ/tCO2), which is clearly encouraging. As perspectives, new absorption-regeneration tests at micro-pilot scale and simulations will be performed with other solvents in order to have a more global evaluation of the interest of partial oxy-fuel conditions for the cement industry.

Experimental Investigation of the Absorption, Phase Transition, and Desorption Behavior of Biphasic Solvent Blends for Postcombustion CO2 Capture

Aqueous biphasic solvent blends consisting of diethylenetriamine (DETA) and a tertiary amine, N,N,N’,N”,N”-pentamethyldiethylenetriamine (PMDETA) or bis[2-(N,N-dimethylamino)ethyl] ether (BDMAEE), were experimentally assessed. Results revealed that the composition of solvent blends greatly affected the CO2 loading capacity and dual-phase transition behavior. A speciation analysis of dual liquid phases suggested that CO2 absorption was a two-stage process, in which CO2 reacted with DETA initially, followed by the protonation of PMDETA or BDMAEE and the production of HCO3−/CO32− species lately. Rates of CO2 absorption and pressures of CO2 desorption were also measured for the selected solvent blends and compared with the benchmark monoethanolamine solvent.

Kinetic performance of CO2 absorption into a potassium carbonate solution promoted with the enzyme carbonic anhydrase: Comparison with a monoethanolamine solution

Development of enzyme-mediated solvents are regarded as a potential option to overcome the energy use disadvantages associated with the benchmark monoethanolamine (MEA) solvent for post-combustion CO2 capture. In this work, the kinetics of CO2 absorption into a 20wt% potassium carbonate (PC) solution promoted with the enzyme carbonic anhydrase (CA) was investigated using a stirred tank reactor. Experimental results showed no noticeable change in the intrinsic activity of the CA enzyme with increasing CO2 loading in PC solution. A rate-based mass transfer analysis was conducted using the enzymatic kinetics measured, and results revealed that in a packed-bed column, the CO2 absorption rates into a lean and rich PC solution with 3gL−1 CA were 50% lower and 2.2 times higher, respectively, than those into their 5M MEA counterparts. The liquid-phase mass transfer resistance was dominant for both PC- and MEA-based systems. Modeling results revealed the effective packing volume of the absorber with PC in the presence of 10gL−1 CA was only slightly larger than that with MEA for post-combustion CO2 capture.

Aqueous hydrazine as a promising candidate for capturing carbon dioxide

Hydrazine, which is the simplest diamine, was investigated for its viability as a sorbent for carbon dioxide (CO2) capture from flue gas using lab scale experiments. It has a high CO2 absorption capacity due to its low molecular weight. The overall mass transfer coefficient of aqueous hydrazine (32wt%) is about 2.9 times higher than that of the benchmark monoethanolamine (MEA, 30wt%), indicating that the absorption rate of CO2 in aqueous hydrazine is remarkably fast. Furthermore, the cyclic capacity of aqueous hydrazine is comparable to that of MEA. Aqueous hydrazine has demonstrated the ability to capture and release CO2 for three cycles without changing its absorption capacity. In addition, aqueous hydrazine does not show any indication of thermal degradation up to 90°C. These advantages could lead to a substantial reduction of the cost of electricity, making aqueous hydrazine a promising new sorbent for post-combustion CO2 capture applications.