Solvent Regeneration Research Articles

Experimental and computational study of the thermal degradation of primary amines used in CO2 capture

CO2 loaded amine polymerizes during solvent regeneration at temperatures above 100 °C, resulting in the deterioration of solvent performance. Herein, five primary amines were heated to 120, 135 and 150 °C with CO2 loading of 0.4C/N to study thermal degradation. It was found that 2-amine-1-butanol showed the greatest amine loss of 38.5 % after heating to 135 °C for 672 hrs while 2-amino-2-methyl-1-propanol was most stable with amine loss of 17.4 % under the same conditions. The degradation products were identified and the reaction pathway was studied through density functional theory (DFT) calculation. Furthermore, the transition state for ring closure and opening reactions was analyzed. The ring closure reaction to form oxazolidinones had a higher energy barrier, showing that it was the limiting step. This is further supported by the good agreement with experimental results. The structure–activity relationship showed the strong steric hindrance effect and the methyl group at β-carbon improved the amine stability.

Biphasic solvents based on dual-functionalized ionic liquid for enhanced post-combustion CO2 capture and corrosion inhibition during the absorption process

To reduce the energy consumption for solvent regeneration and mitigate the corrosiveness of saturated solvents, dual-functionalized ionic liquid (IL) [DMAPA][TZ] was synthesized as a primary absorbent, and mixed with a phase separation accelerator poly (ethylene glycol) dimethyl ether (NHD) or propylene carbonate (PC) as biphasic solvents, to achieve high efficiency, energy savings, and corrosion inhibition of post-combustion CO2 capture. The results demonstrated a transition from a homogeneous solvent to a biphasic system upon CO2 absorption, with the majority of CO2 being concentrated in the rich phase, which is related to the formation of hydrogen bonds. Molecular dynamics analysis showed that interaction between the IL and PC is significantly stronger than that with NHD, resulting in a reduced absorption capacity of IL-PC relative to IL-NHD, while NHD effectively suppressed the formation of HCO3−/CO32−. At 373 K, both solvents exhibited efficient regeneration of their respective rich phases within 10 min. The calculated absorption enthalpies for IL-NHD and IL-PC are remarkably low at 0.662 and 0.772 GJ·t−1, respectively, and the regeneration energy consumption of IL-NHD was lower to 1.387 GJ·t−1. Notably, the phase separation accelerator exerts a significant influence on the phase-transition behavior and absorption products of biphasic solvents. Furthermore, ILs effectively inhibited corrosion through the adsorption-passivation mechanism; specifically, the corrosion rate of the CO2-rich phase in IL-NHD relative to 20# carbon steel was only 0.1896 mpy, which is only 1/865 of the rate of the saturated 5 M MEA solution.

Analysis and insights of the second-generation ternary AMP-PZ-MEA solvents for post-combustion carbon capture: Absorption-regeneration performance

This work comprehensively investigates absorption and regeneration performance of the second-generation AMP-PZ-MEA in comparison with the first-generation AMP-PZ-MEA, the benchmark 5 M MEA, and the conventional MEA at the same amine concentration. The performance indicators include CO2 absorption capacity, mass transfer coefficient, CO2 removal percentage, amount of desorbed CO2, initial CO2 desorption rate, and regeneration heat duty. Both 6 M (i.e., 2:2.5:1.5, 1.3:3.2:1.5, and 0.95:3.55:1.5) and 7 M (i.e., 2:2.5:2.5, 1.3:3.2:2.5, and 0.95:3.55:2.5) second-generation blends show more promising overall absorption and regeneration performance than 5 M, 6 M, and 7 M MEA. In comparison with the first-generation blend, 6 M and 7 M second-generation blends deliver more favorable mass transfer rate. Interestingly, an increase of PZ:AMP molar ratio accelerates mass transfer and absorption capacity but unfavorably affects solvent regeneration. Also, high viscosity of the second-generation 7 M blend (especially, at its equilibrium CO2 loading) retards the solvent regeneration. The key success for a formulation of AMP-PZ-MEA is appropriate PZ:AMP molar ratio and total amine concentration. Too high and too low PZ:AMP molar ratio lead to (i) solvent precipitation and (ii) imbalance of absorption and regeneration performance. Three standouts are recommended. 2.5:0.5:3 is attractive due to its low regeneration heat duty (42.1% lower than that of 5 M MEA). In terms of mass transfer coefficient, 0.95:3.55:1.5 shows 148.6% higher than 5 M MEA. 2:2.5:1.5 is also favorable according its high mass transfer coefficient (91.3% greater respecting 5 M MEA) and low regeneration heat duty (16.3% less than 5 M MEA).

Simulation Process for Allyl Alcohol Production via Deoxydehydration of Glycerol

A process for the deoxydehydration (DODH) of glycerol to allyl alcohol in 2-hexanol as solvent was modelled with Aspen Plus. Experimental results for the DODH reaction, the liquid vapour equilibria and the catalytic hydrogenation were employed for the development of the model. The whole process consists of four subsystems: allyl alcohol production (S1), solvent recovery (S2), allyl alcohol purification (S3) and solvent regeneration (S4). Based on the results of the process model, allyl alcohol with 96% yield and a purity of 99.99% with product loss of only 0.2% was obtained. The optimisation of the energy consumption through an integrated heat exchange network resulted in a net primary energy input of 863.5 kW, which corresponded to a carbon footprint of 1.89 kgCO2/kgAllylOH.

A new neodymium complex on renewable magnetic biochar nanoparticles as an environmentally friendly, recyclable and efficient nanocatalyst in the homoselective synthesis of tetrazoles.

Inexpensive, stable, selective, and recyclable nanocatalysts, waste regeneration, and utilization of safe and available solvents are of interest and important factors in laboratory science and industrial applications of green chemistry. Therefore, herein, biochar nanoparticles (BNPs) were synthesized through chicken manure pyrolysis as a novel method for waste recycling. Then, in order to improve their recyclability, the obtained BNPs were magnetized using magnetic nickel nanoparticles. Then, the surface of the biochar magnetic nanoparticles (BMNPs) was modified by (3-chloropropyl)trimethoxysilane (3-CPTMS) and further a novel neodymium Schiff-base complex was immobilized on the surface of the modified BMNPs, denoted as Nd-Schiff-base@BMNPs. The obtained supported neodymium complex was used as a practical, selective, biocompatible, commercial, and reusable heterogeneous nanocatalyst. The biochar support of this nanocatalyst was formed from pyrolysis of chicken manure; therefore, it is cheap, economically viable, green and also compatible with the principles of green chemistry. Nd-Schiff-base@BMNPs acts selectively in organic reactions and also it can easily be recovered using an external magnet and reused, which is compatible with the principles of green chemistry. This nanocatalyst was characterized by wavelength-dispersive X-ray spectroscopy (WDX), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma (ICP), and N2 adsorption-desorption (BET method) techniques. In the next step, the catalytic utilization of Nd-Schiff-base@BMNPs was investigated in the homoselective synthesis of 5-substituted 1H-tetrazole compounds from [3 + 2] cycloaddition of sodium azide (NaN3) and organo-nitriles in PEG-400 as a green solvent. Utilizing PEG-400 as a solvent offers various advantages, e.g. cheap, readily available, and environmentally friendly solvent as well as rapid separation and high purity of products. Therefore, this work is fully compatible with the principles of green chemistry.

A TECHNICAL AND ECONOMIC COMPARISON OF CO2 REMOVAL TECHNOLOGIES IN AMMONIA PRODUCTION PLANTS

The utilization of natural gas as a primary feedstock in ammonia production has resulted in significant carbon dioxide (CO2) emissions, raising environmental concerns. Consequently, several technologies have been developed to capture and remove carbon dioxide. In this study, a comparison was conducted between two CO2 removal technologies (Amine and Benfield) in an Ammonia production plant. The evaluation was performed using rate-based modelling techniques in Aspen Plus software. A base case simulation was built and validated using figures obtained from various literature studies. Optimization and sensitivity analyses were conducted to determine optimal operating conditions. The optimized parameters were used to perform an economic analysis of both technologies based on the energy consumption, solvent regeneration efficiency, and CO2 removal efficiency. The results obtained from the comparison showed that the amine technology was more economical than the Benfield technology in terms of cost and plant efficiency. The economic analysis revealed that the amine technology had a lower Net Present value, and a shorter payback period compared to the Benfield technology. Overall, this study provides insight into the economic and operational considerations of CO2 removal technologies in ammonia production plants and recommends the use of amine technology as the preferred technology for CO2 removal in ammonia production plants.

A Two-Dimensional Transport Model of Bipolar Membrane Electrodialysis for the Electro-Regeneration of Carbon Capture Solvents

Bipolar membrane electrodialysis (BPMED) is a promising technology that uses an electric field to split water into H+ and OH- ions. A repeating stack of cation selective, anion selective, and bipolar membranes are placed between two electrodes, creating a repeating pattern of acid, base, and diluting flow chambers. A major application of BPMED is the electrochemical solvent regeneration of capture solutions used in CO2 point source (PS) or direct air capture (DAC). Protons generated using BPMED can be used to shift the acid-base equilibria back to CO2, providing a more sustainable alternative to traditional thermal regeneration methods when integrated with renewable electricity sources. This method combines electrosynthesis and separation, producing a pure stream of CO2 for sequestration and a concentrated base stream.Despite its potential, current limitations to BPMED implementation for this application stem from a large power consumption and high membrane costs. In addition, gas bubbles in solution can cause high electrical resistances, and experimental studies of this phenomenon are challenging due to the small scale on which it occurs. To address these challenges, we present a two-dimensional model of BPMED for CO2 capture solvent recovery. This model depicts a single repeating cell triplet and was constructed using COMSOL Multiphysics version 6.1. The Navier-Stokes equations were implemented to compute a convection field, and the ionic species concentration was found by solving the Nernst-Planck equation. A source term in the concentration partial differential equations was implemented to account for ionic speciation and water splitting reactions, captured through kinetic rate expressions.Experimental validation was conducted on a PC Cell BED 1-4 recirculating batch system with a stack of seven cell pairs of PC acid 60 (anion selective), PC SK (cation selective), and PC Bip (bipolar) membranes. Good agreement between the model and experimental results across a range of conditions and variables demonstrates accuracy and robustness. The calculated pH and concentration profiles revealed that the majority of the speciation reaction takes place inside, or directly adjacent to, the bipolar membrane, including bubble nucleation. Bubbles form inside membrane pores and displace the electrolyte, greatly increasing the electrical resistance of the membrane, particularly when membrane porosity is low. However, the reaction plane location where bubbles are generated can be manipulated by increasing the channel width or reducing the applied voltage.Future research will focus on expanding to multiphase CFD simulations to investigate the effect on flow. Our two-dimensional model provides valuable insights into the complex and multifaceted nature of BPMED, offering a powerful tool for investigating small-scale processes and advancing the use of BPMED for CO2 capture solvent recovery. Figure 1

Techno-economic and environmental analysis of high temperature heat pumps integration into industrial processes: the ammonia plant and pulp mill cases

Heat pumps will play an important role in improving the performance of the industrial processes aiming to decarbonize their heating requirements. Yet, defining the best operating conditions of those devices may be a challenging task, as they are embedded in larger energy conversion systems and in direct competition with fired and electric heaters and other waste heat recovery systems. The costs of the energy inputs also influence the selection of either a heat pump or a gas boiler, which affects the overall efficiency and the incremental cost of the final solution. Thus, a systematic analysis must be applied in order to determine the best option to supply the heating requirement, without considerably impacting the operational feasibility of the overall plant. In this work, the base-case performance of two industrial applications with intensive heating demand, namely, the solvent regeneration process of a carbon capture unit and the black liquor concentration process of a kraft pulp mill, are compared to that of the scenarios in which a high temperature heat pump or a mechanical vapor recompression unit are integrated, aiming to reduce the energy consumption and the environmental impact. The benefits of the integration of a heat pump or a mechanical vapor recompression unit over a conventional reboiler and a multiple effect evaporation system are discussed in the light of thermodynamic, economic and environmental indicators. As a result, the alternative approaches remain competitive vis-à-vis the conventional solutions in terms of energy consumption and operating costs. In addition, the emissions associated to the heating applications could be reduced by 45% if a high temperature heat pump is integrated. The optimized solution using a heat pump has an overall exergy efficiency 9% higher compared to the typical configuration of the ammonia plant. In pulp mills, the integration of mechanical vapor recompression systems slightly affects the performance compared to the conventional scenario with a multiple effect evaporation system.

Energy, exergy, economic, and environmental analysis of natural gas sweetening process using lean vapor compression: a comparison study

Abstract Gas sweetening with an aqueous solution of diethanolamine is a crucial and common process in natural gas processing. However, the process, particularly in the solvent regeneration section, consumes a substantial amount of energy, significantly escalating the cost of gas. This paper presents a simulation and optimization of an existing natural gas refinery plant using a lean vapor compression method. The simulation results indicate that the current process requires 2.73 GJ/tacid gas for solvent regeneration, with exergy destruction of 14,120.59 kW in the solvent regeneration section. The total annualized cost for the current process is 11.68 M$. A modified scheme is proposed to address the issue of high energy consumption and the associated costs. The proposed scheme demonstrates significant improvements in the aforementioned parameters. Specifically, energy for solvent regeneration, exergy destruction in the solvent regeneration section, total annualized cost, and cost of gas are reduced by 16.12 %, 25.04 %, 20.97 %, and 20 % compared to the current process, respectively. These improvements enhance the thermoeconomic indexes, making the proposed scheme a viable and cost-effective alternative to the current process.

Results from pilot-scale CO[formula omitted] capture testing using 30 wt% MEA at a Waste-to-Energy facility: Optimisation through parametric analysis

Post-combustion carbon capture is a well-established technology for removing CO2 from industrial emissions. However, research is still underway to optimise the process and make it more energy efficient. The current work aims to present the results from pilot-scale (with a capacity of 1tonne CO2/day) studies of CO2 capture conducted at Amager Bakke, a Waste-to-Energy facility in Copenhagen, Denmark. The pilot operation is fully automated, and the process control structure helps achieve multiple steady states at regular intervals. In addition, the pilot is capable of several configurations which can assist in optimising the energy required for solvent regeneration. The current work discusses the base case configuration of the pilot plant by employing 30wt% MEA as the solvent. Experiments were conducted to analyse the influence of reboiler duty, solvent flow rate, and gas flow rate on the pilot’s performance. The influence of these parameters on several aspects is discussed in detail, and recommendations for the optimal operation of such plants are provided. An optimum specific reboiler duty of 3.46GJ/tonne CO2 is obtained at a solvent flow rate of 306kg/h, flue gas flow rate of 113kg/h, and reboiler duty of 17.5kW excluding heat loss.

Tailoring Chemical Absorption-Precipitation to Lower the Regeneration Energy of a CO2 Capture Solvent.

Solvent-based CO2 capture consumes significant amounts of energy for solvent regeneration. To improve energy efficiency, this study investigates CO2 fixation in a solid form through solvation, followed by ionic self-assembly-aided precipitation. Based on the hypothesis that CO3 2- ions may bind with monovalent metal ions, we introduced Na+ into an aqueous hexane-1,6-diamine solution where CO2 forms carbamate and bicarbonate. Then, Na+ ions in the solvent act as a seed for ionic self-assembly with diamine carbamate to form an intermediate ionic complex. The recurring chemical reactions lead to the formation of an ionic solid from a mixture of organic carbamate/carbonate and inorganic sodium bicarbonate (NaHCO3 ), which can be easily removed from the aqueous solvent through sedimentation or centrifugation and heated to release the captured CO2 . Mild-temperature heating of the solids at 80-150 °C causes decomposition of the solid CO2 -diamine-Na molecular aggregates and discharge of CO2 . This sorbent regeneration process requires 6.5-8.6 GJ/t CO2 . It was also found that the organic carbamate/carbonate solid, without NaHCO3 , contains a significant amount of CO2 , up to 6.2 mmol CO2 /g-sorbent, requiring as low as 2.9-5.8 GJ/t CO2 . Molecular dynamic simulations support the hypothesis of using Na+ to form relatively less stable, yet sufficiently solid, complexes for the least energy-intensive recovery of diamine solvents compared to bivalent carbonate-forming ions.

Obtaining the Enoxaparin Sodium Substance Equivalent to the Original Clexane® and Lovenox®. The Selection of Technological Parameters and Optimization of the “Greenness” of the Purification Stage

The aim of the study was to adjust and optimize the purification stage of crude enoxaparin sodium to obtain a substance equivalent to the original drugs Clexane® and Lovenox® according to the criteria specified by the FDA. The purification stage involves the reprecipitation of crude enoxaparin in methanol. Determining the ratio of solvents required for the reprecipitation is important for studying the correlation between the experimental conditions of the technological process and the structural characteristics of enoxaparin samples. In the study, the method of purification of enoxaparin sodium described in the patent was assessed, and the following variations of the MeOH:H2O solvent ratio were selected – 4:1; 2:1; 1:1. The obtained samples of enoxaparin sodium were analyzed according to the in-house specification developed on the basis of the pharmacopoeial monograph, as well as by non-pharmacopoeial methods, such as two-dimensional NMR spectroscopy (HSQC) and size exclusion chromatography (SEC) for detailed characterization of the molecule. Strategies of greening of the enoxaparin sodium purification stage by reducing the E-factor were also considered in the study. Considering the principles of “green” chemistry, the method of purification of crude enoxaparin sodium was optimized by the solvent regeneration. It was experimentally possible to demonstrate the effect of the solvent ratio at the stage of purification of crude enoxaparin on the composition, as well as on the number and distribution of oligosaccharide fractions in the molecule. Based on the results of the study, it can be concluded that the ratio of MeOH:H2O=1:1 allows obtaining samples that are closest to Clexane® and Lovenox® in terms of the molecular weight distribution profile and the composition profile. The E-factor was also reduced from 14 to 5.25 by solvent regeneration.

Fast‐Photocurable, Mechanically Robust, and Malleable Cellulosic Bio‐Thermosets Based on Hindered Urea Bond for Multifunctional Electronics

AbstractMalleable thermosets as dynamic covalent cross‐linked polymers, simultaneously possessing the advantages of thermosets and thermoplastics, have attracted considerable attention. Although several reprocessing concepts have been demonstrated, the fabrication of fast‐curing bio‐based strong and tough malleable thermosets for advanced applications in electronics remains a great challenge. Herein, a novel construction strategy of combining hindered urea bonds (HUB) and radical polymerization is developed to prepare fast‐photocurable and mechanically robust cellulose‐based malleable bio‐thermosets (CMTs). In this strategy, the functional cellulose macromonomer simultaneously has acrylate groups and HUB is first synthesized and employed as a macro‐crosslinker to react with plant oil‐based monomer to construct the malleable bio‐thermosets with “soft (plant oil‐based polymer)” and “hard (rigid cellulose)” phase architecture through the fast photocuring. The CMTs exhibit excellent flexibility and high toughness (2.89 MJ m−3), and the introduction of dynamic HUB endows the CMTs with excellent malleability and reprocessability by heating compression molding or solvent regeneration, the recovery efficiency reached 94.7%. More impressively, the CMTs can be used as substrates to fabricate CMTs/silver composite for anti‐icing or de‐icing devices, and CMTs‐based capacitive sensors for monitoring environmental humidity or human health. This work paves a new strategy to develop new‐generation fast‐photocurable mechanically robust, malleable bio‐thermosets for multifunctional electronic devices.

"Greening" of the industrial technology of enoxaparin sodium synthesis

The aim: carrying out stages of synthesis of intermediates of Enoxaparin sodium, considering the variation of synthesis parameters. Correlation analysis between the technological parameters of the synthesis and the quality of the obtained samples. Evaluation of the influence of the quality of semi-finished products on the quality of the final substance. Implementation of the principles of green chemistry in the synthesis of Enoxaparin sodium by reducing the production cycle and using the most environmentally friendly solvents and reagents. Materials and methods: samples of intermediates of the substance Enoxaparin sodium were synthesized according to the method described in the patent, as well as with a variation of the selected critical technological parameters. The obtained samples of intermediate products were analyzed according to the internal specification. In addition, an NMR-spectroscopy analysis was carried out for detailed structural characterization of Enoxaparin sodium intermediate molecules. Results: the method of synthesis of intermediates of the Enoxaparin substance proposed in the patent was evaluated and the critical parameter for the formation of the final molecule was selected, namely the reaction mass holding time. The intermediate of Enoxaparin sodium - benzethonium salt of heparin and benzyl ester of heparin were developed according to the selected parameters and the analysis of the obtained samples was carried out according to the internal ND. Taking into account the principles of green chemistry, the method of synthesis of the intermediate product - benzyl ester of heparin was optimized by solvent regeneration. Conclusions: As a result of the research, the methods of synthesis of intermediates of Enoxaparin were evaluated and the technological parameters of the synthesis of intermediates were determined, allowing to obtain a substance equivalent to the original Clexane® and Lovenox®. Evaluation of the method of synthesis of intermediate products according to the principles of green chemistry was carried out. The possibilities of greening the synthesis were analyzed. The holding time of the reaction mass of the benzethonium salt of heparin was reduced from 6 to 4 hours, and the benzyl ester of heparin from 25 to 22 hours. The E-factor indicator was reduced by regeneration of the solvent at the stage of synthesis of heparin benzyl ester

Electrification of amine-based CO2 capture utilizing heat pumps

Capturing CO2 is necessary to abate the climate crisis. Amine CO2 capture is the most mature technology but suffers from high thermal energy consumption for solvent regeneration. Heat pumps are a proven technology with which to electrify industrial processes. This study investigates an integrated heat pump system used to electrify an amine CO2 capture unit for a biogas upgrading process using aqueous monoethanolamine. The study evaluates the potential of such integrated systems through the overall energy consumption at varied stripper pressures between 0.313 to 1.813 bara and includes a techno-economic analysis to determine the levelized cost. The most optimal heat pump scenario utilizes a vacuum operated stripper at 0.513 bara and reduces the overall energy consumption by 68 % compared to a classical amine scrubbing unit. The techno-economic analysis shows that the levelized costs for biogas upgrading per MWh of produced biomethane may be reduced by up to 33 % from 47 €/MWh to 31 €/MWh by implementing heat pump electrification systems and a vacuum operated stripper compared to a scenario using natural gas.

Lipid recovery from deep eutectic solvents by polar antisolvents

Deep eutectic solvents (DES) can be a green alternative extraction technology for microalgae lipids, acting simultaneously as a pre-treatment agent and solvent. However, due to the low vapor pressure of both DES and lipid solute, the recovery of lipids and solvent regeneration remains difficult. In this study, we developed a novel strategy to separate the dissolved sunflower and model algae oil from imidazole/hexanoic acid DES by using polar antisolvents (water, methanol, and ethanol). The polarity and the amount of antisolvent influenced the lipid solubility in DES. While the water was the strongest antisolvent, the alcohols were easier to evaporate, ensuring easy DES regeneration. By adding small amounts of water and methanol, more than 90% of the lipids were recovered in the form of high-purity oils (>90%). In the case of ethanol, a large amount of ethanol was required, which diluted the solvent-rich phase and solubilized more lipids in it. Based on three repeated cycles with the selected antisolvent methanol, > 90% of the eutectic solvent could be regenerated.

Energy-efficient regeneration of amine-based solvent with environmentally friendly ionic liquid catalysts for CO2 capture

Catalytic CO2 desorption from rich amine solution is a practical approach to reducing energy consumption for amine regeneration. In this study, for the first time, the catalytic effect of environmentally friendly, imidazole series ionic liquids ([Bmim]PF6, [Bmim]BF4, [Bmim]HSO4, [Bmim]NO3, [Bmim]CH3COOH, [Bmim]Cl, [Bmim]Br, and [Bmim]I) is evaluated in terms of CO2 desorption rate, amount of CO2 released, and heat duty. Overall, the [Bmim]PF6 catalyst shows excellent catalytic activity for CO2 desorption, increasing the quantity of CO2 released by 21.35% and reducing the relative heat duty by 17.59%. In addition, the catalytic applicability of [Bmim]PF6 for secondary and tertiary amine systems was evaluated. Of note, the homogeneous [Bmim]PF6 catalyst presents good stability during 5 cycles. The catalyst/MEA (monoethanolamine) solution ratio of 3 wt% retained about 94% of the catalytic performance after five cycling tests without any reactivation step, showing the potential application of this desorption technology for CO2 capture with lower heat duty.

Catalytic desorption of CO2‐loaded solutions of diethylethanolamine using bentonite catalyst

AbstractThe absorption of CO2 gas into aqueous alkanolamine solutions is the most advanced CO2 separation technology and a key challenge in this technique is the energy‐intensive process of solvent regeneration. The tertiary amine N,N′‐diethylethanolamine (or DEEA) is a candidate CO2‐capturing solvent with potential. To improve the energy efficiency of regeneration of DEEA, several catalysts were used for desorbing CO2 from loaded solutions of DEEA (2.5 M) at T = 363 K. Desorption trials were conducted in batch mode. The initial CO2 loading varied in the 0.3–0.35 mol CO2/mol DEEA range. The performance was analyzed by calculating the rate of CO2 desorption, cyclic capacity, and reduction in sensible energy. The amount of thermal energy needed for amine regeneration was significantly lowered by using nine transition metal oxide catalysts and the hierarchy was as follows: Al2O3 < MoO3 < V2O5 < TiO2 < MnO2 < ZnO < Cr2O3 < SiO2 < ZrO2. Among the metal oxides, Al2O3 increased desorption efficiency compared to blank runs by 89%. A clay‐based powder bentonite was also used as catalyst and its efficacy was compared with the metal oxides. This cheap and easily available bentonite catalyst was tuned through simple ion‐exchange with four acids (HCl, H3PO4, HNO3, and H2SO4). Upon treatment with H2SO4, bentonite remarkably increased desorption efficiency by 100%. Furthermore, bentonite catalyst treated with sulphuric acid (denoted here as Bt/H2SO4) was characterized by Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectrometery (FTIR), X‐ray diffraction (XRD), and ammonia temperature‐programmed desorption (NH3‐TPD). In this way, a comprehensive study on catalytic desorption of DEEA was performed.

New improvement of amine-based CO2 capture processes using heat integration and optimization

The post-combustion capture process (PCCP) using amine-based solvent was the most mature and adequately researched carbon capture and storage (CCS) technology. Monoethanolamine (MEA) solvent regeneration in the stripper (desorption process) usually takes high energy consumption and a MEA make-up is required before re-entering the absorber (absorption process). To improve the CO2 capture efficiency and reduce the overall energy consumption of PCCP, four configurations (Design-1, Design-2, Design-3, Design-4) are presented, where Design-1 is denoted as the base case design. Design-2 is an extension of Design-1 by adding the side intercooler in the absorber. Design-3 is an extension of Design-2 by using internal heat integration in the stripper. Design-4 is an extension of Design-3 by adding the side interheater in the absorber. By using response surface methodology (RSM) in conjunction with central composite design (CCD), operating parameters (MEA solvent flowrate, MEA concentration, pressure) including side intercooler/side interheater locations of Design-2 to Design-4 are optimized. It is successfully validated that the side intercooler absorber could increase the CO2 capture ability by MEA solvent and the side interheater stripper with internal heat integration could effectively reduce energy consumption about 36% to 62%.

Performance and Stability of Molten Carbonate Fuel Cell Cathode Electrode Under Carbon Capture Endurance Tests

Introduction The molten carbonate fuel cell (MCFC) has emerged as one of the promising alternatives for carbon capture from industrial and power generation CO2 sources. MCFC technology is less energy-intensive compared to conventional amine scrubbing that requires a significant amount of energy (steam) for solvent regeneration process.MCFC has been commercially used for distributed power generation, however its use in carbon capture applications has been limited to development activities and a few demonstrations during the past decades. The electrochemical reactions taking place during cell operation involve the CO2 transfer from cathode to anode in the form of carbonate ions resulting in a gas stream with high CO2 concentration on the anode exhaust. Therefore, MCFC stack systems can be combined with conventional combustion-powered generators (coal and/or natural gas-based power plants) for simultaneous CO2 separation, power and hydrogen generation.CO2 capture applications will typically take in flue gas from industrial furnaces, coal and gas fired combined cycle plants as the cathode inlet gas stream having low CO2 concentrations ranging from 4% to 10% by volume and high CO2 utilization (>90%). These CO2-lean conditions may pose a challenge for attaining good mass-transfer performance and life stability, therefore innovative approaches are needed in terms of hardware design and cathode structure to achieve long-term stability.FCE has tested numerous single cells (250 cm2) and technology stacks (30 kW) under carbon capture operating conditions (4-8% CO2 in the cathode inlet as opposed to >12% in baseline MCFC systems) to understand impact of design parameters on performance, life, and to investigate design solutions for further enhancement. Figure 1 highlights the effect of cathode water content on CO2 utilization. It appears that differences exist between the ideal and measured CO2 utilizations, indicating that less CO2 is transferring from the cathode to anode than expected. This CO2 transference reduction becomes more pronounced with higher water concentration, suggesting that a species other than CO3 2- ion, likely hydroxide (OH- ion), may be generated and transported through the electrolyte matrix.This paper will review the cathode material stability and electrochemical performance under long-term carbon-capture operation. The effect of parameters such as water content, gas composition, utilization, and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed. Figure 1