Regeneration Heat Duty Research Articles

An energy-efficient cyclic amine system developed for carbon capture from both flue gas and air

High energy consumption is a major barrier to the large-scale deployment of carbon capture processes from flue gases or air (direct air capture, DAC). The non-aqueous amines reported in literature possess a high energy efficiency for CO2 capture from flue gases, they struggle with gas streams containing ultra-dilute CO2, like air, due to poor absorption kinetics. This study developed novel 2-PE (2-piperidineethanol)/APZ (Aminoethylpiperazine) based CO2 absorbents to address these problems. The experiments and MD simulation results showed that the 2-PE/APZ-based absorbents possessed a superior absorption performance both in flue gas and air. Among the developed absorbents, when 2-PE/APZ mixed with DMF (Dimethylformamide), the CO2 loading reached to 1.004 mol/mole, as the theoretical maximum. In DAC tests, 87.31 % CO2 from the air was captured in 24 h experiments. The regeneration heat duty of 2-PE/APZ/DMF decreased to 1.694 KJ/g CO2, a 55.89 % reduction compared to the benchmark 30 wt% MEA. The CO2 absorption/desorption mechanism was analysed by NMR, In-situ FT-IR, and DFT calculation. It indicated that this significant improvement in CO2 absorption performance and the reduction in energy consumption are due to the synergistic effect of 2-PE and APZ. During CO2 absorption, CO2 reacts with APZ forming APZ zwitterion rapidly, then deprotonation to the 2-PE. The formation of protonated 2-PEH+ ion pairs with APZCOO- reduces hydrogen bonds and van der Waals forces among the amine-CO2 complex, facilitating easy regeneration at mild conditions while maintaining high reactivity. The combination of theoretical and experimental results indicates that 2-PE/APZ-based absorbents can serve as a promising alternative for carbon capture from flue gas to air with low energy usage.

Effective amine solvent regeneration over NiO-modified SBA-15 catalysts for energy-saving CO2 capture

Catalytic amine regeneration can decrease the energy required for regeneration; therefore, high economic and energy efficiency can be expected for CO2 capture. These factors necessitate the development of an inexpensive and easily synthesizable catalyst that can exhibit a high desorption efficiency. When selecting a catalyst, its physicochemical properties must be considered, because they markedly affect the chemical reaction between CO2–amine–catalyst. In this study, mesoporous silica SBA-15, particularly, rod-type SBA-15, wrinkled SBA-15 (modified from rod-type SBA-15), and NiO-impregnated rod-type and wrinkled SBA-15 catalysts were investigated in terms of the CO2 desorption rate and heat duty in a CO2–rich 5 M monoethanolamine (MEA) solution at 86 ℃. The physicochemical properties of the catalysts were compared to investigate their effect on the CO2 desorption efficiency. The performance of wrinkled SBA-15 impregnated with 10 wt% NiO in a CO2–rich MEA solution was optimal, exhibiting a 12 % higher CO2 desorption rate and 19.9 % lower heat duty than the MEA solution without a catalyst. Furthermore, the stability and reproducibility of the catalysts were confirmed through repeated experiments under identical conditions. Based on the experimental results and analysis, a plausible desorption mechanism for CO2–MEA–catalyst was proposed. It is expected that the regeneration heat duty during the CO2 regeneration can be effectively reduced by a catalyst, eventually applied to the CO2 capture.

Novel tri-solvent amines absorption for flue gas CO2 capture: Efficient absorption and regeneration with low energy consumption

Blended amine scrubbing is considered as a promising alternative to the monoamine scrubbing process due to the potential for enhanced CO2 capture efficiency and reduced energy consumption. However, striking a balance between absorption rate and regeneration energy consumption in blended amine systems by establishing suitable interactions between activated amines and proton-acceptor amines remains a significant challenge. In this study, a novel blended amine system, involving tertiary amine diethanolamine (DEEA) as the main agent and several monoamines as promoters, was first proposed to achieve highly effective CO2 capture. The designed tri-solvent amine system of DEEA combined with piperazine (PZ) and 4-amino-1-methylpiperidine (PD) (denoted as DEEA + PZ + PD) exhibited exceptional CO2 loading (0.988 mol CO2/mol amine), superior cyclic capacity (0.788 mol CO2/mol amine), and reduced regeneration heat duty (2.14 GJ/t), surpassing monoethanolamine (MEA) by 79.6 %, 277 %, and decreasing by 43.7 %, respectively. Furthermore, the performance improvement mechanism of DEEA + PZ + PD was systematically elucidated, showcasing the swift CO2 absorption facilitated by PD or PZ in the initial reaction phase, and the subsequent formation of bicarbonate from PDCOO− and DEEA in the later stage, enhancing CO2 absorption capacity. The predominant reaction products, bicarbonate and unstable carbamate (PZ(COO−)2, PDCOO−), contribute to the high regeneration efficiency and minimal energy consumption during regeneration for DEEA + PZ + PD. Consequently, this facilely prepared tri-solvent amine system, characterized by high capture efficiency and low energy consumption, holds promise for achieving carbon–neutral operations in coal-fired power plants.

Sulfur Migration Enhanced Proton-Coupled Electron Transfer for Efficient CO2 Desorption with Core-Shelled C@Mn3O4.

Transforming hazardous species into active sites by ingenious material design was a promising and positive strategy to improve catalytic reactions in industrial applications. To synergistically address the issue of sluggish CO2 desorption kinetics and SO2-poisoning solvent of amine scrubbing, we propose a novel method for preparing a high-performance core-shell C@Mn3O4 catalyst for heterogeneous sulfur migration and in situ reconstruction to active -SO3H groups, and thus inducing an enhanced proton-coupled electron transfer (PCET) effect for CO2 desorption. As anticipated, the rate of CO2 desorption increases significantly, by 255%, when SO2 is introduced. On a bench scale, dynamic CO2 capture experiments reveal that the catalytic regeneration heat duty of SO2-poisoned solvent experiences a 32% reduction compared to the blank case, while the durability of the catalyst is confirmed. Thus, the enhanced PCET of C@Mn3O4, facilitated by sulfur migration and simultaneous transformation, effectively improves the SO2 resistance and regeneration efficiency of amine solvents, providing a novel route for pursuing cost-effective CO2 capture with an amine solvent.

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).

Inhibiting effect of 2-amino-2-methyl-1-propanol on gelatinous product formation in non-aqueous CO2 absorbents: Experimental study and molecular understanding

Diamines or polyamines with two or more amino groups are suitable for formulating non-aqueous absorbents (NAAs) with high CO2 loading capacity and low regeneration energy consumption. However, these two types of amines in NAAs are prone to produce insoluble gelatinous products after absorbing CO2, resulting in difficult operation of the CO2 capture system. In this study, by using 2-amino-2-methyl-1-propanol (AMP) as an inhibitor, the insoluble gelatinous products of the aminoethylethanolamine (AEEA)-N-methyl-2-pyrrolidone (NMP) (A-A-N) and 3-(methylamino)propylamine (MAPA)-NMP (M-A-N) NAAs were successfully eliminated. The experimental results showed that the AMP-regulated NAAs possessed a high absorption rate, high CO2 loading capacity, excellent desorption efficiency, and stable recyclability. The reaction mechanism of CO2 absorption and the inhibitory mechanism of AMP on the formation of gelatinous products were comprehensively elucidated. Taking the A-A-N system as a representative, AEEA reacted with CO2 to form zwitterionic protonated carbamate species (AEEACO2−(P)H+(S)), which tended to self-aggregate via hydrogen-bond interaction, resulting in the formation of insoluble gelatinous products. With the introduction of AMP, the AMP-derived products could combine easily with AEEACO2−(P)H+(S) via strong electrostatic attraction to form ion pairs, preventing the AEEACO2−(P)H+(S) molecules from self-aggregating to form insoluble gelatinous products. The regeneration heat duty of the A-A-N system was 1.89 GJ∙ton−1 CO2, which was 49.9 % lower than that of the benchmark 30 wt% MEA. Overall, introducing AMP as a gelatinous product inhibitor was beneficial for the development of NNAs with high CO2 absorption capacity and low-energy consumption.

Comprehensive investigation on carbon dioxide absorption capacity, cyclic capacity, and regeneration heat duty of blended 2–amino–2–methyl–1–propanol (AMP) and N–methyl–4–piperidinol (MPDL) solvent

This research studied blended solvent of 2–amino–2–methyl–1–propanol (AMP) and N–methyl–4–piperidinol (MPDL) at concentrations of 30% wt. (5/25, 10/20, and 15/15%wt. AMP/MPDL) and 40% wt. (10/30, 15/25, and 20/20%wt. AMP/MPDL). An increase of AMP/MPDL blended ratio favored CO2 absorption capacity, cyclic capacity, and regeneration heat duty. Additionally, an elevation of total amine concentration benefited cyclic capacity and regeneration heat duty but negatively affected CO2 absorption capacity. The sensible heat was a major contributor of the regeneration heat duty (approximately 51–61%). An increase of AMP/MPDL blended ratio and an elevation of total amine concentration considerably reduced the sensible heat. In general, the sensible heat can be largely reduced by purposely selecting the solvent with low heat capacity and high cyclic capacity. The proposed AMP–MPDL solvent showed very satisfactory absorption–regeneration performance with 26–48% higher CO2 absorption capacity, 3.3–4.6 times larger cyclic capacity, and 60–68% lower regeneration heat duty than those of 30% wt. MEA.

An investigation on the effects of organic additives on CO2 capture performance of Na2CO3 solution

AbstractBACKGROUNDThe large‐scale practical application of CO2 capture using carbonate solutions is mainly limited by their low CO2 absorption rate. In view of this, it is feasible to improve CO2 capture performance of carbonate solution by adding additives. In this paper, low‐cost sodium carbonate (Na2CO3) solution was selected as the main CO2 absorbent, and the effects of different organic additives on CO2 capture performance of Na2CO3 solutions were systematically investigated.RESULTSThe results showed that 0.04 mol/L tetrabutylammonium bromide (TBAB) could achieve a better enhancement effect on CO2 capture performance of Na2CO3 solution. After addition of TBAB, the maximum CO2 absorption rate of Na2CO3 solution was improved to 2.52 × 10−3 mol/min, which increased by 105%. And the maximum CO2 desorption rate could also be improved by 45%. TBAB/Na2CO3 system not only realized a high CO2 absorption capacity of 0.769 mol/mol, but also maintained 82% of the initial CO2 absorption capacity after three cyclic tests. The regeneration heat duty of TBAB/Na2CO3 solution was calculated to be 1136.6 kJ/mol, which was significantly lower than that of single Na2CO3 solution and conventional MEA aqueous solution. The promotion mechanism of TBAB in Na2CO3 solution was explored using Fourier transform infrared spectra (FTIR) and 13C nuclear magnetic resonance (NMR) analysis.CONCLUSIONThe introduction of TBAB additive could significantly improve CO2 capture performance of Na2CO3 solution and reduce regeneration heat duty, making it a possible option in the field of post‐combustion CO2 capture. © 2023 Society of Chemical Industry (SCI).

Theoretical and experimental analysis of CO2 capture into 1,5-diamino-2-methyl-pentane/n-propanol non-aqueous absorbent regulated by ethylene glycol

The non-aqueous amine solvents for CO2 capture gaine an advantage in energy-saving potential, but with a sharp increase viscosity after saturated absorption would easily cause problems such as equipment scaling and pipe blockage. In the present work, the ethylene glycol (EG) was used as co-solvent and activator to regulate the non-aqueous absorbent of 1,5-diamino-2-methyl-pentane (DA2MP) and n-propanol (PrOH) for CO2 capture. The absorption loading of the mixture solution was 1.13 mol·mol−1 when the mass concentration of DA2MP was 25 wt% and the volume ratio of PrOH to EG was 8:2. By activated by EG, the viscosity of the saturated solution was only 9.05 mPa·s, which changed from viscous precipitation to clarify liquid compared with that of DA2MP/PrOH. The absorbent maintained 90.30% of its initial CO2 absorption loading after 10th cycle regeneration under 393.15 K for 60 min. According to the quantum chemical calculations and experimental results, the reaction and regulation mechanism of CO2 capture into DA2MP/PrOH/EG was clarified. In DA2MP-PrOH solution, CO2 firstly reacted with DA2MP to form carbamate, and them the product further reacted with PrOH to form alkyl carbonates, which was viscous and insoluble due to the high intermolecular force between the CO2 products. After adding appropriate amount of EG, the solubility of insoluble products in solvent was increased through weakening the intermolecular interaction of products and enhancing the intermolecular interaction between products and solvents, which further converted them into soluble alkyl carbonate and realized viscosity reduction. The regeneration heat duty of DA2MP/PrOH/EG solution was estimated as 1.58 GJ·ton−1 CO2, which was 29.5% and 58.42% less than that of DA2MP/PrOH and bench mark MEA solution, respectively, indicating a alternative candidate for CO2 capture.

Acid-treated activated carbon as simple and inexpensive catalyst to accelerate CO2 desorption from aqueous amine solution

Catalytic amine regeneration has emerged as a promising technique for accelerating CO2 desorption from aqueous amine solutions at temperatures ≤ 100 ⁰C, to ultimately reduce the thermal penalty of CO2 capture process. However, the development of abundant and inexpensive materials is imperative. Herein, we prepared superabundant and low-cost activated carbon (AC) catalysts by activating AC with two acidic solutions, sulfuric acid (H2SO4) and phosphoric acid (H3PO4), and investigated their catalytic performance in the process of amine regeneration at a temperature of 86 °C. The experimental results revealed that the prepared catalysts are highly effective in amine regeneration process and can significantly increase the CO2 desorption rate and desorbed CO2 quantity at temperatures as low as 60 °C. Catalyst characterization data shows that the prepared catalysts have a higher surface area and acidity, together both of which can accelerate the CO2 desorption at much lower temperatures to ultimately reduce the regeneration heat duty by ∼20%. The prepared catalysts can easily be separated and reused in cyclic experiments, showcasing their potential use in a continuous CO2 capture unit. This study demonstrates the use of inexpensive materials to optimize the CO2 desorption process, ultimately leading to the development of a green CO2 capture process.

Rate-based modeling and energy optimization of acid gas removal from natural gas stream using various amine solutions

Reduction in energy consumption of industrial plants is always an essential need due to high cost, CO2 emissions and global warming caused by energy supply from fossil fuels for boilers and electricity consumers. Iran has been struggling to compensate the lack of gas supply for domestic and industrial demands in winter within the past decade despite of having large natural gas resources. One of the most economical methods to decrease energy requirements in hydrocarbon plants is process improvement and revamping by changing existing solvents. There are already 44 identical acid gas removal units under operation in the South Pars Gas Complex (located in Iran) with the same feed composition. The gas-sweetening unit in the Phase 12, operating with the solution of 45.5 wt% methyldiethanolamine (MDEA), was modeled by Aspen Plus for acid gas removal (CO2 and H2S) as a rate-based model with the application of electrolyte non–random two–liquid (E-NRTL) activity model and Peng–Robinson equation of state in addition to the actual characteristics of the absorber and regenerator, and the operational conditions of the gas and liquid streams. After validation of the model by the real data from the plant, the incumbent amine solution was replaced with five proposed amine solutions – one single and four blended amine mixtures – in the same mass concentration to select the most efficient alternative from the aspects of outlet acid gas concentration, H2S content in the treated flash gas, required total power, reboiler power supply, and regeneration heat duty. The simulation results revealed that H2S was sharply absorbed on the top of the column, while CO2 was smoothly removed from the gas phase to the MDEA and blended solutions along the absorber and it occurred at the bottom of the column for the DEA solution. The blended amine solution of 1.5 wt% sulfolane + 44 wt% MDEA (Sulfinol-M) has shown to be the most appropriate option instead of the solution of MDEA compared to other suggested absorbents, with several advantages such as higher selectivity of H2S over CO2, low temperature bulge, highest H2S loading, and outlet sweet gas flow rate while required total power, reboiler power supply, and regeneration heat duty were reduced by 21.19%, 21.26%, and 23.54% respectively. The operational conditions of the unit with the application of the Sulfinol-M solution were optimized to achieve three specifications (constraints) and the minimum required total power (objective function) through a sensitivity analysis and optimization using a genetic algorithm to assure the reliability of values for three independent parameters, namely, amine solution temperature, amine solution flow rate, and gas temperature. The optimum limits and values of these parameters were 47–50 °C, 220 – 240 ton/h, and 34 °C respectively.

Energy efficient CO2 capture in dual functionalized ionic liquids and N-methyldiethanolamine solvent blend system at elevated pressures: Interaction mechanism and heat duties

In this study, three lab synthesized dual functionalized ionic liquids (DFILs) were utilized as promoters to improve the CO2 absorption performance of methyl diethanolamine (MDEA) absorbent under elevated pressures of 2–7 bar. Initially, 5 wt% DFILs containing polyamine cations (triethylenetetramine and diethylenetriamine) and cyclic amine anions (piperazine and imidazole) were blended with 20 wt% MDEA and their physical and chemical properties were examined. The pKa value at 303 K of the blend of [TETAH][Pz] + MDEA is found to be 9.83, which is nearly equal to the industrial 30 wt% monoethanolamine (MEA) solution. The CO2 absorption performance at different temperatures and pressures demonstrated that the blending of 5 wt% DFILs into aqueous MDEA significantly altered both the absorption rate and loading. The percentage loading showed a significant 22% increase in the [TETAH][Pz] promoted aqueous MDEA blend. This is attributed to the high amount of carbamate and bicarbonate formation in the DFILs blended aqueous MDEA as revealed by 13C NMR results. These results were possible due to the highly reactive piperazine anion being a crucial factor in the significant performance of the [TETAH][Pz] blend system. Further, when the regeneration heat duty of all these absorbents was calculated, it was found that MDEA and DFILs blended MDEA absorbents consumed 25.36% and 33.34–22.79% less energy than industrial MEA, respectively along with a low absorbent loss during regeneration thus, [TETAH][Pz] and [TETAH][Im] are potential promoters in an aqueous MDEA solvent system for pressurized capture of carbon dioxide.

CO2 capture using EGHE-based water-lean solvents with novel water balance design

Maintaining water balance in water-lean solvents is drawing special attention as it may affect the capture performance and process stability. In this study, novel water-lean solvents containing ethylene glycol monohexyl ether (EGHE) and secondary alkanolamines was proposed for energy-saving postcombustion CO2 capture. Excess water from wet flue gas can be discharged from the desorber overhead condensate which can produce a spontaneous phase-separation feature. Less than 0.8 mass% EGHE was observed in the water-rich phase of the biphasic condensate. Effect of water content in these absorbents on CO2 capture performance was discussed. Most notably, regeneration energy consumption increased significantly as increasing water content in the absorbent. The proposed water-lean absorbents with 10 % H2O can reduce the regeneration heat duty by about 40% in comparison with aqueous MEA, indicating that the novel water balance design can make it competitive in a practical sense.

A new look to the old solvent: Mass transfer performance and mechanism of CO2 absorption into pure monoethanolamine in a spray column

The most mature CO2 capture technology is absorption of monoethanolamine (MEA) in packed or spray columns. Typically, an aqueous 30 wt.% MEA solution is used. High MEA concentrations are believed to hinder mass transfer rate due to high viscosity of MEA. We worked, for the first time, on the effects of using pure MEA on overall mass transfer coefficient (KGɑ) and absorption efficiency in a spray column by varying several operational parameters. Image analysis results suggested that interfacial area increased with increasing liquid flow rate. As a result, KGɑ increased. As opposed the belief in literature, KGɑ also increased with increasing MEA concentrations. The highest KGɑ was obtained in this work (11.7 kmol·m−³∙kPa−1∙h−1) is around one order of magnitude higher than most literature studies. Having more MEA molecules on the surface of the droplets led to higher KGɑ. In addition, it was shown that absorption efficiency was largely determined by inlet CO2 to MEA molar ratio. 13C NMR spectra results revealed that similar levels of carbamate were formed for MEA concentrations up to 70 wt.%. A simplified analysis on regeneration heat duty showed that decreasing water amount can lead to 3–10 fold decrease in reboiler energy duty.

Nanostructured AlOOH – A promising catalyst to reduce energy consumption for amine-based CO2 capture

In order to alleviate the intensive energy demand of amine-based post-combustion carbon capture technology, metal oxyhydroxide AlOOH of nanoscale was synthesized through the hydrothermal method and applied to accelerate the CO2 desorption rate and reduce the regeneration heat duty of aqueous monoethanolamine (MEA) solution for the first time. Results showed that the use of AlOOH could accelerate the desorption rate by up to 560% and increase the desorption amount by 251%. By comparing the performance between AlOOH and Al2O3, it can be found that the presence of extra hydroxyl groups is 20.6% more efficient in catalyzing CO2 desorption. According to a simplified heat transfer model created in this work, AlOOH could reduce the heat duty by 17% with only 0.1 wt% loading, which exhibited the highest performance cost ratio among related literature. In addition, the cyclic stability of AlOOH was confirmed through various characterization methods, including XRD, FT-IR, SEM, and N2 adsorption–desorption. More importantly, a possible catalytic mechanism of AlOOH was discussed and proved where it could change reaction pathways in different CO2 loading regions. This work reveals a promising research direction towards cost-efficient and high-performance metal oxyhydroxide catalysts in the catalytic amine regeneration field to approach the net-zero carbon emission goal.

Highly Efficient Removal of CO2 Using Water-Lean KHCO3/Isopropanol Solutions

The use of aqueous carbonate as an inorganic absorbent is not only inexpensive but also stable and environmentally friendly. However, the regeneration processes for aqueous carbonate sorbents require high regeneration heat duty; this energy intensity makes their wide utilization unaffordable. In this work, a low-temperature, energy-saving, and environmentally friendly carbon dioxide desorption method has been investigated in potassium bicarbonate-water-alcohol solutions. The addition of alcohol, particularly isopropanol, to the potassium bicarbonate-water solution can significantly increase carbon dioxide desorption capacity. The potassium bicarbonate-water-isopropanol solution used in this study (36 wt % isopropanol) resulted in 15.2 mmol of carbon dioxide desorption within 2400 s at 80 °C, which was 2000-fold higher than the potassium bicarbonate-water-solution. This research demonstrates a water-lean solvent-based carbon dioxide removal route with the potential to be economical, environmentally safe, and energy-efficient. CO2 sequestration, capture, and utilization technologies will play a key role in reducing CO2 emissions. The excellent desorption kinetics and relatively moderate desorption temperatures (80 °C) of water-lean solvent could help in reducing the cost of CO2 capture, particularly in terms of the heat demand at the regenerator.

Comprehensive mass transfer analysis of CO2 absorption in high potential ternary AMP-PZ-MEA solvent using three-level factorial design.

Mass transfer of CO2 absorption in 2-amino-2-methyl-1-propanol (AMP)-piperazine (PZ)-monoethanolamine (MEA) was statistically investigated in terms of overall mass transfer coefficient ([Formula: see text]) and CO2 removal percentage. The parameters of interest were lean solvent flux (A), rich gas flux (B), CO2 loading in the lean solvent (C), and ratio of the sampling height to the total column height [Formula: see text] (D). From ANOVA, A was the most impactable parameter on both responses with three-quarters of the overall contribution. Regarding the three-level factorial design, a second-order polynomial increasing trend of [Formula: see text] was observed as C and/or D increased. Additionally, [Formula: see text] linearly increased as A increased but was not affected by B. On the other hand, the CO2 removal percentage linearly increased as A and/or D increased but linearly decreased as B and/or C increased. Surface analysis suggested the optimum condition for both responses at a high level of A, low level of B, low level of C, and middle level of D. In this work, D was statistically investigated and included in the predictive correlation for [Formula: see text] for the first time. The main advantage of the proposed correlation over the recently reported correlations was that it did not require a measurement of CO2 partial pressure along the column height. For each amine component in the blend, (i) AMP played a positive key role in cyclic capacity and solvent regeneration duty, (ii) PZ enhanced transfer rate, and (iii) MEA elevated total amine concentration. As a result, 1.5:1.5:3 was recommended due to (i) elevations of 68.2% [Formula: see text], 14% CO2 removal percentage, 15.1% absorption capacity, and 66.7% cyclic capacity and (ii) reduction of 50% regeneration duty compared with 5M MEA. With respect to the other literature-reported solvents, AMP-PZ-MEA is very competitive in terms of transfer coefficient, cyclic capacity, and solvent regeneration heat duty.

Carbon dioxide adsorption/desorption performance of single- and blended-amines-impregnated MCM-41 mesoporous silica in post-combustion carbon capture

Abstract High-surface-area, hexagonal-structured mesoporous silica, MCM-41, was synthesized and wet impregnated with three different amines of 2-(ethylamino) ethanol (EAE), ethylenediamine (EDA), and tetraethylenepentamine (TEPA) for use as solid adsorbents in post-combustion CO2 capture application. The CO2 adsorption test was performed at 25°C and atmospheric pressure using 15/85 vol% of CO2/N2 at a 20-mL/minute flow rate. Desorption was carried out at 100°C under 20 mL/minute of N2 flow. The results show that the capacity and rate of CO2 adsorption obtained from all the amine-modified adsorbents were significantly increased with increasing amine loading due to carbamate formation. Desorption efficiency and heat duty for regeneration were also affected by the amount of amine loading. The more stable the carbamate produced, the higher the energy was required. They exhibited the highest adsorption–desorption performance at 60 wt% amines used for impregnation. Blended EAE/TEPA at different weight ratios at a total concentration at 60 wt% amines was impregnated on MCM-41 adsorbent. Sorbent impregnated with 50%/10% of EAE/TEPA showed the best performance of 4.25 mmolCO2/g at a high adsorption rate, a low heat duty of 12 kJ/mmolCO2 and with 9.4% reduction of regeneration efficiency after five repeated adsorption–desorption cycles.

Understanding the potential benefits of blended ternary amine systems for CO2 capture processes through 13C NMR speciation study and energy cost analysis

Aqueous blends of the three amines 2-aminoethanol (MEA), N-methyldiethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) were tested as sorbents for CO2 capture processes. We formulated three different blends with the same overall amine concentration (5M) but with different amine molar ratio, namely blend-1 (2M MEA+2M MDEA+1M AMP), blend-2 (1M MEA+2M MDEA+2M AMP) and blend-3 (2M MEA+1M MDEA+2M AMP). Their CO2 absorption and desorption performances were investigated in batch experiments in terms of CO2 equilibrium solubility, CO2 absorption at 40 °C and CO2 desorption at 100 °C as a function of time, and energy consumption during the regeneration process. The results were compared to those obtained under the same operating conditions with 5M aqueous MEA, the benchmark sorbent for CO2 absorption processes. The effect of the different amino composition on the CO2 capture mechanism was evaluated by identifying and quantifying the species formed during the capture process through an accurate 13C NMR speciation study. The results obtained showed that all formulated sorbents have higher desorption performance and require less energy for regeneration than conventional aqueous MEA, confirming that blending different alkanolamines has the potential to improve CO2 capture. In particular, blend-2 can be regarded as a promising sorbent for implementation in commercial systems, as it performed a desorption rate up to 5 times higher than conventional aqueous MEA, combined with a significantly lower relative heat duty for regeneration (41.5%) and lower operating costs for CO2 capture.

Simulation and validation of carbon dioxide removal from the ethane stream in the south pars phase 19 gas plant by different amine solutions using rate-based model

The high pressure absorption of carbon dioxide (CO2) from a distilled ethane stream at Phase 19 of South Pars Gas Complex (in Iran) has been simulated by Aspen Plus using non-random two-liquid and Peng-Robinson models in addition to the technical and operational data. The plant employs 40 wt% diethanolamine (DEA) solution as the actual absorbent in a conventional column. The potential single and blended absorbents including methyldiethanolamine (MDEA), piperazine (PZ) + MDEA, and DEA + MDEA have been modelled to estimate the outlet CO2 and sulfur compounds concentrations, CO2 loading, reboiler power supply and regeneration heat duty to determine the most efficient substitute. The model is in good agreement with the real data of the plant. The rate-based simulation results reveal that CO2 and H2S concentrations have nearly reached zero while the total sulfur content is below the demanded specification (10 ppm wt) by the application of a blended amine solution with a low PZ concentration as 1 wt% PZ + 39 wt% MDEA in the operational limits of 110–120 ton/hr and 40–55 °C, suggesting that the PZ + MDEA solution can be used as the most appropriate alternative to the 40 wt% DEA solution due to the higher CO2 concentration (1.950% mole) and CO2 loading (0.216) of the rich solution as well as the lower required regeneration heat duty (10.590 GJ).