Lean Solvent Research Articles

Experimental investigation of CO2 capture at high pressure using energy-efficient amino acid salt solvents

The increase in energy consumption has led to greenhouse gas emissions, specifically CO2. This has caused many researchers to explore the possibility of capturing CO2 emissions. The utilization of typical water-based solvents, such as amine solutions, poses challenges in large-scale operations owing to the substantial energy consumption associated with their regeneration process. To decrease the energy required to regenerate the solvent, new types of phase change solvents, known as lean water amino acid-based phase change solvents, were invented. This study investigated the absorption capacity of an amino acid salt made up of glutamine and potassium hydroxide in a water-based solution including N,N-dimethylformamide (DMF) as a co-solvent. The measurement of absorption capacity was conducted under elevated pressures ranging from 5 to 30 bar. Additionally, an investigation was conducted to assess the impact of DMF volumetric concentration on absorption capacity. The findings of the study indicated that augmenting both the pressure and concentration of DMF increased the capacity for CO2 absorption. This enhancement was achieved by simultaneously raising the rates of physical and chemical absorption. The results obtained from the C NMR phase analysis revealed that the solid phase had carbon bonds that were related to the absorption of CO2, whilst the upper liquid phase did not contain any CO2. This phase might readily be recycled into the absorption process without the need for regeneration. The absorption capacity of this solvent was also assessed following three absorption-reduction cycles. The results indicated a decrease in absorption capacity by only 6.6 %.

Computational Investigation of Co-Solvent Influence on CO2 Absorption and Diffusion in Water Lean Solvents

Computational Investigation of Co-Solvent Influence on CO2 Absorption and Diffusion in Water Lean Solvents

Covalent organic frameworks with tunable Co–N–C for high-performance carbamate decomposition via sulfonic modification in amine-based CO2 capture

Nanowire-like COF support with sulfo group (-SO3H) decoration was designed and synthetized, to offer favourable conditions for atomically dispersing Co atoms (S–Co/NC). The ingenious coordination of sulfo group synergistically improved COF structure and Co–N–C scheme, creating high surface area and excellent catalytic activity. Lab-scale experimental evaluations confirmed that the maximum CO2 desorption rate of spent MEA-solvent increased significantly by 733 % (3.74 CO2 mmol/min) after introducing S–Co/NC catalysts, ascribed to its contribution for proton transfer and C-N break. Bench-scale experiments demonstrated that a mere 0.0125 wt% of catalyst in MEA-solvent substantially decreased the CO2 loading of lean solvent by 17.7 % at low desorption temperatures (120→110 °C), resulting in a 28.8 % reduction in energy consumption. Furthermore, the negligible degradation of catalytic performance during 100-h testing wall-validated the stability and durability of the S–Co/NC catalysts. This work provided a prominent COF-based solid acid catalysts for energy-saving solvent regeneration during amined-based CO2 capture.

Hybrid Advanced Control Strategy for Post-Combustion Carbon Capture Plant by Integrating PI and Model-Based Approaches

Even though the energy penalties and solvent regeneration costs associated with amine-based absorption/stripping systems are important challenges, this technology remains highly recommended for post-combustion decarbonization systems given its proven capture efficacy and technical maturity. This study introduces a novel centralized and decentralized hybrid control strategy for the post-combustion carbon capture plant, aimed at mitigating main disturbances and sustaining high system performance. The strategy is rooted in a comprehensive mathematical model encompassing absorption and desorption columns, heat exchangers and a buffer tank, ensuring smooth operation and energy efficiency. The buffer tank is equipped with three control loops to finely regulate absorber inlet solvent solution parameters, preventing disturbance recirculation from the desorber. Additionally, a model-based controller, utilizing the model predictive control (MPC) algorithm, maintains a carbon capture yield of 90% and stabilizes the reboiler liquid temperature at 394.5 K by manipulating the influent flue gas to the lean solvent flowrates ratio and the heat duty of the reboiler. The hybrid MPC approach reveals efficiency in simultaneously managing targeted variables and handling complex input–output interactions. It consistently maintains the controlled variables at desired setpoints despite CO2 flue gas flow disturbances, achieving reduced settling time and low overshoot results. The hybrid control strategy, benefitting from the constraint handling ability of MPC, succeeds in keeping the carbon capture yield above the preset minimum value of 86% at all times, while the energy performance index remains below the favorable value of 3.1 MJ/kgCO2.

Post-combustion carbon capture process modeling, simulation, and assessment of synergistic effect of solvents

Post-combustion carbon capture appears to be a promising solution to reduce the emission of carbon dioxide (CO2) from power plants that generate electricity using either coal or natural gas. In addition, carbon capture process efficiency, capacity, and energy consumption have become challenging against the performance of the capture process. However, synergistic effect due to solvents blend has gained attention to reduce the process energy consumption and enhance process efficiency. In this study, blends of methyldiethanolamine (MDEA) and piperazine (PZ) at different concentrations were investigated using a validated post-combustion capture process model using Aspen HYSYS. Results were compared with 30 wt% monoethanolamine (MEA) as reference case. The effective process variables are concentration of solvents, the amount of water and solvent in the makeup section, viscosity of solvent, energy consumed in different process stages, and the amount of lean solvent flow rate. These variables were studied against fixed process variables using rate-based model. The study shows that using (43 wt% MDEA/7 wt% PZ) for post-combustion carbon capture needs 2.53 MJ/kgCO2 regeneration energy for 88.5% process efficiency compared to 4.003 MJ/kgco2 for 30 wt% MEA without the need for any process modifications. In addition, it was found that solvents synergistic effect contributes to resolving the drawbacks of post-combustion capture that will enable the high utilization of the process and contribution to reduce the consequences effect of climate change. Therefore, the study will help policymakers, industries and encourage researchers towards the large-scale commissioning of blended solvent -based post-combustion capture process.

Energy optimization of a non-aqueous solvent CO2 absorption system with pressure swing regeneration

This study focuses on optimizing the energy requirement in the post-combustion CO2 capture system using pressure swing regeneration through a model-based design (MBD). The simulation results highlight the significant impact of CO2 recovery, inlet gas and liquid flow rate, and CO2 concentration in the flue gas on the overall energy demand of the system. Moreover, an investigation into the de-sublimation chamber was undertaken, revealing a relationship between dry ice formation and the heat transfer between the LNG stream and CO2 in the heat exchanger. The parametric analysis study reveals that the sensible heat of the lean solvent is significantly influenced by the CO2 concentration in the liquid, consequently affecting the overall system energy. According to the results, the utilization of cold energy from LNG could save 80 % of the total energy requirement. The optimization results found the best working condition, which consumes energy of 0.190 GJ/ton CO2, 31 % lower than the basic scenario.

In-house synthesized poly(ether ether ketone) ionenes. II. ToF-SIMS spectra in the negative ion mode

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to analyze poly(ether ether ketone) (PEEK) based membranes. PEEK membranes have been shown to be effective in the separation of CO2 from flue gases (post-combustion technique). The PEEK membranes were synthesized using novel aromatic ether-ketone linkages inspired by PEEK with polymeric backbone bistriflimide [Tf2N]− counterions. One of the keys to advancing this technology is developing membranes that are selective and permeable toward CO2, in which PEEK based membranes have been shown to be. Furthermore, the compatibility between various water lean solvents also needs to be investigated. Surface analytical techniques such as x-ray photoelectron spectroscopy and ToF-SIMS are useful for investigating chemical changes between membranes. Herein, we present ToF-SIMS data obtained in the negative ion mode for four different PEEK membranes designed for use in CO2 capture systems. Positive ion mode spectra are reported in Paper I.

Minimalization of Dissolved Heavy Hydrocarbon on Lean Solvent with Absorption Optimization

Pertamina EP DonggiMatindok Field has an Acid Gas Removal Unit (AGRU)which is an acid gas (H2S) separator unit that flows from the LP Separator. An increase of pressure differential occurred in the AGRU indicates a foaming tendency and impacting on decrease in sales gas. The well switch method was carried out to overcome foaming event by opening the manual valve in stages from 25%, 50%, 75% and 100% with waiting time of 30 minutes each stage. Besides, solvent flow adjustment is carried out using HYSYS simulation to find optimal solvent flow requirements through ratio of flow balance between feed gas and lean solvent. This method aims to minimize heavy hydrocarbons dissolved in the solvent by optimizing absorption process. After implementing this method, a decrease occurred in the average solvent flow of 2,308 BPD at 10 MMSCFD feed gas, the pressure differential relatively stable at 3-4 psig which indicate no foaming event. Laboratory result shows that Heavy Hydrocarbon Content parameter were 60 mg/L and Particulate Matter Content (>0.45µm) was 22 mg/L. This method also extends the lifecycle of the solvent and has an impact on reducing the solvent packaging waste which categorized as toxic and hazardous waste.

A predictive model for the techno-economic assessment of CO[formula omitted] chemisorption processes applicable to a large number of amine solvents

With the growing need to reduce carbon dioxide (CO2) emissions, there have been substantial efforts to identify new solvents that can improve the overall performance of chemical-absorption CO2 capture processes. Given the large number of potential solvents, computer-aided molecular and process design (CAMPD) approaches can play a critical role in accelerating the search for optimal solvents by enabling the systematic exploration of solvent candidates and process conditions. One of the challenges in developing such a framework is the requirement for a process model that can be used to capture the interactions between process performance and solvent structure without significantly increasing its numerical complexity. In the current work, a model for the absorption–desorption of CO2 is developed using the predictive SAFT-γ-Mie group-contribution approach, allowing the performance of numerous solvents to be assessed without the need for extensive experimental data. In order to avoid convergence difficulties when solving this highly nonlinear model, a tailored initialization strategy is established, using an adapted inside-out algorithm to prime a nonlinear equation solver for each column, providing a good initial guess for the whole flowsheet. Tests on three solvents confirm the robustness of the approach. Building on this enhanced numerical stability, the model is validated by comparison against pilot-plant data, showing good accuracy. A detailed parametric study of the effect of the key process variables is undertaken; the important role of the CO2 capture rate, of the lean solvent temperature and loading, and of the desorber pressure is highlighted. The results of the parametric study are used to formulate an optimization problem which is successfully solved for four solvents. A large reduction in total annualized cost and energy requirements is achieved by tuning the operating conditions to each solvent considered. The predictive capability, robustness, and reliability of the proposed model and associated initialization strategy open the way for the evaluation of a large number of novel solvents.

Comparative techno-economic analysis of CO2 capture processes using blended amines

Blended amines synthesize the absorption characteristics of different amine solvents and show a great potential in carbon capture. However, a comprehensive techno-economic analysis (TEA) of the CO2 absorption process using blended amines is still lacking. In this study, we investigated three blended amine solvents: MEA/MDEA, PZ/MEA, and PZ/MDEA, with commercially available amine MEA used as the benchmark. Rigorous process simulation and techno-economic analysis were applied to evaluate the performance of the carbon capture process in a steel plant. CO2 molar loading in the lean solvent (αlean) and stripper pressure (P) were optimized to minimize the total annualized cost (TAC). The results demonstrated that PZ/MDEA-based process is most cost-effective (31.43$/tCO2) under the operating conditions of αlean = 0.15 and P = 1.25 bar. The cost breakdown analysis revealed that αlean and P significantly impact the TAC through the regeneration heat, equipment investment, and amines make-up cost. Furthermore, the energy analysis indicated that using a solvent with a low reaction enthalpy and heat capacity as well as high reactivity and absorption capacity could minimize the energy consumption of the process.

Machine learning based modelling and optimization of post-combustion carbon capture process using MEA supporting carbon neutrality

The role of carbon capture technology using monoethanolamine (MEA) is critical for achieving the carbon-neutrality goal. However, maintaining the efficient operation of the post-combustion carbon capture is challenging considering the hyperdimensional design space and nonlinear characteristics of the process. In this work, CO2 capture level from the flue gas in the absorption column is investigated for the post-combustion carbon capture process using MEA. Artificial neural network (ANN) and support vector machine (SVM) models are constructed to model CO2 capture level under extensive hyperparameters tuning. The comparative performance analysis based on external validation test confirmed the superior modelling and generalization ability of ANN for the carbon capture process. Later, partial derivative-based sensitivity analysis is carried out and it is the found that absorbent-based input variables like lean solvent temperature and lean solvent flow rate are the two most significant input variables on CO2 capture level in the absorption column. The optimization problem with the ANN model embedded in the nonlinear programming-based optimization environment is solved under different operating scenarios to determine the optimum operating ranges for the input variables corresponding to the maximum CO2 capture level. This research presents the optimum operating conditions for CO2 removal from the flue gas for the post-combustion carbon capture process using MEA that contributes to achieving the carbon neutrality goal.

Energy-efficient carbon dioxide capture using piperazine (PZ) activated EMEA+DEEA water lean solvent: Performance and mechanism

Water vapor contained in industrial waste gas will be accumulated in non-aqueous amine solvents when used for CO2 capture and subsequently affect capture efficiency. While Piperazine (PZ) could be considered as an activator of the solution. Hence the effect of different contents of water and PZ added into the non-aqueous amine solvents on the CO2 capture performance has been investigated. 13C NMR has been used to identify the compounds present in aqueous CO2-rich amine solvents to characterize the mechanism of reactions. The energy consumption using 2-(ethylamino)ethanol (EMEA) water-lean amine solvent and aqueous monoethanolamine (MEA) solution was tested and compared on lab-scale, and further a comprehensive evaluation in a bench-scale pilot plant has been performed; It was found that the regeneration efficiency of the solution was reduced by approximately 10% when the water content was 10 wt%. The addition of PZ can recover the regeneration efficiency of the solvent to 94.2%. And its energy consumption was reduced by about 45% compared to the aqueous MEA solution in a 72-hour continuous absorption-desorption experiment. The results demonstrated that the aqueous PZ solution could improve the regeneration efficiency by involving in the proton transfer process. This work has proven that the blend of water-lean amine solvent and PZ is a novel, energy-efficient absorbent for CO2 capture.

Retrofit of the acid gas sweetening process for the refinery based on exergy analysis method

Although the acid gas sweetening process in the petrochemical and natural gas industries has continually improved over the past few decades, the energy consumption and process optimization remain a challenge. In this study, based on the process simulation and exergy analysis, the bottlenecks of a typical acid gas sweetening process for the refinery was analyzed using Aspen HYSYS, and the optimization strategies were discussed and proposed. First, a novel low temperature absorption with a lean solvent temperature of 15 °C was developed coupled with the recovery of cold energy of sweet gas, which improved the absorption efficiency and reduced the circulation rate of lean solvent. Then a modified heat pump distillation combining split flow feeding technology was developed. After optimization of the novel process developed, the results indicated that operating cost and overall energy consumption was dramatically reduced by 14% and 22% for the absorption process respectively, and combined with the modified regeneration process, the energy recovery efficiency was further improved. The operating cost, the comprehensive energy consumption and the TAC were totally reduced by 19.3%, 30%, and 13.1%, respectively. Finally, the primary investment analysis indicates that the retrofits are feasible, which provides an alternative for the acid gas sweetening.

Diamine based hybrid-slurry system for carbon capture

Hybrid adsorption-absorption slurry systems are very attractive for CO2 capture, given their ability to simultaneously lower regeneration energy and increase absorption rate and uptake, because of enhanced mass and heat transfer mechanisms. In this work, novel hybrid slurries were formulated from the dispersion of 1 wt.% of solid adsorbents in a water-lean solvent of 30 wt.% of Tetramethyl-1,3-diaminopropane (TMPDA) + 10 wt.% Ethanol (EtOH) for CO2 capture. Different solid particles were suspended in the water-lean solvent such as activated carbon, ion-exchanged zeolite Y (Mg-Y), and polyethyleneimine doped silicas (PEI-SG and PEI-MCM-41). The CO2 uptake of the solid and fluid components of the slurries was confirmed by pH, density, and Fourier transform infrared analysis. The neat water lean solvent reduced the absorption energy by 16 % and slightly increased the CO2 uptake by 0.6 % compared to the aqueous TMPDA solvent. Additionally, the hybrid slurries exhibited further reductions in absorption energy of 10 – 30 % compared to the benchmark TMPDA-based solvents. The PEI-MCM-41-based slurry presented the highest CO2 uptake of 0.33 g CO2.g−1 and lowest regeneration energy of 2261.30 kJ.kg−1 among the studied systems. Additionally, the hybrid slurry exhibited a 21 % reduction in CO2 uptake compared to the benchmark 30 wt.% aqueous monoethanolamine (MEA) and similar capacity to aqueous methyl diethanolamine (MDEA), however, resulting in a far higher reduction in absorption enthalpy of 56 %, and 29 % compared to aqueous MEA and MDEA, respectively. The results obtained here encourage further development and optimization of hybrid slurry systems as potential efficient systems for CO2 capture.

Application of rotating packed bed technology for biogas upgrading

Biogas is a renewable energy source consisting mainly of methane, carbon dioxide, and other impurities. A purification process is required to remove the impurities (biogas upgrading and purification) to meet the requirements as an energy source for vehicles. Removal of CO2 from the biogas stream, which accounts for about 40% of the impurities, is necessary to produce biogas (mainly methane) for use in vehicles. Chemical absorption of CO2 using a rotating packed bed was considered due to its high CO2 absorption efficiency and small column size. Aspen Plus and Visual Fortran software were used to develop the model, and monoethanolamine (MEA) was used as the absorbent. The developed model was validated with experimental data, where the relative error is less than 10%. The process analysis performed shows: (a) biogas purity increases with rotation speed. (b) An increase in lean solvent concentration leads to an increase in CO2 capture efficiency and biomethane purity. (c) An increase in biogas throughput leads to an increase in biogas purity. The study may be useful for the design and operation of intensified CO2 capture from biogas streams for vehicle applications.

Enhancing Efficiency of Corncob-Fired Power Generation with Carbon Capture and Storage

Bioenergy from biomass wastes with carbon capture and storage (CCS) is an important way to compensate for hard-to-abate emissions and collaborate with decarbonizing the energy industry. This work evaluates a corncob-fired power generation with CCS regarding overall energy efficiency in two process alternatives: (a) post-combustion CO2 capture by an aqueous blend of methyl-diethanolamine and piperazine; and (b) oxy-combustion coupled to state-of-art air separation unit. The alternatives are simulated in Aspen HYSYS and compared with a conventional plant to evaluate the energy penalty of capturing CO2. The lean solvent composition is optimized for the lowest regeneration heat demand (2.92 GJ/tCO2). Post-combustion capture designed for 90% CO2 abatement presents an efficiency penalty of 7.96%LHV. In contrast, Oxy-combustion has zero CO2 emissions and outperforms Post-combustion with a lower penalty of 6.77%LHV, given a chance to have oxygen supplied at an energy cost of 139 kWh/tO2. To render Post-combustion the most efficient route, it would be necessary to have its reboiler heat ratio reduced to 2.30 GJ/tCO2.

Comparison of the performance of solvent wash reagents used for the primary cleanup of degraded PUREX solvent

Abstract The effectiveness of the solvent wash reagents such as sodium carbonate and hydrazine carbonate were compared using the lean solvent obtained during reprocessing of high plutonium content fast reactor spent nuclear fuel. The concentrations of the reagents were optimized based on the removal of retained metal ions from the lean solvent and 1.5 M hydrazine carbonate was found to be optimal and superior to sodium carbonate to be adopted as the reagent for primary cleanup of the spent solvent. Both the reagents were found to possess excellent room temperature stability and their performance was not affected upon gamma irradiation which was assessed in terms of capacity to remove di-butyl phosphate from degraded TBP/n-DD system.

The impact of novel diamine based aqueous and water lean solvents on the corrosion of carbon steel

Two diamine based water lean solvents PNH and ENH (N,N-dimethyl-1,3-propanediamine (DMPDA) and N,N-dimethyl-1,2-ethanediamine (DMEDA) respectively) using N-methyl pyrrolidone (NMP) as a diluent together with their corresponding aqueous solvents were investigated for their corrosivity of carbon steel. Siderite (FeCO3) film is demonstrated to provide stronger corrosion resistance than chukanovite (Fe2(CO3)(OH)2) film formed in aqueous solvents, DMEDA-H2O and DMPDA-H2O. Diamine water lean solvents ENH and PNH showed more severe corrosion behavior (ten-fold higher dissolved iron concentration) due to a lack of film protection. Improved anti-corrosion ability was observed in diamine water lean solvents by increasing the water content to 40%.

Vapor–Liquid Equilibrium Measurements for Aqueous Mixtures of NH3+ MDEA + CO2and KOH + MDEA

Isothermal vapor–liquid equilibrium measurements were performed for aqueous solutions containing N-methyl diethanolamine (MDEA), MDEA + ammonia (NH3), MDEA + potassium hydroxide (KOH), MDEA + carbon dioxide (CO2), NH3 + CO2, and MDEA + NH3 + CO2. The experiments were carried out between 310 and 390 K and 0.07 and 34 bar using a static synthetic apparatus. Overall, 202 data points are reported in terms of total volume, total number of moles, temperature, and pressure. The experimental results for MDEA(aq), NH3(aq) + CO2(aq), and MDEA(aq) + CO2(aq) are in good agreement with the calculations done using the Extended UNIQUAC model within the studied range. The data presented in this work are also comparable to previously published measurements. This work reports for the first time VLE measurements for aqueous mixtures of MDEA + NH3 and MDEA + KOH. These data suggest that the interactions between MDEA(aq) and NH3(aq) or K+(aq) ions have a minor effect on the equilibrium pressures. Consequently, other physical properties are needed to describe the thermodynamic state of these systems, such as heat capacity, heat of dilution, and other phase equilibrium measurements. The isothermal VLE measurements for solutions containing NH3(aq) showed a pressure minimum that was confirmed by model estimates and by other works done in similar conditions. As a consequence, it is not possible to estimate the partial pressure of CO2 based on the difference between the pressure at equilibrium conditions and the partial pressure of the lean solvent. This paper demonstrates that this common approach to determining the partial pressure of gases may introduce a bias in these values. The dissolution of CO2 into MDEA(aq) + NH3(aq) mixtures changes the speciation of the system, leading to an increase in the concentration of their protonated species (MDEAH+(aq) and NH4+(aq), respectively). For this reason, the interaction between these charged species must be determined in order to perform reliable phase equilibrium calculations. Ultimately, the measurements reported in this work can be used for thermodynamic modeling of CO2 capture solvents to ensure accurate results in process simulation.

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.