Post-combustion Capture Research Articles

Thermodynamic Analysis of Low-Emission Offshore Gas-to-Wire Firing CO2-Rich Natural Gas: Aspects of Carbon Capture and Separation Systems

Despite the growth of renewable energy, fossil fuels dominate the global energy matrix. Due to expanding proved reserves and energy demand, an increase in natural gas power generation is predicted for future decades. Oil reserves from the Brazilian offshore Pre-Salt basin have a high gas-to-oil ratio of CO2-rich associated gas. To deliver this gas to market, high-depth long-distance subsea pipelines are required, making Gas-to-Pipe costly. Since it is easier to transport electricity through long subsea distances, Gas-to-Wire instead of Gas-to-Pipe is a more convenient alternative. Aiming at making offshore Gas-to-Wire thermodynamically efficient without impacting CO2 emissions, this work explores a new concept of an environmentally friendly and thermodynamically efficient Gas-to-Wire process firing CO2-rich natural gas (CO2 > 40%mol) from high-depth offshore oil and gas fields. The proposed process prescribes a natural gas combined cycle, exhaust gas recycling (lowering flue gas flowrate and increasing flue gas CO2 content), CO2 post-combustion capture with aqueous monoethanolamine, and CO2 dehydration with triethylene glycol for enhanced oil recovery. The two main separation processes (post-combustion carbon capture and CO2 dehydration) have peculiarities that were addressed at the light shed by thermodynamic analysis. The overall process provides 534.4 MW of low-emission net power. Second law analysis shows that the thermodynamic efficiency of Gas-to-Wire with carbon capture attains 33.35%. Lost-Work analysis reveals that the natural gas combined cycle sub-system is the main power destruction sink (80.7% Lost-Work), followed by the post-combustion capture sub-system (14% Lost-Work). These units are identified as the ones that deserve to be upgraded to rapidly raise the thermodynamic efficiency of the low-emission Gas-to-Wire process.

Thermodynamically Efficient, Low-Emission Gas-to-Wire for Carbon Dioxide-Rich Natural Gas: Exhaust Gas Recycle and Rankine Cycle Intensifications

Onshore gas-to-wire is considered for 6.5 MMSm3/d of natural gas, with 44% mol carbon dioxide coming from offshore deep-water oil and gas fields. Base-case GTW-CONV is a conventional natural gas combined cycle, with a single-pressure Rankine cycle and 100% carbon dioxide emissions. The second variant, GTW-CCS, results from GTW-CONV with the addition of post-combustion aqueous monoethanolamine carbon capture, coupled to carbon dioxide dispatch to enhance oil recovery. Despite investment and power penalties, GTW-CCS generates both environmental and economic benefits due to carbon dioxide’s monetization for enhanced oil production. The third variant, GTW-CCS-EGR, adds two intensification layers over GTW-CCS, as follows: exhaust gas recycle and a triple-pressure Rankine cycle. Exhaust gas recycle is a beneficial intensification for carbon capture, bringing a 60% flue gas reduction (reduces column’s diameters) and a more than 100% increase in flue gas carbon dioxide content (increases driving force, reducing column’s height). GTW-CONV, GTW-CCS, and GTW-CCS-EGR were analyzed on techno-economic and environment–thermodynamic grounds. GTW-CCS-EGR’s thermodynamic analysis unveils 807 MW lost work (79.8%) in the combined cycle, followed by the post-combustion capture unit with 113 MW lost work (11.2%). GTW-CCS-EGR achieved a 35.34% thermodynamic efficiency, while GTW-CONV attained a 50.5% thermodynamic efficiency and 56% greater electricity exportation. Although carbon capture and storage imposes a 35.9% energy penalty, GTW-CCS-EGR reached a superior net value of 1816 MMUSD thanks to intensification and carbon dioxide monetization, avoiding 505.8 t/h of carbon emissions (emission factor 0.084 tCO2/MWh), while GTW-CONV entails 0.642 tCO2/MWh.

Solar-Assisted Carbon Capture Process Integrated with a Natural Gas Combined Cycle (NGCC) Power Plant—A Simulation-Based Study

In the realm of Natural Gas Combined Cycle (NGCC) power plants, it is crucial to prioritize the mitigation of CO2 emissions to ensure environmental sustainability. The integration of post-combustion carbon capture technologies plays a pivotal role in mitigating greenhouse gas emissions enhancing the NGCC’s environmental profile by minimizing its carbon footprint. This research paper presents a comprehensive investigation into the integration of solar thermal energy into the Besmaya Natural Gas Combined Cycle (NGCC) power plant, located in Baghdad, Iraq. Leveraging advanced process simulation and modeling techniques employing Aspen Plus software, the study aims to evaluate the performance and feasibility of augmenting the existing NGCC facility with solar assistance for post-carbon capture. The primary objective of this research is to conduct a thorough simulation of the Besmaya NGCC power plant under its current operational conditions, thereby establishing a baseline for subsequent analyses. Subsequently, a solar-assisted post-combustion capture (PCC) plant is simulated and seamlessly integrated into the existing power infrastructure. To accurately estimate solar thermal power potential at the Baghdad coordinates, the System Advisor Model (SAM) is employed. The integration of solar thermal energy into the NGCC power plant is meticulously examined, and the resulting hybrid system’s technical viability and performance metrics are rigorously evaluated. The paper contributes to the field by providing valuable insights into the technical feasibility and potential benefits of incorporating solar thermal energy into conventional natural gas power generation infrastructure, particularly in the context of the Besmaya NGCC plant in Baghdad. The power generation capacity of the plant was set at 750 MW. With this capacity, the annual CO2 generation was estimated at 2,119,318 tonnes/year which was reduced to 18,064 tonnes/year (a 99% reduction). The findings aim to inform future decisions in the pursuit of sustainable and efficient energy solutions, addressing both environmental concerns and energy security in the region.

Modeling gas–liquid equilibrium of carbon dioxide in mixtures of (1-butyl-3-methyl-imidazolium acetate + 1-(2-aminoethyl) piperazine + water) and (1-butyl-3-methyl-imidazolium acetate + bis (3-aminopropyl) amine + water) by electrolyte non-random two liquid (e-NRTL) model

Targeting the control in emissions of post-combustion carbon dioxide capture from large point sources, a simulation approach towards the estimation of important thermodynamic property parameters useful in designing of carbon capture and sequestration technologies is being proposed. In the current work, simulation is carried out for modeling the gas – liquid equilibrium of CO2 in two aqueous mixtures of ionic liquid 1-butyl-3-methyl imidazolium acetate ([bmim][Ac]) and amines viz. ([bmim][Ac] + 1-(2-aminoethyl) piperazine) (AEP) and ([bmim][Ac] + bis (3-aminopropyl) amine) (APA). The experimental CO2 solubilities were taken from our previously published work and is regressed with electrolyte–Non-Random Two Liquid (e-NRTL) model for the liquid phase while Redlich-Kwong (RK) equations of state (EOS) was used to model the gas phase. Various thermodynamic parameters of importance and concentration of species in the mixtures were regressed in the model using Aspen Plus 14.

An Assessment of CO2 Capture Technologies towards Global Carbon Net Neutrality

Carbon dioxide, the leading contributor to anthropogenic climate change, is released mainly via fossil fuel combustion, mostly for energy generation. Carbon capture technologies are employed for reducing the emissions from existing huge point sources, along with capturing them from direct air, to reduce the existing concentration. This paper provides a quantitative analysis of the various subtypes of carbon capture technologies with the aim of providing an assessment of each from technological, social, geo-political, economic, and environmental perspectives. Since the emissions intensity and quantity, along with the social–political–economic conditions, vary in different geographic regions, prioritising and finding the right type of technology is critical for achieving ambitious net-zero targets. Four main types of carbon capture technology were analysed (adsorption, absorption, membrane, and cryogenic) under four scenarios depending on the jurisdiction. The Technique for Order of Preference by Similarity to Ideal Solution (also known as the TOPSIS method) was used to establish a quantitative ranking of each, where weightages were allocated according to the emissions status and economics of each depending on the jurisdiction. Furthermore, forecasting the trends for technology types vis à vis carbon neutral targets between 2040 and 2050 was carried out by applying regression analysis on existing data and the emissions footprint of major contributing countries. The study found the membrane score to be the highest in the TOPSIS analysis in three of the four scenarios analysed. However, absorption remains the most popular for post-combustion capture despite having the highest energy penalty per ton of CO2 capture. Overall, capture rates are well short of projections for carbon neutrality; the methodology put forward for prioritising and aligning appropriate technologies and the region-by-region analysis will help highlight to technocrats, governments, and policymakers the state of the art and how to best utilise them to mitigate carbon emissions—critical in achieving the net-zero goals set at various international agreements on climate change.

Measurement of the critical temperatures, pressures, and thermal diffusivities of glymes from monoglyme to tetraglyme

The critical temperatures, critical pressures, and thermal diffusivities have been measured for mono-, di-, tri-, and tetraglymes, compounds that are used for pre- and post-combustion capture of CO2, H2S and other gases. The critical properties have been measured using the pulse-heating method applicable to thermally unstable compounds. The combined relative expanded uncertainties with the 0.95 level of confidence are 0.01 and 0.03 for the critical temperature and pressure, respectively. The acentric factors of the compounds have been calculated based on the experimental data. The critical properties of these compounds have also been calculated by the group contribution methods of Wilson and Jasperson, Nannoolal et al., and Hukkerikar et al. in two variants. The Wilson/Jasperson technique provides the best estimation of the critical temperature and the Hukkerikar et al. one gives the best results for the critical pressure. The thermal diffusivities of glymes have been measured at atmospheric pressure in the temperature range from 303.15 to 353.15 K. The thermal conductivities of glymes have been calculated from the experimental data. The temperature dependence of the thermal diffusivities and thermal conductivities has been approximated by linear polynomials. The experimental thermal conductivities of glymes have been compared with those estimated by the methods of Govender et al. and Liu et al. The method of Govender et al. provides a good estimation of the thermal conductivity of glymes.

Operating optimization of biomass direct-fired power plant integrated with carbon capture system considering the life cycle economic and CO2 reduction performance

Biomass direct-fired power plant integrated with carbon capture system can achieve negative CO2 emission during the power generation, which provides an important technology pathway for the transformation of energy system towards carbon neutrality. Understanding the economic competitiveness and CO2 reduction potential of the plant, and identifying the optimal operating mode are the key to fully exert the advantages of the technology. For this reason, this paper develops life cycle economic and CO2 emission assessment models for the biomass direct-fired circulating fluidized bed boiler power plant (BCFBP) integrated with solvent-based post-combustion carbon capture (PCC) system. The levelized cost and CO2 emission of energy indexes are then applied to evaluate the performance of the BCFBP-PCC system. Based on the life cycle assessment, a novel economy and CO2 reduction dual-objective operating optimization approach is proposed for the BCFBP-PCC to find the optimal hourly power generation and CO2 capture level of the plant under given market conditions. The static investment payback period is employed as a constraint in the optimization to narrow down the range of the solution set and provide clearer guidance for system operation. This paper provides the first work pioneered the economic and negative carbon operation optimization of the BCFBP-PCC system.

N-doped hierarchically porous carbons prepared with the assistance of chemical blowing and in-situ hard template as highly efficient CO2 adsorbents: A combined experimental and theoretical study

In the current work, we presented the synthesis of N-doped hierarchically porous carbons (NDHPCs) through chemical activation of hierarchically structured precursor derived from polyvinylpyrrolidone (PVP) and magnesium acetate tetrahydrate. Magnesium acetate tetrahydrate served as the blowing agent, and its decomposition product MgO served as the in-situ formed hard template. Combined with KHCO3 activation, the NDHPCs demonstrated a unique micro-meso-macroporous structure. Owing to the highly porous structure (1560–2545 m2/g) and enriched N-doping (1.48–6.31 wt%), the NDHPCs were investigated as potential CO2 adsorbents in both post-combustion capture and pre-combustion capture applications. When the adsorption temperature was 25 °C, the samples showed outstanding capture performances at both 1 bar (2.97–3.88 mmol/g) and 20 bar (13.24–19.89 mmol/g). The adsorption performances were further analyzed with grand canonical Monte Carlo (GCMC) simulation. Effects of various physicochemical properties on CO2 adsorption at different pressures were thus revealed with a combined experimental-theoretical approach.

Two-dimensional interfacial enhanced CO2 adsorption performance of porous organic amine solids: Structure-activity relationships and DFT calculations

The utilization of inexpensive and efficient amine-functionalized adsorbents has become a research hotspot in post-combustion capture technology. Meanwhile, the structure of the support and the selection of organic amines are the primary considerations affecting the CO2 adsorption performance. Herein, the novel solid amine adsorbent materials with amine-support interfacial effect were successfully synthesized in this study by loading four organic amines (TETA, TEPA, PEHA, and PEI) onto expanded vermiculite (EVMT) support with the layered structure. The results indicated that EVMT-50TETA exhibited superior CO2 adsorption capacity (132.5 mg/g) along with effective regeneration capability. This was attributed to the unique layered structure of EVMT that facilitates the dispersion of TETA on its surface or between layers as well as the formation of hydrogen bonds between surface functional groups (–OH) and amines to enhance the amine-support interfacial interaction. Furthermore, the minimal volume expansion of TETA during CO2 adsorption enables improved diffusion of CO2 in channels and enhanced accessibility to active sites. DFT calculations show higher binding energies and faster CO2 adsorption-diffusion rates between TETA and EVMT support. In situ DRIFTS experiments revealed that the process of CO2 adsorption followed the zwitterion mechanism, in which the zwitterion can be reversibly deprotonated to form ammonium carbamate and carbamic acid. This study provides comprehensive insights into the supports and amines interfacial effects through systematic investigation, offering both simplified synthesis strategies and profound theoretical support for studying solid amine adsorbents.

Gas Turbine's Role in Energy Transition

Abstract cycle configuration, with rated efficiencies (at ISO base load) above 60% net LHV, are expected to play a significant role in reducing the carbon footprint of utility scale electricity generation. Even without post-combustion capture, simply switching from coal-fired generation to natural gas-fired generation reduces carbon dioxide emissions by 60% (on a kg per MWh of generation basis). In simple cycle mode, with efficiencies above 40% net LHV and startup times around 20 minutes, 300 to 400+ MW gas turbines can easily serve as peakers to support variable renewable resources, i.e., wind and solar. In this paper, a close quantitative look is taken at the capabilities of gas turbines firing natural gas, hydrogen, or a blend thereof, both in simple and combined cycle configurations. Furthermore, using published data, first-principles calculations, and software simulations, it will be shown that the gas turbine constitutes an efficient and cost-effective technology, with and without carbon capture, as a key player in decarbonization of the electric power sector.

High accuracy prediction of the post-combustion carbon capture process parameters using the Decision Forest approach

This paper investigates the relationships among the important process parameters that impact Post-combustion Carbon Capture (PCC) carbon dioxide (CO2) separation. A better understanding of the complex relationships among those parameters can support optimization and performance enhancement of the separation process. Being able to precisely predict the process parameters will enable the operator to determine the current state of the process, forecast any potential changes or events, and adjust process parameters to enhance the plant's performance. With the objective of studying the process parameters' correlations in the amine-based PCC process, we modeled the multi-year historical production data of the Clean Energy Technologies Research Institute (CETRi) (formerly known as the International Test Center for PCC or ITC) in Regina, Saskatchewan, Canada, using a Decision Forest approach. The model validation process revealed that the Decision Forest model produced higher predictive accuracy than previous efforts. The Decision Forest models we developed also represent knowledge about the importance of parameters involved in the capture process, and such knowledge is useful for further optimization of the capture process in the future.

Linker-exchanged zeolitic imidazolate framework membranes for efficient CO2 separation

Metal organic framework (MOF) membranes have exhibited great potential for efficient gas separation owing to their excellent chemical and structural tunability. To realize CO2 separation from flue gas, linker modification or exchange is generally required to functionalize MOF membranes. However, the reported linker-exchanged polycrystalline MOF membranes have not yet achieved attractive CO2 separation performance due to the sacrificed permeance of the overly reduced pore apertures when employing bulky linkers. Herein, we report a 3-amino-1,2,4-triazole (Atz)-exchanged polycrystalline ZIF-8 membrane (Atz-ZIF-8) with Atz molar ratios ranging from 3% to 29% which shows an excellent CO2/N2 separation performance that significantly surpasses that of other linker-exchanged ZIF-8 membranes. The as-synthesized Atz-ZIF-8 membranes possess additional uncoordinated amines for CO2-preferential adsorption, resulting in an excellent CO2/N2 selectivity of 29. What's more, the size and configuration of Atz is similar to 2-methylimidazole (2-mIm), so the window size of Atz-ZIF-8 membranes is not significantly reduced, and thus high CO2 permeance (690 GPU) is achieved. Considering the superior performance and accessible manufacturing process, we conclude that our work could provide guidelines on designing advanced linker-exchanged ZIF-8 based polycrystalline membranes towards post-combustion carbon capture.

Greater Energy Independence with Sustainable Steel Production

Global energy market price volatility and an upward trajectory of prices per unit of electricity have sent all industrial sectors and many economies to the brink of recession. Alongside the urgent need for decarbonisation of all industries, achieving a globally higher level of energy independence across all sectors seems imperative. A multi-disciplinary approach with a proposed system of CO2 emissions reduction and capture technologies has the potential for short-term emissions reduction to near-zero in the steel industry—although some of the mechanisms can be implemented across most heavy industries. The findings of this research show a CO2 emissions reduction of ~30% from 977 t of CO2 to 684 t in one single blast furnace production cycle (based on 330 tonnes of liquid iron production capacity, with the mean of 2.1–3.2 tonnes CO2/t of steel and chemical reactions emissions applied), by switching the electricity provider for operating the electric heaters to providers generating energy exclusively from renewable sources. Replacing coal with biomass and adding post-combustion capture units to the blast furnace operation, will add carbon neutrality into the process—resulting in CO2 emissions reduction to near-zero. Carbon capture from biomass utilisation (BECCS) will add the benefit of carbon-negative emissions to the cycle. Simultaneously, energy-saving and process improvement measures implementation (up to 60% efficiency increase), excess heat recovery <30% of energy savings, and retrofitting renewable energy technology resulted in an energy independence of 88%. Engineering solutions, partly subsidised in the UK, are readily available for implementation in the iron and steel manufacturing industry.

Scaling up 3D printed hybrid sorbents towards (cost) effective post-combustion CO2 capture: A multiscale study

A 3D-printed sorbent containing polyethylene-imine and multi-walled carbon nanotubes (PEI-MWCNT) was studied for post-combustion carbon capture. In this work, the adsorbent was printed on a kg scale and characterized for CO2 adsorption through lab experiments. A 6-step VSA process was simulated using the lab data to capture CO2 from a representative 800 MW power plant. The adsorbent captured >70 % of the CO2 and 95 % CO2 purity was achieved. The levelized cost of electricity (LCOE) was 130.2 $/MWh and the costs of CO2 captured and avoided were 80 and 100.12 $/tonne. However, a zeolite 13X-activated carbon (13X-AC) monolith achieved a lower LCOE of 118.1 $/MWh, with the captured and avoided costs being 63 and 78.4 $/tonne, respectively. The LCOE value for the 13X-AC monolith was 5.1 % lower than a reference-packed bed system with Zeolite 13X pellets. The corresponding cost values were lower by 9.1 % and 13.9 %, respectively for the costs of CO2 captured and avoided. The lab experiments on the PEI-MWCNT sorbent revealed that further work is necessary to improve the thermal stability and stability with long-term storage of the precursor paste.

Pressurized Chemical Looping for Direct Reduced Iron Production: Economics of Carbon Neutral Process Configurations

The replacement of the blast furnace—basic oxygen furnace (BF-BOF) steelmaking route with the direct reduced iron—electric arc furnace (DRI-EAF) route reduces the direct CO2 emissions from steelmaking by up to 68%; however, the DRI shaft furnace is one of the largest remaining point source emitters in steelmaking. The capital and operating expenses of two potential nearly carbon-neutral DRI process configurations were investigated as a modification to a standard Midrex DRI facility. First, amine-based post-combustion capture with a 95% capture rate was considered as the benchmark, as it is currently commercially available. A second, novel configuration integrated the Midrex process with pressurized chemical looping—direct reduced iron (PCL-DRI) production. The capital expenditures were 71% and 28% higher than the standard Midrex process for a Midrex + amine capture plant, and a PCL-DRI plant, respectively. There was an incremental variable operating cost of USD 103 and USD 44 per tonne of CO2 for DRI production using amine capture and PCL-DRI, respectively. The amine capture configuration is most sensitive to the cost of steam generation, while PCL-DRI is more sensitive to the cost of electricity and the makeup oxygen carrier. An iron-based natural ore is recommended for PCL-DRI due to the low cost and availability. Based on the lower costs compared to amine-based post-combustion capture, PCL-DRI is an attractive means of eliminating CO2 emissions from DRI production.

Biochar-mediated release of CO2 from monoethanolamine/H2O solution with low energy requirement over ZrO2/SiO2/biochar ternary catalysts

CO2 absorption technology based on amine solutions has sustained appeal due to its high efficiency in post-combustion capture of CO2. However, the high energy penalty of solvent regeneration limits its large-scale industrial application. Therefore, designing inexpensive catalysts to reduce solvent regeneration energy consumption remains challenging. This study reports a recyclable ternary catalyst, ZrO2/SiO2/biochar, which was synthesized by co-pyrolysis of zirconium oxychloride and wheat flour in the presence of SiO2 nanoparticles. The incorporation of biochar improved the distribution of Lewis acidic sites (LAS) and Brønsted acidic sites (BAS). The improved BASs and LASs of ZrO2/SiO2/biochar catalyst were conductive to donate protons or accept electrons and thus, the amount and rate of CO2 desorption from CO2-saturated monoethanolamine (90 °C) were more than 24% and 26% higher, respectively, to compare with the catalyst-free system at the same conditions. As a result, the energy penalty was decreased by about 31%. A biochar-mediated proton-transfer mechanism that the presence of biochar increased the mesoporous proportion, the BAS and L/B ratio as well as the favorable charge transfer was inferred for the ZrO2/SiO2/biochar-catalyzed CO2 release through experimental evidence. The results reveal the role of biochar in solid acid catalysts for CO2 desorption, which will provide a novel strategy for building solid acid catalysts to reduce energy requirements in CO2 capture.

Assessing economic trade-off for advances in amine-based post-combustion capture technology

The study aims to evaluate the trade-off relationship between reducing energy consumption through technological improvements, including process modifications and the use of CO2-absorbing solvents, and the increased costs associated with their implementation in power and industrial sectors. Additionally, the economic potentials of heat-integrated CO2 capture and amine solvent degradation are explored. Four representative cases are considered, involving changes to lean vapor compression (LVC) and a blended amine solvent from a monoethanolamine (MEA) benchmark process. The findings indicate that the characteristics of combustion processes have a minor impact on the energy intensity of amine-based CO2 capture, but they significantly affect its cost. This is primarily due to substantial variations in fuel costs and equipment size. Technological advancements, such as process modifications and the use of amine solvents with high CO2 absorption capacity, play a crucial role in reducing both the energy consumption and costs associated with CO2 capture. However, the study suggests that careful consideration is needed when utilizing expensive amine solvents with high CO2 absorption capacity, particularly in situations prone to solvent degradation, as solvent loss can significantly impact the economic viability of CO2 capture.

Optimizing post-combustion carbon capture: A comprehensive 3E analyses of energy, exergy, and exergoeconomic aspects with solar integration

The combination of capturing CO2 from power plants and storing it has the potential to mitigate the effects of fossil fuel usage on the climate. The reduction of CO2 emissions through CCS is recognized as a viable solution, but the significant challenge lies in the need to reduce costs and energy consumption in its development. A method that can be utilized to improve the energy efficiency of capture is the implementation of exergy-based analysis, which includes both exergetic and exergoeconomic analyses. This study aims to create an exergy-based assessment of a post-combustion CO2 capture with DGA 50 wt% solvent, using ASPEN HYSYS Version 11 for a Natural Gas-fired power plant with a capture rate of 90 %. The results show that through meticulous modifications in the system's configuration, including LVC, SSF, RVC, RSR, ICA, and their combinations, the reboiler's energy consumption was significantly reduced from 11.1 GJ/Ton CO2 to 3.27 GJ/Ton CO2, and the utility consumption was reduced by approximately 6,500$/h. Additionally, we compared various configurations in terms of exergy and exergoeconomic. The plant exergy efficiency improved from 44.9 % in the standard configuration to 68.3 % for the LVC + Solar configuration. Additionally, the exergoeconomic factor improved from 3.1 % to 3.8 %.

The relationship between oxidative degradation and ammonia emission of carbon capture amines based on their chemical structures

Abstract This work investigates the effect of chemical structural positioning of different functional groups in 29 amines covering primary, secondary and tertiary alkanolamines as well as multi-alkylamines and cyclic amines on both amine degradation and ammonia (NH3) emissions during post-combustion amine-based carbon dioxide capture. The results helped to elucidate possible relationships between degradation and emissions as related to the chemical structure of the amine. The results showed that longer alkyl chain lengths in multi-alkylamines caused a more drastic decrease in both degradation and NH3 emissions followed by secondary alkanolamines. The decrease in those activities for primary and tertiary alkanolamines as well as cyclic amines was low and more so for NH3 emissions. In contrast, the increase in hydroxyl groups in secondary alkanolamines caused a drastic increase in degradation and NH3 emissions. On the other hand, having more hydroxyl groups in sterically hindered primary and tertiary alkanolamines caused a more drastic decrease in degradation and a smaller decrease in NH3 emissions due to the steric hindrance within their structure. An increase in the number of amino groups in an amine caused an increase in both degradation and NH3 emission rates because these provided the reactive sites for the formation of free radicals. This effect was not as large in alkyl-cyclic amines as in multi-alkylamines due to the ability of the former to resist oxidative degradation. Furthermore, branched alkyl groups between amino and hydroxyl groups more drastically increased both the degradation and NH3 emission activities than branched alkyl groups located at the nitrogen atom.

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).