Special Issue "Gas Capture Processes"

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: closed (15 September 2019).

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A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Tohid N. Borhani
E-Mail Website
Guest Editor
School of Engineering, Division of Chemical Engineering, University of Wolverhampton, Wolverhampton WV1 1LY, UK
Interests: process modeling and simulation; chemometric and AI; energy conversion and storage
Special Issues and Collections in MDPI journals
Dr. Zhien Zhang
E-Mail Website
Guest Editor
William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH 43210, USA
Interests: Carbon Capture Utilization and Storage (CCUS); gas separation; membrane; polymer; absorption; process modeling; mass transfer; heat transfer; fossil fuel; renewable energy; hydrate; wastewater treatment
Special Issues and Collections in MDPI journals
Prof. Dr. Muftah H. El-Naas
E-Mail Website
Guest Editor
Gas Processing Center, Qatar Unviersity, P.O. Box 2713, Doha, Qatar
Interests: water treatment and purification; biotechnology; electrocoagulation; CO2 capture and utilization; membrane separation and plasma technology
Special Issues and Collections in MDPI journals
Dr. Salman Masoudi Soltani
E-Mail Website
Guest Editor
Department of Chemical Engineering, College of Engineering, Design and Physical Sciences, Brunel University London, Uxbridge UB8 3PH, UK
Interests: Separation Processes; Process Synthesis and Design; Carbon Capture and Utilisation
Special Issues and Collections in MDPI journals
Dr. Yunfei Yan
E-Mail Website
Guest Editor
Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University, Chongqing 400044, China
Interests: pollution control; mass and heat transfer; combustion; multiphase flow

Special Issue Information

Dear Colleagues,

Gas emissions from industries and human activities represent a global threat to the atmosphere and human health. Recently, gas emissions control technologies have been employed widely in a variety of fields, such as CO2, CO, SO2, H2S, NOX, H2, etc. However, in the specific areas, some capturing methods show poor performance not only in term of cost but also in terms of energy consumptions. Thus, the choice of a good gas capture method is very significant to the various industrial processes and the small-scale applications. It is important to conduct the proper analysis of the main factors that influence the process and identify the mechanisms of the different phases of the processes.

This Special Issue on “Gas Capture Processes” aims to identify novel advances in the development and application of experimental and modeling work to address longstanding challenges in gas capture processes. Topics include, but are not limited to, the following:

  • Gas separation from gas mixture;
  • Optimization and comparison of the gas capture processes;
  • Mechanism and thermodynamics of CO2 and other phases;
  • Multiphase flow during the capturing process; and
  • The development of gas capture applications.

Dr. Tohid N.Borhani
Dr. Zhien Zhang
Dr. Muftah H. El-Naas
Dr. Salman Masoudi Soltani
Dr. Yunfei Yan
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs). Please note that for papers submitted after 31 December 2019 an APC of 1400 CHF applies. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Air pollution
  • Gas separation
  • Gas capture
  • Process optimization

Published Papers (26 papers)

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Editorial

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Editorial
Gas Capture Processes
Processes 2020, 8(1), 70; https://doi.org/10.3390/pr8010070 - 04 Jan 2020
Viewed by 1223
Abstract
The increasing trends in gas emissions have had direct adverse impacts on human health and ecological habitats in the world. A variety of technologies have been deployed to mitigate the release of such gases, including CO2, CO, SO2, H [...] Read more.
The increasing trends in gas emissions have had direct adverse impacts on human health and ecological habitats in the world. A variety of technologies have been deployed to mitigate the release of such gases, including CO2, CO, SO2, H2S, NOx and H2. This special issue on gas-capture processes collects 25 review and research papers on the applications of novel techniques, processes, and theories in gas capture and removal. Full article
(This article belongs to the Special Issue Gas Capture Processes)

Research

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Article
Experimental Study on Spray Breakup in Turbulent Atomization Using a Spiral Nozzle
Processes 2019, 7(12), 911; https://doi.org/10.3390/pr7120911 - 03 Dec 2019
Cited by 1 | Viewed by 1277
Abstract
Spiral nozzles are widely used in wet scrubbers to form an appropriate spray pattern to capture the polluting gas/particulate matterwith the highest possible efficiency. Despite this fact, and a fact that it is a nozzle with a very atypical spray pattern (a full [...] Read more.
Spiral nozzles are widely used in wet scrubbers to form an appropriate spray pattern to capture the polluting gas/particulate matterwith the highest possible efficiency. Despite this fact, and a fact that it is a nozzle with a very atypical spray pattern (a full cone consisting of three concentric hollow cones), very limited amount of studies have been done so far on characterization of this type of nozzle. This work reports preliminary results on the spray characteristics of a spiral nozzle used for gas absorption processes. First, we experimentally measured the pressure impact footprint of the spray generated. Then effective spray angles were evaluated from the photographs of the spray and using the pressure impact footprint records via Archimedean spiral equation. Using the classical photography, areas of primary and secondary atomization were determined together with the droplet size distribution, which were further approximated using selected distribution functions. Radial and tangential spray velocity of droplets were assessed using the laser Doppler anemometry. The results show atypical behavior compared to different types of nozzles. In the investigated measurement range, the droplet-size distribution showed higher droplet diameters (about 1 mm) compared to, for example, air assisted atomizers. It was similar for the radial velocity, which was conversely lower (max velocity of about 8 m/s) compared to, for example, effervescent atomizers, which can produce droplets with a velocity of tens to hundreds m/s. On the contrary, spray angle ranged from 58° and 111° for the inner small and large cone, respectively, to 152° for the upper cone, and in the measured range was independent of the inlet pressure of liquid at the nozzle orifice. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Theoretical and Experimental Insights into the Mechanism for Gas Separation through Nanochannels in 2D Laminar MXene Membranes
Processes 2019, 7(10), 751; https://doi.org/10.3390/pr7100751 - 15 Oct 2019
Cited by 7 | Viewed by 1076
Abstract
Clarifying the mechanism for the gas transportation in the emerging 2D materials-based membranes plays an important role on the design and performance optimization. In this work, the corresponding studies were conducted experimentally and theoretically. To this end, we measured the gas permeances of [...] Read more.
Clarifying the mechanism for the gas transportation in the emerging 2D materials-based membranes plays an important role on the design and performance optimization. In this work, the corresponding studies were conducted experimentally and theoretically. To this end, we measured the gas permeances of hydrogen and nitrogen from their mixture through the supported MXene lamellar membrane. Knudsen diffusion and molecular sieving through straight and tortuous nanochannels were proposed to elucidate the gas transport mechanism. The average pore diameter of 5.05 Å in straight nanochannels was calculated by linear regression in the Knudsen diffusion model. The activation energy for H2 transport in molecular sieving model was calculated to be 20.54 kJ mol−1. From the model, we can predict that the gas permeance of hydrogen (with smaller kinetic diameter) is contributed from both Knudsen diffusion and molecular sieving mechanism, but the permeance of larger molecular gases like nitrogen is sourced from Knudsen diffusion. The effects of the critical conditions such as temperature, the diffusion pore diameter of structural defects, and the thickness of the prepared MXene lamellar membrane on hydrogen and nitrogen permeance were also investigated to understand the hydrogen permeation difference from Knudsen diffusion and molecular sieving. At room temperature, the total hydrogen permeance was contributed 18% by Knudsen diffusion and 82% by molecular sieving. The modeling results indicate that molecular sieving plays a dominant role in controlling gas selectivity. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Siderite Formation by Mechanochemical and High Pressure–High Temperature Processes for CO2 Capture Using Iron Ore as the Initial Sorbent
Processes 2019, 7(10), 735; https://doi.org/10.3390/pr7100735 - 14 Oct 2019
Cited by 4 | Viewed by 662
Abstract
Iron ore was studied as a CO2 absorbent. Carbonation was carried out by mechanochemical and high temperature–high pressure (HTHP) reactions. Kinetics of the carbonation reactions was studied for the two methods. In the mechanochemical process, it was analyzed as a function of [...] Read more.
Iron ore was studied as a CO2 absorbent. Carbonation was carried out by mechanochemical and high temperature–high pressure (HTHP) reactions. Kinetics of the carbonation reactions was studied for the two methods. In the mechanochemical process, it was analyzed as a function of the CO2 pressure and the rotation speed of the planetary ball mill, while in the HTHP process, the kinetics was studied as a function of pressure and temperature. The highest CO2 capture capacities achieved were 3.7341 mmol of CO2/g of sorbent in ball milling (30 bar of CO2 pressure, 400 rpm, 20 h) and 5.4392 mmol of CO2/g of absorbent in HTHP (50 bar of CO2 pressure, 100 °C and 4 h). To overcome the kinetics limitations, water was introduced to all carbonation experiments. The calcination reactions were studied in Argon atmosphere using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. Siderite can be decomposed at the same temperature range (100 °C to 420 °C) for the samples produced by both methods. This range reaches higher temperatures compared with pure iron oxides due to decomposition temperature increase with decreasing purity. Calcination reactions yield magnetite and carbon. A comparison of recyclability (use of the same material in several cycles of carbonation–calcination), kinetics, spent energy, and the amounts of initial material needed to capture 1 ton of CO2, revealed the advantages of the mechanochemical process compared with HTHP. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Effect of Physical and Mechanical Activation on the Physicochemical Structure of Coal-Based Activated Carbons for SO2 Adsorption
Processes 2019, 7(10), 707; https://doi.org/10.3390/pr7100707 - 05 Oct 2019
Cited by 4 | Viewed by 815
Abstract
The SO2 adsorption efficiency of activated carbons (ACs) is clearly dependent on its physicochemical structure. Related to this, the effect of physical and mechanical activation on the physicochemical structure of coal-based ACs has been investigated in this work. In the stage of [...] Read more.
The SO2 adsorption efficiency of activated carbons (ACs) is clearly dependent on its physicochemical structure. Related to this, the effect of physical and mechanical activation on the physicochemical structure of coal-based ACs has been investigated in this work. In the stage of CO2 activation, the rapid decrease of the defective structure and the growth of aromatic layers accompanied by the dehydrogenation of aromatic rings result in the ordered conversion of the microstructure and severe carbon losses on the surfaces of Char-PA, while the oxygen content of Char-PA, including C=O (39.6%), C–O (27.3%), O–C=O (18.4%) and chemisorbed O (or H2O) (14.7%), is increased to 4.03%. Char-PA presents a relatively low SBET value (414.78 m2/g) owing to the high value of Non-Vmic (58.33%). In the subsequent mechanical activation from 12 to 48 h under N2 and dry ice, the strong mechanical collision caused by ball-milling can destroy the closely arranged crystalline layers and the collapse of mesopores and macropores, resulting in the disordered conversion of the microstructure and the formation of a defective structure, and a sustained increase in the SBET value from 715.89 to 1259.74 m2/g can be found with the prolonging of the ball-milling time. There is a gradual increase in the oxygen content from 6.79 to 9.48% for Char-PA-CO2-12/48 obtained by ball-milling under CO2. Remarkably, the varieties of physicochemical parameters of Char-PA-CO2-12/48 are more obvious than those of Char-PA-N2-12/48 under the same ball-milling time, which is related to the stronger solid-gas reactions caused by the mechanical collision under dry ice. Finally, the results of the SO2 adsorption test of typical samples indicate that Char-PA-CO2-48 with a desirable physicochemical structure can maintain 100% efficiency within 30 min and that its SO2 adsorption capacity can reach 138.5 mg/g at the end of the experiment. After the 10th cycle of thermal regeneration, Char-PA-CO2-48 still has a strong adsorptive capacity (81.2 mg/g). Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Highly Selective CO2 Capture on Waste Polyurethane Foam-Based Activated Carbon
Processes 2019, 7(9), 592; https://doi.org/10.3390/pr7090592 - 03 Sep 2019
Cited by 8 | Viewed by 1382
Abstract
Low-cost activated carbons were prepared from waste polyurethane foam by physical activation with CO2 for the first time and chemical activation with Ca(OH)2, NaOH, or KOH. The activation conditions were optimized to produce microporous carbons with high CO2 adsorption [...] Read more.
Low-cost activated carbons were prepared from waste polyurethane foam by physical activation with CO2 for the first time and chemical activation with Ca(OH)2, NaOH, or KOH. The activation conditions were optimized to produce microporous carbons with high CO2 adsorption capacity and CO2/N2 selectivity. The sample prepared by physical activation showed CO2/N2 selectivity of up to 24, much higher than that of chemical activation. This is mainly due to the narrower microporosity and the rich N content produced during the physical activation process. However, physical activation samples showed inferior textural properties compared to chemical activation samples and led to a lower CO2 uptake of 3.37 mmol·g−1 at 273 K. Porous carbons obtained by chemical activation showed a high CO2 uptake of 5.85 mmol·g−1 at 273 K, comparable to the optimum activated carbon materials prepared from other wastes. This is mainly attributed to large volumes of ultra-micropores (<1 nm) up to 0.212 cm3·g−1 and a high surface area of 1360 m2·g−1. Furthermore, in consideration of the presence of fewer contaminants, lower weight losses of physical activation samples, and the excellent recyclability of both physical- and chemical-activated samples, the waste polyurethane foam-based carbon materials exhibited potential application prospects in CO2 capture. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Adsorption of NO Gas Molecules on Monolayer Arsenene Doped with Al, B, S and Si: A First-Principles Study
Processes 2019, 7(8), 538; https://doi.org/10.3390/pr7080538 - 15 Aug 2019
Cited by 4 | Viewed by 1280
Abstract
The structures and electronic properties of monolayer arsenene doped with Al, B, S and Si have been investigated based on first-principles calculation. The dopants have great influences on the properties of the monolayer arsenene. The electronic properties of the substrate are effectively tuned [...] Read more.
The structures and electronic properties of monolayer arsenene doped with Al, B, S and Si have been investigated based on first-principles calculation. The dopants have great influences on the properties of the monolayer arsenene. The electronic properties of the substrate are effectively tuned by substitutional doping. After doping, NO adsorbed on four kinds of substrates were investigated. The results demonstrate that NO exhibits a chemisorption character on Al-, B- and Si-doped arsenene while a physisorption character on S-doped arsenene with moderate adsorption energy. Due to the adsorption of NO, the band structures of the four systems have great changes. It reduces the energy gap of Al- and B-doped arsenene and opens the energy gap of S- and Si-doped arsenene. The large charge depletion between the NO molecule and the dopant demonstrates that there is a strong hybridization of orbitals at the surface of the doped substrate because of the formation of a covalent bond, except for S-doped arsenene. It indicates that Al-, B- and Si-doped arsenene might be good candidates as gas sensors to detect NO gas molecules owning to their high sensitivity. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Formation and Evolution Mechanism for Carbonaceous Deposits on the Surface of a Coking Chamber
Processes 2019, 7(8), 508; https://doi.org/10.3390/pr7080508 - 03 Aug 2019
Cited by 3 | Viewed by 1287
Abstract
This work aimed to investigate the carbonaceous deposits on the surface of the coking chamber. Scanning electron microscopy (SEM), X-ray fluorescence spectrum (XRF), Fourier transform infrared spectrometer (FTIR), Raman spectroscopy, X-ray diffraction spectrum (XRD), and X-ray photoelectron spectroscopy (XPS) were applied to investigate [...] Read more.
This work aimed to investigate the carbonaceous deposits on the surface of the coking chamber. Scanning electron microscopy (SEM), X-ray fluorescence spectrum (XRF), Fourier transform infrared spectrometer (FTIR), Raman spectroscopy, X-ray diffraction spectrum (XRD), and X-ray photoelectron spectroscopy (XPS) were applied to investigate the carbonaceous deposits. FTIR revealed the existence of carboxyl, hydroxyl, and carbonyl groups in the carbonaceous deposits. SEM showed that different carbonaceous deposit layers presented significant differences in morphology. XRF and XPS revealed that the carbonaceous deposits mainly contained C, O, and N elements, with smaller amounts of Al, Si, and Ca elements. It was found that in the formation of carbonaceous deposits, the C content gradually increased while the O and N elements gradually decreased. It was also found that the absorbed O2 and H2O took part in the oxidation process of the carbon skeleton to form the =O and –O– structure. The oxidation and elimination reaction resulted in change in the bonding state of the O element, and finally formed compact carbonaceous deposits on the surface of the coking chamber. Based on the analysis, the formation and evolution mechanisms of carbonaceous deposits were discussed. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Modeling and Simulation of the Absorption of CO2 and NO2 from a Gas Mixture in a Membrane Contactor
Processes 2019, 7(7), 441; https://doi.org/10.3390/pr7070441 - 11 Jul 2019
Cited by 7 | Viewed by 1429
Abstract
The removal of undesirable compounds such as CO2 and NO2 from incineration and natural gas is essential because of their harmful influence on the atmosphere and on the reduction of natural gas heating value. The use of membrane contactor for the [...] Read more.
The removal of undesirable compounds such as CO2 and NO2 from incineration and natural gas is essential because of their harmful influence on the atmosphere and on the reduction of natural gas heating value. The use of membrane contactor for the capture of the post-combustion NO2 and CO2 had been widely considered in the past decades. In this study, membrane contactor was used for the simultaneous absorption of CO2 and NO2 from a mixture of gas (5% CO2, 300 ppm NO2, balance N2) with aqueous sodium hydroxide solution. For the first time, a mathematical model was established for the simultaneous removal of the two undesired gas solutes (CO2, NO2) from flue gas using membrane contactor. The model considers the reaction rate, and radial and axial diffusion of both compounds. The model was verified and validated with experimental data and found to be in good agreement. The model was used to examine the effect of the flow rate of liquid, gas, and inlet solute mole fraction on the percent removal and molar flux of both impurity species. The results revealed that the effect of the liquid flow rate improves the percent removal of both compounds. A high inlet gas flow rate decreases the percent removal. It was possible to obtain the complete removal of both undesired compounds. The model was confirmed to be a dependable tool for the optimization of such process, and for similar systems. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
The Effect of Various Nanofluids on Absorption Intensification of CO2/SO2 in a Single-Bubble Column
Processes 2019, 7(7), 393; https://doi.org/10.3390/pr7070393 - 26 Jun 2019
Cited by 10 | Viewed by 1266
Abstract
Application of nanoparticles in aqueous base-fluids for intensification of absorption rate is an efficient method for absorption progress within the system incorporating bubble-liquid process. In this research, SO2 and CO2 were separately injected as single raising bubbles containing nanofluids to study [...] Read more.
Application of nanoparticles in aqueous base-fluids for intensification of absorption rate is an efficient method for absorption progress within the system incorporating bubble-liquid process. In this research, SO2 and CO2 were separately injected as single raising bubbles containing nanofluids to study the impact of nanoparticle effects on acidic gases absorption. In order to do this, comprehensive experimental studies were done. These works also tried to investigate the effect of different nanofluids such as water/Al2O3 or water/Fe2O3 or water/SiO2 on the absorption rate. The results showed that the absorption of CO2 and SO2 in nanofluids significantly increases up to 77 percent in comparison with base fluid. It was also observed that the type of gas molecules and nanoparticles determine the mechanism of mass transfer enhancement by nanofluids. Additionally, our findings indicated that the values of mass transfer coefficient of SO2 in water/Al2O3, water/Fe2O3 and water/SiO2 nanofluids are, respectively, 50%, 42% and 71% more than those of SO2 in pure water ( k L SO 2 w a t e r = 1.45 × 10 4   m / s ). Moreover, the values for CO2 in above nanofluids were, respectively, 117%, 103% and 88% more than those of CO2 in water alone ( k L CO 2 w a t e r = 1.03 × 10 4   m / s ). Finally, this study tries to offer a new comprehensive correlation for mass transfer coefficient and absorption rate prediction. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Exergy Analysis and Evaluation of the Different Flowsheeting Configurations for CO2 Capture Plant Using 2-Amino-2-Methyl-1-Propanol (AMP)
Processes 2019, 7(6), 391; https://doi.org/10.3390/pr7060391 - 24 Jun 2019
Cited by 2 | Viewed by 1650
Abstract
This paper presents steady-state simulation and exergy analysis of the 2-amino-2-methyl-1-propanol (AMP)-based post-combustion capture (PCC) plant. Exergy analysis provides the identification of the location, sources of thermodynamic inefficiencies, and magnitude in a thermal system. Furthermore, thermodynamic analysis of different configurations of the process [...] Read more.
This paper presents steady-state simulation and exergy analysis of the 2-amino-2-methyl-1-propanol (AMP)-based post-combustion capture (PCC) plant. Exergy analysis provides the identification of the location, sources of thermodynamic inefficiencies, and magnitude in a thermal system. Furthermore, thermodynamic analysis of different configurations of the process helps to identify opportunities for reducing the steam requirements for each of the configurations. Exergy analysis performed for the AMP-based plant and the different configurations revealed that the rich split with intercooling configuration gave the highest exergy efficiency of 73.6%, while that of the intercooling and the reference AMP-based plant were 57.3% and 55.8% respectively. Thus, exergy analysis of flowsheeting configurations can lead to significant improvements in plant performance and lead to cost reduction for amine-based CO2 capture technologies. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Optimization of Post Combustion CO2 Capture from a Combined-Cycle Gas Turbine Power Plant via Taguchi Design of Experiment
Processes 2019, 7(6), 364; https://doi.org/10.3390/pr7060364 - 12 Jun 2019
Cited by 4 | Viewed by 2075
Abstract
The potential of carbon capture and storage to provide a low carbon fossil-fueled power generation sector that complements the continuously growing renewable sector is becoming ever more apparent. An optimization of a post combustion capture unit employing the solvent monoethanolamine (MEA) was carried [...] Read more.
The potential of carbon capture and storage to provide a low carbon fossil-fueled power generation sector that complements the continuously growing renewable sector is becoming ever more apparent. An optimization of a post combustion capture unit employing the solvent monoethanolamine (MEA) was carried out using a Taguchi design of experiment to mitigate the parasitic energy demands of the system. An equilibrium-based approach was employed in Aspen Plus to simulate 90% capture of the CO2 emitted from a 600 MW natural gas combined-cycle gas turbine power plant. The effects of varying the inlet flue gas temperature, absorber column operating pressure, amount of exhaust gas recycle, and amine concentration were evaluated using signal to noise ratios and analysis of variance. The optimum levels that minimized the specific energy requirements were a: flue gas temperature = 50 °C; absorber pressure = 1 bar; exhaust gas recirculation = 20% and; amine concentration = 35 wt%, with a relative importance of: amine concentration > absorber column pressure > exhaust gas recirculation > flue gas temperature. This configuration gave a total capture unit energy requirement of 5.05 GJ/tonneCO2, with an energy requirement in the reboiler of 3.94 GJ/tonneCO2. All the studied factors except the flue gas temperature, demonstrated a statistically significant association to the response. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Optimal Design of a Carbon Dioxide Separation Process with Market Uncertainty and Waste Reduction
Processes 2019, 7(6), 342; https://doi.org/10.3390/pr7060342 - 05 Jun 2019
Cited by 4 | Viewed by 1043
Abstract
The aim of this work is to optimize the conceptual design of an amine-based carbon dioxide (CO2) separation process for Enhanced Oil Recovery (EOR). A systematic approach is applied to predict the economic profitability of the system while reducing the environmental [...] Read more.
The aim of this work is to optimize the conceptual design of an amine-based carbon dioxide (CO2) separation process for Enhanced Oil Recovery (EOR). A systematic approach is applied to predict the economic profitability of the system while reducing the environmental impacts. Firstly, we model the process with UniSim and determine the governing degrees of freedom (DoF) through a sensitivity analysis. Then, we proceed with the formulation of the economic problem, where the employment of econometric models allows us to predict the highest dynamic economic potential (DEP). In the second part, we apply the Waste Reduction (WAR) algorithm to quantify the environmental risks of the studied process. This method is based on the minimization of the potential environmental indicator (PEI) by using the generalization of the Waste Reduction algorithm. Results show that the CO2 separation plant is promising in terms of economic revenues. However, the PEI value indicates that the higher the profitability, the larger the environmental risk. The optimal value of the DEP corresponds to 0.0274 kmol/h and 60 °C, with a plant capacity according to the mole flow rate of the produced acid gas. In addition, the highest environmental risk is observed at the upper bounds of the DoF. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Catalytic Effect of NaCl on the Improvement of the Physicochemical Structure of Coal-Based Activated Carbons for SO2 Adsorption
Processes 2019, 7(6), 338; https://doi.org/10.3390/pr7060338 - 05 Jun 2019
Cited by 6 | Viewed by 1061
Abstract
The utilization of coal-based activated carbons focuses on improving the physicochemical structure for achieving high-capacity. Herein, the catalytic effect of NaCl (1 and 3 wt%) in the presence of oxygen functional groups on the improvement of the physicochemical structure of coal-based activated carbons [...] Read more.
The utilization of coal-based activated carbons focuses on improving the physicochemical structure for achieving high-capacity. Herein, the catalytic effect of NaCl (1 and 3 wt%) in the presence of oxygen functional groups on the improvement of the physicochemical structure of coal-based activated carbons is studied in this work. A large quantity of Na can be retained in 1NaJXO and 3NaJXO with the presence of oxygen functional groups to promote further its catalytic characteristics during pyrolysis, resulting in the disordered transformation of the carbon structure. In addition, the development of micropores is mainly affected by the distribution and movement of Na catalyst, whereas the growth of mesopores is mainly influenced by the evolution of oxygen functional groups. Then, the active sites of 3NaJXO-800 can no longer be consumed preferentially in the presence of Na catalyst during subsequent CO2 activation to facilitate the sustained disordered conversion of the microstructure and the rapid development of the micropores, resulting in the obvious high SBET value as activation proceeds. And the high SBET/burn-off ratio value (41.48 m2∙g−1/%) of 3NaJXO-800 with a high value of SBET (1995.35 m2∙g−1) at a low burn-off value (48.1%) can be obtained, presenting the high efficiency of pore formation. Finally, the SO2 adsorption efficiency of 3NaJXO-800-48.1 maintains at 100% within 90 min. After 180 min, 3NaJXO-800-48.1 still presents a high adsorptive capacity (140.2 mg/g). It is observed that a large micropore volume in the case of hierarchical pore structure necessarily assures optimal adsorption of SO2. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Communication
Analysis of the Excess Hydrocarbon Gases Output from Refinery Plants
Processes 2019, 7(5), 253; https://doi.org/10.3390/pr7050253 - 01 May 2019
Cited by 2 | Viewed by 1007
Abstract
The article presents the ideas of maximizing recovery of flare gases in the industrial plants processing hydrocarbons. The functioning of a flare stack and depressurization systems in a typical refinery plant is described, and the architecture of the depressurization systems and construction of [...] Read more.
The article presents the ideas of maximizing recovery of flare gases in the industrial plants processing hydrocarbons. The functioning of a flare stack and depressurization systems in a typical refinery plant is described, and the architecture of the depressurization systems and construction of the flares are shown in a simplified way. The proposal to recover the flare gases together with their output outside the industrial plant, in order to minimize impact on the environment (reduction of emissions) and to limit consumption of fossil fuels is presented. Contaminants that may be found in the depressurization systems are indicated. The idea presented in the article assumes the injection of an excess stream of gases into an existing natural gas pipelines system. A method of monitoring is proposed, aiming to eliminate introduction of undesirable harmful components into the systems. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
The Influence of Sorption Pressure on Gas Diffusion in Coal Particles: An Experimental Study
Processes 2019, 7(4), 219; https://doi.org/10.3390/pr7040219 - 16 Apr 2019
Cited by 7 | Viewed by 1551
Abstract
Gas pressure changes during the process of coal mine gas drainage and CBM recovery. It is of great importance to understand the influence of sorption pressure on gas diffusion; however, the topic remains controversial in past studies. In this study, four samples with [...] Read more.
Gas pressure changes during the process of coal mine gas drainage and CBM recovery. It is of great importance to understand the influence of sorption pressure on gas diffusion; however, the topic remains controversial in past studies. In this study, four samples with different coal ranks were collected and diffusion experiments were conducted under different pressures through the adsorption and desorption processes. Three widely used models, i.e., the unipore diffusion (UD) model, the bidisperse diffusion (BD) model and the dispersive diffusion (DD) model, were adopted to compare the applicability and to calculate the diffusion coefficients. Results show that for all coal ranks, the BD model and DD model can match the experimental results better than the UD model. Concerning the fast diffusion coefficient Dae of the BD model, three samples display a decreasing trend with increasing gas pressure while the other sample shows a V-type trend. The slow diffusion coefficient Die of BD model increases with gas pressure for all samples, while the ratio β is an intrinsic character of coal and remains constant. For the DD model, the characteristic rate parameter kΦ does not change sharply and the stretching parameter α increases with gas pressure. Both Dae and Die are in proportion to kΦ, which reflect the diffusion rate of gas in the coal. The impacts of pore characteristic on gas diffusion were also analyzed. Although pore size distributions and specific surface areas are different in the four coal samples, correlations are not apparent between pore characteristic and diffusion coefficients. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Study of Various Aqueous and Non-Aqueous Amine Blends for Hydrogen Sulfide Removal from Natural Gas
Processes 2019, 7(3), 160; https://doi.org/10.3390/pr7030160 - 15 Mar 2019
Cited by 11 | Viewed by 2125
Abstract
Various novel amine solutions both in aqueous and non-aqueous [monoethylene glycol (MEG)/triethylene glycol(TEG)] forms have been studied for hydrogen sulfide (H2S) absorption. The study was conducted in a custom build experimental setup at temperatures relevant to subsea operation conditions and atmospheric [...] Read more.
Various novel amine solutions both in aqueous and non-aqueous [monoethylene glycol (MEG)/triethylene glycol(TEG)] forms have been studied for hydrogen sulfide (H2S) absorption. The study was conducted in a custom build experimental setup at temperatures relevant to subsea operation conditions and atmospheric pressure. Liquid phase absorbed H2S, and amine concentrations were measured analytically to calculate H2S loading (mole of H2S/mole of amine). Maximum achieved H2S loadings as the function of pKa, gas partial pressure, temperature and amine concentration are presented. Effects of solvent type on absorbed H2S have also been discussed. Several new solvents showed higher H2S loading as compared to aqueous N-Methyldiethanolamine (MDEA) solution which is the current industrial benchmark compound for selective H2S removal in natural gas sweetening process. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Reaction Kinetics of Carbon Dioxide in Aqueous Blends of N-Methyldiethanolamine and L-Arginine Using the Stopped-Flow Technique
Processes 2019, 7(2), 81; https://doi.org/10.3390/pr7020081 - 06 Feb 2019
Cited by 5 | Viewed by 1759
Abstract
Reduction of carbon dioxide emission from natural and industrial flue gases is paramount to help mitigate its effect on global warming. Efforts are continuously deployed worldwide to develop efficient technologies for CO2 capture. The use of environment friendly amino acids as rate [...] Read more.
Reduction of carbon dioxide emission from natural and industrial flue gases is paramount to help mitigate its effect on global warming. Efforts are continuously deployed worldwide to develop efficient technologies for CO2 capture. The use of environment friendly amino acids as rate promoters in the present amine systems has attracted the attention of many researchers recently. In this work, the reaction kinetics of carbon dioxide with blends of N-methyldiethanolamine and L-Arginine was investigated using stopped flow technique. The experiments were performed over a temperature range of 293 to 313 K and solution concentration up to one molar of different amino acid/amine ratios. The overall reaction rate constant (kov) was found to increase with increasing temperature and amine concentration as well as with increased proportion of L-Arginine concentration in the mixture. The experimental data were fitted to the zwitterion and termolecular mechanisms using a nonlinear regression technique with an average absolute deviation (AAD) of 7.6% and 8.0%, respectively. A comparative study of the promoting effect of L-Arginine with that of the effect of Glycine and DEA in MDEA blends showed that MDEA-Arginine blend exhibits faster reaction rate with CO2 with respect to MDEA-DEA blend, while the case was converse when compared to the MDEA-Glycine blend. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Investigation of Pore-Formers to Modify Extrusion-Spheronized CaO-Based Pellets for CO2 Capture
Processes 2019, 7(2), 62; https://doi.org/10.3390/pr7020062 - 24 Jan 2019
Cited by 7 | Viewed by 1304
Abstract
The application of circulating fluidized bed technology in calcium looping (CaL) requires that CaO-based sorbents should be manufactured in the form of spherical pellets. However, the pelletization of powdered sorbents is always hampered by the problem that the mechanical strength of sorbents is [...] Read more.
The application of circulating fluidized bed technology in calcium looping (CaL) requires that CaO-based sorbents should be manufactured in the form of spherical pellets. However, the pelletization of powdered sorbents is always hampered by the problem that the mechanical strength of sorbents is improved at the cost of loss in CO2 sorption performance. To promote both the CO2 sorption and anti-attrition performance, in this work, four kinds of pore-forming materials were screened and utilized to prepare sorbent pellets via the extrusion-spheronization process. In addition, impacts of the additional content of pore-forming material and their particle sizes were also investigated comprehensively. It was found that the addition of 5 wt.% polyethylene possesses the highest CO2 capture capacity (0.155 g-CO2/g-sorbent in the 25th cycle) and mechanical performance of 4.0 N after high-temperature calcination, which were about 14% higher and 25% improved, compared to pure calcium hydrate pellets. The smaller particle size of pore-forming material was observed to lead to a better performance in CO2 sorption, while for mechanical performance, there was an optimal size for the pore-former used. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Simulation Study on the Influence of Gas Mole Fraction and Aqueous Activity under Phase Equilibrium
Processes 2019, 7(2), 58; https://doi.org/10.3390/pr7020058 - 22 Jan 2019
Cited by 2 | Viewed by 1535
Abstract
This work explored the influence of gas mole fraction and activity in aqueous phase while predicting phase equilibrium conditions. In pure gas systems, such as CH4, CO2, N2 and O2, the gas mole fraction in aqueous [...] Read more.
This work explored the influence of gas mole fraction and activity in aqueous phase while predicting phase equilibrium conditions. In pure gas systems, such as CH4, CO2, N2 and O2, the gas mole fraction in aqueous phase as one of phase equilibrium conditions was proposed, and a simplified correlation of the gas mole fraction was established. The gas mole fraction threshold maintaining three-phase equilibrium was obtained by phase equilibrium data regression. The UNIFAC model, the predictive Soave-Redlich-Kwong equation and the Chen-Guo model were used to calculate aqueous phase activity, the fugacity of gas and hydrate phase, respectively. It showed that the predicted phase equilibrium pressures are in good agreement with published phase equilibrium experiment data, and the percentage of Absolute Average Deviation Pressures are given. The water activity, gas mole fraction in aqueous phase and the fugacity coefficient in vapor phase are discussed. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Theoretical Methodology of a High-Flux Coal-Direct Chemical Looping Combustion System
Processes 2018, 6(12), 251; https://doi.org/10.3390/pr6120251 - 04 Dec 2018
Cited by 2 | Viewed by 1399
Abstract
This study, as an extension of our previous experimental tests, presented a mechanism analysis of air reactor (AR) coupling in a high-flux coal-direct chemical looping combustion (CDCLC) system and provided a theoretical methodology to the system optimal design with favorable operation stability and [...] Read more.
This study, as an extension of our previous experimental tests, presented a mechanism analysis of air reactor (AR) coupling in a high-flux coal-direct chemical looping combustion (CDCLC) system and provided a theoretical methodology to the system optimal design with favorable operation stability and low gas leakages. Firstly, it exhibited the dipleg flow diagrams of the CDCLC system and concluded the feasible gas–solid flow states for solid circulation and gas leakage control. On this basis, the semi-theoretical formulas of gas leakages were proposed to predict the optimal regions of the pressure gradients of the AR. Meanwhile, an empirical formula of critical sealing was also developed to identify the advent of circulation collapse so as to ensure the operation stability of the whole system. Furthermore, the theoretical methodology was applied in the condition design of the cold system. The favorable gas–solid flow behaviors together with the good control of gas leakages demonstrated the feasibility of the theoretical methodology. Finally, the theoretical methodology was adopted to carry out a capability assessment of the high-flux CDCLC system under a hot state in terms of the restraint of gas leakages and the stability of solid circulation. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Energy Consumption and Economic Analyses of a Supercritical Water Oxidation System with Oxygen Recovery
Processes 2018, 6(11), 224; https://doi.org/10.3390/pr6110224 - 16 Nov 2018
Cited by 5 | Viewed by 1774
Abstract
Oxygen consumption is one of the factors that contributes to the high treatment cost of a supercritical water oxidation (SCWO) system. In this work, we proposed an oxygen recovery (OR) process for an SCWO system based on the solubility difference between oxygen and [...] Read more.
Oxygen consumption is one of the factors that contributes to the high treatment cost of a supercritical water oxidation (SCWO) system. In this work, we proposed an oxygen recovery (OR) process for an SCWO system based on the solubility difference between oxygen and CO2 in high-pressure water. A two-stage gas–liquid separation process was established using Aspen Plus software to obtain the optimized separation parameters. Accordingly, energy consumption and economic analyses were conducted for the SCWO process with and without OR. Electricity, depreciation, and oxygen costs contribute to the major cost of the SCWO system without OR, accounting for 46.18, 30.24, and 18.01 $·t−1, respectively. When OR was introduced, the total treatment cost decreased from 56.80 $·t−1 to 46.17 $·t−1, with a reduction of 18.82%. Operating cost can be significantly reduced at higher values of the stoichiometric oxygen excess for the SCWO system with OR. Moreover, the treatment cost for the SCWO system with OR decreases with increasing feed concentration for more reaction heat and oxygen recovery. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Calculation Model and Rapid Estimation Method for Coal Seam Gas Content
Processes 2018, 6(11), 223; https://doi.org/10.3390/pr6110223 - 14 Nov 2018
Cited by 7 | Viewed by 1549
Abstract
Coalbed gas content is the most important parameter for forecasting and preventing the occurrence of coal and gas outburst. However, existing methods have difficulty obtaining the coalbed gas content accurately. In this study, a numerical calculation model for the rapid estimation of coal [...] Read more.
Coalbed gas content is the most important parameter for forecasting and preventing the occurrence of coal and gas outburst. However, existing methods have difficulty obtaining the coalbed gas content accurately. In this study, a numerical calculation model for the rapid estimation of coal seam gas content was established based on the characteristic values of gas desorption at specific exposure times. Combined with technical verification, a new method which avoids the calculation of gas loss for the rapid estimation of gas content in the coal seam was investigated. Study results show that the balanced adsorption gas pressure and coal gas desorption characteristic coefficient (Kt) satisfy the exponential equation, and the gas content and Kt are linear equations. The correlation coefficient of the fitting equation gradually decreases as the exposure time of the coal sample increases. Using the new method to measure and calculate the gas content of coal samples at two different working faces of the Lubanshan North mine (LBS), the deviation of the calculated coal sample gas content ranged from 0.32% to 8.84%, with an average of only 4.49%. Therefore, the new method meets the needs of field engineering technology. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Regeneration of Sodium Hydroxide from a Biogas Upgrading Unit through the Synthesis of Precipitated Calcium Carbonate: An Experimental Influence Study of Reaction Parameters
Processes 2018, 6(11), 205; https://doi.org/10.3390/pr6110205 - 24 Oct 2018
Cited by 16 | Viewed by 2461
Abstract
This article presents a regeneration method of a sodium hydroxide (NaOH) solution from a biogas upgrading unit through calcium carbonate (CaCO3) precipitation as a valuable by-product, as an alternative to the elevated energy consumption employed via the physical regeneration process. The [...] Read more.
This article presents a regeneration method of a sodium hydroxide (NaOH) solution from a biogas upgrading unit through calcium carbonate (CaCO3) precipitation as a valuable by-product, as an alternative to the elevated energy consumption employed via the physical regeneration process. The purpose of this work was to study the main parameters that may affect NaOH regeneration using an aqueous sodium carbonate (Na2CO3) solution and calcium hydroxide (Ca(OH)2) as reactive agent for regeneration and carbonate slurry production, in order to outperform the regeneration efficiencies reported in earlier works. Moreover, Raman spectroscopy and Scanning Electron Microscopy (SEM) were employed to characterize the solid obtained. The studied parameters were reaction time, reaction temperature, and molar ratio between Ca(OH)2 and Na2CO3. In addition, the influence of small quantities of NaOH at the beginning of the precipitation process was studied. The results indicate that regeneration efficiencies between 53%–97% can be obtained varying the main parameters mentioned above, and also both Raman spectroscopy and SEM images reveal the formation of a carbonate phase in the obtained solid. These results confirmed the technical feasibility of this biogas upgrading process through CaCO3 production. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Article
Hydrodynamic Study of AR Coupling Effects on Solid Circulation and Gas Leakages in a High-Flux In Situ Gasification Chemical Looping Combustion System
Processes 2018, 6(10), 196; https://doi.org/10.3390/pr6100196 - 18 Oct 2018
Cited by 2 | Viewed by 1486
Abstract
In situ gasification chemical looping combustion (iG-CLC) is a novel and promising coal combustion technology with inherent separation of CO2. Our previous studies demonstrated the feasibility of performing iG-CLC with a high-flux circulating fluidized bed (HFCFB) riser as the fuel reactor [...] Read more.
In situ gasification chemical looping combustion (iG-CLC) is a novel and promising coal combustion technology with inherent separation of CO2. Our previous studies demonstrated the feasibility of performing iG-CLC with a high-flux circulating fluidized bed (HFCFB) riser as the fuel reactor (FR) and a counter-flow moving bed (CFMB) as the air reactor (AR). As an extension of that work, this study aims to further investigate the fundamental effects of the AR coupling on the oxygen carrier (OC) circulation and gas leakages with a cold-state experimental device of the proposed iG-CLC system. The system exhibited favorable pressure distribution characteristics and good adaptability of solid circulation flux, demonstrating the positive role of the direct coupling method of the AR in the stabilization and controllability of the whole system. The OC circulation and the gas leakages were mainly determined by the upper and lower pressure gradients of the AR. With the increase in the upper pressure gradient, the OC circulation flux increased initially and later decreased until the circulation collapsed. Besides, the upper pressure gradient exhibited a positive effect on the restraint of gas leakage from the FR to the AR, but a negative effect on the suppression of gas leakage from the AR to the FR. Moreover, the gas leakage of the J-valve to the AR, which is directly related to the solid circulation stability, was exacerbated with the increase of the lower pressure gradient of the AR. In real iG-CLC applications, the pressure gradients should be adjusted flexibly and optimally to guarantee a balanced OC circulation together with an ideal balance of all the gas leakages. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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Review

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Review
Carbon Mineralization by Reaction with Steel-Making Waste: A Review
Processes 2019, 7(2), 115; https://doi.org/10.3390/pr7020115 - 24 Feb 2019
Cited by 21 | Viewed by 2189
Abstract
Carbon capture and sequestration (CCS) is taking the lead as a means for mitigating climate change. It is considered a crucial bridging technology, enabling carbon dioxide (CO2) emissions from fossil fuels to be reduced while the energy transition to renewable sources [...] Read more.
Carbon capture and sequestration (CCS) is taking the lead as a means for mitigating climate change. It is considered a crucial bridging technology, enabling carbon dioxide (CO2) emissions from fossil fuels to be reduced while the energy transition to renewable sources is taking place. CCS includes a portfolio of technologies that can possibly capture vast amounts of CO2 per year. Mineral carbonation is evolving as a possible candidate to sequester CO2 from medium-sized emissions point sources. It is the only recognized form of permanent CO2 storage with no concerns regarding CO2 leakage. It is based on the principles of natural rock weathering, where the CO2 dissolved in rainwater reacts with alkaline rocks to form carbonate minerals. The active alkaline elements (Ca/Mg) are the fundamental reactants for mineral carbonation reaction. Although the reaction is thermodynamically favored, it takes place over a large time scale. The challenge of mineral carbonation is to offset this limitation by accelerating the carbonation reaction with minimal energy and feedstock consumption. Calcium and magnesium silicates are generally selected for carbonation due to their abundance in nature. Industrial waste residues emerge as an alternative source of carbonation minerals that have higher reactivity than natural minerals; they are also inexpensive and readily available in proximity to CO2 emitters. In addition, the environmental stability of the industrial waste is often enhanced as they undergo carbonation. Recently, direct mineral carbonation has been investigated significantly due to its applicability to CO2 capture and storage. This review outlines the main research work carried out over the last few years on direct mineral carbonation process utilizing steel-making waste, with emphasis on recent research achievements and potentials for future research. Full article
(This article belongs to the Special Issue Gas Capture Processes)
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