Carbon Dioxide Capture Process Research Articles

An experimental and modeling study on incipient hydrate-forming conditions for ternary guests of carbon dioxide, nitrogen and sulfur dioxide

In carbon dioxide capture and sequestration (CCS) processes, captured CO2 may encounter conditions of hydrate formation due to the presence of water. For stable, long-term operation of CCS processes, hydrate-phase equilibrium data are essential. Captured CO2 from combustion of fossil fuel may include other impurities such as N2 and SO2. Phase equilibria including a single impurity (N2 or SO2) have been reported by other researchers, but no experimental observations have been obtained for ternary guest systems. In this work, the incipient hydrate-forming temperatures for a binary guest of CO2 and N2 and a ternary guest of CO2, N2 and SO2 were experimentally measured at 2.0–3.5 MPa. An effect of the ratio between guest components and water was observed. The experimental results were compared with calculations using an equation of state based on a hydrogen-bonding nonrandom lattice fluid (NLF-HB) combined with the van der Waals-Platteeuw model. The model predictions were in good agreement with experimental data with an overall average deviation of 2.6%.

CO2 stripping from ionic liquid at elevated pressures in gas-liquid membrane contactor

In this study, the gas-liquid membrane contactor was considered for regeneration of the room-temperature ionic liquids (RTIL) that can be used as physical solvents for carbon dioxide capture process at elevated pressures. Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) was selected as a membrane material due to its high mass transport characteristics and good mechanical properties. Nine different RTILs, such as [Emim][DCA], [Emim][BF4], [Emim][DEP], [Bmim][BF4], [Bmim][Tf2N], [Hmim][TCB], [P66614][DCA], [P66614][Br] and [P66614][Phos], were used to evaluate the solvent-membrane compatibility. The long-term sorption tests (40+ days) revealed that the solvent-membrane interaction is mainly determined by the liquid surface tension regardless of viscosity and molecular size of RTILs. For instance, [Emim][BF4] and [Emim][DCA], having the surface tension of 60.3 and 54.0 mN/m, demonstrated a very low affinity to the bulk material of PTMSP (sorption as low as 0.02 g/g; no swelling); while for the next ionic liquid [Bmim][BF4] with surface tension of 44.4 mN/m, the sorption and swelling of PTMSP was 0.79 g/g and 21%, respectively. The long-term RTIL permeation test (Δp = 40 bar, T = 50°С, t > 400 h) confirmed that there is no hydrodynamic flow through PTMSP for [Emim][DCA] and [Emim][BF4]. The concept of CO2 stripping from RTIL with the membrane contactor by the pressure (Δp = 10 bar) and temperature (ΔT = 20 °С) swing was proved by using dense PTMSP membrane and [Emim][BF4]. The overall mass transfer coefficient value was equal to (1.6 − 3.8) × 10−3 cm/s with respect to liquid flow rate. By using the resistance-in-series model, it was shown that the membrane resistance contribution to the gas transfer was estimated to be approximately 8%.

Neural Network Based Outlier Identification in Data Values of Carbon Dioxide Loaded 2-amino-2-methyl-1-Propanol Solutions

Presence of a few measured outliers in a non-linear chemical dataset, like CO2-(2-amino-2-methyl-1-propanol)-H2O is a commonality and a hindrance in development of correlation and model development for carbon dioxide capture processes. Therefore, these outliers must be identified and treated accordingly. Most of the traditional statistical techniques are weak in such correlation and lose information at the extrema of the designated system. Hence, neural network based identification is a promising technique for data outliers found in the above system. The proposed approach flexibly transforms to the nonlinear data distribution and identifies the outliers, reported in open literature. The proposed method improves the shortcomings of previous statistical approaches and can be potentially extended to other nonlinear experimental datasets in chemical process systems.

Thermodynamic Modeling and Experimental Study of CO2 Dissolution in New Absorbents for Post-Combustion CO2 Capture Processes

Demixing solvents have been suggested as an alternative to aqueous solutions of alkanolamines for the decarbonation of industrial effluents. These solvents undergo a liquid–liquid phase separation when heated. A phase-separation step could be integrated in the carbon dioxide (CO2) capture process to reduce energetic cost of the solvent regeneration step. As part of a general project on the dissolution of CO2 in aqueous solutions of piperidines, 3-methylpiperidine and 4-methylpiperidine have been investigated. The enthalpies of solution of CO2 in aqueous solutions of those methylpiperidines have been measured using a flow calorimetric technique. This technique makes it possible to simultaneously determine the enthalpies of solution and CO2 solubility limits. The experimental data were used to develop a thermodynamic model representative of phase equilibrium and enthalpy of solution. The carbamate formation constants of the 3-methylpiperidine and 4-methylpiperidine are adjusted in the model. The thermodynam...

Energy and exergy analysis of alternating injection of oxygen and steam in the low emission underground gasification of deep thin coal

Recent studies have shown that by coupling the underground coal gasification (UCG) with the carbon capture and storage (CCS), the coal energy can be economically extracted with a low carbon footprint. To investigate the effect of UCG and CCS process parameters on the feasibility of the UCG-CCS process, we utilize a validated mathematical model, previously published by the same authors, that can predict the composition of the UCG product, temperature profile, and coal conversion rate for alternating injection of air and steam for unmineable deep thin coal layers. We use the results of the model to conduct an energy and exergy analysis of the UCG process. We study the effect of various process parameters on the efficiency of the UCG process, the zero-emission recovery factor of coal, and the total CO2 emission of the process. Moreover, we compare the alternating injection of air/steam with the injection of an air and steam mixture.Exergy analysis shows that the alternating injection of air/steam describes a practical process for UCG at low pressure. However, injecting a mixture of steam and oxygen results in a practical recovery factor of coal higher than the alternating injection process. Additionally, we show that the zero-emission conversion of unmineable deep thin coal resources in a coupled UCG-CCS process, that is not practical with the current state of technology, can be realized by increasing the energy efficiency of the carbon dioxide capture process.

Energy-efficient chemical regeneration of AMP using calcium hydroxide for operating carbon dioxide capture process

To avoid the main disadvantage of the carbon dioxide (CO2) capture process, namely the large amount of energy consumed to regenerate the amine absorbent using current thermal methods, chemical regeneration has been introduced as a novel method to regenerate the amine. Chemical regeneration deploys a swing in the pH of the amine absorbent rather than the swing in temperature of typical thermal regeneration procedures, and hence reduces the regeneration energy. Here we tested calcium chloride (CaCl2) and calcium hydroxide (Ca(OH)2) as a calcium source for CO2 desorption and a pH swing agent for amine regeneration. After desorbing from the amine, CO2 in our procedures reacted with Ca2+ to form calcium carbonate (CaCO3). Forming precipitated CaCO3 is a permanent way to sequester CO2. Since carbonates have a low energy level compared to CO2, we expect the developed method to be an economical and energy-efficient process.

A consistent and transferable thermodynamic model to accurately describe CO2 capture with monoethanolamine

In this work, a consistent and transferable thermodynamic model to describe the carbon dioxide (CO2) capture process with monoethanolamine (MEA) has been successfully developed within the framework of the soft-SAFT equation of state. The effect of the association interactions of the amine and alcohol groups contained in MEA have been isolated and characterized by studying the 1-alkylamines and 1-alkanols family. In a similar manner, the interaction between these functional groups and water has also been determined and later transferred to aqueous MEA. At the end, a reliable and consistent set of molecular parameters has been obtained for MEA. The CO2 absorption process is described in terms of the aggregation of the reactants driven by the presence of strong intermolecular interactions. Descriptions of the density, vapor pressure and surface tension in these systems provide excellent agreement with the available experimental information. Also, a very good estimation of the CO2 loading in MEA is found in the range of operating conditions. Predictions on the mixing enthalpies and the enthalpy of absorption are also given. This transferable model will allow the prediction of the CO2 absorption process in other alkanolamines in the absence of experimental data.

Kinetic and Equilibrium Reactions of a New Heterocyclic Aqueous 4-Aminomethyltetrahydropyran (4-AMTHP) Absorbent for Post Combustion Carbon Dioxide (CO2) Capture Processes

Aqueous amine absorbent processes remain at the forefront of existing technologies for the removal of CO2 from industrial and large-scale power generation flue gas streams. It is essential that improvements in amine-based absorbent technologies are made in order to reduce both capital and operational costs. Intimate understanding of the fundamental chemical behavior of new amine absorbent systems is an intelligent pathway toward higher efficiency amine-based CO2 capture processes. Herein, we investigate and report for the first time the complete temperature-dependent kinetic and equilibrium behavior of a new heterocyclic amine 4-aminomethyltetrahydropyran (4-AMTHP), with CO2, in aqueous solutions. Stopped-flow spectrophotometry, 1H NMR spectroscopy, and potentiometric titration measurements performed over the temperature range 25.0–45.0 °C and the corresponding rate constants for the reversible formation of the carbamic acid, together with equilibrium constants describing the stability of the carbamate, and the protonation of the amine are reported here. Thermodynamic analysis of the resulting constants using the Eyring, Arrhenius, and van’t Hoff relationships has revealed the activation energies, enthalpies, and entropies for the reactions, allowing a comparison to the industrial standard monoethanolamine (MEA). From the kinetic data, the performance of 4-AMTHP was found to be superior to MEA and in line with the established Brønsted relationship between the second-order rate constant and the protonation constant or basicity of the amine. The largely negative protonation enthalpy (−47 kJ/mol), among the key chemical drivers for CO2 regeneration, is again superior to MEA (−41 kJ/mol). Together, a combination of kinetic and equilibrium properties of 4-AMTHP strongly position 4-AMTHP as a promising candidate for more intensive evaluations as a CO2 capture absorbent.

Dual-reflux pressure swing adsorption process for carbon dioxide capture from dry flue gas

This work presents a detailed experimental and simulation study for capturing and recovering high purity carbon dioxide from a dry flue gas (15%CO2/85%N2) via a laboratory-scale dual-reflux pressure swing adsorption apparatus using silica gel as an adsorbent. To achieve a favorable carbon capture performance, parameter study was implemented to obtain a series of optimized settings of process operating variables by investigating the effects of flowrate of light product reflux, flowrate of heavy product and feed inlet position on the separation performance in terms of product purity, product recovery, and adsorbent productivity, as well as specific power-consumption. Under the optimal manipulation parameter configuration, a high-purity CO2 product with a concentration of 95.55% and a higher CO2 product recovery of 96.81% with a competitive specific power consumption of 110.58kJmol−1CO2 can be obtained. This finding demonstrated an efficient and economical method in the field of carbon capture and storage. In addition, a good consistency between simulation results and experimental data confirmed the reliability of the mathematical model of dual-reflux pressure swing adsorption process, and the dynamic distribution behaviors of pressure, temperature and gas-solid concentration were obtained from the simulation results to illuminate and validate the process separation performance in depth under different operating conditions.

Integrated CO2 Capture and Utilization Using Non-Thermal Plasmolysis

In the presented work, 2 simple processes for carbon dioxide (CO2) capture and utilisation have been combined to form a whole systems approach to carbon capture and utilisation (CCU). The first stage utilises a pressure swing adsorption (PSA) system, which offers many benefits over current amine technologies. It was found that high selectivity can be achieved with rapid adsorption/desorption times whilst employing a cheap, durable sorbent that exhibits no sorbent losses and is easily regenerated by simple pressure drops. The PSA system is capable capturing and upgrading the CO2 concentration of a waste gas stream from 12.5% to a range of higher purities. As many CCU end processes have some tolerance towards impurities in the feed, in the form of nitrogen (N¬2) for example, this is highly advantageous for this PSA system since CO2 purities in excess of 80% can be achieved with only a few steps and minimal energy input. Non-thermal plasma is one such technology that can tolerate, and even benefit from, small N2 impurities in the feed, therefore a 100% pure CO2 stream is not required. The second stage of this process deploys a nanosecond pulsed corona discharge reactor to split the captured CO2 into carbon monoxide (CO), which can then be used as a chemical feedstock for other syntheses. Corona discharge has proven industrial applications for gas cleaning and the benefit of pulsed power reduces the energy consumption of the system. The wire-in-cylinder geometry concentrates the volume of gas treated into the area of high electric field. Previous work has suggested that moderate conversions can be achieved (9%), compared to other non-thermal plasma methods, but with higher energy efficiencies (>60%).

A conceptual design of catalytic gasification fuel cell hybrid power plant with oxygen transfer membrane

A hybrid power generation system integrating catalytic gasification, solid oxide fuel cell (SOFC), oxygen transfer membrane (OTM) and gas turbine (GT) is established and system energy analysis is performed. In this work, the catalytic gasifier uses steam, recycled anode off-gas and pure oxygen from OTM system to gasify coal, and heated by hot cathode off-gas at the same time. A zero-dimension SOFC model is applied and verified by fitting experimental data. Thermodynamic analysis is performed to investigate the integrated system performance, and system sensitivities on anode off-gas back flow ratio, SOFC fuel utilization, temperature and pressure are discussed. Main conclusions are as follows: (1) System overall electricity efficiency reaches 60.7%(HHV) while the gasifier operates at 700 °C and SOFC at 850 °C with system pressure at 3.04 bar; (2) oxygen enriched combustion simplify the carbon-dioxide capture process, which derives CO2 of 99.2% purity, but results in a penalty of 6.7% on system electricity efficiency; (3) with SOFC fuel utilization or temperature increasing, the power output of SOFC increases while GT power output decreases, and increasing system pressure can improve both the performance of SOFC and GT.

Integration of Reforming and CO2Removal Processes in a Gas-to-Liquid Plant

In the current era of high energy prices and environmental issues, extensive research is being done to convert natural gas to useful products. For this purpose, the GTL (gas-to-liquid) process is considered an effective process which can produce high quality liquid petroleum products. However, the greenhouse gases produced in the reforming section contribute to global warming which makes the carbon dioxide capture process inevitable. In this work, a reformer reactor is used to produce the syngas, with H2/CO mole ratio of 2, and the reforming process is integrated with the solvent based carbon dioxide capture process. Moreover, the conventional design exhibits enormous energy requirements due to the high energy demand in the reformer and solvent regenerator column. Heat integration and the heat transfer process offer an outline to reduce the energy load of the process. Therefore, different configurations are proposed by modifying the flow sheet, and heat integrations are applied to optimize the total heat ...

Pilot scale testing and modeling of enzymatic reactive absorption in packed columns for CO2 capture

Efficient processes for carbon dioxide (CO2) capture from post-combustion flue gases are required to combat global climate change. A key stage in post-combustion capture is selective CO2 separation from the flue gas stream. Separation of CO2 from mixed gases using countercurrent gas–liquid absorption in packed columns is a well-established technology for treatment of industrial gas streams. This approach can be adapted to remove CO2 from post-combustion flue gas, however, process improvements are needed to minimize the corresponding capital costs and energy requirements. Special challenges for CO2 recovery from flue gas arise from the very large volumes of gas to be processed, the need to operate the process with an inlet flue gas stream at atmospheric pressure, and the high amount of energy required to regenerate the absorption liquid. Aqueous solutions of the tertiary amine N-methyldiethanolamine (MDEA) are commercially used for high pressure CO2 separation due to high loading capacity for CO2, relatively good chemical and thermal stability and low volatility.Application of MDEA-based solutions to ambient pressure separations, such as CO2 capture from flue gases, is challenging since high reaction rates are required. High reaction rates for the MDEA system are achievable at high temperatures, which is conflicting with the preference of low temperatures to exploit high absorption capacity. This conflict can be overcome with the addition of a rate enhancing catalyst that enables high reaction rates at low temperatures.To put this innovative breakthrough technology closer to industrial application CO2 absorption in 30–50wt.% aqueous solutions of MDEA in absence and presence of the CO2 absorption enhancing enzyme carbonic anhydrase (CA) was evaluated in pilot scale. The pilot scale investigation employed a packed column for parametric testing. Test variables included the liquid phase composition (30–50wt.% MDEA), the column liquid load (8–24m3m−2h−1), the absorber temperature (20–40°C), and the application of CA in a dissolved or immobilized form. The CO2 absorption mass transfer enhancement provided by CA was measured.In the presence of dissolved CA, 30wt.% aqueous MDEA showed superior performance in terms of absorption rates compared to operation using 50wt.% MDEA(aq). No significant change in the CO2 absorption rate was observed for operation at given loads between 20°C and 40°C with dissolved CA present. At 20°C with 30wt.% MDEA the absorption rate with dissolved CA increased by more than 9 times compared to the absorption rate without enzyme. These results broaden the operation window for efficient CO2 absorption using MDEA solutions and allow for the exploitation of new process regimes, wherein high equilibrium loadings are achievable by applying lower absorption temperatures.Based on the experimental results obtained with dissolved CA, a simplified rate-based model of enzymatic reactive absorption (ERA), accounting for enzyme accelerated reaction kinetics, was developed which was capable of accurately predicting CO2 absorption rate when compared with experimental data. Implemented in a process simulator the model allows for the detailed investigation of the process behavior and the complex interactions of ab- and desorption operations in the presence of the CA. The validated model is intended to guide future experimental work as well as further performance optimization.In addition to the work exploiting the catalyst in its free form, the utilization of CA immobilized in a granular form and held in the pockets of Katapak-SP packing was successfully demonstrated.

Emergy analysis of three alternative carbon dioxide capture processes

Carbon dioxide (CO2) capture technologies have increased in importance recently due to high CO2 emission levels, principally from fossil fuel power generation to support increasing global energy demand. In this study, emergy accounting was applied to quantify the utilization of resources and compare process performance, in terms of sustainability, of three alternative CO2 capture technologies (chemical absorption, solid adsorption and membrane separation) selected from the representative literature. The natural investment or unit emergy value (UEV) of each process was evaluated in units of sej/kg. The results revealed that the lowest to highest UEVs were solid adsorption, membrane separation and amine absorption, respectively. Thus, the most preferable choice for CO2 capture among these three approaches was solid-based adsorption, since it consumed the lowest level of natural resources. Moreover, the UEV of the solid-based adsorption process can be lowered by improving and optimizing the heat utilization within the system and replacing the non-renewable sources of heat and power with renewable resources. In addition, the emergy analysis also provided suggestions for improving membrane separation and amine absorption processes. For amine absorption, improving solvent regeneration efficiency would reduce natural gas consumption, while for membrane separation, power sources should be switched to renewable resources.

Carbon capture and utilization for sodium bicarbonate production assisted by solar thermal power

In this paper, a novel carbon capture and utilization process is proposed. It is based on using a fraction of the captured carbon dioxide to produce sodium bicarbonate, a widely used product in the chemical and food industries. The process couples the Dry Carbonate process for carbon dioxide capture with sodium bicarbonate production.Raw material is trona or sodium sesquicarbonatedehydrate, which is a relatively abundant mineral composed by approximately 46% sodium carbonate and 35% sodium bicarbonate by weight. In the process, trona is firstly converted into sodium carbonatein a fluidized bed reactor operated at 180–200°C and 1bar. Heat required in the fluidized bed reactor for decomposing trona can be supplied by renewable sources such as low/medium temperature solar energy or biomass. A fraction of the sodium carbonategenerated is recirculated for carbon dioxide capture by means of the dry carbonate process. The rest is converted to sodium bicarbonatein a carbonating tower through the reaction with carbon dioxide and water. After separation of sodium bicarbonate and other salts from water, the sodium bicarbonate produced is suitable for direct sale. The use of renewable sources for supplying the energy required at the sorbent regenerator and for trona decomposition yields a near-zero carbon dioxide emissions global system. As case of study, carbon dioxide capture coupled to sodium bicarbonate production has been analysed for a 15 MWel coal fired power plant. Heat required in the carbon capture process penalizes the global system efficiency by a 10.2%, which is reduced just to the electricity parasitic consumption for solids transport and carbon dioxide compression (∼3%) if renewable energy sources are integrated. From an economic perspective, the penalty in electricity consumption is fully compensated by the new by-product sales. Taking into account the reduction of electricity sales and current prices of trona and sodium bicarbonatea return of investment is obtained in the range between 3 and 8.7years with an internal rate of returnover 12%. These values improve the current forecast of any other carbon capture and storage process up to date, which suggests a high interest of the proposed conceptual integration specially for regions where trona is widely available.

Selection of amine combination for CO2 capture in a packed bed scrubber

This investigation was to test different blends of tertiary amine; triethanolamine (TEA) into primary amine; Monoethanolamine (MEA) usedto capture CO2 in packed bed scrubber with recycle stream. Four different operating parameters: Amine Combination (A), Dilution Water (B),Liquid Flow rate (C), and Gas Flow rate (D) were varied to study the behavior of the system. Moreover, Taguchi method was employed to establishthe order of importance of different parameters in the process. A 4 factor and 3 level was chosen for the study and it was explored using L9 (34)orthogonal array design. According to 3-level design 0%, 20% and 30% were chosen for A, 10%, 20% and 30% for B, 1 Lmin−1, 1.5 Lmin−1 and2 Lmin−1 for C, 8 Lmin−1, 16 Lmin−1 and 20 Lmin−1 for D. To understand the effectiveness order of different operating parameters, three factorsnamely Absorption efficiency (E), Absorption Rate (RA), and Scrubbing Factor (E) were calculated upon which the order was compared. Thehighest efficiency of 92.2% was achieved with 20% TEA. However, with 30% of TEA and 20% solvent mix maximum scrubbing factor (E) of0.63 mol-CO2/mol-Solvent was achieved. As per Taguchi analysis the significance sequence for absorption efficiency (ϕ) was B > C > D > A; forabsorption rate C > B > D > A and for scrubbing factor it was C > B > D > A. The blending of tertiary amine seemed advantageous for carbondioxide capture process.

Optimization of pre-combustion capture for thermal power plants using Pinch Analysis

Carbon dioxide emissions from the chimneys of thermal power plants create major environmental risks. Therefore, an important step toward reducing the emissions in these power plants can be the carbon dioxide pre-combustion capture process. In this paper, a 150 MW thermal steam cycle power plant fueled by bagasse was studied. The power plant has an efficiency of 32.74%, and emits 246.52 t/h carbon dioxide. First, the design and simulation of a suggested pre-combustion carbon dioxide capture process was outperformed. In this process, the amount of carbon dioxide separation and capture using mono ethanol amine (MEA) 30 wt% as solvent is 90%. In this condition, the mass flow of bagasse was increased about 60% to keep the plant efficiency constant. At the same time, the energy loss as a result of the addition of the carbon dioxide recovery unit was around 11%. The process was optimized through Pinch Analysis to reduce energy waste and fuel flow. Moreover, it was indicated that power plant efficiency could be increased around 8% by integrating the hot exhaust gases from the gasification unit with power plant boiler using a heat recovery steam generation (HRSG) unit. With this modification, bagasse consumption was decreased by 23%.

Selection of amine combination for CO2 capture in a packed bed scrubber

Abstract This investigation was to test different blends of tertiary amine; triethanolamine (TEA) into primary amine; Monoethanolamine (MEA) used to capture CO 2 in packed bed scrubber with recycle stream. Four different operating parameters: Amine Combination (A), Dilution Water (B), Liquid Flow rate (C), and Gas Flow rate (D) were varied to study the behavior of the system. Moreover, Taguchi method was employed to establish the order of importance of different parameters in the process. A 4 factor and 3 level was chosen for the study and it was explored using L9 (3 4 ) orthogonal array design. According to 3-level design 0%, 20% and 30% were chosen for A, 10%, 20% and 30% for B, 1 Lmin −1 , 1.5 Lmin −1 and 2 Lmin −1 for C, 8 Lmin −1 , 16 Lmin −1 and 20 Lmin −1 for D. To understand the effectiveness order of different operating parameters, three factors namely Absorption efficiency (E), Absorption Rate (RA), and Scrubbing Factor (E) were calculated upon which the order was compared. The highest efficiency of 92.2% was achieved with 20% TEA. However, with 30% of TEA and 20% solvent mix maximum scrubbing factor (E) of 0.63 mol-CO 2 /mol-Solvent was achieved. As per Taguchi analysis the significance sequence for absorption efficiency (ϕ) was B > C > D > A; for absorption rate C > B > D > A and for scrubbing factor it was C > B > D > A. The blending of tertiary amine seemed advantageous for carbon dioxide capture process.

E-PPR78: A proper cubic EoS for modelling fluids involved in the design and operation of carbon dioxide capture and storage (CCS) processes

Considering the broad range of operating conditions that typically characterize carbon dioxide capture and storage (CCS) processes, on the one side, and the high number of species that compose the processed streams, on the other, it becomes evident the necessity of disposing of suitable equations of state being able to flexibly represent the complexity of all these thermodynamic systems. To address the growing industrial need for predictive, sufficiently accurate and simple thermodynamic models, the Enhanced-Predictive-PR78 (E-PPR78) equation of state is proposed here as a suitable model for CCS fluids. Currently, the application of the E-PPR78 model is limited to CCS mixtures of CO2, CH4, N2, O2, Ar, H2, H2S, SO2, NO, CO and H2O. The main objective of this work is the extension of the modelling capability of E-PPR78 to mixtures that, besides the mentioned species, could also contain COS, NH3, NO2, N2O4 and N2O. This result is achieved by introducing, with this paper, four new molecular groups for the E-PPR78 model, namely, “COS” (group 28), “NH3” (group 29), “NO2/N2O4” (group 30) and “N2O” (group 31). More specifically, the paper presents, at first, a review of all the available experimental vapor-liquid-equilibrium (VLE) and enthalpy changes on mixing (hM) data for binary systems containing 2 of the following compounds: CO2, CH4, N2, O2, Ar, H2, H2S, COS, SO2, NH3, NO, NO2, N2O4, N2O, CO and H2O. Secondly, the E-PPR78 model is parameterized over these data: not only new group-interaction parameters are determined for the 4 groups added in this study but many parameters are updated over newly available data. Modelling results are analyzed accounting for the complexity of each system, evaluated according to the classification scheme of Van Konynenburg and Scott. Moreover, the capacity of the model to predict ternary data is meticulously discussed. This research thus provides a predictive equation of state, the E-PPR78, being applicable to most of the currently treated CCS fluids, and discusses its strengths and limitations.

The effects of refractory zirconium-based ceramic dopants on the stability performance of synthetic Ca-based sorbents prepared by co-precipitation method in cyclic CO2 capture operations

Calcium (Ca) based sorbents utilized in the carbon dioxide (CO2) capture process at high temperatures have displayed considerable activity loss during extended use, due to sintering. Refractory zirconium-based ceramics, however, have shown excellent performances as thermal barrier coatings in many high-tech applications; and, the recent doping of zirconia in Ca-based sorbents has exhibited excellent sustainability in the activity stability in cyclic CO2 capture operations. In this work, we doped sorbents, at loadings of 10 wt%, with a few zirconium-based ceramics, such as alkaline earth metal zirconate (calcium zirconate, CaZrO3), which has the chemical structure of perovskite, and rare earth metal zirconates, which have the chemical structure of pyrochlore. These materials were prepared through the wet co-precipitation method, in order to achieve the optimal uptake capacity and stability in cyclic CO2 capture operations. Among the sorbents tested, the CaZrO3-doped sorbents exhibited excellent performance, remarkable thermal stability and sintering resistant. Therefore, the sorbents were stable though 30 carbonation–calcination cycles. The sorbent showed a CO2 capture capacity of 12 mol CO2/kg sorbent, with an activity loss of 19.6% through carbonation at 675 °C for 10 min and calcination at 850 °C for 10 min. Among the rare earth metal zirconate ceramics, samarium zirconate (Sm2Zr2O7) exhibited the best stability with an activity loss of 23.4% loss, but at a lower uptake of 7.2 mol CO2/kg sorbent at the same carbonation–calcination conditions. In comparison, Cadomin (a natural calcium carbonate) at the same conditions resulted in a capture capacity of 13.5 mol CO2/kg sorbent and an activity loss of 69%. Surface area characterizations showed that incorporation of the ceramics to the calcium based sorbents significantly improved the surface morphology and textural properties of the sorbents. X-ray diffraction results indicated that the improved resistance of the sorbent could be due to forming of ceramic structures such perovskite-type CaZrO3 at a relatively low temperature (around 850 °C compared to higher temperatures required for pyrochlore-type ceramic formation), which made a stable sorbent structure for the carbonation process.