Gas CO2 Capture Research Articles

Improvement of CO2 capture performance of calcium-based absorbent modified with palygorskite

Limestone can be used for CO2 capture and sequestration (CCS) in flue gas effectively. However, its CCS capability will dramatically decline after several cycles due to the surface “sintering”. In this work, the limestone was modified with palygorskite to reduce sintering phenomenon between the absorbent particles during the CCS process and the carbonation rate of the limestone can be enhanced effectively. Palygorskite is a natural mineral with nano-fibrous structure which can reduce the mutual contact of limestone particles during the CCS process. The results were detected by TGA, SEM, MIP, FTIR and particle size analyzer respectively. The best CO2 capture performance of modified absorbent was 13.11% improvement with only 5wt% palygorskite added during the CCS process after 15cycles compared with natural absorbent. It was found that excellent microscopic structures of absorbent modified with palygorskite was created, and the surface sintering was postponed leading to CO2 capture performance enhanced under the same conditions.

Promotion of hydrate-based CO2 capture from flue gas by additive mixtures (THF (tetrahydrofuran) + TBAB (tetra-n-butyl ammonium bromide))

HBGS (Hydrate-based gas separation) is a potential method for CO2 capture from fossil fuel power plants. High hydrate formation rates and low energy consumption are still the demands for industrial application of HBGS. The promotion effects of three additive mixtures (THF (tetrahydrofuran) + TBAB (tetra-n-butyl ammonium bromide)) on flue gas (CO2/N2) hydrate phase equilibrium and CO2 capture characteristics were experimentally investigated in this study. It was found that hydrate phase equilibrium pressure for the 5% THF + 5% TBAB mixture was almost the same as that for the 5% THF + 10% TBAB mixture. Both the gas consumption and CO2 recovery increased substantially with increases in the mass fractions of THF or/and TBAB. The experimental results also showed that the gas consumption increases with the enhancement of initial pressure. Considering the hydrate phase equilibrium conditions and gas separation efficiency, an additive mixture with a mass fraction of 5% THF + 10% TBAB was found to be a better choice for hydrate-based CO2 capture from flue gas relative to other additive mixtures investigated in this study.

Ternary mixed-gas separation for flue gas CO2 capture using high performance thermally rearranged (TR) hollow fiber membranes

Abstract A comprehensive study evaluated the mixed-gas (CO2/N2/O2) separation performance of thermally rearranged polybenzoxazole-co-imide (TR-PBOI-AD5) hollow fiber membranes fabricated in-house (pure-gas CO2 permeance of 481 GPU and ideal CO2/N2 selectivity of 17.7). The criteria for the determining the two major operating conditions (pressure ratio and feed flow rate) were identified in order to deliver optimal separation performance with low process energy consumption. By varying the feed CO2 concentrations, it was found that a single-stage operation using TR-PBOI-AD5 (produced by bis-APAF and DAM as the TR-able and non-TR-able diamines, respectively, based on 6FDA) hollow fiber membranes was not sufficient to meet the required 90% permeate CO2 purity target, while a two-stage operation using the same membranes led to a permeate CO2 purity (81%) closer to the target value. The comparison study among the TR polymer membranes and three other polymer membranes highlighted the significance of an appropriate choice of a mixed-gas separation operating scheme to fully utilize the exceptional permeation properties of the recently developed high performance membranes such as TR polymeric membranes.

Neutrophil granulocytes in atlantic salmon (Salmo salar L.) are MHCII positive antigen-presenting cells

Limestone can be used for CO2 capture and sequestration (CCS) in flue gas effectively. However, its CCS capability will dramatically decline after several cycles due to the surface “sintering”. In this work, the limestone was modified with palygorskite to reduce sintering phenomenon between the absorbent particles during the CCS process and the carbonation rate of the limestone can be enhanced effectively. Palygorskite is a natural mineral with nano-fibrous structure which can reduce the mutual contact of limestone particles during the CCS process. The results were detected by TGA, SEM, MIP, FTIR and particle size analyzer respectively. The best CO2 capture performance of modified absorbent was 13.11% improvement with only 5 wt% palygorskite added during the CCS process after 15 cycles compared with natural absorbent. It was found that excellent microscopic structures of absorbent modified with palygorskite was created, and the surface sintering was postponed leading to CO2 capture performance enhanced under the same conditions.

Model development and process simulation of postcombustion carbon capture technology with aqueous AMP/PZ solvent

This study presents the development, application, and uncertainty analysis of a process simulation model for postcombustion CO2 capture with an AMP/PZ solvent blend based on state of the art knowledge on AMP/PZ solvent technology. The development includes the improvement of the physical property models of a software package designed for simulation of acid gas treatment and CO2 capture technologies. The improvement particularly consisted of regression of AMP–PZ binary interaction parameters. The model was applied to a case study of postcombustion CO2 capture from an Advanced Super Critical Pulverized Coal power plant. Uncertainly analysis was undertaken by validating the physical property models against laboratory measurements reported in literature; by comparing model results with pilot study results, and by evaluating the strength of the model with a novel method called pedigree analysis. The results show that AMP/PZ postcombustion technology performs better than MEA technology on most performance indicators, e.g., the Specific Reboiler Duty is reduced from 3.6GJ/t CO2for MEA, to 2.9 GJ/t CO2 for AMP/PZ, and the specific cooling water requirement is reduced from 4.1 to 3.4GJ/t CO2. Only amine slip to the atmosphere increases with AMP/PZ technology: from 0.18g/t CO2 to 15.3g/t CO2, although this value is still within emission limits from existing regulatory frameworks. The coal power plant net efficiency with AMP/PZ capture amounts to a value of 37.2%LHV, compared to 46.1%LHV for the case without CCS and 36.2%LHV in case of CCS with MEA. The uncertainty analysis shows that the model is well capable of predicting experimental and pilot result. The remaining uncertainty is mostly in the reaction kinetics and in the flowsheet design. Validation could be further improved, by more elaborate comparison to independent measures of physical properties, and by comparison of the model outputs to results from large demonstration or commercial size capture plants.

Highly stable porous covalent triazine–piperazine linked nanoflower as a feasible adsorbent for flue gas CO2 capture

Here, we report a porous covalent triazine–piperazine linked polymer (CTPP) featuring 3D nanoflower morphology and enhanced capture/removal of CO2, CH4 from air (N2), essential to control greenhouse gas emission and natural gas upgrading. 13C solid-state NMR and FTIR analyses and CHN and X-ray photoelectron spectroscopy (XPS) elemental analyses confirmed the integration of triazine and piperazine components in the network. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) analyses revealed a relatively uniform particle size of approximately 400–500nm with 3D nanoflower microstructure, which was formed by the self-assembly of interwoven and slight bent nanoflake components. The material exhibited outstanding chemical robustness under acidic and basic medium and high thermal stability up to 773K. The CTPP possess high surface area (779m2/g) and single-component gas adsorption study exhibited enhanced CO2 and CH4 uptake of 3.48mmol/g, 1.09mmol/g, respectively at 273K, 1bar; coupled with high sorption selectivities for CO2/N2 and CH4/N2 of 128 and 17, respectively. The enriched Lewis basicity of the CTPP favors the interaction with CO2, which results in an enhanced CO2 adsorption capacity and high CO2/N2 selectivity. The binary mixture breakthrough study for the flue gas composition at 298K showed a high CO2/N2 selectivity of 82. CO2 heats of adsorption for the CTPP (34kJmol−1) were realized at the borderline between strong physisorption and weak chemisorption (QstCO2; 25–50kJmol−1) and low Qst value for N2 (22.09kJmol−1), providing the ultimate validation for the high selectivity of CO2 over N2.

CO2 capture in a continuous gas–solid trickle flow reactor

This paper describes the selection, design and experimental validation of a gas–solid trickle flow adsorber for post-combustion CO2 capture using a supported amine sorbents (Lewatit® VP OC 1065). The experimental work presented here summarizes over 300h of operating experience, which is equivalent to approximately 350 adsorption/desorption cycles. We measured the effect of process parameters like gas velocity, solid flux and CO2 inlet concentration on adsorber performance in terms of the capture efficiency, productivity and working capacity. The performance of the trickle flow adsorber was adequately described by a 1-D plug-flow model. This model was used to design an adsorber to capture 90% of the CO2 emitted by a 500MWe coal fired power plant. Model predictions have indicated that the trickle flow adsorber outperforms the scrubber in the conventional MEA based process in terms of productivity; 1.1 compared to 0.6mol/m3/s in the MEA based process. Finally, the energy demand of the lab scale capture facility was measured. The energy associated with heating of the sorbent particles and desorption was 141kJ/mol or 3.2GJ/t at a working capacity of 1.2mol/kg. At working capacities of 2.7mol/kg the heat demand was reduced to values below 2GJ/t.

Simultaneous in Situ X-ray Diffraction and Calorimetric Studies as a Tool To Evaluate Gas Adsorption in Microporous Materials

Combined application of in situ X-ray diffraction (XRD) and differential scanning calorimetry (DSC) is a novel technique for rapidly evaluating the suitability of microporous materials for postcombustion CO2 capture. Further, while many microporous materials show promise for CO2 capture, most are not evaluated in the presence of water vapor, a major component of postcombustion flue gas. As a demonstration of the versatility of XRD-DSC techniques, representatives of the classes of materials typically proposed for CO2 capture, zeolites, and metal–organic frameworks (MOFs) were studied: zeolite NaX, Ni-MOF-74 [Ni2(dobdc); dobdc = 2,5-dihydroxyterephthalate], ZIF-7 [ZIF: zeolitic imidazole framework, Zn(phim)2; phim: benzimidazole], and SBMOF-1 [Ca(sdb); sdb: 4,4′-sulfonyldibenzoate]. Although NaX and Ni-MOF-74 show very high affinity toward CO2 under idealized dry conditions, they are also very sensitive to the presence of water vapor and experience significant performance loss above 25% relative humidity (RH) at room temperature. Relative to NaX and Ni-MOF-74, ZIF-7 and SBMOF-1 show strong CO2 affinity even in the presence of 75% RH and may be more ideally suited for postcombustion flue gas CO2 capture than compounds with unsaturated metal sites. XRD-DSC is particularly powerful for evaluating the consequences of framework flexibility, with XRD providing the signature indicative of the structural rearrangement and the DSC providing the enthalpies of adsorption for each structure. This kind of detailed energy evaluation is not possible with other noncalorimetric methods.

Role of Surfactants in Promoting Gas Hydrate Formation

Gas hydrates have been proposed as a potential technology for a number of applications, such as separation of gas mixtures, CO2 capture, transportation, and sequestration, methane storage and transport, and seawater desalination. Most of these applications will benefit from reduced induction time of hydrate nucleation, enhanced hydrate growth rate, and maximum water-to-hydrate conversion. The addition of surfactants to the gas–water system serves this purpose in a very effective manner. This review focuses on different surfactants that were utilized for gas hydrate formation studies; insights have been provided on the possible mechanisms of action through which these surfactants affect hydrate formation kinetics. A thorough analysis of the existing literature on surfactants suggests that enhanced rate of hydrate nucleation and growth kinetics may not be directly linked to micelle formation. Conversely, reduced surface tension in the presence of surfactants not only enhances the mass transfer but also chan...

Integration of a Gas Switching Combustion (GSC) system in integrated gasification combined cycles

Chemical Looping Combustion (CLC) is a promising technology for achieving economically viable CO2 capture from fossil fuel energy conversion processes. However, complexities and costs surrounding the standard interconnected fluidized bed concept for CLC have prompted the investigation of alternative process configurations. This paper investigates one such configuration, Gas Switching Combustion (GSC), via combined reactor and process modelling. The GSC concept utilizes a standard bubbling/turbulent fluidized bed reactor where an oxygen carrier material is alternatively exposed to feeds of air and fuel (syngas from coal gasification in this case). This configuration maintains the good mixing characteristics of fluidized bed reactors while eliminating the solids handling challenges related to the standard dual fluidized bed system. It was shown that a cluster of GSC reactors operating in a well-controlled manner could supply sufficiently steady streams to a downstream gas turbine and CO2 purification and compression unit. The simplest configuration where fuel and air are fed alternatively to the reactors, with steam purging but no advanced heat management procedures returned a significantly higher electric efficiency (40.7%) than a baseline IGCC plant with currently available gas turbine and CO2 capture technology (35.3%), while also achieving slightly higher overall CO2 avoidance. It was also shown that there exists significant scope for trading further increases in electric efficiency for reductions in overall CO2 avoidance through adjustment of the reactor operating strategy. More complex purging and heat management strategies could further improve the electric efficiency to as high as 41.9%, with overall CO2 avoidance higher than 90%.

CO2 Sorption by Hydrotalcite-Like Compounds in Dry and Wet Conditions

Abstract A pre-combustion removal option, coupling water–gas shift and CO2 capture is the well-known sorption-enhanced water–gas shift (SEWGS): the removal of CO2 produced by WGS reaction, shifting the thermodynamic equilibrium, enhances H2 production. Among the different CO2 sorbents, hydrotalcite-like compounds work at the required intermediate temperature (T = 200–400°C). Using low supersaturation method, three different sorbents were synthesized. Sieved fractions were impregnated with 20%w/w K2CO3 and then dried and subjected to thermal treatment. Sample characterization was performed by means of FT-IR spectroscopy, XRD analysis and TG-DTA analysis. Sample analysis was carried out after synthesis, thermal treatment (calcination) and after fixed bed reactor capture tests. Sorption and desorption tests were performed in a fixed bed microreactor, under cyclic conditions, at temperature level of T = 350°C and P = 5 bar in dry and wet condition. The amount of CO2 captured by the sorbent in each test was quantified by means of a first order with dead time flow distribution model applied to the experimental system. Sorption capacity of sorbents in dry conditions increases of 30% with respect to previous atmospheric pressure results obtained in fluidized bed. These sorbents seem to be good candidates to be used as a bi-functional sorbent-catalyst for SEWGS.

Life-cycle GHG assessment of carbon capture, use and geological storage (CCUS) for linked primary energy and electricity production

Carbon capture, use and geological storage (CCUS) could be feasible when fossil fuel-power plants are close to oil and gas reservoirs where CO2-enhanced oil recovery (EOR) technologies are applicable. In this research, we used a novel “well-to-well” approach that included the operations from natural gas production at oil field to CO2 injection for EOR operations at depleted oil fields. This paper includes estimates for greenhouse gas (GHG) emissions arising from a hypothetical CCUS case with a natural gas combined cycle power plant (NGCC) and Global Warming Potential (GWP) impact, by using Life-Cycle Assessment (LCA) methodology. Our research comprises a comparison with other electricity-generation technologies, including super critical pulverized carbon (SCPC), NGCC without CO2 capture, geothermal, mini-hydro, wind and nuclear. The LCA stages that were undertaken in this study were natural gas supply system, electricity generation, CO2capture, CO2transport, EOR operations and environmental monitoring. Three different functional units were used in this study: MJ, kWh and produced oil barrel (bbl). Results indicate that the energy produced by the described CCUS system had an environmental impact on climate change (global warming potential) of 0.044kg CO2e/MJ. The NGCC power plant with carbon capture unit would produce 0.177kg CO2e/kWh, representing about 21% and 36% of the estimated values for the SCPC and NGCC (without CCS) cases respectively, and about 24% less greenhouse gas emissions than the geothermal scenario. The oil produced in the EOR stage had a greenhouse gas emission rate of 38kg CO2e per oil barrel and 251kg CO2e per oil barrel in the whole CCUS system.

Direct Carbonization of Cyanopyridinium Crystalline Dicationic Salts into Nitrogen-Enriched Ultra-Microporous Carbons toward Excellent CO2 Adsorption.

A family of nitrogen-enriched ultramicroporous carbon materials was prepared by direct carbonization of task-specifically designed molecular carbon precursors of cyanopyridinium-based crystalline dicationic salts (CISs). Varying the molecular structure of CISs, large surface area (918 m(2) g(-1)), high N content (20.10 wt %), and narrow distributed ultramicropores (0.59 nm) can be simultaneously achieved on the sample PCN-14 derived from methyl-linked 4-cyanopyridinium D[4-CNPyMe]Tf2N. It therefore exhibited exceptional performance in greenhouse gas CO2 capture, i.e., simultaneously possessing (1) high CO2 adsorption uptakes: 5.33 mmol g(-1) at 273 K, and 3.68 mmol g(-1) at 298 K (both at 1.0 bar); (2) unprecedented selectivity of CO2 versus N2: 156; and (3) a high adsorption ratio of CO2 to N2: 148 (at 1.0 bar). This is the first time such a high selectivity and adsorption ratio over carbon materials has been achieved, which is among the highest values over solid adsorbents.

Performance comparison of two low-CO 2 emission solar/methanol hybrid combined cycle power systems

Abstract Two novel hybrid combined cycle power systems that use solar heat and methanol, and integrate CO2 capture, are proposed and analyzed, one based on solar-driven methanol decomposition and the other on solar-driven methanol reforming. The high methanol conversion rates at relatively low temperatures offer the advantage of using the solar heat at only 200–300 °C to drive the syngas production by endothermic methanol conversions and its conversion to chemical energy. Pre-combustion decarbonization is employed to produce CO2-free fuel from the fully converted syngas, which is then burned to produce heat at the high temperature for power generation in the proposed advanced combined cycle systems. To improve efficiency, the systems’ configurations were based on the principle of cascade use of multiple heat sources of different temperatures. The thermodynamic performance of the hybrid power systems at its design point is simulated and evaluated. The results show that the hybrid systems can attain an exergy efficiency of about 55%, and specific CO2 emissions as low as 34 g/kW h. Compared to a gas/steam combined cycle with flue gas CO2 capture, the proposed solar-assisted system CO2 emissions are 36.8% lower, and a fossil fuel saving ratio of ∼30% is achievable with a solar thermal share of ∼20%. The system integration predicts high efficiency conversion of solar heat and low-energy-penalty CO2 capture, with the additional advantage that solar heat is at relatively low temperature where its collection is cheaper and simpler. The systems’ components are robust and in common use, and the proposed hybridization approach can be also used with similar benefits by replacing the solar heat input with other low heat sources, and the system integration achieves the dual-purpose of clean use of fossil fuel and high-efficiency conversion of solar heat at the same time.

Modeling of the dissociation conditions of H2 + CO2 semiclathrate hydrate formed with TBAB, TBAC, TBAF, TBPB, and TBNO3 salts. Application to CO2 capture from syngas

Syngas produced from coal gasification or methane reforming contains a significant amount of carbon dioxide (CO2) that has to be removed. Semiclathrate hydrates have been considered as a possible medium for gas separation and CO2 capture. Here, we apply Paricaud's approach [J. Phys. Chem. B 2011, 115, 288–299] to model the dissociation conditions of hydrogen (H2) + CO2 semiclathrate hydrates formed with tetra-n-butyl ammonium bromide (TBAB), tetra-n-butyl ammonium chloride (TBAC), tetra-n-butyl ammonium fluoride (TBAF), tetra-n-butyl phosphonium bromide (TBPB), and tetra-n-butyl phosphonium nitrate (TBANO3). A very good description of the melting temperatures of H2 semiclathrate hydrates is obtained over wide ranges of pressure and salt composition. It is predicted that the H2 storage capacities of semiclathrate hydrates is rather low (about 0.05 wt% at 4 MPa), showing that semiclathrate hydrates are not good candidates to store H2. However, high separations factors are predicted at moderate salt concentrations, confirming the possibility of using semiclathrate hydrates to separate H2 and CO2. It is predicted that the dissociation conditions of semiclathrates in presence of gas mixture significantly depend on the global composition of the mixture: in particular, the melting point is changed by varying the initial amount of water even if the global mole fraction ratio between H2 and CO2 is kept constant. It is shown that an increase of the salt concentration gives rise to a decrease of the separation factor, and the sudden drop of CO2 capture observed for high salt concentrations is explained by a change of hydrate structure.

High Efficiency SOFC Power Cycles With Indirect Natural Gas Reforming and CO2 Capture

Driven by the search for the highest theoretical efficiency, several studies have investigated in the last years the adoption of fuel cells (FCs) in the field of power production from natural gas with CO2 capture. Most of the proposed power cycles rely on high temperature FCs, namely, solid oxide FCs (SOFCs) and molten carbonate FCs (MCFCs), based on the concept of hybrid FC plus gas turbine cycles. Accordingly, high temperature FCs are integrated with a simple or modified Brayton cycle. As far as SOFCs are concerned, CO2 can be separated downstream the FC via a range of available technologies, e.g., chemical or physical separation processes, oxy-combustion, and cryogenic methods. Following a literature review on promising plant configurations, this work investigates the potential of adopting an external natural gas conversion section with respect to the plant efficiency. As a reference plant, we considered a power cycle proposed by Adams and Barton (2010, “High-Efficiency Power Production From Natural Gas With Carbon Capture,” J. Power Sources, 195(7), pp. 1971–1983), whose performance is the highest found in literature for SOFC-based power cycles, with 82% LHV electrical efficiency. It is based on a prereforming concept where fuel is reformed ahead the SOFC, which thus works with a high hydrogen content fuel. After reproducing the power cycle with the ideal assumptions proposed by the original authors, as second step, the simulations were focused on revising the power cycle, implementing a complete set of assumptions about component losses and more conservative operating conditions about FC voltage, heat exchangers minimum temperature differences (which were previously neglected), maximum steam temperature (set according to heat recovery steam generator (HRSG) practice), turbomachinery efficiency, component pressure losses, and other adjustments. The simulation also required to design an appropriate heat exchangers network, which turned out to be very complex, instead of relying on the free allocation of heat transfer among all components. Considering the consequent modifications with respect to the original layout, the net electric efficiency changes to around 63% LHV with nearly complete (95%+) CO2 capture, a still remarkable but less attractive value. On the other hand, the power cycle requires a complicated and demanding heat exchangers network and heavily relies on the SOFC performances, not generating a positive power output from the gas turbine loop. Detailed results are presented in terms of energy and material balances of the proposed cycles. All simulations have been carried out with the proprietary code GS, developed by the GECOS group at Politecnico di Milano.

음이온교환수지를 이용한 CO2흡수 공정시 발생하는 열안정성염 처리 특성

In this study, we studied the characteristics of ion exchange for treatment of HSS (heat stable salts) which cause performance reduction in CO2 gas capture amine solution using anion exchange resins. The optimum HSS removal efficiency, 96.1% was obtained when using strong base anion exchange resin SAR10 at dosage 0.05 g/mL, 316 K, pH 12 and the best resin regeneration efficiency, 78.8% was obtained using NaOH solution of 3 M at 316 K. The adsorption data were described well by the Freundlich model and the sorption intensity(n) was 2.0951 lying within the range of favorable adsorption. The adsorption selectivity coefficients were increased by increasing valences and size of ion and desorption selectivity coefficients showed a contradictory tendency to adsorption selectivity coefficients. By continuous HSS removal experiments, 13.3 BV of HSS con- taminated solution was effectively treated and the optimum NaOH solution consumption was 5.2 BV to regenerate resins.

CO2 capture in humid gas using ZnO/activated carbon and ZnO reactivity with CO2

Carbon dioxide capture with ZnO/activated carbon adsorbates and reactivity of ZnO particle with CO2 are discussed for the effective CO2 capture in humid exhaust gas. Coarse ZnO particles (d = 670 nm), and small diameters, d < 20 nm, of zinc oxide particles on activated carbon supports were prepared. The amounts of CO2 adsorbed on ZnO particles and activated carbon supports were measured and calculated. The calculated value and thermal gravimetric analysis results indicate that only the surface layer (<0.5 nm) of ZnO particles reacts with CO2 and H2O for all sizes of ZnO particles. These results lead to the conclusion that ZnO reactivity with CO2 is still independent of the particle size even in the small diameters in this study. The results quantitatively present the gas-phase carbonation rate of ZnO and its independency on the particle diameter for the first time. This research sheds light on the difficulty in using ZnO as CO2 adsorbent. Some possible solutions for the difficulty are also discussed in view of enhancing of its reactivity.

Guest gas enclathration in tetra-n-butyl ammonium chloride (TBAC) semiclathrates: Potential application to natural gas storage and CO2 capture

The enclathration of guest gases such as CH4 and CO2 in tetra-n-butyl ammonium chloride (TBAC) semiclathrates and their potential application to natural gas storage and CO2 capture were examined with a primary focus on stability condition measurements and cage filling characteristics. The phase behaviors clearly demonstrated that the double CH4 (or CO2)+TBAC semiclathrates yielded a significantly enhanced thermodynamic stability. In particular, the highest stabilization occurred at 3.3mol%, the stoichiometric concentration of TBAC·29.7H2O. The cage-dependent 13C NMR chemical shift identified CH4 molecules enclathrated in the small 512 cages of the double TBAC semiclathrates. CO2 inclusion in the double TBAC semiclathrate was also confirmed using Raman spectroscopy. In addition, the dissociation enthalpy and the dissociation temperature of the TBAC semiclathrate under atmospheric pressure were measured to be 204.8±1.7J/g and 288.0K, respectively, by a differential scanning calorimeter. The experimental results demonstrate that TBAC semiclathrates can potentially be used for gas storage and CO2 capture due to their high thermodynamic stability and favorable enclathration characteristics of guest gases.

Parameters optimization for direct flue gas CO2 capture and sequestration by aqueous mineral carbonation using activated serpentinite based mining residue

Naturally occurring mineral carbonation can significantly reduce GHG emissions. Adapting the reaction in order to sequester post combustion CO2 is a potential industrial mitigation pathway, but such a process must be chemically and economically efficient. Research to date has focused on reacting a concentrated CO2 stream with alkaline rocks. Significant carbonation rates where reached but required a system operating at high pressure and temperature. This article describes the parameter optimization for direct flue gas CO2 capture and sequestration when using finely-ground, heat-activated serpentine derived from mining residues. The gas is contacted with the minerals in an aqueous phase at ambient temperature and moderate pressure (10.5bar). Once the solution is saturated with dissolved CO2 and Mg, it is filtered and carbonates precipitated in a downstream operation. The solid is mixed with fresh water and recirculated to treat more gas until no further Mg can be leached from the solid media. Reaction parameters such as the pulp density, the volumetric ratio of gas to liquid, the reaction time and the particle size were investigated with a 18.2% CO2 gas stream in a batch mode. This innovative approach permits the use of moderate temperature and pressure conditions and the production of pure MgCO3 with a potential sale value. After parameter optimization, batch mode tests showed that 64 wt.% of the Mg could be leached from the solid and that 62.5 wt.% of the CO2 removed from the gas phase giving a ratio of 0.28kg of CO2 sequestered per kg of residues.