Cyclic CO2 Capture Research Articles

Coupled CO2 capture and thermochemical heat storage of CaO derived from calcium acetate

AbstractCaO/Ca(OH)2 thermochemical heat storage (THS) technology is considered to be one of the most promising technologies for large‐scale solar energy storage. However, the THS performance of raw CaO‐based materials decreases during multiple cycles. In this work, CaO derived from calcium acetate (Ac‐CaO) is prepared and applied to a coupled system that achieved simultaneous CaO/Ca(OH)2 THS and CO2 capture. The CO2 capture and THS performances of Ac‐CaO are always higher than those of calcined limestone owing to the preferable pore structure, whereas Ac‐CaO exhibits decreasing CO2 capture and THS performance resulting from sintering and the formation of CaCO3 from CaO or Ca(OH)2 with ambient CO2 during air cooling, respectively. In the coupled CaO/Ca(OH)2 THS and CO2 capture system, Ac‐CaO is subjected to 10 CO2 capture cycles, 30 THS cycles, 1 CO2 capture cycle, 10 THS cycles, 1 CO2 capture cycle, and 10 THS cycles sequentially. The hydration and dehydration conversions of Ac‐CaO in the 31st THS cycle reach 91.7 and 93.6%, respectively, which are 1.6 and 1.6 times higher than those recorded prior to the 11th CO2 capture cycle owing to the decomposition of CaCO3 during calcination. The carbonation conversion of Ac‐CaO achieves 89.9% in the 11th CO2 capture cycle, which is 22.3% higher than that recorded prior to the 10 THS cycles owing to reactivation from the hydration process during THS. The CO2 capture and CaO/Ca(OH)2 THS processes are enhanced in the coupled system using Ac‐CaO; therefore, the coupled system appears promising for CaO/Ca(OH)2 THS and CO2 capture. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Metal-oxide stabilized CaO/CuO composites for the integrated Ca/Cu looping process

An integrated Ca/Cu looping process has been proposed recently for CO2 capture. It uses the exothermic in-situ reduction of CuO with methane or natural gas to supply the heat required for the endothermic calcination of CaCO3 to regenerate CaO for the following CO2 sorption cycle via bifunctional CaO/CuO composites. CaO/CuO composites possess excellent redox characteristics, but the rapid decline in CO2 capture performance remains an unresolved problem. Two different types of stabilizers, i.e., Al2O3 that can form a mixed phase with CaO, and MgO that does not form a mixed phase with CaO under reaction conditions, were incorporated into CaO/CuO composites via a Pechini method, and investigated by thermogravimetry. The results showed that the incorporation of Al2O3 or MgO enhanced cyclic stability significantly, and the formation of calcium-aluminum mixed oxides improved the cyclic CO2 capture stability more than did MgO. The best performing Al2O3- and MgO-stabilized CaO/CuO composites exhibited CO2 uptake of 0.14 and 0.09 gCO2/gmaterial after ten repeated cycles, exceeding the unstabilized CaO/CuO composites by 100% and 29%, respectively. We observed that 15 mol. % Al2O3 is the optimal quantity for Al2O3-stabilized CaO/CuO composites, ensuring a high and cyclically stable CO2 uptake capacity (0.11 gCO2/gmaterial after 45 cycles). Moreover, the cyclic stability was enhanced remarkably with increasing carbonation/oxidation temperature (from 550 to 750 °C). In-situ X-ray powder diffraction results suggest that the intermediate phase Cu2O played an important role in the enhanced performance of the composites at high carbonation/oxidation temperatures.

Catalytic Toluene Reforming with In Situ CO2 Capture via an Iron–Calcium Hybrid Absorbent for Promoted Hydrogen Production

A two‐step sol–gel method is adopted to prepare an iron–calcium hybrid absorbent (Ca–Al–Fe) integrating iron catalysis component and inert support with CaO for calcium looping gasification. Effects of Ca–Al–Fe on cyclic CO2 capture reactivity, mechanical strength, and enhanced reforming of biomass tar model component (toluene) are investigated by comparing with three reference absorbents. Results show that main components of Ca–Al–Fe are CaO, mayenite (Ca12Al14O33), and brownmillerite (Ca2Fe2O5). Ca12Al14O33 plays key roles in keeping stable cyclic carbonation reactivity and significantly promotes mechanical strength of the novel absorbent. In comparison with other absorbents without coupling Ca12Al14O33 or Ca2Fe2O5, Ca–Al–Fe approaches the highest toluene conversion (around 60%) and has the lowest coke deposition (12.2 mg g−1), due to the synergetic influences of Ca2Fe2O5 and Ca12Al14O33, which significantly promotes hydrogen production while reducing CO2 yield in reforming syngas. In addition, influences of reaction conditions such as iron loading, reaction temperature, molar ratio of H2O to carbon in toluene, and absorbent particle size on toluene reforming are examined in the presence of Ca–Al–Fe. Potential reaction routes of toluene reforming are also analyzed and discussed.

SO2 removal performances of Al- and Mg-modified carbide slags from CO2 capture cycles at calcium looping conditions

In this work, the SO2 removal performances of the aluminum- and the magnesium-modified carbide slags fabricated by the combustion synthesis from CO2 capture cycles at the calcium looping conditions were investigated in a thermogravimetric analyzer and a dual fixed-bed reactor. The effects of sulfation temperature, number of CO2 capture cycles and calcination condition on the SO2 removal performances of Al- and Mg-modified carbide slags experienced the multiple CO2 capture cycles were studied. The sulfation temperature in the range of 800–950 °C shows a little effect on SO2 removal capacities of Al- and Mg-modified carbide slags experienced the multiple CO2 capture cycles. As the number of CO2 capture cycles increases, the sulfation conversions of the original and modified carbide slags decrease rapidly. However, Al- and Mg-modified carbide slags possess obviously higher SO2 removal capacity and cyclic stability than original carbide slag due to the good supports Ca3Al2O6 and MgO, respectively. And the larger surface areas and volumes of pores in 5–20 nm in diameter of Al- and Mg-modified carbide slags promote the higher SO2 removal capacity than original carbide slag. The modified carbide slag shows higher sintering resistance in high concentration of steam calcination condition during the CO2 capture cycles, compared with high concentration of CO2 calcination condition. Therefore, Al- and Mg-modified carbide slags from CO2 capture cycles based on calcium looping calcined under high steam concentration achieve SO2 removal capacities.

Introducing a hybrid mechanical – Chemical energy storage system: Process development and energy/exergy analysis

The purpose of this study is to develop and introduce a novel hybrid energy storage system composed of compressed air energy storage cycle as mechanical storage and amine assisted CO2 capture cycle as chemical energy storage. The novelty of this study is to increase the efficiency of mechanical storage cycle by using chemical storage and in this way, the heat released and absorbed by the chemical cycle is used. Two methods of first and second law examination are used to study proposed system. In particular, this energy storage system that stores energy by simultaneously compressing a gas to a higher enthalpy state and recovering the heat of compression by driving a somewhat reversible chemical reaction. The heat energy in the chemical reaction is then recovered while the gas is expanding to a lower enthalpy state. Reboiler of the desorption column requires 1600 kW heat and the power produced by the turbines and consumed by the compressors is 2400 kW and 3884 kW, respectively. Also, the flow rate of the mechanical storage working fluid is 1773 kgmole/h and the storage temperature and pressure are 100 °C and 25 MPa, respectively. In this study, Aspen HYSYS and MATLAB software were used simultaneously for simulation and the results show that round-trip efficiency and exergy efficiency are 51.45% and 72.16%, respectively. Finally, the effect of the various parameters such as fluids inlet temperature to absorption column, CO2 loading and storage temperature on round trip efficiency and exergy efficiency are investigated.

Simultaneous NO/SO2 removal by coconut shell char/CaO from calcium looping in a fluidized bed reactor

A simultaneous NOx/SO2 removal system using bio-char and CaO combined with calcium looping process for CO2 capture was proposed. The simultaneous NO/SO2 removal performance of coconut shell char/CaO experienced CO2 capture cycles was investigated in a fluidized bed reactor. The effects of reaction temperature, mass ratio of CaO to coconut shell coke, CaO particle size and number of CO2 capture cycles from calcium looping process were discussed. The NO removal efficiency of char is improved under the catalysis of CaO. The reaction temperature plays an important role in the simultaneous NO/SO2 removal. Coconut shell char/CaO achieve the highest NO and SO2 removal efficiencies at 825 oC, which are 98% and 100%, respectively. The mass ratio of CaO to coconut shell char of 60: 100 is a good choice for the simultaneous NO/SO2 removal. Smaller CaO particle size contributes to higher NO and SO2 removal efficiencies of coconut shell char/CaO. The NO and SO2 removal efficiencies of coconut shell char and cycled CaO from calcium looping declined slightly with the number of CO2 capture cycles. In addition, the Ca-based materials balance in process of simultaneous NOx/SO2 removal combined with calcium looping is given. The novel simultaneous NO/SO2 removal method using bio-char and cycled CaO from calcium looping process appears promising.

A novel hybrid iron-calcium catalyst/absorbent for enhanced hydrogen production via catalytic tar reforming with in-situ CO2 capture

An iron-calcium hybrid catalyst/absorbent (Ca–Al–Fe) is developed by a two-step sol-gel method to enhance tar conversion, cyclic CO2 capture and mechanical strength of absorbent for hydrogen production in calcium looping gasification. The developed catalyst/absorbent consists of CaO and brownmillerite (Ca2Fe2O5) with mayenite (Ca12Al14O33) as inert support. Comparing with three candidate absorbents without Ca2Fe2O5 or Ca12Al14O33, cyclic carbonation reactivity and mechanical strength of Ca–Al–Fe are largely promoted. Meanwhile, Ca–Al–Fe approaches the maximum conversion rate of 1-methyl naphthalene (1-MN) with enhanced hydrogen yield around 0.15 mol/(h·g) under reforming conditions of present study. Ca–Al–Fe also shows the largest CO2 absorption and lowest coke deposition. Influences of operation variables on 1-MN reforming are evaluated and recommended conditions can be iron to CaO mass ratio of 10%, reaction temperature of 800 °C and steam to carbon in 1-MN mole ratio of 2.0. Ca–Al–Fe hybrid catalyst/absorbent presents good potential to be applied in future.

Microemulsion-derived, nanostructured CaO/CuO composites with controllable particle grain size to enhance cyclic CO2 capture performance for combined Ca/Cu looping process

Abstract Combined Ca/Cu looping process is a very most promising CO2 capture technology, in which chemical looping combustion provides the heat for calcining CaCO3 in calcium looping by employing CaO/CuO composites. However, such CaO/CuO composites demonstrated a fast decay in CO2 uptake capacity during cyclic operation. In order to solve this problem, nanostructured CaO/CuO composites was synthesized using a microemulsion method in this work. The synthetic parameters, including the mole ratio of water to surfactant and mole concentration of precursors, were investigated systematically for the microemulsion system. A fixed-bed reactor was used to assess the redox characteristics and CO2 capture performance. The results showed that the particle grain size of the nanostructured CaO/CuO composites can be controlled by the variation of the mole ratio of water to surfactant. With the increase in the mole ratio of water to surfactant from 9 to 23, the mean particle grain size of the CaO/CuO composites increased from 0.19 to 0.57 μm. A high mole concentration of precursors also resulted in a much enhanced CO2 capture performance. Compared to the successive fast CO2 uptake decay for the reference CaO/CuO composites developed by a conventional co-precipitation method, the CaO/CuO composites fabricated by the microemulsion method demonstrated an increasing CO2 uptake in the initial cycles followed by a relatively slow decline in the subsequent cycles, exceeding uptake of the reference material by 104% after 19 cycles. The kinetic analysis showed that the CaO/CuO composites fabricated by the microemulsion method had much lower activation energy than the reference material.

Bubbling synthesis and high-temperature CO2 adsorption performance of CaO-based adsorbents from carbide slag

Carbide slag used as low-cost adsorbents for high-temperature CO2 capture has widely researched; however, the sintering at high calcination temperature often resulted in an obvious decay of CO2 capture performance after multiple CO2 capture cycles. In this work, a new strategy of synthetic CaO-based adsorbents from carbide slag via the bubbling approach was reported to stabilize the pore structure of adsorbents, to improve the sintering resistance of adsorbents and to boost the CO2 adsorption capacity. Therefore, the influences of bubbling rate, stirring rate, reaction temperature, and carbide slag dosage on CO2 adsorption capacity of CaO-based adsorbents were systemically investigated at 750 °C for 1 h. The synthetic CaO-based adsorbent from carbide slag on the basis of following conditions: 200 sccm of CO2 bubbling, 1100 rpm/stirring, 40 °C of reaction temperature and 5 g of carbide slag dosage, presented the highest CO2 adsorption capacity of 619.8 mg/g and 542.6 mg/g in the 1st and 15th cycles, which were about 6.6% and 33.9% higher than that of original carbide slag (CS). This significant improvement in CO2 uptake capacity is due to more stable interconnected and 2–5 nm porous structure in the as-prepared CaO-based adsorbent, which outstandingly lowered down the sintering of adsorbents and stabilized the CO2 adsorption capacity during multiple CO2 capture cycles.

Reactivation mode investigation of spent CaO-based sorbent subjected to CO2 looping cycles or sulfation

Rapid loss-in-capacity of naturally occurring limestone for CO2 capture is the most prominent issue in the calcium looping process. The synthesis of highly efficient sintering-resisting sorbents is a common solution to mitigate capacity decay. However, the long-term CO2 looping cycles, particularly in the presence of SO2, still cause the generation of large amounts of spent CaO-based sorbents. Comparatively, the reactivation of spent sorbent is more economical than the replenishing of fresh sorbent. In this work, three types of reactivation modes (i.e., hydration, simultaneous hydration/ impregnation and acidification) were applied to recover the CO2 capture capacities of the spent, synthetic CaO-based sorbents (CaO/MgO = 75 wt%/25 wt%). It is found that hydration is effective to recover the cyclic CO2 capture performance of the spent sorbent due to the formation of more cracks and channels that extend to the interior of sorbent particles. Therefore, the sorbent reactivated via sole hydration exhibits a high capacity of 0.390 g/g after 40 cycles. Moreover, NaCl impregnation combined with hydration produce lager amounts of macropores within the reactivated sorbents after initial sever sintering that are responsible for their desirable CO2 capture stability. The introduction of filtration during acidification reactivation process can effectively enhance the initial CO2 capture capacity (an improvement percentage of ~14.7%) owing to the removal of the irreversible CaSO4.

Review and techno-economic assessment of fuel cell technologies with CO2 capture

The concept of using Fuel Cells (FCs) within large scale power generation cycles for CO2 capture has been studied over the last decade. Two types of FCs, Solid Oxide Fuel Cells (SOFCs) and Molten Carbonate Fuel Cells (MCFCs) have emerged as promising CO2 capture systems, with the added advantage of additional power production. Although promising, neither SOFCs nor MCFCs are commercially available for CO2 capture applications, primarily due to low technological maturity, lack of large demonstration projects, and significant associated costs.In this work, the aim is to provide a comprehensive literature review of Fuel Cell technologies with CO2 Capture and a techno-economic analysis of five selected cases utilising SOFCs and MCFCs as CO2 capture systems in power plants. Economic parameters were homogenised to enable a fair comparison between the technologies. Results show that Cases 1 and 5 which consider MCFCs as CO2 concentrator’s in Natural gas and super critical pulverised coal cycles respectively give the best LCOE performance. The LCOE is comparable to current state-of-the-art CO2 capture technologies applied to large-scale power plants.

Steam-Stable Basic Immobilized Amine Sorbent Pellets for CO2 Capture Under Practical Conditions.

Pelletization of basic immobilized amine sorbent (BIAS) particles is required to improve their mechanical strength and facilitate their practical CO2 capture application under fixed or dynamic reactor conditions. Herein, we utilized two methods to prepare amine-functionalized BIAS pellets. Method (ii-a) involved combining latex polychloroprene (PC)/polyamine solutions with fly ash (FA)/BIAS powder to form sorbent pellets. Alternatively, method (ii-b) entailed shaping and drying wet pastes of binder solution plus FA/SiO2 powder into pellet supports. These supports were then functionalized with leach-resistant polyethylenimine MW = 800 (PEI800)/N-N-diglycidyl-4-glycidyloxyaniline (tri-epoxide cross-linker, E3) or ethylenamine E100/E3 mixtures. All pellets were screened for CO2 capture by thermogravimetric analysis (dry 14% CO2/N2, 55-75 °C), H2O stability by accelerated water washing, and mechanical strength by crush and ball-mill attrition testing. The mechanism of superior method (ii-b) pellet formation was uncovered by N2 physisorption measurements, diffuse reflectance infrared Fourier transform spectroscopy, and scanning electron microscopy. Extended fixed bed testing of optimum E3/PEI800-0.13/1 pellets under practical conditions revealed complete CO2 capture stability of 1.5 mmol CO2/g after 48 h of continuous steam exposure (7.2% H2O/He, 105 °C) and minimal 14.6% loss in capacity after 75 hours of combined CO2 capture cycling and steam treating (48 h). This slight oxidative degradation could be alleviated by incorporating a K2CO3 antioxidant into the pellet formulation. Overall, the robust physiochemical properties of the polyamine/cross-linker method (ii-b) pellets confirm their suitability for pilot-scale testing.

PH Swing Cycle for CO2 Capture Electrochemically Driven through Proton-Coupled Electron Transfer

We propose and perform a thermodynamic analysis of the energetic costs of CO2 separation from flue gas using a pH swing created by electrochemical redox reactions involving proton-coupled electron transfer from molecular species in aqueous electrolyte. Electrochemical reduction of these molecules results in the formation of alkaline solution, into which CO2 is absorbed; subsequent electrochemical oxidation of the reduced molecules results in the acidification of the solution, triggering the release of pure CO2 gas. We examined the effect of buffering from the CO2-carbonate system on the solution pH during this pH swing cycle, and thus on the open-circuit potential of a hypothetical electrochemical cell in a 4-step CO2 capture-release cycle. The thermodynamic minimum work input varies from 16 to 75 kJ/molCO2 as throughput increases, for both flue gas and direct air capture, with the potential to go substantially lower if CO2 capture or release is performed simultaneously with electrochemical reduction or oxidation. These values are compared with those for other separation methods. We also discuss the properties required of molecules that would be suitable for such a cycle, and preliminary experimental data from a cycle run using one such molecule.

Feasibility of CO2 Capture from O2-Containing Flue Gas Using a Poly(ethylenimine)-Functionalized Sorbent: Oxidative Stability in Long-Term Operation.

Amine-functionalized sorbents are investigated widely for CO2 capture from flue gas, to mitigate the crisis of global CO2 emission, with the advantages of excellent adsorption and regeneration performance. However, the presence of O2 in flue gas (3-10%) would induce the degradation of the sorbents, and some previous works proposed the strategies at the sacrifice of partial CO2 adsorption capacity. Herein, we focused on the oxidation behavior of PEI-functionalized silica in the long-term operation and analyzed the degradation mechanism by characterizing the oxidized sorbents. The sorbent proved to be oxidative stable under a lower temperature of air exposure, but the oxidative degradation would indeed occur at more harsh temperatures (above 90 °C). This study demonstrated that CO2 capture from O2-containing flue gas was feasible by controlling the operating temperature (below 75 °C), and the effective capacity of above 135 mg/g could be maintained in the cyclic CO2 capture.

Preparation of spherical Li4SiO4 pellets by novel agar method for high-temperature CO2 capture

Li4SiO4 sorbents have received extensive attention in the field of high-temperature CO2 capture due to lower regeneration temperatures and good cyclic durability. The granulation of the sorbent powder is a necessary prerequisite for the practical application of Li4SiO4 in the removal of CO2 from the industrial exhaust gas. This study, for the first time, proposed a facile agar method to achieve the single-step synthesis of spherical Li4SiO4 pellets. The prepared Li4SiO4 pellets presented a high degree of sphericility and uniform diameter ranges of 3–4 mm. The characterization results indicated that the pellets exhibited improved microstructures with loose morphology and enhanced specific surface areas. It was believed that the burning of agar at high temperatures released large volumes of gases in a short time and, thus, led to the formation of massive pore channels. The burning out of the well-dispersed fine agar powder left rich porosity in situ for the pellets. As a result, the granulated pellets showed higher CO2 sorption capacities than the corresponding sorbent powder during the cyclic tests. In addition, during the prolonged sorption/desorption cycles, the prepared pellets displayed excellent cyclic durability and high sorption capacities (>0.330 g CO2/g sorbent). The mechanical strengths of the pellets were also evaluated and during 1000 rotations in the friability test, the pellets exhibited the weight loss lower than 10 wt%. In general, the single-step agar method is suitable for the production of Li4SiO4 pellets for cyclic CO2 capture.

Mode investigation of CO2 sorption enhancement for titanium dioxide-decorated CaO-based pellets

The rapid loss-in-capacity and severe attrition are easily encountered for CaO-based sorbent during multiple CO2 capture cycles. It is necessary to prepare the CaO-based CO2 capture sorbent with high capability for CO2 uptake and attrition resisting. In this work, the TiO2-decorated CaO-based sorbent pellets were prepared via extrusion-spheronization, and three different modification modes (i.e., dry-mixing, wet-mixing and hydration-mixing) were applied. This paper lay emphasis oninvestigating the modification mode on affecting the cyclic CO2 uptake and anti-attrition ability of TiO2-decorated CaO-based sorbent pellets. It is found that hydration-mixing is superior to dry-mixing and wet-mixing on modifying the CO2 capture performance of TiO2-decorated CaO-based sorbent pellets. The TiO2-decorated CaO-based sorbent pellets containing 20 wt% of TiO2 prepared via hydration-mixing exhibit the highest 25th carbonation conversion of 53.44% and a desirable anti-attrition ability (a weight loss of 0.62% after 3000 rotations). The alleviated sorbent sintering as a result of the homogeneously distributed CaTiO3 phase is responsible for the improved CO2 capture performance. Additionally, the strong binding force of the initially formed hydrate contributes to enhancing the anti-attrition ability of the TiO2-decorated CaO-based sorbent pellets prepared via hydration-mixing.

Effect of Empty Fruit Bunch in Calcium Oxide for Cyclic CO2 Capture

AbstractEmpty fruit bunch (EFB) is utilized to increase the CO2 capture capacity and cyclic stability of calcium oxide (CaO) prepared from cockle shells (CS). The cyclic reaction of calcination and carbonation reaction was performed in pure N2 environment and in the presence of CO2 in N2, respectively. The EFB in CS modified the pore structural properties, morphology, and composition of the pristine CaO. Higher EFB loading in CS reduced the CaO composition but improved the CO2 capture capacity and cyclic stability during cyclic CO2 capture.

Cycle design and optimization of pressure swing adsorption cycles for pre-combustion CO2 capture

Novel pressure-swing adsorption (PSA) cycles were developed based on patented TDA AMS-19 (activated carbon) adsorbent for pre-combustion CO2 capture in integrated gasification combined cycle (IGCC) power plants. A variety of cycles comprising of counter-current blowdown, pressure equalization, steam purge and light product pressurization steps were designed and simulated using an in-house one dimensional detailed model. Full process optimization studies were performed for all cycles to evaluate their feasibility for pre-combustion CO2 capture. The CO2 purity and recovery Pareto fronts obtained using the multi-objective optimization were used to assess their ability to simultaneously achieve high CO2 purity (>95%) and recovery (>90%). The cycles that achieved the purity-recovery (95–90%) requirements were subjected to energy-productivity optimizations under the constraints of CO2 purity and recovery. Three cycle designs were ranked in terms of lowest energy consumption at 95% CO2 purities and 90% CO2 recoveries. It was found that a 10-step cycle with three pressure equalization steps achieved a minimum energy consumption of 95.7 kWhe/tonne of CO2 captured at a productivity of 3.3 mol CO2 captured/m3 adsorbent/s.

Low-energy-consumption and environmentally friendly CO2 capture via blending alcohols into amine solution

The conventional regeneration processes for aqueous amine-based sorbents require high regeneration temperature and are very energy intensive. In this work, a low-temperature and energy-saving CO2 capture technology has been successfully developed by using alcohols-amines-water mixtures as sorbents. The addition of certain amounts of alcohols [especially ethanol (EtOH)] to amines can significantly increase the CO2 desorption rates and cyclic CO2 capture capacities in comparison with those of monoethanolamine-water, diethanolamine-water, and methyldiethanolamine-water systems. The sorbent containing 40 wt% EtOH, 20 wt% monoethanolamine (MEA), and 20 wt% H2O can increase cyclic CO2 capture capacity by 6.8 times and a maximum improvement of 236 times in CO2 desorption rate at 75 °C, which makes the use of the low-temperature waste heat in power plants for CO2 capture or self-supported CO2 capture in power plants possible. To the best of authors’ knowledge, this is the first time that Raman and Fourier transform infrared spectroscopy characterizations have been used to confirm that ethanol in EtOH-MEA-H2O can change the reaction pathway by forming C2H5OCO2− instead of HCO3−, which is difficult to decompose. In addition, the experimental results confirm that the new technology can significantly avoid amine degradation – a common challenge of the state-of-the-art CO2 capture technologies. Therefore, the new CO2 capture technology is promising from the perspectives of energy saving and environmental protection.

Fabrication of efficient and stable Li4SiO4-based sorbent pellets via extrusion-spheronization for cyclic CO2 capture

Li4SiO4 is a promising solid sorbent for high-temperature CO2 capture due to the high and stable CO2 adsorption performance. It is required to possess good mechanical properties in practical fluidized-bed systems and pelletization is necessary. However, pelletization generally results in a large decline in the CO2 uptake or a continuous loss-in-capacity of Li4SiO4 sorbents in cyclic reactions. In this work, three kinds of Li4SiO4 powders were synthesized and screened, and spherical pellets were further prepared via an extrusion-spheronization technique using polyethylene as a pore-former to develop porous microstructure. Then sorbent pellets were systematically tested on the CO2 adsorption performance, compression strength and attrition resistance. Results shows that the pellets modifying with 20 wt% polyethylene reach and stabilize a CO2 sorption capacity of 0.31 g CO2/g sorbent in the whole 40 tested cycles under typical conditions, which is even higher than that in powder form. Moreover, the pellets are observed to have an outstanding compression strength (27.5 MPa after calcination) and an excellent attrition resistance (only 1.01 wt% mass loss in 10 h-attrition test), which are both far more better than sorbents reported in the literature. The simultaneous physiochemical performances indicate that the prepared Li4SiO4 sorbent pellets could be suitable for high temperature CO2 capture in fluidized-bed reactors.