Influence of additives on CaCO3 precursors and multicycle CO2 capture performance of CaO sorbents

Yue, Wenfei; Fan, Chengpeng; Song, Wenli; Li, Songgeng

doi:10.1016/j.jece.2022.107440

Cited by 14 publications

(4 citation statements)

References 32 publications

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“…In contrast, our results indicate that nanoparticle calcination can involve planar reaction front motion following heterogenous CaO nucleation at CaCO 3 grain boundaries, without the formation of a metastable CaO polymorph intermediate (Figure 5b). At 500 °C, within a CaCO 3 particle, calcination proceeds first by increased particle surface roughness, attributed to calcination temperatures being in the range of the CaCO 3 Tammann temperature (533 °C) [34] which activates mass transport in CaCO 3 and heterogeneous nucleation of rectangular CaO crystals at CaCO 3 grain boundaries (Figure 5b i-ii). This is consistent with work showing that decreased calcite crystallinity increases the number of reactive sites near crystal defects, result-ing in faster calcination.…”

Section: Discussionmentioning

confidence: 99%

“…[33] Some argue that sintering occurs when particles are CaCO 3 , because typical calcination temperatures (≈900 °C) exceed the CaCO 3 sintering onset ("Tammann") temperature of 533 °C. [34] Others claim that sintering occurs after CaO formation-even though the CaO Tammann temperature (1170-1313 °C [6,35] ) exceeds typical calcination temperaturesbecause a metastable dilated CaO intermediate phase sinters due to exothermic relaxation to the thermodynamically stable unstrained CaO. However, the existence and role of a metastable CaO intermediate remains controversial after ≈50 years, [36][37][38][39][40][41] with researchers still debating if it is a key short-lived reaction intermediate responsible for sorbent surface area loss before transformation to stable CaO.…”

Section: Introductionmentioning

confidence: 99%

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Precision Calcination Mechanism of CaCO₃ to High‐Porosity Nanoscale CaO CO₂ Sorbent Revealed by Direct In Situ Observations

Martinez,

Wardini,

Zheng

et al. 2024

Adv Materials Inter

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Deploying energy storage and carbon capture at scale is hindered by the substantial endothermic penalty of decomposing CaCO3 to CaO and CO2, and the rapid loss of CO2 absorption capacity by CaO sorbent particles due to sintering at the high requisite decomposition temperatures. The decomposition reaction mechanism underlying sorbent deactivation remains unclear at the atomic level and nanoscale due to past reliance on postmortem characterization methods with insufficient spatial and temporal resolution. Thus, elucidating the important CaCO3 decomposition reaction pathway requires direct observation by time‐resolved (sub‐)nanoscale methods. Here, chemical and structural dynamics during the decomposition of CaCO3 nanoparticles to nanoporous CaO particles comprising high‐surface‐area CaO nanocrystallites are examined. Comparing in situ transmission electron microscopy (TEM) and synchrotron X‐ray diffraction experiments gives key insights into the dynamics of nanoparticle calcination, involving anisotropic CaCO3 thermal distortion before conversion to thermally dilated energetically stable CaO crystallites. Time‐resolved TEM uncovered a novel CaO formation mechanism involving heterogeneous nucleation at extended CaCO3 defects followed by sweeping reaction front motion across the initial CaCO3 particle. These observations clarify longstanding, yet incomplete, reaction mechanisms and kinetic models lacking accurate information about (sub‐)nanoscale dynamics, while also demonstrating calcination of CaCO3 without sintering through rapid heating and precise temperature control.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Precision Calcination Mechanism of CaCO₃ to High‐Porosity Nanoscale CaO CO₂ Sorbent Revealed by Direct In Situ Observations

Martinez,

Wardini,

Zheng

et al. 2024

Adv Materials Inter

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“…As a typical gas–solid uncatalyzed reaction process, the capture of CO 2 from flue gases using calcium-based solid sorbents takes place in a packed-bed reactor (carbonator) with nonuniform pore size distributions and interconnectivity. This calcium looping process has been proposed as the most likely technology to be used for CO 2 capture from high-temperature flue gas in industry. , Due to the complex structure of the packing sorbents and the simultaneously occurring gas–solid reaction and mass transport at the pore scale, the characteristics of the coupled gas flow and gas–solid reaction related to the packing structure within the carbonator are difficult to fully investigate by experimental methods. Meanwhile, there are few reports on multiscale coupling models that can achieve cross-scale coupling among micro uncatalyzed reaction kinetics, mesoscale packing structures, and macro flow characteristics.…”

Section: Introductionmentioning

confidence: 99%

Cross-Scale Transfer and Reaction Coupling during CO₂ Capture: A Novel DEM-PNM-Based Pore-to-Reactor-Scale Model

Li,

Shen,

Wang

et al. 2024

Ind. Eng. Chem. Res.

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The mesoscale packing structure and its coupling with the gas flow and heterogeneous reaction kinetics are key for CO2 capture using CaO-based sorbents. A series of packing structures were constructed based on the discrete-element method (DEM), and the accuracy was verified by electronic computer X-ray tomography (CT). It was found that the random particle filling structure based on the DEM can accurately reflect the coordination number and connectivity between pores. Further, a two-dimensional pore network model (PNM) including the effects of packing structure evolution and diffusion–reaction kinetics was developed to study the multiscale coupling among gas flow, energy transport, and carbonation reactions in packed-bed reactors. The calculated results were validated by comparison with experimental data from thermogravimetric analyzer (TGA) tests during the CO2 capture process. The short-circuit flow of the reactive gas caused by the inhomogeneous packing structure of the binary composite packing bed was not linearly correlated with the mass percentage of the binary particles. The differences in the CO2 capture efficiency and sorbent utilization induced by the packing structure characteristics were demonstrated numerically to decrease gradually with the Peclet number at an inlet velocity of 0.8 m/s. Moreover, a dimensionless Thiele modulus was introduced to assess the effect of internal diffusion. This model and the obtained results can be used for the optimization and design of packed-bed reactors with gas–solid uncatalyzed reactions.

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“…In the split CaL process, the CaO obtained by the calcination of quicklime into the calcination reactor is used as an adsorbent. The CaO adsorbent loses activity after several reactions [16,17]. Therefore, the CaO in the calcination reactor needs to be replaced in time, and it can be used as raw cement material to participate in the calcination process of cement clinker.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of CO2 Extraction from the Cement Pre-Calciner Kiln System

Wang

et al. 2023

Processes

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The cement industry is one of the primary sources producing anthropogenic CO2 emissions. The significant increase in the demand for cement in years has significantly contributed to the increase in carbon emissions. Among numerous CO2 treatment technologies, calcium looping (CaL) is a practical approach to mitigating CO2 emissions. This paper used calcium looping (CaL) to capture CO2 from flue gas in a cement pre-calciner kiln system. The raw material exiting the lowest stage of the preheater is used as a calcium-based adsorbent, and the carbonation reactor is built between the tertiary and secondary preheaters, using the high-temperature flue gas exiting the tertiary preheater to provide heat for the reaction. The CFD (Computational Fluid Dynamics) simulation technology was used to evaluate the rationality of the carbonation reactor and the key factors affecting the carbon removal efficiency of the carbonation reactor. The results indicate that the velocity and pressure fields of the carbonation reactor conform to the general operating rules and are reasonable. The optimal operating speed of particles in the carbonation reactor is 15 m/s, with a separation efficiency of particles of 92.5%, ensuring the smooth discharge of reaction products. The factor analysis of the carbonation reactor shows that when the temperature is 911 K, the mass flow rate of CaO is 2.07 kg/s, and the volume fraction of CO2 is 0.28, the carbonation reaction reaches a chemical equilibrium state, and the carbon removal efficiency is 90%. It should be noted that this carbon removal efficiency is the optimal carbon removal efficiency based on a combination of economic factors. In addition, the influencing factors show a precise sequence: CO2 volume fraction > CaO addition amount > temperature. Finally, we investigated the impact of the addition of the carbonation reactor on the preheater system. The results show that adding the carbonation reactor causes an increase in the flue gas velocity at the outlet of the preheater and a decrease in pressure, reducing the separation efficiency. Although the separation efficiency decreases slightly, the impact on the pre-calciner system is minimal.

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Influence of additives on CaCO3 precursors and multicycle CO2 capture performance of CaO sorbents

Cited by 14 publications

References 32 publications

Precision Calcination Mechanism of CaCO₃ to High‐Porosity Nanoscale CaO CO₂ Sorbent Revealed by Direct In Situ Observations

Precision Calcination Mechanism of CaCO₃ to High‐Porosity Nanoscale CaO CO₂ Sorbent Revealed by Direct In Situ Observations

Cross-Scale Transfer and Reaction Coupling during CO₂ Capture: A Novel DEM-PNM-Based Pore-to-Reactor-Scale Model

Numerical Simulation of CO2 Extraction from the Cement Pre-Calciner Kiln System

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Influence of additives on CaCO3 precursors and multicycle CO2 capture performance of CaO sorbents

Cited by 14 publications

References 32 publications

Precision Calcination Mechanism of CaCO3 to High‐Porosity Nanoscale CaO CO2 Sorbent Revealed by Direct In Situ Observations

Precision Calcination Mechanism of CaCO3 to High‐Porosity Nanoscale CaO CO2 Sorbent Revealed by Direct In Situ Observations

Cross-Scale Transfer and Reaction Coupling during CO2 Capture: A Novel DEM-PNM-Based Pore-to-Reactor-Scale Model

Numerical Simulation of CO2 Extraction from the Cement Pre-Calciner Kiln System

Contact Info

Product

Resources

About

Precision Calcination Mechanism of CaCO₃ to High‐Porosity Nanoscale CaO CO₂ Sorbent Revealed by Direct In Situ Observations

Precision Calcination Mechanism of CaCO₃ to High‐Porosity Nanoscale CaO CO₂ Sorbent Revealed by Direct In Situ Observations

Cross-Scale Transfer and Reaction Coupling during CO₂ Capture: A Novel DEM-PNM-Based Pore-to-Reactor-Scale Model