To address the limitations of isothermal models in accurately predicting heat transfer in thermally thick particles (Bi > 1) and to establish a theoretical basis for optimizing fluidized bed reactors used in carbon emission reduction technologies, this study investigates the heat transfer characteristics of such particles, with particular emphasis on the role of internal particle conduction. Based on the CFD-DEM framework, a one-dimensional heat conduction model for the intra-particle temperature is developed. The model is first validated against single-particle and system-level experiments to ensure its accuracy. Subsequently, the effects of particle thermal conductivity and diameter on temperature distribution and heating process are analyzed. The results indicate that increasing the thermal conductivity reduces the maximum internal temperature difference from 300.99 K to 64.67 K and shortens the heating time from 11.19 s to 7.13 s. Similarly, reducing the particle diameter decreases the internal temperature difference peak from 223.7 K to 94.18 K and reduces the heating time from 11.25 s to 5.76 s. However, it also leads to greater temperature non-uniformity during the initial heating stage. These findings enhance the understanding of heat transfer behavior in thermally thick particles within fluidized bed reactors.

This study investigates the influence of solid volume fraction (Vs = 0.03-0.30) on bubble characteristics across various flow regimes in a three-phase bubble column, comparing the effects for two solid particle sizes (48 mu m and 150 mu m). Bubble size distribution, area distribution, number, shape, and Sauter mean diameter (d32) are analyzed. At the smaller particle size (48 mu m), increasing Vs consistently shifts the bubble size distribution towards smaller diameters across all regimes, indicating a particle stabilizing effect on small bubbles; bubble coalescence under these conditions is primarily driven by increasing gas velocity (Ug). Conversely, at 150 mu m, elevating Vs broadens the bubble size distribution at all tested gas velocities. These contrasting results demonstrate that while more adhering 48 mu m particles stabilize small bubbles, increased concentrations of 150 mu m particles promote bubble coalescence. Furthermore, higher Vs reduces bubble numbers across all flow regimes due to increased flow resistance. For 48 mu m particles, increased Vs also enhances the longitudinal stretching deformation of bubbles. The d32 results quantitatively reflect the observed changes in bubble size distributions. This work provides fundamental data elucidating particle effects on hydrodynamics in gas-liquid-solid bubble columns.

This study presents an experimental investigation on the direct aqueous carbonation of carbide slag with a focus on implementing a liquid-phase recycling strategy. The effects and underlying mechanisms of key operational parameters, including the liquid-phase recycling ratio, the number of recycling cycles, and reactor preparation methods (cleaning methods), are systematically compared and analyzed. The research confirms the technical feasibility of the liquid-phase recycling process. The results demonstrate that carbonation efficiency improves and stabilizes with successive recycling cycles. A higher liquid recycling ratio significantly enhances the overall carbonation efficiency and solid-phase CO2 sequestration, primarily attributed to an increased concentration of 〖HCO〗_3^- ions in the recycled aqueous phase, which promotes CaCO3 precipitation and creates a synergistic cycle that improves reaction kinetics. A critical finding is the substantial impact of reactor preparation. Thorough cleaning of the reactor utilizing acetic acid solution between cycles leads to a stable and significant boost in carbonation efficiency. In contrast, merely rinsing with water, which leaves residual solid deposits, causes an initial efficiency increase followed by a continuous decline in subsequent cycles. This decline is linked to increased mass transfer resistance, reduced effective interfacial area, and impaired reaction kinetics due to particle accumulation and increased slurry viscosity. Consequently, the study recommends liquid-phase recycling operation with complete slurry drainage between experiments to mitigate these negative effects. This work provides fundamental data and theoretical insights into the flow, mass transfer, and reaction characteristics of the process, offering valuable guidance for the development of efficient liquid-phase recycling methods in direct aqueous mineral carbonation.

The aqueous mineral carbonation of Ca(OH)(2) in a bubble column has been studied by employing the experimental and numerical approaches. The effect of the gas velocity (0.02 m/s - 0.205 m/s) on the bubbly reactive flow has been investigated. The average gas holdup, local gas holdup, flow images, pH and electrical conductivity and the carbonation efficiencies are obtained by experiments. Eulerian-Eulerian-Eulerian approach is used to simulate the reactive flow. It's found that this numerical model has a good prediction accuracy. The interactions of the flow behaviors, CO2 mass transfer and reaction are discussed. The gas holdup predicted reduces notedly when the mass transfer is considered at 0.082 m/s-0.123 m/s. The mass transfer rate is mainly influenced by the CO2 concentration gradient between gas and liquid phase, and the kLa L a mainly influenced by the mass transfer model chosen. The hydrodynamics and mass transfer are interacted and combined to impact the reaction results.

Efficient Ni-CaO dual function materials (DFMs) pellets show potential in integrated CO2 capture with reversed water gas shift reaction (ICCU-RWGS) for syngas production. However, the presence of O2 in industrial flue gas might affect their ICCU-RWGS performance. In this work, Ni-CaO DFMs pellets were synthesized via the extrusion-spherization method, and the ICCU-RWGS performance of the pellets in O2-containing stream was investigated. The surface basicity of the pellets decreased, and CO2 capture capacity decreased from 10.32 to 8.40 and 6.53 mmol CO2/g when the pellets were exposed to 2 % O2 and 15 % O2, respectively. The presence of 2 %O2 in flue gas resulted in the decay in catalytic activity, and CO yield declined from 6.0 to 5.08 mmol CO/g. Interestingly, the oxidative deactivation of Ni in O2 and the decrease of catalytic activity had avoided the unexpected release of CO in the CO2 capture stage, making the CO2 separation process more efficient.

The hydrodynamics of three-phase reactive flow, CO2 gas-liquid mass transfer and reaction process during the aqueous mineral carbonation of carbide slag in a bubble column are studied. The impact of gas-liquid mass transfer on the carbonation reaction results are discussed. The amounts of CO2 captured in the solid phase or the liquid phase can be characterized by electrical conductivity and outlet CO2 concentration curves. It's found that the three-phase reactive flow is in homogeneous flow regime at 0.07 m/s. The volumetric mass transfer coefficient kLa reduces as the L/S ratio increases due to the reduction of the interfacial area and the increase of the gas diffusion resistant. The kLa increases when the CO2 concentration or the gas velocity enhances. The greater concentration gradient and larger gas velocity are better for the fast mass transfer rate. However, the longer reaction time maintaining at pH of around 12.0-9.0 are favorable for achieving the higher capture capacity and carbonation efficiency. The amounts of CO2 absorbed in liquid phase become larger with the increase of L/S ratio. The effect of Ug on the reaction results is little at low L/S ratio (10 mL/g) and 20 % of CO2 concentration. The maximum capture capacity obtained is 303.9 g CO2/kg carbide slag in this study. This study aims to clarify the mechanism of CO2-water mass transfer and the amounts of CO2 captured as precipitant in a bubble column carbonation reactor.

Electrochemical CO2 reduction (ECR) syngas (CO/H2) using renewable electricity is considered as a promising approach to realizing carbon neutrality. However, balancing the activities of the CO2 reduction reaction (CO2RR) and the hydrogen evolution reaction (HER) to achieve adjustable CO/H2 ratios remains challenging. In this study, Cu-Zn bimetallic catalysts were synthesized via electrodeposition for ECR to syngas, and the CO/H2 ratio was tuned over a broad range of 0.2-2.1 by adjusting the deposition time and applied potential. The effect of deposition time on Zn loading and ECR performance was investigated. As deposition time increased, the density and uniform dispersion of Zn sites were enhanced, which improved CO selectivity and increased the CO/H2 ratio and syngas production rate. Density functional theory (DFT) calculations revealed that the alloying effect between Cu and Zn sites endowed the catalyst with moderate energy barriers for *COOH formation and *CO desorption in CO2RR, and moderate desorption intensity of *H for HER. Increasing Zn loading raised the energy barrier for *H formation but facilitated *CO desorption, thereby enhancing CO production. CO2 conversion to *COOH was then identified as the rate-determining step in CO2RR. Excessive prolongation of the deposition time negatively impacted CO2RR performance, resulting in decreased CO/H2 ratio and syngas production rate due to overloading and uneven dispersion of Zn sites, as well as increased charge transfer resistance. The Cu-Zn-675 catalyst, with an optimal deposition time of 675 s, exhibited the highest activity and selectivity for syngas production, achieving a high syngas Faradaic efficiency (FE) of approximately 90 % and a tunable CO/H2 ratio of 0.6-2.1 over a wide potential range of -0.61 to -1.21 V versus reversible hydrogen electrode (RHE). Cu-Zn-675 also demonstrated excellent long-term operational stability, maintaining a stable CO/H2 ratio and syngas production rate of 2.0 and 104.2 mu mol/h/cm2, respectively, for up to 7.5 h at a constant potential of -0.81 V vs. RHE. This work presents a promising strategy for developing robust catalysts for ECR to syngas with tunable CO/ H2 ratios.

Integrated CO 2 capture and utilization by reverse water gas shift (ICCU-RWGS) reaction for syngas production for C1 chemical industry has gained increasing attention. Designing highly active bifunctional materials that enables CO 2 adsorption and in -situ conversion is essential. In this work, Ni-Na 2 ZrO 3 bifunctional materials are prepared by different synthetic methods for ICCU-RWGS. N 2 physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), CO 2 temperature -programmed desorption (CO 2 -TPD) and H 2 temperature -programmed reduction (H 2 -TPR) analysis reveals that Ni-Na 2 ZrO 3 -CP prepared by the co -precipitation (CP) method shows small Ni crystalline size, moderate surface basicity, and excellent reducibility. ICCU-RWGS performance is investigated under isothermal conditions of 650 degrees C, 10 %CO 2 and 35 %H 2 . The results indicate that Ni-Na 2 ZrO 3 - CP demonstrates excellent performance in ICCU-RWGS, with a notable CO 2 capture capacity of 3.76 mmol CO 2 /g and a CO production rate of 3.10 mmol CO/g. Additionally, it exhibits relatively good operational stability. Detailed reaction paths of the ICCU-RWGS procedure for the Ni-Na 2 ZrO 3 bifunctional materials are proposed. The findings will shed new perspectives on the design of synthetic bifunctional catalysts for ICCU-RWGS.

Electrochemical CO2 reduction (ECR) to value-added products is regarded as a sustainable strategy to mitigate global warming and energy crisis, and designing highly efficient and robust catalysts is essential. In this work, transition metal sulfides (TMS)-decorated CuS microflower-like structures were prepared via the one-pot hydrothermal synthesis method for ECR to CO, and the influence of TMS doping on ECR performance was demonstrated. Characterization of the catalysts was performed using XRD, FESEM-EDS, N2 physisorption, and XPS, revealing the successful loading of TMS, the formation of microflower-like architectures and the generation of sulfur vacancies. Electrochemical tests demonstrated that doping ZnS, Bi2S3, CdS and MoS2 improved the intrinsic CO2 reduction activity of the CuS catalyst. Particularly, the MoS2-CuS composite catalyst with imperfect petal-like structure showed uniform distribution of edge Mo sites, which worked synergistically with the formed grain boundaries (GBs) and undercoordinated S vacancy sites in promoting CO2 activation, stabilizing *COOH adsorption, facilitating *CO desorption, and lowering the energy barrier of the potential-limiting step for improved CO selectivity. The MoS2-CuS catalyst achieved a maximum CO selectivity of 83.2% at –0.6 V versus the reversible hydrogen electrode (RHE) and a high CO cathodic energetic efficiency of 100%. At this potential, the catalyst maintained stable catalytic activity and CO selectivity during a 333-min electrolysis process. The findings will offer a promising avenue for the development of efficient and stable catalysts for CO production from ECR.

The introduction of solar thermal energy and the thermal energy storage are effective methods for reducing the fossil fuel consumption and improving the operation performance of combine cooling, heating and power (CCHP) system. In this study, a CCHP system integrated with solar thermal energy and thermal energy storage is proposed. The thermal energy storage device, which plays the role of energy hub, absorbs the solar thermal energy form the parabolic trough collector and excess thermal energy in the flue gas and then releases the thermal energy when necessary. Transient model of the system is established and the corresponding performance of the proposed system in the typical days are compared with those of the separated system and the conventional CCHP systems. The primary energy saving rate of the proposed system in the typical days of summer, winter and transition seasons are found to be at least 11 percent higher than the other CCHP systems. The capacity of the system is then adjusted for the best economy and corresponding thermal energy storage device capacity is found. Considering the peak-flat-valley electricity price, the operation strategy is then optimized and the equivalent levelized cost of electricity is reduced by 14.3%. This paper provides a viable option for improving the CCHP system performance and economy in solar-abundant regions.

The accelerated carbonation technology utilizing the alkaline minerals or alkaline wastes incurs high operation and investment costs, low conversion efficiency and high energy consumption. Due to the strong alkalinity of the carbide slag, good feedstock availability and great performance of the bubble column reactor, the direct aqueous mineral carbonation of the carbide slag in a bubble column at ambient conditions is evaluated. The impact mechanism of the liquid to solid ratio (5 mL/g - 50 mL/g) and gas velocity (0.0041 m/s - 0.205 m/s) on the reactions are investigated. The flow patterns are identified by EMD energy entropy, and carbonation efficiencies at different flow regimes are compared and illustrated. It is found that this route has a high carbonation efficiency and short reaction time. The maximum carbonation efficiency is 100% and the capture capacity is 214.05 g CO2 / kg carbide slag. The discrete bubble regime (DBR) and bubble coalescence regime (BCR) are observed, and the increase of the L/S ratio can promote the bubble coalescence. The hydrodynamics can influence the processes of the CO2 mass transfer from gas to liquid phase, Ca(OH)2 dissolution, reactant diffusion, collision and ionic reactions. At small L/S ratio, the greater carbonation efficiency is achieved in discrete bubble regime attributing to the longer gas residence time, larger gas-liquid interfacial area and better CO2 mass transfer than that in BCR. At large L/S ratio, the greater carbonation efficiencies are achieved both in DBR and BCR. It has good CO2 mass transfer in DBR and has the strong liquid turbulence intensity in BCR which is good for the reactant diffusion and collision. The enhancement factor increases when enhancing the L/S ratio in DBR. The 30 mL/g and the gas velocity operated in the discrete bubble regime are recommended considering the better three-phase contact, good carbonation conversion and low energy consumption.

搭建了鼓泡床碳酸化反应器,研究常温常压下电石渣直接液相碳酸化矿化封存CO2的能力,揭示了重要操作参数表观气速、液固比和CO2浓度对电石渣矿化封存CO2能力和碳酸化效率的影响规律.同时构建响应面模型,分析各参数对电石渣碳酸化效率的影响强度,优化获得最大碳酸化效率及相应操作工况.结果表明,增加气速有利于钙离子溶解和CO2吸收,但反应器中过高气速易导致气相通道效应,不利于气液充分接触.当液固比降低,溶液中钙离子浓度提高,更有利于碳酸化反应,但液固比过低会影响固液间传质.适当增加CO2浓度有利于提高碳酸化效率,但CO2浓度增至到一定值后,对碳酸化效率影响降低.响应面建模分析发现,各因素对碳酸化效率影响顺序为:液固比>CO2浓度>表观气速.优化结果发现碳酸化效率最高为93.58％,工况为表观气速0.07m/s,液固比为8.26mL/g和CO2体积分数为20.91％.研究可知,鼓泡床中常温常压下电石渣直接液相加速碳酸化反应,具有较大的CO2固定量和高的碳酸化效率,实验结果为电石渣加速矿化封存CO2技术的发展提供了基础数据.

The area for the solar energy utilization in the building is limited. With this in mind, a compact solar collector which integrated the prism and semi-parabolic trough mirror is proposed for the efficiently solar energy collecting in limited space. The prism is rotated to track the sun and keep the emitted sunlight perpendicular to the aperture of semi-parabolic trough mirror. The sunlight from the prism is then reflected and concentrated by semi-parabolic trough mirror and finally absorbed by the receiver tube. Based on the rigorous theoretical model, the tracking strategy is proposed and verified, which indicate that the sun could be tracked exactly and the tracking strategy is effective in the condition of non-parallel and multi-spectrum solar radiation. The geometric concentrating ratio, geometric parameters and the row arrangement of the proposed solar collector are all optimized. The results show that the annual solar-to-thermal efficiency evaluated by land area of the proposed solar collector is up to 41.1%, which is 6.7 and 17.6 percent points higher than those of parabolic trough and flat plate collectors, respectively. With the performance advantage in the solar collecting within limited space, the proposed solar collector could provide a promising approach for the solar energy utilization in the building.(c) 2022 Elsevier Ltd. All rights reserved.

Abstract The direct aqueous mineral carbonation of carbide slag was investigated. The flow characteristics of carbide slag-CO2-water reaction system in a bubble column were studied, which included the bubble Sauter mean diameter, gas holdup, bubble residence time, and the gas-liquid interfacial area. Bubble flow behaviors in the reactor were characterized by analyzing the bed pressure signals. The effects of the gas velocity (U g ) and liquid to solid ratio (L/S ratio) were discussed and analyzed. The results showed that the larger bubbles were easy to form at the larger L/S ratio, which indicated that the bubble coalescence was promoted. The gas holdup was larger when increasing U g or reducing the L/S ratio. The better gas-liquid interfacial areas were found in a wide range of L/S ratio at U g = 0.082 m/s. The optimum conditions were found at U g = 0.082 m/s and L/S ratio = 15–30 mL/g for the better gas-liquid interfacial area and the higher carbide slag conversion. The work provided the theoretical basis for the direct aqueous carbonation of the carbide slag and the operation condition optimization.

Photocatalytic oxidation has been considered as a potential method for elimination of organic contaminants with low energy consumption. Photodegradation performance is subject to some factors: bandgap, band-edge positions and carrier separation efficiency. Z-scheme heterojunction system can improve photocatalytic performance through optimizing these factors. Thus, a Z-scheme α-Fe2O3/g-C3N4 hollow microsphere was obtained via controlled crosslinking and hydrolysis process (uniform dispersion of two components: through crosslinking; hollow structure: from self-sacrifice of glucose). Numerous constructed pores are beneficial for tetracycline (TC) to adsorb on photocatalysts (7.9 mg/L), which further accelerates TC degradation process. TC degradation rate increased to 67% over α-Fe2O3/g-C3N4-4 (g-C3N4: 48%, α-Fe2O3: 44%) after 2 h irradiation, which results from the quick capture and separation of photogenerated electron–hole pairs and the oxidation and reduction abilities of photocatalysts. This work presents an insight into promoting degradation efficiency of antibiotics and simultaneously reducing photocatalyst cost.

The LaFeO3-based heterostructure photocatalyst and photo-Fenton process are combined to effectively treat ceftriaxone sodium (CRS) contaminant under visible light.

Ca-rich solid waste, carbide slag, was adopted to prepare the CaO-based sorbent for CO2 uptake at elevated temperature. To alleviate the elutriation issue of CaO-based sorbent from the calcium looping system, the granulation of carbide slag was conducted via an extrusion-spheronization method. Calcium aluminate cement possessing excellent refractory property was selected as the binder. A range of cement-bound carbide slag pellets were prepared with the active CaO content varying from 25 to 70 wt %. The incorporation of calcium aluminate cement significantly decreases the CO2 capture capacities of the carbide slag pellets due to the irreversible consumption of active CaO by the silicates or aluminates within the cement. However, the average compression strengths of the fresh (3.29-9.82 MPa) and calcined (0.47-2.46 MPa) cement-bound carbide slag pellets gradually increase with the increase of cement addition. Additionally, the addition of rice husk can improve the CO2 capture performance of the cement-bound carbide slag pellets during the fast CO2 capture stage because of the generation of in stiu pores and cavities within the sorbent pellets. Although the cyclic CO2 capture performance of the cement-bound carbide slag pellets degrades under oxy-fuel calcination condition, to some extent, the low-cost and easily scaled-up preparation route may offsets the increased CO2 avoid cost because of the loss-in-capacity.