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Numerical simulation of CO emission in a sintering pot under flue gas recirculation
No full textA transient two-dimensional sintering model coupling porous medium flow, interphase heat mass transfer and reactions was established through computational fluid dynamics (CFD) method by Comsol Multiphysics 6.0 for a sintering pot under sintering flue gas recirculation (SFGR). The ignition was considered and CO was the carbon combustion intermediate and experienced catalytic oxidation in the ferric oxide bed. The model was verified by sintering pot experimental data of flue gas temperature and components fractions with maximum deviation less than 10 %. The bed temperature, CO emission and solid fuel consumption were focused under different SFGR parameters by the verified model. Ignition was important for the beginning flue gas component fractions, especially when the bed height was less than 700 mm. The effect of SFGR parameters on the maximum bed temperature (MBT) was sequenced: inlet gas velocity > inlet CO fraction > inlet O2 fraction > inlet gas temperature. MBT grew up when each of the four parameters increased. The impact on the CO emission was different: inlet CO fraction > inlet O2 fraction > inlet gas velocity > inlet gas temperature. CO emission declined when each of the parameters increased. The total reaction rate of CO was studied for explanation. The reduction of solid fuel consumption was studied by energy conservation to evaluate the influence of inlet CO, inlet gas temperature and flue gas recirculation fraction. The three factors had positive linear correlation with solid fuel consumption reduction. The reduction maximally reached 16.6 % at flue gas recirculation fraction of 50 %, inlet 2 % CO and 473.15 K temperature, providing theoretical support for SFGR application
A new method of Ionic Fragment Contribution-Gradient Boosting Regressor for predicting the infinite dilution activity coefficient of dichloromethane in ionic liquids
No full textIonic liquids (ILs) have shown huge potential advantages as solvents to absorb and recover dichloromethane (DCM) from waste gasses. The infinite dilution activity coefficient (gamma infinity) of DCM in ILs is an important parameter, which can be used to predict the vapor-liquid equilibrium of DCM-IL systems. In this work, a new model of calculating the gamma infinity of DCM in ILs is established based on ionic fragments contribution (IFC) and gradient boosting regressor (GBR) algorithm. IFC is used to obtain the surface charge density distribution area of ILs (S sigma-profile) that is the input of GBR. GBR is used to learn the mapping relationship between input feature and gamma infinity of DCM in ILs. The database of the gamma infinity of DCM in ILs composed of 29 cations and 22 anions includes 72 experimental data and 421 COSMO calculation data, which was employed to establish the IFC-GBR model and predict the gamma infinity of DCM in ILs. The coefficient of determination (R2) and mean absolute error (MAE) of the IFC-GBR model test set are 0.9703 and 0.0519, respectively. Also, this model has excellent generalization capability of predicting evidenced by high 10-fold cross-validation coefficients of determination in the range 0.9474-0.9481. These results indicate that the proposed model can accurately predict gamma infinity of DCM in ILs, then provide the important data for developing a new process of absorbing and desorbing DCM by IL-based technologies
Construction of a flower-like SnS2/SnO2 junction for efficient photocatalytic CO2 reduction
No full textPhotoreduction of CO2 to value-added chemicals and fuels is an attractive solution to alleviate environ-mental problems and energy crisis at the same time. However, engineering efficient photocatalysts with high activity and product selectivity is still challenging. Herein, we achieved three-dimensional (3D) spa-tial configuration design at micro-scale and heterogeneous interface construction at nano-scale on a SnS2/SnO2 composite, which featured hierarchical flower-like morphology consisted of nanosheets and type-II semiconductor structure. It behaved excellent selectivity and impressive photocatalytic CO2-to-CO performance with a yielding rate of 60.85 lmol g-1h-1, roughly 3 times higher than that of SnS2 and was in the front rank of this kind catalysts under 300 W Xe lamp illumination without using any sen-sitizers or noble metals. The enhanced catalytic capability could be attributed to the elaborately built structure with suitable energetic position that afforded effective separation and migration of photo -generated electron/hole pairs as well as enhanced light caption and absorption. Meanwhile, main reactive intermediates (e.g., CO2- and *COOH) were captured by in-situ Fourier transform infrared spectroscopy (FTIR), suggesting a fluent catalytic pathway on the SnS2/SnO2 platform. This work provides a new scheme to build advanced catalysts based on multiscale design and rational phase assembling.(c) 2022 Elsevier Inc. All rights reserved
Projects of the Innovation Academy for Green Manufacture, Chinese Academy of Sciences, China[IAGM 2020DB04]
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Construction of Co3O4/CeO2 heterostructure nanoflowers facilitates deployment of oxygen defects to enhance the oxygen evolution kinetics
No full textThe bottom-up design strategy can more rationally optimize the composition and structure of the materials to impart excellent oxygen evolution reaction (OER) performance. Heterostructures can modulate electronic behavior through interface construction to optimize materials properties for superior OER performance. In this paper, we created abundant Co3O4/CeO2 phase interfaces to tune the grain size, the electronic con-figuration of cobalt sites, and the content of oxygen defects in Co3O4, which increases the number of active sites, enhances the electronic conductivity of the material, and optimized the adsorption energy for reaction intermediates. Moreover, the assembly of nanograins into nanoflowers with a three-dimensional hier-archical pore structure can provide more effective active sites, abundant pores and channels for mass transport, and discrete cavities for in-depth reactions of intermediates. The construction of Co3O4/CeO2 heterostructure nanoflowers (CoCe HNFs) contributes to the excellent OER performance of the catalyst. (c) 2022 Elsevier B.V. All rights reserved
Interfacial oxygen vacancies at Co3O4-CeO2 heterointerfaces boost the catalytic reduction of NO by CO in the presence of O2
No full textSimultaneously improving both NOx conversion and N2 selectivity in the selective catalytic reduction of NO by CO (CO-SCR) under O2-containing conditions is highly challenging because of the competitive reactions of NOx and CO with O2. Here, we demonstrate that the interfacial oxygen vacancies (IOVs) generated at the Co3O4-CeO2 heterointerfaces by ball-milling-induced strain can remarkably boost both NOx conversion and N2 selectivity in the temperature range of 100-400 degrees C. The Co3O4-CeO2-IOV catalyst achieved approximately 100% NOx con-version and 100% N2 selectivity (200-350 degrees C, 1-5 vol% O2, and 20,000 h-1); even under 10 vol% O2, it still showed good catalytic performance. The spectroscopy analysis and theoretical calculations reveal that compared with O2 activation, IOVs are more favorable for the rate-limiting step of NO adsorption and dissociation. This work provides an effective strategy to create IOVs within metal oxide composite catalysts using ball-milling -induced interfacial strain for improving CO-SCR performance