numerical modeling

The impact of bed loading on minimum spouting velocity (ums) of polydispersed TiO2 particles was studied in a conical fluidized bed. The experiments were performed at different bed loadings according to Gaussian and narrow-cut particle size distribution (PSD). The bed consisted of simple-agglomerates in size range of 30-90 µm belonging to Geldarts’ group A classification. The effect of PSD and interparticle force (IPF) on the predicted ums and hysteresis in the pressure profiles were studied through a combination of computational fluid dynamics and discrete element method (CFD-DEM). The experimental data showed that the choice of bed with Gaussian PSD-type led to more accurately predicting ums than the narrow-cut particle PSD. The impact of IPF on the expected ums became more critical than the PSD type because of an increase in bed loadings. The lowest deviations the results were obtained in the low bed loadings, which is confirmed the accuracy of simulation results. The simultaneous effects of PSD-type and IPF led to a change in the fluidization behavior of the bed. The bed with narrow-cut PSD has a hydrodynamic behavior similar to spouting and slugging regimes, while the fluidization quality of the bed improves by fine particles.

In this study, a three-dimensional model was examined for the evaluation of CO2 diffusivity in pure water and silicon oxide, aluminum oxide and titanium oxide nanofluids with the concentrations of 0.05, 0.1, and 0.2 wt%, respectively. Different parameters such as temperature and the nanoparticles weight percentage on CO2 diffusivity in a diffusivity cell were studied in COMSOL software. Next, CO2 diffusivity was compared with the experimental results. The modeling results showed that water was saturated with gas at 36,000 seconds, and the highest amount of absorbed gas happened at 0.32 m. The CFD results were then validated with the experimental data. Furthermore, temperature was found to have a significant effect on the diffusivity, and it improved by increasing nanofluid concentration until the critical value of 0.1 wt% in all conditions. Moreover, TiO2 NF was introduced as an appropriate nanofluid for the phenomenon of mass diffusivity.

The adsorption characteristics of Basic Red 46 (BR46) were evaluated onto calcium oxide nanoparticles synthesized in two different procedure by combustion method. The operational parameters was checked out to achieve the optimum condition. The X-ray diffraction spectrum, FTIR and scanning electron micrograph of samples was obtained. Adsorption isotherms were determined by BET, Redlich–Peterson, Langmuir, Tempkin, Freundlich, and Dubinin–Radushkevich isotherms, and the results represented Langmuir and Tempkin isotherms as the best fitted one for the adsorption of dye on C1 and C2 (CaO samples), respectively. The adsorption kinetics was studied, and the rate parameters were evaluated at various dye concentrations (10-40 mg L-1) and pH values (3-9). The results conform to the pseudo-second-order kinetics for both samples. Thermodynamic analysis indicates the physical adsorption and endothermic reaction for the adsorption process. Moreover, to model the adsorption process, a computational fluid dynamic model has been performed applying the Matlab CFD code to predict the elimination of BR46 from the aqueous solution by C1 and C2 samples.