Volume 8, Issue 2 -

This communication deals with the Abductive Network modeling approach to investigate the phase holdup distributions of a liquid–solid circulating fluidized bed (LSCFB) system. The Abductive Network model is developed/trained using experimental data collected from a pilot scale LSCFB reactor involving 500-μm size glass beads and water as solid and liquid phases, respectively. The trained Abductive Network model successfully predicted experimental phase holdups of the LSCFB riser under different operating parameters. It is observed that the model predicted cross-sectional average of solids holdups in the axial directions and radial flow structure are well agreement with the experimental values. The statistical performance indicators including the mean absolute error (~4.67%) and the correlation coefficient (0.992) also show favorable indications of the suitability of Abductive Network modeling approach in predicting the solids holdup of the LSCFB system.

This article describes the formulation, solution and analysis of two single-objective optimization and one multi-objective optimization (MOO) problems on trickle-bed reactors (TBRs) involving hydrodesulfurization (HDS) and hydrodearomatization (HDA). The model used by Chowdhury et al. (AIChE J 2002;48:26) for TBR involving HDS and HDA is used in this study, to solve these optimization problems. The correctness of algorithm and the numerical procedure used in this study to solve the model equations are validated with the results of Chowdhury et al. (AIChE J 2002;48:26), before the model is used for optimization. Objective functions chosen in our optimization studies are minimization of sulfur concentration and maximization of total conversion of aromatics at the exit of TBR. Decision variables considered are reactor temperature, reactor pressure and liquid hourly space velocity (LHSV). Two single-objective optimization and one MOO problems are formulated and solved using simple genetic algorithm (SGA) and NSGA-II, respectively, to obtain the optimal values of reactor operating conditions. Pareto set for the MOO problem is generated which show that conflicting nature of the objective functions. Specifically, we have shown that the simultaneous minimization of exit sulfur and maximization of aromatics removal conflict each other in hydrotreating.

In this study, infrared drying characteristic of mushroom slices was investigated in the temperature range of 50–90°C. The drying data were fitted to five thin-layer drying models. The performance of these models was compared using the determination of coefficient ( R 2 ), reduced chi-square ( χ 2 ), and root mean square error between the observed and predicted moisture ratios. The values of the diffusivity coefficients at each temperature were obtained using Fick’s second law of diffusion. The drying processes were completed within 60–168 min at different temperatures. Experimental drying curves showed only a falling drying rate period. The results show that the logarithmic model is the most appropriate model for infrared drying behavior of thin-layer mushroom slices. A third-order polynomial relationship was found to correlate the effective moisture diffusivity with moisture content. The average effective moisture diffusivity increased with increasing temperature and decrease in moisture content of mushroom slices and varied from 8.039 × 10 −10 to 20.618 × 10 −10 m 2 /s. Arrhenius relation with an activation energy value of 21.85 kJ/mol expressed the effect of temperature on the average diffusivity. The minimum and the maximum energy requirements for drying of mushroom slices were also determined as 2.87 kW h/kg water and 5.36 kW h/kg water for 90 and 50°C, respectively.

Typical current operation of lateral-blown Peirce-Smith converters (PSCs) has the common phenomenon of splashing and slopping due to air injection. The splashing and wave motion in these converters cause metal losses and potential production lost time due to intermittent cleaning of the converter mouth and thus reduced process throughput. Understanding of the effect of combined top and lateral blowing could possibly lead to alternative technology advancement for increased process efficiency. In this study, computational fluid dynamics (CFD) simulations of conventional common practice (lateral blowing) and combined (top and lateral blowing) in a PSC were carried out, and results of flow variables (bath velocity, turbulence kinetic energy, etc.) were compared. The two-dimensional (2-D) and three-dimensional (3-D) simulations of the three-phase system (air–matte–slag) were executed utilizing a commercial CFD numerical software code, ANSYS FLUENT 14.0. These simulations were performed employing the volume of fluid and realizable turbulence models to account for multiphase and turbulent nature of the flow, respectively. Upon completion of the simulations, the results of the models were analysed and compared by means of density contour plots, velocity vector plots, turbulent kinetic energy vector plots, average turbulent kinetic energy, turbulent intensity contour plots and average matte bulk velocity. It was found that both blowing configuration and slag layer thickness have significant effects on mixing propagation, wave formation and splashing in the PSC as the results showed wave formation and splashing significantly being reduced by employing combined top- and lateral-blowing configurations.