Band 18, Heft 3 -

The profitability margin of biodiesel production hampering due to surplus amount of glycerol with the low market price. Thus, developing an alternative route highly demanded for the conversion of glycerol into value-added chemicals. In the present manuscript, green synthesis route was explored by utilizing rice husk derived catalyst. The catalytic properties of the prepared catalyst were investigated by using various characterization techniques. The basic strength of the catalyst was influenced by varying the calcination temperature (200 °C to 500 °C) as well as active metal (cerium) loading (5 wt. % to 20 wt. %). The present investigation revealed that 10 wt. % Ce on Na 2 SiO 3 catalyst calcined at 400 °C exhibited the moderate basic sites of 13.89 mmol/g, which showed potential catalytic activity for the transesterification of glycerol to glycerol carbonate under optimum condition: 92 % glycerol carbonate yield and 98 % glycerol conversion. The catalyst stability study revealed that the catalyst could be reused up to four consecutive cycles without an appreciable drop in catalytic activity. The kinetics of the reaction was also studied, and the activation energy was calculated as 23.80 kJ/mol.

Stirred tanks are commonly used in chemical and allied industries for reaction and separation. In order to improve the mixing performance, large scale reactors are often equipped with multiple impellers. In the case of gas-liquid systems, the gas hold-up, mass transfer coefficient, and interfacial area strongly depend on the size and type of impellers, clearance between impellers and superficial gas velocity. In the present work, the effect of the impeller speed, superficial gas velocity, and top impeller position has been investigated on gas hold-up, interfacial area, and mass transfer coefficient. Computational fluid dynamics have been carried out for the multiphase multi-impeller system and the model predictions have been compared with the experimental data.

Many of oil reservoirs have dealt with operational problems due to probability of asphaltene deposition as a consequence of asphaltene precipitation during natural production and gas injection into the reservoir. So the prediction of asphaltene precipitation is very important and many equations of state (such as Ping Robinson (PR) and Soave–Redlich–Kwong (SRK)) are used for this reason. These common equations are suitable for non-polar components and a modification is necessary to use them for prediction of asphaltene precipitation because of the polar nature of asphaltene compounds. In this study, the SRK equation of state was modified by deriving a new equation for calculating b-parameter (co-volume parameter); and this modified SRK equation of state was used to model asphaltene precipitation. Finally asphaltene precipitation during natural depletion and first stage gas injection process (in different concentrations), was monitored at reservoir temperature and various pressures. The experimental results show a good match with the modified SRK equation of state.

The three-dimensional (3-D) comprehensive mathematical model was developed to simulate the coal gasification process in an entrained flow gasifier with a swirl burner. The models employed or developed includes the coal devolatilization model, the char combustion and gasification model, the gas homogeneous reaction model, the random-trajectory model, gas turbulence model, and the P-1 radiation model. The solution of models was executed based on the computational fluid dynamics (CFD). By qualitatively comparing the results at different swirl number, the significant influences of swirl on characteristics of coal gasification such as flow distributions, gas temperature and product composition including hydrogen (H 2 ), carbon monoxide (CO), etc., and on the performance of coal gasification such as averaged exit product composition, carbon conversion rate and cold gas efficiency, were in detail discussed. Especially, a proper swirl number (S ≤ 0.65) in favor of gasification was found for the investigated gasifier in this paper.

In this paper, we designed tree-like branch structures with two levels according to generalized Murray’s law, and set them as obstacles in microchannels. The influence of the mixing performance of the micromixer was studied by changing the geometry sizes of obstacles, the branch angles and the distances between obstacles. The mixing performance of micromixer was analyzed from three aspects, including mixing efficiency, flow behavior, and pressure drop.We designed three different obstacles A, B, and C, the micromixer with obstacle C has the highest mixing efficiency. For the distances of obstacles, the micromixer with smaller distance has the higher mixing efficiency. The micromixer with branch angle of 75° has the highest mixing efficiency in the range of Reynolds number (Re) 0.1 to 150.

In this paper, we study the role of inlet gas temperature and jet to bed cross-section ratio on hydrodynamics and circulation patterns of particles in a spout-fluid bed. The system is modeled using CFD-TFM approach based on Eulerian-Eulerian method. Simulation results are validated by experimental data measured by (Link 2008. “PEPT and Discrete Particle Simulation Study of Spout-fluid Bed Regimes.” Aiche Journal 54 (5): 1189–202). First, the sensitivity analysis of simulation results versus the most significant parameters are conducted to find the optimum values for each parameter. Subsequently, the role of inlet gas temperature and cross-section ratios are studied in detail. The simulation results clearly demonstrate that increasing the inlet gas temperature raises particles’ velocity in the bed and affects the circulation pattern in annulus region. Additionally, it is shown that higher gas temperature leads to existence of hot spots in the annulus region. In case of jet to bed cross-section ratio, using larger ratios results in higher velocities and lower pressure drop along the bed.

The effect of competitive adsorption on the catalytic performance of H 3 PMo 12 O 40 @C catalyst for producing 2-nitro-4-methylsulfonylbenzoic acid (NMSBA) from the oxidation of 2-nitro-4- methylsulfonyltoluene (NMST) by oxygen in acetic acid has been investigated. Six kinds of acids were added into the impregnation solution as competitive adsorbates for phosphomolybdic acid in the preparation of H 3 PMo 12 O 40 @C catalyst. H 2 SO 4 , HCl, HNO 3 , CH 3 COOH and H 2 C 2 O 4 are beneficial to improving the catalytic activity of the H 3 PMo 12 O 40 @C catalyst. The corresponding optimum impregnation concentrations for H 2 SO 4 , HCl, HNO 3 , CH 3 COOH and H 2 C 2 O 4 are 0.4, 0.3, 0.3, 1.0 and 0.3 mol L −1 , respectively. The addition of H 3 PO 4 exerts a negative effect on the catalytic capability of H 3 PMo 12 O 40 @C catalyst. The results of TEM characterization show that good dispersion of H 3 PMo 12 O 40 on the surface of the H 3 PMo 12 O 40 @C catalyst is beneficial to ameliorating the catalytic ability of H 3 PMo 12 O 40 @C catalyst in the production of NMSBA from NMST by oxygen in acetic acid. The results of NH 3 -TPD indicate that the acidity of the H 3 PMo 12 O 40 @C also favors the improvement of the catalytic capability of H 3 PMo 12 O 40 @C in the oxidation of NMST to NMSBA.

A full-scale multi-environment Eulerian CFD model for a countercurrent packed-bed absorber with structured packing Mellapak 250Y was built in ANSYS Fluent 2019 R1 in order to model CO 2 capture using physical solvents. The objective of the model is to predict the overall absorber gas-liquid internal flow profiles within the complex packing geometry, while accurately predicting the hydrodynamic parameters, such as liquid holdup and pressure drop. The gas-solid and gas-liquid drag coefficients were fitted and validated using the following experimental data by Green et al. (2006. “Hydraulic Characterization of Structured Packing via X-ray Computed Tomography”; 2007. “Novel Application of X-ray Computed Tomography: Determination of Gas/liquid Contact Area and Liquid Holdup in Structured Packing.” Industrial & Engineering Chemistry Research 46: 5734–53.): dry pressure drop, irrigated pressure drop, and liquid holdup. The validated CFD model was used to study the effect of liquid distributor design on the liquid distribution in the absorber using three distributors provided with seven, thirteen, and twenty orifices of 0.2 mm diameter. The CFD model predictions revealed that the distributor with the largest number of orifices resulted in the least liquid maldistribution in the absorber, which led to increasing the overall CO 2 absorption efficiency in Selexol as a physical solvent. Also, the overall CO 2 absorption efficiency decreased with increasing the superficial liquid velocity due to the shorter contact times between CO 2 and Selexol in the absorber at higher superficial liquid velocities.

The paper addresses an exploration of the removal efficiency of banana peel ftrip(BP) towards copper and zinc ions from water and to optimize the factors involved in this adsorption process. In this sense, process optimization, kinetics, and equilibrium studies were performed in a batch process. The kinetics shows that the equilibrium reached in 60 minutes and the adsorption is favored above pH 5. The BP was firstly characterized by proximate analysis, FTIR, BET surface area, and SEM. The highest adsorption capacity for Langmuir isotherm for Cu(II) and Zn(II) onto BP was observed to be 61.728 mg/g and 55.56 mg/g respectively. Finally, the regeneration of BP was also studied up to 5 cycles. Thus, BP showed excellent adsorption characteristics during the uptake of Cu(II) and Zn(II) from wastewater effluent and can be used as low-cost agricultural waste biomass as an adsorbent.

The heat transfer of a reactor with improved Intermig impellers was numerically investigated by the finite element method (FEM) simulation software Fluent (V.19). A turbulence model utilized the standard k - ε model, and the turbulent flows in two large vortexes between vertical tubes were collided to form a strong convection. The influence of heat and mass transfer developing from the impeller diameters, the distance between the two impellers ( C 1), the rotational speed and the installation height of the bottom impeller ( C 2) were studied. The reactor was equipped with special structure vertical tubes to increase the heat exchange areas. The rate of heat transfer, including criteria such as the convective heat transfer coefficient, the Nusselt number of outside vertical tubes, and the temperature boundary layer thickness, assured the accurate control of the heat exchange mixing state. The experimental testing platform was designed to validate the simulated results, which revealed the influence order of related factors. The Nusselt number Nu was affected by various related factors, resulting in the rotation and diameter of impellers extending far beyond the distance between the two impellers ( C 1) and the installation height of the impeller ( C 2). The average temperature boundary layer thicknesses of the symmetrical and middle sections were 3.24 mm and 3.48 mm, respectively. Adjusting the appropriate parameters can accurately control the heat exchange process in such a reactor, and the conclusions provide a significant reference for engineering applications.