Volume 16, Issue 3 -

A newly designed laboratory scale thin film reactor (TFR) was tested for the decarboxylation of anacardic acid in Cashew Nut Shell Liquid (CNSL) and to investigate the fluid flow behaviour under the influence of temperature since the fluid properties like viscosity and density have strong dependence on temperature. The CNSL containing 60–65 % anacardic acid was decarboxylated to produce cardanol and CO 2 at wall temperatures ranging between 393 K and 433 K, respectively. The characteristics of the CNSL, essentially a non-Newtonian fluid, was analysed at different temperatures and its rheological behaviour was studied using the well-known power law model. It was observed that CNSL follows a pseudoplastic behaviour and its viscosity, along with the liquid residence time, was found to decrease till 413 K, while a further increase in temperature resulted in product degradation due to charring, accompanied by an increase in viscosity and residence time. Using measured values for the viscosity, the film thickness was calculated for each wall temperature within the 393–433 K temperature range, showing an increase of the film thickness with temperature and viscosity. Computational Fluid Dynamics (CFD) studies were carried out for the first time for this reactor configuration, using the volume of fluid (VOF) model for the reactive flow. The results obtained from these simulations were in concurrence with the experimental outcomes: velocity profiles along the length of the reactor show its highest values at a wall temperature of 413 K, while lower velocity values were observed when the temperatures were lower or greater than 413 K.

Irradiated roast treatment and the ammonia leaching processing were conducted to deal with the low-grade oxide zinc ores. The ZnCO 3 phase was hard to be attended, which was the reason for the low leaching rate of the complicated zinc ores. The mineral phase transformation of the ZnCO 3 phase was generated after the ores irradiated in the microwave at the temperature of 673 K. The irradiated ores generated more small particles, it was the reason that the leaching rate of the complicated zinc ores was increased. When the leaching processing of the irradiated roasted ores was conducted under the conditions of the total ammonia concentration of 6 mol/L, the liquid to solid phase ratio of 11:1, the leaching temperature of 298 K, the leaching time of 150 min and the stirring speed of 400 rpm, 88.3 % of zinc could be achieved, which was the maximum leaching rate of the irradiated ores.

In this work the influences of solid viscosity and the way to scale-down traditional drag models on the predicted hydrodynamics of Geldart A particles in a lab-scale gas-solid bubbling fluidized bed are investigated. To evaluate the effects of drag models, the modified Gibilaro et al. drag model (constant correction factor) and the EMMS drag model (non-constant correction factor) are tested. And the influences of solid viscosity are assessed by considering the empirical model proposed by Gidaspow et al. (1997, Turbulence, Viscosity and Numerical Simulation of FCC Particles in CFB. Fluidization and Fluid-particle Systems, AIChE Annual Meeting, Los Angeles, 58–62) and the models based on kinetic theory of granular flow (KTGF) with or without frictional stress. The resulting hydrodynamics by incorporating the different combinations of the drag model and solid viscosity model into two-fluid model (TFM) simulations are compared with the experimental data of Zhu et al. (2008, Detailed Measurements of Flow Structure inside a Dense Gas-Solids Fluidized Bed.” Powder Technological 180:339–349). The simulation results show that the predicted hydrodynamics closely depends on the setting of solid viscosity. When solid viscosity is calculated from the empirical model of Gidaspow et al., both drag models can reasonably predict the radial solid concentration profiles and particle velocity profiles. When the KTGF viscosity model without frictional stress is adopted, the EMMS drag model significantly over-estimates the bed expansion, whereas the modified Gibilaro et al. drag model can still give acceptable radial solid concentration profiles but over-estimate particle upwards and downwards velocity. When KTGF viscosity model with frictional stress is chosen, both drag models predict the occurrence of slugging. At this time, the particle velocity profiles predicted by EMMS drag model are still in well agreement with the experimental data, but the bed expansion is under-estimated.

Ag modified mesoporous molecular sieves Ti-HMS were prepared by in-situ synthesis (Ag/Ti-HMS-I), deposition-precipitation method (Ag/Ti-HMS-D) and ultrasound-assisted impregnation methods (Ag/Ti-HMS-U), respectively. The catalytic performance of catalysts in the oxidative desulfurization(ODS) of benzothiophene with hydrogen peroxide (H 2 O 2 ) has been investigated. The physicochemical properties of the catalysts were characterized by XRD, SEM, BET and FT-IR techniques. Experimental results showed that the catalyst Ag/Ti-HMS-U exhibited the best catalytic activity, and this maybe because the catalyst possessed relatively good mesoporous structure and high Ag dispersion. Under the best operating condition for the catalytic oxidative desulfurization: temperature 60 °C, atmospheric pressure, 0.1 g catalysts, 8 molar ratio of hydrogen peroxide to sulfur, using acetonitrile as extraction solvent for double extraction, the sulfur content in model diesel fuel (MDF) was reduced from 800 ppm to 17 ppm with 97.8% of total sulfur after 1 h.

Our rigorously validated Computational Fluid Dynamics (CFD) model (Basha Omar, M., L. Weng, Z. Men, and I. Morsi Badie. 2016. “CFD Modeling with Experimental Validation of the Internal Hydrodynamics in a Pilot-Scale Slurry Bubble Column Reactor.” International Journal of Chemical Reactor Engineering 14(2):599–619), was used to predict the effects of spargers design and internals configuration on the local hydrodynamics and flow structure in a pilot-scale (0.3-m ID) and a large-scale (10-m ID) Slurry Bubble Column Reactors (SBCRs), operating under Fisher-Tropsch (F-T) process conditions. In the pilot-scale SBCR without internals, the 6-arms spider created small/fast liquid recirculations in the vicinity of the sparger and slow/large liquid recirculations at about 1.2 times reactor diameter, whereas, the 3-concentric-rings and perforated plate spargers created slow/large recirculations throughout the reactor. In the pilot-scale SBCR with internals, spargers with downward-pointing orifices created larger Sauter mean bubble diameters (ds), leading to more effective solids suspension when compared with those with upward-pointing orifices. Also, 3-concentric-rings spargers resulted in larger Sauter mean bubble diameter values when compared with those of 6-arms spiders. In the large-scale SBCR provided with a large 3-concentric-rings sparger, the effects of vertical parallel and bundled internals on the local hydrodynamics and flow structures were predicted. Bundled internals led to slower and smaller liquid recirculations, smoother radial gas holdup profiles, larger average gas bubbles size, and smaller local gas holdups, when compared those predicted when using parallel internals.

An experimental study was performed to investigate the effects of spouting gas velocity, fluidizing gas velocity, sound wave frequency and sound wave pressure level on fluidization behaviors of ultrafine particles in an acoustic spout-fluid bed with a draft tube. A half-cylinder with a diameter of 120 mm and height of 1200 mm was used as the fluidization column, TiO 2 ultrafine particles with an average diameter of 290 nm were employed as the bed materials while the high-speed atmosphere jet was utilized as the spouting gas. Results showed that high-speed jet as spouting gas could effectively disrupt the agglomerates of TiO 2 ultrafine particles and reduce the agglomerate size significantly. The introduced fluidized gas in annulus was conducive to eliminate dead-zone in the bottom of bed. Sound wave could break bubbles, restrain channeling making the axial fluidization state in annular region to be more uniform and homogeneous, thus significantly improved the fluidization quality of agglomerates in the annulus, reduced the minimum spouting velocity of particles, and promoted the stable circulation of inner particles in spout-fluid bed with a draft tube.

Because of the complexity of flow and the opacity of sludge, usually we can’t gain a precise and comprehensive sight of sludge flow type and its associated flow characteristics in the anaerobic digestion (AD) reactor. In the present study, we focused on the sludge rheological properties as well as the flow behavior in the digester. The viscosity decreased with the increase of shear rate, and sludge as a kind of pseudo-plastic fluid was proved. Based on computational fluid dynamics (CFD), taking sludge rheological index and rotational speed into consideration, then the flow field distribution in the digester was obtained. The fluid velocity raised with increase in rotational speed, moreover, fluid near blades had higher velocity while it was almost stagnant in the areas near reactor bottom and top as well as reactor wall and stirring shaft. The effect of rheological index on improving the velocity of fluid farther from impeller exceeded the influence on fluid at the impeller installation height. Regarding dead zone fraction as an indicator of the mixing effect, it was recommended that the suitable rotational speed for AD of 96 % moisture content sludge is 40 r/min. Finally, the reactor performance was optimized respectively from impeller form and reactor configuration, the results showed that both combined impellers and oval reactor can reduce dead zone volumes and produce a better mixing effect.

The bio-oil from fast pyrolysis of cornstalks was used as substitute of phenol to synthesize resol resin as an ideal wood adhesive. The effects of formaldehyde/phenol (F/P) molar ratios and oil/phenol (O/P) weight ratios on rehology, thermal cure, thermal resistance and adhension of plywoods were investigated. With the increase of bio-oil used in bio-resol, the gel time of the prepared bio-oil modified resol resin (bio-resol resin) increased gradually, and the exothermic peak temperature of thermal cure shifted slightly higher. It was found that the bio-resin with bio-oil/phenol = 0.5 (weight ratio) and F/P = 1.5 (molar ratio) had the best comprehensive properties. The plywoods made with the bio-resol resins fulfilled the standards of E 0 and type I plywood, implying the bio-resol resins was a new environment-friendly adhesive.

This paper deals with the design, analysis and optimization of micro-mixer for fluids having very low diffusivity (in the order of 10 −12 m 2 /s) to be used in Lab on Chip (LOC) for medical diagnosis. As flow is laminar and the cross-sectional area is in microscale, the viscous forces are strong causing the fluids to be transported in streamline with minimum diffusion. The main objective in designing a micro mixer is to achieve complete mixing with minimum channel length and pressure drop. In this work a passive micro mixer with two inlets and one outlet (Y shaped passive micro mixer) with obstacles in various shapes and sizes is modelled, to study the effect of mixing. After a CFD analysis, Analysis of variance (ANOVA) of 3 K design with 3 parameters as well as a 2 K design with 4 parameters was performed to study the effect of parameters on mixing index (mixing length) and pressure loss. There is a negative correlation between the response obtained for mixing length and pressure loss while varying the parameters. This makes it difficult to predict the optimum configuration. Taguchi method is used to obtain an optimum configuration to overcome this negative correlatiozn.

In this article, we investigate the effects of Arrhenius activation energy with binary chemical reaction and convective boundary condition on natural convective flow over vertical frustum of a cone in a Buongiorno nanofluid under the presence of thermal radiation. The zero nanoparticle flux condition is used at the surface of frustum of a cone rather than the uniform wall condition to execute physically applicable results. For this complex flow model, a suitable non-similarity transformations are used initially and then Bivariate pseudo-spectral local linearisation method is used to solve the non-similar, coupled partial differential equations. Further, the convergence test and error analysis are conducted to verify the accuracy of numerical method. The effects of flow influenced parameters on the non-dimensional velocity, temperature, nanoparticle volume fraction and regular concentration profiles as well as on the skin friction, heat transfer rate, nanoparticle and regular mass transfer rates are analyzed.