Hydrodynamic study of gas-solid flow in an internally circulating fluidized bed (ICFB) using experimental and CFD techniques

Circulating fluidized bed (CFB) solid circulation systems are widely used in the process of catalyst regeneration, coal gasification, coking, thermal cracking, drying, incineration of solids waste as well as many other applications. However, conventional circulating fluidized beds require a tall tower as a solids riser and externally circulation of solids with the help of cyclones. Therefore to alleviate such problems encounter with CFB, several new generations fluidized beds have been developed. A circulating fluidized bed called as an internally circulating fluidized bed (ICFB) with a draft tube is one of the novel design. An ICFB is a type of fluidized bed with centrally located draft tube, which divides the bed into two sections called as annular section and draft tube riser. Because of simple and flexibility of operation have its own advantages. Literature review shows that there is still considerable uncertainty in establishing complete hydrodynamics of ICFB. Only few computational fluid dynamics (CFD) simulation studies were reported on ICFB and that to most of them considered 2D geometry of ICFB. Moreover, in all CFD simulations, particles were assumed to mono sized particles

Prediction of solid recirculation rate and solid volume fraction in an internally Circulating Fluidized bed (ICFB)

Numerical & experimental study of gas and solid flow in an internally circulating fluidized bed (ICFB). The gas and solid hydrodynamics have been simulated by using the commercially available computational fluid dynamics (CFD) softwar e package, ANSYS’s Fluent. A three dimensional geometry was used to represent key parts of a laboratory ICFB. In 3D ICFB, the two - fluid Eulerian model with kinetic theory of granular flow option and the various drag laws like Gidaspow, Syamlal - Obrien, Gibl aro and Arastoopour drag models used to predict the hydrodynamic behavior of ICFB. The simulation results by four drag laws show that the Gidaspow and Arastoopour drag models predict the fluidization dynamics in terms of flow patterns, void fractions and a xial velocity fields were compared with experimental data. With the Arastoopour drag model the simulations are giving the best fits to the experimental data. The effect of superficial gas velocity, presence of draft tube on solid hold - up distribution, soli d circulation pattern, and variations in gas bypassing fraction for the 3D ICFB investigated through CFD simulations. The mechanism governing the solid circulation in an ICFB has been explained based on gas and solid dynamics obtained from the simulations

Wound healing activity of topical application of Aloe vera gel in experimental animal models

Aloe vera gel of 50% and 96.4% were tested for its wound healing activity by topical application in experimental rats. The effect of Aloe vera gel on wound healing was evaluated by wound excision model and histopathology was used to study the effect on wound healing. The effect produced by Aloe vera gel with reference to wound contraction, wound closure, decrease in surface area of wound, tissue regeneration at the wound site and histopathological characteristics were significant in treated rats. The effect of Aloe vera gel on biochemical studies revealed significant increase in collagen and decreased hexosamine content and malondialdehyde levels when compared with control. The present study thus provided scientific rationale for the traditional use of Aloe vera gel for management of wounds

Development of a new AgriSeq 4K mid-density SNP genotyping panel and its utility in pearl millet breeding

Pearl millet is a crucial nutrient-rich staple food in Asia and Africa and adapted to the climate of semi-arid topics. Since the genomic resources in pearl millet are very limited, we have developed a brand-new mid-density 4K SNP panel and demonstrated its utility in genetic studies. A set of 4K SNPs were mined from 925 whole-genome sequences through a comprehensive in-silico pipeline. Three hundred and seventy-three genetically diverse pearl millet inbreds were genotyped using the newly-developed 4K SNPs through the AgriSeq Targeted Genotyping by Sequencing technology. The 4K SNPs were uniformly distributed across the pearl millet genome and showed considerable polymorphism information content (0.23), genetic diversity (0.29), expected heterozygosity (0.29), and observed heterozygosity (0.03). The SNP panel successfully differentiated the accessions into two major groups, namely B and R lines, through genetic diversity, PCA, and structure models as per their pedigree. The linkage disequilibrium (LD) analysis showed Chr3 had higher LD regions while Chr1 and Chr2 had more low LD regions. The genetic divergence between the B- and R-line populations was 13%, and within the sub-population variability was 87%. In this experiment, we have mined 4K SNPs and optimized the genotyping protocol through AgriSeq technology for routine use, which is cost-effective, fast, and highly reproducible. The newly developed 4K middensity SNP panel will be useful in genomics and molecular breeding experiments such as assessing the genetic diversity, trait mapping, backcross breeding, and genomic selection in pearl millet

Prediction of Solid Recirculation Rate and Solid Volume Fraction in an Internally Circulating Fluidized Bed

This paper presents a numerical study of gas and solid flow in an internally circulating fluidized bed (ICFB). Two-fluid Eulerian model with kinetic theory of granular flow option for solid phase stress closure and various drag laws were used to predict the hydrodynamic behavior of ICFB. 2D and 3D geometries were used to run the simulations. The 2D simulation results by various drag laws show that the Arastoopour and Gibilaro drag models able to predict the fluidization dynamics in terms of flow patterns, void fractions and axial velocity fields close to the experimental data. The effect of superficial gas velocity, presence of draft tube on solid hold-up distribution, solid circulation pattern, and variations in gas bypassing fraction for the 3D ICFB are investigated. The mechanism governing the solid circulation and solids concentration in an ICFB has been explained based on gas and solid dynamics obtained from the simulations. Predicted total granular temperature distributions in the draft tube and annular zones qualitatively agree with experimental data. The total granular temperature tends to increase with increasing solids concentration in the dilute region (ε < 0.1) and decreases with an increase of solids concentration in the dense region (ε > 0.1). In the dense zone, the decreasing trend in the granular temperature is mainly due to the reduction of the mean free path of the solid particles

Hydrodynamics Study of Gas-Solid Flow Pattern in an Internally Circulating Fluidized Bed with a Draft Tube

Circulating fluidized beds (CFB) are widely used in coal combustion and gasification processes. These CFBs suffer from having very tall column as a solids raiser and accompanying additional external circulation of solids through cyclone. To avoid the external circulation accessories a compact internally circulating fluidized bed (IFCB) is developed. ICFB represent a modified spouted fluidized bed with a draft tube inside to avoid problem of gas bypassing. The hydrodynamics of ICFB have studied using combination of experiments and CFD simulations. Solids circulation rate and bed pressure drop were measured using high speed camera and pressure manometers for a wide range of particle sizes and bed heights. 3D Twofluid Eulerian granular flow model was adopted to predict the hydrodynamic behavior of ICFB. Effect of gas velocity, presence of draft tube on solid hold-up distribution, solid circulation pattern and variations in gas bypassing fraction in the ICFB have been investigated with the help of CFD simulations. CFD validation against the experimental data is mad

Experimental investigation of hydrodynamics of gas-solid flow in an internally circulating fluidized bed

Hydrodynamic study of gas and solid flow in an internally circulating fluidized bed (ICFB) is made in this paper using a high-speed camera and pressure probes for the laboratory 0.3 m × 0.27 m column having an internal draft tube. Experiments were conducted using sand particles of Geldart B and Geldart B-D groups. At each run the standard pressure-flow curves for both the draft tube and annular region beds, and the moving wall particle velocity in the annular bed region were measured. The effects of superficial gas velocity, static bed height, and draft tube gap height on pressure drop profiles, solid circulation patterns, and gas bypassing dynamics for the ICFB were investigated extensively. Unlike the conventional CFB, the pressure drop in ICFB is further decreased with superficial gas velocity after the minimum spouting fluidization, followed by yielding a cross-over in the pressure drop of the annular bed compared to the draft tube. Pressure drop in the draft tube increases with an increase of static bed height and gap height between the draft tube bottom and the air distributor. The gas bypassing fraction increases with an increase in gap height and decreases with increased bed height and mean particle size. The mechanism governing the solid circulation and the pressure losses in an ICFB has been elaborated based on gas and solid dynamics obtained from the experimental data

Hydrodynamic Study of Gas–Solid Internally Circulating Fluidized Bed Using Multiphase CFD Model

In the present work, hydrodynamic study of gas and solid flow in an internally circulating fluidized bed (ICFB) was carried out using the CFD multiphase model. Two- (2D) and three-dimensional (3D) computational meshes were used to represent physical ICFB geometries of 0.186-m and 0.3-m diameter columns. The model approach uses the two-fluid Eulerian model with kinetic theory of granular flow options to account particle–particle and particle–wall interactions. The model also uses various drag laws to account the gas–solid phase interactions. The 2D simulation results by various drag laws show that the Arastoopour and Gibilaro drag models predict the fluidization dynamics in terms of flow patterns, void fractions, and axial velocity fields in close agreement with the Ahuja et al. (2008) experimental data. Three dimensional simulations were also carried out for a large-scale ICFB. The effects of superficial gas velocity and the presence of draft tube on solid holdup distribution, solid recirculation pattern, and gas bypassing dynamics for the 3D ICFB were investigated extensively. The mechanism governing the solid circulation and the pressure losses in an ICFB has been explained based on gas and solid dynamics obtained from these simulations. Predicted total granular temperature distributions in 3D ICFB draft tube and the annular zone are qualitatively in agreement with the experimental data. The total granular temperature tends to increase with the increase in solids concentration in the dilute region (ϵ 0.1)

Computational and experimental study of the effect of inclination on hydrocyclone performance

In this paper, the effect of inclination on hydrocyclone performance is studied using both computational fluid dynamics (CFD) and experimental methods. Experiments with water medium and the corresponding water-air two-phase CFD simulations in a 75 mm diameter cyclone are carried out at various inclined positions to the vertical plane. The two-phase CFD flow analysis shows that the water split to underflow decreases as the inclination increases, which is consistent with the experiments. The predicted flow velocity profiles were analyzed for different inclinations. An increase in the inclination results the air-core size reduction and reduced pressure drop profiles. Experimental classification also performed using the silica slurry. The experimental analysis shows the increased cut-size and the reduced water split with the inclination. Cross validation of inclined cyclone's CFD data is attempted with Electrical Resistance Tomography (ERT) and High speed video imaging experiments. The inclination effect on hydrocyclone flow field is further analyzed in terms of turbulence parameters; turbulent intensities, and radial RMS velocities. Turbulent dispersion of the particles is calculated using the CFD data and plotted by using a dispersion index formulation. Fish hook phenomena and possible mechanism of particle classification under the influence of inclination is also explained. Experimentally measured cut size and water recovery to underflow for 10 wt% silica slurry at various inclinations are compared with numerical predictions. Predicted efficiency curves are found in a close agreement with experiments for all the inclinations

simulation study of a Turkish container terminal

Due to a long-lasting increase in global trade, only interrupted by the late-2000s economic crisis, container traffic has grown dramatically. As a result, new terminals have opened and existing terminals face much higher container handling than before. In order to meet these challenges, one of the biggest container terminals in Turkey has begun to reconsider its terminal operations and to achieve improvements of its overall logistics performance. Because the factors impacting the terminal's performance are highly interrelated, a simulation model was developed to analyze the terminal operations, to identify potential bottleneck resources and to highlight directions for the future development of the configuration and the operational control system. For a long-established terminal like the one considered in this study the options for improving the overall performance are limited by the geographical dimensions and by the existing terminal equipment. By use of the simulation model the terminal operations are evaluated under different workload scenarios and alternative configurations are tested in order to support strategic decisions on the terminal's development