Minimum Spouting Velocity Research Articles

Determination of the physical and interaction properties of sorghum grains: Application to computational fluid dynamics–discrete element method simulations of the fluid dynamics of a conical spouted bed

Computational simulation is an important tool for design and improvement of industrial units. Computational fluid dynamics (CFD) coupled with the discrete element method (DEM) has been applied to simulate drying equipment that usually involves gas–solid flow. For reliable results of CFD–DEM simulations, the properties related to the interactions of the material within the industrial equipment, such as the restitution or friction coefficients, must be known. In this study, CFD–DEM was applied to simulate the fluid dynamics inside a conical spouted bed operating with sorghum grains. The physical properties of the particulate phase and the particle–particle and particle–wall interaction parameters were determined by the direct measurement approach and applied to CFD–DEM. The interaction parameters were experimentally determined, including the particle–particle interaction parameters of η=0.46, μS=0.79, and μR=0.70, and the particle–wall interaction parameters of η=0.56, μS=0.75, and μR=0.40. The simulated minimum spouting velocity and characteristic curves were compared with the experimental results. There was good agreement between the simulated and experimental results.

An ensemble model to predict the minimum spouting velocity for two types of spouted beds

Spouted beds are extensively used in different industries. The minimum spouting velocity is a critical hydrodynamic parameter needed for the design and scale-up of these systems. This study deals with an ensemble method involving Multi-Layer Perceptron (MLP) network, the Adaptive Neuro-fuzzy Inference System (ANFIS), the Gaussian Process Regression (GPR), and a Regression Tree (RT) model for predicting minimum spouting velocity for coarse particles in conical spouted beds equipped with nonporous draft tubes (CSBDTs) and conical-cylindrical spouted beds. Some dimensionless variables related to the physical properties of the conical bed and particles’ material were constructed and used as model inputs. The proposed method was validated against the measured data. The results revealed that the ensemble method was capable of predicting the minimum spouting velocity with an average absolute relative error (AARE) of 10.52% and 10.35% for the testing data points in the case of CSBDTs and conventional spouted beds, respectively. It was also shown that the proposed ensemble method provided the best results in comparison with the other methods. Therefore, the ensemble method is a useful and powerful technique for predicting the minimum spouting velocity in spouted beds with and without the draft tube.

Particle segregation in spouted bed pyrolysis reactor: Sand-coconut shell and sand-cocoa shell mixtures

The singularity of air-particle flow characteristics and segregation phenomenon are still the main obstacles for application of conical spouted bed (CSB) for fast pyrolysis. This paper aims to investigate statistically the operating parameters (minimum spouting velocity and bed pressure drop) and biomass segregation (biomass mixing index) in a CSB composed of biomass (coconut and cocoa shells) and sand mixtures. Models for the pressure drop and inlet air velocity at the minimum spouting condition and for the axial mixing index were obtained. The bed voidage does not change significantly with the increase of biomass mass fraction (coconut and cocoa shells), therefore, larger amounts of biomass can be used without greatly increasing or decreasing the inlet air velocity to stabilize the spouted regime. From the analysis of bed stability and particle segregation, significant insights were obtained for future application of the CSB for the pyrolysis of biomasses. It is recommended the use of mixtures with 40 wt% of coconut shells and 75 wt% of cocoa shells in initial pyrolysis tests in CSB reactor. The cocoa shells particles are more suitable to pyrolysis because of their higher flowability.

Prediction of pressure drop and minimum spouting velocity in draft tube conical spouted beds using genetic programming approach

The smart method of genetic programming (GP) is used to predict the operating pressure drop (ΔPs) and the minimum spouting velocity ums for conical spouted beds (CSBs) equipped with nonporous draft tubes. Accordingly, six dimensionless variables have been taken as model inputs, including crucial parameters associated with the bed and tube geometric and operating conditions. Two general correlations comprising almost all constitutive and operating variables have been derived for the first time by the GP approach. Both ΔPs and ums values predicted by the GP technique are in a fair agreement with the values corresponding to the experiments, with average absolute relative errors (AARE) of 18.9 and 19.9 %, respectively. The results of the proposed correlations show that the GP method is a powerful tool to make reasonable estimates.

Effect of operating conditions on the drying of fine and ultrafine sand in a fountain confined conical spouted bed

A study has been carried out on the influence process conditions and design parameters have on the drying in a conical spouted bed. Optimum parameters have been determined for the draft tube and the fountain confiner. Drying time is reduced when the spout region is enlarged. A distance between the bed surface and the lower end of the confiner in the 0.10–0.15 m range and a confiner of 0.5–0.9 m length minimize the drying time. Longer distances do not avoid entrainment, and shorter distances lead to higher pressure drop and minimum spouting velocity. Longer fountain confiners do not reduce significantly the drying time. Draft tubes with a reduced aperture ratio lead to longer drying times due to their adverse effect on the gas–solid contact. Aperture ratios above 60% cause a decrease in the efficiency of the process due to the higher gas flow rates required to achieve spouting regime.

Effect of operation conditions on coating of pharmaceutical pellets with a film of HPMC/PEG in a Wurster coater

Wurster coater was utilized for coating glass beads with HPMC/PEG. The effects of design and operating parameters on the coating process were evaluated. It was found that the pressure drop decreases when spraying the coating solution into the bed, indicating that spraying prevents the particles from flowing easily in the draft tube. Moreover, it was observed that the minimum spouting velocity increases during the coating process. The results indicated that increasing the entrainment zone height and decreasing the distributor hole pitch increase the coating yield, while the draft tube height did not have a significant influence on the coating yield. These findings were confirmed by thermogravimetric analysis (TGA). The degree of agglomeration intensifies when increasing the entrainment zone height, increasing draft tube height and decreasing the distributor hole pitch. Finally, scanning electron microscopy and energy dispersive X-ray spectroscopy analyses confirmed deposition of the coating material on the surface of particles.

Estimation of the minimum spouting velocity in shallow spouted beds by intelligent approaches: Study of fine and coarse particles

The minimum spouting velocity, which is an essential parameter in the design and scale-up spouted beds, has been predicted by different intelligent methods for shallow spouted beds of fine and coarse dense-particles. Four important dimensionless moduli, namely, Ar, Hb/Do, Do/Dc, and tan(γ/2) have been taken as model inputs. A single correlation for the minimum spouting velocity in the whole range of dense particle diameter, i.e., fine and coarse, leads to a high average absolute relative error (AARE) in the estimation of Ums,o due to the effect of particle size on the hydrodynamics of these beds. Accordingly, two distinct range of data sets based on the particle size have been used in all calculations. Among the models used, Gaussian Process predicts the best results for both fine and coarse particles. The coefficients of best fit in the correlations have been optimized by the well-known optimization method of Imperialist Competition Algorithm (ICA). Finally, different empirical correlations have been analysed and their results compared with those calculated by the correlations proposed. A sensitivity analysis based on the Gaussian Process approach has been conducted in order to determine the most significant parameters affecting Ums,o in shallow spouted beds of fine/coarse particles.

Paraboloid-Based Spouted Bed Drying of Paddy: Aerodynamics, Temperature Distribution, and Moisture Degradation

Aerodynamics, temperature variations in the annulus, and the moisture reduction of paddy in a paraboloid-based spouted bed (PBSB) dryer without draft tube and with solid and porous draft tubes were investigated. Draft tube caused a rapid decrease in the peak pressure drop and minimum spouting velocity when compared with PBSB without a draft tube. Pressure drops with draft tubes were 17 to 30% of the values for the PBSB without a draft tube. Temperature distribution along the bed height in the annular region during drying of paddy was also investigated. Heat-up in the spouted bed without draft tube was more rapid. The experiments were conducted for 70, 90, and 110 °C inlet air temperatures. The required length of drying time to dry the paddy with an initial moisture content of 0.35 db to a moisture content below 0.15 db could be reduced by 50–60% using a temperature of 110 °C instead of 70 °C. No constant rate period was observed. Drying took place in the falling rate period. Drying time decreased in the case of porous draft tube rather than the solid one. The highest drying rates were achieved by spouted bed without draft tube. Drying rates were in the range of 0.62–0.1, 0.51–0.06, and 0.37–0.06 (db.min−1) for the spouted bed without draft tube, with porous, and solid draft tubes, respectively.

Drying kinetics, quality and moisture diffusivity of spouted bed dried Sri Lankan black pepper

Drying of black pepper has been investigated in a lab-scale conventional spouted bed dryer. Spouting behavior of black pepper was studied, and the minimum spouting velocity was determined. The effect of operational conditions; drying temperature, air velocity and stagnant bed height on drying kinetics was analysed. The higher values of drying rates were achieved when the dryer was operated with moderately high temperatures, high airflow rates and shallow beds. The results show an increase in effective moisture diffusivity with increasing drying temperature. The highest effective moisture diffusivity of 2.03 × 10-10 m2/s was obtained at a hot air temperature of 75 °C. Extraction and analysis of essential oil from dried black pepper showed that the variation of oil yield with drying temperature is significant for drying temperatures from 45 °C to 75 °C 65 °C was selected as the best drying temperature for black pepper drying in the conventional spouted bed dryer.

Mathematical Model of Three Dimensional Spouted Bed Using Distinct Element Method

Spouted bed was simulated by a combining of Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) technique. In the simulation, DEM based on the Newton’s second law of motion was used to solve the particle motion and the fluid motion were obtained by CFD with the SIMPLE method and Upwind scheme. Programming was developed in Standard-C language and MATLABTM was used to visualize the results. The size of particles focused on this simulation is 2.5 mm in diameter (the density = 2,500 kg/m3, stiffness = 800 Nm -1). The time step used to maintain the stability of the simulation was 6.5 10-5 sec.In this simulation, three levels of the static bed height were studied: 45, 58, and 70 mm. The operating parameter effects (the static bed height on the pressure drop across the bed and the minimum spouting velocity) were investigated. The pressure drop across the bed and the minimum spouting velocity increased corresponding to the level increment. In the study of the pulsed and multi-pulsed frequency, it was found that the higher number of frequency introduced the higher heat transfer to the particles. Moreover, the effect of each type of flow on the average particles temperature was studied. The continuous flow gave the highest average particles temperature. Even though, the single pulsed flow and the multiple pulsed flows gave the lower heat transfer than continuous flow, the multiple flows produced a very good distribution in the heat transfer and also can reduce the dead zone problem of the spouted bed.

Bacaba powder produced in spouted bed: an alternative source of bioactive compounds and energy food product

Abstract This study evaluated Bacaba powder produced in a spouted bed as a source of bioactive compounds and high energy value. The conditions influencing the drying process parameters (yield, moisture level, phenolic and anthocyanin retention) as well as simultaneous optimization (optimal conditions) of production were also considered. Drying was most efficient at 75 °C using maltodextrin concentrations above 20.0% (w/w). Higher anthocyanin retention (92.52%) at 65 °C (p = 0.0003), and a maltodextrin concentration of 20.0% (w/w) resulted in high retention of phenolics (95.38%). Accordingly, the operations tested under the desirability function (68 °C, maltodextrin concentration of 21.7% w/w, and air velocity of 1.3 × minimum spouting velocity (Vjm) m s-1) resulted in a process yield of 55.04% and the dry basis (d.b.) composition results were: total phenolics (376.43 mg GAE 100 g-1), energetic value (612.64 kcal 100 g-1), lipids (47.74 g 100 g-1), carbohydrates (27.79 g 100 g-1), protein (15.10 g 100 g-1), and dietetic fiber (8.45 g 100 g-1). The high solubility (92%), flowability (14%), energy, and bioactive characteristics of Bacaba powder suggest the potential for many applications, such as development of dietary supplements, high-energy drinks, milk-based and instant products, and bakery products.

On the stability of Würster fluid bed of pharmaceutical pellets

The flow of pharmaceutical pellets in a Würster fluid bed (WFB) was characterized by a frequency domain analysis of pressure fluctuations. Pellets with a diameter of 0.780mm and density of 1.225kg/m3 were used in the experiments. Different flow structures were identified in the bed, including bulk movement of pellets in the annulus (f<5Hz), bulk movement of pellets inside the draft tube and bulk horizontal movement of pellets through the entrainment zone (5<f<15Hz), and clustering (15<f<145Hz). The minimum spouting velocity was also measured experimentally. Effects of bed height, distance of the entrainment zone, and distributor hole pitch on minimum spouting velocity were investigated. It was found that the minimum spouting velocity increased with increasing bed height and distance of the entrainment zone while it decreased with increasing distributor hole pitch. A correlation was developed for estimating the minimum spouting velocity in WFBs containing pharmaceutical pellets. The correlation fit the experimental data satisfactorily. Studying the WFB hydrodynamics and determining the minimum spouting velocity provides information that can be used to properly design, operate, and scale up such systems.

Analysis of the dynamics of paste drying in a spouted bed

Although there are some models available in the literature for paste drying in spouted beds, few of them have focused on transient analysis of dynamical systems. Our objective was to integrate experiments and simulations of a dynamic model to investigate the transient response to disturbances and interruptions in the feed flow during paste drying in a spouted bed with inert particles. The spouted bed consisted of a cylindrical column with 50.0 cm of height and 20.0 cm of diameter. Drying tests were performed at inlet gas temperatures of 70 °C and 100 °C and inlet air flow 30% above the minimum spouting velocity. A 5% w/w suspension of calcium carbonate was used as paste material, and glass spheres of 2.2 mm were used as inert materials. Different patterns of step function changes were tested in the paste feed flow rate. A lumped parameter model was used to predict mass and heat transfer during the drying. Experiments and simulations were in good agreement.

Deciphering conical spouted bed hydrodynamics using high intensity microphone

Pressure fluctuations emanating from three dimensional (3D) conical spouted bed using dense zirconia particles (6200 kg/m3) were investigated via high intensity microphone. The effects of static bed height and gas velocity on the spouted bed hydrodynamics were studied. Studies reveal that unprocessed pressure signals are adequate to decipher the various hydrodynamic regimes of the spouted bed. Simple root mean square (RMS) of pressure fluctuation signals can be used to identify the spouted bed hydrodynamic regimes. Pressure fluctuation signals were further analyzed in the frequency domain and the analysis shows drastic lowering of peak intensity of power spectral density at minimum spouting velocity. The differentiating factor of the present study being that the pressure signals exhibit distinctly identifiable general trend associated with various spouted bed regimes and such trend is further confirmed by the frequency analysis. This very feature could be useful tool in fabricating TRISO particles in single batch process. Experimental data on minimum spouting velocity (Ums) was compared with relevant correlations and the results were discussed.

Smart models to predict the minimum spouting velocity of conical spouted beds with non-porous draft tube

The minimum spouting velocity, Ums, is a critical topic, and an exact prediction of this parameter certainly can be useful in design and scale-up of the conical spouted beds. In the present study, a number of intelligence methods was applied to predict Ums in conical spouted beds equipped with non-porous draft tube. Six dimensionless moduli comprising the essential operating and geometric parameters, namely, the gas density, the gas viscosity, the particle diameter, the particle density, the cone angle, the nozzle diameter, the static bed height, the length of the tube, the entrainment height, and the tube diameter were taken as models inputs. The total number of data samples is 1004 that includes 572 data points to train the smart models and 432 data points to test those models. The self-organizing map (SOM) was used to examine the effect of inputs correlation on the performance of the chosen smart models. Among the different models, a multi-layer perceptron (MLP) trained by Bayesian Regulation (BR) incorporating SOM i.e. (MLP-BR-SOM) predicted the best results with mean relative error of 9.71 and 12.45% for train and test data, respectively. In addition, sensitivity analysis (SA) of the proposed model was performed and it was shown the Ar, DT/D0, and H0/D0 have most influential parameters in prediction of Ums.

Characterization of flow properties of pharmaceutical pellets in draft tube conical spout-fluid beds

Experimental studies of the hydrodynamic performance of the draft tube conical spout-fluid bed (DCSF) were conducted using pharmaceutical pellets. The experiments were carried out in a DCSF consisted of two sections: (a) a conical section with the cross section of 120 mm×250mm and the height of 270mm, (b) a cylindrical section with the diameter of 250mm and the height of 600mm. The flow characteristics of solids were investigated with a high speed camera and a pezoresistive absolute pressure transducer simultaneously. These characteristics revealed different flow regimes in the DCSF: packed bed at low gas velocities, fluidized bed in draft tube at higher gas velocities until minimum spouting, and spouted bed. The stable spouting was identified by the presence of two dominant frequencies of the power spectrum density of pressure fluctuation signature: (i) the frequency band 6–9Hz and (ii) the frequency band 12–15Hz. The pressure drops across the draft tube as well as the annulus measured in order to better recognize the flow structure in the DCSF. It was observed that the pressure drop across the draft tube, the pressure drop across the annulus, and the minimum spouting velocity increase with the increase in the height of draft tube and distance of the entrainment zone, but with the decrease in the distributor hole pitch. Finally, this study provided novel insight into the hydrodynamic of DCSF, particularly minimum spouting and stable spouting in the DCSF which contains valuable information for process design and scale-up of spouted bed equipment.

Adjustment of the Minimum Spouting Velocity in a Conical Spouted Bed from Artificial Neural Networks

The minimum spouting velocity is one of the fundamental parameters in the application of the conical spouted bed pyrolysis, gasification and combustion, therefore it is necessary the adequate calculation and the use of a correlation with good adjustment, for this an artificial neural network has been applied, in order to improve the correlations of the literature. Six variables that involve different geometrical parameters and operation of the bed have been used. With the purpose to compare the results of the model with the experimental data and those predicted by the empirical equations, the quadratic error has been used. Although there is a complex relationship between the input variables and the output variables, and despite numerous of available data, the training and test steps of the network show a good adjustment with respect to the experimental values. This shows that an artificial neural network is an agile method to predict the minimum velocity of the bed at the pump, especially when the relationship between geometric parameters, operating parameters and minimum speed is complex and difficult to define.

Drying and extraction of astaxanthin from pink shrimp waste (Farfantepenaeus subtilis): the applicability of spouted beds

Abstract In this study, the spouted bed drying technique was used to obtain powder from shrimp wastes, with high quality for subsequent extraction of astaxanthin using vegetable oil, as alternative to organic solvents. Shrimp waste paste was dried in three inlet air temperatures (70, 80 and 90 °C), and air velocity used in the experiments was 100% over minimum spouting velocity. The minimum spouting, the velocities were 1.23, 1.33 and 1.39 m/s, for temperatures of 90, 100 and 110 °C respectively. The powder obtained in this work shows properties comparable to of the commercial products, indicating that the spouted bed is an alternative technique to obtain powdered products with quality good, at low cost and suitable for subsequent extraction of astaxanthin. The extractions of astaxanthin from shrimp waste were performed using palm olein at three different temperatures (50, 60, and 70 °C). At these conditions, maximum extraction of astaxanthin was 29.814µg/g of dried waste. The extraction kinetics were modeled using a simplified mass transfer kinetic model which showed a good agreement (0.9685<r2<0.9912), between the experimental and calculated data.

An experimental investigation on the drying of thorium oxalate in a batch spouted bed dryer

In the present work, drying of thorium oxalate slurry has been investigated using a batch spouted bed dryer containing inert spherical glass particles. The results show that the fine and discretized dried particles could be produced in this type of dryer. Moreover, the effect of temperature and velocity of inlet air on the drying kinetics of thorium oxalate has been studied. Drying experiments have been conducted at three different temperature (90, 100 and 110 °C), and three different air inlet velocities (1, 1.2 and 1.5 times the minimum spouting velocity). Five widely applied models with velocity and temperature dependent constant were chosen to predict the drying kinetic. Three criteria of statistical analysis including the root mean square error (ERMS), reduced Chi-squared (χ2), and the coefficient of determination (R2) have been used to analyze the quality of fitted models. All examined models were satisfactory but the predication capability of Logarithmic model was the best for describing the drying kinetics of thorium oxalate.

Estimation of Minimum Spouting Velocity in a Rectangular Spouted Bed

A study was conducted to explore the effects of static bed height, nozzle diameter, cone angle, and particle properties on the minimum spouting velocity in a 4 in × 1 in rectangular spouted bed. Tests were conducted with various solids materials (including 871 μm HPDE pellets, 3.2 mm nylon beads, 707 μm glass beads, and 1.5 mm alumina spheres), two gas inlet nozzle diameters, and two cone angles. Experimentally obtained minimum spouting velocities were compared to existing published correlations developed for cylindrical spouted beds. In each case, it was determined that the existing correlations did not adequately predict the minimum spouting velocity for a rectangular spouted bed. A new correlation is proposed.