Six-blade Impeller Research Articles

Improvement of Technologies for Isolation and Purification of Biologically Active Substances from Plant Raw Materials

Introduction. Improving the technologies for isolating and purifying biologically active substances from plant materials is an important task for the pharmaceutical, food and cosmetic industries. Technology development often requires changes to the design of existing equipment. During the modernization of equipment for the implementation of new technologies, it is possible to improve its configuration, which makes it possible to significantly increase the yield of active substances at minimal cost. To increase the efficiency of the process of isolating hesperidin from plant materials, we proposed to use a number of technological solutions. In particular, it is proposed to use mixing devices with the configuration of impellers obtained by computational fluid dynamics, when using a Soxhlet extractor to use a heated extraction chamber, by adding an external coil jacket, which makes it possible to regulate the temperature inside the extraction chamber to accelerate the processes of diffusion and mass transfer, and to select the solvent and extractant on the basis of thermodynamic models by calculation.Aim. Improving the technology for isolating and purifying hesperidin from plant materials using modernized equipment.Materials and methods. Flow distribution in extraction apparatuses was modeled using computational fluid dynamics methods. To evaluate the results obtained on the basis of modeling, a number of experiments were carried out, the object of which was the peel of an orange (dried flavedo and albedo, grinding degree 0.1–0.2 mm, moisture content 3.5 %). The quantitative content of the flavonoid complex in terms of hesperidin was determined by direct spectrophotometry at a wavelength of 290 nm, the quantitative content of hesperidin was determined gravimetrically. Statistical data processing was performed using Minitab v21 software (Minitab Inc., USA), differences were considered statistically significant at p < 0.05.Results and discussion. Based on the methods of computational fluid dynamics, to intensify the processes of mixing and dissolution at the stages of preliminary degreasing of raw materials and extraction, a six-bladed impeller was designed, which makes it possible to accelerate these processes by creating axial and radial flows of fluid movement in a capacitive apparatus and maintaining raw materials in suspended state in the volume of liquid at low mixing speeds and energy consumption. Equipping the extraction chamber with a coiled jacket made it possible to significantly increase the solubility of the active substance and extract more of the target component in one extraction cycle. A technology for the isolation and purification of hesperidin was developed, and the parameters of the processes were determined and optimized.Conclusion. As a result of the study, it was shown that it is possible to intensify the processes of extraction and dissolution of active substances by selecting mixing devices using the method of computational fluid dynamics. To isolate poorly soluble compounds from dense raw materials (roots, bark, etc.), a modification of the Soxhlet apparatus with a heated extraction chamber was proposed. Modernization of typical technological units made it possible to obtain the substance of hesperidin with a yield of up to 95 % and a purity of up to 90 % with a single recrystallization.

Space-time frequency spectra analyses of the unsteady cavitating vortical flows inside a mixed-flow pump

The objective of this paper is to investigate the space-time frequency spectra for cavitating flows in a mixed-flow pump by using both fast Fourier transform and wavelet transform. Unsteady cavitating flows in a mixed-flow pump are numerically investigated by using the Reynolds-averaged Navier-Stokes method, which is closured with SST k-ω turbulence model and Zwart cavitation model. The cavitation performance is fairly predicted when compared with available experimental data. There are two stages for unsteady cavitation evolution during one impeller rotating cycle, including the cavity growth stage and diminution stage. The cavitation in the impeller is characterized by the spatial non-uniform distribution since a high-pressure region presents at the impeller inlet plane. The pressure amplitude decreases when the cavitation becomes severer at a smaller operating velocity. Besides, the dominant frequency in the impeller is the impeller rotating frequency (fn), i.e. the cavity evolution frequency. Due to the rotor-stator interaction from the six-blade impeller, there is a dominant long-term frequency of 6fn in the intake duct and the diffuser inlet. Furthermore, a broadband low-frequency around 1.5fn exhibits near the diffuser exit, and the 1.5fn amplitude varies over time corresponding to different corner-vortex dynamics. Therefore, wavelet analysis is a more favorable and practical method to obtain time-dependent frequency information for unsteady cavitating flows.

Effects of Impeller Geometry on the 11α-Hydroxylation of Canrenone in Rushton Turbine-Stirred Tanks.

The 11α-hydroxylation of canrenone can be catalyzed by Aspergillus ochraceus in bioreactors, where the geometry of the impeller greatly influences the biotransformation. In this study, the effects of the blade number and impeller diameter of a Rushton turbine on the 11α-hydroxylation of canrenone were considered. The results of fermentation experiments using a 50 mm four-blade impeller showed that 3.40% and 11.43% increases in the conversion ratio were achieved by increasing the blade number and impeller diameter, respectively. However, with an impeller diameter of 60 mm, the conversion ratio with a six-blade impeller was 14.42% lower than that with a four-blade impeller. Data from cold model experiments with a large-diameter six-blade impeller indicated that the serious leakage of inclusions and a 22.08% enzyme activity retention led to a low conversion ratio. Numerical simulations suggested that there was good gas distribution and high fluid flow velocity when the fluid was stirred by large-diameter impellers, resulting in a high dissolved oxygen content and good bulk circulation, which positively affected hyphal growth and metabolism. However, a large-diameter six-blade impeller created overly high shear compared to a large-diameter four-blade impeller, thereby decreasing the conversion ratio. The average shear rates of the former and latter cases were 43.25 s-1 and 35.31 s-1, respectively. We therefore concluded that appropriate shear should be applied in the 11α-hydroxylation of canrenone. Overall, this study provides basic data for the scaled-up production of 11α-hydroxycanrenone.

Numerical investigation of flow behavior in double-rushton turbine stirred tank bioreactor

The current research focuses on the numerical simulation to scrutinize the divergent flow characteristics in a stirred tank bioreactor. The reactor is composed of a cylindrical flat-bottom tank equipped with two Rushton six-blade impellers and four baffles on the wall of the tank. The turbulent flow within the reactor is modeled with the Large Eddy Simulation model. The traditional subgrid model of Smagorinsky was used to solve turbulent small-scale structures with Smagorinsky constant C s = 0.1 The influence of the reactor components (i.e., cylindrical wall, baffles, shaft, and Rushton turbines) on the liquid-flow field has been obtained using the immersed boundary method. A highly parallelized computer code is developed to perform the simulation on a multi-core Graphics Processing Unit platform. The results are demonstrated in phase average flow velocities and turbulent statistics, with validation from the available experimental data reported in the literature.

APPLICATION OF THE TEMPERATURE OSCILLATION METHOD IN HEAT TRANSFER MEASUREMENTS AT THE WALL OF AN AGITATED VESSEL

The Temperature Oscillation Infra-Red Thermography (TOIRT) was used to measure convective heat transfer coefficients at the inner vertical wall of an agitated and baffled vessel. Two impellers were used: an axial six-blade impeller with pitched blades and the Rushton turbine. The TOIRT method represents an indirect method based on measuring the phase shift between the oscillating heat flux applied to one side of the heat transfer surface and the wall temperature response monitored by a contactless infra-red camera at the same side. On the basis of this phase shift, the TOIRT method can indirectly evaluate the heat transfer coefficient on the other side of the heat transfer surface. Two forms of experimental results are presented in this paper. The first one describes graphical dependencies of the local Nusselt number on the dimensionless distance from the vessel bottom for various Reynolds numbers. The second form describes the mean Nusselt number along the wall as a function of the Reynolds number.

Numerical Investigation of Periodic Fluctuations in Energy Efficiency in Centrifugal Pumps at Different Working Points

In order to simulate the energy efficiency fluctuation behavior of an industrial centrifugal pump with a six-blade impeller, a full-scale three-dimensional (3D) an unsteady state computational fluid dynamics (CFD) model was used. Five operational points with different flow fluxes were numerically investigated by using the Navier–Stokes code with shear-stress transport (SST) k-ω turbulence model. The predicted performance curves agreed well with the test data. A sine function was fitted to the transient calculation results and the results show that the efficiency fluctuates mainly on the blade passing frequency, while the fluctuation level varies with flow rate. Furthermore, high efficiency is not necessarily associated with low fluctuation level. The efficiency fluctuation level is high at part-load points, and becomes relatively low when flow rate exceeds the design value. The effect of change in torque is greater than that of the head lift with respect to fluctuations of efficiency. Based upon the analysis of velocity vector distribution of different impeller phase positions, a hypothesis which considers both the effect of pump’s structural shape and flow fluxes was proposed to explain the above behavior by analyzing the impeller–tongue interaction. This work enriches the theoretical system of flow parameters fluctuation of centrifugal pump, and provides useful insight for the optimal design of centrifugal pumps.

Large eddy simulation of a pitched blade impeller mixed vessel – Comparison with LDA measurements

This study deals with a large eddy simulation (LES) of the single-phase turbulent flow in a fully baffled mixed vessel stirred by a pitched six-blade impeller. The ANSYS FLUENT 15.7 commercial CFD programme was employed. The LES turbulent model is used with the dynamic Smagorinsky–Lilly model. The Werner–Wengle wall function is used to cope with the requirements of near the wall cell size of the LES model. The sliding mesh (SM) model was used for simulating the impeller movement. The results of the simulations are compared with experimental data obtained by previous LDA measurements of the radial profiles of the axial component of the ensemble averaged mean velocity in the impeller discharge flow. The volume flow rates and the flow rate criteria were calculated from these velocity profiles, and were compared with the flow rates determined from the horizontal vessel cross section from simulation.

Flow Evaluation and Hemolysis Analysis of BVAD Centrifugal Blood Pump by Computational Fluids Dynamics

Computational fluid dynamics (CFD) and particle image velocimetry (PIV) are commonly used techniques to evaluate the flow characteristics in the development stage of blood pumps. CFD technique allows rapid change to pump parameters to optimize the pump performance without having to construct a costly prototype model. These techniques are used in the construction of a bi-ventricular assist device (BVAD) which combines the functions of LVAD and RVAD in a compact unit. The BVAD construction consists of two separate chambers with similar impellers, volutes, inlet and output sections. To achieve the required flow characteristics of an average flow rate of 5 l/min and different pressure heads (left - 100mmHg and right - 20mmHg), the impellers were set at different rotating speeds. From the CFD results, a six-blade impeller design was adopted for the development of the BVAD. It was also observed that the fluid can flow smoothly through the pump with minimum shear stress and area of stagnation which are related to haemolysis and thrombosis. Based on the compatible Reynolds number the flow through the model was calculated for the left and the right pumps. As it was not possible to have both the left and right chambers in the experimental model, the left and right pumps were tested separately.

An optimization study on the cementation of silver with copper in nitrate solutions by Taguchi design

Silver cementation from nitrate containing solution using Taguchi methods was studied to understand and optimize silver cementation yield by considering design and rotation rate of the impeller, temperature and pH of the solution. In the experiments, 2, 4 and 6 blade impellers and 100, 200 and 300 RPM rotation rates were used. The solution pH values were selected as 0.5, 1.5, and 2.5, and the experiments were conducted at 30, 45 and 60 °C. The maximum silver recovery conditions were obtained when six-bladed impeller was rotated at a rate of 200 RPM in a solution pH of 0.5 at 30 °C. The silver cementation yields obtained by theoretically and experimentally were in good agreement, which were 99.1% and 99.2% respectively.

Comparison of mean drop sizes and drop size distributions in agitated liquid–liquid dispersions produced by disk and open type impellers

Abstract A comparison is made of drop diameters produced by a disk and an open type six-blade impeller having the same impeller diameter and width and rotated at the same speed. Drop size measurements in situ at 200, 250, 300, 350, 400 and 450 rpm and at hold-up fractions 0.01, 0.025, 0.05 and 0.10 showed that always the Sauter mean drop diameters produced by the open style impeller were 6–82% larger than the ones produced by the disk impeller. Plots of ln d 32 versus ln N and ln d max versus ln N gave straight lines. Plots of d 32 versus d max gave relationships not quite linear.

Electrostatic charge generation during impeller mixing of used transformer oil

The purpose of this study was to examine the effects of varying conductivity and turbulent impeller mixing intensity on charge generation of used Shell Diala ® transformer oil. The oil was mechanically agitated by a pitched six-bladed impeller in a 1.5 quart fully baffled cylindrical vessel at impeller Reynolds numbers between 5 000 and 10 000. The electrical current generated from the mixing operation was measured on the wall of the mixing tank and also in the internal vapor space on a 1 cm 2 target disk positioned approximately 1.5″ above the free liquid surface. Fluid electrical conductivity was varied using different concentrations of two types of commercially available antistatic additives (Shell ASA-3 and DuPont Stadis 450). A generalized dimensional analysis performed by using the Buckingham Pi theorem showed that a dependent dimensionless group, π 1, which contains the measured wall current and other fluid dynamic and electrical variables was found to be dependent on six independent groups. Four of these groups were related to modified Reynolds numbers based on impeller diameter and width, and tank diameter and fluid depth or tank height. The two remaining independent groups were related to the mass transfer Schmidt number and the impeller rotational speed. The mean particle diameter from a Malvern ZetaSizer and π 1 were plotted versus fluid conductivity to investigate the functional dependence of these parameters. The dimensionless group π 1 was also plotted for different impeller Reynolds numbers. These different plots show results that appear to illustrate inverse dependencies. The current versus conductivity data for different impeller Reynolds numbers also show similar behavior to published data for both laminar and turbulent flow through capillaries (i.e., current first increases with increasing conductivity, hits a maximum and then decreases with further increases in conductivity). This apparently demonstrates that a single charge transport mechanism is responsible for the behavior in two different charge-generation situations for different geometrical conditions.

CONSTRUCTION AND OPERATION OF AN IMPELLER RHEOMETER FOR ON-LINE RHEOLOGICAL CHARACTERIZATION OF NON-NEWTONIAN FERMENTATION BROTHS

The present work describes the development and operation of a continuous rotational impeller rheometer for on-line rheological measurements in fermentation broths. In an initial step three devices were calibrated, two of them utilizing helical ribbon impellers and the third a six-bladed impeller. The calibration constants obtained were within the range mentioned in the literature, showing consistency with the methodology employed. In the sequence, the system with one of the helical ribbon impellers (HR39) was selected for on-line continuous rheological measurements due to its small dimensions and its wide measurement range. Finally, the performance of the proposed device, in terms of rheological measurements in Aspergillus awamori broths, was compared to that of a commercial bench rheometer. The comparison of on-line and off-line rheological measurements showed a good agreement between both measurement techniques. Furthermore, results suggest that the proposed on-line rheometer features higher sensitivity and easier operation than the commercial rheometer

Rheological behavior of fermentation broths in antibiotic industry

An experimental study of rheological behavior of three morphological types of fermentation broths in relation to process conditions was carried out in industrial and pilot-plant bioreactors. Three industrially manufactured antibiotic broths were studied: Cephalosporin C (fungal), tylosin (actinomycetic), and apramycin (proactinomycetic), in which the rheology may cause real problems. A viscometer with coaxial cylinders and six-blade impeller was used for rheological measurements. The shear rates range in which both the instruments give similar results was determined. During the experiments rheological and morphological behavior, pH, activity, biomass concentration, fats, glucose, and nitrogen concentrations were studied. All the broths studied exhibited nonNewtonian behavior, which could be described with Ostvald-de-Waele power-law model. It was found that the rheological behavior of the broths during the process is closely related to biomass concentration and morphological changes of mycelia, so that viscosity could be used as a parameter for process monitoring and regulation. A set of experiments on oxygentransfer improvement in the case of the most viscous tylosin broths by water addition was also done.

An experimental investigation of enzyme release from poly(vinyl alcohol) crosslinked microspheres.

Crosslinked poly(vinyl alcohol) particles were prepared by the addition of glutaraldehyde into a PVA methanol/water solution in the presence of 0.2 N sulphuric acid. The polymer solution was dispersed in mineral oil in a jacketed vessel, with the aid of a six-blade impeller. Spherical crosslinked particles in the size range 30-80 microns were obtained by varying the degree of agitation or/and the amount of suspending agent. The crosslinked particles, after washing and drying, were placed into a protease enzyme solution for loading. The enzyme-containing water-swollen particles were subsequently removed from the solution and the enzyme release kinetics determined by a UV spectrophotometer. The influence of the degree of crosslinking, ionic strength, pH, particle size, and degree of hydrophilicity of the polymer on the enzyme activity was retained during the adsorption-desorption studies. The release behaviour of enzymes from crosslinked PVA particles exhibited a biphasic kinetic model, with an initial fast release followed by a much slower release rate.

Design and Performance of a Horizontal, Axial-Flow Water Circulator

An axial-flow water circulator was developed for use in channel catfish, Ictalurus punctatus, culture ponds. The circulator design incorporated a series of 0.76-m diameter fan blades housed within a belled inlet duct 0.92 m in diameter and 1.22 m in length. Power was provided by a 2.24-kW gear motor. Power demand and discharge rates were established using all combinations of the following design variables: impeller type-three blades set at 30' angle or six blades set at 25' angle; impeller speed-90, 120, 144, and 180 rpm; number of impellers in series-1, 2, 3, or 4. The highest discharge rate of 63 m3/minute was established using four six-blade impellers operating at 144 rpm. A maximum discharge rate per unit of power input (efficiency) of 91.4 m3/minute-kW was obtained using two three-blade impellers operating at 90 rpm. Circulator efficiency decreased with increasing discharge rates as described by the model Y = 12888.8X-1.68315, where Y = m3/minute-kW and X = m3/minute. Field tests conducted in 1.62-ha channel catfish production ponds demonstrated the ability of the circulator to increase water movement in all areas of the ponds and to reduce the frequency and total duration of required emergency aeration by 39.3% and 54.6%, respectively. Net production of channel catfish in ponds outfitted with the water circulator (6,683 kg/ha, n = 3) was not different (P > 0.05) than production in control ponds (6,205 kg/ha, n = 3).

Analytical description of the solid phase particle distribution in a mechanically agitated system

A mathematical model of the solid particle random motion in a turbulent liquid flow was developed which resulted in an unconventional form of diffusion equation. The diffusion equation derived describes quantitatively the local extremes of the solid phase concentrations in the charge mixed which were verified experimentally. The comparison of the experimental and calculated distribution of local concentrations in the system shows an adequate qualitative agreement. The system consisted of a cylindrical conical-bottomed vessel with baffles and cylindrical draft-tube. A six-blade impeller with inclined (at α = 45° plane blades was used for agitating.