CFD-Based and Experimental Hydrodynamic Characterization of the Single-Use Bioreactor XcellerexTM XDR-10

Understanding the hydrodynamic conditions in bioreactors is of utmost importance for the selection of operating conditions during cell culture process development. In the present study, the two-phase flow in the lab-scale single-use bioreactor XcellerexTM XDR-10 is characterized for working volumes from 4.5 L to 10 L, impeller speeds from 40 rpm to 360 rpm, and sparging with two different microporous spargers at rates from 0.02 L min−1 to 0.5 L min−1. The numerical simulations are performed with the one-way coupled Euler–Lagrange and the Euler–Euler models. The results of the agitated liquid height, the mixing time, and the volumetric oxygen mass transfer coefficient are compared to experiments. For the unbaffled XDR-10, strong surface vortex formation is found for the maximum impeller speed. To support the selection of suitable impeller speeds for cell cultivation, the surface vortex formation, the average turbulence energy dissipation rate, the hydrodynamic stress, and the mixing time are analyzed and discussed. Surface vortex formation is observed for the maximum impeller speed. Mixing times are below 30 s across all conditions, and volumetric oxygen mass transfer coefficients of up to 22.1 h−1 are found. The XDR-10 provides hydrodynamic conditions which are well suited for the cultivation of animal cells, despite the unusual design of a single bottom-mounted impeller and an unbaffled cultivation bioreactor.

Enhanced Separation of Oil and Solids in Oily Sludge by Froth Flotation at Normal Temperature

Oily sludge (OS) contains a large number of hazardous materials, and froth flotation can achieve oil recovery and non-hazardous disposal of OS simultaneously. The influence of flotation parameters on OS treatment and the flotation mechanism were studied. OS samples were taken from Shengli Oilfield in May 2017 (OSS) and May 2020 (OST), respectively. Results showed that Na2SiO3 was the suitable flotation reagent treating OSS and OST, which could reduce the viscosity between oil and solids. Increasing flotation time, impeller speed and the ratio of liquid to OS could enhance the pulp shear effect, facilitate the formation of bubble and reduce pulp viscosity, respectively. Under the optimized parameters, the oil content of OST residue could be reduced to 1.2%, and that of OSS could be reduced to 0.6% because of OSS with low heavy oil components and wide solid particle size distribution. Orthogonal experimental results showed that the impeller speed was the most significant factor of all parameters for OSS and OST, and it could produce shear force to decrease the intensity of C-H bonds and destabilize the OS. The oil content of residue could be reduced effectively in the temperature range of 24–45 °C under the action of high impeller speed.

Systematic Study of the Effects of High Shear Granulation Parameters on Process Yield, Granule Size, and Shape by Dynamic Image Analysis

The aim of the work was to analyze the influence of process parameters of high shear granulation on the process yield and on the morphology of granules on the basis of dynamic image analysis. The amount of added granulation liquid had a significant effect on all monitored granulometric parameters and caused significant changes in the yield of the process. In regard of the shape, the most spherical granules with the smoothest surface were formed at a liquid to solid ratio of ≈1. The smallest granules were formed at an impeller speed of 700 rpm, but the granules formed at 500 rpm showed both the most desirable shape and the highest process yield. Variation in the shape factors relied not only on the process parameters, but also on the area equivalent diameter of the individual granules in the batch. A linear relationship was found between the amount of granulation liquid and the compressibility of the granules. Using response surface methodology, models for predicting the size of granules and process yield related to the amount of added liquid and the impeller speed were generated, on the basis of which the size of granules and yield can be determined with great accuracy.

Using electrical resistance tomography to characterize and optimize the mixing of micron sized polymeric particles in a slurry reactor

A solid-liquid mixing system has a significant role in the suspension polymerization, crystallization, adsorption, and solid-catalyzed reactions. In this study, Electrical Resistance Tomography (ERT) was employed to investigate the effect of the particle size, the design parameters such as impeller type, impeller clearance and impeller diameter as well as operating conditions such as impeller speed, impeller pumping mode, and solids concentration on the mixing of micron sized latex particles in a slurry reactor. The ERT data were used to calculate the concentration profile and the degree of homogeneity in three dimensions, as a function of design parameters and operating within the reactor. In this work, tap water and latex particles (5.2 µm, 8.5 µm, 9.1 µm) were used as liquid and solid phase, respectively. Six axial impellers were utilized (A310, A100, A200, A320, A315, 3AM) with impeller speed (N) varying from 252 rpm to 400 rpm. Impeller diameter to tank diameter ratios (D/T) were in the range of 0.29 to 0.47 while, the impeller clearance (C/T) was changed in the range of T/3.8 to T/2.5. Impeller pumping was tested in both downward and upward directions. The concentration of latex particles was ranged between 15 wt% and 30 wt%. This study shows that the level of homogeneity in a solid-liquid mixing system improved with the increase in impeller speed. However, after achieving the maximum level of homogeneity, any further rise in the impeller speed had a detrimental effect on the level of homogeneity. A310 impeller, wtih D/T ratio of 0.31, demonstrated the highest level of homogeneity while the upward pumping direction was found to be more efficient than the downward one. In addition, a clearance of T/3 proved to create the highest level of homogeneity. Also, the results showed that a rise in the size and concentration of particles decreases the level of homogeneity. Thus, 5.2 µm latex particles with the concentration of 15 wt% demonstrated the highest level of homogeneity. Applying the findings of this study will lead to improved equipment design, chemical cost reduction, increased production rate, improved quality of products, and more efficient use of power in slurry reactors.

Using electrical resistance tomography to characterize and optimize the mixing of micron sized polymeric particles in a slurry reactor

A solid-liquid mixing system has a significant role in the suspension polymerization, crystallization, adsorption, and solid-catalyzed reactions. In this study, Electrical Resistance Tomography (ERT) was employed to investigate the effect of the particle size, the design parameters such as impeller type, impeller clearance and impeller diameter as well as operating conditions such as impeller speed, impeller pumping mode, and solids concentration on the mixing of micron sized latex particles in a slurry reactor. The ERT data were used to calculate the concentration profile and the degree of homogeneity in three dimensions, as a function of design parameters and operating within the reactor. In this work, tap water and latex particles (5.2 µm, 8.5 µm, 9.1 µm) were used as liquid and solid phase, respectively. Six axial impellers were utilized (A310, A100, A200, A320, A315, 3AM) with impeller speed (N) varying from 252 rpm to 400 rpm. Impeller diameter to tank diameter ratios (D/T) were in the range of 0.29 to 0.47 while, the impeller clearance (C/T) was changed in the range of T/3.8 to T/2.5. Impeller pumping was tested in both downward and upward directions. The concentration of latex particles was ranged between 15 wt% and 30 wt%. This study shows that the level of homogeneity in a solid-liquid mixing system improved with the increase in impeller speed. However, after achieving the maximum level of homogeneity, any further rise in the impeller speed had a detrimental effect on the level of homogeneity. A310 impeller, wtih D/T ratio of 0.31, demonstrated the highest level of homogeneity while the upward pumping direction was found to be more efficient than the downward one. In addition, a clearance of T/3 proved to create the highest level of homogeneity. Also, the results showed that a rise in the size and concentration of particles decreases the level of homogeneity. Thus, 5.2 µm latex particles with the concentration of 15 wt% demonstrated the highest level of homogeneity. Applying the findings of this study will lead to improved equipment design, chemical cost reduction, increased production rate, improved quality of products, and more efficient use of power in slurry reactors.

Dynamic & CFD modeling of a continuous-flow mixer using fluids with yield stress

A continuous-flow mixer was designed and built in the Mixing Technology Lab, Chemical Engineering Department at Ryerson University to study mixing of xanthan gum solutions in water, a pseudoplastic fluid possessing yield stress. The extent of flow non-ideality was quantified using a dynamic model that incorporated the extent of channeling and the effective mixed volume within the mixing vessel. Dynamic tests were made using a frequency-modulated random binary input of a brine solution. The same experiments were simulated using Fluent, a Computational Fluid Dynamics (CFD) package. CFD flow fields were used to obtain the system dynamic response to a tracer injection applied at conditions indentical to the experimental conditions. The extent of channeling and effective mixed volume were determined and then compared with the parameters obtained experimentally. Experimental and CFD results show that the extent of non-ideal flow is significantly affected by impeller speed, impeller type, feed flow rate, fluid rheology, and exit location. The performance of continuous mixed vessels can be improved by increasing impeller speed, decreasing feed flow rate, and decreasing solution concentration. However, decreasing feed flow rate and solution concentration reduces the production capacity of the process. Increasing impeller speed may require modification to the motor and can cause air entrainment. Therefore, other remedies such as relocating the exit location and using the proper type of impeller may be taken into consideration. The results show that the extent of non-ideal flow was reduced using the bottom output and flow efficiency in the vessel was enhanced using A320 impeller.

Solid-Liquid Mixing In Agitated Tanks : Experimental And CFD Analysis

Solid-liquid mixing plays a significant role in crystallization, suspension polymerization, leaching, solid-catalyzed reaction and adsorption. In this study, a computational fluid dynamic (CFD) model was developed for solid-liquid mixing in a cylindrical tank equipped with a top-entering impeller. The multiple reference frame (MRF) technique, k-ε model and Eulerian-Eulerian approach were employed to simulate the impeller rotation, turbulent flow and multiphase flow, respectively. The effects of impeller speed, solid concentration, particle size, solid density and impeller clearance on the mixing performance of four different impellers (A310, marine propeller, pitched blad turbine and A320) were investigated. The CFD results were in good agreement with experimental data measured using electrical resistance tomography (ERT). In order to investigate the mixing quality in this study, the impeller speed required for maximum homogeneity, clouding height, and just-suspended impeller speed were investigated.

Dynamic & CFD modeling of a continuous-flow mixer using fluids with yield stress

A continuous-flow mixer was designed and built in the Mixing Technology Lab, Chemical Engineering Department at Ryerson University to study mixing of xanthan gum solutions in water, a pseudoplastic fluid possessing yield stress. The extent of flow non-ideality was quantified using a dynamic model that incorporated the extent of channeling and the effective mixed volume within the mixing vessel. Dynamic tests were made using a frequency-modulated random binary input of a brine solution. The same experiments were simulated using Fluent, a Computational Fluid Dynamics (CFD) package. CFD flow fields were used to obtain the system dynamic response to a tracer injection applied at conditions indentical to the experimental conditions. The extent of channeling and effective mixed volume were determined and then compared with the parameters obtained experimentally. Experimental and CFD results show that the extent of non-ideal flow is significantly affected by impeller speed, impeller type, feed flow rate, fluid rheology, and exit location. The performance of continuous mixed vessels can be improved by increasing impeller speed, decreasing feed flow rate, and decreasing solution concentration. However, decreasing feed flow rate and solution concentration reduces the production capacity of the process. Increasing impeller speed may require modification to the motor and can cause air entrainment. Therefore, other remedies such as relocating the exit location and using the proper type of impeller may be taken into consideration. The results show that the extent of non-ideal flow was reduced using the bottom output and flow efficiency in the vessel was enhanced using A320 impeller.

Solid-Liquid Mixing In Agitated Tanks : Experimental And CFD Analysis

Solid-liquid mixing plays a significant role in crystallization, suspension polymerization, leaching, solid-catalyzed reaction and adsorption. In this study, a computational fluid dynamic (CFD) model was developed for solid-liquid mixing in a cylindrical tank equipped with a top-entering impeller. The multiple reference frame (MRF) technique, k-ε model and Eulerian-Eulerian approach were employed to simulate the impeller rotation, turbulent flow and multiphase flow, respectively. The effects of impeller speed, solid concentration, particle size, solid density and impeller clearance on the mixing performance of four different impellers (A310, marine propeller, pitched blad turbine and A320) were investigated. The CFD results were in good agreement with experimental data measured using electrical resistance tomography (ERT). In order to investigate the mixing quality in this study, the impeller speed required for maximum homogeneity, clouding height, and just-suspended impeller speed were investigated.

Experimental and CFD investigation of the mixing of MMA emulsion polymerization in a stirred tank reactor

Although significant advances have been achieved in emulsion polymerization in recent decades, the effect of mixing on this type of polymerization has not been fully delineated yet. In fact, mixing plays a significant role in the performance of an emulsion polymerization reaction. For instance, in case of a very low agitation rate, larger droplets are generated and phase separation, which limits the diffusion mechanism, may occur. In contrast, vigorous agitation can result in reduced nucleation of particles. Therefore, the main objective of this study is to investigate the impact of mixing parameters (e.g. impeller speed, impeller type, impeller number, and baffles) on the monomer conversion, the polymer average molecular weight, particle size and size distributions, transition glass temperature, and number of particles. To achieve this objective, the emulsion polymerization of methyl methacrylate (MMA) was carried out in a lab-scale reactor equipped with a top-entry agitator, 4 wall baffles, a U shaped cooling coil, and a temperature controller. To analyze the reactive flow inside the polymerization reactor, a novel computational fluid dynamics (CFD) model was developed. The multiple reference frames (MRF) technique, k-ε model, and mixture model approach were employed to model the impeller rotation, turbulence, and multiphase flow, respectively. The particle number density distribution within the reactor was also estimated by means of the population balance approach, which employs a discrete method to describe the nucleation and growth of the polymer particles. The experimental data and CFD results showed that the installation of the baffles enhanced the particle size and molecular weight but reduced the conversion and particle number. The number density achieved using the Rushton impeller was higher than that for the pitched blade impeller. The results revealed that the effect of the impeller speed on the characteristics of the polymer attained using the pitched-blade turbine was more prominent than that for the Rushton turbine. It was also found that the impact of the impeller speed on the polymer characteristics was much more pronounced for the double pitched-blade turbines rather than for the double Rushton turbines.