Disc Stack Centrifuge Research Articles

Numerical Study of Internal Flow Field in a Disc Stack Centrifuge Based on Mixture-PBM Model

Disc stack centrifuge belongs to one kind of sedimentation centrifuge, widely used in the environmental protection, pharmacy, and chemical industries, etc. The flow process inside the disc stack centrifuge seriously affects the separation efficiency. However, the flow process inside the disc stack centrifuge and its influence on the separation efficiency have not yet been detailed. We plan to study the flow process of oil and water phases inside the disc stack centrifuge and to explore the process of fragmentation and accumulation of water droplets. In this study, the Mixture-PBM (Population Balance Model) model is used to numerically simulate the two-phase flow of oil and water in the disc stack centrifuge and compare it with the tests. The research found that with the increase in rotational speed, the separation efficiency rises in both the test and numerical simulation results, and the difference between the test and simulation results is below 1%. The effect of ribs on the flow is considered, and the results show that the hysteresis of the liquid flow in the disc stack centrifuge is significantly reduced after considering the ribs, and the numerical simulation results can reach 98% of the theoretical results. Fluid entering the separation channel from the neutral pore creates a vortex, and as the dimensionless number λ increases, the degree of deviation of the fluid’s trajectory from the generatrix increases. The circumferential and radial velocities in the separation channel appear large in the center and small near the wall. The water content in the rising channel gradually decreases, and 90% of the water finishes settling in the distributor. The processing volume of the separation channel in each layer shows a small bottom layer, a large top layer, and a uniform law in the middle. The coalescence of water droplets occurs mainly in the separation channel, as found by analyzing the laws of the internal flow of the disc stack centrifuge, which provides the basis for improving the structure of the disc stack centrifuge, increasing the separation efficiency and reducing the floor space.

Optimization and test study of centripetal pump in disc-stack centrifuge based on flow field analysis

BackgroundDisc-stack centrifuges are widely used in various production areas, and the centripetal pump serves as its energy conversion device, which saves energy. MethodsBased on the condition of constant fluid velocity moment in the flow channel of centripetal pump, redrawn the shape of the flow channel while keeping the height constant, to achieve the improvement of discharge performance. Significant findingsThe optimized centripetal pump has a reasonable static pressure distribution, a wider velocity distribution and a more uniform velocity gradient distribution, and the pressure drop is reduced by 4.8 % compared with the original structure. The performance enhancement of the centripetal pump positively affects the performance of the whole machine. The centrifuge now reaches a higher efficiency (96 %), and can effectively reduce the power consumption, wear, and vibration during operation, which can provide reference for the design and optimization of centripetal pumps of disc-stack centrifuges.

Evaluation of a single-use disk stack centrifuge for improved efficiency and sustainability at 1000 L GMP manufacturing scale.

Direct depth filtration is an established technology for single-use harvest operation. Advantages of direct depth filtration include familiarity with depth filtration in downstream processes and simplicity of the operation. Drawbacks include low capacity, large footprint, labor-intensive set-up, high water use, and high waste in the form of discarded filters. Single-use centrifugation is emerging as an alternative to depth filtration for the single-use harvest step. Within the single-use centrifugation space, disc stack centrifugation represents the newest entrant. In this study, we evaluated the performance of the GEA kytero single-use disc stack centrifuge to clarify two monoclonal antibody-producing cell culture fluids. The separation performance of the GEA kytero centrifuge varied between the two cell culture fluids, with differences in centrate turbidity and centrate filterability measured. A comparison was then performed to determine resource savings, compared to direct two-stage depth filtration, when using a GEA kytero centrifuge to harvest a 1000 L bioreactor. The analysis concluded that replacement of the first stage of depth filters with a GEA kytero centrifuge has the potential to decrease the required second stage depth filtration area by up to 80%. The decrease in depth filter area resulting from the use of the GEA kytero would result in a decrease in the harvest step footprint, a decrease in buffer volume required to prime and rinse depth filters, and a decrease in the volume of plastic waste. An economic comparison of the GEA kytero single-use centrifuge against a direct depth filtration step found that for a 1000 L harvest step, the GEA kytero centrifuge may reduce costs by up to 20% compared with two-stage direct depth filtration.

Cost-efficient cell clarification using an intensified fluidized bed centrifugation platform approach.

The intensification of industrial biopharmaceutical production and the integration of process steps pave the way for patients to access affordable treatments. The predominantly batchwise biomanufacturing of established cell clarification technologies, stainless steel disc stack centrifugation (DSC) and single-use (SU) depth filtration (DF), pose technological and economical bottlenecks, that include low biomass loading capacities and low product recoveries. Therefore, a novel SU-based clarification platform was developed combining fluidized bed centrifugation (FBC) with integrated filtration. The feasibility of this approach was investigated for high cell concentration with more than 100E6 cells/mL. Furthermore, scalability to 200 L bioreactor scale was tested for moderate cell concentrations. In both trials, low harvest turbidities (4 NTU) and superior antibody recoveries (95%) were achieved. The impact on the overall economics of industrial SU biomanufacturing using an up-scaled FBC approach was compared with DSC and DF technologies for different process parameters. As a result, the FBC showed to be the most cost-effective alternative for annual mAb production below 500 kg. In addition, the FBC clarification of increasing cell concentrations was found to have minimal impact on overall process costs, in contrast to established technologies, demonstrating that the FBC approach is particularly suitable for intensified processes.

A novel method for extraction of paramylon from Euglena gracilis for industrial production

For establishing an extraction process of paramylon for industrial production, the process of disrupting and concentrating Euglena gracilis cells by disc stack centrifuge (DSC), and then paramylon was extracted successfully on the pilot scale by the method of sodium dodecyl sulfate (SDS) in this study. The results revealed that the cell disruption rate of 93.44 % could be obtained by disc stack centrifuge. The optimal extraction conditions of paramylon in E. gracilis concentrate were SDS addition of 5.4 g L−1, extraction temperature of 76 °C, single extraction time of 42 min, and the number of extraction times of 2. There was no photosynthetic pigment residue in the extract before washing. Furthermore, washing 3 times could effectively reduce the SDS residue in paramylon. The content of paramylon extracted by the pilot process is >97 %. The extraction yield can reach >92 %. There are no cytochrome and SDS residues in paramylon. The extraction process of paramylon established in this study is convenient, free of organic solvent, and easy to operate and scale up.

White-flesh guava juice clarification by a fixed-angle conical rotor centrifuge laboratory and characterization of continuous disk stack centrifuges

The two objectives of this paper were to determine the effect of centrifugation parameters on guava juice physicochemical characteristics and to identify operational characteristics of continuous disc-stack centrifuges based on the performance of a laboratory centrifuge. Effects of g-force (149 g–3731 g) and centrifugation time (10–40 min) on juice physicochemical characteristics (protein, pectin, galacturonic acid, dry matter, total soluble sugars contents; pH; electrical conductivity, clarity and particle size distribution) were assessed. Laboratory centrifuge performance was evaluated for 1343 g, 2388 g and 3731 g. At 1343 g, separation limits (xmax), feed flow-rates of disc-stack centrifuges and cut-off sizes (x50) were determined for corresponding laboratory centrifuge operation times. Significant decrease in average particle size, protein and pectin contents was observed, contrary to juice clarity. Similar clarification efficiency was obtained for g-forces ≥ 1343 g. xmax were 2669 nm, 2200 nm and 1783 nm, with corresponding x50 for continuous centrifuges, 1887 nm, 1556 nm, 1261 nm, for 20 min, 30 min and 40 min, respectively.

Improvement of disc stack centrifuge design to increase efficiency of formation fluid separation

It should be noted that numerous theoretical studies on flow hydromechanics in the centrifugal field have not been sufficiently used in designing separators with a high productivity index. This is caused by the extreme complexity of the flow conditions of the separated liquid in the intrarotor space. Therefore, experimental studies of intra-rotor flows have now gained great importance. The obtained results of studies carried out on a real product at a pressure and flow rate corresponding to production conditions made it possible to create and manufacture an industrial sample of the assembly. The authors use experimental data to calculate similar hydrocyclones ment for operation with other mixtures.

Fluidized bed centrifugation of precipitated and flocculated cell cultures: An intensified clarification approach for monoclonal antibodies

Precipitation and flocculation pretreatments promise improved clarification of cell culture fluids (CCF) to intensify the production of monoclonal antibodies (mAb). However, such pretreatments pose the risks to alter the mAb and damage cells. This can be additionally exacerbated by the subsequent clarification process, for example by high shear forces during disk stack centrifugation, resulting in a release of host cell impurities. To overcome these limitations and enhance the clarification particularly of cell cultures with low viability and thus a high level of impurities, this study investigated low-pH precipitation and cationic polymer flocculation, each in combination with a mild fluidized bed centrifuge (FBC) separation and a subsequent filtration step. Therefore, low-viable CCF´s were pretreated and characterized to investigate the effects of additives on CCF composition and stability. In clarification experiments, both pretreatments achieved similar FBC throughput compared to an untreated reference but increased the maximum filter throughput up to four times. Furthermore, high mAb recoveries (> 91%), low turbidities (< 3.1 NTU) and high DNA removals (> 91%) were achieved. Similar glycan profiles and dimer ratios suggest consistent mAb quality. These findings have a great potential to intensify mAb downstream processing with both CCF pretreatments using a FBC clarification approach.

A computational fluid dynamics-discrete element modeling study on flow field and particle sedimentation processes in a disk-stack centrifuge settler

A computational fluid dynamics-discrete element modeling study on flow field and particle sedimentation processes in a disk-stack centrifuge settler

Optimization of industrial-scale centrifugal separation of biological products: comparing the performance of tubular and disc stack centrifuges

It is reported for the first time, the selection of an industrial centrifuge with the optimized geometry and operational conditions to efficiently separate the diphtheria bacterial cell debris from the culture medium and particularly to harvest the purified bacterial toxin by using the computational fluid dynamics (CFD) simulation and experimental approaches. The industrial-scale tubular and disc stack centrifuges each with two different sizes were first simulated to quantify their complex hydrodynamics. An optimal balance among the rotational speed, feed flow rate, and possible cell damages was required to efficiently separate the bacterial cells. It was also revealed that both large-sized tubular and disc stack centrifuges perform remarkably better than the smaller ones. Ultimately, according to the CFD simulation results, among four centrifuges, the large-sized disc stack centrifuge with the rotational speeds upper than 5500 rpm and the feed flow rates lower than 100 L h−1 was a potential candidate to utilize in the real process. Through performing experiments by using an industrial disc stack centrifuge, a good agreement was found between the CFD and experimental data in terms of the optimized rotational speed and feed flow rate required for the separation of cells. The Ramon flocculation assay confirmed the preserved quality and quantity of the main product of this bioseparation process, ‘the bacterial toxin purified from the bacterial cell debris’.

Lipid reduction to improve clarification and filterability during primary recovery of intracellular products in yeast lysates using exogenous lipase

AbstractBACKGROUNDThe yeast Pichia pastoris is a popular host organism for production of a range of biological products, several of which are intracellular. The disruption of yeast cells by homogenization also releases large quantities of lipids, which can foul the downstream membranes and chromatography matrices used for purification. This work examines lipid removal from yeast cells following homogenization by enzymatic degradation and its impact on the performance of the subsequent centrifugation and filtration.RESULTSLipase treatment of cell homogenate at 37 °C for 2 h, followed by clarification using a scaled‐down mimic of disc stack centrifugation, resulted in a 6.5‐fold improvement in solids removal when compared to untreated feed material. The lipase‐treated and untreated materials that had undergone initial centrifugation were then tested for filtration performance by passing the material through a 0.45 μm polyethylene sulfone membrane under constant flux. A 50% increase in throughput was observed in comparison to the untreated material.CONCLUSIONThese proof‐of‐concept data suggest enzymatic digestion of lipids, analogous to the widely performed DNA reduction using nucleases, could be a valuable process improvement strategy. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry (SCI).

Centrifugal Separation in the Treatment of Produced Water for its Subsequent Injection into a Reservoir

The present article covers the results of theoretical and experimental studies into the purification of produced water (wastewater) by means of centrifugal separation technology using a disk stack centrifuge. When produced water obtained during crude oil treatment is reinjected to maintain reservoir pressure, it is necessary to reduce the content of mechanical particles and oil in this water. For these purposes, the centrifugal technology of water purification enabling the removal of suspended solids and oil particles can be more effective than gravitational settling.

Optimization of mechanical harvesting of microalgae by centrifugation for biofuels production

This study aims to minimize the energy consumption of the disc-stack centrifuge by optimizing the factors that affect its consumption using response surface methodology. Eight factors with the potential to affect the energy consumption of the centrifuge were identified. A 3k factorial Box-Behnken design was used as the design model to investigate the chosen factors using Minitab software. The result indicates that the main three factors that have the largest impact on the energy consumption of the centrifuge are the particle size, the rotational speed, and the outer radius of the centrifuge, respectively. Moreover, the results demonstrate that the energy consumption of the centrifuge can be reduced from 1 kWh/m3 to 0.1 kWh/m3 achieving a 90% reduction in total. In order to achieve such a low consumption, the outer radius and the rotational speed of the disc-stack centrifuge should be designed to not exceed 0.175 m and 3000 rpm, respectively.

A comparison among innovative plants for high quality extra‐virgin olive oil production

The cleaning operation of extra-virgin olive oil (EVOO), subsequent to its extraction, is generally performed by means of a vertical disc stack centrifuge separator causing qualitative damage due to increased oxidative alterations. However, previous works have demonstrated the great opportunity that settling represents in order to improve the EVOO quality performing the separation operation with minimal qualitative damage. A new patented prototype device (ROTASED, RS) has been used in the cleaning operation of extra-virgin olive comparing physical and chemical characterization of EVOO after 48 h from extraction and after 180 days of shelf-life. In addition, the results have been compared with those obtained using an assisted sedimentation (AS) plant and an enhanced sedimentation plant by hydrocyclone (H) from previous authors' works, in order to assess the improvement of EVOO quality that could be attained with respect to the use of the vertical disc stack centrifuge separator. The results show that after 48 h of storage the tested patented prototype device seems to be preferable, however, after 180 days of storage, the difference between H and RS device results similar in terms of improvement of the final olive oil quality. In addition, the method of principal component analysis can be used to evaluate the suitability of an olive cv. in terms of quality of extracted oil. © 2020 Society of Chemical Industry.

Visualization of the deposition mechanisms in disk stack centrifuges with an acrylic glass bowl top and high-speed image processing

ABSTRACT Disk stack separators represent an industrial standard for mechanical separation within a large range of applications. To date, the prediction of separation efficiencies for disk stack separators is largely based on the concept of the equivalent clarification area, namely the Σ-Theory. This theory is based on various simplifying assumptions which lead to inconsistencies with experimental results. The separation process inside the top disk gap of a disk stack centrifuge with a transparent bowl top is visualized using a high-speed camera. The influence of disk geometry parameters on the flow and particle separation is analyzed by image processing and the unused clarification areas are determined. The analysis shows that the ratio of unused clarification area is significant. Abbreviations: GEA: GEA Group AG; PMSQ: Polymethyl silsesquioxane beads; PVAc: Poly(vinyl acetate) beads; rpm: Revolutions per minute; 3D: Three-dimensional

Downstream Processing of Chlamydomonas reinhardtii TN72 for Recombinant Protein Recovery.

The green microalga Chlamydomonas reinhardtii is under development as a production host for recombinant proteins and whole-cell therapeutics. In particular, the cell wall-reduced strain TN72 is used as a model organism for protein expression and algal synthetic biology. However, the bioprocessing characteristics of TN72 and other C. reinhardtii strains have yet to be examined. Here we use a TN72 strain expressing a protein-based antibiotic (Pal) to study the scale-up of cell harvest and product recovery. Cell harvest was examined with 100L cultures in two intermittent-discharge continuous-flow disc-stack centrifuges at flow rates of 150–250 L.h−1, as well as with an ultra scale-down (USD) mimic of the centrifuges. Solids recovery exceeded 99.5% and the loss of product to the supernatant was below 2–3%. TN72 is intact following the high shear conditions of the feed zone, however discharge from both disc-stack centrifuges resulted in full cell breakage and in the case of Pal, partial degradation in the subsequent hours. We demonstrated that shake flask cultivation and the USD centrifuge technique can be used to predict the pilot-scale clarification efficiency and product release at the centrifuge inlet for TN72, but not the cell breakage on discharge. This study outlines a number of challenges for scale-up of recombinant protein production in the microalgal host in particular for whole cell therapeutics, but also opportunities for the bioprocessing of intracellular products from TN72.

Analysis and estimation/prediction of the disk stack centrifuge separation performance – Scaling from benchtop fixed rotor type to disk stack centrifuges

ABSTRACT A mathematical model is proposed to calculate the total separation effectiveness in terms of GT for a disk stack centrifuge taking account of the variation of the centrifugal force with a position in the disk. In practice, the centrifuge ability/force is often referred as Relative Centrifugal Force (RCF) or G number, which is a multiple of the centrifugal acceleration over the gravitational acceleration. As the radial velocity varies it is important to integrate the relative centrifuge force, here in terms of the G number along the path taking account of the change in velocity. The separation effectiveness, GT is defined as an integrated product of local G number, G(x) and local residential time (dt), where dt is the time taken for the bulk fluid to traverse a distance from r to r+ dr. The GT value calculated for a disk type centrifuge can be compared with the GT value of others and compared with a bench top fixed rotor centrifuge. An industrial centrifuge would be expected to be able to deliver similar separation performance to a pilot or a lab scale one, if operated at the same/similar value of GT. This would allow the performance of a full-scale clarifier to be predicted. This model is, in essence, a simple alternative to the Sigma concept.

Sorbitol/methanol mixed induction reduces process impurities and improves centrifugal dewatering in Pichia pastoris culture

This study investigates how sorbitol/methanol mixed induction affects fermentation performance, dewatering characteristics of cells during harvesting and the profile of host cell proteins (HCP) in the process fluid when producing the target recombinant protein aprotinin. Compared to standard methanol induction, sorbitol/methanol (1:1, C-mol/C-mol) mixed induction improved cellular viability from 92.8 ± 0.3% to 97.7 ± 0.1% although resulted in a reduced product yield from 1.65 ± 0.03 g L−1 to 1.12 ± 0.07 g L−1. On the other hand, average oxygen consumption rate (OUR) dropped from 241.4 ± 21.3 mmol L−1 h−1 to 145.5 ± 6.7 mmol L−1 h−1. Cell diameter decreased over time in the mixed induction, resulting in a D50 value of 3.14 μm at harvest compared to 3.85 μm with methanol. The reduction in cell size enhanced the maximum dewatering efficiency from 78.1 ± 3.9% to 84.5 ± 3.3% as evaluated by using an established ultra scale-down methodology that models pilot and industrial scale disc stack centrifugation. Seventy host cell proteins (HCPs) were identified in clarified supernatant when using sorbitol/methanol mixed induction regimen. The total number of HCPs identified with standard methanol induction was nearly one hundred. The downstream process advantage of the mixed induction lies in improved product purity by reducing both cell mortality and level of released whole cell proteins. This needs to be balanced and optimised against the observed reduction in product yield during fermentation.

Flocculant Screening Method at Lab Scale for Application in Disc Stack Centrifuges with Hermetic Design.

Chemicals produced using biotechnological methods like fermentation processes are obtained as complex diluted aqueous mixture, which still contains the production organism. Centrifugation is a commonly used technology for biomass separation. By flocculation, the settling velocity of microorganisms can be increased. Here, a laboratory flocculant screening method tailored for the separation of flocculated biomass in a fully hermetic disc stack centrifuge is described. The specific requirements of this process, namely, floc formation, floc stability, sliding behavior in the disc stack, and flowability of the sludge, were transferred to lab scale and validated in pilot tests. The qualitative results of the laboratory screening were in agreement with the processes at industrial scale.

Rheological Characterization of Solids Phase in Biomass Processes of Disc-Stack Centrifuges.

Rheological characterization of the solids phase in bio‐industry disc‐stack centrifuges is considered. Three discriminatory properties of the solids phase are investigated, namely, the particle settling velocity, the angle of repose, and the solids phase viscosity. The solids phase produced in disc‐stack centrifuges in the food or biopharmaceutical industry possesses both liquid‐like and solid‐like properties which can be quantified by means of these test methods. The resulting rheological characterization can be used for diagnostic purposes in the selection process of industrial centrifuges and for optimization of centrifuge solids handling in biomass processing of suspension systems.