eq. (A.131)
The Centritech separation system is a new type of centrifuge, designed to handle animal cells, primarily cell cultures in laboratory and pilot plants. It can be used to concentrate cells and clarify media for purposes such as cell recycling, harvesting, washing, clarification and fractionation. The separation takes place in a presterilized flexible tube. The special design of this unit makes it possible to rotate one end of the flexible tube while the other is standing still, thus avoiding the potential risk of infection of the culture that the need for seals on inlet and outlets represents.
The Centritech centrifuge is available for bench and pilot/small plant scales. The bench and pilot scale units handle throughputs of up to 10 and 100 L/h, respectively.
● Centrifugation in a Centritech Centrifuge Procedure
The material balances are based on the removal percentage of particulate components, and the concentration factor (Feed to Retentate Ratio). More specifically, the removal percentage of particulate components determines the amount of particulate components retained in the concentrate. The concentration factor determines the amount of liquid and soluble components retained in the concentrate.
Design mode of calculation: For continuous operation, the throughput is set equal to the volumetric flowrate of the feed stream. For batch operation, the throughput (Q) is given by the following equation:
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eq. (A.131) |
where Vp is the volume of material processed per batch, Ncycles is the number of cycles per batch, and tp is the process time. If the calculated throughput is less than 10 L/h, a bench scale unit is selected. If it is greater than 10 L/h but lower than 100 L/h, a pilot scale unit is selected. If it is greater than 100 L/h, then, multiple pilot units are assumed operating in parallel so that the throughput of each unit is less than 100 L/h.
Rating mode of calculation: This mode of calculation is used for simulating existing equipment. For a plant operating in batch mode, the primary objective is to calculate the centrifugation (process) time by solving the above equation with respect to process time. For flexibility, the user also has the option to specify the centrifugation time. In that case, the throughput is calculated using the above equation and if it is greater than the maximum, the user is warned.
Built-in values are available for the cost of consumables. The default values that are shown on the i/o dialog window of the Centritech centrifuge apply to the pilot scale unit. The user has the option to modify the unit cost as well as the frequency of replacement.
Pump mode: This mode of centrifugation requires separate pumps for feed (push) and discharge (pull) lines. The supernatant line opens during separation and discharge, leading to highest perfusion rate. This mode is preferred for scale-up operation.
Feed mode: A single pump is used for feed and discharge lines. The supernatant line closes during discharge to improve clearance. It leads to highest discharge clearance for high cell mass concentration.
Valve mode: Only one pump is used for the supernatant line. A pinch valve opens and closes feed and discharge lines separately. Recovered and recycled cells avoid exposure to pump shear stress.
In the current implementation of the Centritech centrifuge model, the modes of operation have no impact on the model. The information is provided to facilitate communication between professionals involved in the scale up and operation of such units.
The interface of this operation has the following tabs:
● Oper. Cond’s, see Centritech Centrifugation: Oper. Conds Tab
● Labor, etc, see Operations Dialog: Labor etc. Tab
● Description, see Operations Dialog: Description Tab
● Batch Sheet, see Operations Dialog: Batch Sheet Tab
● Scheduling, see Operations Dialog: Scheduling Tab