This operation simulates a PBA column loading step in flow-through chromatography where (typically but not necessarily) the target protein flows through and impurities bind to the column. The main objectives of this operation are to estimate the time for flowing through the column, account for retained mass in the column and, if in Design Mode, determine the number and size of columns required.
● Packed Bed Adsorption (PBA) Chromatography Procedure (Detailed) in Flow-Through Mode
In this operation you need to specify the resin’s loading capacity in terms of a key component, or its total binding capacity. The resin’s loading capacity in terms of a key component refers to the maximum mass of that component that can be processed by the resin, divided by the resin (bed) volume. Its value can be measured experimentally. The resin’s total binding capacity refers to the maximum mass of all components (except those ‘ignored in sizing’ as explained below) that can bind to the resin, divided by the resin (bed) volume. Its value can be either measured experimentally or approximated using Scopes' correlation, provided that the molecular weight of the main components is known (Scopes, 1982; p.105, Fig. 5.3).
You also need to specify the retained mass % for each component. This is the percentage of the mass of that component in the feed stream that is retained in the resin. By default, all retained mass is considered bound to the resin. If the total binding capacity is set, and a component’s retained mass is not bound, or that component must not be considered when the total binding capacity is determined, you can instruct the program to ignore that component in sizing calculations by checking the ‘Ignore in Sizing ?’ box next to it.
The required bed volume per cycle, V, can be calculated as:
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Where:
● Q is the volume of material processed by the bed per plant batch time.
● n is the number of cycles per batch.
● k is the total number of components in the feed stream.
● Ci is the concentration of component ‘i’ in the feed stream.
● Fi is the retained % that is assigned to component ‘i’ for equipment sizing purposes; if the loading capacity of a key component is set, then Fi is set to 1.0 for the key component and 0.0 for any other component; if the total binding capacity is set, then there are two possibilities: (a) if the ‘Ignore in Sizing ?’ option is checked, Fi is set to 0.0; (b) if the ‘Ignore in Sizing ?’ option is not checked, Fi is set equal to the specified retained %.
● C is either the key component loading capacity per volume or the total binding capacity per volume depending on which type of resin capacity is specified.
● ODF is the overdesign factor.
When the bed height (L) and the maximum bed (or column) diameter (Dmax) are specified, the bed (or column) diameter is calculated by the following equation:
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If D > Dmax, then multiple columns are assumed in parallel. Similarly, the user may decide to fix the diameter and have the program calculate the height.
The process time can be either set by user or calculated based on loading flowrate and feed volume as follows:
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If the process time is set by user then the above equation is used to calculate the absolute loading flowrate.
In terms of loading flowrate, if the process time is not set, you can specify any one of the following three variables: linear velocity, absolute flowrate, or relative flowrate. The other two variables will be calculated by the program according to the following equations:
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If the process time is set, the above two equations are used to calculate the linear velocity and relative flowrate, respectively.
For each component, a percentage of the corresponding amount in the feed stream equal to the specified retained mass % for that component is retained in the bed. Everything else flows through. If the option ‘Consider Throwaway” is not checked, then all flow-through ends up in the flow-through (top outlet) stream. If this option is checked, then a percentage of the flow-through amount equal to the specified throwaway % for each component exits through the specified throwaway streamand the rest exits through the flow-through stream.
The cost associated with resin replacement is estimated as for all consumables (see Consumables Cost). For resins that last several years, the user may decide to depreciate the first resin fill-in by checking the ‘Is First Resin capitalized’ check box in the equipment consumables tab.
The interface of this operation has the following tabs:
● Oper. Cond’s, see PBA Flow-Through: Oper. Conds Tab
● Throwaway, see PBA Flow-Through: Throwaway 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
