This operation simulates a membrane loading step in load-and-elute chromatography where (typically but not necessarily) the target protein binds to the membrane and impurities flow through. The main objectives of this operation are to determine process time, account for retained mass in the membrane and, if in Design Mode, determine the required number of units (holders/cartridges).
● Membrane Adsorption Procedure in Bind-and-Elute Mode
In this operation you need to specify the membrane’s binding capacity (either per membrane area or per membrane volume). This refers to the maximum mass of all components (except those ‘ignored in sizing’ as explained below) that can bind to the membrane. Its value can be estimated experimentally.
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 membrane. By default, all retained mass is considered bound to the membrane. If a component’s retained mass is not bound, or if that component is not considered when the 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 membrane volume per cycle, V, can be calculated as:
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Where:
● Q is the volume of material processed by the membrane 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 ‘Ignore in Sizing ?’ option is checked, Fi is set to 0.0; if the ‘Ignore in Sizing ?’ option is not checked, Fi is set equal to the specified retained %.
● C is the binding capacity per volume.
● ODF is the overdesign factor.
If V > V0, where V0 is the membrane volume per equipment unit (holder or cartridge), then multiple units operating in parallel are assumed.
The process time can be either set by user or calculated based on loading flowrate and feed volume as follows:
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where the term ‘Feed Volume’ represents the buffer volume in the context of this operation.
If the process time is set by user, then the above equation is used to calculate the absolute loading flowrate.
If the loading time is calculated based on loading flowrate, you can choose among four different options for specifying the loading flowrate: you can specify the feed’s linear velocity, or its volumetric flowrate, or its relative flowrate (in bed volumes) in the bed, or the empty bed contact time (the amount of time it takes for a feed volume of material to flow through an empty bed). Any variable that is not specified will be calculated by the program based on the following relations:
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where the term ‘Bed Volume’ represents the membrane’s volume in the context of this operation.
If the loading time is set by the user, then the program will first calculate the absolute flowrate from eq. (A.166) and then it will calculate the linear velocity, relative flowrate, and empty bed contact time from eq. (A.163), eq. (A.164), and eq. (A.165), 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 membrane. Everything else ends up in the specified outlet (wate) stream.
The cost associated with membrane replacement is estimated as for all consumables (see Consumables Cost). For membranes that last several years, the user may decide to depreciate the first membrane fill-in by checking the ‘Is First Cartridge Capitalized’ check box in the equipment’s Consumables tab.
The interface of this operation has the following tabs:
● Oper. Cond’s, see MA Loading: 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
