BATCHFRAC Charge Specification

Define charges to the BATCHFRAC unit during its operation. Charges may be instantaneous or continuous. Multiple charges are allowed in any policy segment.

Usage

The BATCHFRAC requires at least one initial charges to the stillpot. No Distill action is allowed until initial charging is complete. The first policy segment in the Overall Operating Policy table of the BATCHFRAC Main Window must contain an initial charge to the unit. Further charges may be added to the unit later in its operation.

The time required for initial charging is not simulated. This means all initial charges are treated as instantaneous, even if specified as continuous.

After the initial charge, a series of Distill actions cause the simulated time to advance. A continuous charge has its own stopping criterion.

Charge Identifier

Each charge identifier may contain up to 12 characters. It identifies the charge in the output reports.

Feed Stream

Select a feed stream to use as the source for the charge. A drop down list of feeds is attached to the unit on the Process Flow Diagram.

Charging Mode

Charges to the stillpot may be instantaneous or continuous. Continuous charges may be fed to any stage in the column excluding the condenser.

You may select the charging mode as:

Instantaneous amount: The specified amount is added instantaneously to the stillpot. Instantaneous charges are assumed to be added before any Distill action in the same policy segment.

At a rate: The charge continues at the specified rate until the end of the policy segment.

Rate over a time period: The charge is fed at the specified rate for the stipulated time period. This is assumed similar to the instantaneous amount with Rate*Time Period giving the total amount fed into the stillpot.

Charge Location

Indicate to which stage the charge is to be fed. An instantaneous charge may feed only to the stillpot. Continuous charges may feed any stage except the condenser (stage one).

To change the dimensional units for entries shown on the screen, depress the UOM button to activate the Unit of Measure Selection Window.

Feed Flash Convention

Single phase feeds are always placed onto the feed tray - liquid feeds enter above the feed tray and vapor feeds enter below it. Two options are provided for handling mixed phase vapor/liquid column feeds. The option which is selected is used for all feeds to the column.

Vapor and Liquid on the Feed Tray

This option is the default. Each feed is placed on the designated feed tray, regardless of the thermal condition of the feed. The liquid portion enters above the feed tray and the vapor portion enters below it.

Flash the feed adiabatically

For this option, each feed is adiabatically separated into liquid and vapor portions. The liquid portion is placed on the designated feed tray and the vapor portion feeds the next higher tray in the column, simulating the flashing which occurs at actual column feed trays. Even if this option is specified, column feeds which are all vapor are placed on the designated feed tray.

How to get to this window

The BATCHFRAC - Charge Specification window is accessed by selecting Charge in the Action/Condition table in the BATCHFRAC - Policy Segment window and then clicking on the linked text under Description.

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