Heat Exchanger Stream Attached to a Column

The internal stream of a distillation column can be heated or cooled by exchanging heat with either a process stream or a utility stream using an attached heat exchanger. The stream from a tray in the column can be linked with either side of the exchanger.

The duty of the heater-cooler may be determined by the column, in which case, an exchanger Performance Specification should not appear in the heat exchanger input. Alternatively, the duty may be determined from the specification of the heat exchanger. In this case, the heater-cooler duty in the column cannot be varied to meet a column specification.

Suggestion: Column convergence calculations are considerably enhanced when the column is allowed to calculate the exchanger duty.

Usage

From the Simple Heat Exchanger Main Window push the Attach to Column button for the desired side.

From the Heat Exchanger Hot/Cold Side Attached to Column window:

1. Check the "Use Attached Heat Exchanger" box and select the column unit to which the heat exchanger has to be attached.

2. Select the column attachment type from one of the following choices. The choices available will depend on the attached heat exchanger side and the existing attachments in the selected column.

Condenser : The heat exchanger replaces the column condenser. The hot-side of the exchanger contains the condenser stream, while the cold-side contains either a process stream that gains heat or a cold utility stream like air, water or refrigerant.

( Available only when Cold-side is attached to column ).

Pumparound : The heat exchanger replaces the specified pumparound heater/cooler. The pumparound stream is attached to either the hot or cold side depending on whether the stream gets heated or cooled. Note that the condensers and reboilers modeled in the column with pumparounds (as with a thermosyphon reboiler) should select this attachment type.

Side Heater/ Cooler :

The heat exchanger replaces the specified side heater or cooler. If it is a heater, then the cold-side of the exchanger contains the side heater stream, whereas it will be the hot-side for a side cooler. A process stream or a utility stream flows through the other side.

Reboiler : The heat exchanger replaces the column reboiler. The cold-side of the exchanger contains the reboiler stream, while the hot-side contains a process stream that loses heat or a hot utility stream such as steam.

( Available only when Hot-side is attached to column ) .

3. If a side heater/cooler or pumparound has been selected, you must specify the column tray number to which the unit is attached.

If a side heater or cooler has been selected, you must also specify its feed stream (which will exchange heat) and the flowrate. The feed stream can be one of the following:

vapor of the tray to which the exchanger is attached

liquid of the tray to which the exchanger is attached

vapor from the tray below the attached tray

liquid from the tray above the attached tray

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