Purging / Inerting: Oper. Conds Tab

Variable Definitions, Ranges and Default Values

The following table shows a brief description of the variables appearing in this tab. The table also displays their default values and their generally acceptable range. Note that due to how the variables are used in the modeling equations, the range of acceptable values may be further reduced; for more details, see Purging / Inerting: Modeling Assumptions & Constraints.

Variable	Default Value	Range

○ Purging Gas Indicates the gaseous stock mixture or pure component that is selected as the purging gas. Click on the list box to bring up a list of registered stock mixtures or pure components in order to select one.	<none>	Any Gaseous Stock Mixture or Pure Component
○ Supply Temp. (^oC) The temperature of the purging gas in the vessel.	25.0	Positive
● Volume Consumption (L) The volume of purging gas that is consumed for the operation (per cycle, per equipment unit).	0.0	Positive
● Mass Consumption (kg) The mass of pressurization gas that is consumed for the operation (per cycle, per equipment unit).	0.0	Positive
● Initial System Pressure (bar) The pressure of the vessel at the start of the operation.	1.01325	Positive
○ Low System Pressure (bar) The low pressure of the vessel upon evacuation during a vacuum purge or a vacuum and pressure purge.	0.500	Positive
○ Vacuum Pump Indicates the name of the engaged vacuum pump (a type of auxiliary equipment). Click on the list box to bring up a list of available vacuum pumps in order to select one.	<none>	Any Vacuum Pump
○ Vacuum Pump Power (kW) The power consumption of the engaged vacuum pump.	0.0	Positive
○ High System Pressure (bar) The pressure of the vessel upon pressurization during a pressure purge or vacuum and pressure purge.	1.5	Positive
○ Final System Pressure (bar) The pressure of the vessel at the end of this operation.	1.013	Positive
○ Setup Time (min) The amount of time (per cycle) spent before each operation is carried in preparation for the actual execution of the operation. It may involve actions like cleaning, vacuuming, setting up of equipment, etc. which the user opted not to model explicitly.	0.0	Positive
○ Number of Purge Steps The number of times that the purging cycle is repeated.	1	Positive
○ Purging Time Per Step (min) The actual duration of the operation per purging step.	360.0	Positive

Symbol Key: ○ User-specified value (always input); ● Calculated value (always output); ◙ Sometimes input, sometimes output

Specification Choices / Comments

The following list describes the available specification choices in this tab.

•If Pressure purge is selected...

In the case of pressure purge, pressure is first applied with an inert gas to increase the system’s pressure from ‘initial’ to ‘high’, and then venting is applied to reduce the system’s pressure from ‘high’ to ‘final’. This cycle can be repeated several times (the number is specified by the user).

•If Vacuum purge is selected...

In the case of vacuum purge, first a vacuum is produced by means of a vacuum pump to reduce the pressure in the vessel from ‘initial’ to ‘low’, and then the vessel is filled with inert gas up to a ‘final’ pressure. This cycle can be repeated several times (the number is specified by the user).

•If Vacuum and Pressure purge is selected...

In the case of vacuum and pressure purge, first a vacuum is produced by means of a vacuum pump to reduce the pressure of the vessel from ‘initial’ to ‘low’, then the vessel is filled with inert gas until a ‘high’ pressure is reacheed, and then venting is applied to reduce the system’s pressure from ‘high’ to ‘final’. This cycle can be repeated several times (the number is specified by the user).

•Vacuum Pump Controls...

Note that the vacuum pump controls are only displayed if the operating pressure is less than the ambient pressure (specified through the flowsheet’s Reference Conditions dialog).

Click on the vacuum pump list box to bring up a list of available vacuum pumps in order to select one, or select “(none)” (default) if equipment sizing, costing and scheduling calculations are not important.

To create a new vacuum pump and add it to the list of available vacuum pumps, click on the New button (). This will open the Auxiliary Equipment Properties dialog for auxiliary equipment of the vacuum pump type (see Auxiliary Equipment Properties Dialog: Aux. Equipment tab (Vacuum Pump)). Through this dialog, you can view or edit the properties of the auxiliary equipment resource (e.g., name, size, purchase cost, consumables, scheduling).

The same dialog is displayed if you select one of the available vacuum pumps from the list and click on the View/Edit Properties button ().

Click on the Setup button to display the Vacuum Pump Consumption dialog (see Vacuum Pump Power Consumption Dialog), and select different options for specifying the power consumption of the vacuum pump. By default, the vacuum pump power specification option is “Set Total Power” and the total power consumption of the vacuum pump can be set by the user (the default value is zero). For more information, see Vacuum Pump Auxiliary Equipment Calculations.