Agitated Tank Operations: Vent/Emissions Tab

AgitatedTankEmissionsSpec.jpg

This tab is part of the simulation data dialog of operations in which emissions are calculated using the Agitated Tanks - Emission Model. These are:

      Continuous Stoichiometric Photobioreaction,

      Kinetic Well-Mixed (WM) Aerobic Bio-Oxidation,

      Stoichiometric Plug-Flow (PF) Aerobic Bio-Oxidation, and

      Kinetic Plug-Flow (PF) Aerobic Bio-Oxidation.

You can access the simulation data dialog of an operation through the Operation Data item of the corresponding unit procedure’s context menu (right-click on the unit procedure icon to bring up its context menu).

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:

Variable

Default Value

Range

 

Venting
Check this box to enable venting of freeboard gases.

Yes

Yes/No

Vent Port / Stream
Indicates the output port that is connected to the venting stream. Click on the list box to bring up a list of available output ports in order to select one.

<none>

Any Output Port

Auto-Tag Stream
Check this box to classify the stream that is connected to the vent port as emissions stream.

Yes

Yes/No

Pressure Control Set At (bar)
The operating pressure of the vessel.

1.013

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

Emitted ?
Check this box to specify that the corresponding pure component is vented.

No

Yes/No

Set by User
Check this box to set the vent percentage of the corresponding pure component.

No

Yes/No

Vent/Emission (%)
The emission percentage of the corresponding component.

0.0

0-100

Oxygen Comp.
Indicates the oxygen component. Click on the list box to bring up a list of available components in order to select one.

<none>

Any Pure Component

Oxygen Mass Transfer Coefficient at 20oC (1/h)
The oxygen mass transfer coefficient at a temperature of 20 oC.

4.0

Positive

Theta
This parameter is used to estimate the oxygen mass transfer coefficient at temperatures other than 20 oC.

1.024

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; for more details on how these are implemented, see Agitated Tanks - Emission Model.

‘Venting’ Option...

If venting is off, free-board gases are not allowed to escape (closed-valve operation), thereby contributing to a pressure increase.

If venting is turned on, free-board gases are vented. The user can select between atmospheric or pressurized vessel operation with a relief valve setting specification.

Venting Operating Mode...

‘Atmospheric’ operation is equivalent to having the release valve open so the pressure inside the vessel is equal to the atmospheric pressure. Operation under this setting allows for gases inside the vessel to escape from the vessel, but also, for atmospheric air to be introduced into the vessel in order to preserve the pressure. For more details on how SuperPro Designer calculates the amount that is vented from an operation, see Vent/Emission Calculations In Batch and Continuous Operations.

The ‘Pressurize Control’ mode allows pressure to build up inside an equipment, until the value of the pressure control / relief valve setting is reached. If more gases are accumulated so the pressure exceeds the pressure control setting, then a portion of it will be vented from the vessel so that the pressure matches the pressure control setting specified. Notice however that, if the pressure is lower than the pressure control setting, no air will be allowed into the vessel.

For continuous operations the venting operating mode is simply another way to specify the pressure of the operation. The pressure specification in this tab will update the respective specification of the Oper. Conds. tab (if applicable) and vice versa. Also notice that the specified pressure will be inherited by the operation’s output stream(s).

Vacuum Pump Controls...

Note that the vacuum pump controls are only displayed if the ‘Venting’ option is checked and the operating mode is set to ‘Pressure Control’ and the pressure control setting is set at a lower pressure than the ambient pressure.

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 (AddNewButton00085.jpg). 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 (ViewEditProperties200086.jpg).

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.

In addition, through the Vacuum Pump Consumption dialog you can also specify a flowrate for leaking air if the operation takes place under vacuum.

‘Emitted ?’ Component Option...

In order for component to included in the vent/emissions calculations the corresponding option must be checked. Components that are 100% in the gas phase will be automatically checked as being emitted.

‘Set by User’ Component Option...

Check this box to set the emission percentage for particulate and other components for which the VOC emission models do not apply or the respective VLE-related component properties can not be specified.

For more information on how and when components are set as ‘Emitted?’, see Adding a Component to the Emitted/Vented List.

Emission Model...

For each VOC component, you may specify the parameters that are used for the calculation of the overall mass transfer coefficient through the Emission Model dialog for that component (see Agitated Tank Operations: Emission Model Dialog). To open this dialog, click on the corresponding row number of a component to select it and then click on the Emission Model button. Note that this button will not be available if the ‘Perform Emission Calculations’ option is not checked, or the ‘Emitted ?’ option of the selected component is not checked, or the ‘Set by User’ option of the selected component is checked.

Oxygen Component...

The oxygen component must be identified if at least for one component emissions are calculated.