Vessel Sizing

Separator Sizing

ProMax can size horizontal or vertical two- or three-phase separators. Correlations used in vessel sizing calculations are based on Svrcek (1993), Monnery (1994), GPSA Engineering Data Book (1998), and Manning (1995).

Vertical Orientation

Vertical separators are usually selected when the vapor/liquid ratio is high or total volume is low. A vertical separator occupies less floor space than a horizontal separator and is often considered when plot space is limited. However, a vertical separator may be larger and more expensive than a horizontal separator for the same gas handling capacity due to the upward flow of gas retarding the falling liquid droplets. In the vertical separator, the fluids enter the vessel striking a diverting baffle which initiates primary separation. Liquid removed by the inlet baffle falls to the bottom of the vessel. The gas moves upward, usually passing through a mist extractor or "demister pad" to remove suspended mist. Liquid removed by the demister pad is coalesced into larger droplets which then fall through the gas to the liquid reservoir in the bottom. The ability to handle liquid slugs is typically obtained by increasing height. Level control is not critical and liquid level can fluctuate several inches without affecting operating efficiency. Mist extractors can significantly reduce the required diameter of vertical separators.

Horizontal Orientation

Horizontal separators are preferred for separating mixtures with a low vapor/liquid ratio or for large volumes of total fluids. Horizontal separators have a much greater gas-liquid interface area than vertical separators, which is useful in degassing solvents and reducing foaming. Increased slug capacity is obtained through shortened retention time and increased liquid level.

Three Phase Separator Sizing

Three phase units can be either vertical or horizontal, although they typically are horizontal. The vertical orientation is only used if there is a large amount of vapor to be separated from a small amount of the light and heavy liquid (< 10-20% by weight).

There are a number of basic horizontal Three Phase Separator configurations. Four typical horizontal configurations are: 1) Interface control, 2) Interface control with boot, 3) Interface control with weir, 4) Bucket and weir. Each of these configurations offers advantages depending on the application. Refer to Monnery and Svrcek 1994 for a detailed discussion of the uses and sizing of various three phase separator configurations. A boot typically is specified when the volume of heavy liquid is not substantial (< 15-20% of total liquid by weight), while a weir is used when the volume is substantial. The bucket and weir type design is used when interface level control may be difficult, such as with heavy oils or when large amounts of an emulsion or a paraffin are present.

Separator Thickness Calculations

The separator thickness calculations apply to both two phase and three phase separators and are based on ASME Boiler and Pressure Vessel Code Section VIII, 2004. The appropriate separator design formulas may also be found in the ASME Code. The effect of static head due to liquid level in the separator is not included in the minimum separator thickness calculations. Thickness calculations are not performed for separators under external pressure. Further, the separator thickness calculations are based only on the pressure of the separator. Additional thickness and material may be required for supports and other fixtures.

Column Sizing and Rating

Distillation columns containing trays, random packing, structured packing, or any combination may be sized or rated in ProMax.
To calculate Column Diameter for trayed columns, specify Fraction Flooding, Tray Spacing, Weir Height, Froth Model, Percent Hole Area, and Fraction Active Area (or Weir Widths depending on the number of passes). To calculate Fraction Flooding for trayed columns, specify the previous parameters substituting Diameter for Fraction Flooding.
To calculate Column Diameter for packed columns, specify Fraction Flooding, System Factor, Packing Type, and Flood Model. To calculate Fraction Flooding for packed columns, specify the previously mentioned parameters substituting Diameter for Fraction Flooding.
Column Hydraulic calculations are performed only for VLE or VLLE columns. Columns with only two liquid phases (LLE Column Type) are not sized or rated.

Tray Parameters

Tray Spacing: This parameter is used in the calculation of Residence Time and in Column sizing.
Fraction Active Area: If this parameter is specified, then Weir Widths are calculated assuming equal flow path lengths. If Weir Widths are specified, Fraction Active Area is calculated and cannot be specified.
Weir Height: This parameter is used in the calculation of Residence Time and in Column sizing.
Number of Passes: Select either 1, 2, 3, or 4 pass trays from the drop-down list.
Froth Model: Select either Bolles-Fair, Colwell, or Stichlmair from the drop-down list.
Froth Gravity: This parameter is a correction term which converts the Froth Height to the equivalent height of clear liquid and accounts for the fact that the aerated liquid is less dense than the clear liquid. The Froth Gravity may be calculated using the Bolles-Fair, Colwell, or Stichlmair models. This parameter is calculated and cannot be set by the user.
Height Over Weir: This parameter is the height of liquid above the top of the weir and is always calculated.
Froth Height: This parameter is the sum of the Weir Height and the Height Over Weir and is always calculated.
Percent Hole Area: This parameter is used in the calculation of Residence time and in Column sizing. Enter the ratio of perforation area (for sieve trays) or full valve opening (for valve trays) to active area. If this parameter is > 10%, it will not affect the sizing or calculation of Fraction Flooding. If Percent Hole Area is < 10%, a penalty will be applied.
Weir Side Width: If Fraction Active Area is not specified, Weir Widths must be specified, as they are used to calculate the Fraction Active Area. Active area is calculated based on Weir Width(s), and Fraction Active Area is the active area divided by the total area of the stage. The user must enter valid weir widths, since some combinations of these widths might result in calculation of negative active areas. Weir Side Width must be specified for trays with 1, 2, 3, or 4 passes.
Weir Center Width: If Fraction Active Area is not specified, Weir Widths must be specified, as they are used to calculate the Fraction Active Area. Active area is calculated based on Weir Width(s), and Fraction Active Area is the active area divided by the total area of the stage. The user must enter valid weir widths, since some combinations of these widths might result in calculation of negative active areas. Weir Center Width must be specified for trays with 2 or 4 passes.
Weir Off Center Width: If Fraction Active Area is not specified, Weir Widths must be specified, as they are used to calculate the Fraction Active Area. Active area is calculated based on Weir Width(s), and Fraction Active Area is the active area divided by the total area of the stage. The user must enter valid weir widths, since some combinations of these widths might result in calculation of negative active areas. Weir Off Center Width must be specified for trays with 3 or 4 passes.

Random Packing Parameters

Random Packing Types: Select the Random Packing Type from the drop-down list. If your random packing does not appear in the list, you can add a User Defined packing type to the Column Hardware.xml file for use in ProMax.
Flood Model: Select either Packing Factor or Billet-Schultes from the drop-down list. For further information on these models, refer to Packed Column Flood Models.
Stage Pressure Drop: This parameter is the dynamic pressure drop per length of bed. Stage Pressure Drop is calculated and cannot be set by the user.
Holdup: This parameter is the volume of liquid present in the void spaces of the packing per volume of packing. Holdup is always calculated and cannot be set by the user.
Linear Holdup Time: The calculated Linear Holdup Time is the Holdup divided by the Liquid Load (General tab) and represents the holdup time per unit bed height (assuming plug flow). It can be used to estimate the Residence Time used in the TSWEET Kinetics Model. First multiply the Linear Holdup Time by the total height of packing to determine the total holdup time. This total column holdup time is then divided by the number of stages to obtain the Residence Time. The Real/Ideal Stage Ratio should always be set to 1. Adjust the Residence Time if the number of stages is changed.
Surface Area: Surface Area is the packing surface area per unit volume and is specified in the Column Hardware.xml file. (This parameter cannot be specified in the Column Hardware dialog).
Packing Factor: This parameter is used in the packing factor flood model and is specified in the Column Hardware.xml file. (Packing Factor cannot be specified in the Column Hardware dialog).
Void Fraction: This parameter is the packing void space per unit volume and is specified in the Column Hardware.xml file. (Void Fraction cannot be specified in the Column Hardware dialog).
Billet Cfl, Cp, Ch, CL, Cv: These are parameters for the Billet-Schultes packing model and are specified in the Column Hardware.xml file. See Packed Column Flood Models for further information.

Structured Packing Parameters

Structured Packing Types: Select the Structured Packing Type from the drop-down list. If your structured packing does not appear in the list, you can add a User Defined packing type to the Column Hardware.xml file for use in ProMax. See Column Hardware.xml File for details on how to add User Defined packing types.
Flood Model: Select either Sulzer or Billet-Schultes from the drop-down list. The Sulzer model can only be used with Sulzer packing. User Defined packing must use the Billet-Schultes model. For further information on these models, refer to Packed Column Flood Models.
tage Pressure Drop: This parameter is the dynamic pressure drop per length of bed. Stage Pressure Drop is calculated and cannot be set by the user.
Holdup: This parameter is the volume of liquid present in the void spaces of the packing per volume of packing. Holdup is always calculated and cannot be set by the user.
Linear Holdup Time: The calculated Linear Holdup Time is the Holdup (Structured tab) divided by the Liquid Load (General tab) and represents the holdup time per unit bed height (assuming plug flow). It can be used to estimate the Residence Time used in the TSWEET Kinetics Model. First multiply the Linear Holdup Time by the total height of packing to determine the total holdup time. This total column holdup time is then divided by the number of stages to obtain the Residence Time. The Real/Ideal Stage Ratio should always be set to 1. Adjust the Residence Time if the number of stages is changed. See Packed Column Residence Time for further information.
Surface Area: Surface Area is the packing surface area per unit volume and is specified in the Column Hardware.xml file. (This parameter cannot be specified in the Column Hardware dialog).
Void Fraction: This parameter is the packing void space per unit volume and is specified in the Column Hardware.xml file. (Void Fraction cannot be specified in the Column Hardware dialog).
Billet Cfl, Cp, Ch, CL, Cv: These are parameters for the Billet-Schultes packing model and are specified in the Column Hardware.xml file. See Packed Column Flood Models for further information.

Column Hardware.xml File

The Column Hardware.xml file contains data required to make calculations with packing. The file is separated into random and structured packing sections. In addition to Pre-Defined packing types, there may be User Defined packing types. Data within the Pre-Defined packing types blocks should not be modified in any way. However, individual Pre-Defined packing types blocks can be deleted or reordered as desired. The User Defined packing type may be edited and multiple User Defined packing types may be included.


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Free SixxacMenu module license Capabilities Amine Sweetening Glycol Dehydration Heat Exchanger Rating Crude Oil Refining LPG Recovery NGL Fractionation Caustic Treating Sulfur and TGCU Reactors Sour Water Stripper Pipelines Vessel Sizing Other Processes Interface Flowsheet Drawing Multiple Flowsheets Project Viewer Reporting Property Packages Extensibility TSWEET PROSIM Client List Sales Information Testimonials	Separator Sizing ProMax can size horizontal or vertical two- or three-phase separators. Correlations used in vessel sizing calculations are based on Svrcek (1993), Monnery (1994), GPSA Engineering Data Book (1998), and Manning (1995). Vertical Orientation Vertical separators are usually selected when the vapor/liquid ratio is high or total volume is low. A vertical separator occupies less floor space than a horizontal separator and is often considered when plot space is limited. However, a vertical separator may be larger and more expensive than a horizontal separator for the same gas handling capacity due to the upward flow of gas retarding the falling liquid droplets. In the vertical separator, the fluids enter the vessel striking a diverting baffle which initiates primary separation. Liquid removed by the inlet baffle falls to the bottom of the vessel. The gas moves upward, usually passing through a mist extractor or "demister pad" to remove suspended mist. Liquid removed by the demister pad is coalesced into larger droplets which then fall through the gas to the liquid reservoir in the bottom. The ability to handle liquid slugs is typically obtained by increasing height. Level control is not critical and liquid level can fluctuate several inches without affecting operating efficiency. Mist extractors can significantly reduce the required diameter of vertical separators. Horizontal Orientation Horizontal separators are preferred for separating mixtures with a low vapor/liquid ratio or for large volumes of total fluids. Horizontal separators have a much greater gas-liquid interface area than vertical separators, which is useful in degassing solvents and reducing foaming. Increased slug capacity is obtained through shortened retention time and increased liquid level. Three Phase Separator Sizing Three phase units can be either vertical or horizontal, although they typically are horizontal. The vertical orientation is only used if there is a large amount of vapor to be separated from a small amount of the light and heavy liquid (< 10-20% by weight). There are a number of basic horizontal Three Phase Separator configurations. Four typical horizontal configurations are: 1) Interface control, 2) Interface control with boot, 3) Interface control with weir, 4) Bucket and weir. Each of these configurations offers advantages depending on the application. Refer to Monnery and Svrcek 1994 for a detailed discussion of the uses and sizing of various three phase separator configurations. A boot typically is specified when the volume of heavy liquid is not substantial (< 15-20% of total liquid by weight), while a weir is used when the volume is substantial. The bucket and weir type design is used when interface level control may be difficult, such as with heavy oils or when large amounts of an emulsion or a paraffin are present. Separator Thickness Calculations The separator thickness calculations apply to both two phase and three phase separators and are based on ASME Boiler and Pressure Vessel Code Section VIII, 2004. The appropriate separator design formulas may also be found in the ASME Code. The effect of static head due to liquid level in the separator is not included in the minimum separator thickness calculations. Thickness calculations are not performed for separators under external pressure. Further, the separator thickness calculations are based only on the pressure of the separator. Additional thickness and material may be required for supports and other fixtures. Column Sizing and Rating Distillation columns containing trays, random packing, structured packing, or any combination may be sized or rated in ProMax. To calculate Column Diameter for trayed columns, specify Fraction Flooding, Tray Spacing, Weir Height, Froth Model, Percent Hole Area, and Fraction Active Area (or Weir Widths depending on the number of passes). To calculate Fraction Flooding for trayed columns, specify the previous parameters substituting Diameter for Fraction Flooding. To calculate Column Diameter for packed columns, specify Fraction Flooding, System Factor, Packing Type, and Flood Model. To calculate Fraction Flooding for packed columns, specify the previously mentioned parameters substituting Diameter for Fraction Flooding. Column Hydraulic calculations are performed only for VLE or VLLE columns. Columns with only two liquid phases (LLE Column Type) are not sized or rated. Tray Parameters Tray Spacing This parameter is used in the calculation of Residence Time and in Column sizing. Fraction Active Area If this parameter is specified, then Weir Widths are calculated assuming equal flow path lengths. If Weir Widths are specified, Fraction Active Area is calculated and cannot be specified. Weir Height This parameter is used in the calculation of Residence Time and in Column sizing. Number of Passes Select either 1, 2, 3, or 4 pass trays from the drop-down list. Froth Model Select either Bolles-Fair, Colwell, or Stichlmair from the drop-down list. Froth Gravity This parameter is a correction term which converts the Froth Height to the equivalent height of clear liquid and accounts for the fact that the aerated liquid is less dense than the clear liquid. The Froth Gravity may be calculated using the Bolles-Fair, Colwell, or Stichlmair models. This parameter is calculated and cannot be set by the user. Height Over Weir This parameter is the height of liquid above the top of the weir and is always calculated. Froth Height This parameter is the sum of the Weir Height and the Height Over Weir and is always calculated. Percent Hole Area This parameter is used in the calculation of Residence time and in Column sizing. Enter the ratio of perforation area (for sieve trays) or full valve opening (for valve trays) to active area. If this parameter is > 10%, it will not affect the sizing or calculation of Fraction Flooding. If Percent Hole Area is < 10%, a penalty will be applied. Weir Side Width If Fraction Active Area is not specified, Weir Widths must be specified, as they are used to calculate the Fraction Active Area. Active area is calculated based on Weir Width(s), and Fraction Active Area is the active area divided by the total area of the stage. The user must enter valid weir widths, since some combinations of these widths might result in calculation of negative active areas. Weir Side Width must be specified for trays with 1, 2, 3, or 4 passes. Weir Center Width If Fraction Active Area is not specified, Weir Widths must be specified, as they are used to calculate the Fraction Active Area. Active area is calculated based on Weir Width(s), and Fraction Active Area is the active area divided by the total area of the stage. The user must enter valid weir widths, since some combinations of these widths might result in calculation of negative active areas. Weir Center Width must be specified for trays with 2 or 4 passes. Weir Off Center Width If Fraction Active Area is not specified, Weir Widths must be specified, as they are used to calculate the Fraction Active Area. Active area is calculated based on Weir Width(s), and Fraction Active Area is the active area divided by the total area of the stage. The user must enter valid weir widths, since some combinations of these widths might result in calculation of negative active areas. Weir Off Center Width must be specified for trays with 3 or 4 passes. Random Packing Parameters Random Packing Types Select the Random Packing Type from the drop-down list. If your random packing does not appear in the list, you can add a User Defined packing type to the Column Hardware.xml file for use in ProMax. Flood Model Select either Packing Factor or Billet-Schultes from the drop-down list. For further information on these models, refer to Packed Column Flood Models. Stage Pressure Drop This parameter is the dynamic pressure drop per length of bed. Stage Pressure Drop is calculated and cannot be set by the user. Holdup This parameter is the volume of liquid present in the void spaces of the packing per volume of packing. Holdup is always calculated and cannot be set by the user. Linear Holdup Time The calculated Linear Holdup Time is the Holdup divided by the Liquid Load (General tab) and represents the holdup time per unit bed height (assuming plug flow). It can be used to estimate the Residence Time used in the TSWEET Kinetics Model. First multiply the Linear Holdup Time by the total height of packing to determine the total holdup time. This total column holdup time is then divided by the number of stages to obtain the Residence Time. The Real/Ideal Stage Ratio should always be set to 1. Adjust the Residence Time if the number of stages is changed. Surface Area Surface Area is the packing surface area per unit volume and is specified in the Column Hardware.xml file. (This parameter cannot be specified in the Column Hardware dialog). Packing Factor This parameter is used in the packing factor flood model and is specified in the Column Hardware.xml file. (Packing Factor cannot be specified in the Column Hardware dialog). Void Fraction This parameter is the packing void space per unit volume and is specified in the Column Hardware.xml file. (Void Fraction cannot be specified in the Column Hardware dialog). Billet Cfl, Cp, Ch, CL, Cv These are parameters for the Billet-Schultes packing model and are specified in the Column Hardware.xml file. See Packed Column Flood Models for further information. Structured Packing Parameters Structured Packing Types Select the Structured Packing Type from the drop-down list. If your structured packing does not appear in the list, you can add a User Defined packing type to the Column Hardware.xml file for use in ProMax. See Column Hardware.xml File for details on how to add User Defined packing types. Flood Model Select either Sulzer or Billet-Schultes from the drop-down list. The Sulzer model can only be used with Sulzer packing. User Defined packing must use the Billet-Schultes model. For further information on these models, refer to Packed Column Flood Models. tage Pressure Drop This parameter is the dynamic pressure drop per length of bed. Stage Pressure Drop is calculated and cannot be set by the user. Holdup This parameter is the volume of liquid present in the void spaces of the packing per volume of packing. Holdup is always calculated and cannot be set by the user. Linear Holdup Time The calculated Linear Holdup Time is the Holdup (Structured tab) divided by the Liquid Load (General tab) and represents the holdup time per unit bed height (assuming plug flow). It can be used to estimate the Residence Time used in the TSWEET Kinetics Model. First multiply the Linear Holdup Time by the total height of packing to determine the total holdup time. This total column holdup time is then divided by the number of stages to obtain the Residence Time. The Real/Ideal Stage Ratio should always be set to 1. Adjust the Residence Time if the number of stages is changed. See Packed Column Residence Time for further information. Surface Area Surface Area is the packing surface area per unit volume and is specified in the Column Hardware.xml file. (This parameter cannot be specified in the Column Hardware dialog). Void Fraction This parameter is the packing void space per unit volume and is specified in the Column Hardware.xml file. (Void Fraction cannot be specified in the Column Hardware dialog). Billet Cfl, Cp, Ch, CL, Cv These are parameters for the Billet-Schultes packing model and are specified in the Column Hardware.xml file. See Packed Column Flood Models for further information. Column Hardware.xml File The Column Hardware.xml file contains data required to make calculations with packing. The file is separated into random and structured packing sections. In addition to Pre-Defined packing types, there may be User Defined packing types. Data within the Pre-Defined packing types blocks should not be modified in any way. However, individual Pre-Defined packing types blocks can be deleted or reordered as desired. The User Defined packing type may be edited and multiple User Defined packing types may be included.