1. Overview:Use this form to specify tray and/or packing configurations for sizing and rating.Each column internals object represents a complete configuration of trays and/or packing for the column along with specifications for sizing or rating. You can specify a combination or trays and packing in the same configuration.Create multiple internals configurations when you wish to quickly evaluate the performance of column with different internals types. For example, you might wish to compare/evaluate the feasibility of using different tray types (Valve or Sieve) or compare the benefits of using a packed column versus a trayed column.The table displays the following information for each configuration:Each column internals object contains these forms:In the Column Design tab of the ribbon, when results are available you can click Reports to generate a PDF report for the column design, or Export to Vendor to generate files of the column design for vendor packages.2. RadFrac Column Internals sections Form2.1 OverviewRadFrac Column Internals Sections Sections SheetUse this sheet to divide the column into sections. You may use one section for the entire column or split the column into multiple sections, but your sections must not overlap or leave gaps. A complete configuration of column internals must include all stages except the condenser and reboiler, if the column is equipped with these.At the top of the form, the Column description lets you specify a description of up to 128 characters for the entire internals configuration; this is the same description that appears in the Column Internals form. Below this are the following buttons:Specifying SectionsFor each section, specify:∙The start and end stages∙The mode: Interactive sizing or Rating∙Type of internals in this section: Trayed or Packed∙The type of trays or packing∙The number of passes for trays, or the packing vendor, material, and dimension for packing ∙For trays, the spacing between trays, or for packing, the height of packing in the section∙The diameter of the sectionAll of these specifications except the start and end stages can also be made on the Geometry sheet for that section. You must always specify the start and end stages; most other values have defaults:∙In Interactive Sizing mode, defaults are available for all fields except section packed height.∙In Rating mode, defaults are available for all fields except diameter, section packed height (for packing), and downcomer widths and locations (for trays; these must be specified on the Geometry sheet).Overall Column ConfigurationA diagram displays the layout of the column with adjacent sections in alternating colors, showing the locations of feeds, products, pumparounds, and gaps and overlaps between sections. A message at the top right of the sheet indicates where any gaps are located. If the column sections are of different diameters, the sections are depicted with widths proportional to those diameters.Above this diagram, a label indicates whether this column configuration is active (i.e. is selected as the design basis on the Column Internals form).In large columns, when there are multiple feeds, draws, and/or pumparound returns on the same or near stages such that the arrows would overlap, you can hover the mouse over the arrow to see information about the connections there.Pressure Drop SpecificationsIn Rating mode, in the active configuration, you can choose to calculate the pressure drops across the column while material and energy balances are being solved. Below the grid, select:∙Don't update pressure drop: Do not calculate pressure drop. RadFrac uses the pressure specified on the Specifications | Setup | Pressure sheet for all stages.∙Update pressure drop from top stage: The pressure specified for the condenser or top stage is used, and other stage pressures are calculated relative to it.∙Update pressure drop from bottom stage: The pressure specified for the reboiler or bottom stage is used, and other stage pressures are calculated relative to it.By default, the calculated pressure drop across each stage includes the contribution due to static vaporhead, ρv gh where ρv is the vapor mass density, g is gravitational acceleration, and h is the tray spacing (for trays) or the packed height per stage (for packing). Uncheck Include static vapor head in pressure drop calculations to ignore this contribution.SumpRadFrac can optionally calculate the pressure drop across the sump. To do so, specify the diameter of the sump (which defaults to the diameter of the bottom stage) and either the liquid level in the sump or the residence time in the sump.Other FormsEach section has two forms on which you can make detailed specifications and view results:The Hydraulic Plots form also displays plots of results for the entire column configuration, and the ColumnHydraulic Results form displays tabular results for the whole column.2.2 Import Template Dialog BoxSee AlsoUse this dialog box to import previously saved templates (XML files) for column sections.In the Import from box, click and select a template file.Then either click Create new section from imported template, or click Import to section and check the boxes to indicate which existing sections should load the template. All specifications in the existing sections, except for the start and end stages, will be overwritten by the data from the template.Click Import to complete the import.2.3 Export as Template Dialog BoxUse this dialog box to save specifications for a column section as a template (XML file) which can be loaded into other column sections in this or another Aspen Plus file.In the Export section field, select the section to export.In the to File box, click to select a folder for the exported file and type a file name.Click Export to export the file3 RadFrac Column Internals Sections Geometry Form3.1 OverviewUse this form to specify the geometry of a column internals section. This form contains the following sheets (though some of them only appear when certain options are selected):3.2 RadFrac Column Internals Sections Geometry Geometry SheetUse this sheet to specify:∙Section type: Trayed or Packed∙Mode: Interactive sizing or Rating∙Tray or packing geometryMost fields have default values, though the availability and method of determining defaults depends on mode and section type.At the top, information displayed includes the name of the section, its start and end stages, and whether the column configuration this section is part of is active (i.e. is the selected design basis on the Column Internals form).When you change units for a field on this sheet, the value is updated to display in the new units.Interactive Sizing ModeDefaults for geometry fields are calculated using the design criteria specified on the Design Parameters sheet. Sizing results are based on the stage or tray with the largest liquid volume flow rate; see the Results | By Stage/ByTray sheet to check these flows, if needed.Trays∙Diameter is calculated using the % Jet flood for design (default 80%), the Minimum downcomer area / Total tray area (default 0.1), and the Maximum downcomer loading calculated by the specified method. All of theseare specified on the Design Parameters sheet. Note that weeping is not accounted for in the sizing calculation.See Tray and Downcomer Area Calculations for details about this calculation.∙The number of passes is adjusted to satisfy the Maximum weir loading specified onthe Design Parameters sheet. If you specified the diameter, this heuristic is used to determine if an increase inthe number of passes is justified:o Columns of at least 5 foot diameter require at least 2 passes.o Columns of at least 8 foot diameter require at least 3 passes.o Columns of at least 10 foot diameter require 4 passes.∙For multi-pass trays, the downcomer locations are adjusted based on an equal flow path length design.Packing∙Diameter is calculated using the selected sizing criterion (either % Approach to maximum capacity (L/V) or Design capacity factor) specified on the Design Parameters sheet. The default is an approach tomaximum capacity of 80%Notes:∙In Interactive Sizing mode, calculated defaults for values such as diameter will change when the vapor-liquid traffic in the column changes. If you overwrite calculated defaults for geometry parameters, those values will NOT change when vapor-liquid traffic in the column changes.∙Interactive Sizing mode cannot be used if the column is specified as Rate-Based. To calculate the internals geometry for a Rate-Based Column, please do the following:1.Set the Calculation Type to Equilibrium on the Setup | Configuration sheet2.Create Column Internals and calculate geometry in Interactive Sizing mode.3.Change the internals mode to Rating.4.Change the Calculation Type to Rate-Based on the Setup | Configuration sheet.∙When you switch from Interactive Sizing to Rating, the calculated values of Diameter, Downcomer Widths, and Downcomer Locations will be retained and appear as defaults (blue italics). If you clear or delete these values in Rating mode, the simulation will become incomplete. You can specify your own values, or switch back to Interactive Sizing and back to Rating again to populate these fields and make the simulation complete.Rating ModeDefaults are available for all fields except diameter and (for trays) the downcomer width and locations.Note: In Rating mode, diameter and other geometry will NOT change when vapor-liquid traffic in the column changes. Deleting the diameter and other geometry-related fields will cause the simulation to becomeincomplete.Trayed SectionsFor each tray section, the following specifications are available:Calculated by Aspen Plus for sieve trays. To achieve a desired number of holes, set the Hole area/active area to where active areais the cross-sectional area of the column () minus the areas at the top and bottom of all downcomers (or just minus the top areas of downcomers if Active area under downcomer is checked). To compute downcomer areas, see Tray and Downcomer Area Calculations.Packed SectionsSpecify packing geometry in three steps, as labeled in the diagram:1.Choose the packing type. The options available in the Packing characteristics section update based on theselected packing type.2.Specify the specific packing by choosing a Vendor, Material, and Dimension. Also specify the diameter ofthe packed section. If the packing factor for the selected packing is available in the database, it is filled in. Forsome vendors, it is locked and cannot be changed. If you choose a GPDC-based Pressure drop calculationmethod on the Design Parameters sheet, and Packing factor is missing for the selected packing, you mustspecify it.If you have loaded a simulation from a past version, you can use Update Parameters to compare the packingparameters in the current version with those used when you saved your simulation.3.Specify either the height equivalent to a theoretical plate (HETP) or the height of the entire section. If youspecify the height of the entire section, Aspen Plus divides that equally over the stages to determine the HETP.3.3 Update Packing Parameters Dialog BoxSee AlsoPacking Types and Packing FactorsUse this dialog box to selectively update packing parameters from past simulations to the values from the newpacking database.At the top of the dialog box are the packing specifications for the packed column section from which you launchedthis dialog box. Below this, the parameters for this packing appear in three columns. The Current Value columnshows the value now used in your simulation, regardless of its source. The Database Value column shows the valuein the selected database (usually the latest one; you can select the database on the Setup | Calculation Options |Calculations sheet), or blank if there is no value in the database for this parameter.You can select the checkboxes in the Update column to indicate that you want to use the database value instead ofthe current value. For the Stichlmair C1, C2, and C3 parameters there is a single Update checkbox that applies to allthree parameters. You can click Select All to automatically mark all checkboxes, Clear All to clear all of them,or Select Valid Database Values to automatically mark all checkboxes for parameters where the database has avalue.Select Save database values as user entered if you want to preserve the values you update as if you had enteredthem. If this option is not selected, values updated from the database are not saved with the simulation; if the selected database is Latest, this will cause the parameters to be automatically updated in future versions of Aspen Plus.When you click OK, the database values for parameters where you have marked Update overwrite the onespreviously specified.Note: In Aspen Plus 2006 and previous versions, the packing parameters were always saved with the simulation,and it is impossible to distinguish these from user-entered values.3.4 RadFrac Column Internals Sections Geometry Picketed/Swept-Back Weirs SheetSee AlsoWhen Picketed or Swept-back weirs are selected as Weir Modifications on the Geometry sheet, use this sheet to specify geometry parameters specific to those weir types. This sheet only appears in tray sections with picketed or swept-back weirs.Picketed WeirsUse picketed weirs increase the weir loading for 1-pass trays, or balance the weir loading for multi-pass trays. Picketed weirs have "pickets" which rise up above the top of the weir, effectively blocking part of the weir length. The picketing fraction represents the fraction of the weir length which is blocked in this way. The effective weir length which liquid flows over is reduced by the picketing fraction, which increases the weir loading.In Rating mode, the default picketing fraction is 0 for all weirs.In Interactive Sizing mode, the default picketing fraction is calculated in one of these ways:∙For 1-pass trays, if the weir loading for the unpicketed weir is greater than the Minimum weirloading specified on the Design Parameters sheet, the default picketing fraction is 0. Otherwise, the default picketing fraction is calculated based on the extent of picketing required to raise the minimum weir loading to the specified weir loading:∙For multi-pass trays, the default picketing fractions for center and off-center weirs are calculated based on the extent of picketing required to make the weir loading equal across all weirs. The side weir defaults to 0 picketing fraction.The weir length and weir loading for each section are also shown, for reference.Swept-Back WeirsUse swept-back weirs to increase the effective length of the side weirs and decrease the weir loading.Three different shapes for swept-back weirs are available, corresponding with designs offered in vendor programs SulCol, KG-Tower, and FRI. Choose one of these shapes, and then specify the geometry parameters in the diagram.∙SulCol: Specify lengths A, B, and S, which define the size and shape of the swept-back portion of the weir.In Interactive sizing mode, if the loading of the side weir exceeds the Maximum weir loading specified onthe Design Parameters sheet, S is calculated to ensure that the effective weir loading of the swept back weirequals the maximum weir loading. This effective weir loading is calculated as:The default for A is 2/3 of the width of the side downcomer, and the default for B is 2/3 of A.∙KG-Tower: Specify the depth from the main part of the weir at the point where it is most swept back. Theother geometry parameters are defined relative to this.The default for this depth is calculated in the same way as the default for S in the Sulcol weir.∙FRI: Specify the lengths of the three different segments of the weir.The defaults are calculated in the same was as the default for S in the Sulcol weir.The following results are displayed on this sheet:∙The tray with maximum weir loading∙The maximum weir loading for this tray∙The maximum allowable weir loading (from the Design Parameters sheet)∙Actual side weir length of swept-back weir∙Effective (or projected) side weir length of the swept-back weir∙The percentage of tray active area lost due to the swept-back weirs3.5 RadFrac Column Internals Sections Geometry Design Parameters SheetUse this sheet to specify design parameters in Rating mode for both tray and packing sections. The parametersavailable are different for tray and packing sections, but include pressure drop and flooding parameters in both cases.Tray ParametersSizing CriterionHydraulic plots / LimitsThese parameters are only used in the user interface for determining the limits in hydraulic plots. They are not available in the engine and cannot be accessed by design specs, calculators, and the like.Design factorsCalculation methodsPacking ParametersSizing criterionDesign factorsHydraulic plot / Pressure dropThese parameters are only used in the user interface for determining the limits in hydraulic plots. They are not available in the engine and cannot be accessed by design specs, calculators, and the like.Hydraulic limits for column targetingReferencesResetarits, M.R. and Ogundeji, A.Y. "On Distillation Tray Weir Loading." AIChE Spring National Meeting, Tampa, FL (April 26-30, 2009).3.6 RadFrac Column Internals Sections Geometry Packing Constants SheetThis sheet only appears in packed sections.Use this sheet to specify Specific surface area and Void fraction for packings. These parameters are used in many pressure drop/flood correlations for packings.In addition, you can specify other parameters needed to calculate pressure drop and liquid holdup only when youspecify the Stichlmair method on the Design Parameters or Sizing Parameters sheet.These parameters apply only to sections with Packing. The databank contains defaults for these parameters for many packings, which are filled in automatically when available. Use this sheet to override the databank values or supply missing values.3.7 RadFrac Column Internals Sections Geometry Tray Geometry Summary SheetThis sheet only appears in tray sections.Use this sheet to view a summary of the dimensions of each tray, including the active area and area for eachdowncomer (for tray sections only). The first table displays properties which apply to entire trays, such as trayspacing and deck thickness. The second table displays weir and downcomer properties which may be set differently for downcomers in different positions on multiple-pass trays.For details about these calculations, see Tray and Downcomer Area Calculations.4 RadFrac Column Internals Sections Results Form4.1 OverviewUse this form to view the results for a section. This form contains the following sheets:4.2 RadFrac Column Internals Sections Results Summary SheetUse this sheet to view overall tray or packing rating results for a section. For detailed results for individual stages, see the By Stage/By Tray sheet.Trayed SectionsThe following results are shown for a trayed section:∙Starting and ending stages of the section∙Tray type∙Number of tray passes∙Tray spacing∙Diameter of the section∙Height of the section∙Pressure drop across the section. Includes static vapor head if the option to do so is selected.∙Head loss across the section, in inches of hot liquid∙List of trays affected by weepingThe Limiting conditions table shows key results that can help to identify trays in the column that might be operating close to or outside acceptable limits. The following results are shown. For each condition, in addition to the value, the tray where the maximum occurs is listed. For loadings, the downcomer or weir where the maximum occurs isalso listed.∙Maximum % jet flood∙Maximum % downcomer backup (aerated)∙Maximum downcomer loading∙Maximum weir loading∙Maximum aerated height over weir∙Maximum % approach to system limit∙Maximum Cs based on bubbling (active) areaPacked SectionsThe following results are shown for a packed section:∙Starting and ending stages of the section∙Diameter of the section∙Packed height per stage∙Total height of the section∙Maximum % capacity (at constant L/V) in the section∙Maximum capacity factor in the section∙Pressure drop across the section. Includes static vapor head if the option to do so is selected.∙Average pressure drop / Height∙Average pressure drop / Height (Frictional). This is the average pressure drop per unit packing height excluding the contribution from static vapor head.∙Maximum stage liquid holdup∙Maximum stage superficial velocity in the section∙Surface area of the packing∙V oid fraction of the packing∙Stichlmair constants for the packingFor information about the methods used to calculate some of these packing results, see Packed Columns.Rate-Based designFor both trays and packing, the Calculated diameter appears if the column is Rate-Based (Calculationtype on Specifications | Setup | Configuration sheet) and Design mode to calculate column diameter is checked on the Rate-Based Modeling | Rate-based Setup | Design sheet, showing the result of that design calculation.4.3 RadFrac Column Internals Sections Results By Stage/By Tray SheetThis is called the By Stage sheet for packed sections and the By Tray sheet for tray sections.Use this sheet to view stage-by-stage results for tray and packing rating calculations. For each stage in this section, many results are shown. Use the View field to select which results are shown (selecting All shows all of theseresults):Hydraulic resultsFor trays, these results are shown.∙Percent Jet flood∙Total pressure drop: The sum of dry pressure drop, clear liquid height on the tray, and any residual pressuredrop terms that might apply.∙Percent Downcomer backup (Aerated): Downcomer backup (aerated liquid) divided by the total of trayspacing and weir height, expressed as a percentage∙Dry pressure drop: Average pressure drop for a tray when the liquid flow is zero. This is reported in bothpressure drop units and equivalent liquid head units.∙Total pressure drop (Head loss): Same as Total pressure drop, reported in head units.∙Downcomer backup: Average height of aerated liquid and of unaerated liquid in the downcomers.∙Percent Downcomer backup (Unaerated): Downcomer backup (unaerated liquid) divided by the total of tray spacing and weir height, expressed as a percentage∙Liquid mass rate/Column area∙Liquid volume rate/Column area∙Fs (net area):∙Fs (bubbling or active area):∙Cs (net area):∙Cs (bubbling or active area):∙Downcomer exit velocity for each downcomer type (depending on number of tray passes)∙Approach to system limit (as a percentage)∙Height over weir (of aerated and unaerated liquid)∙For each downcomer type (depending on number of tray passes):o Volumeo Residence timeo Velocity from topo Velocity from bottomFor packed sections, the results are:∙Packed height∙Percent capacity (based on constant L/V ratio or constant liquid rate)∙Pressure drop (includes static head if this option is selected)∙Pressure drop per height (Frictional). Does not include static head contribution.∙Liquid holdup∙Liquid velocity∙Fs∙Cs∙Approach to system limitHydraulic results-ShortThis provides a summary of just the key results for each tray/stage. The results include:∙Percent jet flood (trays only)∙Total pressure drop (trays only)∙Percent downcomer backup (aerated) (trays only)∙Percent capacity at constant L/V (packing only)∙Pressure drop per height (Frictional) (packing only)∙Liquid mass flow (liquid from stage, including any liquid draw from the stage)∙Vapor mass flow (vapor to stage)∙Liquid mass density∙Vapor mass density∙Liquid viscosity∙Vapor viscosity∙Surface tensionState conditionsAll liquid results apply to the liquid leaving a stage/tray and include any liquid draw from the stage/tray. All vapor results apply to vapor entering a stage/tray.∙Liquid temperature∙Vapor temperature∙Liquid mass flow∙Vapor mass flow∙Liquid volume flow∙Vapor volume flowPhysical propertiesAll liquid results apply to the liquid leaving a stage/tray. All vapor results apply to vapor entering a stage/tray.∙Liquid molecular weight∙Vapor molecular weight∙Liquid mass density∙Vapor mass density∙Liquid viscosity∙Vapor viscosity∙Surface tension (for liquid leaving a stage/tray)4.4 RadFrac Column Internals Sections Results Messages SheetSee AlsoThis sheet displays messages related to column behavior. These messages appear next to an icon indicating theseverity of the message:∙Message: This indicates potentially useful information, such as general design guidelines which are violated, which do not necessarily indicate a problem.∙Warning: This indicates a problem which may cause operational issues with the column.∙Error: This indicates a problem which will almost certainly prevent proper operation of the column.5 RadFrac Column Internals Hydraulic Plots FormUse this form to view hydraulic operating diagrams for the column. These results are only available for trays; inmixed tray/packed columns, blanks will appear for stages in packed sections. Hydraulic plots are also not available for sections where jet flooding or pressure drop is calculated by a user subroutine.Column DiagramAt the left, a column diagram appears. There are three different views of the column available through tabs at the top.∙Stages depicts the sections in proportion to their diameter, and indicates the locations of feeds and products.You can hover the mouse over any of these arrows to see a tooltip indicating the connected stream(s).∙Vapor depicts the stages as bars indicating the stable range for the vapor flow rate on each stage. This bar is colored blue if the flow rate is in the stable region, yellow if it is near a stability limit (within a range specified by Warning status (% to limit) on the Design Parameters sheet), and red if the flow is outside the stable region (using other limits defined on that sheet). A dot indicates the current operating point.∙Liquid does the same for the liquid flow rates, including the colors.On this diagram, five stages are surrounded by a box; small diagrams for each of these stages are shown at the bottom of the form in the Carousel. You can also click any stage to center the carousel on the stage and display the stability diagram for that stage.Downcomer Loading and Weir LoadingIf the selected stage is a tray, these diagrams appear below the column diagram. The Downcomer Loading diagram shows a bar chart of the downcomer loadings (for each downcomer in multiple-pass trays). Downcomer loading is volumetric flow per time per cross-sectional downcomer area. The Weir Loading shows a bar chart of the weir loadings (for each weir in multiple-pass trays). The minimum and maximum acceptable weir loadings, taken either from specified values or Aspen Plus defaults, are shown as horizontal lines across the bar chart. Weir loading is volumetric flow of liquid over the weir per time per length of weir. For 3 and 4 pass trays, thelabels OCIn and OCOut stand for the off-center inside weir (the weir on the off-center downcomer for the panel toward the center of the column) and the off-center outside weir.Stability DiagramTrays。
