Aspen Workshop Radfrac (1)

$: Aspen Workshop Radfrac (1)$
RadFracRadFracProcess Modeling Process Modeling

using Aspen Plususing Aspen Plus

Faculty of Chemical and Natural Resources Engineering

Universiti Malaysia Pahang

2008

Aspen Workshop 2008Aspen Workshop 2008

ObjectivesObjectives

Enter the minimum input required for the Enter the minimum input required for the RadFrac fractionation modelRadFrac fractionation model

Implement design specificationsImplement design specifications


RadFrac Flowsheet ConnectivityRadFrac Flowsheet Connectivity


Some RadFrac optionsSome RadFrac options To set up an absorber with no condenser or reboiler, set To set up an absorber with no condenser or reboiler, set

condenser and reboiler to none on the RadFrac Setup condenser and reboiler to none on the RadFrac Setup Configuration sheetConfiguration sheet

Either Vaporization or Murphree efficiency on either a stage or Either Vaporization or Murphree efficiency on either a stage or component basis can be specified on the RadFrac Efficiency component basis can be specified on the RadFrac Efficiency formform

Tray and packed column design and rating is possibleTray and packed column design and rating is possible

A second liquid phase may be modeled if the user selects A second liquid phase may be modeled if the user selects Vapor-Liquid-Liquid as Valid phaseVapor-Liquid-Liquid as Valid phase

Reboiler and condenser heat curves can be generatedReboiler and condenser heat curves can be generated


RadFrac demonstrationRadFrac demonstration

RadFrac SpecificationsRadFrac Specifications Partial condenserPartial condenser Kettle reboilerKettle reboiler 15 stages15 stages R = 1.5R = 1.5 Distillate to feed ratio = 0.6Distillate to feed ratio = 0.6 Column pressure = 315 Column pressure = 315

psiapsia Feed stage = 8Feed stage = 8

B1FEED

OVHD

BOTM

Flow= 1000 lbmol/hr

T= 190 F

P= 315 psia

Mole fraction

C1: 0.26

C2: 0.09

C3: 0.25

nC4: 0.17

nC5: 0.11

nC6: 0.12

Use the RKS-BM Property method


RadFrac Configuration SheetRadFrac Configuration Sheet

SpecifySpecify

Number of stageNumber of stage Condenser and reboiler Condenser and reboiler

configurationconfiguration Two column operating Two column operating

specificationsspecifications Default: distillate rate and Default: distillate rate and

reflux ratioreflux ratio Valid phasesValid phases Convergence Convergence


RadFrac Setup Streams SheetRadFrac Setup Streams Sheet

SpecifySpecify

Feed stream locationFeed stream location Feed stream conventionFeed stream convention

Above-stageAbove-stage On-stageOn-stage

Bottom and overhead Bottom and overhead product streamsproduct streams

Side productsSide products


RadFrac Setup Pressure SheetRadFrac Setup Pressure Sheet

Specify one of:Specify one of:

Top/bottom pressureTop/bottom pressure Pressure profilePressure profile Section pressure dropSection pressure drop


Plot Wizard (1)Plot Wizard (1) Use the plot wizard (on th eplot menu) to quickly Use the plot wizard (on th eplot menu) to quickly

generate plot results of a simulation. You can generate plot results of a simulation. You can use the Plot wizard for displaying results for the use the Plot wizard for displaying results for the following operations:following operations: Assay data analysisAssay data analysis Physical property analysisPhysical property analysis Data regression analysisData regression analysis Profiles for all separation models including RadFrac, Profiles for all separation models including RadFrac,

MultiFrac, and PetroFracMultiFrac, and PetroFrac Click the object of interest in the data browser to Click the object of interest in the data browser to

generate plots for that particular objectgenerate plots for that particular object


Plot Wizard (2)Plot Wizard (2)

The Plot Wizard guides The Plot Wizard guides you in the basic you in the basic operations for generating operations for generating a plota plot

In Step 2, click the plot In Step 2, click the plot type you wish to type you wish to generate, then click generate, then click Next> to continueNext> to continue

Click the Finish button to Click the Finish button to generate a plot with generate a plot with default settingsdefault settings


Plot Wizard DemonstrationPlot Wizard DemonstrationUse the Plot Wizard to create plots of temperature, flows, and compositions throughout the column


Design Specs and VaryDesign Specs and Vary

Design specifications can be specified inside the Design specifications can be specified inside the RadFrac block using DesignSpecs and Vary formsRadFrac block using DesignSpecs and Vary forms

One or more RadFrac inputs can be manipulated to One or more RadFrac inputs can be manipulated to achieve specifications on one or more RadFrac achieve specifications on one or more RadFrac performance parametersperformance parameters

The number of specs should, in general, be equal to the The number of specs should, in general, be equal to the number of variesnumber of varies

The DesignSpecs and Varys in a RadFrac are solved in The DesignSpecs and Varys in a RadFrac are solved in a “Middle loop”. If you get an error message saying that a “Middle loop”. If you get an error message saying that the middle loop was not converged, check the the middle loop was not converged, check the DesignSpecs and Varys you have entered.DesignSpecs and Varys you have entered.

Workshop (1)Workshop (1)Methanol TowerMethanol Tower


B1

FEED

DIST

BOTM

63.2 wt% water

36.8 wt% methanol

Flow= 120000 lb/hr

Pressure= 18 psia

Saturated liquid

38 trtays (40 stages)

Feed tray= 23 (stage 24)

Total condenser

Top stage pressure= 16.1 psia

Pressure drop per stage= 0.1 psia

Distillate flow rate= 1245 lbmol/hr

Molar reflux ratio= 1.3

Use the NRTL-RK property method

Objective: Set up a methanol towerObjective: Set up a methanol tower


Part APart A

Record the column duties:Record the column duties: Condenser duty:Condenser duty: Reboiler duty:Reboiler duty:

Record composition:Record composition: Mass fraction of methanol in the distillate:Mass fraction of methanol in the distillate: Mass fraction of water in the bottom:Mass fraction of water in the bottom:

Make plots of temperature, flows, and Make plots of temperature, flows, and compositioncomposition


Part BPart B

Set up DesignSpecs within the column so Set up DesignSpecs within the column so that there is:that there is: 99.95 wt% methanol in the distillate99.95 wt% methanol in the distillate 99.90 wt% water in the bottom99.90 wt% water in the bottom

Vary the distillate rate (800-1700 lbmol/hr) Vary the distillate rate (800-1700 lbmol/hr) and reflux ratio (0.8-2)and reflux ratio (0.8-2)

Record the final values for:Record the final values for: Distillate rate:Distillate rate: Reflux rate:Reflux rate: Condenser duty:Condenser duty: Reboiler duty:Reboiler duty:


Part CPart C

Perform the same calculations after Perform the same calculations after specifying a 65% Murphree efficiency for specifying a 65% Murphree efficiency for each tray. Assume the condenser and each tray. Assume the condenser and reboiler have stage efficiencies of 90%. reboiler have stage efficiencies of 90%. Determine how these efficiencies affect Determine how these efficiencies affect the column duties:the column duties: Condenser duty:Condenser duty: Reboiler duty: Reboiler duty:


Part DPart D

Perform a tray sizing calculation for the Perform a tray sizing calculation for the entire column, given that Bubble Cap trays entire column, given that Bubble Cap trays are usedare used Record the predicted column diameterRecord the predicted column diameter

Aspen Workshop Radfrac (1)

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