aspen塔模拟教程

RadFrac for Dummies:A How to Guide on Aspen Plus ArrayThis example will show how to use Radfrac on Aspen Plus to model distillation columns. The feed shown in the diagram above will consist of 50 lbmol/hr of Methanol and 50 lbmol/hr of water. A purity of 99.5% is desired in both thebottoms and distillate product streams using a reflux ratio of 1.5.Click on the red arrow on the left side of the column to add your feed stream. For this simulation there is only one feed stream, if there were more feed streams use the blue arrow on the left of the column to add more streams.Enter “Feed” in the ID box when prompted for this simulation.Click “OK”.If this box doesn’t appear it is because your flowsheet isn’t complete. A box will then appear telling you what part of the flowsheet you are missing.This box should appearand a title for this simulation can now be entered although is not mandatory for this simulation. Click on the Next button to continue entering numerical data.If this box doesn’t appear you can go to Setup onthe left-hand side of thebox and click on that.The Components box will be the next to appear. This allows us to enter all of the components that will be present within our system; in this simulation they will be Methanol and Water.AspenPlus will now search its database and attempt to match a chemical name with the Component ID that was entered. If this happens the other three boxes (Type, Component Name, and Formula) will fill automatically and other components can then be entered.The next screen to appear will show the interaction parameters for the components in our system using the base method we selected. If you are happy with this numbers (and we sure hope you are) click “Next.”A prompt screen will appearasking if we want to enter anymore data or change theproperty specifications.Since everything is good to go,click “OK.”Now it’s time tobegin entering thephysical data for thesystem. The firstscreen that willappear will be for theFeed stream.Before we actuallystart entering datalet’s go over acouple of thedifferent availableoptions.Now is the time we’ll all been waiting for, designing the actual column. The first step is to get at least a rough estimate for the required number of stages needed.we’re going to use AspenPlus to generate a T-XY plot and use it to do a quick McCabe-Thile diagram. At the top of the screen under Tools, click on Analysis, Property, and Binary.AspenPlus should generate thisliquid/vapor equilibrium plot for Methanol and Waterat 1 atm. The X-axis is the molefrac of Methanol, so the extreme left and extreme right represent pure Water and MeOH respectively.Notice that there are no azeotropes between the two so perfect separation is theoretically possible.This diagram cangive us an estimateof how manyequilibrium stagesare necessary byusing the McCabe-Thiele method.Unfortunately, wecannot show youthe actual drawingbut trust us; ittakes about 7equilibrium stages.After the graph hasbeen made andlooked at you canclose all threewindows that arefor the graph.A box will appear prompting youfor a section number.Click “OK” to continue.This screen allows us tochoose from a list ofpossible types of trayswithin our column.Enter a 2 in the startingstage and a 9 in theending stage becausethere are 10 stages inour column as both thecondenser and reboilercount as stages.Here’s the moment we’ve been waiting for. We’re ready to run our simulation. Click “OK.”Double-click on the blue Blocks folder and then also on Dist.Next, go to the top menu bar and click on Plot and then Plot Wizard.Plot Wizard takes the profiles AspenPlus generated for the column and turns them into pretty little charts.Upon completion click on the blue folder again and go under Results Summary and then Streams. The results show that we now have 94.9% purity in each of the product streams. Moving in the right direction but still not up to the desired specs.Let’s take a look at the Liquid Composition diagram…Double-click on the blue Blocks folder and then on the blue Dist folder to look at the results for the column.Go to Plot at the top of the screen and click on Plot Wizard.Hit “Next” through the welcoming screen and click on the Composition plot. Choose to plot Both Components in the Liquid phase and hit “Finish.”From this plot it is obvious that our feed stage is a little bit too low.We want the composition to be smooth lines without any humps or bumpsin the middle.Close the Results folder and let’s go adjust our feed stage.After you’ve determined the optimum feed plate location (HINT: 9) your plot should look like this.Next check your stream results to see if we have achieved the desired purity in our Methanol Stream.Unfortunately we still haven’t reached the desired purity in our product streams. But we did increase the purity by 3% to 97.5% by optimizing the location of the feed plate.Since the reflux ratiois given at 1.5 in the problem statement,the only other option is to continue to increase the number of stagesin our column.Return to the Setupscreen under the Blocks/Dist folder.Click on the Configuration tab at the top and increase the number of stages in the column.Also, go under the Tray Sizing and Tray Rating folders and change the ending stage on each to one stage less than the actual number of stages that you entered here.Next click on the Streams tab and change the location of the feed plate. Click on “Next” to run the simulation, then check the liquid composition diagram to be sure that it is in the optimum position. If it is, check the results. Continue this procedure until you meet the given purity spec.The other way we canobserve the pressuredrop is by using PlotWizard to create agraph.Go to Plot Wizard andclick on the Pressuregraph.Choose the desiredunits and click “Finish.”A graph similar to thisone should be createdshowing the pressureprofile in the column.The temperature profilecan also be created in asimilar manner.Congratulations! You havefinished the race and you’re probably not even half as tiredas this guy, he looks beat.Now you can entercomponents, feed streams,column data and generateresults for all of your own simulations. Feel free to bragto all of your friends nowabout your superior knowledgeof Radfrac, you’ve earned it.You are truly a champion.Peace and Love,Bj。