DWSIM-3.4/C2/Rigorous-Distillation/English-timed

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Time
Narration
00:00 Welcome to the spoken tutorial on Simulating a Rigorous distillation column in DWSIM.
00:07 My name is Kannan Moudgalya.
00:10 In this tutorial, we will carry out a rigorous simulation of a Distillation column.
00:15 We will learn to specify column pressure profile.
00:20 We will see where to specify tray efficiencies.
00:23 We will check whether the product compositions are as desired.
00:29 We will also learn how to view the column profiles.
00:34 To record this tutorial, I am using DWSIM 3.4.
00:39 To practice this tutorial, you should know:
00:41 How to open a simulation file in DWSIM
00:45 How to add components to a flowsheet
00:47 How to select thermodynamic packages
00:51 How to add material and energy streams and specify their properties.
00:57 Our website spoken tutorial dot org gives details of the prerequisite tutorials.
01:05 You can access these tutorials and also all the associated files from this site.
01:12 This slide shows the problem solved in one of the prerequisite tutorials.
01:17 This was solved using shortcut distillation.
01:23 Let us open the corresponding file in DWSIM.
01:28 I have already opened DWSIM.
01:31 I have already loaded the file shortcut dash end dot dwxml.
01:38 This file is available to you for download from our website spoken tutorial dot org.
01:45 Let me save this as "rigorous".
01:58 You can see that the file name has changed now to "rigorous".
02:03 Click on the Configure Simulation button.
02:06 Below the Thermodynamics tab, locate the Options menu.
02:13 Let me click it.
02:15 In the white space above it, you get an option called Units System. Let me click it.
02:22 Locate Pressure on the right hand column.
02:26 To see that, let me bring this here.
02:30 Change its units to atmosphere.
02:35 Similarly, change the units of Delta_P also to atmosphere.
02:42 Change also the units of Molar flow rate to kilo moles per hour.
02:50 Click on Back to simulation.
02:53 Let us switch to the slides.
02:56 The file we opened just now in DWSIM, solves the problem in this slide.
03:02 The solution is given in the next slide.
03:05 This problem was solved in the spoken tutorial on shortcut distillation.
03:11 These values form the basis for the rigorous distillation column problem.
03:17 You may want to write down these values in a piece of paper.
03:20 We will be using these values shortly.
03:24 Let us begin by replacing the Shortcut column with a rigorous distillation column.
03:31 Let me go back to the simulation.
03:33 Press right-click on the Shortcut column and delete it.
03:40 Answer yes to the prompt.
03:43 Locate the Distillation column in the Object Palette.
03:46 Click on it and drop it in the place of shortcut distillation column.
03:52 You may have to adjust its position.
03:55 Click the column and select it.
03:59 Go to the Selected Object window.
04:02 Under the Properties tab, locate the Connections menu.
04:05 It is the third item.
04:08 In this, we can see Edit Connections. Click on it.
04:13 Immediately after clicking it, a button appears at the right extreme;
04:16 a button with three dots, click on it.
04:21 Now, there is a pop-up window.
04:23 Under the Feeds menu, click on the + (plus) button which is the Add button.
04:29 Under To Stage column, the option is Condenser by default.
04:36 Here, we have to specify the stage at which the feed enters.
04:41 Click on the arrow next to the Condenser.
04:44 In my version of DWSIM, I had to click a second time.
04:49 We can see the list of stages.
04:51 Select the stage where we want the feed to enter the Distillation column.
04:57 Here we select Stage_6.
05:00 Now, we will select the material stream.
05:03 Click on the down-arrow below the Stream menu.
05:08 You may have to click this also twice.
05:10 Click on Feed.
05:12 We have done the pairing that the Feed should go to Stage_6.
05:17 The actual connection will be done later in the flowsheet.
05:22 This is as per the solution we got in the shortcut distillation column.
05:27 Let us see it in the slide, we see the optimal feed location to be six.
05:31 Let us go back to DWSIM.
05:35 In a similar way, we have to pair the product streams.
05:39 Pair the Condenser to Distillate,
05:42 pair the Reboiler to Bottoms.
05:46 Now, we will connect heat duties to reboiler and condenser.
05:50 Pair C-Duty with Condenser and R-Duty with Reboiler.
05:58 We will now convert all the pairing into connections.
06:02 Click on any one of Feed or Condenser or Reboiler.
06:09 This completes the connections indicated by pairing.
06:14 We can move this and check.
06:17 You can see the connections have been made.
06:21 Let me close this.
06:24 Let me shift some streams to make it look more beautiful.
06:35 Click the Column and select it.
06:37 Under Properties tab, locate the Column Properties section.
06:43 It is the first option.This section is used to specify the various attributes of a Distillation Column.
06:51 In this section, the first option is Condenser Pressure.
06:55 By default, it is 1 atmosphere.
06:59 We will leave it as it is.Next is the Reboiler Pressure.
07:04 I will change its value to 1.1 atmosphere.
07:09 Using this, I will show how to establish a linear profile in the column.
07:16 Locate the Number of Stages option next.
07:20 You have to enter the total number of trays here.
07:24 Enter 15 here.
07:27 Because, this number includes the condenser also in DWSIM.
07:32 We plan to use a total condenser.So, this number should be one more than the equilibrium stages given by shortcut method.
07:41 We got the equilibrium stages to be 14 from the shortcut method.
07:47 We can see it in the slide.
07:50 Let us go back.The next option is Edit Stages. Click it.
07:57 Press the button at the right extreme.
08:01 It shows the condenser and reboiler pressures at 1 and 1.1 atmosphere.
08:08 These are the values that we entered just now.
08:12 The new stages that have been added have been assigned zero pressures which is incorrect.
08:20 We would like, infact, all the intermediates stage pressures to take interpolated values.
08:28 Go to the left column and click the interpolation symbol at the bottom.
08:35 Immediately, linearly interpolated values are assigned to every stage.
08:41 One may also change the pressure in any of the stages one through thirteen.
08:47 For example, I will click this pressure and change it to one (1) atmosphere.
08:56 Let me undo this by pressing the interpolated values again.
09:02 This is a very useful and important method.
09:05 Whenever the number of trays changes, you will have to press the interpolate button.
09:10 If you forget this, there could be a lot of problems.
09:14 For example, there could be negative flow rates.
09:18 Remember to do this in Assignment 3, at the end of this tutorial.
09:22 One may also change the efficiency in one or more stages, as given here.
09:30 Close this popup.
09:32 Next we have the Condenser type.
09:35 For that, we have to go up.
09:38 By default, it is Total condenser.
09:41 We will leave it as it is.
09:44 Next we have Condenser Pressure drop in atmosphere. By default, it is 0.
09:49 We will leave it as it is.
09:53 Next we have Condenser Specifications.
09:56 Under this menu, we have the type as Stream_Ratio by default.
10:03 Below this, we can see the Value menu.
10:07 Click on the field besides it.
10:10 Enter the required Reflux ratio.
10:13 Here we enter it as 2.
10:16 Recall that the minimum reflux ratio from the shortcut distillation was 1.47.
10:26 By multiplying 1.47 by 1.3 and rounding it off, we get 2.
10:33 Next we have Reboiler Specifications.
10:38 Under this menu, we have the type as Product Molar Flow Rate by default.
10:47 Change the units to kmol/per hour, if necessary.
10:55 We see the Value menu.
10:58 Enter the required Molar flow rate. Here we enter it as 61.1.
11:05 This is suggested by the shortcut solution.
11:09 We can see it in the slide.
11:13 Now we will select the solution method.
11:17 Locate the Solving Method option from the Properties tab; it is item 7.
11:26 Click on the field besides it.
11:30 Click on the arrow on the right extreme.
11:33 We can see a list of solving methods.
11:36 Select WangHenke_BubblePoint.
11:41 Now we will run the simulation.
11:43 To do this, go to the calculator options.
11:47 Click on the Play button.
11:50 Now click on the Recalculate All button.
11:55 When the calculations are completed, click the product compositions.
12:01 Choose a stream, for example, distillate.
12:05 You know how to check the product compositions from the molar compositions option.
12:15 Now, click on the Distillation column.
12:19 Under Properties tab, locate the Results menu. It is item 8.
12:27 This shows all the required results like Condenser Duty, Reboiler Duty and Column Profiles.
12:34 To see the Column profiles, click on it.
12:39 We can see the button appearing on the right extreme; click on it.
12:44 Now we can see the pop-up window.
12:46 We can see the temperature and pressure profiles,
12:51 Flows profiles,
12:53 Component flows and Component fractions.
12:58 If you want to know the exact numbers, use the Table tab to the right of the Graph tab.
13:07 Let me close this.
13:10 Let us save this file.
13:15 Let me summarize.
13:17 We learnt how to simulate a rigorous Distillation column,
13:21 Specified pressure profile,
13:23 Found out where to give tray efficiencies,
13:26 Verify column profiles.
13:30 Let me give some assignments.
13:33 Repeat the calculations for a constant column pressure of 1 atmosphere. That is, with reboiler pressure = 1 atmosphere.
13:42 Do you see major changes in the results?
13:46 Next, simulate the distillation column at a constant pressure of 1 atmosphere. That is, the reboiler pressure also is at 1 atmosphere.
13:55 If the reflux ratio is increased beyond 2, does the purity improve?
14:01 What reflux ratio should you use, if the actual purity is as desired.
14:07 In a future tutorial, we will show how sensitivity analysis can help do this easily.
14:16 In the next assignment, we simulate the column at a reflux ratio of 2.
14:22 Keep the column pressure constant at 1 atmosphere.
14:24 Increase the total number of trays by 1, that is, from 15 to 16.
14:31 As the number of trays has changed, you have to use the interpolate option.
14:36 This was mentioned earlier also.
14:38 With a larger number of trays, has the purity increased?
14:44 In the next assignment, verify the following relationship:
14:48 Composition of vapour flow to the condenser = distillate product composition.
14:54 Explain why this equation has to be satisfied.
14:58 In the next assignment, check the consistency of the variables of the reboiler.
15:03 Use compositions, temperature and pressure at the reboiler for this purpose.
15:10 Do this through an equivalent flash calculation.
15:15 In the last assignment, solve the problem by different Solving Methods.
15:20 Compare the results.Compare the computation times.
15:25 We have come to the end of this tutorial.
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