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