Distillation: Exam task (Ethanol)

[@klasikindo]

you are a good teacher thank you

[@Meinan4370]

Bro I love you

[@leventali5491]

Dear Mr. Mattias, I watched all your uploaded videos and all are very useful in the field of process engineering, because mass transfer is one of the most important discipline. Based on my experience, many chemical engineering students are still confused about the difference between Azeotropic Distillation and Extractive Distillation. I kindly ask you if is possible to upload a new video with a Extractive Distillation and, also, about the difference between this two types of "special" distillations. Thank you and I apologize for inconvenience caused.

[@PLE_LU]

Hi and thanks for the nice comment, glad you find them useful. Thank you also for your suggestion Regarding upcoming priorities we usually have to prioritize rather. Currently we have _very_ strict priorities due to Covid-19 and the fact that all teaching now is distance teaching. I'm currently busy creating and uploading the last handful of videos for our course in Separation Processes (course code KETF10). At this point we do not know if distance teaching will continue and we haven't made any decisions on other courses. We will have to see what happens and if other teachers want to upload videos for their courses on our department KZbin channel. I also do not know by heart all details about our courses, e.g. exactly what kind of distillation is dealt with in our course in Sustainable Process Design. Due to time limitations we are unlikely to publish videos that are not closely linked to our courses or our research projects.

[@leventali5491]

Thank you so much for your kind answer!

[@tvndvne]

Thank you so much!

[@TobiasSchauer]

why is Rmin 0,76?

[@michielvaneersel5080]

I have a question: Now say that your feeding stream is for example a 50/50 mixture of tolueen and n-hexane. But that mixture is not that pure than you thougt, so for example it contains 10% water. What does this with your separation and how can you fix this?

[@PLE_LU]

McCabe-Thiele can only be used for binary solutions, so that's a completely different question than the ones we address in the two courses (KETF10 separation processes and KETF40 Mass transfer in environmental engineering) that this video is designed for. It also goes beyond my (i.e. Mattias who made this video) expertise. We have a different course, sustainable process design, that deal with distillation of non-binary mixtures, but we don't have any recorded videos for that course (at least not yet). Videos are planned, but it has not yet been decided if they will be published on our KZbin channel.

[@vivaldikonzsmith7291]

Can you please help me understand why q=0.75?

[@PLE_LU]

See kzbin.info/www/bejne/b5i9lpmqirOYoM0 q by definition equals (energy it takes to evaporate 1 mol of the feed) divided with (the evaporation enthalpy of the feed at the boiling point) thus q is the fraction of saturated liquid in the feed. (The fraction of saturated gas has already been evaporated, what is left to evaporate is the fraction of saturated liquid)

[@abdulwasi7411]

why did you drag q line into 0.75? not into -3

[@PLE_LU]

To learn how to draw lines of a certain slope, see kzbin.info/www/bejne/jKC9iquAmMeEhdU

[@amjadazeez4929]

I'd like to know the text you've used for the diagrams and equations. (:

[@PLE_LU]

Can you rephrase your question to help me understand what you want to know? Attempts to answer your question * The exam task solved is an exam task I once gave my students. * The equations I use are explained in the compendium I have written for my students (and they are also listed in the Handbook that our department and the department of Food Technology (Lund University) uses in several courses. (I'm the editor of that Handbook) However, you can find the same equations in several different standard textbooks on distillation * The diagrams I have created using matlab and data on phase equilibrium. I keep forgetting which mathematical model I used for which system (Van Laar or one of the others?) Experimental data sets on phase equilibria often state the goodness of fit for the different mathematical models, so I tend to go for the model that shows the best fit. There are, however, rules of thumb of which model to use depending on the characteristics of the substances, but to be honest that's not something I know much about.

[@amjadazeez4929]

Thank you for the swift reply. I found the equations in a textbook but, I'm having trouble finding some of the graphs used such as the one represented under 'Estimating fraction of eq. stages' in this video. Is it possible to access the handbook online? (I need to reference some of these in my thesis as well)

[@PLE_LU]

Sorry, neither our Handbook or my compendiums are available online. The calculation of fraction of equilibrium stage is a standard used in many text books on distillation. As far as I know, no-one is claiming that the method has a particularly solid theoretical foundation (It mimics the definition of the Murphree tray efficiency, but the overall tray efficiency is a lumped parameter, so there is no guarantee that it will give you an accurate result. On the other hand, McCabe-Thieles graphical method uses a few simplifications anyway, so if you use McCabe-Thiele you should not expect an exact prediction of reality). What some textbooks say is that you should calculate the fraction both horisontally and vertically and take the average of the two. (Compare taking the average of the Murphree tray efficiencies for gas and liquid compositions respectively). So, if you're looking for a reference to a book regarding how to calculate fraction of equilibrium stage (for position of feed or total number of equilibrium stages), you should be able to find plenty of text books to refer to. If you're looking for an actual image to copy-paste into your thesis as an illustration, I hope you know that the basic idea behind copyright laws is that you're not allowed to use other peoples images without permission (even if you redraw them). Your university might penalize you if you break such rules so my standard advice to students is always: "If you're not sure if you're allowed to use an image/illustration: Either don't or ask your supervisor/examinor" With this particular illustration I would say the content is in the public domain (it is "common knowledge") and that you therefore do not break copyright rules if you make your own version. You thus shouldn't need permission, but if you feel a need for it, you can state that you have received my written permission to redraw the illustration. /Mattias Alveteg, Lund University

[@MrVBeez]

cheers