Archived-Announcements-2012

From Separation Processes: 4M3
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  • Final grades have been posted on Avenue. Please ignore any calculated value from Avenue, and only read the ACTUAL GRADE value, which represents the integer-rounded grade that will appear on your transcript. Conversion to letter grades will be done using the standard system.
    • Confirm your grade calculation with this spreadsheet
    • Class average = 74.9% (median = 77.5)
    • Class standard deviation = 12%
    • Grades are perfectly normally distributed, no curving of grades was done or required.
  • Grades for all assignments, the project and the midterm are now posted on Avenue for 4M3. These grades should agree with your paper copies. Any corrections made by the TA or myself should also be shown correctly now.
  • A note about the final exam.
  • All solutions to the assignments and midterms are posted to assist you while studying.
  • Assignment 5 (updated on 27 November) is posted.
    • All 4 questions are now posted for this assignment.
    • Question 3.3, part (c), the solvent flow of 15kg/hr is impossibly low. Use a revised value of 27.5 kg/hr.
    • Please note that in question 1 it is not acceptable to use the Lineweaver-Burk plot method to calculate the isotherm parameters. See the course notes for a better method: the Eadie-Hofstee method.
    • Note the ternary diagrams in question 2 and 3 are different.
    • You may scan in your diagrams (make sure the resolution is of good quality) and submit electronically.
    • Important: assignments must be submitted by 16:00 on Monday (03 December) electronically or in the Chemical Engineering dropbox. No late hand-ins will be accepted.
  • The class for 4M3, on Friday (30 November), will be the course wrap-up lecture. It is also the last chance to pick-up any old assignments and midterms: I will bring them to class everyday on Tuesday, Thursday and Friday; after that I will destroy uncollected material, unless you make an alternative arrangement with me.
  • The midterms are available for pickup in class or from my office. Grades are now posted to Avenue. I've had a chance to analyze the data:
    • The average grade for the midterm was 71.2 (median was 72) with a stdev of 13.9, which is a little higher than I prefer. The distribution is mostly normal, with a slightly heavy left tail. There is nothing in the grades to warrant adjustment (i.e. "curving").
    • Assignment 5 has sufficient bonus grades to boost your grade; in addition to the take-home exam that's been dropped and course grades redistributed.
    • As mentioned in class, I apologize for the delay in grading. Overhauling this course while teaching it for the first time, and teaching 4N4 for the first time has just used up all my spare hours.
    • For issues regarding the midterm grading, please see Kevin regarding questions 3, 4, 7, 8, 9, and see Daryl for the others.
  • If you prefer not to appear in any of the presentation course videos, please send me an email by Saturday and I will edit you out and replace the video. Videos are hosted on a 3rd party server, so I cannot restrict access to McMaster only.
  • Due time for presentations is now 7pm the day before: no exceptions after that. Future groups, please make sure your names appear on one of the slides. Thanks.
  • Important announcement regarding the take-home midterm and assignment 5. From speaking with your class members, I've realized this term is just too crazy with final projects and hand-ins in your other courses. The value you will get from a take-home midterm is about that from a large assignment. Rather than having your do the take-home midterm and assignment 5, I'd rather you do one thing well. So I'd rather you do assignment 5 (which will be posted soon), so you have seen an equal number of questions from all topics in the course. The take-home would have covered the entire course and be more computer-based questions, while assignment 5 will focus only on recent material and be more hand-written questions.
So with the take-home cancelled, this leaves 10% of your grade unaccounted for. Here's what I will do:
Drop the take-home midterm and transfer its 10% overall course grade to:
    1. the final exam, OR
    2. spread it out equally over the entire course (i.e. divide your final percentage by 90 instead of 100)
NOTE: you don't pick the option, I will give you whichever option gets you the higher final grade, on an individual basis. So some people will have option 1 and others option 2, which ever benefits your more. This obviously makes grading a bit messy for me, but I think it will work OK.
Note that assignment 5 will still be optional as described above, but I strongly recommend you do it.
  • As announced in class, assignment 5 will be optional. The grades for the assignment portion of the course will be best 4 assignments submitted, so each assignment counts 5%. Now I will make the deal even better for you: if you submitted 5 assignments over the semester, then the assignment that was not used in the best 4, will be a bonus grade, weighing 5%. Example:
    • you submit 5 assignments and got: 50%, 60%, 70%, 80% and 90% respectively
    • the assignment portion of your course grade will be (60+70+80+90)/4 x 0.20 = 15%
    • you get a bonus grade of 50 * 0.05 = 2.5%
If you hand in 4 or fewer assignments, then there is no bonus grade. This is one way you can boost your grade if you didn't do so well in the midterm.
  • Based on the large volume of questions I've been getting regarding the course project makes me realize that some extra time and input is required from me to guide you.
    • I rather you do this project properly.
    • I propose we cancel the teaching part of class on Thursday and Friday. However, I will be in the MDCL room 1110 for any questions regarding your project and presentation during the class hours.
    • The timing also works well, because there isn't enough time to start and finish the next section of the course before the presentations.
    • The project submission is shifted to Sunday night by midnight (i.e 23:59 on Sunday) to allow you to act on any feedback.
  • Some questions have been asked about the project report, so I've updated the page:
    • particularly on line spacing
    • the coverage required for capital and operating costs
    • the dates on which you will present (dates were selected to avoid clashes with 4N)
    • the presentation format for slides.
  • For those modelling processes that are "difficult", such as distillation columns, and for which computer software exists to do your mass and energy balance, please use the software (e.g. Hysys and Aspen). But then your project still has substantial work on designing the column size, and internals of the unit. Here are 2 examples of project reports
  • For those groups struggling to find information regarding sizing of your project equipment, please check Perry's and the other references suggested on this website.
    • Perry's tends to have very practical sizing information and examples.
    • Industrial and Engineering Chemistry Research often has rate expressions and lab data which is useful.
    • New: Another interesting reference I came across today that will help is in the book "Rules of Thumb in Engineering Practice" by Don Woods. It contains a lot of typical size and flow rates for many units, including many separators. Check out the table of contents online.
    • A useful article on designing and understanding adsorbers has been posted.
  • Avenue grades have been added now for all question, except question 3.
    • The midterm median, without question 3 that's not been graded yet, is 76%, which is right on target.
    • Question 3 will take me a while to grade, so expect midterms returned the week of 19 November. I apologize for the delays, but 4N4 and 4M3 are keeping me (and you) super busy.
    • Please address any discrepancies regarding assignment grades with myself right away. Waiting until the end of the term is too late.
  • Important: parts of assignment 4 will be covered in class on Tuesday. Assignments must be submitted by the start of class on 6 November.
  • Some hints and an update for assignment 4, question 5:
  • The \(A_\text{salt}\) and \(A_\text{solv}\) terms are not the area of the membrane: they are the permeances of the salt and solvent respectively. This unfortunate notation is widely used though in most texts.
  • There is a correction, the feed concentration should be 2.5 g NaCl per liter in the feed (not 2.5 wt% NaCl). I apologize for wasting your time for those of you that have been iterating with negative concentrations.
  • And another hint. I found a way to solve question 5 that leads to faster convergence:
    • Specify \(C_F\) and \(\theta\)
    • Guess \(C_R\) instead
    • Calculate \(C_P\) from equation 5
    • If your calculated value of \(C_P\) is negative or exceeds \(C_F\), then repeat your guess for \(C_R\), until you get a \(C_P\) that lies between 0 and \(C_F\) and double check also that the rejection coefficient from this \(C_P\) is reasonable, around 90 to 99%.
    • This approach to estimate \(C_R\) and then \(C_P\) will get you really close to the final answer.
    • Now carry on with the rest of the steps in the notes. It's interesting how simply flipping what you guess first leads to much faster convergence.
    • If you iterate and get a negative value for \(C_P\) or \(C_R\), it simply means that you must decrease your guess for that term, since you obviously can't have a negative concentration.
  • And a final hint: this question is much better to solve on a computer, with goal seek, than by hand. There is tremendous sensitivity to initial guesses, so solving by hand will take too long.
  • For question 2(B), part 3: by definition, optimization implies we have excess degrees of freedom, i.e. more unknowns than equations. You should get a system of 3 unknowns (including \(A_1\) and \(A_2\)) and 2 equations. Set the 3rd unknown to various values (between its lower and upper bound), and solve for \(A_1\) and \(A_2\). Pick the solution that gives the optimum.
  • Updated: Feedback about your course project outline has been sent. Feel free to reply with any comments, otherwise, you should have started collecting the information you need to work on your report, such as equations on how to design the separator and capital & operating costs.
  • Important note: there will be no teaching on Friday (02 Nov), 08:30 to 09:20.
    • I will be at the class though to answer any questions regarding assignment 4.
    • There will be a tutorial-style question (slide 58) that you can ask questions on. This question will be in assignment 5 ... so get a head start.
  • Some changes to deadlines, based on student requests (due to other course loads):
  • The slides from Friday (26 Oct) have been updated - all the solutions are added to the slides. Please ensure you understand how to use the ternary diagram. Hint: there might just be a pop-quiz on Tuesday as part of assignment 5.
  • I am planning to cancel class on Tuesday morning, due to the bad weather. I will rely on the university's choice to cancel class, please check http://mcmaster.ca in the morning before class. Update at 630am: classes are going ahead on Tuesday.
  • For class on Friday (26 October 2012):
    • Make sure you watch and understand this video on ternary phase diagrams: the class is going to rely heavily on that.
    • I recommend you attempt the 5 questions in the course slides prior to class.
    • Bring a ruler, pencil and eraser to class to work with ternary diagrams.
    • Updated notes are available. Print slides 29, 30, 32 and 35 on separate, large pages.
  • Assignment 4 is posted - due later, on 01 November, as there are several midterms in other courses this week.
  • Important correction to the notes: slide 76, please make this correction: \(R = 1 - \displaystyle\frac{C_P}{C_F} \)
  • Read ahead: a highly recommended reading is chapter 8 on liquid-liquid extraction from Seader, Henley and Roper.
  • If you missed class on 18 Oct, please make sure to watch the video recording; Friday's class will not have too much time to recap before moving on. Here are some questions to think about before class:
    • What happens, in terms of osmosis, on a really hot day to fluid flow in a tree?
    • Is \(P_\text{solv}\) going to change if we use a different solute?
    • If we double the pressure drop, will we double the solvent flux?
    • Why did we not take osmotic pressure in account for microfiltration and ultrafiltration?
    • In RO: what will be the expected effect of increasing operating temperature?
  • The midterm solutions have been updated with question 3 included now.
  • Updated details regarding the course project are posted. Please note the deadline of 18 October for the project outline.
  • Thanks everyone again for your constructive feedback about the midterm. Once Daryl and I have graded the midterm I will make a judgement on how to adjust the grades, if required.
  • This anonymous comment was received from the course website:

Kevin,

Friday night's 4M midterm was too hard! More specifically, the 24 mark question was very unfair. It is material that was covered on Thursday - ONE day before the midterm! Its not fair to test us on this and make it worth 24 marks! Normally, our other profs give us at least a week to digest the material before it is covered on a midterm. Other than that, the question itself was tough and many of my colleagues also were confused by it. Basically, if we did not get this question, we automatically drop to 76%, not taking into account other mistakes.

Please - reconsider the marking allocation of this question !

The other thing - the midterm was way too long. I understand that you gave us extra time but 2 hours and 45 minutes is almost 3 hours - which is the duration of a final exam! This is not to be expected for a 15% midterm.

Those are some thoughts - I would appreciate your addressing them!

Thanks.
I appreciate and take any feedback seriously. I'm interested in whether this is one data point (1 student out of 80), or if these issues are of general concern. Feel free to message me via the course website to address the issues of whether question 3 was (a) unfair (b) confusing, (c) too soon; and lastly (d) whether the midterm was too long. I will discuss these in class on Tuesday.
In the mean time, please review the midterm solutions; I will take up question 3 in class on Tuesday. Please redo this question and hand it in at class on Tuesday morning as question 2 of assignment 4. You must do it on your own to maximize your learning. You may hand it in electronically if you cannot make it to class.
A membrane operating with pure feed of water produced a flux of 0.20 \(\text{kg.s}^{−1}\text{.m}^{−2}\); this was with a pressure difference of 20kPa. When operated with a protein-water mixture and a 20 kPa pressure difference, a flux of 0.04 \(\text{kg.s}^{−1}\text{.m}^{−2}\) was measured at steady state. What would be the expected flux for this same protein-water mixture, but at a pressure difference of 30kPa?
  • Clarification in question 1, assignment 3: please ignore the word "needle"; it is simply a rectangular object.
  • Slides for the guest lecture on membranes are now available. This material forms part of the course content.
  • Please note: the solutions to the assignment will be discussed in class on 9 October. Assignments MUST be handed in at the start of class.
  • Course project selection is starting. It is mandatory to fill out this form before noon, 27 September. Also note that topics will generally be allocated on a first-reserved basis.
  • There is a piece of information missing for Assignment 2, Q4: the volumetric flow rate coming in. What I will ask you to do instead, is please present your answer as a plot, showing the minimum particle size that can be removed (y-axis) as a function of the volumetric feed flow rate, Q, in units of ms−1, on the x-axis.
  • A great presentation on beer clarification, showing photos of the internals of the disk-bowl centrifuge. Notice the dimensions are similar to those we designed in class on Friday. As mentioned, here is a 10 page report on centrifuges for beer clarification. Course projects for this course will be similar.
  • The practice question in class is available: see the link to "Practice questions for tests and exams" on the main course page. More questions will be added there as the course progresses, so keep checking that page.
  • Given the clashes with other evening classes and with CSChE, the only feasible midterm date is Friday, 12 October at 18:30.
  • The second assignment is available; due on 25 September (date has changed).
  • Comments, questions, feedback? Don't wait for official course evaluations.
  • The first assignment is out. Due on 14 September. To clarify, in question 1, please state:
    • the box from the table (e.g. gas-gas)
    • the name of the unit (e.g. cryogenic distillation)
    • the input stream (air with mostly nitrogen and less oxygen)
    • the two or more output streams (high purity oxygen; high purity nitrogen; high purity argon; other mixed purity streams).
  • Please use the feedback page to let me know which evening works best for the midterm: 15, 16, 17, 18 or 19 October.
  • Also, if you didn't get a chance to let me know which separation unit ops you are interested in seeing covered in the course, then please let me know.
  • The first class is on Thursday morning, 08:30AM, in MDCL 1110. Please bring
    • the course outline, and
    • any thoughts on what you want to see covered in this elective course.