Discussion Central

  • 1.  Separations, Distillation vs other options

    Posted 09-08-2019 11:50
    Cynthia Mascone's editorial (August 2019 CEP) highlights the debate on the future of separations, specifically distillation vs other options.   When I was in school, >35 years ago there were claims distillation was mature and would be surpassed by new unit operation similar to  points raises in the recent NASEM report.  I find the current thinking as flawed now as it was then.   Yes we all know the energy intensity of distillation but that is only one aspect.   Separations are often a major part of the capital and operating cost of a plant.  There are many factors in choosing a separation scheme. But what is often neglected in academic dialogs is the absolute requirement to be robust.  Industry is risk adverse for good reason.   If the separations fail, the plant fails.  Building a billion dollar plant that doesn't work will bankrupt most companies.  However that does not mean industry is stagnant and hasn't explored, alternative technologies over the decades, especially when energy prices spiked to >$10/mbtu.  It just means they don't win.   While there has been advances in membranes, and other alternative, when you look at capital efficiency, operating cost (including energy) and reliability, distillation is compelling.  This is especially true when you employ heat integration, process intensification, divided wall columns and other advanced concepts.  To educate future students that the "forefront of separations isn't distillation" in my opinion is misguided.  There is an analogous and equally troubling trend  in neglecting the importance of thermodynamics in energy discussion.

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    William Banholzer
    University of Wisconsin- Madison
    Madison WI
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  • 2.  RE: Separations, Distillation vs other options

    Posted 09-10-2019 07:35
      |   view attached
    I agree with Professor Banholzer's observations. There was a very nice summary of Available Separation Technologies in a paper (I believe so) by George Keller in a Supplement to The Chemical Engineer (publication of IChemE, UK) circa 1981. I had adapted it for my classroom course on Separation Technologies at the Instt of Chemical Technology, Mumbai, India. (This is attached with a citation that I don't remember clearly-there were no pdf versions at that time). This is a plot of Technological Maturity vs Use Maturity. Obviously Distillation was (& is) given the top billing. There are no numbers for x & y axes only 2 stages, Invention/First application and Asymptote. Distillation occupies a position very close to the top right corner showing Asymptote-indicating that improvements are still possible.
    We should remember that Distillation consumes a major chunk of Energy that the CPI uses. Therefore, even a 0.1 % improvement in energy efficiency can result in tremendous savings in absolute terms. As Dr Bravo's paper in CEP suggests R&D opportunities in Distillation are plentiful and the returns obviously will be commensurate.
    So let us not forget Distillation !

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    Vishwas Pangarkar PhD
    Retired Professor of Chemical Engineering, University of Mumbai, India.
    Currently: Independent Chemical Engineering Academic/Professional.
    Nasik-422013, India.
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    ppt
    Available Separation Technologies.ppt   39 KB 1 version
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  • 3.  RE: Separations, Distillation vs other options

    Posted 09-18-2019 00:47
    I am greatly surprised that there are just two comments on this very important issue. We should certainly appreciate participation from a larger section of the ChE fraternity.

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    Vishwas Pangarkar PhD
    Retired Professor of Chemical Engineering, University of Mumbai, India.
    Currently: Independent Chemical Engineering Academic/Professional.
    Nasik-422013, India.
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    Original Message


  • 4.  RE: Separations, Distillation vs other options

    Posted 09-18-2019 01:32
    Hi, Professor Pangarkar.  I agree with you, I was looking forward to more comments on this thread.  I know that researchers are experimenting with 3D printed column structures that have better performance than traditional packing or trays in columns.  But I think a lot of effort goes into tweaking current processes and some of them are around for mostly historical reasons.  There may be room for revolution in some areas.

    As an aside, in North America, when people see the word "fraternity" they think of a university club that only men can join.  Some might have taken your comment to exclude female chemical engineers.  In India I think fraternity means a group of people with a common interest.  I don't want you to be tarred with a sexist brush if you don't deserve it.  :)

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    -Kirsten

    Kirsten Rosselot
    Process Profiles
    Calabasas, CA United States
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    Original Message


  • 5.  RE: Separations, Distillation vs other options

    Posted 09-18-2019 02:20
    Hello Kirsten,
    The Oxford Dictionary defines "Fraternity" as " A Group of People sharing a common Profession or interests" as you rightly point out. We in India generally follow the UK English & therefore I meant EVERYBODY in the ChE Community. I beg everybody's pardon if there is any other interpretation (which I did not mean) of the term Fraternity. I have checked Oxford Dictionary again and indeed it does include the following subsequent to what I noted above: "N. Amer. A male students' society in a  University or college" as Kirsten explains. This is definitely a revelation to me. I thank you for pointing out a major difference in the meaning of this term. I will have to be careful next time I post anything.
    So let us have comments from everyone who wants to contribute !

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    Vishwas Pangarkar PhD
    Retired Professor of Chemical Engineering, University of Mumbai, India.
    Currently: Independent Chemical Engineering Academic/Professional.
    Nasik-422013, India.
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    Original Message


  • 6.  RE: Separations, Distillation vs other options

    Posted 09-18-2019 19:54
    Hi,

    Whenever a tech is proposed, we should look at it against the Hype Cycle or the Dunning-Kruger effect..... Both based on past discussions and projections into the future. It's a joyful way of learning and keeping things in perspective.

    May be the experts can create one. Thanks,

    Regards,
    Pavan

    ---------------------------------
    Pavan Kumar Naraharisetti
    Assistant Professor
    Newcastle University in Singapore
    Singapore
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    Original Message


  • 7.  RE: Separations, Distillation vs other options

    Posted 09-19-2019 12:20

    Plead ignorance to the Hype Cycle or the Dunning-Kruger effect. Please enlighten.

     

    Privileged to have Professor Pangarkar as one of my teachers, I can vouch for the fact he treated everyone equally. Fraternity is to be taken to mean community here.

     

    On to the topic of discussion though: it seems there is some thought to minimize teaching of traditional (and still dominant) unit operations of distillation, absorption and extraction, while trying to squeeze in bioseparations and such in the separations course. The attempt is to cover these three in the chemical engineering thermo course (thermo concepts in turn shoe-horned into material/energy balance course), to make room for emerging separation techniques. I think this does a great disservice to the students by negatively impacting all three courses.

     

    Vivek Utgikar, PhD PE

    Professor, Department of Chemical and Materials Engineering

    Associate Dean of Research, College of Engineering

    University of Idaho

    875 Perimeter Drive, MS 1021

    Moscow, ID 83844-1021

    Phone - (208) 885-6970; Fax (208) 885-7462

    vutgikar@uidaho.edu

    webpages.uidaho.edu/vutgikar

     




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  • 8.  RE: Separations, Distillation vs other options

    Posted 09-20-2019 09:20
    Community members,

    It is surprising to note that chemical engineering definition starts and ends with an oil & gas perspective. Distillation may be an important separation process, no doubt about it. But it is not the only thing about separation. 
    In the industrial biotechnology arena where important products from bio-pharmaceuticals, bio-chemicals, bio-materials are being manufactured, distillation as a separation phenomenon is unheard of.  The phenomenon is chromatography and membranes. In a world of yeasts, cells and microbes, you don't need a scale of distillation. The business maturity of bio-technology is now no longer done in few labs by eccentric scientists, but a matured industry in terms of few billions of USD businesses globally. Now it encompasses plastics and renewable technologies also. Add the pharmaceuticals businesses globally, it will surpass the oil & gas business .
    Bio-chemical engineering scale-up is a challenging subject in its own and does not require understanding of only distillation as a separation phenomenon.
    The perspectives of chemical engineering does not begin and end with only oil & gas industry and distillation as a separation process.

    Sorry, I can't agree with the majority of the view points.

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    Eur Ing Santanu Talukdar CEng CSci MIChemE SMAIChE
    Chartered Chemical Engineer
    Independent PAT consultant
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    Original Message


  • 9.  RE: Separations, Distillation vs other options

    Posted 09-21-2019 01:29
      |   view attached
    We need to clear a misunderstanding. None of us has suggested that oil & gas (also distillation) is the only thing that needs focus. On the other hand in my original comment I have specifically concluded : "So let us not forget Distillation !"
    All the separation processes that Mr Talukdar mentions (Chromatography, Membrane separations) and some more (affinity separations, field induced separations, supercritical extractions, etc) are included in my PPT slide which I had attached to the original comment. Some of the separations in the lower left corner would have moved to higher x and y values over the last 2-3 decades. However, these other separations certainly cannot compete with the Technological/Use maturity of distillation. The point that was made is there is a wrong notion that distillation has reached the zenith in technological maturity. My argument was that nothing is perfect and distillation still needs attention because of its sheer scale of operation and potential for energy saving. I am re-sending the above referred PPT slide for ready reference.

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    Vishwas Pangarkar PhD
    Retired Professor of Chemical Engineering, University of Mumbai, India.
    Currently: Independent Chemical Engineering Academic/Professional.
    Nasik-422013, India.
    ------------------------------

    Attachment(s)

    ppt
    Available Separation Technologies.ppt   39 KB 1 version
    Original Message


  • 10.  RE: Separations, Distillation vs other options

    Posted 09-19-2019 02:33
    I have been a practicing chemical engineer for over 50 years, and remain very active in troubleshooting and enhancing industrial distillation operations for hydrocarbon and complex chemical mixtures.  In my opinion, a very real problem is that chemical engineering faculty have trouble obtaining government or industry support for work in this area and so are unable to generate sufficient interest in their graduate students to pursue research in this extremely important industrial unit operation.  I know many faculty who have no interest in this subject, or in the thermodynamics of phase equilibria.  An unfortunate consequence is that fresh graduates often have an insufficient grasp of this vital aspect of plant operations.  There is a widespread, but highly erroneous, notion that these areas have reached a high level of maturity and are not worthy of serious academic attention.  I have also noticed that this issue is more pronounced in the USA than in Europe.

    No one would quarrel with the development of ideas for energy-efficient processes that compete with distillation.  However, the fact remains that distillation remains, by far, the best and most widely used option both for continuous and batch processes.  As others have noted, there are very good and practical reasons for this, and we continue to witness many recent developments.  For my part, I would be happiest if we saw closer industrial collaboration with, and funding for, chemical engineering education in this area.  I know several major corporations that have to devote intense efforts to train fresh recruits in areas, such as distillation and thermodynamics, that should have been emphasized more intensively in their undergraduate programs.

    Another aspect that has concerned me over the years is the widespread, but premature, dissemination of process simulators to undergraduates who have not yet mastered the fundamentals.  The ease of use of these tools often fosters a false sense of confidence, and one often sees examples of poorly conceived process simulation models or improper selection of thermodynamic options, especially with complex chemical processes. These generally result in a questionable match against plant data, even for steady-state models.

    The last issue I wish to mention is dynamic simulation: these models are an order of magnitude more complex than those at steady-state.  Since the behavior of all real-world processes is essentially time-dependent, dynamic simulation is far more effective in improving our understanding of "what-if" questions in process dynamics.  This is extremely useful for improving the configuration, design, and tuning of regulatory and advanced process control systems, and also has important implications for plant profitability and process safety.  It is worth noting that the quality and robustness of several commercial products is not quite where it should be when it comes to dynamic simulation of chemical processes, especially in distillation with simultaneous chemical reaction.







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