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Homework Help: Process Simulation Project- Gothenburg Refinery

  1. Dec 8, 2018 #1
    1. The problem statement, all variables and given/known data
    I am required to obtain the following
    1) Energy targets and pinch temperatures
    2) Composite Curves
    3) Grand Composite Curve with and without utilities?
    4) What utilities are you going to use to fulfill the energy targets? Why have you selected these utilities?
    5) Design a HEN that fulfills the energy targets
    6) Design a HEN that fulfills the minimum total costs
    7) What is the difference between the two HEN designed


    2. Relevant equations
    http://publications.lib.chalmers.se/records/fulltext/142245.pdf

    This link contains the process description.
    3. The attempt at a solution
    In this project, I am required to design a HEN for this distillation section of the process based on the process flow diagram In addition to the grand composite curves with and without utilities using ASPEN Energy Analyzer. But because I am not well aware of the process I can't identify from the stream data which streams are utilities and which are process streams
     

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  2. jcsd
  3. Dec 8, 2018 #2

    BvU

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    Not even after reading the 60 page thesis you attach to your post ? Do you expect us to work it through for you ?
    None of them at all ? Or can you designate some as definitely utility c q definitely process ? Which ones remain ? Does it matter ? If one process stream heats up another, then what ?


    What I miss here is your own attempt . . . (and please type, do not photograph pages of handwriting :smile:)
     
  4. Dec 8, 2018 #3
    I am not expecting anyone to read 60 pages, but there is part of it which is of relevance to me in solving the problem that is the process description. I am not confident in my understanding of the process and how the streams get heated to their target temperatures from just looking at the process flow diagram. I am sorry if my handwriting is an issue I just found it more convenient for me to post photos of my solution instead of typing. I am using ASPEN Energy analyzer software to design a Heat exchanger network drawing both composite curve and grand composite curve based on the stream data. In drawing the hot and cold composite curves we should not take into account the utility streams and from the data I cant figure out which is which?
     
  5. Dec 9, 2018 #4

    BvU

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    The idea is you make the process streams handle heating and cooling as much as possible and use utilities to take care of the remainder. Hence the focus on process streams in the curves.

    I don't want to rob you of the exercise (PF culture :smile:), so I think you should pick the list of process streams. Post it and we'll discuss. Start with #1 (that's a giveaway :rolleyes:). Another hint is in the colours used in fig. 14. But there it looks as if choices have been made already.

    Any specific questions left over after reading the 60 pages?
     
  6. Dec 9, 2018 #5
    Feed water streams 13,14,and 15 are not process streams instead they are used as cooling utility to cool the hot streams but I am not sure.
    "The crude oil is heated by a number of heat exchangers before entering the first furnace. This results in a preheated crude oil stream which decreases the energy demand of the furnace. The stream continues to the atmospheric distillation column where four different fractions are extracted".

    So stream 1A represents crude oil before entering the furnace and Steam 1B crude oil to the atmospheric distillation column, right?.
     
  7. Dec 9, 2018 #6

    BvU

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    I agree. In the sense: The waste heat from the 160 degree bitumen is used to provide feed water for some other steam boilers outside process battery limits.

    (just to caution you: I'm not a refinery expert either....) Aren't you lured into 'finding' the solution that's already worked out in fig 14 ?
     
  8. Dec 9, 2018 #7
    The stream continues to the atmospheric distillation column where four different fractions are extracted. Two of the fractions extracted from the AD column (stream 3 and 4) are led into pressure vessels where the gas and liquid are separated and the gaseous part is recycled to the column.
    Stream 3 is used to heat Stream 1 A in heat exchanger E-11.
    "The gas consists of volatile hydrocarbons and steam from the distillation column. To be able to extract only liquid hydrocarbons later in the process, stream 5 must be condensed. Cooling of stream 5 is achieved in two steps, first by heat recovery to preheat the crude oil and then final cooling in a water-cooler to reach the target temperature. Thereafter, the stream is separated and gas and liquid are led in different directions before further processing. The gaseous part goes to a separator where all the remaining liquid is separated (Nynas AB, 2011). The liquid part is sent to another separator where the water is separated from hydrocarbons in order to deliver a product which is led to a storage cistern". I think that stream 5 A is the stream that exchanges heat with stream 1 A and 5B is the stream that is cooled in a water cooler. 5 C represents the stream sent to the separator. But I am not sure.

    No, the ultimate goal is to design a HEN that fulfills the energy targets and design a HEN that fulfills the minimum total costs as well but I don't understand the differences between these two requirements if the utilities employed in the HEN that fulfills the minimum total costs would satisfy energy targets
     
  9. Dec 10, 2018 at 3:06 AM #8

    BvU

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    I find it all rather a big assignment and have trouble discerning what is expected of you, other than repeating the work in the thesis.

    @Chestermiller, can you provide a suggestion ?
     
  10. Dec 10, 2018 at 3:14 AM #9

    BvU

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    However, from the color in fig 14 it looks as if the streams themselves are considered within battery limits (to reduce cooling water use). Quite unclear where the 160 degree target temperature for the bitumen occurs (before or after the steam generator ?). Perhaps you can start marking the temperatures from the very incomplete stream table in the appropriate places in fig 14 ?
     
  11. Dec 10, 2018 at 5:46 AM #10
    I found the link on the internet and it was not given to me as a guide for understanding the process, what was given instead was the process flow diagram and the stream data and we are required to obtain the requirements in my first post.
     
  12. Dec 10, 2018 at 7:11 AM #11
    I'll take a look, but it seems like it would involve a lot of work to help with this.
     
  13. Dec 10, 2018 at 11:51 AM #12
    It seems to me all the streams in the figure are process streams except the ones related to water: cold water, 13, 14, 15, steam to boilers, steam, separator water.
     
  14. Dec 15, 2018 at 5:49 AM #13
    I constructed the composite curve and determined the ideal minimum cooling and heat requirements as 3811 KW and 3648 KW respectively and the pinch temperature at 252 degrees Celsius. I also Constructed a GCC but I don't know how from Energy Analyzer one can find the temperature interval where the GCC bends back on itself in order to figure out where to set utility targets. I also don't know on what basis should I select the utilities given in pastedImage (2).png, Should we choose the utilities with the least cost per energy in order to satisfy the cooling and heating requirements. Are streams 13, 14, and 15 we excluded cold utilities we should employ in my HEN design and GCC?
     

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  15. Dec 15, 2018 at 7:44 AM #14
    I'm going to ask a friend of mine with a lot more process experience than I do to help out.
     
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