Results 1 to 4 of 4
  1. #1

    transfer line vaporization

    Hi everyone,
    We have a naphtha/diesel/Gasoil distillation unit, and distillation expert give us the entire simulation in ASPEN Plus. The distillation tower seams to work; I know that we need from 3 to 10% of overflash that according our heavy naphtha 91% is just fine.
    Nevertheless, the transfer line, from heater to column have also 91% of vaporization, and our company design manual says that we must to take care of vaporization (not up to 60%) to avoid heater coking. Now, some other process engineers are proposing to put a control valve in the transfer line to help the expansion and vaporization in that point, which I haven’t seen before in other facilities.
    Besides that I just have the VDU transfer line criteria to design with critical velocity, even though I haven design one. The actual path of this line has horizontal and vertical stretches instead the shortest ride with different diameters.
    That’s why I ask you:
    1. It is possible to have more than 60% of vaporization outside the heater, taking care the film temperature of the heavy naphtha?
    2. To put a control valve in the transfer line is correct?
    3. What design criteria I should follow to design transfer line in this kind of facilities?
    The plant is new, the heavy naphtha comes from gas that goes to a Cryogenic Plant.
    Thanks in advance for your help.


    See More: transfer line vaporization

  2. # ADS
    Spons Circuit
    Join Date
    Always
    Posts
    Many
     
  3. #2

    Re: transfer line vaporization

    (1) Before you do anything, I strongly recommend you check the feed heater design for outlet degree of vaporization since you should never exceed it in operation (you can formally rerate the heater if necessary)

    (2) The degree of vaporization is usually Wt%. If you are using Vol%, suggest you use the wt% in your post (91 Wt% vaporization is very very high)

    (3) VDU transfer line design criteria is never used for other refinery heater transfer lines.

    (4) Adding a control valve to the transfer line will probably force you to add a new relief system upstream.

    (5) you need to describe your distillation system in more detail before I can help you.

    My threads; sazeg :


    •    Sponsored Links



      -

    • #3

      Re: transfer line vaporization

      (1) Before you do anything, I strongly recommend you check the feed heater design for outlet degree of vaporization since you should never exceed it in operation (you can formally rerate the heater if necessary)

      (2) The degree of vaporization is usually Wt%. If you are using Vol%, suggest you use the wt% in your post (91 Wt% vaporization is very very high)

      (3) VDU transfer line design criteria is never used for other refinery heater transfer lines.

      (4) Adding a control valve to the transfer line will probably force you to add a new relief system upstream.

      (5) you need to describe your distillation system in more detail before I can help you.

      My threads; sazeg :


      • #4

        Re: transfer line vaporization

        Thank you for your response. Yes, I'm agree with you, unfortunately is 91%wt, that's why I'm concerned. I have not noticed the point about the addition of a new relief system, and that is a good point to discard the control valve.
        In my process we receive heavy naphtha, to obtain light naphtha, diesel and heavy gasoil. It is similar to a CDU, with preheating, flashing, furnace heating, distillation (with its top condensation), and a lateral striper column distillation for diesel product.
        In the heavy naphtha preheating we have four (4) tube and shell exchangers, first one is against light naphtha from top distillation, the second is against diesel pumparound, the third is against diesel product is also the stripe reboiler, and the fourth and last one is against bottoms column.
        Then we separate between 10% in a Flash Tank (isenthalpic expansion), for this the pressure is set at 72.5 psia (58 psig), below the vapor pressure at preheating temperature, of 93psi at 428°F. The vapor go to the 8 column stage, and the liquid go to the furnace.
        The furnace outlet temperature is 680°F,with 40psi pressure drop.
        Our 12 stages column is operating at 20psig at top, with 4 psi pressure drop.
        Now, I can improve thermal recovery, to get 570°F (it is very important to minimize the use of fuel gas), but the flash pressure decrease significantly, and I can’t get enough pressure to get the 24psig at bottom column. So I’m considering to pump liquids from Flash Tank, and get the column and outlet furnace vaporization between 45-50%wt, with Flash Tank level control.
        I still don’t know how to size line from furnace to column, just with 2phase criteria? And with this obtain the pressure drop in the line.
        The other thing is if I pump the Flash Tank liquid perhaps there is a better control option than level control.
        The last point is that my furnace pressure drop perhaps is to low.
        Perhaps you can help me to figure out this, in a better way, to decreasse my stress for this and perhaps get a cutie with this hahahaha. Thanks!!!

      •   

      Similar Threads

      1. Replies: 3
        Last Post: 08-31-2017, 05:47 PM
      2. Article: Latent heat of vaporization of Crude Oil
        By monugeni in forum Home Articles
        Replies: 0
        Last Post: 07-01-2014, 05:22 PM
      3. Latent heat of vaporization of Crude Oil
        By monugeni in forum Petroleum Refining
        Replies: 0
        Last Post: 06-30-2014, 03:06 PM
      4. Article: eclipse e300 for water vaporization application
        By worawut sitthithanasut in forum Home Articles
        Replies: 0
        Last Post: 12-10-2010, 09:06 PM
      5. eclipse e300 for water vaporization application
        By worawut sitthithanasut in forum Engineering Software Tutorial
        Replies: 0
        Last Post: 12-08-2010, 08:04 AM

      Tags for this Thread

      Bookmarks

      Posting Permissions

      • You may not post new threads
      • You may not post replies
      • You may not post attachments
      • You may not edit your posts
      •