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  1. lgmarti

    Effect of adding external stream to Crd Twr pumparound

    One of our HDS units is planning on routing their stripper overhead liquid to the crude unit top pumparound (@ the suction of the pump). I would have prefered to route the stream to the slop tank. However, the stream would then back out crude from the crude unit. The stream is at 100F and it...
  2. lgmarti

    Self-venting pipe in Crude Tower Draws

    Do the draws from a Crude tower need to be sized for aerated fluid? What is the recommended length of the self-venting pipe. Could the diameter of the pipe be decreased within a couple of feed from the nozzle?
  3. lgmarti

    Location of Thermocouple in Distillation Towers

    Thanks for your reply. I do not know much about controls so please excuse my ignorance. The only thing I know is that the thermocouple is located in tray #2 from the bottoms (TC701); and that TC-701 controls the steam flow controller (FC405). The flow controller flows the setpoint very well...
  4. lgmarti

    Location of Thermocouple in Distillation Towers

    What is the best location for a tray thermocouple? I have a thermocouple located at the outlet of the tray downcommer. The temperature fluctuates by 10-15 degrees and is hard to control. Should the thermocouple be on the vapor or the liquid phase? In the downcommer where I can guarantee...
  5. lgmarti

    Kettle Reboiler Duty Swings

    ...the weir, a 50% level in the tower and a tower top pressure of 150 psig. Using the same formula, Pd = (liquid height @ tower - weir height)*(density/2.31), the liquid height @ the tower is only 4'11". The problem is that the tower T-T line is 7'4" from the ground. Does this mean that I...
  6. lgmarti

    Kettle Reboiler Duty Swings

    The operators have been fantasazing about the depentanizer bottoms pump for at least 10 years. So the problem is not new. They were really excited about putting the pump. I may say, I am not a very popular person now since I stopped the pump idea. I did a survey on the depentanizer bottoms...
  7. lgmarti

    Kettle Reboiler Duty Swings

    Thank you so much for all your responses. Yes, the deethanizer is a lean oil absorber and a stripper in one. We control the lean oil temperature and the lean oil rate very well and there is no overhead accumulator. The gas goes straight to the FG system. The tower pressure is constant at 150...
  8. lgmarti

    Kettle Reboiler Duty Swings

    I checked the condensate header pressure to the steam trap and it is steady at 50 psig. Should this be an indication that the trap is working properly? It is maintaining a steady pressure in the steam.
  9. lgmarti

    Kettle Reboiler Duty Swings

    The kettle reboiler in our Deethanizer tower has a pretty consistent swing that has been a mystery for the past 20 years. The steam to the reboiler is controlled by Tray 2 of the tower. Every ten minutes this temperature cycles up and down. This wave is strong enough to increase the overhead...
  10. lgmarti

    Pressure control with flooded condensers

    Our depropanizer has flooded condensers. Over the years we have tried to improve the pressure conrol in this tower without success. The last proposed control scheme will control the accumulator pressure with the level in the drum. That is, when the pressure increases, the overhead release...
  11. lgmarti

    Weird Vacuum Tower dP problem

    Again thank you for your input. I guess that I was going to address the problem backwards. I started looking for sources of amine in the slop/drips. As the matter of fact, we found them at ppm levels. Next I was going to do an "amine" balance in the desalters" to see if they go...
  12. lgmarti

    Weird Vacuum Tower dP problem

    We collected more "coke-looking balls" from the LVGO section yesterday. The lab crushed the particles, mixed it with deionized water and place it on a hot plate. After heating, the water turned black (to my annoyance). The slurry was then tested in a ion chromatograph and showed a...
  13. lgmarti

    Weird Vacuum Tower dP problem

    25362, no I did not know about FeCl3. Our lab equipment can test for chlorides only. I collected some coke-looking materials out of some strainers and they ended up being 82% chlorides! They were also not soluble in water...at least not tap water. We have been relying on our vendors to test...
  14. lgmarti

    Performance of exchangers in Preheat train

    25632, Thank you for you input. Becuase of the outcome, it is obvious that I have done several things wrong. I am trying to learn as I go. We run a cocktail of crudes. Sometimes we blend up to 5 different crudes. The mixture API varies between 17-30 (the average is 21). I have noticed that...
  15. lgmarti

    Performance of exchangers in Preheat train

    I was given the task of identifying which exchangers in the crude unit preheat train where fouling. I was lucky becuase I have plenty of thermocouples and flowmeters to calculate the U coefficient of each bank of exchangers. There were 3 banks of exchangers where the U coefficient had...
  16. lgmarti

    Coker Naphtha Diolefin Reactor

    The 1st Reactor does not trap silica or filter out solids. We have analyzed the Rx1 catalyst on several occassions for silica. There is none. The dP is only 4 psi, so it does not filter anything (actually we have full flow filters before the unit). All catalyst vendors agree that this reactor...
  17. lgmarti

    Weird Vacuum Tower dP problem

    Has anyone out there experienced salt built up in the Vacuum tower? During "normal" operations our LVGO section pressure drop is ~ 8mmHg. Over time, however, the dP increases! When it reaches 14mmHg, the unit goes thru a salt sublimation process. The temperature in the LVGO section...
  18. lgmarti

    HVGO Cutpoint/Yield improvement

    The maximum heater outlet temperature is 775F. Yesterday, we were step-testing the heater and we increased its duty 14% to a 775F heater outlet. The HVGO yield did not improved and we lost 3-4 mmHg of vacuum (we started at 14.5mmHG and ended up at 18.3mmHg). However, one of my operators...
  19. lgmarti

    HVGO Cutpoint/Yield improvement

    I was wondering what other refineries do to optimize their HVGO cutpoint/yield. In my refinery the strategy is to always maximize the heater outlet temperature. I have noticed, however, that the actual yield does not necesarily increase with the higher duty/temp and that sometimes maximizing...
  20. lgmarti

    Coker Naphtha Diolefin Reactor

    We have and HDS unit that processes 100% coker naphtha (I don't recommend this operation to ANYONE). It has 3 reactors. The 1st Reactor was ment to be for diolefin saturation and it is placed before the furnace. Sometime ago, it was decided to convert this unit to heavy coker naphtha and a...

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