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Sim Romero

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  • in reply to: Drum obstrution #5201

    Sim Romero
    Participant

    I am glad the worked out for you.  Keep in mind the outside drum wall temperatures are a poor indicator of the temperature in the drum especially in a plugged hot drum.  Coke and/or pitch is an excelent insulator so a few feet of coke or pitch on the wall can give you a false sence of security.

  • in reply to: Maximum Amount of FCC slurry oil as Coker Feed #5202

    Sim Romero
    Participant

    Most refiners dispose of slurry oil in the coker because there is nowhere else to go with it.  Some use slurry oil to control or avoid shot coke – especally in the cone section of the drum. Finally, a few use slurry oil to control the metals and sulfur in anode grade coke.
     
    FCC slurry oil boils in the same range as heavy coker gas oil – approximately. So when the slurry oil is fed to the coker most of the slurry oil vaporizes out of the coke drum and reports to the gas oil product.  This is highly dependent on the pressure/temperature of the coke drums.
     
    KBC, the company I work for, has done this type of analysis many times.  The economics of sending FCC slurry oil to the coker gets complicated with the gas oil yields in the Hydrotreater(HT) and then the FCC.  A low pressure HT will send aromatic (due to the slurry oil) coker heavy gas oil to the FCC which then will yield higher amounts of slurry oil.  The net results is an increase in slurry oil, poor utilization of the coker, the hydrotreater and the FCC.  However if the HT operates at sufficient pressures to breakup the polynuclear aromatics in the coker gas oil then this might work well.  Bottom line is this is not a simple issue.
     

  • in reply to: Cracks in Heater outlet elbow #5203

    Sim Romero
    Participant

    Good idea.  A tee is frequently used in a fluid coker to avoid erosion, which is common in delayed coker spalling.

  • in reply to: coil inlet temperature #5204

    Sim Romero
    Participant

    The rule of thumb is 1 to 2 wt% velocity steam but more is better.  The problem with more is better is the high velocities produced in the coke drum and fractionator plus the sour water produced. 
     
    Crossover temperatures are typically between 365C to 377C.  At these low temperatures there is no significant thermal cracking/polymerization so the velocities are not critical in the convection section but adding the steam to the crossover does not buy you much in pressure drop – usually.
     
    If the feed has high inorganic solids (greater than .2wt%) there can be significant fouling in the convection section and upper radiant section. With solids more steam in the convection section might not be better.

  • in reply to: Vertical tubes in Coker Heater #5205

    Sim Romero
    Participant

    A refinery near New Orleans has a coker with vertical tubes (converted visbreaker heater) and it worked well.  When I was there we modified the burners to even out the heat flux.  The heater was arranged with a mixture of single fired and dounle fired tube.  The heater worked well because of the low total heat flux and the wide spacing between the burners and the tubes. There were some issues with the return bends but that is somewhat common with a vertical tube heater – at least I seen this problem before.

  • in reply to: Material of coke drums #5217

    Sim Romero
    Participant

    Contact Stress Engineering Services  – SES in Houston

  • in reply to: Effect of Increasing throughput on Coke Yield #5218

    Sim Romero
    Participant

    I had our (KBC’s) delayed coking modeling expert take a quick look at this.  Here are his thoughts;
     
    In DC-SIM is that at higher Feed rates, even with constant COT, CFR and pressure, the reaction temperature in the Drum liquid holdup decreases. Due to more cracking moles at higher feed rates? The lower reaction temperature then results in higher coke yields.
    If you send the file to us we can review the results and see if they are reasonable.
    Thanks,
    Sim Romero (sromero@kbcat.com)

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