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    4 drums coker
    Participant

    Tower, Fractionation, Product

    1) Goal is to get about 90% C3/C4 recovery or allow only 10% or less C3/C4 to go out with the fuel gas. FW quoted 93% max recovery was a good economic limit.
    2) With the naphtha lean oil increase flow and lower temperature to increase recovery most significant variable to adjust
    3) Stripper reboiler can over strip. Look at the C2 in the debutanizer OVHD there should be a small amount of C2 in the debutanizer OVHD.
    4) Sponge oil (LGO) rate does not have a very significant affect on C3/C4 recovery
    5) Reboilers should be limited to 550 to 600F on the hot side of the exchanger to avoid polymerization of the olefins on the shell side of the reboiler.

    Coke Drums
    1) Drum Cracks

    • Increase cycle times for better warm-up and quench
    • Use strain gauging to determine quench program
    • Scaffold at problem weld seams and do proactive inspection and repair
    • Consider Delta Valve Center Flow Devise
    • Need for a industrial weld repair standard.

    2) Valves

    • MOV Interlocking System with procedures for Interlock failure
    • Consider MOV Ring Valve for back-pressure control (warm-up)
    • Consider SP-4 Blowdown MOV control from Console

    3) Cutting

    • Auto-switch Bit
    • Flowserve Bit Oil contamination issues, continuous self-draining, can be manually switched and has indicator position.
    • Ruhr Pumpen Bit No oil needed, does not self drain with nozzles plugged, can be manually switched but does not have an indicator a tywrap is used to determine position.
    • Delta Valve Bit Cannot be manually switched, no position indicator, longer drill time.

    4) Drill Water Diverter Valve

    • Pacific Valve Actuator problems, Positioner problems, coke fines in orifice plates.
    • BOC Valve No insurance of position but fails in bypass position, maintenance in place (change pilot valve or cartridge in one hour)
    • Elwood Valve Cam shaft ensures correct position.

    Heaters, Tube decoke

    When To Spall?
    Temperature 1200, 1250, 1265 F
    Pressure Drop
    Heater Management System
    How many TIs used to determine when to spall.

    How to spall? Duration of spall?
    Consistent Procedure.
    Steam vs Water
    Multiple injection points, use inlet feed inlet only.
    Single fired and double fired heaters can be spalled.
    12, 18, 20, 24, 32, 48 hours per pass.

    Effects of spalling on tubes.
    Erosion.

    Tube ceramic coatings.
    Platformers, scale paint.

    Pass trips due to low flow.
    Trip delays (5-45 sec.).
    Laydown coke in tubes
    Piping design.
    Type and location of instrument taps.

    Ideal periods between spalls .
    6-8 months common, 1 year ideal.

    Spall each pass or all passes.
    Procedure varies.

    Manipulation of outlet temperatures and flows.
    Extend run time to schedule spalling or pigging.

    Ideal periods between spalls .
    6-8 months common, 1 year ideal.

    Number of TIs on each heater pass.
    4-24, varies by design.

    Heater Monitoring.
    Continuous thermal imaging.

    Cleaning of convection section.
    Polar blast.
    Extra doors cut in. Refractory repairs.

    Tube metallurgy change on last 4-5 tube rows.
    Heat transfer differences.

    Why spall vs pigging.
    Online vs heater shutdown.

    Heater Monitoring.
    Continuous thermal imaging.

    Cleaning of convection section.
    Polar blast.
    Extra doors cut in. Refractory repairs.

    Tube metallurgy change on last 4-5 tube rows.
    Heat transfer differences.

    Why spall vs pigging.
    Online vs heater shutdown.

    Thermal shocks during spall.
    Varies, 100 500 F.

    Burner maintenance.
    PM of burners by operations.

    Merox waste gas consumed in heater.
    Through wall lance.
    Connected to main burners

    Internal ceramic coating of tubes.
    Has been done. Jury still out.

    Thermowell metallurgy/ coatings.
    9cr, 304ss, 347ss.
    Stellite coated.

    Sporadic/ episodal fouling of heater tubes.
    Desalter upsets.
    FCCU catalyst fines
    Crude sludges

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