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What are the advantages or disadvantages in having a backpressure control valve for Drum Warm-up? We are thinking of installing a back pressure contol valve in the common vapor line for each Drum pair so that we can restrict the vapor flow during Drum Warm-up and force more vapors through the Drum that is warming up. Our objective is to have a shorter warm-up time so that we can further reduce Drum cycles. Are there any Cokers doing this and if so what are the benefits or results?
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We use a butterfly valve in the common lines of our drum pairs. We’ve had extremely short warm ups, but only choose to do so when we are behind in schedule. We run 14hrs.
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Do you have a vender contact for the type of backpressure butterfly valve that you use? What has your Drum warm-up time changed from and to when you use the butterfly valve? What percentage do you close down on the butterfly?
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We use Fischer Valves. We’ve closed them fully at times, but generally we may close them to 40-50% in order to get adequate preheat within 45-60mins. By adequate I mean 400*F+ skin temps./minimum OVHD temp. drop after switch. If you are to start doing this on a routine basis I would suggest thourough and routine drum seem inspection.
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Closing this valve also will depend on the load to the unit, since, some times closing much the same one, leaves without sufficient load to the tower (Fractionator), We have constructed graphs the load to the unit vs percentage of the valve (opening) and temperature rate in the bottom of the drum, this allowed us to know to a certain load, how many we are going to closed in order to manage (to reach) the temperature in the drum, in the necessary time (all this is approximated)
I´m going to send the spec for our valve, Regards
Im sorry for my english -
Have you also tried using this backpressure valve to help suppress the foam front? I am thinking that this could help not only for drum warm-up but also as means of slowly letting down the drum pressure to prevent the drum from foaming immediately after switching feed from the drum and the introduction of quench steam. Do you have the backpressure valve set up to control from the DCS Control Room?
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No. We’ve never tried it for that application. Dry steam and continued quench oil (5-10mins after) have seemed to be adequate in keeping down foam @ switch.
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AnonymousUp here in the rockies, we use the butterfly valve as a back pressure controller. Like perk, we only do short warm ups when we are behind schedule, we also run 14 hour cycles. we usually backwarm to the blowdown which roughly takes 30 to 40 minutes to achieve 450f degrees then warm up to the frac to roughly 650f degrees. Up here we are referred to as sluicers, but i would be honored to be labelled a RAT. [:)] I’ve been workin on the drums for 15 years and still to this day sluicers aren’t respected[sm=rolleyes.gif] as the other units are. [:@] Rat would be the perfect title for the job.
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AnonymousYou could try partially closing the fractionator return valve off your vapor line to see if this aids your drum warm up before investing in a back pressure regulator with console control scheme.
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AnonymousI have heard of some places using this to help prevent a foam front from advancing after the switch. It helps stablize the pressure drop across the drums.
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- We run 20 sometime 18hrs cycles and have to be very carefull when un-heading beacause we produce 100% shot Coke
- After 14hrs, what type of bottom un-heading system are you running/using?
- What are your heater COT’s.
- What type of Coke are you’ll producing?
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