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RE: About Cycle Period


Charles Randall

You have lot good response on cycle time ranges here – 13-36 hours. I assume the 36 hours is either a needle coker with lot soak time (and probably 3 drum operation) or its counting the full cycle on both drums instead of per drum (ie 18 hrs).
Cycle time only works if when you decrease the time you still end up with full drum petcoke – otherwise you are wasting time & money. Additionally lot design & monitoring folks say drum only has about 5-7,000 cycles before you have to replace it and its 15-20 year design life is based on an 18-24 hour cycle. The lower the cycle time the more cycles you chew up per year and the more stress you put on drum (greatly increased because most time has come out of either warm-up or cool-down stages ramping the temp deltas and stress).
The lowest cycle time I know of is 9-10 hours and its for coker on very heavy crude slate. Generally most of fuel cokers on heavy sour crude are at cycles of 12-15 hours. Most of the Anode type cokers run at 14-24 hour cycles because the coke yield is much lower from the sweeter / lighter crudes. Needle cokers run at much higher pressure and temp and often go thru a soaking stage often half to equal a the cycle time …. probably little interest to you.
Besides the heavy crudes having higher coke yield they are also driven more to shot coke instead of sponge as you push the cycle time and try decrease the VM (~as increasing liquid yield) – this often helps the cycle time by allowing quicker decoking stage from the auto-unheading and quicker drill times. But always remember if you dont get full drum dont go there you are just throwing away your drum life.

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