Effect of Increasing throughput on Coke Yield

[Anonymous]

I have been working for Reliance Jamnagar Refinery since last 3 years after my graduation and currently involved in Revamp study of Delayed Coker Unit. The original design capacity of DCU is 160 KBPSD and the revamped capacity is expected to be ~184 KBPSD.  As a part of Reactor Simulation Group, I have estimated Coke drum yields for the revamped case using KBC DC-SIM. What I found that my Coke yield (wt%) has increased on increasing throughput while maintaining same COT , Thruput Ratio and Drum Pressure as original design. The reason I could think of possibly is that at constant CFR, increasing thruput means increase in recycle rate (tph) and I found a literature where it states that it’s actually recycle rate and not recycle ratio which increases coke yield. Kindly throw some light on the subject as most of the literature reflects affect of Temperature, Pressure and CFR on Coke Yield.

[Sim Romero]

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)

[Anonymous]

Plz check the coke quality.I hope coke should show some more VCM and ash. Probably this is becz of the improper flashing of the increased material in the coke drum.
Consider coke drum as a flashing vessel which should have some design parameter.
Increased in feed rate to that of same vessle will generate less flash (With maintening same delta pressure i.e.feed coke drum inlet to that of the coke drum).
I hope this is the reason why your coke % has been increased.

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