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Effective Decoking Procedure


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#1 alameehs

alameehs

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Posted 03 January 2017 - 07:07 AM

good day

 

I am plant engineer on ethylene plant and I need your help for decoking procedure.

 

currently we face a difficulty to reduce Venturi critical pressure after complete decoking pressure  CPR. we start decoking activity when cut HC feed and maintained COT at 820 C and dilution steam at 25 t/hr. at this point we introduce the air slowly until COT reached 850c and hold for 1 one hours after that  we increase COT to 870 with almost same air flow and waiting for almost 10 hours. co2 concentration only increase at beginning of introducing air and it reached up to 1.5 %. Until end of the procedure, we never notice any change of CO2 concentration.

 

once complete this procedure, still CPR of several coils on high ration

 

I need you help if there is some mistake or improvement for this procedure  

 

your help is highly appreciated

thanks



#2 pavanayi

pavanayi

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Posted 03 January 2017 - 07:52 AM

It is difficult for anyone to offer any opinion on your question as we have no idea about your plant, licensor, furnace type, coil vendor etc. The decoking procedure to be followed would have been amply explained in your operating manual and/or the documentation from the coil vendors if the coil has been replaced, together with information regarding temperatures, ramp up procedure, holding time, COlevels, lab sample duration, and the criteria to terminate your decoking to re introduce h/c. 

 

Ideally I would expect the CO2 concentration to taper off and when it has dropped below a particular value set by the vendor (confirmed by 3 samples atleast, as I used to do a good few years back), then the furnace can be taken back inline.






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