(55b) Ethylene Cracking Heater Decoking Tutorial

Coke is deposited in the radiant coils and in the transfer line exchangers (TLEs) as a consequence of the cracking reactions that occur in ethylene furnaces.  The coke must be removed on a periodic basis to maintain acceptable heat transfer and pressure drop in the system (to maximize yield and prevent unplanned shutdown of the equipment).  The process of gasifying the coke with steam and/or air to remove it from the radiant coils and TLEs is called "decoking."  

The decoking procedure affects the performance of the furnace and the life of the radiant coil. Moreover, improper decoking can shorten the furnace run-length. This tutorial will introduce decoking concepts and examine important factors that contribute to the safe and successful execution of a decoke with a short duration.  The following objectives will be addressed in the tutorial: 

• Define the basic principles of decoking
• Introduce decoking flow schemes and philosophies
• Describe decoking objectives
• Examine the general steps in the radiant coil and TLE decoking sequences 
• Review key variables that should be closely monitored to ensure a safe and successful decoking
• Highlight tips for maximizing coke burn and safety, while minimizing time and damage to equipment
• Mention instrument considerations
• Benchmark key decoking performance parameters