Pyrolysis or steam cracking is the primary process utilized to manufacture olefins from large hydrocarbon molecules. This gas-phase reaction takes place in metal alloy tubes within a fired furnace. Pyrolysis proceeds as a series of free radical reactions and the complexity of the mechanisms increases with the nature of the feedstock. Both rigorous and empirical solution techniques are available. A mathematical model for design of pyrolysis coil is presented. The effect of residence time, temperature, pressure and inert on ethylene yield will be discussed briefly.

Coke formation onto the tubular coils continues to be a challenge faced by engineers. Coke deposition increases fuel consumption, reduces the furnace throughput and causes non-productive outages for decoking activities. Various coke formation mechanisms will be discussed and a review of recent developments to mitigate this phenomenon will be presented.