---
title: "Coking"
description: "Coking in refining and petrochemicals is the formation of hard carbonaceous deposits on hot process surfaces — typically inside ethylene-cracker furnace tubes, delayed-coker drums, and the radiant tubes of fired heaters. Coke forms by thermal cracking of hydrocarbons in stagnant or low-velocity zones, accumulating until a planned decoking outage removes it."
canonical_url: "https://sylio.co/glossary/coking"
last_updated: "2026-06-28T02:29:31.822Z"
---

**Coking** in refining and petrochemicals is the formation of hard carbonaceous deposits on hot process surfaces — typically inside ethylene-cracker furnace tubes, delayed-coker drums, and the radiant tubes of fired heaters. Coke forms by thermal cracking of hydrocarbons in stagnant or low-velocity zones, accumulating until a planned decoking outage removes it.

## Where it dominates

- Ethylene-cracker furnace radiant tubes
- Visbreaker furnaces
- Delayed-coker process drums
- Some refinery heater tubes
- [FCC](/glossary/fluid-catalytic-cracking) catalyst (different mechanism — burned off in the regenerator)

## Cleaning

Coke is hard, bonded, and refractory — far beyond what [sonic horns](/glossary/sonic-horn) can address. Standard cleaning is by *decoking*: a campaign in which the heater is run with a steam-air mixture at elevated temperature, oxidising the deposit out of the tubes. Manual mechanical pigging is sometimes used on selected sections.

Acoustic cleaning is not a primary tool against coking, but downstream particulate-handling equipment (decoking-effluent dust collection, [SRU](/glossary/claus-unit-sulphur-recovery-unit) adjacency) can benefit from sonic-horn coverage.

## Related terms

- [Fluid catalytic cracking (FCC)](/glossary/fluid-catalytic-cracking)
- [Reformer furnace](/glossary/reformer-furnace)
- [Fouling](/glossary/fouling)