decoking

Decoking is the process of removing coke, a carbon-rich solid residue formed from hydrocarbon processing, from process equipment to restore heat transfer, flow, and throughput. Coke deposits accumulate in reactors, furnaces, and cokemaking units during high-temperature hydrocarbon conversion. If not removed, coke increases pressure drop, decreases heat transfer efficiency, and can cause overheating or equipment damage.

In coke ovens, decoking specifically refers to removing coke from oven chambers after a coking cycle. The solid coke is expelled from the ovens into a receiving vehicle, typically by a mechanical pusher, and then cooled or quenched before handling. In some plants, hot pushing is used to minimize cycle time, with subsequent quenching to control dust and emissions.

In refinery processing and petrochemical units, decoking usually means removing inorganic coke from equipment or catalyst surfaces. In fluid catalytic cracking, spent catalyst carries coke to the regenerator, where air oxidizes the coke to CO2/CO, burning off carbon and heating the catalyst, which is then recycled to the reactor. In fired heaters, furnaces, and process lines, decoking involves controlled oxidation to burn away surface coke on tubes, coils, or bundles, often with sulfur retention and emission controls.

Safety and environmental considerations include high temperatures, corrosive combustion products, particulate matter, and occupational hazards. Decoking requires permit-to-work systems, gas monitoring, sulfur and hydrocarbon management, and proper quenching and collection of byproducts.