DECOKING APPARATUS

The specification discloses a decoking apparatus suitable for use with a reaction vessel for the thermal cracking of heavy petroleum oils. The apparatus includes a cylinder assembly mounted on top of the reaction vessel and having a cylinder and a piston slidably and rotatably received in the cylinder, the cylinder and piston defining a scrubbing liquid chamber which is sealed from the outside. scrubbing liquid is fed through the scrubbing liquid chamber to a main injection pipe attached to the piston for movement therewith and projecting into the reaction chamber to inject the liquid through a plurality of jet nozzles in the main injection pipe against the inner wall surfaces of the reaction vessel. In this way, the coke deposit which builds up on the inner surfaces of the reaction vessel can be quickly, safely and efficiently removed without the need for shutting down the operation and waiting for the reaction vessel to cool.