The oil-free solvent-free catalyst is subsequently decoked through a controlled oxidation process by a decoker (50).

(19) The BAT-AELs do not apply during decoking operations.

(19) The BAT-AELs do not apply during decoking operations.

When a Pt/α-Al¿2?O3 catalyst is employed, decoking could be performed without catalyst degradation.

Methods are provided for decoking the radiant coils in an ethylene cracking plant.

At regular intervals, a decoking of the pyrolysis tubes and the primary quenching exchangers is effected in the presence of air.

The assembly includes a housing to hold one or more nozzles that are used to spray or otherwise distribute decoking fluid.

A similar technique is conducted during decoking to remove asphaltene coke starting from the lower convection section upward.

In another form, the apparatus includes a gas spring to counteract the forces imposed by the pressurized decoking fluid.

Once every year or once during decoking, if decoking is less frequent

Hot, decoked material is withdrawn from the base of the secondary regenerator (B) for use in the catalytic cracking reaction.

After decoking, a suppression additive also comprising group IA and IIA metals is added to the steam and hydrocarbon feed.

In the inventive system, the decoking cycle preferably comprises simply a steamout stage and a coke product draining procedure.

Meanwhile, a decoking mechanism is provided for removing the coke on the surface of the inner wall of the cracker during the cracking process.

The decoking process is controlled by monitoring the coil outlet temperature to control the rate of burning of coke in the radiant coils.