To effectively prevent the adhesion and deposition of carbon on the bend of the riser of a coke oven by simultaneously supplying a pressurized liquid into the respective jet nozzles fitted upstream and downstream of the bend.

A jet nozzle 3 is fitted upstream of the bend 2 of the riser of a coke oven, and a jet nozzle 4 is fitted downstream of the bend 2. A pressurized liquid (e.g. pressurized ammonia water) is simultaneously supplied into the nozzles 3 and 4 during, desirably, coal feed into a carbonization chamber 7. As a result, the ejector effect brought about by the jet being the pressurized liquid jetted from the nozzle 4 realizes both the suction of the gas from the carbonization chamber and the reduction of the pressure in it to a negative one sufficient for the prevention of gas leak from the door of the chamber 7 during coal feeding, while the gas is cooled and scrubbed. By simultaneously jetting the pressurized liquid both from the nozzle 3 and from the nozzle 4, the carbon deposition on the bend can be effectively removed, and the carbon deposition on the bottom of the bend can also be prevented.