PURPOSE: To recover waste gases with high efficiency by constituting a controller for the pressure of waste gases in a furnace port part in recoverying of waste gases of a converter of the combination of a pressure controller for furnace port and devices for compensating the volume and pressure of the waste gases in the stage of changing the rate of oxygen blow and by charging of raw materials.

CONSTITUTION: The CO-contg. combustible waste GASES from a converter are recovered with high recovery efficiency without releasing the same partly in air at the furnace port of the converter and without burning CO wastefully by sucking air. The pressure of the waste gases in the furnace port is regulated positive slightly from the atmospheric air. The difference in the gaseous pressure 7 set in a furnace port pressure setter 1 and the measured values 8 of the pressure of the waste gases in the furnace port is arithmetically processed with a pressure controller 2, and the difference thereof is operated with an operator 35 so tht it is made virtually zero. In accordance with this value, the opening of a damper 4 is optimized by operating a damper operator 3. In this case, the change in the rate of blowing oxygen and the change in the pressure of the waste gases owing to the charging of raw materials is compensated with a deliding device 34, and is inputted as the compensation value to an operator 35, by which the operator 3 is operated correctly.