Abstract: In an apparatus for punching the tuyeres of a converter for smelting of copper or nickel, the apparatus including a carrier frame supported by wheels and which is capable of moving on the working platform located adjacent to the converter, the carrier frame mounting a plurality of punch rods which can reciprocatingly extend into respective tuyeres to remove deposits therein. An electric motor is employed to drive the carrier frame and an electrical control system controls the operation of the electric motor and thus the movement of the carrier frame so that the correct positioning of the punch rods with respect to the tuyeres on a converter can be automatically achieved.

Abstract: In a system wherein exhaust gases containing SO.sub.2 are fed to a sulfuric acid plant from multiple furnaces, including an intermittently operated furnace (such as a copper or nickel converter furnace), a method of automatically controlling the gas pressure to within a predetermined range at a point just upstream of the exhaust gas pretreating equipment at the inlet of the sulfuric acid plant so as to compensate for the fluctuation in the exhaust gas pressure resulting from start up and stopping of the operation of the intermittently-operated furnace. By this method, the disadvantages caused by large gas fluctuations, i.e., the leakage of SO.sub.2 -containing gas and the suction of excess free air can be prevented.