A reducing gas injection system for a blast furnace having a blast furnace wall, the system including a reducing gas distribution pipe, one or more injectors mounted to the blast furnace wall at a shaft level, where the reducing gas distribution pipe is attached to the blast furnace wall or its supporting structure, where the injector(s) have a nozzle body with a peripheral wall extending along a longitudinal axis from a front portion, with at least one injection hole, to an opposite rear portion with an inlet port, where the nozzle body includes an inner gas channel for guiding reducing gas from the inlet port to the injection holes(s); where the nozzle body is mounted trough an aperture in the blast furnace wall in such a way that the front portion with the injection hole(s) is located on an inner side of the blast furnace, whereas the rear portion with the inlet port is outside of the blast furnace wall, where the nozzle body includes a peripheral mounting portion configured for connecting the injector in a gas tight manner to the aperture in the blast furnace wall, where the inlet port is in fluidic connection with the reducing gas distribution pipe by means of an injector stock, the injector stock including a feeding pipe connected to the reducing gas distribution pipe, an elbow connected to the feeding pipe and an injector pipe connected to the elbow, the injector pipe being flange mounted in a gas tight manner to the inlet port of the injector and the injector pipe and/or an outlet of the elbow having at least one cardan compensation joint.

A device to inject a reducing gas into a shaft furnace including an external casing whose front face is provided with an outlet for gas injection into the shaft furnace, an internal casing located inside the external casing and made of a steel able to resist to a temperature up to 1200° C., this internal casing having an opening matching the gas injection outlet of the front face of the external casing and a refractory layer located between the external casing and the internal casing.

A device to inject a reducing gas into a shaft furnace includes an external casing whose front face is provided with an outlet for gas injection into the shaft furnace, an internal casing located inside the external casing wherein reducing gas is circulating. The internal casing has an opening matching the gas injection outlet of the front face of the external casing. The front face of the external casing includes an upper and a lower part and the gas injection outlet is in the lower part and inwards from the upper part.

A device to inject a reducing gas into a shaft furnace includes an external casing whose front face is provided with an outlet for gas injection into the shaft furnace, an internal casing located inside the external casing wherein reducing gas is circulating. The internal casing has an opening matching the gas injection outlet of the front face of the external casing. The front face of the external casing includes an upper and a lower part and the gas injection outlet is in the lower part and inwards from the upper part.

A blast furnace for ironmaking production wherein iron ore is at least partly reduced by a reducing gas which is injected in the stack of the blast furnace. The blast furnace includes an external and an internal wall, having a thickness T.sub.int, in contact with matters charged into the blast furnace. The thickness T.sub.int of the internal wall is substantially constant above and below the injection area of a reducing gas.

A shaft furnace, in particular a blast furnace, comprises includes an outer metal shell; a plurality of tuyeres arranged to inject hot blast into the shaft furnace; and means for injecting process gas in the shaft stack area, where the injector has a nozzle body with a peripheral wall extending along a longitudinal axis from a front portion, with at least one injection hole, to an opposite rear portion connected to a base member, where the nozzle body includes an inner gas channel for guiding process gas from an inlet port in the base member to the injection holes(s), nozzle body being mounted through an aperture in the metal shell in such a way that the front region with injection hole(s) is located on the inner side of the metal shell, whereas the rear portion is outside of the metal shell, and the base member includes a peripheral mounting portion configured for connecting the injector in a gas tight manner to a mounting unit surrounding the aperture in the metal shell.

A shaft furnace, in particular a blast furnace, comprises includes an outer metal shell; a plurality of tuyeres arranged to inject hot blast into the shaft furnace; and means for injecting process gas in the shaft stack area, where the injector has a nozzle body with a peripheral wall extending along a longitudinal axis from a front portion, with at least one injection hole, to an opposite rear portion connected to a base member, where the nozzle body includes an inner gas channel for guiding process gas from an inlet port in the base member to the injection holes(s), nozzle body being mounted through an aperture in the metal shell in such a way that the front region with injection hole(s) is located on the inner side of the metal shell, whereas the rear portion is outside of the metal shell, and the base member includes a peripheral mounting portion configured for connecting the injector in a gas tight manner to a mounting unit surrounding the aperture in the metal shell.

A method of operating an ironmaking or steelmaking plant with low CO.sub.2-emissions is provided. Hydrogen and oxygen are generated by water decomposition and at least part of the generated hydrogen is injected as a reducing gas into one or more ironmaking furnaces with off-gas decarbonation and reinjection into the furnaces of at least a significant part of the decarbonated off-gas and at least part of the generated oxygen is injected as an oxidizing gas in the one or more ironmaking.

A method of operating an ironmaking or steelmaking plant with low CO.sub.2-emissions is provided. Hydrogen and oxygen are generated by water decomposition and at least part of the generated hydrogen is injected as a reducing gas into one or more ironmaking furnaces with off-gas decarbonation and reinjection into the furnaces of at least a significant part of the decarbonated off-gas and at least part of the generated oxygen is injected as an oxidizing gas in the one or more ironmaking.

An air blast system for melting furnaces includes: a supply unit supplying hot air into a melting furnace; a bustle pipe connected to the supply unit; a tuyere stock connecting the bustle pipe to the melting furnace to supply hot air from the bustle pipe to the melting furnace in a distributed manner; and a temperature management module determining whether the tuyere stock is damaged by comparing a temperature of the tuyere stock with a preset reference temperature.