To provide a method for operating a blast furnace with which the combustion efficiency of a solid fuel, such as pulverized coal, is improved, thereby making it possible to improve productivity and reduce CO.sub.2 emissions. Pulverized coal and LNG are blown from an upstream lance configured by a double tube, and oxygen is blown from a downstream lance on the downstream side in a hot air blast direction, so that oxygen used for preceding combustion of the LNG is supplied from the downstream lance, and the pulverized coal whose temperature has been increased by the combustion of the LNG is combusted along with the supplied oxygen. When a direction perpendicular to the hot air blast direction is designated as 0 , and a downstream direction and an upstream direction therefrom in the hot air blast direction are designated as positive and negative, respectively, a blowing direction of the oxygen from the downstream lance with respect to the blast direction ranges from 30 to +45 , and a blowing position of the oxygen from the downstream lance with reference to a position at which the upstream lance is inserted into a blast pipe ranges from 160 to 200 in terms of a blast pipe circumferential direction angle.

To provide a method for operating a blast furnace with which the combustion efficiency of a solid fuel, such as pulverized coal, is improved, thereby making it possible to improve productivity and reduce CO.sub.2 emissions. Pulverized coal and LNG are blown from an upstream lance configured by a double tube, and oxygen is blown from a downstream lance on the downstream side in a hot air blast direction, so that oxygen used for preceding combustion of the LNG is supplied from the downstream lance, and the pulverized coal whose temperature has been increased by the combustion of the LNG is combusted along with the supplied oxygen. When a direction perpendicular to the hot air blast direction is designated as 0 , and a downstream direction and an upstream direction therefrom in the hot air blast direction are designated as positive and negative, respectively, a blowing direction of the oxygen from the downstream lance with respect to the blast direction ranges from 30 to +45 , and a blowing position of the oxygen from the downstream lance with reference to a position at which the upstream lance is inserted into a blast pipe ranges from 160 to 200 in terms of a blast pipe circumferential direction angle.

Apparatus for supplying blast to a blast furnace (1) having a plurality of hot blast stoves (4, 5, 6), each stove including a cold blast inlet, a fuel inlet, an air supply inlet, a hot blast outlet, and a waste gas outlet; a waste heat recovery unit (30) connected to a fuel supply, the stove fuel inlet and the cold blast inlet. The stove waste gas outlets are connected to the cold blast inlets, whereby stove waste gas from one stove (5) is supplied, via the waste heat recovery unit, as cold blast to another stove (4).

Apparatus for supplying blast to a blast furnace (1) having a plurality of hot blast stoves (4, 5, 6), each stove including a cold blast inlet, a fuel inlet, an air supply inlet, a hot blast outlet, and a waste gas outlet; a waste heat recovery unit (30) connected to a fuel supply, the stove fuel inlet and the cold blast inlet. The stove waste gas outlets are connected to the cold blast inlets, whereby stove waste gas from one stove (5) is supplied, via the waste heat recovery unit, as cold blast to another stove (4).

A method for heating a blast furnace stove includes combusting fuel in a combustion chamber in the stove, providing combustion gases from the combustion chamber to heat refractory material in the stove, recirculating exhausted combustion gases into the combustion chamber, enriching the combustion chamber with oxygen sufficient for maintaining combustion in the combustion chamber without damaging the refractory material in the stove.

A method for heating a blast furnace stove includes combusting fuel in a combustion chamber in the stove, providing combustion gases from the combustion chamber to heat refractory material in the stove, recirculating exhausted combustion gases into the combustion chamber, enriching the combustion chamber with oxygen sufficient for maintaining combustion in the combustion chamber without damaging the refractory material in the stove.

Electric stove for heating a reducing gas, the electric stove including: a hollow metal shell body extending along a longitudinal direction; a refractory lining arranged on an inner surface portion of the shell body; a plurality of bricks arranged in adjacent layers extending along the longitudinal direction, where each brick includes a plurality of cavities extending straight along the longitudinal direction through the respective layer, where the cavities of adjacent layers are aligned to one another, whereby a plurality of channels for conducting the reducing gas is formed; and a plurality of heating wires for heating the reducing gas, wherein each heating wire has a diameter smaller than a diameter of a channel, and where each heating wire extends at least partially through at least one corresponding channel of the plurality of channels, such that when the electric stove is operated, a predefined heat amount is dissipated by each heating wire to a reducing gas flowing around the heating wire.

A slag discharge door device for an electric furnace is provided. The device prevents slag from flowing out via a slag discharge port by making a discharge control door body move up and down to and from the upper surface of a supporting body where slag is discharged by flowing to the upper surface, and the discharge of slag is controlled, such that during steel-making work in the electric furnace, the outflow of slag is prevented and heat losses are reduced, the efficiency of arc heat due to the formation of foamed slag is increased, and valuable metals are recovered from the molten slag thereby increasing the percentage of molten steel recovered.