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 oxygen are blown from an upstream lance 4 configured by a double tube, and LNG is blown from a downstream lance 6 on the downstream side in a hot air blast direction, so that oxygen to be used for combustion of the LNG is supplied from the upstream lance 4, and the pulverized coal whose temperature has been increased by the combustion of the LNG is combusted along with the supplied oxygen or oxygen in an air blast. 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 LNG from the downstream lance 6 with respect to the blast direction ranges from 30 to +45, and a blowing position of the LNG from the downstream lance 6 with reference to a position at which the upstream lance 4 is inserted into a blast pipe 2 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 oxygen are blown from an upstream lance 4 configured by a double tube, and LNG is blown from a downstream lance 6 on the downstream side in a hot air blast direction, so that oxygen to be used for combustion of the LNG is supplied from the upstream lance 4, and the pulverized coal whose temperature has been increased by the combustion of the LNG is combusted along with the supplied oxygen or oxygen in an air blast. 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 LNG from the downstream lance 6 with respect to the blast direction ranges from 30 to +45, and a blowing position of the LNG from the downstream lance 6 with reference to a position at which the upstream lance 4 is inserted into a blast pipe 2 ranges from 160 to 200 in terms of a blast pipe circumferential direction angle.

A method of operating a blast furnace by blowing a pulverized coal at an amount of not less than 150 kg/tp from tuyeres through a lance into a blast furnace, wherein when the operation is performed under a condition that lump coke charged from a furnace top has a strength defined in JIS K2151 (DI.sup.150.sub.15) of not more than 87%, the pulverized coal blown through the tuyere contains not more than 60 mass % as a weight ratio of coal having a particle size of not more than 74 m and has an average volatile matter of not more than 25 mass %, and a blast temperature blown through the tuyere is not higher than 1100 C., oxygen is simultaneously blown into the furnace with the blowing of the pulverized coals through the lance and a gas having an oxygen concentration of 60 vol %-97 vol % is used as a carrier gas for the blowing of the pulverized coal.

An injection regulation and control device includes blast furnace tuyeres for introducing rich oxygen or pure oxygen to form tuyere raceways. Temperature-adjusting injection openings are evenly formed in the circumferential direction of a blast furnace and inject a hydrocarbon component-containing injection object to the blast furnace. The temperature-adjusting injection openings are located, in an axial direction, within a height range where a soft melting dripping zone is located and are not lower than the positions of the blast furnace tuyeres. The hydrocarbon component-containing injection objects are enabled to undergo a thermal cracking reaction by utilizing the temperature in the vicinity of the tuyere raceways to form a hydrocarbon thermal cracking heat absorption area. Gas products generated by the thermal cracking reaction of the hydrocarbon component-containing injection objects increase the blast furnace gas volume. Redundant heat in a lower high-temperature area is carried to the upper part of the blast furnace.

A method of decarburizing a molten alloy may generally comprise injecting a first gas comprising at least one of argon, carbon dioxide, and oxygen through a first fluid-conducting portion of a tuyere into the molten alloy below the surface of the molten alloy, and injecting a second gas comprising at least one of argon and carbon dioxide through a second fluid-conducting portion of the tuyere into the molten alloy below the surface of the molten alloy. The tuyere may comprise an inner portion concentrically aligned within an outer portion to define an annulus therebetween. The first gas may be injected through the inner portion, and the second gas may be injected through the annulus.

A method of decarburizing a molten alloy may generally comprise injecting a first gas comprising at least one of argon, carbon dioxide, and oxygen through a first fluid-conducting portion of a tuyere into the molten alloy below the surface of the molten alloy, and injecting a second gas comprising at least one of argon and carbon dioxide through a second fluid-conducting portion of the tuyere into the molten alloy below the surface of the molten alloy. The tuyere may comprise an inner portion concentrically aligned within an outer portion to define an annulus therebetween. The first gas may be injected through the inner portion, and the second gas may be injected through the annulus.

A method of operating a blast furnace includes two or more lances that inject reducing agents from a tuyere; injecting a solid reducing agent and a flammable reducing agent from different lances; and disposing the lances so that an axial line that extends from an end of the lance that injects the solid reducing agent and is the axial line of the lance that injects the solid reducing agent and an axial line that extends from an end of the lance that injects the flammable reducing agent and is the axial line of the lance that injects the flammable reducing agent cross each other, and so that a main flow of the solid reducing agent injected and a main flow of the flammable reducing agent injected overlap.

A method of operating a blast furnace includes two or more lances that inject reducing agents from a tuyere; injecting a solid reducing agent and a flammable reducing agent from different lances; and disposing the lances so that an axial line that extends from an end of the lance that injects the solid reducing agent and is the axial line of the lance that injects the solid reducing agent and an axial line that extends from an end of the lance that injects the flammable reducing agent and is the axial line of the lance that injects the flammable reducing agent cross each other, and so that a main flow of the solid reducing agent injected and a main flow of the flammable reducing agent injected overlap.

On the basis of data obtained by means of analyzing coal, a first and second coal type satisfying conditions are selected, the ash melting point of the mixed coal resulting from mixing the first and second coal types is derived on the basis of a four-dimensional state diagram for SiO.sub.2CaOMgO-20% Al.sub.2O.sub.3, on the basis of the ash melting point of the mixed coal and the four-dimensional state diagram, an additive causing the ash melting point of the mixed coal to be at least 1400 C. at the lowest quantity when added to the mixed coal is selected from SiO.sub.2, MgO, and CaO, the addition quantity of the additive is derived, the first coal type and second coal type are mixed to result in the mixed coal, and the addition quantity of the additive is added to the mixed coal.

On the basis of data obtained by means of analyzing coal, a first and second coal type satisfying conditions are selected, the ash melting point of the mixed coal resulting from mixing the first and second coal types is derived on the basis of a four-dimensional state diagram for SiO.sub.2CaOMgO-20% Al.sub.2O.sub.3, on the basis of the ash melting point of the mixed coal and the four-dimensional state diagram, an additive causing the ash melting point of the mixed coal to be at least 1400 C. at the lowest quantity when added to the mixed coal is selected from SiO.sub.2, MgO, and CaO, the addition quantity of the additive is derived, the first coal type and second coal type are mixed to result in the mixed coal, and the addition quantity of the additive is added to the mixed coal.