Specialized metallurgical processes – compositions for use therei – Processes – Process control responsive to sensed condition
Patent
1996-07-09
2000-07-18
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Process control responsive to sensed condition
75471, C21B 500
Patent
active
060901810
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of operating a blast furnace for producing pig iron, and more particularly to a technology for enabling use of low grade solid reducing agents such as charcoal as well as injection of a large quantity of pulverized coal in a blast furnace by forming a packed bed comprising high strength blocks in the central core of the blast furnace.
BACKGROUND ART
Generally, it is very important to insure gas permeability and liquid permeability in a blast furnace for producing pig iron during its operation into which coke (generic name for iron ore, sintered ore, lime stone, and the like) are loaded therein. When gas permeability in a blast furnace becomes lower, increase of pressure loss or non-uniformed gas flow may occur with defective descent of the burden (frequent occurrence of hanging and slip). which in turn not only makes the operation unstable but also lowers a reaction efficiency in the entire furnace as well as productivity of the blast furnace. Furthermore, when the liquid permeability becomes lower, slag overburden is generated at the tuyere level, which causes not only non-uniformity in gas distribution in the furnace, but also tap hole deviation and a rise in the pressure of in the furnace, thereby causing a non-uniform tap output rate from each tap hole. This phenomenon also causes defective decent of the burden and damages the operational stability of the furnace. In relation to the gas permeability and liquid permeability in a blast furnace, it has been recognized that the operational factors, such as gas permeability and liquid permeability are especially important in the core section. The core section comprises a lower section of the tuyere level and a core coke layer existing under a zone where the ores are softened and melted (Refer to FIG. 1). The function of the core section 7 is to control gas flow distribution in a furnace, and as a result, its construction effects the stability and descent of the burden. When the furnace utilizes pulverized coal injection, the core section 7 serves as a path for unburned materials to pass from the tuyere, up to the softening and melting zone.
In order to provide the proper heat source, reducing capacity, gas distribution (gas permeability), liquid permeability and the dropping of molten metal and slag, a relatively high quality coke for the blast furnace has been used. Apart from the possible problem of future exhaustion of feed stock coal used for producing such high quality blast furnace coke, there is the problem that blast furnace coke typically has a high porosity, or a low compression strength or a low strength after reaction (CSR) nature. Even in a case where the coke for a blast furnace has a relatively higher quality than that of commercial coke, the coke can become powdered due to various types of physical or chemical phenomena generated in the furnace. For this reason, it is difficult to completely stabilize the operations of a blast furnace and to improve the gas and liquid permeability by only using a high quality blast furnace coke.
An attempt in overcoming the problems described above, is found in Japanese Patent Laid-Open Publication No. 63206/1978. The disclosure discusses a method of operating a blast furnace for which coke is used, characterized in that 3 to 25% of the total charged coal materials by weight is replaced with high strength block made of fine carbonaceous materials, and where coke fine materials are mixed with the coke for use in the blast furnace.
With that method however, as the fines and high strength coke was charged into the furnace in place of the ordinary coke, the gas permeability was temporally improved, but the high strength block intruded into some areas other than the core section of the furnace. That condition lowered the furnace reaction efficiency of the entire furnace. Furthermore, the high strength blocks descended to the raceway section in front of the tuyere, which in turn, caused incomplete combustion of the coke, and in addition, oxygen to climb
REFERENCES:
patent: 4963186 (1990-10-01), Shimizu et al.
patent: 5486216 (1996-01-01), Shigeno et al.
Fujimori Hirotoshi
Kawai Takanari
Nakajima Yoshiyuki
Sakurai Syouji
Andrews Melvyn
Kawasaki Steel Corporation
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