JP2000129322A - Lance for blowing pulverized fine coal into blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lance resisted to hot blasting at a specific surrounding temp. without applying water-cooling and excellent in durability by constituting the lance of a tube formed of oxide dispersion type iron base alloy containing a specific ratio of yttria (Y2O3). SOLUTION: This lance is composed of the tube formed of the oxide dispersion type iron base alloy containing 0.1-1.0 mass % yttria (Y2O3) and resisted to the hot blasting at the surrounding temp of about 1200 deg.C. Desirably, the iron-base alloy contains, by mass, 18.0-20.0% Cr, 4.0-6.0% Al and 0.1-1.0% Ti. Further, the iron base alloy has excellent heat resistance and at the same time, in the improvement of a creep strength without causing such trouble as hang- down of the lance. The blowing lance has the structure of inserting the lance 3 for blowing pulverized fine coal, which is constituted of a metallic pipe, into a blowing pipe 1 arranged on a blast furnace wall and a tuyere 2. In the case of the oxide dispersion type alloy-made non-water cooling lance, the continual use having >=1 year can be obtd. and the remarkably excellent durability in comparison with a heat resistant steel-made non-water cooling lance, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lance for blowing pulverized coal into a blast furnace (hereinafter sometimes referred to as a lance).

[0002]

2. Description of the Related Art Pulverized coal injection into a blast furnace is known as a technique for reducing costs by using pulverized coal as a substitute fuel for coke, which is an expensive blast furnace fuel. As shown in FIG. 2, the blowing is performed using a blowpipe 1 provided on a blast furnace wall (not shown) and a pulverized coal blowing lance 3 inserted into the tuyere 2.

[0003] The pulverized coal blowing lance 3 is composed of a metal tube 4 as shown in FIG. 3, and a water cooling space 5 is formed as shown in FIG. There are also things.

[0004]

The above-mentioned lance for pulverized coal injection is conventionally made of heat-resistant steel (mainly SUS310S).
When used as a non-water-cooled pulverized coal injection lance having the structure shown in FIG. 3 above, the lance is always exposed to hot air at about 1200 ° C. receive. As a result, there is a problem that the lance life is extremely short, about two months.

On the other hand, when used as a pulverized coal injection lance having a water cooling structure (hereinafter referred to as a water cooling lance) shown in FIG. If the outer diameter becomes larger and a water-cooling lance is inserted into the tuyere, the flow path of the hot air becomes narrower and the blowing pressure increases. In particular, in order to inject a large amount of pulverized coal, it is preferable for the blast furnace operation to inject the pulverized coal with the tip of the lance as close to the tuyere as possible. In many cases it was not possible. It is also possible to select a water-cooled lance with a small outer diameter, but in this case, the diameter of the inner pipe, which is the pulverized coal flow path, is also reduced, and the flow resistance of the pulverized coal in the lance pipe increases. In addition, there is a problem that the amount of pulverized coal to be blown must be reduced due to the limitation of the capacity of the pulverized coal blowing device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a blast furnace which withstands hot air at a use environment temperature of about 1200 ° C. without water cooling and has relatively excellent durability. And a lance for blowing pulverized coal.

[0007]

To achieve the above object, according to the solution to ## pulverized coal injection lance into the blast furnace according to the present invention, oxide dispersion comprising 0.1-1.0 wt% of yttria (Y ₂ O ₃₎ It consists of a tube made of a type iron-based alloy.

In recent years, a large amount of pulverized coal has been blown into a blast furnace. For this purpose, as described above, a non-water-cooled type in which pulverized coal can be blown in without narrowing the hot air flow path and increasing the blowing pressure. It is desirable to use a pulverized coal blowing lance and arrange the tip so as to be as close to the tuyere as possible. However, in this case, the conventional non-water-cooled pulverized coal injection lance made of heat-resistant steel (mainly SUS310S) is easily melted and has a very short life. Then, the present inventors examined and studied the cause of the erosion, and found out from the research results that the lance was caused by the carbonization of the material in a high-temperature field. That is, the lance starts softening when exposed to a high temperature of 1200 ° C. or more, which is the operating environment temperature. At that time, if a carbon-containing substance (for example, pulverized coal) is present in the vicinity, the carbon dissolves in the lance or undergoes solid phase diffusion. As a result, the metal structure changes and becomes brittle. It is considered that erosion was caused by such a mechanism.

Based on the above research results, the present inventors have paid attention to an alloy in which yttria is dispersed, which has recently attracted attention in the field of heat-resistant composite materials, and manufactured an oxide-dispersed iron-based alloy containing yttria. Using a heat-resistant material (SUS310S, SUS304) used for a lance, carbonization characteristics (hardness of carbonization) in a high temperature field were investigated. As a result, the relationship between the amount of carbonization and the elapsed time was investigated at a high temperature of 1100 ° C. From the results shown in FIG. 1, the amount of carbonization hardly increased even when the iron-based alloy in which yttria was dispersed for a long time. It was found that the carbonization characteristics in the field were excellent. FIG.
In the above, a is an example of the present invention, and b is a comparative example (SUS310
S) and c show a comparative example (SUS304).

[0010] The mechanism by which the iron-based alloy in which yttria is dispersed suppresses the amount of carbonization is not yet clear, but if the amount of yttria is 0.1 or more, the amount of carbonization hardly increases even after a long time. Therefore, the amount is set to 0.1 to 1.0% by mass in consideration of economical aspect. Also,
Although the iron-based alloy is not particularly limited, Cr: 18.0 to 2
An iron-based alloy containing 0.0% by mass, Al: 4.0 to 6.0% by mass, and Ti: 0.1 to 1.0% by mass is preferable because it has excellent heat resistance and improved creep strength and eliminates problems such as lance sag.

[0011]

[Example] Cr: 19.2% by mass, Al: 4.8% by mass, Ti: 0.6
Mass%, Y ₂ O ₃ : 0.4 mass%, a non-water-cooled lance manufactured from an oxide dispersion type alloy consisting of the balance Fe and a non-water-cooled lance manufactured from a conventional heat-resistant steel (SUS310S) for comparison, These lances were used for pulverized coal injection into the blast furnace, and the life of each lance was compared and investigated. as a result,
The non-water-cooled lance made of an oxide-dispersed alloy according to the present invention can be used continuously for one year or more, whereas the conventional non-water-cooled lance made of heat-resistant steel (SUS310S) is as short as about two months. The non-water-cooled lance made of an oxide-dispersed alloy according to the above was much more durable. In addition, the pulverized coal was blown at a desired amount during the period without any trouble in the blowing pressure or the like.

[0012]

As described above, according to the lance for injecting pulverized coal into a blast furnace according to the present invention, the lance can be introduced into the blow pipe and the tuyere without water cooling and without impeding the hot air flow path. By inserting and arranging it, it can withstand hot air at a working environment temperature of about 1200 ° C. and continuously blow pulverized coal into the blast furnace for a long time.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of carbonization and the elapsed time when the high temperature field is 1100 ° C.

FIG. 2 is a partially sectional explanatory view for explaining a use state of a lance for blowing pulverized coal.

FIG. 3 is a cross-sectional explanatory view of a tip portion for describing a form of a non-water-cooled type pulverized coal blowing lance.

FIG. 4 is an explanatory sectional view of a distal end portion for explaining a form of a water-cooled type pulverized coal blowing lance.

[Explanation of symbols]

 1: Blow pipe 2: Tuyere 3: Lance for pulverized coal injection 4: Metal tube

Claims (2)

[Claims] 1. A method for producing yttria (Y ₂ O ₃ ) in an amount of 0.1 to 1.0% by mass.
A lance for injecting pulverized coal into a blast furnace, comprising a tube made of an oxide-dispersed iron-based alloy containing: 2. The iron-based alloy contains Cr: 18.0 to 20.0% by mass, Al:
2. A lance for blowing pulverized coal into a blast furnace according to claim 1, wherein the lance contains 4.0 to 6.0% by mass and Ti: 0.1 to 1.0% by mass.