JPS58113311A - Protecting method for tuyere for blowing oxidative gas for refining - Google Patents

Abstract

PURPOSE:To prevent chemical erosion owing to FeO, SO2, etc. of refractories, by protecting the peripheries of tuyeres with an inert gas contg. a force reducing agent in the form of powder and maintaining the refactories around the preceding ends of the tuyeres in a reducing atmosphere. CONSTITUTION:A titled method is a method for protecting the surroundings of tuyeres to be used for blowing of oxidative gases under the surface of the molten metal contained in a refining vessel by the releasing gaseous flow that encloses the same like a sleeve. A gas inert to the molten metal contg. the powder reducing agent is used for said releasing gaseous flow. More specifically, a gaseous mixture of argon and carbon powder or nitrogen and carbon powder is used, and kish graphite is preferable as the carbon powder. Then, the refractories around the preceding ends of the tuyeres are maintained in a reducing atmosphere and are protected against chemical erosion by the FeO, SO2, formed around the ignition parts in front of the preceding ends of the tuyeres.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for maintaining tuyeres for blowing oxidizing gas for refining, and particularly advantageously increases the durability life of the tuyeres by increasing the cover for collecting water in the molten metal. It is intended to make it possible to do the same as above.

Among steelmaking furnaces, pure oxygen bottom-blowing converter (commonly known as Q-BOP).

or OEM) or top-bottom blowing combined converter (commonly known as -B
In the case of OP or LD-OB), a lambda double tube type tuyere is buried in the bottom of the furnace, and pure oxygen gas is supplied from the inner tube of this double tube type tuyere to the bath water assembly line, and from the outer tube of the kettle. A hydrocarbon gas such as propane is blown into the molten metal. Of these, the hydrocarbon gas decomposes into C and H2 at the hot part of the tuyere tip, which is opposed to molten iron.At this time, the surrounding molten iron solidifies and adheres to take away the decomposition m, playing the role of preserving the tuyere tip. There is.

When the hydrocarbon gas is propane, the current is usually about 3% of the oxygen gas flow flowing through the inner pipe, and in the case of normal ordinary steel blowing, the oxygen gas consumption rate is about 1 ton of molten steel. Hit san〇-! Since it is ONm3, the propane consumption rate is the same (
/,,2~/,j Nm, which is not only quite expensive, but also the biggest drawback of the conventional technology that uses hydrocarbons as a protective gas is that the N2 gas generated by decomposition is absorbed into the molten steel, so it is difficult to manufacture. This would impair the quality of the steel used.

Therefore, the inventors solved the problem without increasing hydrogen in molten steel.
The present invention was completed by researching various protective fluids that have at least the same tuyere protective effect as the prior art, on the condition that the fluid is cheaper than hydrocarbon gas.

There were no proposals for staying in the United States based on this perspective.

For example, when hydrocarbons are used as mentioned above, propane in volume % relative to oxygen has its sensible heat (2j
℃→1too℃) by adding decomposition heat to oxygen/Nm'/Hiroshi0. j Since the amount of heat removed by Kcal is estimated, we chose hydrocarbons to achieve a cooling effect commensurate with this amount.

Attempts have been made to find alternative siding protection fluids, for example, by mixing carbon powder with carbon dioxide gas and utilizing the fact that the reaction of CO□+C→200 is an endothermic reaction (JP-A-Sho st.
The basic idea was the same insofar as protection was sought by cooling the tip of the tuyere (Publication No. 7/I).

As the inventors continued to closely examine trends in the actual operation of steelmaking using bottom-blowing converters, they found that one of the causes of the melting of the tuyeres was that the refractory material around the tips of the tuyere It has been newly discovered that the material is chemically eroded by FeO, depressions 2, etc. generated at the points.

Based on such new findings, this invention has been developed through studies and experiments on protection against chemical corrosion, and has developed a new and useful tuyere protection measure by keeping the refractory around the tip of the tuyere in a reducing atmosphere. It has been established since then.

This invention relates to a method for protecting a tuyere by a discharge air flow that wraps around 1゜ of the tuyeres in a sheath below the bath surface of molten metal contained in a refining vessel, which is used for blowing in oxidizing gas. A tuyere for smelting and oxidizing residue injection that uses the forced reducing property of powder to keep things in a reducing atmosphere mixed into the carrier gas, which is virtually inert to the bath water, to protect the tuyere. It is particularly advantageous for the siding protection fluid to be a mixture of argon and/or nitrogen and carbon powder, and for the carbon powder to be Quiche graphite.

According to this invention, the refractory surrounding the tuyere tip is placed in a reducing atmosphere by a forced reducing agent, such as carbon powder, which is successively carried there by a carrier gas, so that the fire point formed in front of the tuyere tip is The generated FeO, SiO□, etc.
Since the refractory is reduced before chemical attack occurs, the causes of erosion and wear of the siding can be advantageously eliminated.

In the acid Mixed lr or N2 gas, or a mixed gas of Ar and N2 is used. Like this A
The reason for using inert scum such as r, N2 is that (1) the carbon powder does not react in the blowing channel up to the tip of the tuyere, and (2) hydrogen is absorbed into the molten steel and impairs the quality of the steel. The main reason is that it does not include

The carbon powder used as a reducing agent for FeO is powdered coke,
Although various other forms can be used, it is particularly desirable to use quiche graphite, which has excellent slipperiness due to the amount of powder, there is no risk of clogging the blowing midstream passage, and - This is because it is inexpensive because it can be recovered from the dust as a by-product in the process of charging molten pig iron into a converter in a steelworks.

In a normal λ double tube tuyere, the gap in the annular portion through which the jacket gas passes, ie, the gap between the inner and outer tubes, is less than 0/IM. This is because if the gap is made larger, the dynamic pressure of the protective gas becomes smaller, which may cause problems such as insertion of molten steel. On the other hand, in this invention, solid carbon powder must be blown through the annular part. At this time, in order to prevent the annular part from clogging with the carbon powder, it is preferable that the annular part gap be as large as possible. In order to avoid a drop in gas dynamic pressure, gas consumption increases unnecessarily.

Therefore, extreme care must be taken when blowing powdered carbon.

According to the experience of the inventors, even from the annular part of Example 1/II, if the particle size of the carbon powder and the carbon powder blowing rate per unit of gas are appropriately selected, the powder can be formed without any problems without any knots. Carbon blowing is possible. For example, the inner tube outer diameter is /4Ej
ul, if the gap with the outer tube is 7 squares, the particle size is 7Qμ
The following carbon powder was blown at a blowing speed of 1j 10 n/am5.
It is known that there is no problem in blowing with N2.

If the amount of powdered carbon injected is too small, the protection of the refractory around the tip of the tuyere will be insufficient, and if it is too much, it will cause clogging during the blowing process, and a slow rate of decarbonization at the end of the blowing can due to carbonization. Since problems such as grinding may occur, an appropriate value should be selected depending on the blowing conditions and the type of steel manufactured.

According to the experience of the inventors, the conditions for blowing the protective gas according to the present invention are preferably within the following range.

Molten iron/per minute, protective gas blowing speed m'tq
. (Nm 7 mln-t), q carbon powder blowing rate per minute per molten iron. (/cg/m1n-t
), and the linear velocity of the protective gas in the piping converted to standard conditions is U
g (Vii60), in order to prevent clogging with powdered carbon, the condition qO//qo≦io must be satisfied, and in order to effectively protect the refractories around the tuyeres, q. The condition is to satisfy the condition ≧0.0.

Note that if the flow rate of the protective gas is too large, it will lead to a decrease in thermal efficiency and is also uneconomical. The condition of ≦0.6 is preferable, and on the other hand, in order to smoothly transport the powdered carbon, it is preferable that Ug≧IO in the conduit through which the protective gas passes.

Examples of the present invention will be described below along with comparative examples.

Example 1 Bath iron! , cort(≠,j%Q ,0.!0%si
, o, i%Mn, 0.10!1%p, 0.
007%s, 1rto℃)'ijt was charged into a bottom-blown converter. This converter has λ double tube tuyeres arranged in a straight line at the bottom of the furnace, with an inner tube inner diameter of io ymgt, an inner tube outer diameter of 1 uw x ll, and an annular part gap/Ill. Of the main tuyere, φl, S2.
The +3 was conventionally cooled using propane as the protective gas, while the +3 used a mixture of nitrogen gas and a powdered rare element as the protective fluid according to the invention.

The total oxygen delivery rate is HNm'/min, tuyere ◆i, +2
, ÷ 3, each propane flow rate is 31% as a ratio of the flow rate to IIS per day, and the nitrogen flow rate of the tuyere ◆hiro is IO% as the ratio of oxygen to oxygen per tuyere, and the amount of powdered carbon blown is O1
The carbon powder used was coke with a particle size of under 70μ.

The amount of burnt lime used is 120 kl of lumps added to the furnace at the beginning of blowing, and powder AOK4I mixed with oxygen gas at the beginning of blowing.
- Added by bottom blowing, and further added tokg of powder by bottom blowing at the end of blowing.

The blowing was completed by blowing a total amount of oxygen of ≠4 Nm.

The stopper component and mu are 0.02%Q, 0. (73%
Mn.

o, oii%P, 0.006%S, 1637℃
Met.

Immediately thereafter, the steel was tapped, the furnace was cooled, and the diameter of the pine mushrooms produced in each wall was measured. The results were as follows.

Tuyere φl Pine mushroom diameter Hiro 3II Eda I
φλ Da deceive fI φ3
Reference t4 Iris φ≠
Based on the experience of the inventors, it can be concluded that the larger the matsum, the less the tuyeres are eroded, and therefore, the protective fluid of the present invention has better blade retaining ability than conventional propane gas.

Example 2 Hot metal z, g t (a, A%c, o, 34c%Si
, 0,173%Mn, 0. IJI%p, 0
．． 0JO%S, /λrj”o) as in Example 1, 11
It was charged into a bottom blowing converter. +1 inside the main tuyere. λ, ◆
3 was cooled using Grono 2 as the protective gas as before, while the tuyere φHiro was cooled using a mixture of argon gas and powdered carbon as the protective fluid according to the present invention. The total oxygen delivery rate is /j
Nm/mln% The propane flow rates for each of the feathers rona/, +co, and su3 are 3% by weight relative to the oxygen flow rate of the tuyere/truck, and the argon flow rate of the tuyere + tuyere is the oxygen flow rate per tuyere. 1 in ratio
% by weight, and the amount of powdered carbon blown into ginseng is 0. /ψ Hayabusa 3 Co., Ltd. In this case, Quiche graphite crystallized during cooling of the blast furnace bath I was recovered and used as the carbon powder. This quiche graphite was scaly, and the average diameter of the scaly surface was on the O side.

The amount of burnt lime used was that 20 kl of fluid was charged from the furnace mouth at the beginning of blowing, powder aokg was added by bottom blowing together with oxygen gas at the beginning of blowing, and totq powder was added by bottom blowing at the end of blowing.

A total amount of oxygen of -61 Nm3 was blown in to stop the blowing. The blowstop components and temperatures are o, o%o, o,io%Kn,
0.0/l%P, 0.0/l%S, /1r
Jj ”Oteh ft.

Immediately thereafter, the steel was tapped, the furnace was cooled, and the diameter of the pine mushroom formed at the tip of the tuyere was measured by entering the furnace.

The results were as follows.

Wing Rona l Pine mushroom diameter μ/111+f
lI φ2' JIam+
Guls3 Doug4gu' ◆
4' It can be concluded that the protective fluid used in the 1 case of Hiroshima Dakoreyo is comparable in terms of tuyere protection ability compared to conventional propane gas. .

Hot metal j! t (Reference, Reference%a, o, az%Si,
0.2l%Mn.

o,ii@p, o,ooy%S, /2171'
Example 1.2 and Okaji Jt bottom-blowing converter were charged with O).

The Hiromoto tuyeres of this converter all used a mixture of argon gas and powdered carbon as the protective fluid in accordance with the present invention.

The total oxygen delivery rate is /j Nm/min s The flow rate of argon gas, which is a protective gas, is IO volume % as a ratio of the flow rate to oxygen. Coke with a particle size of under 70 μm was used as the powder.

The amount of burnt lime used is as follows: Fluid 1λotq is charged from the furnace mouth at the beginning of blowing, powder 1/-Okfl is added by bottom blowing together with oxygen gas at the beginning of blowing, and g is added to powder iao by bottom blowing at the end of blowing. Added circles.

The total amount of oxygen Hm was blown into the tank to stop the blowing. The blowstop ingredients and temperature are o, ois%0, 0,11%In
, 0.01Jfkp, o,ooy%S, /4
70℃, 1. It was ppm H.

On the other hand, in the experience of multiple heats using propane as a protective gas, the blow-stop H concentration under uniform blowing conditions as in the above example is extremely significant, at 7 to P ppm. The preventive effect is significant.

In addition, after the steel was tapped and cooled in the furnace, the diameter of the pine mushrooms formed at each tuyere was measured. The results were as follows.

Feather Rona L Pine Shroom Diameter 7λul12
74! 1111 da J
70 ff1l (e
tram〆From this, it can be seen that the protective fluid of the present invention is superior to the conventional propane gas, which was used for pine mushrooms with a diameter of JJ' to 1 m.

The above embodiments have described the application of the present invention to a pure oxygen bottom-blown converter, but similar effects can also be achieved in a converter for refining, a converter using an oxidizing gas injection tuyere, or a converter with bottom blowing. bring, and furthermore, like a mu OD furnace, mu r +
Even when O□ is used as a refining gas and Ar is used as a storage gas, the benefits of applying this invention are significant.

Thus, in contrast to the conventional method for refining, oxidizing gas injection, and tuyere maintenance, which relies on a cooling effect that utilizes the reaction heat of protective gas in the furnace, this invention Based on a thorough investigation of the cause of tuyere melting, which involves the chemical attack of refractories by reaction products at the fire point formed by the injection of oxidizing gases, we found that inert gas and powder By using a mixture with a reducing agent, a remarkable and useful preservation measure has been newly established, and the durability life of the tuyere can be advantageously improved without increasing the hydrogen content in the molten metal.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Scope of Claims] 1. A method in which a tuyere for blowing oxidizing gas is maintained under the bath surface of molten metal contained in a refining vessel by a discharge air flow wrapped around the tuyere in a sheath shape, A powdered forced reducing agent that keeps the refractory around the tip of the mouth in a reducing atmosphere is applied to ff4.
Practically unfit for hot water! A method for protecting an oxidizing residue injection tuyere for refining, characterized by using a tuyere protector mixed in a carrier gas consisting of an i-prone gas. 2.%Iv where the tuyere maintenance fluid is a mixture of argon and carbon powder! P Claims 1.1 Self-published method. 6. The range of special properties in which the fluid is a mixture of nitrogen and carbon powder 1. Method described. 4. Claim 2 in which the carbon powder is black-and-white graphite.
or 3. Method described.