JP2000096124A - Blowing method for restraining sticking of metal in converter type refining furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To melt and remove skull stuck to a furnace opening part and side wall in the furnace without damaging a refractory by adjusting pure oxygen flow rate in the gaseous oxygen jetted from nozzles for melting the skull arranged on the outer peripheral surface of a lance according to the dust concn. in exhaust gas generated during blowing molten iron. SOLUTION: The lance 5 is inserted into the furnace through the furnace opening part 4 from the upper part of a converter 3, in which the molten iron 1 and slag-making material 2 are charged. In the lance 5, an oxygen nozzle 6 for blow-refining is disposed at the lower end part and also, the nozzle 7 for melting the skull on the furnace opening part, is disposed at a prescribed position in the upper part from the lower end part, and the jetting direction from the nozzle 7 for melting the skull is made to downward or in the longitudinal direction in the range of about 40-90 deg. angle formed with the axial line 10 in the longitudinal direction of the perpendicular lance. The dust concn. in the exhaust gas 11 from the converter is measured with an exhaust gas dust concn. meter 12 and the pure oxygen flow rate in the gaseous oxygen jetted from the nozzle 7 for melting the skull, is adjusted according to this concn. to restrain the stuck quantity of the skull 8 stuck on the furnace opening part 4 and its constricting part 4a and the skull 8' stuck on the sidewall in the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter type refining furnace, in which the raw material charging operation into the furnace is performed smoothly, and the furnace port and the furnace inner wall are smoothly maintained. The present invention relates to a converter blowing method for suppressing adhesion of metal to the inner wall of a furnace.

[0002]

2. Description of the Related Art In converter refining, a part of molten steel and slag scattered by spitting and slopping generated during blowing is adhered to a furnace port and a furnace inner wall as metal. The deposited metal grows as the heat continues, and when its size exceeds a certain limit, it not only hinders the charging of hot metal and scrap, but also falls into the bath during blowing and melts down. Fluctuates in the composition of the components and the temperature, causing a major hindrance to the operation. If such adhered metal is not properly removed, there is a risk of damaging the underlying refractory. Therefore, it is necessary to remove the deposit metal before it becomes larger than the size that hinders the operation.

[0003] Traditional methods of removing furnace slabs include:
There is a method in which a scrap is hit against an ingot metal part and physically removed. However, in this method, since the scraps are directly hit on the metal slab, there is a risk that the bricks may fall off due to the impact. Further, Japanese Patent Application Laid-Open No. 4-354814 discloses a method of inserting a dedicated metal melting lance into a furnace from a furnace port during non-operation to melt and remove the metal adhered to the furnace port. (Prior art 1
). However, since this method must be performed when the converter is not blown, the time required for non-steel making is increased and converter productivity is significantly impaired. Therefore, a method has been proposed in which exhaust gas generated in the furnace during blowing is subjected to secondary combustion so as to dissolve and remove the furnace opening and the inner wall metal of the furnace so as not to impair converter productivity. For example, Japanese Patent Publication No. Hei 7-26141 discloses that in a total oxygen bottom-blowing converter, operation is performed at a ratio of one slagless blowing to one heat of normal blowing, and at that time, the upper blowing is performed during the bottom blowing. A method is disclosed in which oxygen gas is introduced into a furnace from a lance to dissolve and remove metal that has adhered to the vicinity of the furnace port (referred to as prior art 2). According to this method, it is possible to melt and remove the furnace mouth metal while securing the productivity. However, since the secondary combustion in the furnace is used, it is difficult to control the secondary combustion rate, and there is a problem that the refractory is easily damaged. Further, JP-A-8-12
No. 7812 discloses a method in which oxygen gas for blowing is blown from a lower end of a lance to hot metal while oxygen gas is injected from an outer peripheral portion of the lance toward a furnace inner wall to dissolve and remove ingots in the furnace. (Referred to as Prior Art 3). Also in this method, when the amount of deposited metal decreases, the refractory may be damaged.

[0004]

As described above, according to the prior art, it has become possible to remove in-furnace ingots while ensuring the productivity of the smelting furnace. However, the development of a technique for melting and removing ingots adhering to the furnace port and the inner wall of the furnace without damaging the refractory on the foundation is not sufficient. It is considered that the reason is that it was difficult to judge the adhesion state in the furnace during blowing, so that oxygen gas was empirically blown to dissolve the adhesion metal or to suppress the adhesion. .

[0005] In view of the above, the inventors of the present invention have developed a technique for dissolving and removing ingots of a converter furnace mouth and an inner wall of a furnace, on the premise that productivity is ensured. An object of the present invention was to develop a method for preventing the refractory from being damaged by excessive melting of the metal. The object of the present invention is to ensure the productivity of molten steel in a converter, and to prevent the refractory on the furnace port and the inner wall of the furnace from being melted and to properly manage the state of adhesion of the metal. To provide a refining method.

[0006]

Means for Solving the Problems In the meantime, in-furnace ingots tending to be formed rapidly over a wide area, particularly ingots adhering to a narrowed portion of a furnace opening, are uniformly removed while avoiding damage to the refractory underlayer. In order to dissolve the metal efficiently, it is important to control the metal adhesion and to dissolve and remove the metal in a time when the amount of metal ingot is large in one heat. did. The present inventors have found that a large amount of ingots in the converter are formed when the amount of dust generated from the furnace is large, and that appropriate oxygen gas for melting the ingots is blown at this time. As a result, the above problem was expected to be solved.

The present invention has been made on the basis of the above-mentioned findings, and a method for suppressing the adhesion of metal in a converter type refining furnace according to the present invention uses a hot metal as a main iron source by refining by top blowing or top and bottom blowing oxygen. In the converter type refining furnace, a blowing nozzle is provided at the lower end, a smelting nozzle is provided on the outer peripheral surface, and oxygen gas or purge gas is blown from the smelting nozzle to the oxygen gas for blowing. In a blowing method that uses a lance that can be controlled and supplied independently and suppresses the adhesion of metal to the furnace opening and / or the inner wall of the furnace, the refining furnace exhaust gas generated during the blowing of the hot metal The method is characterized in that the dust concentration in the inside is measured, and the pure oxygen flow rate in the oxygen gas injected from the smelting nozzle is adjusted to flow according to the obtained dust concentration. Here, the oxygen gas injected from the metal melting nozzle is generally pure oxygen, but may be any oxygen-containing gas, and may be mixed with an inert gas to lengthen the gas reach. It is. In addition, suppressing the adhesion of the metal includes dissolving and removing the metal that has adhered, and preventing the metal that is about to adhere from being adhered. Incidentally, industrial oxygen gas is generally used as the oxygen gas for blowing.

[0008]

Next, a preferred embodiment of the present invention will be described. FIG. 1 is a conceptual diagram of an example of equipment used to carry out the method of the present invention.

A lance 5 is inserted into the furnace through the furnace port 4 from above the converter 3 in which the hot metal 1 and the slag material 2 are charged.
The lance 5 is provided with a blowing oxygen nozzle 6 at the lower end and a metal melting nozzle 7 at a predetermined position above the lower end. The gas injection direction from the metal melting nozzle 7 is a downward or horizontal direction in which the angle between the lance and the longitudinal axis 10 of the lance set vertically is in the range of 40 to 90 °. As a result, the sliver attached to the furnace port 4 and its narrowed portion 4a (hereinafter referred to as "furnace slab" 8 unless otherwise specified) and the slab attached to the furnace inner wall "furnace inner wall slab" (particularly rejected) Unless otherwise stated, the furnace mouth metal and the furnace inner wall metal are collectively referred to as “metal”. The structure of the lance 5 includes an oxygen supply pipe for supplying oxygen gas to the blowing oxygen nozzle 6, an oxygen / purge gas supply pipe for supplying oxygen gas and / or purge gas to the metal melting nozzle 7, and a cooling lance. It has a quadruple structure with a water supply pipe and a drain pipe.
In this way, the supply path of the metal for melting metal can be controlled independently of the supply path of the oxygen for blowing. The upper part of the furnace port 4 is slidably sealed with the exhaust gas hood 9,
The converter exhaust gas 11 is recovered from the furnace port 4 through a duct. A dust concentration meter 12 for measuring the dust concentration in the converter exhaust gas 11 is provided in the middle of the duct.

Using the above equipment, molten iron 1 is refined by injecting a predetermined flow rate of oxygen gas from blowing oxygen nozzle 6.
On the other hand, oxygen gas is injected from the metal melting nozzle 7 to melt and remove the metal 8 attached to the furnace port 4 and its narrowed portion and the metal 8 'attached to the inner wall of the furnace. Here, the dust concentration in the exhaust gas 11 is measured continuously by the dust concentration meter 12 during the blowing period, and the flow rate of the pure oxygen in the oxygen gas for dissolving the metal is adjusted according to the dust concentration to feed the acid. The reason why the metal for melting metal is caused to flow in accordance with the dust concentration is that the rate of forming the furnace mouth metal is high when the dust concentration in the exhaust gas is high. The present inventors have found the relationship between the above dust concentration and the metal forming speed as follows.

FIG. 2 shows the result of measurement of the relationship between the elapsed time of one heat of decarburization blowing and the amount of dust generated using the dust concentration meter 12. According to this, the amount of generated dust is large in the early stage of blowing. FIG. 3 shows the relationship between the amount of dust generated at the beginning of blowing and the number of times the furnace mouth metal was removed during the operation period with a fixed number of heats in the conventional blowing method. According to this, as the initial dust generation amount increases, the furnace port metal removal frequency increases. Therefore, it can be seen from FIGS. 2 and 3 that the rate of formation of the furnace mouth metal is high at the early stage of blowing when the amount of generated dust is large.

In performing the ingot dissolving operation, the flow rate of pure oxygen in the ingot dissolving oxygen gas is increased according to the ingot forming speed. That is, as the metal forming speed increases, the flow rate of pure oxygen in the metal gas for melting metal increases. For that purpose, the dust concentration of the exhaust gas 11 is measured by the dust concentration meter 12, and the larger this is, the larger the pure oxygen flow rate in the metal gas for dissolving the metal is. By doing so, it is possible to suppress the adhesion of the base metal having an appropriate thickness without excessively dissolving the base metal, and to manage the state of adhesion of the base metal satisfactorily. Here, the oxygen gas flowing from the metal melting nozzle is
Generally, it is pure oxygen, but any oxygen-containing gas may be used. In order to extend the gas reach, it is possible to mix an inert gas. In addition, dissolving and removing the ingot includes preventing the ingot from adhering. Incidentally, industrial oxygen gas is generally used as the oxygen gas for blowing.

In addition, at the time when the ingot melting operation is not performed due to the low dust generation speed, for example, at the end of blowing, a purge gas is supplied from the ingot melting nozzle 7 to prevent clogging of the nozzle. Regarding the injection direction of oxygen for melting metal,
The angle θ of the lance with respect to the longitudinal axis 10 is 40 to
If the angle is 90 ° and the direction is downward or horizontal, the action and effect of dissolving and removing the base metal described above are large.

[0014]

The present invention will be described in more detail with reference to examples. The test method was such that a predetermined amount of 310 t of hot metal, 10 t of scrap, and slag-making material were charged into a 300 t converter, and decarburization and refining were performed with an upper blowing lance. The equipment used conforms to that shown in FIG. As an upper blowing lance, an oxygen nozzle for blowing is arranged at the lower end, and eight holes are provided at equal intervals on the outer peripheral surface from the lower end. 8 holes x 2 steps type was used. The shape and specifications of the nozzle and the mounting angle of the nozzle were variously changed.
The flow rate of blowing oxygen is 750 to 1000 Nm ³ / min.
And the flow rate of the oxygen for dissolving the metal was in the range of 3 to 10% of the flow rate of the oxygen for blowing at that time.

On the other hand, the dust concentration in the exhaust gas was measured by a densitometer throughout the blowing period. Oxygen flow rate Q
(Nm ³ / min) to the dust concentration q (mg / N
m ³ ) with a linear function. However, in the period after the analysis sample collection and temperature measurement by the sublance performed at the end of blowing, the oxygen gas for dissolving the metal was stopped in principle and switched to the purge gas.

A cycle in which the heat by the blowing method for melting the metal was discharged for 10 charges, and then the heat for the blowing method without melting the metal was discharged for 20 charges was repeated 10 times. Then, after the tapping of the ingot melting heat was performed, the ingot adhesion on the furnace port and the inner wall of the furnace was visually observed. As a result, it was confirmed that the state of the deposited metal in the furnace was well controlled without damaging the refractory of the foundation.

[0017]

As described above, according to the present invention,
It is possible to provide a method for efficiently suppressing the adhesion of the furnace mouth metal while suppressing damage to the furnace mouth refractory without impairing the productivity in the converter type refining furnace, which is an industrially useful effect. Is brought.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an example of equipment used to carry out a method of the present invention.

FIG. 2 is a graph showing changes in the amount of dust generated during one heat of decarburization blowing.

FIG. 3 is a graph showing the relationship between the amount of initial dust generation and the frequency of furnace mouth metal removal.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 hot metal 2 slag-making material 3 converter 4 furnace port 4a squeezed portion 5 lance 6 blowing oxygen nozzle 7 furnace port smelting nozzle 8 furnace port slab 8 'furnace side wall metal 9 furnace port hood 10 shaft center Wire 11 converter exhaust gas 12 exhaust gas dust concentration meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kanji Hiji 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Taizo Sera 1-2-1, Marunouchi, Chiyoda-ku, Tokyo No. Nihon Kokan Co., Ltd. F-term (reference) 4K002 AB01 AC05 AC07 AD02 AF03 BA10 BB10 BE03 BF01 BF02 BF03

Claims (1)

[Claims] 1. A converter type refining furnace for performing refining by using top blown or top and bottom blown oxygen using molten iron as a main iron source,
A blowing nozzle is provided at a lower end, and a metal melting nozzle is provided on an outer peripheral surface, and an oxygen gas or a purge gas is supplied from the metal melting nozzle to be controlled independently of the oxygen gas for blowing. In a blowing method that uses a lance that is capable of preventing the metal from adhering to the furnace opening and / or the inner wall of the furnace,
The dust concentration in the exhaust gas of the refining furnace generated during the blowing of the hot metal is measured, and the pure oxygen flow rate in the oxygen gas injected from the metal melting nozzle is adjusted according to the obtained dust concentration to flow. A method for suppressing and blowing metal ingots in a converter type refining furnace.