JPS58123812A - Operating method of converter - Google Patents

Abstract

PURPOSE:To enable operation under the stable burnout of a tuyere over a long term by regulating the flow rate of a gas blown from the bottom of a converter to prevent the burning of a nozzle and the wear of brick due to bubble backing phenomenon. CONSTITUTION:A bottom or top and bottom blowing converter is operated while regulating the speed of an oxidizing gas ejected from the tip of a nozzle as a refining gas contg. O2 blown under the surface of a bath to the range represented by equationIor II in accordance with the inside diameter of the nozzle. As a result, the abnormal burnout of the nozzle and the wear of brick can be prevented, and the operating and repairing costs can be reduced considerably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bottom-blown or top-bottom blown converter operating method that reduces the amount of wear on the immersed siding.

Many studies have been conducted on bottom-blown gas conditions for reducing tuyere wear in bottom-blown or top-bottom blown converters, and a great deal of knowledge has been obtained so far from the patent documents listed below.

b) Concerning appropriate cooling gas conditions for double tube tuyere (Japanese Patent Publication No. 54-20443, JP55-161015); (3) Concerning nozzle structure (Japanese Patent Publication No. 54-163715, JP-A Showa 55-24
948 Publication, Gathering FF155251787 Publication), etc.) related to the type of blown gas (Japanese Patent Application Laid-Open No. 53-131916, Japanese Patent Application Laid-Open No. 56-13
423 Publication, Japanese Patent Application No. 56-33549), etc. 2) Regarding the discharge flow rate (#86203 Publication No. 1987, Japanese Patent Application No. 1982-649) etc.
No. 20, Patent Application No. 1984-64921, Patent Application No. 1982-75
No. 861), etc., and the discharge flow rate of item 2) is closely related to damage to the bottom tuyere due to the so-called bubble regression phenomenon.

However, the knowledge regarding the conventional discharge speed (Japanese Patent Application No. 1983)
-64920, patent application No. 1983-64921, patent application No. 1973
No. 0-75861) 10 relating to the injection of oxidizing gas into line membrane gas equipment, invention in the area where the bath depth is limited to within 0.5 m), bottom-blown converter having a bath depth of 1 to 3 m Otherwise, it cannot be applied to a top-bottom blowing converter.

In addition, the invention described in Japanese Patent Application Laid-open No. 49-86203 discloses that the oxygen discharge rate of a bottom blowing converter is "at least 85 Nm"/my from a nozzle diameter of 1/13 of the bath depth to an oxygen tube with a nozzle cross-sectional area of It stipulates that the air pressure is 1 atm to 15 atm.
11 (3”) - (1~3) x bath weight (TON)
It is defined as J and 9.

However, the scope of this proposal is very wide, and in experiments conducted by the present inventors, the contact of molten steel with the nozzle is intense at low flow rates, and
The nozzle itself ignites 1 time, only 1 time, 6 too much during the 11 blowing time also causes loss ^ Regular (jI
This phenomenon occurs frequently, and in the Kutakataki kettle, there is considerable wear and tear on the bottom of the furnace, especially on the siding and seam f, due to the bubble regression phenomenon that accompanies the increase in the discharge flow rate, and there is no possibility of preventing it.

The objective of the present invention is to prevent brick wear due to abnormal erosion due to large nozzle combustion and bubble regression phenomenon caused by excessive discharge flow rate, which cannot be solved by conventional methods.The present invention achieves this objective. The basic technical idea is to set upper and lower limits on the discharge speed of the blown gas.

In order to solve the problems of the above-mentioned conventional method, the present inventor conducted various experiments and obtained the knowledge shown in FIG. 1 and m2rms FIG. 3.

Iris 1 is a top-bottom blowing converter with a capacity of 340T/h@at, and the bath depth is 3 levels of 1200, 1700, and 2000■.
Fr'w 2. O ~ 5.9, nozzle @
The relationship between the erosion rate and Fr' as a result of operation with a diameter of 18φ to 33φ is shown in Figure 1. The shaded areas all indicate abnormal erosion due to nozzle combustion. y) When Fr' is increased, the erosion rate increases, and when it decreases by 1, nozzle combustion occurs. Regarding the problem of dosage for II, in order to reduce the erosion rate to below 1 (3■/ah), apr'<4.5 is required for a nozzle diameter <27φ, and yr/3. Must be 5 or less. In addition, with Fr' (,3,0, there is a risk of nozzle ignition, which is difficult to operate.
Change CFr' from 3.3 to &9 and turn on at 9 o'clock! When 6 ru Fr' 3.3 with a moderate transition, #I loss rate is 1.3■/e
It was k.

When increasing to Fr'5.9, the simultaneous K11l loss rate ti6.7
mm /@h, and spalling of the hearth bottom tuyere also occurred frequently.

No. 3 had a Fr' of 3.3 during continuous operation in the same top-bottom blowing converter.
This figure shows the change in the nozzle tip opening area ratio when lowering from 2.5 to 2.5.The opening area ratio is calculated backward from the flow rate-pressure characteristics and is 900 million. In operation at Fr' = 3.3, the tip opening ratio is stable with a predominance of 75, but immediately after shifting to Fr I = 2.5, the tip opening ratio decreases to 50-, causing contact with molten steel to the nozzle tip. shows that there is a rapid increase. During this period, there were 4 cases of abnormal erosion due to nozzle combustion) and abnormal erosion due to insufficient flow rate.

Based on the above, the discharge flow velocity range that can prevent normal melting loss and brick wear is certain. In the Takabuki Matahiro top-to-bottom blowing converter furnace, which blows a saponifiable gas containing oxygen under the bath surface, % oxidation is performed to reduce melting loss and spalling of the soaked feathers and refractories around the tuyeres. The nozzle tip discharge speed of the refining gas should be operated within the following range: (1) nozzle inner diameter 27 (27) nozzle inner diameter > 27 (3.0<;: Fr'<3.5).

Examples of the present invention will be described below.

340T/h@at top-bottom blowing converter with 750 liters of oxygen
0ONm”/krs bottom-blown oxygen 1500-8000 Nw
h”/hr, the nozzle tip discharge speed was varied by 5.9 m from L5 using Fr' as an index.
In operation at less than 271, melting of one nozzle frequently occurred below Fr'lJi, resulting in an unoperable state. The f#I loss could be suppressed to a level that would not pose a practical problem when operating at Fr'4.5 or less. When operating at II27 wm or higher in the nozzle, the area with good brick erosion shrinks to a low flow rate9.
, Good results can be obtained with Fr/≦3.5.

Example operating conditions: Furnace volume: 340 T/'heat % Steel type: At-K.

To Muj-111-, oxygen amount; top blowing 7500ON@'/h
r, bottom blowing 1500 to 800 ONm'/hr operation results (Note) According to the present invention described above, by regulating the bottom blowing gas discharge flow rate, nozzle combustion is prevented and brick wear due to bubble regression phenomenon is prevented. The benefits of this method are significant, such as the ability to prevent tuyere melting and stable operation over a long period of time, and greatly reduce operating costs and repair costs.

[Brief explanation of the drawing]

The first @ has a bath depth of 1200-2000cm, a nozzle inner diameter of 18-33cm, and t! A diagram showing the relationship between Fr' and the erosion rate when operating at I, the first intention is a diagram showing the fluctuation of the erosion rate at 9 o'clock when the bottom blowing gas discharge rate is changed to Takataki speed in the middle of the furnace, 3rd m! 1 is a diagram showing the transition of the nozzle tip opening ratio when the bottom blowing gas discharge speed is changed to a low flow rate in the middle of the furnace. In Figure 1: + Bath depth 1700s+a Yellow Bath depth 1200m Bulk 1 Figure 2 Furnace softening

Claims (1)

[Claims] In a bottom-blown or top-bottom blowing converter furnace in which an oxidizing gas containing oxygen is blown below the bath surface as a refining gas, melting of the immersion tuyeres and refractories on both sides of the tuyeres, A converter operating method characterized by operating the nozzle tip discharge speed of oxidizing refining gas within the following range in order to reduce polling. ■Nozzle inner diameter〉27■ rr': Modified Froude number - 5; Oxidizing gas density, however, p: @R - Density of pig iron g: Acceleration of gravity■; Steel bath severity