JPS5856006B2 - Continuous smelting furnace with a reaction chamber dedicated to desiliconization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to equipment for more efficiently refining molten metal when refining it continuously.

The molten metals here refer to molten iron, molten pig iron, molten iron alloys (for example, iron-manganese alloys, etc.), and smelting refers to silicon, phosphorus, and sulfur (hereinafter referred to as S) contained in the molten metals.
Denoted as i, P, S.

) refers to the reaction aimed at removing
At this time, manganese and iron (hereinafter referred to as Mn and Fe) coexist.

) etc. will inevitably transition to slag.

Continuously refers to an operation that assumes that molten metal is supplied to and taken out of the refining vessel without interruption.

The following explanation will be given using hot metal, which is a type of molten metal, as an example.

In the oxygen steelmaking method, which uses hot metal as the main raw material, pure oxygen (hereinafter referred to as 02) is used.

) by spraying or blowing.

Si 102→S i02 The reaction removes Si from the hot metal.

Quicklime (Cab) charged as an auxiliary material (raw material for slag) for deP and S removal is melted and turned into slag, and then the bath is oxidized in the coexistence of slag from 02t to perform deP and S removal. A common task is to measure the temperature.

In this way, Si in molten metal is an essential component for slag formation of sub-materials, but on the other hand, Si produced by oxidation
iO2 is considered to be an acidic component and is an undesirable component for refining reactions.

The purpose of using quicklime as an auxiliary material is to neutralize these acidic oxides with basic oxides and make the slag basic for the refining reaction. ) / (S i02 ) is commonly used.

The basicity is targeted to be 3 to 4 for the blow-off slag used in the oxygen steelmaking process, and 1 to 2 for the preliminary film P intended for deP treatment at the hot metal stage.

On the other hand, when considering deP in a bath where Si coexists, P in the bath must be oxidized to P2O5, which is fixed in the slag as a calcium salt.
Due to competitive oxidation of Si, oxidation of P occurs, but a phenomenon is observed in which only <<Si is preferentially oxidized, and the Si range where this phenomenon occurs is generally considered to be 0.5% or more.

Furthermore, in order to perform refining (de-P, de-S), quicklime must be added to ensure the basicity of the slag, as described above.

From this point of view, as the amount of Si removed increases, the amount of quicklime added also increases, and naturally the amount of slag also increases.

If the amount of slag increases, unfavorable results such as a decrease in iron yield and a decrease in thermal efficiency will occur.

Considering that there are Si regions in which P removal does not proceed in the high Si region as mentioned above, in this high Si region, only Si removal is performed without expecting P removal, and Si below a certain value is
It can be seen that it is reasonable to perform P removal only in the Si region, that is, the Si region where Si removal and P removal occur in parallel.

That is, in the high-Si region where P removal is difficult to proceed, it is advisable not to remove P at all, but to perform only Si removal under the least slag generation conditions at this stage.

However, in refining based on basic auxiliary materials, SiO2 becomes an essential component for refining.

Namely. Under general refining using CaO, Ca
It is necessary to increase the solubility of O to make it easier to form slag, and to suppress the volatilization of alkali metals in refining using alkali metal compounds, so that the alkali metal compounds can be used effectively in refining.

As described above, in refining molten metal, it is essential to control the generated SiO2 in order to effectively perform the refining.

In the oxygen steelmaking process, which uses hot metal as the main raw material, all processes are performed in batch operations, so it is difficult to adjust Si in advance in the same furnace, and in reality, double slag blowing is We have no choice but to take operations that pose many problems, such as:

However, in the process of continuously refining molten metal, S
The amount of i can be easily controlled.

Although various types of continuous refining equipment are known, none of these has yet met the fundamentals of rational refining, which is the aim of the present invention.

The present invention relates to equipment for rationally proceeding with these methods of continuously refining molten metal.

That is, in a device that continuously refines molten metal,
It has the function of adjusting Si under conditions for the purpose of only removing Si before the step of removing P, and has an independent reaction chamber separated from other reaction chambers by a partition wall in the same reaction tank. It is characterized by

The term "reaction tank" as used herein refers to reaction equipment constructed within a single steel shell.

Reducing only Si in advance is known as a method of removing Si in a mixer furnace such as an active mixer, but this method is combined with a continuous refining device to remove Si in a batch method. is not a good idea.

In order to perform only continuous removal of Si, it is possible to provide a separate reaction tank for removing Si from a reaction tank for refining such as P removal, but this method is undesirable due to the following points.

(1) The reaction rate for Si removal is rate-limited by oxygen supply, and the oxygen efficiency is high, so unlike the case for P removal, the reaction chamber can be designed to be small, and installing an independent reaction tank is It's not a good idea.

(2) If the reaction tanks are installed separately, there is an increased chance of the molten metal being cooled as it comes into contact with the atmosphere or touching a refractory gutter as it moves between the two tanks, from the standpoint of thermal energy conservation. Undesirably, if a desiliconization chamber is provided in one tank, the molten metal simply passes under the partition wall, and there is no opportunity for heat loss.

(3) Providing a separate reaction tank is undesirable because it not only increases equipment costs but also increases the number of maintenance points and workload.

This method of dividing the inside of the reaction tank, creating a reaction chamber exclusively for removing Si, and connecting this to other reaction chambers at the bottom of the partition wall has many advantages over the method of connecting reaction tanks. We have invented a furnace structure that maximizes these advantages.

That is, the present invention provides an apparatus for continuously refining molten metal, which is adjacent to the upstream side of the molten metal flow in a reaction chamber mainly used for refining such as deP removal and deS, and is partitioned by a partition wall, and both chambers are connected at the bottom of the partition wall. It is characterized by the provision of a reaction chamber exclusively for Si removal, which is connected to only the molten metal of 1 and is located under the same furnace outer shell as one reaction chamber.

To explain in detail, a trench furnace (
A furnace in which the cross-sectional shape perpendicular to the longitudinal direction of the bath resembles a square or rectangle, and the length of the bath is more than twice that of the bath.
Take for example.

An example of a trench type furnace provided with a dedicated chamber for removing Si according to the present invention is shown in FIG. 1.

A refractory partition wall 3 is provided perpendicularly to the flow direction of the molten metal in the trench type furnace, and its bottom is separated from the furnace bottom 5. Although it is connected to the reaction chamber 2 under the partition wall, the slag on the bath is isolated by the partition wall.

The bath in the desiliconization chamber 1 does not have to be the same as the bath in the dephosphorization reaction chamber 2, and it is often a good idea to make the desiliconization chamber wider in order to ensure residence time in the same chamber. 1 side wall 4
reference).

Furthermore, when the amount of Si removed in the Si removal chamber is large, the temperature of the hot metal in the same chamber increases significantly, and it is necessary to cool the bath by putting pieces of material such as scrap into the same chamber.

In some cases, it may be necessary to make the bath depth larger than that of the deP reaction chamber (for example, to reduce the impact on hearth refractories) when pieces are introduced into the same chamber. (e.g., when the unit weight of the bath is large), in this case it is a good idea to make the bath depth as deep as 5b, and generally it is a good idea to ensure a bath depth of 50 cIfL or more.

The upper side wall of the molten metal bath surface 7 of the Si removal chamber 1 is provided with one or more slag exhaust holes 8 that communicate with outside air for the purpose of removing slag, and the ceiling 6 of the Si removal chamber 1 is provided with one or more slag exhaust holes 8 communicating with outside air for the purpose of exhausting slag. Holes 9 and 10 are provided at arbitrary locations on the side walls and bottom of the furnace for the purpose of charging coolant such as auxiliary materials and scrap and blowing oxygen for removing Si.
One or more are provided.

The size of the Si removal chamber is determined by the amount of Si to be removed and the amount of molten metal to be processed.

The amount of Si to be removed is determined by the difference between the charged molten metal Si content (%) and the amount of Si required in the dephosphorization reaction chamber. 0 as mentioned above
．． Generally, it is 5% or less.

According to the findings of the present inventors, it is appropriate that the residence time of the molten metal in the Si removal chamber is 0.5 to 3.5 minutes per 0.1% of the amount of Si removed.

If the time is shorter than the above, the amount of oxygen supplied (per unit time) must be increased, and as a result, metal adhesion becomes severe, making stable operation difficult. The length of the Si chamber must be increased, which is undesirable from the viewpoint of equipment cost and refractory unit consumption.

Furthermore, if the residence time is increased, the Si removal chamber becomes larger, which is undesirable from the viewpoint of equipment cost and refractory unit consumption, as described above.

Since the purpose of Si removal in the Si removal chamber is only to remove Si, it is desirable to use as simple operating conditions as possible;
Slag produced only with 5i02 and FeO without the addition of 5i02 and FeO has high viscosity and causes problems such as difficulty in slag removal and maximum content of 2 grains of iron. Therefore, it is necessary to add quicklime to reduce the slag viscosity, and the amount of Slag basicity (CaO)
7 (sio2) 0.7 to 1.0 may be determined as a target.

Examples of the method of the present invention will be described.

Molten metals targeted by the method of the present invention include a wide range of metals such as pig iron for molten steel production, molten iron, and molten alloy iron.
As an example, an example will be explained in which pig iron for molten steel manufacturing is targeted.

A dephosphorization reaction chamber and a partition wall (J
A preliminary membrane chamber with primary dimensions was provided adjacent to each other.

Hot metal is continuously charged from the charging hole 11, refined in the desiliconization chamber 1 and the dephosphorization reaction chamber 2, and continuously discharged from the tap hole 14.

The Si-removal chamber 1 and the P-removal reaction chamber 2 are adjacent to each other with a partition wall 3 in between, and the hot metal flows under the partition wall, and only the slag is isolated.

Furthermore, the bath depth 5 and bath width 4 are larger than those of the P removal reaction chamber on the premise that pieces of material such as scraps are to be input into the Si removal chamber.

The ceiling 6 of the furnace body has a lance hole 9 for supplying 02 for bath oxidation, and a charging hole 10 for charging auxiliary material (CaO), piece material, etc. A slag discharge hole 8 for the Si removal chamber is provided.

In addition, 12 is a lance hole of the deP reaction chamber 2, 13 is an auxiliary material charging hole, 14 is a metal discharge hole after refining, 15 is a partition wall,
11 exhaust stack.

The cross-sectional shape of the bath in the deP reaction chamber is 50 cm wide and 25 cm deep.
cIfL, the Si-free chamber was constructed with the following dimensions.

Oxygen width for Si removal: 0 GIrL Depth: 0 cm Length: 200 crrL Hot metal was supplied to the Si removal chamber at a rate of 50 T/hr, and Si was removed under the following conditions.

(Residence time: 5 minutes) Quicklime consumption rate: 5 kg/T Hot metal acid feeding rate: 300 Nm”/hr The above treatment can reduce [%Si] from 0.61 to 0.29, and the bath temperature is 153°C. showed an increase in

(Without charging of scrap as a coolant) The above-mentioned Si removal
The process was carried out continuously in a ladle-shaped furnace (diameter 3 m, depth 2 m) independent of the deP reaction chamber, and deSi was removed under the same conditions as above.
This was also supplied to the deP reaction chamber using a refractory gutter.

The bath temperature increased by only 130°C with the same amount of Si removed as above, and it became clear that there was a bath temperature loss of 23°C (corresponding to about 15 degrees Celsius) during transportation, demonstrating the advantages of the present invention. It became clear.

[Brief explanation of drawings]

Figures 1a and 1b show the shape of the desiliconization chamber in the refining furnace of the present invention, where a is a plan sectional view and b is a front sectional view. Figure 2 a, l) shows a specific example of the refining furnace of the present invention, and a (
''A side sectional view, b is a plan sectional view. 1...Desiliconization chamber, 2...Dephosphorization reaction chamber, 3...Partition wall, 4...Side wall of desiliconization chamber, 5... ... Desilicating chamber hearth bottom, 6 ... furnace ceiling, 7 ... bath surface, 8 ... slag drainage hole. 9...Lance hole (Si removal chamber), 10...
...Auxiliary material, scrap charging hole, 11...Hot metal charging hole, 12...Lance hole (DeP reaction chamber)
, 13...Auxiliary material charging hole (DeP reaction chamber), 14
...Metal discharge hole after refining, 15...
Partition wall, 16...Exhaust pipe.

Claims (1)

[Claims] 1. A furnace for continuously refining molten metal, characterized by having a desiliconization chamber exclusively for desiliconization reaction adjacent to the molten metal flow through a partition wall on the upstream side of the molten metal flow of the reaction chamber for refining such as dephosphorization. A continuous smelting furnace with a reaction chamber dedicated to desiliconization.