JPH01127614A - Method for heating molten metal - Google Patents

Abstract

PURPOSE:To effectively utilize energy of the coke by combined blowing oxygen into molten metal having floated slag and also directly supplying the oxygen from tuyere at the side part to lump coke added in the slag. CONSTITUTION:To the molten iron 3 having the floated slag 4 charged in furnace body 1 of a converter and oxygen is supplied from a top blow lance 6 and bottom blow tuyeres 2 arranged at the upper part and the lower part of the furnace body 1. Successively, auxiliary raw material of chromium ore, coke, etc., is charged from chuter 7 above the furnace and the oxygen is directly supplied into the slag 4 from one pair of side blow tuyeres 8 arranged at the belly part to the floated slag 4 having the lump coke. Then, the side blow tuyere 8 is set at lower part than the lower end of the top blow lance 6 and upper part than the iron bath surface under standing up straight and during progressing the blowing, and constituted with double tubes, in which oxygen from the inner tube 9 and cooling gas from gap 10 between the inner tube 9 and the outer tube are injected. By this method, the energy of the coke is effectively utilized and the molten metal is effectively heated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for heating molten metal, in particular, by effectively utilizing the heat of oxidation reaction of carbon in the molten metal and lump coke added to slag. , which attempts to effectively heat molten metal.

(Prior art) A large amount of scrap iron is melted in a steelmaking furnace, such as a converter,
Alternatively, when ore raw materials such as iron ore, manganese ore, and chromium ore are added into a converter and the metals in the ore raw materials are recovered by reducing the ore, a large amount of energy is required. As such an energy source, it is common to use a carbon-containing substance, especially coal or coke, and use the heat of the oxidation reaction to compensate for the lack of heat. For example, Tokuko Sho 5
Publication No. 6-8085 describes a method for increasing the amount of scrap iron charged by using a pure oxygen bottom blowing converter equipped with an oxygen top blower at a position higher than the bath surface, and using especially coke breeze as an energy source. is introduced into molten iron through a bottom blowing tuyere protected by hydrocarbons. In this method, since the coke is in powder form and is introduced from below the bath surface, most of the carbon in the coke dissolves into the molten iron relatively instantaneously, resulting in C = C-11000 (cal/g- mol
) - (1) The endothermic reaction occurs, and in addition to this, since the proportion of coke breeze suspended in the slag is small, the reaction C+-T between the oxygen gas supplied from the bottom blowing tuyere and the carbon in the molten iron occurs. O□=CO+32740 (cal/
g-mol) By the strong stirring of the molten iron and slag by the CO gas generated by (2), a part of the suspended coke powder is also dissolved into the molten iron.

Furthermore, the CO gas generated by the reaction of equation (2) above the bath surface is combined with the oxygen gas supplied from the top-blown oxygen device installed above the bath surface at a rate of CO+ Ox = coz+61750 (cal/g
-mol) (3) An exothermic reaction proceeds. Furthermore, the residue of the suspended coke undergoes a direct reaction with oxygen gas blown from above the bath, C+Oz =CO! +94052 (cal/g-m
ol) −(4). Here, above (
3), Most of the CO□Ox generated by the reaction of equations (4) is entrained in the top-blown oxygen stream from above the bath and collides with the iron bath, changing CO1+C→2CO-29010 (cal
/g−n+ol) (5) This causes an endothermic reaction.

The energy needed to heat and melt scrap metal is (1) to (5)
It is given by the sum of the reactions in equation (4), but the problem here is that the proportion of the reaction in equation (4), which has a high calorific value but also a large amount of heat transfer, is due to the suspended coke powder in the slag. Because it is a small amount, it is small overall, and in addition (3), (
Since the CO□Ox generated in the reaction of formula 4) has a high possibility of causing the endothermic reaction of formula (5) because the top-blown oxygen flow is from top to bottom, the energy of coke breeze is effectively used to react with molten iron. This means that it cannot be used for heating.

Tetsu-to-Hagane 71 (1985) 5928 also states that when smelting and reducing chromium ore, a top-bottom blowing converter is used to supply nitrogen gas through the bottom tuyere or the side-blowing tuyere attached to the belly of the furnace. The lump coke that is introduced into the molten metal or slag and suspended on the slag is oxidized by oxygen gas supplied from the top blowing lance, and the heat of this oxidation reaction is used for the endothermic heat generated during the reduction of chromium oxide. A method is disclosed.

In this method, the molten metal is heated by the soft-blown top-blown oxygen colliding with the lump coke on the slag, and the lump coke and slag heated by the heat of the oxidation reaction being heated by side-blown or bottom-blown nitrogen gas. mixed in slag,
Furthermore, it is carried out by contact with molten metal.

In order to efficiently melt and reduce chromium ore,
In addition to increasing the heat supply capacity mentioned above, it is necessary to increase the reduction reaction rate, and specific measures include increasing the temperature and [%C] of the molten metal to 1600°C or higher and 3%
It is well known that it is effective to stir and mix slag and metal while maintaining the above-mentioned temperature.

The problem here is that in order to efficiently reduce the chromium ore, the gas supplied from the side-blowing or bottom-blowing tuyere is nitrogen gas (oxygen gas may also be blown from the side-blowing tuyere). . In other words, it is desirable to increase the amount of gas in order to perform more powerful stirring and mixing of slag and metal and improve the reduction recovery rate and reduction rate of chromium oxide in chromium ore, but it is desirable to increase the amount of nitrogen gas. This increase has a thermal and disadvantageous effect on reduction due to cooling of the slag and metal by nitrogen gas, and as a result, a significant improvement in the reduction rate of chromium ore cannot be expected.

In this regard, the inventors previously proposed a method for heating molten iron as described below in Japanese Unexamined Patent Publication No. 84311/1983.

In other words, when the oxygen gas supplied from the tuyere installed at the bottom of the converter furnace floats through the molten iron, it reacts with the carbon gas generated by the reaction.
The slag formed by O gas is subjected to secondary combustion (CO gas is
By blowing oxygen into the slag from the oxygen tuyere (oxidized to O□Ox), the CO generated in the molten iron is oxidized to CO□, and the reaction heat is stored in the slag. This stored heat is transferred to the molten iron side while the slag and metal are strongly stirred by oxygen gas supplied from the bottom blowing tuyere. In this method, a large amount of heat is transferred to the molten iron using the slag as a medium, so the generated CO2 does not undergo an endothermic reaction in which it becomes CO again according to equation (5), and the molten iron can be heated efficiently. .

(Problems to be Solved by the Invention) This invention relates to an improvement of the above-mentioned heating method, by adding lump coke to the slag and efficiently utilizing the energy of the added coke to heat molten metal. It is an object of the present invention to propose a technique for advantageously heating and thus achieving a high-volume use of scrap iron in a converter and, in particular, a high-efficiency smelting reduction of ore raw materials.

(Means for Solving the Problems) That is, the present invention blows oxygen from above and below from the top and bottom of the reaction vessel to the molten metal containing floating slag stored in the reaction vessel, and at the same time blows the floating slag This method of heating molten metal consists of adding lump coke to the slag and supplying oxygen directly into the slag from a tuyere provided in the belly of the reaction vessel.

In this invention, a pure oxygen bottom-blown converter or a top-bottom blowing converter capable of bottom-blowing pure oxygen is particularly advantageously suitable as the reaction vessel.

The use of a converter as described above as a reaction vessel means that the heat of the coke and slag heated by the oxygen supplied from the side-blown tuyere is transferred to the molten metal by powerful bottom-blown gas stirring; Since the bottom blowing gas is oxygen, it is effective in the sense that the heat generated by the further reaction of the CO gas produced by the reaction with the carbon content in the molten metal with the oxygen gas supplied from the side blowing tuyeres can be utilized.

In addition, in the method of bottom-blowing inert gas, if an amount sufficient to strongly stir the bath is blown in, not only does the cost of the inert gas increase, but also thermal loss occurs due to the cooling effect of the inert gas. That is, in order to obtain a stirring effect equivalent to the method of blowing oxygen, it is necessary to blow in an inert gas twice the volume of oxygen as shown in the following equation.

o! +2C-→2C0 2N2→2Nt Furthermore, since CO gas is not generated in the bath, the secondary combustion effect due to the horizontal blowing tuyeres is also inferior.

Furthermore, if the flow rate of the bottom blowing gas is set to 0.5 Nm"/sin or more per ton of molten steel, it will not only improve the stirring effect of the bath, but also achieve excellent secondary combustion due to the oxygen gas from the side blowing tuyeres. It has become clear that this method is effective.

(Example) Example 1 An example of the present invention, which was carried out using a top-bottom blowing converter having a furnace capacity of 5 tons as shown in FIG. 1, is shown below. In the figure, number 1 is the converter body, 2 is the bottom blowing tuyere, 3 is molten iron, 4 is slag, 5 is lump coke, 6 is top blowing lance, and 7 is for charging auxiliary materials such as chromium ore and coke. 8 is an over-furnace shooter, and 8 is a tuyere for introducing oxygen gas to combust the lump coke 5 in the slag and CO gas generated by the oxygen gas supplied from the bottom blowing tuyere 2 in the slag. .

The horizontal blowing tuyeres 8 immersed in the slag 4 are arranged in sets of two facing each other at a position where they will not be immersed below the surface of the molten metal even if the furnace body 1 is tilted during charging of molten iron or tapping of molten steel. The direction is determined so that the central axes of the oxygen streams collide in the space of the converter body 1.

If this installation procedure is not adopted, the coke in the slag 4 will not be sufficiently burned, and if the side blowing tuyere 8 is not immersed in the slag, the heating and stirring of the slag will be insufficient, resulting in a decrease in the heating ability of the molten metal. Instead, there is a high risk that the oxygen gas flow will directly collide with the opposing furnace wall and cause significant erosion of the furnace wall refractories.

On the other hand, the installation height of the side blowing tuyere 8 must be below the lower end of the top blowing lance 6 and above the surface of the iron bath when the converter is in an upright state and blowing is in progress.

However, since it varies depending on the shape of the converter body 1, the internal volume of the refractory bricks, the lower limit of the lance height, etc., it cannot be determined in general and must be determined for each converter.

In addition, the horizontal blowing tuyere 8 is a so-called double pipe tuyere and its inner pipe 9
Oxygen or oxygen-containing gas is passed through the gap 1 between the inner tube and outer tube.
It is desirable that the cooling gas for protecting the tuyeres be ejected from zero.

Now, the operation was performed according to the following steps.

First, the inside of the converter 1 was sufficiently preheated with coke oven gas, and then 5 tons of hot metal was charged. The hot metal temperature was 1264°C. Next, after standing the furnace upright, the inner pipes of the four bottom tuyeres and the four side blowing tuyeres were each rated at 5.0 Nm'/l1i.
Oxygen gas of 0.3 Nm and 37 ml of propane gas for protecting the tuyere were supplied from the outer tube. At the same time, the top-blowing lance 6 was lowered from above the furnace, fixed at a position where the distance between the stationary scene and the tip of the lance was 0.7 m, and oxygen gas was supplied at a rate of 12.5 Nm''/win. 150 kg of CaO powder from bottom tuyere 2,
500 kg of lump coke was added and the temperature of the molten iron was 155.
Blowing was performed for about 7 minutes until the temperature reached 0°C.

The temperature of the molten iron was checked from above the furnace using a sublance.

The temperature and ingredients at this time are shown in Table 1.

Next, 28 kg of lump coke was released from the shooter above the furnace.
The agglomerated chromium ore was added at a rate of ... in so that the temperature of the molten iron remained constant. In addition, CaO powder was blown into the slag from the bottom blowing tuyere so that the basicity of the slag was 1.5. The compositions of the lump coke and chromium ore used are shown in Table 2.3.

The blowing was completed when the amount of chromium ore added reached LOOOKG. The operational results at this time are shown in Table 4.

As is clear from Table 4, 95% of the chromium content in the supplied chromium ore was recovered into the metal. Of the remaining chromium content, 1.0% remains in the slag, and 4% is the amount that escapes to the outside of the furnace due to dust and spitting.

Example 2 The same equipment and operating method as in Example 1 were followed, but since powdered chromium ore was used in this example, a special top blowing lance as shown in Figure 2 was used, and from the center of the top blowing lance Chromium ore powder is introduced into the furnace using nitrogen gas as a carrier gas,
In addition, oxygen gas is supplied from the outer tube at a rate of 12.5 Nm'/mi.
The operation was carried out by spraying at a ratio of n. The operation results at this time are shown in Table 5.

Table 5 According to this method, the chromium ore powder passes through a high-temperature oxygen stream and is preheated before entering the molten iron, making it possible to further reduce operating time and various basic units.

Furthermore, by improving the addition yield of chromium ore powder, the reduction recovery rate further increased to 96%.

Comparative Example The same equipment and operating method as in Example 2 were followed, except that nitrogen gas was supplied from the bottom blowing tuyere at a rate of 1.0 Nm3/min, and oxygen gas was supplied from the side blowing tuyere at a rate of 5.0 Nm37m.
1n, oxygen gas from the top blowing lance at 17.5Nm3/
The operation was carried out by supplying min. min and chromium ore powder. The operation results at this time are shown in Table 6.

Table 6 As is clear from a comparison of the operation results in Tables 5 and 6, in order to melt and reduce 1000 kg of chromium ore powder, the conventional method uses nitrogen as the bottom blowing gas, so the energy of the coke is used. It cannot be used effectively, and as a result, the operating time is extended, which means that various basic units are increased, which is not economical. Furthermore, in the conventional method, the reduction recovery rate was as low as 91%, partly due to the lack of bottom-blowing gas stirring.

On the other hand, in the method of this invention, the energy possessed by coke can be used effectively, and the operating time can be shortened, and further, various basic units can be reduced and a high chromium reduction recovery rate can be obtained.

(Effects of the Invention) According to the invention, molten metal can be effectively heated by effectively utilizing the energy of coke, and the consumption of coke and refining gas can be significantly reduced. Instead, the chromium content in chromium ore can be reduced and recovered into metal at a high yield.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a reaction vessel suitable for carrying out the present invention, and Fig. 2 is a diagram showing the nozzle structure at the lance tip of a special top blowing lance that has the function of blowing powdered ore. . 1... Converter furnace body 2... Bottom blowing tuyere 3...
Molten iron 4...Slag 5...Lump coke 6...Top blow lance 7...Furnace shooter 8
...Horizontal blowing tuyere 9...Horizontal blowing tuyere oxygen supply nozzle 10...Horizontal blowing tuyere coolant gas inlet 11...Powder flow path 12...Oxygen gas flow path 13...
Nozzle 14...Cooling water flow path patent applicant
Kawasaki Steel Co., Ltd. Figure 1 Figure 2 An, Engineering, A.A-A'4 View

Claims (1)

[Claims] 1. Oxygen is blown from above and below the molten metal with floating slag stored in the reaction vessel from the top and bottom of the reaction vessel, and lump coke is added to the floating slag, A method for heating molten metal, characterized by supplying oxygen directly into the slag from a tuyere provided in the slag.