JPS61194106A - Combustion method of gaseous co in furnace - Google Patents

Abstract

PURPOSE:To improve the combustion efficiency of gaseous CO by blowing a gaseous O2 jet out of the tuyere provided to the barrel of a converter under specific conditions and burning the gaseous CO generated by the decarburization reaction of a molten iron or molten steel. CONSTITUTION:The gaseous O2 jet is blown out of the tuyere provided to the barrel of the converter and the gaseous CO generated by the decarburization reaction of the molten iron or molten steel is burned. The blowing of the gaseous O2 jet is executed between the top end of a top blowing lance and the bath surface or within the height of twice the bath depth from the bath surface. The gaseous O2 jet is blown toward the furnace center at the section of the furnace barrel or toward the circumferential direction of the concentrical circle at the furnace center and at the angle within + or -45 deg. from the horizontal direction. The gaseous O2 jet is thus blown in such a manner that the horizontal sectional area of the blown gaseous O2 jet within the horizontal position occupies >=25% of the sectional area of the furnace barrel.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention aims to burn CO gas generated by the decarburization reaction of hot metal or molten steel in a converter by injecting it with an 02 gas jet through a lining provided in the furnace belly. It concerns how to do so.

(Prior art) Conventionally, it is said that the maximum amount of scrap that can be used during iV1 production using a converter is 20-30% (by weight) of 4 pieces per batch, and if a larger amount of scrap is charged This is the heat of oxidation combustion of Si and C during cleaning.
J is insufficient to reach the required high temperature (7),
It is necessary to provide a new external heat source. Furthermore, not only when increasing the amount of scrap as described above, but also when hot metal whose P and Si content has been significantly reduced through sufficient hot metal pretreatment is processed in a converter, Si, which serves as a heat source, is reduced. The temperature of hot metal is also decreasing, and the situation of lack of heat sources is similar.

Nowadays, as the proportion of scrap used is increasing and hot metal pretreatment is becoming widespread, the problem of converter heat sources is becoming more and more important.

Furthermore, instead of scrap, we use the five yuan forces in the iron bath,
Adding alloy components in ore or semi-reduced form, iron bath components, I! , and methods for performing 1-stage adjustment are also being researched, and the need for a heat source within the converter is increasing.

Conventionally, in such a converter, the heat source, that is, the heating 1
Regarding the stage, it has been proposed to combust CO gas produced by a decarburization reaction in a converter and utilize the combustion heat.

By the way, in the past, due to some serious confusion, the location where the hot water was stored changed, and it was a common practice that there was no space for oxygen and gas for combustion in the furnace. This was because the gas blow was a soft blow.

However, in recent years, by limiting the injection angle and direction, it has become possible to achieve high-speed injection. ￥; Even if the siding is located below the hot water surface, 2. A gas injection speed was achieved that did not allow molten metal to enter. In other words, the structure is similar to that of bottom blowing under the surface of the molten metal, and 02 gas is blown during secondary combustion, and at the top of the furnace and at the time of melting, a gas that does not adversely affect the molten steel is used. For example, a total of CO2.02 is injected.

Against this background, in Japanese Patent Publication No. 53-35764, when CO gas is combusted in a converter by adding 02 gas to produce CO2 gas, C0107, CO2
A method has been proposed in which the addition amount, direction, etc. of combustion gas are controlled by detecting the following.

This is a method that attempts to follow the irregularity of CO gas generated in the furnace by changing the direction and amount of 07 gas injection. However, it is extremely difficult to detect gas generated in a high-temperature furnace, making it difficult to apply to large converters, etc., and control becomes extremely complex as the number of tuyere increases, making it impractical.

Tokuko Sho 5G-9249 has zero fuel supplied from outside.
A method of heating molten steel by blowing into /8 steel or from the outside to the inside while burning with two gases is disclosed. According to this method, fuel consumption is enormous, but the CO gas in the exhaust gas (which can be used as fuel gas) is released as is, and considering the amount of heat that this CO gas has, the energy loss is quite large. Become.

(Problems to be solved by the invention) Conventionally, there have been two (11) basic structures for CO gas combustion.
In a bottom-blown converter, 02 gas is blown from one or two blades placed from the furnace shoulder or top toward the bath surface in the center of the furnace; (2) In a top-blown converter, 02 gas for decarburization is sprayed directly downward from the tip of the lance, and a separate C gas is sprayed in a more horizontal direction.
There are two methods of blowing out 02 gas for O gas combustion.

However, with such conventional methods, only 25% of CO
It is the combustion rate. In other words, with the conventional balloon method, CO
Since the number of 02 gas jets for gas combustion is small, the area covered by the 02 gas jets relative to the cross section of the furnace belly cannot be large, and the amount of CO gas that is generated that passes through the cross section of the furnace belly is covered only at about A position.

The key to CO gas combustion in a converter is to provide all of the CO gas passing through the furnace belly with ~f-yance in contact with the O, gas. For this purpose, it is preferable to blow out the 02 gas from the belly side so that the entire cross section of the belly is covered with 02 gas. Blowout from the lance can lead to damage to the furnace bricks, so i-
It's not 7 strategies. In addition, even if it is blown out from the furnace shoulder through the siding, the blown jet collides with the bath surface, so the combusted CO2 reacts with carbon on the bath surface, causing an endothermic reaction of C+CO2-2CO. This means that the ignited combustion will not be utilized effectively.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method that utilizes the tuyere provided in the converter belly to efficiently burn CO gas and does not have the above-mentioned drawbacks.

(Failure to solve the problem) As mentioned above, in the past, attempts were made to increase the burning point area of the top-blown 02 gas jet to increase the amount of CO gas burned. The subsequent CO2 gas collides with the bath surface and becomes CO2+C-2CO again, so the total amount of combustion is small and only a few degrees.

Therefore, in the present invention, ■ Area Ao covered by 02 gas di and L soto for CO gas combustion.
2 is set to be wider than the rising area Aco of CO; ■For this reason, the blowing direction of the O2 gas jet for CO gas combustion is blown out from the furnace wall side in a fan-like manner from a large number of slits or slit-like slats, and the blowing height is The height of the jet should be within a certain range above the bath surface in order to transfer the combustion heat to the hot metal or F6 steel; ■The direction of the blowout should be within ±45 degrees from the horizontal plane within the range where the jet does not collide with the bath surface of the hot metal or molten steel. The aim is to improve this by blowing from a position below the tip of the top-blowing lance within 30°.

Here, the gist of the present invention is a method for burning CO gas generated by the decarburization reaction of hot metal or molten steel by blowing out a 02 gas jet from a lining provided in the belly of a converter, The above 02 gas jet is blown between the top blowing lance tip and the bath surface, or within twice the bath depth from the bath surface, and
The blowing direction of the gas jet is directed toward the furnace center of the cross section of the furnace belly or toward the circumferential direction of a concentric circle around the furnace center, and the angle is within ±45°, preferably ±30′ from the horizontal direction, [3]
In this way, the horizontal cross-sectional area at the siding position covered by the injected 02 gas jet occupies 25% or more, preferably 40% or more of the furnace belly cross-sectional area. It is a gas combustion method.

The above-mentioned "converter" includes not only the LD converter, but also a composite converter that combines top blowing and bottom blowing, and even a bottom blow converter known as the low-Bop process.

Furthermore, there is one advantage 1. ! ! In this case, the siding is exposed to an extremely high temperature atmosphere both during combustion in the furnace and during tilting, and the siding structure is exposed to -J in order to cool the tuyeres.
The cooling gas, which causes an endothermic reaction due to thermal decomposition of hydrocarbons (CmHn), etc., is ejected from the outer tube part of the double front panel to protect the blades and prevent the decomposition inside the furnace. The structure may be such that the gas is combusted by the 0□ gas blown in from the inner tube to increase the heat transfer efficiency.Similarly, the blade structure may be a 2m slit structure.

In addition, the score is t1'! In the case of a tube, the tip may be made of a ceramic pipe to extend its life.

By the way, the oxygen jet that is blown in from the plane is usually about the size of Matsuha, and in this case, the reach distance of the jet (L
) is L-42d. However, d is the tuyere diameter. If the jetting speed is low, it is necessary to change the coefficient, but in order to prevent molten steel from entering the cuff when the converter 1 rotates, the jet speed needs to be 1 or higher.

As already mentioned, the purpose of burning CO gas in the converter is to use it as additional FA5 when the amount of scrap charged is increased, or to pre-treat hot metal to remove P and Si. This is to use it as an auxiliary heat source for hot metal.

Therefore, from one aspect, the present invention is a converter steelmaking method with excessive scrap charging accompanied by CO gas combustion, and from another aspect, the present invention is a converter steelmaking method that removes P and Si from hot metal. It is also a reduction steel manufacturing method that utilizes alloy components, etc.

(effect) The invention will be further described in connection with the accompanying drawings.

FIG. 1 is a schematic sectional view illustrating a converter structure for carrying out the method according to the present invention. According to the present invention, 07 gas dienoto is emitted from a plurality of tuyeres 11 provided in the belly of the converter 10. For example, in the case of a top-blowing converter, the blowing position is between the tip of the -L blowing lance and the bath surface. In the case of a bottom-blown converter, this is carried out in an area within twice the bath depth from the bath surface. In the case of a combined converter, the process is basically the same as in the case of a top-blown converter.

The 02 gas jet blown into such an area is blown toward the center of the furnace cross section or toward the circumferential direction of the concentric circle around the center of the furnace, so that the 02 gas jet does not directly collide with the furnace bricks. must choose a direction. This is to prevent the 02 gas Geno 1- from colliding with the bricks and promoting melting damage.

Figures 2-1(d) to 2 (dl are diagrams schematically showing the flow of gas in the converter brought about by the injection of the Ot gas jet at this time. When 02 gas jets are blown from the blade L1 toward the center of the furnace, Figure 2 (BL shows the gas flow in the furnace when slits are used as the blades. Similarly, Figure 2 (C1 shows the flow of gas in the furnace when slits are used as the blades). This shows the gas flow when the same gas is blown from.

On the other hand, FIG. 2 (dl shows the case where 02 gas jets are blown from three concentric circles in the circumferential direction.

Considering the combustion efficiency of the CO gas, a method of blowing in the circumferential direction, especially a method of blowing through a large number of holes, is preferable, and a slit-like hole is more preferable because the surface area of -F jet, and m is increased.

Next, the direction of the 02 gas jet blown from the siding is limited to within ±45° with respect to the horizontal plane, but this is not 0° to the bath surface.
This is to reduce collisions between the two gases as much as possible, and to prevent CO gas once generated from reacting with carbon in the bath again on the bath surface. Preferably, the air is blown at an angle within the range of 130° C. with respect to the horizontal plane. This is because even if Soeno I is bent by the shadow 3 of the air flow in the furnace, it will remain in the target space C.

Next, in the present invention, the horizontal cross-sectional area of the blade of the 02 jet at the position ``■'' occupies more than 25% of the area of the heart I fold.
If this is less than 25%, the furnace firing efficiency of CO gas, that is, the heat supply to the converter is insufficient, and preferably 40%.
That's all. When it exceeds 80%, almost 100% of the CO gas is burned.

Next, the present invention will be further explained by examples.

15 Ton converter (furnace inner diameter: 1.5 mm) with the structure shown in Figure 1.
Hot metal of the following composition was treated using At this time, from the 4 slit-type slats provided at equal intervals on the furnace belly and the auxiliary two city pipe-type slats provided between the slits, a circle is drawn approximately horizontally to the same circle at the center of the converter. 02 gas jet (Matsuha 1) was blown in the circumferential direction.

The size of the siding is swan 1 ~ type siding 10mm + X 10
The diameter of the auxiliary tuyere was 15 mm, and propane was blown out in an amount of 7% of each vane for cooling the tuyere.

Hot metal 1 composition (weight%) -C4 sword Si J' S-
4,50゜30 0.45 0゜105 0゜020?22 22 16 0.35 0.50 0.110
0.025 When the blowout from the tuyere was increased one by one, the gas composition at the top of the furnace was analyzed to determine the combustion efficiency of CO gas. The results were graphed in relation to the ratio of the horizontal cross-sectional area of the 02 gas jet to the total furnace belly cross-sectional area - top blowing 02 jet area.

Figure 3 (al) is a graph showing the influence of the ratio of the horizontal cross-sectional area at the 02 gas jet line position to the belly cross-sectional area on the CO gas combustion efficiency. The combustion efficiency increases, and when it exceeds 40%, the combustion efficiency also decreases to 5.
Combustion efficiency exceeding 0% and almost 100% can be obtained at 70%. This means that the CO gas combustion efficiency improves as the contact area between the CO gas and the 0° gas jet increases. In addition, Fig. 3 (bl) explains the calculation method of the horizontal cross-sectional area Δ and the area A when the blowing speed of the 02 gas jet from the round tuyere is Matsuha 1,
In the case of Surin I/Hame, the jet angle widens.

(Effects) As described above, it can be seen that according to the present invention, the combustion efficiency of the CO gas generated by the in-furnace decarburization reaction is increased, and accordingly, a sufficient amount of heat is supplied to the inside of the furnace.

Therefore, according to the present invention, it is possible to carry out multi-current charging of scrap materials, and it is also possible to perform decarburization treatment of molten pig iron without P and Si.

[Brief explanation of drawings]

Fig. 1 is a sectional view schematically showing a converter in which the present invention is implemented; Fig. 2 ta+ to Fig. 2 (di is O, gas dir-7
A schematic explanatory diagram showing the state of injection in 1.; and Fig. 3 (
al and Figure 3 (bl is a graph showing the combustion efficiency of CO gas. Applicant: Sumitomo Kinzoku Kogyo is a representative company and patent attorney: Akira Hirose - Sou, Figure 1)

Claims (1)

[Claims] [1] A method of blowing out an O_2 gas jet from a tuyere provided in the belly of a converter to burn CO gas generated by the decarburization reaction of hot metal or molten steel,
The gas jet is blown out between the tip of the top blowing lance and the bath surface, or within twice the bath depth from the bath surface, and [2] The blowing direction of the O_2 gas jet is directed toward the furnace belly. Direct the cross section toward the furnace center or toward the circumferential direction of the concentric circle around the furnace center, at an angle within ±45° from the horizontal direction, [3] In this way, the O_2 gas jet injected at the tuyere position The horizontal cross-sectional area is 25 of the furnace belly cross-sectional area.
% or more, the in-furnace CO
Gas combustion method.