JPS62202010A - Spout refining method - Google Patents

Abstract

PURPOSE:To efficiency execute >=2 kinds of preliminary refining by blasting refining agents onto the bare surface of a molten iron and blasting the next preliminary refining agents before said refining agents float on the molten iron in the case of subjecting the molten iron to >=2 kinds of preliminary refining in blast furnace spout. CONSTITUTION:The molten iron 3 tapped from a tap hole 1a of the blast furnace 1 is poured through the blast furnace spout 4 into a torpedo 2. The molten iron 3 is subjected to preliminary refining such as desiliconizing, dephosphorizing and desulfurizing during the flow down in the blast furnace spout 6a. Blast furnace slag is discharged from a slag discharge port 4. The refining agents respectively having different properties are blasted from 3 pieces of nozzles 7a, 7b, 7c onto the bare surface of the molten iron flowing down by passing the underside of a skimmer 5a and are thoroughly penetrated into the molten iron, by which the preliminary refining is effectively executed. The 2nd refining agents of the different kind are blasted into the molten iron before the 1st refining agents blown thereto float on the surface of the molten iron. The refining agent or gas may be blasted from the final nozzle 7c. The refining agents mix thoroughly with the molten iron and >=2 kinds of the preliminary refining are efficiently executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a gutter refining method in which a refining agent is added to hot metal flowing in a gutter.

[Conventional technology]

Continuous refining methods, in which hot metal is allowed to flow down continuously and a refining agent is added to the flow path to remove impurities, have come to be used particularly in blast furnace gutters.

As a method of adding this refining agent, the overlay method was often used in the early days. In this top placing method, the hot metal and refining agent are not mixed immediately after addition, but mixing and refining is performed for the first time when the hot metal falls from the gutter into a container such as a pig iron mixing car. Perhaps for this reason, it has been often used only for single refining, but 1
In order to perform two or more refining processes in one channel with high reaction efficiency,
This method is no longer practical because it requires measures such as providing multiple falling sections or providing a stirring device.

After this, an injection method using a submerged lance was adopted on a trial basis, but although it had excellent refining efficiency, the lance was subject to wear and tear due to the influence of the flow of hot metal and the relatively long refining time, resulting in high costs. There was a problem that it didn't cover my face.

Instead, a blasting method was proposed in JP-A-58-130208, etc., in which a refining agent is blown into the hot metal using high-speed airflow while the lance (nozzle) is positioned above the hot metal. It came to be used in various refining processes. However, since the blasting method also blows high-speed airflow from the top, there is a problem that there is a lot of splashing of hot metal, and that the blowing amount cannot be controlled with just one nozzle.

For this reason, when adding a large amount of refining agent, JP-A-60-1
As seen in Japanese Patent No. 84611, it has been proposed to arrange nozzles in multiple stages relative to the flow of hot metal.

[Problem that the invention seeks to solve]

However, in the above proposal, the slag generated in the previous stage is blown into the next stage, reducing the amount of refining agent that penetrates into the hot metal.
There was a problem that the refining reaction decreased.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a gutter refining method that solves the above problems and improves the reaction efficiency of a refining agent in continuous refining.

[Failure to solve the problem]

In order to achieve the above object, the present invention has a gutter refining method in which a refining agent is added to the hot metal flowing in the gutter, and when blasting is performed sequentially in the flow direction of the hot metal, the blasting entry part is always kept at the bare surface of the hot metal. The method is characterized in that the refining agent is blasted to promote its penetration into the hot metal, and before the refining agent floats above the hot metal, it is blasted again to allow the refining agent to penetrate into the hot metal again.

In the gutter refining method described above, a different refining agent can be used for the blasting in the later stage than in the blasting in the earlier stage,
Further, only gas can be used for blasting in the latter stage.

[Effect]

When blowing nozzles are installed in multiple stages in the hot metal flow direction, the slag generated by blowing in the previous stage floats up and covers the surface of the hot metal, increasing the slag layer thickness and absorbing much of the infiltration energy of the refining agent blown in the next stage. It is consumed in removing the slag layer, making it impossible to obtain the desired penetration depth.

If the penetration depth is shallow, the reaction time and stirring power will be reduced, resulting in a reduction in the efficiency of the refining reaction.

Therefore, by adjusting the nozzle interval and performing the next blowing just before the refining agent injected in the first stage floats up as slag, the permeability of the refining agent will be improved, and the refining agent blown in the first stage will again flow into the hot metal. The unreacted parts get a chance to react again, and the reaction progresses.

Furthermore, the slag that is about to float and the refining agent that is injected are mixed together in the hot metal in a complicated manner, and the stirring action becomes active, further progressing the refining reaction.

〔Example〕

Examples will be described below with reference to the drawings.

The equipment used to carry out the present invention is constructed as shown in FIG. To explain this equipment, a blast furnace trough 4 is installed in the blast furnace 1 to guide hot metal 3 from the tap hole 1a to the torpedo 2. Preliminary refining is performed in the blast furnace gutter 4, and for this purpose, first and second skimmers 5a, 5 are installed on the upstream and downstream sides at a certain interval.
A blast furnace slag discharge port 6a is provided immediately upstream of the first skinmer 5a, and a slag discharge port 6b is provided immediately upstream of the second skinmer 5b. Between the skinmers 6 av 6 b, a group of nozzles for blasting the refining agent is arranged in two stages 7 a and 7 b, and each stage 7 a p
7b is composed of three nozzles 7...

Each nozzle 7... is arranged approximately at right angles to the flow of hot metal. It is also possible to further increase the number of steps to form a three-pronged structure of 7a, 7b, and 7c, as shown in FIGS. 2(a) and 2(b).

(Just &) is a conventional example. ) Each stage 7a+7b+7
Although not shown, the distance Zl + t2 of c can be adjusted by a suitable moving device. A tank 8 for feeding a refining agent is connected to each nozzle 7.... In the figure, the same tank 8 is connected to each stage 7 a p 7 b, but when blasting different refining agents in the former stage 7 a and the latter stage 7 b, another tank may be connected to the latter stage 7 b. can. In addition, when blasting gas only to the latter stages 7b and 7c, use the valve 8a to
cut off.

Further, a load cell 10 is installed under the rail 9 on which the torpedo 2 runs. This load cell 10 is originally intended for measuring the amount of hot metal, but in the present invention it is also used to measure the flow rate of hot metal flowing in the blast furnace gutter 4.

By the way, in the present invention, the nozzle interval L 1 p t2 is adjusted and the distance shown in FIG. As shown in (b), before the refining agent floats on top of the hot metal, it is blasted again (either with the gas alone or together with the refining agent) to allow the refining agent to penetrate into the hot metal again. However, in order to implement this, it is necessary to know the floating position of the refining agent. The easiest way to determine the floating position is by visual judgment, but it can also be determined by experiment or calculation. The floating position is generally determined by the nozzle angle θ and the blasting flow rate V1.
, mass of refining agent ml, hot metal flow rate V2) viscosity coefficient μ of hot metal
, and the mass of hot metal m2. Hence these parameters. By deriving an experimental formula that is a function of , the floating position can be determined by calculation even if each parameter changes.

The nozzle position 7c can be placed in front of the floating position of the refining agent. Also, among the /J parameters, the most variable is the hot metal flow rate 1 and 2, so a map centered on this v2 is formed, and the nozzles 7 and 7 of the next stage 7b and 7c are immediately followed by changes in the flow rate v2. It is also possible to move...

Next, to explain a specific example, hot metal was desiliconized in a blast furnace gutter using the above-mentioned equipment. As shown in Figure 3, the blowing angle of nozzle 7 was slightly tilted downstream, the angle between the nozzle axis and the hot metal surface was 85°, and the hot metal flow rate was determined using the above-mentioned load meter. I measured it. The refining reaction efficiency was then measured by changing the nozzle interval at regular intervals while adjusting the blowing amount to a constant rate based on the hot metal flow rate.

The refining reaction efficiency η is expressed by the following formula.

However, A: coefficient (ratio of St and 02).

As a result, the graph shown in FIG. 4 was obtained. As can be seen from this graph, there is a position C that has the maximum efficiency at the midpoint between the calculated deepest position A and the floating part position B, and if the nozzle spacing t1 is set to oC, the maximum efficiency can be obtained. It has been demonstrated that it is sufficient to perform blasting again before the refining agent floats on top of the hot metal. The distance between nozzles @t1 is the above i
If the four parameters change, the quality will naturally deteriorate, so it is desirable to change them according to those conditions. The purpose can also be achieved by changing the floating position of the slug. The simplest method is to change the nozzle angle θ of the front stage 7a. However, if you change it too much, the penetration depth will become insufficient, or conversely, the refining agent will reach the bottom, promoting erosion of the bottom of the gutter, so you need to be careful.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

■ Reaction efficiency can be improved by multi-stage blasting.

■ The number of nozzles can be expected to increase due to the use of multi-stage nozzles.
Moreover, since each nozzle can be made into a small volume nozzle,
It is possible to reduce hot metal sglache.

■ The multi-stage nozzle makes it possible to inject a large amount of refining agent, increasing the amount of impurities removed in the gutter. Accordingly, the end point impurity concentration can be reduced.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the equipment used to carry out the present invention;
Figures (a) and (b) are explanatory diagrams showing the relationship between blasting and slag flow; (,) are conventional examples; (b) are the present invention; Figure 3 is an explanatory diagram showing the nozzle angle; Figure 4 is a graph showing the relationship between nozzle spacing and refining efficiency. 3... Hot metal, 4... Blast furnace gutter, 7... Nozzle, 7a
...Nozzle front stage, 7b... Nozzle next stage, 7C...
Nozzle final stage, 8...Tank, tl+t2...Distance between nozzles.

Claims (3)

[Claims] (1) In the gutter refining method in which a refining agent is added to the hot metal flowing in the gutter, when blasting is performed sequentially in the flow direction of the hot metal,
The refining agent is always blasted to keep the blasting penetration area at the bare surface of the hot metal, promoting penetration into the hot metal,
A gutter refining method characterized by blasting the refining agent again before it floats above the hot metal to allow the refining agent to enter the hot metal again. (2) The gutter refining method according to claim 1, characterized in that a different refining agent is used in the latter stage blasting than in the earlier stage blasting. (3) The gutter refining method according to claim 1, characterized in that only gas is used for the blasting in the latter stage.