JPS60243211A - Method for blowing powder from single pipe nozzle at furnace bottom - Google Patents

Abstract

PURPOSE:To blow safely powder into a refining vessel while averting penetration of a molten steel and formation of a mushroom in the stage of blowing the power into said vessel through a single pipe nozzle at the bottom thereof by controlling the flow rate of the carrier gas from the tip of a nozzle in a way as to satisfy the specific equation. CONSTITUTION:The result shown in the figure is obtd. when blowing experiment of exothermic powder is made while passing Ar as a carrier gas through the single pipe nozzle after attaching said nozzle to the bottom of the refining vessel for testing, for example, 0.5t (e.g.; converter). The blowing state of the pulverous powder stabilizes in the range where the relation of the equation holds between the flow rate V of the carrier gas and the inside diameter (d) of the single pipe nozzle as shown in the figure. The cooling effect by the carrier gass is so high that the mushroom sticks to the tip of the single pipe nozzle and blowing of the pulverous powder is not possible in the case of V<(0.1d+0.5). On the other hand, blowing of the carrier gas against the static pressure of the molten steel in the converter is not possible and the nozzle outlet is made liable to be clogged by penetration of the molten steel into the single pipe nozzle in the case of V<(0.07d+0.1).

Description

Detailed Description of the Invention The present invention relates to a method for refining by injecting exothermic powder (hereinafter simply referred to as powder) into a refining vessel from a single pipe nozzle attached to the bottom of the furnace, and details of the method for refining by injecting exothermic powder (hereinafter simply referred to as powder) into a refining vessel from a single pipe nozzle attached to the bottom of the furnace. The present invention relates to a method for safely and stably blowing powder while avoiding the formation of powder.

A technology in which hot metal is first subjected to desiliconization treatment, followed by dephosphorization and sulfurization treatment, with the aim of reducing costs by reducing the cost of auxiliary raw materials and reducing the amount of slag generated during the steelmaking stage, and also improving quality. is being put into practical use. Under these circumstances, the role of the converter has been narrowed down to decarburization and temperature increase, and through this, economical production of general steel has been achieved.

On the other hand, in fields where higher quality products are required, there are situations such as various out-of-furnace refining being refrained after converter operation, and ■ the ratio of continuous casting is increasing, so it is necessary to respond to these situations. There is a growing demand to raise the upper converter tapping temperature.

However, in the current converter operation, as mentioned above, oxidizable elements such as 81 are removed by pre-treatment of the hot metal, so the self-heating ability of the molten steel in the converter decreases, and the tapping temperature should be increased. However, there are situations where the desired temperature cannot be reached.

In order to cope with this situation, it became necessary to add some kind of heat source to the converter, and as a heat source, oxidizable substances such as Fe-8iy coke and coal were considered, and Ichika decided to implement it. There is. That is, the method for replenishing the heat source is as follows: (1) A method in which lumps of the heat source material are introduced into the molten metal from a hopper on the furnace; and (2) a method in which powder of the heat source material is introduced into the molten metal from a single tube nozzle attached to the bottom of the furnace as a carrier gas. The latter method is attracting attention because of its good thermal efficiency and reaction efficiency. However, when a single tube nozzle is used to inject powder from the furnace bottom nozzle, the tip of the nozzle is cooled by the injected carrier gas, causing an inconvenient phenomenon in which solidified iron (pine mushroom) adheres to the nozzle. It may happen. This type of pine mushroom serves to protect the nozzle when only gas is injected, but when powder is injected together with a carrier gas, the powder can clog the pine mushroom at the tip of the nozzle, preventing powder injection. It may become impossible. That is, the disadvantage of using a single tube nozzle is that the cooling effect of the nozzle tip by the gas accompanied by powder is strong, so that pine mushrooms adhere to the nozzle tip. Therefore, for example, when injecting pulverized coal, 2.
A method is being developed by Krupp and others that uses a heavy pipe nozzle to inject 02 alone from the inside and pulverized coal together with a carrier gas such as air tArtN7 from the outside. However, in the above method, not only (1) the nozzle is easily melted and damaged due to injecting Oz, but also (2) it is technically difficult to inject pulverized coal through the gap between the inner tube and the outer tube, and (3) O! There is also the risk of backfire occurring because pulverized coal and pulverized coal are injected at the same time.
This was not necessarily the preferred method.

The present invention is. This was made after repeated studies focusing on these circumstances. Even if a single pipe nozzle is used when injecting powder using an inert gas as a carrier gas, pine mushrooms will not occur at the nozzle tip and will continue. The purpose of the present invention is to provide a method that enables powder injection.

The method of the present invention, which has achieved the above object, consists of a single tube nozzle attached to the bottom of the refining vessel, in which the powder is injected by a carrier gas, and the carrier gas flow rate from the nozzle tip is set as follows. The gist of this is that it is controlled to satisfy equation (1).

(0,07d+0.1”, ≦■≦(0,1d+0.5)
(1) ■=Carrier gas flow rate (Matsuha) d: Nozzle inner diameter (M) The present invention will be explained below according to the experimental history.

First of all, the inventors attached a single tube nozzle to the bottom of a test refining vessel (a converter in the experiment), and while flowing Ar as a carrier gas, exothermic powder (pulverized coal in the experiment) was extracted. When a blowing experiment was conducted, the results shown in FIG. 1 were obtained. In the experiment, the carrier gas flow rate M and the inner diameter (d) of the single tube nozzle were used as parameters, and the stability of the blowing was evaluated. Also, the accuracy of the injected pulverized coal is 30
Below mesh = 100%, below 200 mesh is 280%, solid air ratio of pulverized coal flow is 7 to 20 kg pulverized coal AgA
It was set as r.

As shown in FIG. 1, the state of fine powder injection is stable within the range where the relationship expressed by equation (1) is established between the carrier gas flow relationship and the inner diameter (d) of the single tube nozzle. That is, V>(0,
In the case of 1d+0.5), the cooling effect by the carrier gas is so strong that pine mushrooms adhere to the tip of the single tube nozzle, making it impossible to inject pulverized coal, resulting in an orange color. On the other hand, if v〈(0゜o7d+o, tb becomes easier. In carrying out the present invention, carrier gas flow rate (7)
may be adjusted by controlling each factor shown in equation (2) below.

However, Q: Carrier gas flow rate (Nml/m) a: fI steel static pressure kg/cm" gauge pressure) 5T: Absolute temperature (0
K) A: Single tube nozzle cross-sectional area (C) ω: Sound velocity in carrier gas at 20°C (m/decrease) The basic structure of the present invention is as described above, but the powder is made of pulverized coal. Other examples include Fe, -81 powder, and coke powder. Also, as refining vessels, LD converter, LF furnace, W
AD furnace, AOD furnace, ASEA-8KF furnace, RH furnace, DI
(In addition to furnaces, ladle and mixed pig iron furnaces.

An example is a pig iron truck. Furthermore, although the method of the present invention is basically applied to blowing exothermic powder, it can also be applied to other uses. For example, if a converter is operated while injecting pulverized coal, 80% of the pulverized coal may accumulate in the molten steel, increasing the S concentration. After that, finely powdered CaO+ CaF, CaC, etc. may be injected through a single tube nozzle at the bottom of the furnace, and the present invention can also be applied to such cases.

In the present invention, the reason why the appropriate range of carrier gas flow rate changes depending on the diameter of the single tube nozzle has not been clarified, but even at the same gas flow rate, the gas jet at the outlet of the single tube nozzle changes depending on the diameter of the single tube nozzle. We believe that this is because the differential of the pine mushrooms changes, which causes a difference in the adhesion of pine mushrooms.

The present invention is constructed as described above, and stably injects powder from a single tube nozzle by controlling the carrier gas flow rate so as to satisfy the range shown in equation (1) above. can be done.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the range in which stable powder injection can be performed, and is a graph showing the relationship between the nozzle inner diameter and the carrier gas flow rate. Applicant Kobe Steel, Ltd.

Claims (1)

[Claims] In order to inject exothermic powder into the molten metal through a carrier gas (through a single pipe nozzle attached to the bottom of the furnace of a refining vessel), the flow rate of the carrier gas from the nozzle tip is determined as follows (1). ) is a powder injection method from a single tube nozzle at the bottom of the furnace, which is controlled to satisfy the following equation. (0,07d+ O: υ≦V≦(o,1d+0゜5)
-・-<s) V: Carrier gas flow rate (Matsuha) d: Nozzle inner diameter (IIIm)