JPS61291890A - Drying temperature-elevation method of vessel for molten metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for drying and heating up containers for molten metal such as pig iron mixers and ladles used in pig iron making and steel making. The object of the present invention is to provide an inexpensive drying and temperature raising method that allows extending the life of containers lined with easily oxidizable refractories such as silicon carbide or Si3N4.

[Conventional technology]

In the past, most of the drying and heating of molten metal containers was done manually. For this reason, the adjustment of the ratio of the amount of drying air to the fuel (air-fuel ratio) was dependent on the operator's control, and the amount of O2 remaining in the container was always unstable. This residual amount of 02 had a small effect on conventional containers lined with chamotte-based oxidizing refractories and did not pose much of a problem.

However, in recent years, for the purpose of producing high-quality steel, various treatments have been carried out inside the container, such as de-S, de-Si, de-P in a pig iron mixer, de-P in a ladle, etc., and the durability of the container has improved. For this reason, lining with easily oxidizable refractories such as carbon, graphite, and silicon carbide has become a frequent practice. Easily oxidizable refractories have good density, and when they come into contact with slag, they become very wet. have.

On the other hand, this easily oxidizable refractory has the disadvantage that when the temperature inside the container is high, the surface easily undergoes an oxidation reaction, becomes crumbly and peels off. As a countermeasure to this problem, the drying temperature rise is automated and combustion is performed at a constant low air-fuel ratio, that is, the air-fuel ratio is controlled by flow rate. The drying time was forced to be extended due to reduced power, insufficient stirring and circulation of the combustion gas in the container, and a longer drying time.

[Problem that the invention seeks to solve]

The present invention was invented in view of the above points, and when drying and heating easily oxidizable refractories, combustion is performed at a high air-fuel ratio at low temperatures where there is little oxidation reaction with 02 in the container. Improves the agitation and circulation of combustion gas and shortens drying time. Another object of the present invention is to provide a method for drying and heating molten metal that burns at a low air-fuel ratio at high temperatures where the influence of oxidation reactions is large.

[Means for solving problems]

In order to achieve the above objectives, the drying temperature is automatically raised according to a preset heating pattern, and the ratio is set to perform combustion at a high air-fuel ratio in the low temperature range of the heating pattern, and in the high temperature range. This objective is achieved by a method for drying and heating a container for molten metal, in which a ratio is set to perform combustion at a low air-fuel ratio, and the ratio setting is switched by measuring the temperature inside the container.

[Effect]

Next, the present invention will be explained along with its operation based on the accompanying drawings.

Figures 2 and 3 show a pig iron mixer car and a ladle drying device, respectively, in which the method of the present invention was carried out, and in Figure 2, 1 is a container for molten metal lined with a refractory material containing easily oxidizable substances. In a certain pig iron mixer car, 2.2a is a high-speed combustion burner for drying the pig iron mixer car, 3 is a rail for moving the burner back and forth, and 4 is a frame. In Figure 3, 5 is a ladle lined with a refractory material containing easily oxidizable substances, 6 is a high-speed burner for drying the ladle, 7 is a mounting equipped with a burner, and 8 is a mounting opening/closing device. It is.

FIG. 1 is an example of a control system diagram of the method of the present invention, in which a molten metal container 1 or 5 is heated to dry. 9 is burner, 10
11 is a thermocouple that detects the temperature inside the container, and 11 is a program temperature increase controller that automatically increases the temperature according to a preset temperature increase pattern, and adjusts the amount of fuel and air supplied according to the temperature increase pattern. do. 12 is an air-fuel ratio setting device for low temperatures, 13 is an air-fuel ratio setting device for high temperatures, 14 is a changeover switch, 15 is a fuel pipe, 16 is a combustion air pipe,
17 is a combustion air blower, 18 is a fuel flow rate control valve, and 19 is a fuel air flow rate control valve. In FIG. 1, two air-fuel ratio setting devices 12 and 13 are provided and switched by a changeover switch, but they can be set to one by setting a sequence.

Next, what about the operation of the method of the present invention? The following describes the case where a pig iron mixer car is dried using coke oven gas as fuel. first,
The pig iron mixer burner 2 is inserted into the pig iron mixer 1, and drying is started along a temperature rise curve determined by the programmed temperature rise controller 11. At this time, the changeover switch 14 is configured to operate the low temperature air-fuel ratio setter 12, and the ratio is set so that the air-fuel ratio R/B=1.5. The opening degree of the fuel flow control valve 18 is automatically controlled according to the combustion load during temperature rise (temperature increase program pattern). In accordance with this, the opening degree of the combustion air flow rate control valve 19 is controlled to reach the set air ratio, so that a flow rate of air-fuel ratio R/B = 1.5 times can be obtained under any combustion load. .

Next, in this state, the temperature is raised to 600°C according to a preset pattern. When the temperature measured by the thermocouple 10 exceeds 600°C, the program temperature increase controller 11
A signal is issued, the changeover switch 14 is activated, and the low temperature ratio setting device 12 is switched to the high temperature ratio setting device 13. At this time, the ratio is set so that the air-fuel ratio R/B=1.0. Accordingly, the opening degree of the combustion air valve 19 is changed so that only the minimum amount of air (R/B=lO) is always obtained. Thereafter, this state is maintained until the end of drying, and the temperature is increased according to the temperature increase pattern.

Note that the set temperature for switching the air-fuel ratio from the low temperature range to the high temperature range will be explained.

According to experiments conducted by the present inventors, as shown in Figure 4, the depth of oxidation loss increases as the oxygen concentration inside the container increases, but when the temperature inside the container exceeds 600°C, the oxidation loss suddenly increases. Become. Therefore, if the temperature is high and the O2 concentration is high, the oxidation of C in the refractory will be significant, and at around 800° C., it is necessary to perform low air combustion in the burner.

〔Example〕

Example 1 Dry heating was carried out in a pig iron mixing car.

As a container lining A text 203:63% by weight 5t02:15! Amount% SiC: 10% by weight Graphite: 10% by weight In a mixed pig iron car completely lined with bricks, the traditional method of relying on the operator's intuition (air-fuel ratio R/B = 1.5 from the start of heating to the completion) ) The relationship between the life of the pig iron mixer car and the S removal treatment ratio is shown in Figure 5.
The result was that the 0-heat life was improved.

This improvement in life corresponds to the thickness of the oxidation dissipation layer in the previous preliminary test.

Example 2 Dry heating with equipment similar to Example 1 was tested in a ladle lined with magnesia carbon (15% by weight) bricks in the slag line. As shown in Figure 6, the results are as follows:
= 1.5), the dry heating according to the present invention resulted in an improvement in life of about 10 heat at the same molten steel desulfurization treatment ratio.

〔Effect of the invention〕

By the method of the present invention, the following effects were obtained.

As shown in Example 1.2 above, the life of the container was improved compared to the conventional method relying on operator intuition.

In addition, as shown in No. 7 rgJ, compared to the conventional temperature raising that is performed at a low air-fuel ratio from the start of temperature raising to prevent oxidation, the high-speed combustion burner performs combustion at a high air-fuel ratio at low temperatures, resulting in a large burner injection force, which increases the combustion inside the container. By being able to stir and circulate the gas and switching to a low air-fuel ratio at a high temperature of 600°C, wasted heat loss was eliminated, and drying heating time and energy were significantly improved. Furthermore, the lifespan of refractories was improved by about 20% compared to conventional drying and temperature raising methods.

[Brief Description of the Drawings] Fig. 1 is a control system diagram showing the method of the present invention, Figs. 2 and 3 are drying and heating devices for a pig iron mixer car and a ladle, respectively, in which the method of the present invention was implemented, and Fig. 4 is a container Graphs showing the relationship between oxygen concentration and oxidation loss depth in Figures 5 and 6rI! I is a graph comparing the life of refractories according to the method of the present invention and the conventional method,
FIG. 7 is a graph showing an example of a drying temperature pattern. ■・・・Pigtail car 2, 6.9...Burner 3
...Rail 4 ... Frame 5 ... Ladle
7...Installation 8...Plate lid opening/closing device i1
10...Thermocouple 11...Program temperature increase controller 12.13...Air-fuel ratio setter 14...Selector switch 15...Fuel pipe 16.
...Air piping 17...Blower 18.19...
·Control valve

Claims (1)

[Claims] 1. When drying and heating a molten metal container lined with a refractory material containing an easily oxidizable material, the container is heated in a preset heating pattern while measuring the internal temperature of the container. Drying and temperature raising of a container for molten metal, which is characterized by drying and heating a container for molten metal, and performing burner combustion at a high air-fuel ratio in the low temperature range of the temperature rising pattern, and switching to a low air-fuel ratio and performing burner combustion in the high temperature range. Method.