SU1765183A1 - Method for melting steel in hearth steel-melting unit - Google Patents

Abstract

Usage: in the field of ferrous metallurgy, namely, in the smelting of steel in the hearth steelmaking units with oxygen blowing. The essence of the invention: oxygen for the afterburning of CO is fed into the atmosphere of the furnace from a height of 0.2 - 0.3 of the height of the arch from the thresholds of the charging windows. The jets of oxygen are directed towards the surface of the bath, at an angle of 50 - 60 ° C to the vertical. The number of jets is equal to 1500 - 3500 from the ratio of the nozzle caliber to the height at which oxygen is introduced into the furnace atmosphere, 2 tab.

Description

This invention relates to ferrous metallurgy, in particular, to methods for smelting steel in double-bath steel-making units and open-hearth furnaces.

The aim of the invention is to increase the durability of the refractory lining.

The goal is achieved by the method of steel smelting in an underwater steelmaking unit, which includes supplying oxygen through separate oxygen tuyeres into a bath and into the furnace atmosphere with separate jets at different levels, oxygen is fed into the furnace atmosphere from a height of 0.2 - 0.3 of the arch height from the level of the thresholds, charging windows, jets directed to the bath surface at an angle of 50–60 ° to the vertical, while the number of jets is assumed to be (1,500–3,500) from the ratio of the tuyere nozzle to the height,

with which oxygen is introduced into the furnace atmosphere.

The implementation of this process is carried out by optimizing the scheme of interaction of the oxidant with the bath, including through the rational organization of oxygen flows in the furnace atmosphere.

The determination of the optimal characteristics of the movement of gases in the working space was made on a cold model of an open-hearth furnace, made on a scale of 1: 15, observing the criteria of Archimedes, Reynolds and Froude. Water was used as a modeling fluid. Compressor air was used as a simulating oxidant. The speed of air movement in the lining phase above the slag catfish and in the sub-drift region was used as the optimization parameter.

Xi

ON

00 WITH

As a result of model experiments, it was found that when the oxidant supply is less than 0.2 heights of the arch, the velocity of air above the slag catches increases dramatically, which indicates an unavoidable decrease in the durability of the lining of the back and front walls of the furnace when this mode is implemented.

When the oxidizer is supplied from a height of more than 0.3 of the height of the roof, the movement of gases in the subsurface area is noticeably accelerated, which will lead to overheating of the roof in natural conditions.

When the oxidant is introduced at an angle of more than 60 ° to the vertical, even at the minimum height of the fornix, the streams fall on the lining both due to direct contact and due to the distribution over the bath mirror. When the oxidant is introduced at an angle of less than 50 ° to the vertical, the proportion of gas reflected from the surface of the bath and falling on the walls and roof of the furnace increases, which leads to a decrease in the durability of the lining.

During studies on the model, it was found that the rate of wear of the lining is significantly influenced by the number of jets of oxidant with which it is introduced into the atmosphere at the flow rate. Moreover, the optimal number of jets depends on the ratio of their diameter (caliber) at the cutter of the feeding device to the height at which they are inserted. If the number of jets is less than 1500 of this ratio, the kinetic energy of the jet rises to values at which it is not quenched as a result of interactions from the bathroom. This leads to the penetration of jets to the lining, increased spatter formation and reduced resistance of the furnace working space. When the number of jets is greater than 3500 the ratio of the diameter (caliber) of the jet at the shear of the feeding device to the height at which the oxidizer is introduced into the bath, the jet of oxidant deviates from the calculated trajectory by the furnace’s smoke extractor; the movement of furnace gases and with them falls on the roof and walls of the unit, reducing their resistance. The average values of the measured Pitto-Prandtl tube air flow rates along the rear wall (10 control points) and speeds under the roof (12 control points) are shown in Table 1.

From the data presented in Table 1 it follows that with the stated values of operating parameters, high-speed jets of oxidizer do not fall on the furnace lining, as evidenced by the decrease in speed

gas movement in the area immediately adjacent to the lining.

PRI me R 1. The invented method was implemented in steelmaking in a two-bath steelmaking unit 2 x 250 tons.

The unit worked with an oxygen consumption of 8000 m3 / h.

In the initial state, the unit was equipped with a system of end oxygen

tuyeres implementing prototype technology. According to the proposed method, the unit was equipped with arched two-level oxygen lances that realize the average values of the parameters of the proposed method.

The height of the arch above the thresholds of the charging windows was 3.7 m, the height of the second rus of nozzles above the level of the calm bath was 3.7 x X 0.25 0.92 m, the angle of the nozzles of the upper rus was

verticals were set to 50 °. The number of jets was

2500 x

0.01 0.92

27,

where 2500 is the average value of the claimed coefficient;

0.01 — nozzle diameter equal to the jet diameter at the cutter of the feeding device, m; 1.3 - the height from which oxygen was supplied, m

The oxygen jets were distributed into three tuyeres (9 pcs. Each).

According to the claimed technology, a campaign of heats was carried out to achieve a residual thickness of the brick 150 mm.

The results of the experimental heats are presented in Table 2.

Thus, industrial testing of the proposed method confirmed the efficiency of the developed method of steel smelting and its advantages in comparison with the prototype both in lining durability and in technological indicators.

The effectiveness of the proposed technical solution is 0.2 rubles per ton of steel.

Claims (1)

Invention Formula The method of steelmaking in the hearth steelmaking unit, including the supply of oxygen through separate oxygen tuyeres into the bath and into the furnace atmosphere, by separate streams at different levels, characterized in that, in order to increase the resistance of the refractory lining, oxygen is supplied to the furnace atmosphere from a height of 0.2 - 0.3 of the height of the arch from the level of the thresholds of the charging windows, jets, directed to the surface of the bath at an angle of 50 - 60 ° to the vertical, with the number of jets being equal to 1500 - 3500 from ratios of the tuyere nozzle caliber to the height at which oxygen is introduced into the furnace atmosphere. Average values of the speed of the oxidizer in the vicinity of the surface of the lining of the unit lining, and / s (1 - along the centerline of the vault, 2 - along the joint line of the sandwich with the rear wall, 3 - at the level of the charge package, 4 - at the height of the rear wall) table 2 Comparative performance of the steelmaking unit when using claimed solution Table 1