JPS5841322B2 - Melting accelerator in arc type electric furnace for steelmaking - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a specific apparatus based on a method for improving the melting rate of steelmaking materials in an electric arc furnace for steelmaking and further improving the heat balance regarding the furnace.

When producing steel by charging pig iron, steel scrap, etc., and melting and refining them in an electric arc furnace for steelmaking, electricity is mainly used as the heat source, and some heavy oil etc. are used as combustion improvers.
is sometimes used.

During the melting stage of the above-mentioned charges such as steel scrap and pig iron,
As this is melted by the arc and the ejection activity from the burner, the temperature inside the furnace becomes high and a large amount of soot and smoke reaching 1,200 to 1,400°C is generated, filling the furnace and making the furnace internal pressure positive. This soot is ejected from the openings around the electrode, tapping port, and the electrode.This soot contains combustion components such as carbon monoxide, and when it ejects from the furnace to the outside, it burns as a flame and remains as it is. It used to be dissipated into the atmosphere as soot and dust, but now all electric furnaces are equipped with dust collectors and are required to collect the soot and dust in order to purify the air.

In other words, as a pollution prevention measure, a large amount of soot and smoke is generated by installing an opening on the top or side of the furnace to collect the smoke and introduce it into a dust collector to prevent it from dispersing into the atmosphere. In particular, the gas discharged from the furnace top elbow is 120
It has thermal energy of 0 to 1400°C or more, and is cooled to 150 to 200°C with a large amount of water, and the dust is collected by a bag filter, and the amount of dust is about 2 to 5 times the amount of steel produced.
% of the weight is generated.

In an electric furnace equipped with such a dust collector, the high temperature gas containing soot generated inside the furnace is sucked out by the dust collector, creating a negative pressure inside the furnace and allowing air to enter the furnace from outside. There was a concern that this would tend to flow in and lower the temperature inside the furnace, resulting in heat loss and prolonging the melting time of steelmaking materials.

The present invention was developed in consideration of the current situation, and is designed to prevent gases such as air from flowing into the furnace due to negative pressure caused by soot suction in an arc-type electric furnace equipped with a dust collector, and which attempts to equalize the furnace pressure. This oxygen-containing gas, which flows into the furnace when negative pressure is generated in the furnace during actual operation, is contained in the contents of the furnace. The purpose of the present invention is to propose a means to oxidize carbon, silicon, manganese, sulfur, phosphorus, tin, etc., and actively shorten the melting time of the charge using the heat of oxidation.

When an electric furnace is equipped with a dust collector to suck in furnace gas containing soot and smoke, air or oxygen is added to the oxygen-containing gas flowing into the furnace instead of allowing a large amount of cooling air to flow in. The air is preheated by heat exchange with the high-temperature gas sucked into the dust collector, and then flows into the electric furnace as a high-temperature oxygen-containing gas to oxidize carbon, silicon, manganese, sulfur, phosphorus, tin, etc. The purpose of the present invention is to provide a specific equipment system capable of actively burning unburned gas, mainly consisting of heat and CO, to reduce the power consumption for melting the charge and at the same time shorten the melting time. It is said that

Next, the present invention will be explained in detail.

The thermal energy of the gas sucked into the dust collector from the electric furnace is approximately 130 x 103K103K/TON, which when converted to electric power is 150 KWH/TON, which is approximately 20% of the total heat input energy as far as conventional methods are used. According to the means of the present invention, this wasted thermal energy is utilized through the exhaust gas that is its medium, so that it is transferred from the electric furnace to the dust collector. A heat exchanger is installed in the middle of the exhaust gas route, and the oxygen-containing gas such as air flowing into the electric furnace or oxygenated air is passed through this part to preheat it and keep it above a certain temperature. This is done so that it flows into the furnace.
In addition, if the pressure drop in the heat exchanger is large compared to the suction pressure of the dust collector, and there is insufficient gas flowing into the furnace, use a blower to blow air and always maintain the appropriate pressure in the furnace before charging. This allows the components contained in the product to be oxidized quickly.

Hereinafter, one example of a specific implementation of the apparatus of the present invention will be explained based on the drawings. As shown in FIG. A combustion chamber 4 with a water jacket 5 for cooling is connected to the top elbow 3, and the generated gas including soot inside the furnace is
If necessary, the air sucked in from the gap formed in the part that communicates with the furnace top elbow 3 is mixed, the contained CO gas is combusted in the combustion chamber 4, and the exhaust gas that has been burned, including all unburned gas, is water-cooled and The post-processing gas, which was appropriately air-cooled and reached the dust collector 6 to remove dust, was dissipated into the atmosphere.

Cold air had appropriately entered the electric furnace from around the electrodes 2, etc., which had a negative pressure in order to suck the gas generated in the furnace into the dust collection system.

In the present invention, as shown in FIG. 2 is an explanatory diagram of the basic idea, and as shown in FIG. A heat exchanger 11 is connected to the furnace top elbow 3 via an exhaust gas pipe 18.

This heat exchanger 11 is configured to heat an oxygen-containing gas passing through a large number of heat exchange tubes disposed in this part in an atmosphere where high-temperature soot introduced from an exhaust gas pipe 18 is combusted.

The temperature of the exhaust gas generated in the electric furnace is lowered by heat exchange, and at the same time, part of the dust in the exhaust gas containing soot falls and settles in the dust reservoir 15 at the bottom of the heat exchanger 11 and is removed, and most of the dust is removed. They are sucked into the dust collector, where they are completely removed and released into the atmosphere.

On the other hand, a cold air supply pipe equipped with a blower 14 and an air supply pipe 12 communicating with an electric furnace are connected to a heat exchanger 11, and when air or an oxygen-containing gas such as oxygen added to air is used, a cold air supply pipe is manufactured. Then, it enters a heat exchanger, increases its temperature by heat exchange, and is supplied into the furnace through the air pipe 12, for example, from the operating port 1 of the furnace.

Moreover, the oxygen-containing gas body preheated by the heat exchanger 11 is
Air supply branch pipe 13 branching from the heat exchanger 11 or the air supply pipe 12
The air is guided around the electrode that passes through the top of the furnace, and forms an air seal in this area, preventing cold air from entering the furnace through the gap around the electrode while allowing it to flow into the furnace.

In the device of the present invention in which a heat exchanger is interposed between the arc type electric furnace and the dust collector, during actual operation, the exhaust gas sucked by the attached dust collector is 1200 to 1400 at the furnace top elbow. ℃, and even near the heat exchanger, the temperature is about 800℃ or higher.

When passing through the dust collector, the temperature of the exhaust gas is 2.
The temperature can be lowered to about 00°C.

On the other hand, the oxygen-containing gas body that exchanges heat with this exhaust gas is a gas body at room temperature, but after passing through the heat exchanger, it becomes a preheated gas body at about 350° C. and flows into the furnace.

The pressure inside the furnace tends to become negative due to the suction pressure of the exhaust gas, and this negative pressure causes the preheated oxygen-containing gas to be introduced into the furnace, and the combustible composition of high oxides contained in the contents inside the furnace. During this period, the furnace internal pressure is detected by the furnace internal pressure measuring device 16, controls the air supply control device 17, drives the blower 14, and controls, for example, a heat exchanger for oxygen-containing gas. By adjusting the back pressure when passing,
The amount of preheated oxygen-containing gas flowing into the furnace and its temperature can be set to optimal conditions for melting the charge.

In this embodiment, the heat exchanger is installed in such a way that multiple thin tubes for heat exchange are placed inside the combustion chamber.
If it is possible to preheat the oxygen-containing gas and supply it into the furnace, the heat exchanger can be installed not only in the combustion chamber but also in an appropriate location depending on the furnace volume or slowing of the furnace. In terms of thermal efficiency, it is preferable that the location be as close as possible to the electric furnace.

Furthermore, in order to improve the heat balance in electric furnaces, a method is often adopted in which charging materials such as steel scraps are preheated by contact with high-temperature exhaust gas, and then charged into the furnace. The heat exchanger that preheats the oxygen-containing gas to be supplied into the furnace can preheat the oxygen-containing gas at a temperature of 350°C either before or after the charge preheating section. Furthermore, the heat in the furnace body, such as the furnace top elbow that connects to the electric furnace, the furnace lid of the furnace body, or the upper part of the furnace side wall, can be transferred to the outside by transmission. An advantage of the present invention is that it is possible to substantially act as a heat exchanger by making the area an air jacket or by running an oxygen-containing gas supply pipe along the area. It is.

By configuring the equipment system as described above, during the melting period of the contents in the electric furnace, the furnace pressure adjustment and appropriate temperature maintenance, which are essential requirements for efficient and rapid melting, can be carried out very easily and under stable conditions. It has come to be.

In other words, melting efficiency will decrease if the amount of oxygen-containing gas such as preheated air or oxygenated air is supplied into the furnace either too little or too much, so the furnace pressure should be adjusted to the optimum pressure. This objective has been distantly achieved by adjusting the amount of preheated oxygen-containing gas delivered using a blower.

It is effective to simultaneously supply the preheated oxygen-containing gas into the furnace from the furnace side or the top of the furnace, and at the same time to prevent the tilting of the furnace body when discharging the melted material from the furnace. In some cases, as shown in FIG. 3, the exhaust gas pipe, the air supply pipe, the air supply branch pipe, etc. are each of the sleeve type and are of course detachable.

Here is an example of a 30-ton electric furnace in which a preheated oxygen-containing gas was fed into the furnace using the method and equipment described above: (a) Melting power was reduced by 52 KWH per ton.

This corresponds to over 15 of the total required power.

(b) The dissolution time could be reduced by about 4 minutes and 20 seconds.

This means that the conventional dissolution time was reduced by about 8.6 times.

(c) Oxygen was sprayed onto the red-hot scrap using a lance pipe for quick melting, reducing the amount of acid used when cutting the charged material.

It also saved fuel oil for combustion.

2) Since the exhaust gas passes through the dust collector at a low temperature, the life of the cleaning cloth etc. can be extended.

Remarkable effects such as these were obtained.

The specific device that brings about the effects of the present invention is not limited to the above description and one example of implementation, and modifications, applications, diversions, etc. derived therefrom are also within the technical scope of the present invention. Needless to say, it is included in thought.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of conventional means, FIG. 2 is an explanatory diagram of the basic idea of the present invention, and FIG. 3 is a diagram showing an example of the implementation of the present invention. 1... Electric furnace, 2... Electrode, 3...
...Furnace top elbow, 4...Combustion chamber, 5...
...Water jacket, 6...Dust collector, 7
......Operating port, 11...Heat exchanger, 12
...Air supply pipe, 13...Air supply branch pipe, 14
...Blower, 15 ...Dust collection, 1
6... Furnace pressure measuring device, 17... Air supply control device, 18... Exhaust gas pipe.

Claims (1)

[Claims] 1. In an electric furnace equipped with a dust collector to treat exhaust gas containing soot and dust generated when melting the contents in the furnace, pig iron,
When melting materials in the furnace such as steel scraps, air preheated to a temperature higher than room temperature or an oxygen-containing gas such as air with oxygen added to it is supplied into the furnace from the operating port of the furnace or around the electrodes, and collected. In order to compensate for the negative pressure in the furnace due to the suction of the dust device to an appropriate furnace pressure, and to cause the gas to react with the high oxide contained in the charge to generate vigorous oxidation heat generation,
A heat exchanger is interposed at an appropriate location on the route including the exhaust gas combustion section between the opening part such as the furnace top elbow that leads the exhaust gas out of the furnace and the dust collector, and the heat receiving inlet side of this heat exchanger is An inlet pipe for an oxygen-containing gas such as air at room temperature or air to which oxygen has been added is connected, and the outlet side of this pipe is removably connected to the operation port of the electric furnace, so that the gas is preheated by the exhaust gas of the electric furnace. 1. A melting accelerator in an electric arc furnace for steelmaking, characterized in that an oxygen gas is supplied into the furnace.