JP2000292074A - Scrap preheating equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a preheating apparatus for a preheating furnace provided in a preceding stage of a melting furnace when melting iron-based scrap. An electrical or CO to fossil fuel generated from a melting furnace and refining furnace to an energy source, is burned leading the exhaust gas containing combustible gas such as H ₂ directly, a rotary kiln type preheating the scrap to be inserted into the melting furnace In the scrap preheating device, the discharge angle of at least one auxiliary burner of the exhaust gas combustion auxiliary burner in a plane perpendicular to the rotation axis of the rotary kiln intersects with the bottom of the rotary kiln type preheating furnace in a downward direction with respect to the auxiliary burner central axis. A scrap preheating device, which is disposed at an angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preheating apparatus for a preheating furnace which is provided in a stage preceding a melting furnace when melting iron-based scrap.

[0002]

2. Description of the Related Art In melting furnaces and refining furnaces that use electric or fossil fuel as an energy source, when iron-based scrap is melted and reused, the sensible heat and latent heat of the exhaust gas are effectively used to achieve high efficiency. It is desired to dissolve iron-based scrap. A facility for preheating the iron-based scrap is disposed at a stage preceding the melting furnace for the iron-based scrap. Conventional examples of such preheating equipment are roughly classified into two types, a shaft furnace type and a rotary kiln type. Among these, the rotary kiln type preheating furnace has, for example, a configuration in which a rotary kiln is connected to an upper part of an electric furnace, and has a structure in which scrap is sufficiently preheated and inserted into the furnace.

In such a rotary kiln type preheating furnace, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 10-300364, a plurality of nozzles for injecting a combustion supporting gas in parallel with the rotation axis of the rotary kiln are provided in a plane perpendicular to the rotation axis of the rotary kiln. A device for preheating and melting the scrap to be disposed is disclosed. Thus, in order to burn combustible exhaust gas generated in the melting furnace and preheat the scrap, a flame is formed in the rotary kiln, and the scrap is preheated in the rotary kiln, thereby preheating the scrap.

[0004]

However, when the combustible exhaust gas generated in the melting furnace is formed into a flame in the rotary kiln and burned in the rotary kiln, the oxygen in the air entrained from the furnace opening of the scrap melting furnace is reduced. Is present in a mixed state in the exhaust gas and cannot itself have a large momentum such as combustion air, so it does not have sufficient turbulence intensity necessary to cause combustion with combustible gas, Therefore, it becomes difficult to consume all oxygen for combustion in the rotary kiln type preheating furnace, and there is a problem that combustible gas and oxygen are discharged from the rotary kiln type preheating furnace in a mixed state.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive developments, and as a result, in a melting furnace exhaust gas stream containing air entrained from a furnace opening of a scrap melting furnace. Another object of the present invention is to provide a device that promotes turbulent mixing of both by positively blowing a jet of auxiliary combustion air to promote a combustion reaction of oxygen in combustible gas with exhaust gas from a melting furnace.

The gist of the invention is as follows: (1) Exhaust gas containing combustible gas such as CO and H ₂ generated from a smelting furnace and a smelting furnace using electric or fossil fuel as an energy source is directly introduced and burned, In a rotary kiln-type scrap preheating apparatus for preheating a scrap to be inserted into a melting furnace, a discharge angle of at least one or more auxiliary combustion burners of an exhaust gas combustion auxiliary burner in a plane perpendicular to a rotation axis of the rotary kiln, with respect to a central axis of the auxiliary burner. A scrap preheating apparatus, which is disposed downward at an angle that intersects the bottom of a rotary kiln type preheating furnace. (2) The discharge angle of the auxiliary burner described in (1) is 5 to 3
A scrap preheating apparatus characterized in that the temperature is set to 0 degrees.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a preheating furnace according to the present invention. As shown in FIG. 1, one end of an inclined rotary kiln type scrap preheating furnace 2 rotatable around a cylindrical axis is connected to the upper part of the scrap melting furnace 1, and the other end of the scrap preheating furnace 2 is connected to The lower part of the shaft furnace type second preheating furnace 3 extending to a certain height in the vertical direction is continuously provided. The iron-based scrap is charged from the upper part of the second preheating furnace 3, and the exhaust gas passing through the scrap preheating furnace 2 and the second preheating furnace 3 from the scrap melting furnace 1 is also discharged from the upper part of the second preheating furnace 3. It is a form that is discharged from.

In such a facility, the scrap charged from the upper part of the second preheating furnace 3 is preheated in the preheating furnace 3 and then sent to the next scrap preheating furnace 2 to be preheated to a higher temperature again. After that, it is charged from above the scrap melting furnace 1 and melted. In this case, it is necessary to always fill the shaft furnace type second preheating furnace 3 with scrap.
The scrap preheating furnace 2 loads the scrap into the scrap melting furnace 1 while adjusting the rotation speed of the rotary kiln according to a required scrap charging speed.

Exhaust gas generated from the scrap melting furnace 1 is kept at a high temperature while a rotary kiln type scrap preheating furnace 2
And heat exchange with the scrap, but in the scrap preheating furnace 2, the fusion of the scrap does not occur due to the rotation. Further, in the scrap preheating furnace 2, combustible gas such as CO and H ₂ gas in the exhaust gas 4 generated from the scrap melting furnace 1 is burned by the auxiliary combustion gas of the auxiliary combustion burner 5. Thereby, the preheating effect can be improved. The exhaust gas having undergone the heat exchange in the scrap preheating furnace 2 is introduced into a shaft furnace type second preheating furnace 3 where it is exchanged with scrap.

In the present invention, the exhaust gas 4 generated from the scrap melting furnace 1 is led to the scrap preheating furnace 2 and is burned by the combustion gas of the combustion burner 5. At this time, the discharge angle of the auxiliary burner 5 is inclined downward so that the point where the oxygen concentration in the combustion flame 6 attenuates to zero comes into contact with the furnace bottom refractory 7. This discharge angle is disposed at an angle of 8 at the intersection with the bottom of the rotary kiln-type preheating furnace with respect to the central axis of the auxiliary burner, and is 5 to 30 degrees, preferably 10 to 10 degrees.
25 degrees. This promotes the complete consumption of oxygen in the intruded air 9 from the furnace opening of the scrap melting furnace 1 mixed in the exhaust gas 4 generated from the scrap melting furnace 1 in the scrap preheating furnace 2, and the amount of auxiliary combustion gas It is possible to prevent the unreacted oxygen in the exhaust gas from the scrap preheating furnace from being mixed with the CO gas, thereby preventing abnormal combustion in the downstream process.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a series of scrap melting equipment shown in FIG. The iron-based scrap was melted in such a state that the combustion flame was blown at the respective angles shown in Table 1 with respect to the central axis of the combustion burner so that the combustion burner was discharged so as to be contained in the preheating furnace. At that time, the composition of the exhaust gas generated from the scrap melting furnace was as follows: CO 40%, CO ₂ 30%, H ₂
3%, N ₂ 27% and the flow rate was 1300 Nm ³ / hr. 1200 Nm ³ / hr of air is injected into the exhaust gas from the nozzle as a combustion supporting gas, and the scrap is reduced to 3 tons.
Dissolved at a throughput of on / hr. On the other hand, as a comparative example,
Table 1 shows the combustion state in the case where a plurality of nozzles for injecting the auxiliary gas under the same conditions are provided substantially in parallel with the rotation axis of the rotary kiln-type scrap preheating furnace.

[0012]

[Table 1]

As shown in Table 1, Nos. 1 to 6 are examples of the present invention, and Nos. 7 to 10 are comparative examples. As can be seen from this table, by blowing the auxiliary combustion gas according to the present invention at a blowing angle of 5 to 30 degrees having an intersection with the bottom of the refractory of the scrap preheating furnace, the air caught from the furnace outlet of the scrap melting furnace is blown. The preheating temperature of the scrap is increased by promoting turbulent mixing as an assisting air jet in the flow of the melting furnace exhaust gas that contains it to promote the turbulent mixing and reducing the oxygen concentration in the melting furnace exhaust gas to almost zero. No abnormal combustion occurred. On the other hand, in Comparative Examples 7 to 10, it was confirmed that all of the unreacted CO gas was contained. Therefore, the preheating temperature of the scrap was low, and abnormal combustion occurred in the downstream process. .

[0014]

As described above, according to the present invention, the oxygen in the air entering from the furnace opening of the scrap melting furnace mixed into the exhaust gas generated from the scrap melting furnace is completely consumed in the scrap preheating furnace, This is an extremely excellent effect that can reduce the amount of auxiliary gas and improve the preheating effect, and prevent the unreacted oxygen in the exhaust gas of the scrap preheating furnace from being mixed with CO gas to prevent abnormal combustion from occurring in downstream processes. is there.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a preheating furnace according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scrap melting furnace 2 Scrap preheating furnace 3 2nd preheating furnace 4 Exhaust gas 5 Burning burner 6 Combustion flame 7 Bottom refractory 8 Intersection 9 Intrusion air

Claims (2)

[Claims] 1. A rotary kiln for directly heating and combusting exhaust gas containing combustible gas such as CO and H ₂ generated from a melting furnace and a refining furnace using electric or fossil fuel as an energy source, and preheating a scrap to be inserted into the melting furnace. In the mold scrap preheating device, the discharge angle of at least one combustion burner for exhaust gas combustion in a plane perpendicular to the rotation axis of the rotary kiln, the intersection with the bottom of the rotary kiln preheating furnace in a downward direction with respect to the combustion burner center axis A scrap preheating device, which is disposed at an angle. 2. A scrap preheating apparatus according to claim 1, wherein the discharge angle of the auxiliary burner is 5 to 30 degrees.