JPH0735882B2 - Pulverized coal combustion method - Google Patents

Description

The present invention relates to a pulverized coal combustion method, and more particularly to a pulverized coal combustion method in an electric furnace for melting steel scrap and a burner for a melting furnace for melting aluminum, copper or the like. .

[Conventional technology]

Most of the burners for melting steel scrap, aluminum, copper, etc. use liquid fuel such as heavy oil and oxygen, oxygen-enriched air or air, and some of them are disclosed in JP-A-59-59.
As disclosed in Japanese Patent Laid-Open No. 115904, co-firing of pulverized coal and gaseous fuel or co-firing of pulverized coal and liquid fuel.

By the way, the combustion speed of pulverized coal with low energy cost is much slower than that of liquid fuels such as heavy oil, and it has almost no dissolution capacity such as steel scrap, so most of liquid fuels such as heavy oil with high energy cost are used. is occupying.

When pulverized coal and liquid combustion or mixed combustion of pulverized coal and gas fuel are used, when radiating heat such as steel scrap, aluminum, and copper, radiant heat from the furnace wall is small near the burner, and only pulverized coal is stable. Since a flame may not be obtained and may extinguish, increase the mixing ratio of liquid fuel or gaseous fuel until the temperature near the burner rises, and decrease this mixing ratio after the temperature near the burner rises. ing.

[Problems to be solved by the invention]

However, although the energy cost of this pulverized coal and liquid fuel or gas fuel co-firing is lower than that of combustion of heavy oil, the energy cost is also high when compared with pulverized coal exclusive combustion, and The co-firing burner has a drawback that the structure is complicated.

Therefore, the present invention provides a scrap melting electric furnace, a burner for melting a metal such as aluminum or copper, and a high temperature (20%) even when the temperature in the vicinity of the burner is insufficient for ignition of pulverized coal.
It is an object of the present invention to provide a pulverized coal combustion method capable of forming a stable flame at a temperature of at least 00 ° C.) and having a sufficient melting ability and capable of pulverized coal combustion alone.

[Means for solving problems]

In order to achieve the above object, the method of the present invention forms a pulverized coal combustion flame by burning a combustion-supporting gas having an oxygen concentration of 30% or more preheated to 80 ° C. or more and pulverized coal preheated to 300 ° C. or less,
When melting metal such as steel scrap, aluminum, and copper with the flame, T = flammable gas temperature [° C], C =
Assuming that the oxygen concentration in the combustion-supporting gas [%], t = pulverized coal temperature [° C], T ≥ exp {14.14-1.84 ・ InC-exp (0.01127t-3.44)
4)} is characterized in that it is burned so as to satisfy the condition.

As a melting burner for metals such as steel scrap, aluminum and copper, it is required to form a flame close to the combustion characteristics of liquid fuel such as heavy oil. The flame temperature must be about 2000 ° C or higher. Further, it is required to form a flame that is stable and high even if the ambient temperature near the burner is about several hundred degrees.

By the way, pulverized coal consisting of about 15 to 30% of volatile components and 45 to 60% of fixed carbon was burned at a normal temperature of 20 ° C. oxygen in an air atmosphere, but a flame could not be formed. Therefore, the oxygen temperature 15
When preheated to 0 ℃ and pulverized coal temperature of 150 ℃, a stable flame of about 2000 ℃ can be obtained and stable in relation to oxygen concentration in combustion-supporting gas, combustion-gas preheating temperature, and pulverized coal preheating temperature. The flame forming zone is as shown in FIG.
≧ exp {14.14-1.84 ・ InC-exp (0.01127t-3.444)}
It was found that there is a relationship.

That is, if the preheat of pulverized coal is higher than 300 ° C, low temperature tar is extracted and it becomes difficult to convey the pulverized coal.The preheating of pulverized coal is up to 300 ° C, the oxygen concentration in the combustion supporting gas is 30 ° C or higher, It was found that a flame of about 2000 ° C or higher can be formed when combustion is performed using a pulverized coal burner with a preheating temperature of the characteristic gas of 80 ° C or higher. The method of the present invention has been completed based on this situation.

〔Example〕

 Examples of the method of the present invention will be shown below.

Pulverized coal (volatile components 15-30%, fixed carbon 45-60%, ash 10
~ 20%, particle size 200 mesh or less 85%) is preheated to 260 ℃,
The oxygen concentration in the combustion-supporting gas is 30 to 100%, the temperature of the combustion-supporting gas is 700 ° C., and pulverized coal is burned in the atmosphere with a burner.
A stable flame was obtained and the flame temperature was measured.

The results are shown in FIG. As can be seen from FIG. 2, the flame temperature was as high as 2000 to 2400 ° C, and the ability to dissolve steel scrap, aluminum, copper, etc. was also good.

〔The invention's effect〕

As described above, the combustion-supporting gas containing 30% or more of oxygen concentration
In preheating to 80 ° C. or higher and preheating pulverized coal to a maximum of 300 ° C. and burning the pulverized coal with the combustion-supporting gas, the method of the present invention is T ≧ exp {14.14−1.84 · InC−exp (0.01127t− 3.
444)} is burned to satisfy the conditions of (444)}, so the energy cost is low in burners that require high flame temperatures (about 2000 ° C or higher) and melting capacity in melting metals such as steel scrap, aluminum, and copper. The pulverized coal can be burned exclusively.

In addition, since the pulverized coal can be burnt exclusively, the co-firing part and the liquid and gas fuel devices necessary for the co-firing burner of pulverized coal and liquid fuel or gas fuel are not required, and pulverized coal and liquid fuel or pulverized coal The burner can be made more compact than the mixed burner for gaseous fuel.

[Brief description of drawings]

Fig. 1 is a graph showing the relationship between oxygen concentration in combustion-supporting gas, preheating temperature of combustion-supporting gas, pulverized coal preheating temperature, and stable flame formation zone. Fig. 2 is pulverized coal preheating temperature of 260 ℃, combustion-supporting zone. FIG. 6 is a graph showing the relationship between the oxygen concentration in the combustion-supporting gas and the flame temperature when the preheating temperature of the propellant gas is 700 ° C.

Claims (1)

[Claims] 1. A pulverized coal combustion flame is formed by burning a combustion-supporting gas having an oxygen concentration of 30% or more preheated to 80 ° C. or more and pulverized coal preheated to 300 ° C. or less, and steel scrap or aluminum is produced by the flame. When melting metals such as copper, T
= Turn gas temperature [℃], C = Oxygen concentration in fuel gas [%], t = Pulverized coal temperature [℃], T ≧ exp {14.14-1.84 ・ InC-exp (0.01127t- 3.44
4)} Pulverized coal combustion method characterized by burning so as to satisfy the condition of.