JPH0535349B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for melting scrap, etc., and in particular, to a method for melting scrap, etc., which can achieve power saving and effective use of sensible heat and heat from exhaust gas. Concerning a method of dissolving.

[Prior Art] A three-phase arc furnace that utilizes the arc heat of three-phase electrodes is already known as a device for melting solid iron, such as scrap, in order to recycle it.

In this arc furnace, raw material scrap is placed in the arc furnace main body, which is open at the top, and a three-phase electrode is inserted into this, the top lid is placed on it, and the raw material is discharged, and the raw material is melted by the arc heat. It is something. The exhaust gas generated from the arc furnace body is mainly composed of air that has entered the furnace from the surrounding area, but it also contains some combustible components such as CO, so the exhaust gas is taken out from inside the furnace and burned. This combustion gas is used to preheat the raw material scrap, making effective use of heat.

[Problems to be Solved by the Invention] By the way, when melting raw materials such as scrap using arc heat as in the conventional melting method, a large amount of electric power is required even though preheating is performed using exhaust gas. Especially in countries like Japan where electricity costs are high, operating costs have been forced to rise.

Therefore, although electrical energy and oil or petroleum gas are used together for melting,
Oil, petroleum gas, etc. are also expensive, and operating costs cannot be reduced sufficiently.

In addition, other raw materials are preheated using the high-temperature exhaust gas generated during melting, but the temperature of this exhaust gas is low at around 600 degrees, so the preheating temperature of the raw materials is even lower at 200 to 300 degrees, making it difficult to preheat them sufficiently. can't do it.

Furthermore, although combustion of combustible gas contained in the exhaust gas has been carried out, the content of combustible gas is very low and the temperature of the exhaust gas cannot be raised sufficiently.

Furthermore, as mentioned above, since the preheating temperature of the raw materials is low, malodorous components generated by thermal decomposition of organic components contained in the raw materials have become a source of pollution.

Particularly in today's world where scrap consumption is expected to increase significantly in the future, it is desired to solve the above-mentioned problems as soon as possible.

[Object of the Invention] The present invention has focused on the above-mentioned problems and has been devised to effectively solve the problems.

The purpose of the present invention is to cause a combustible gas producing reaction by blowing carbonaceous material into a melting furnace together with oxygen or air, and to melt the raw material using the reaction heat, and
The present invention relates to a method for melting scrap, etc., which sequentially recovers sensible heat and radiant heat from emitted combustible gas, thereby significantly reducing power consumption.

[Summary of the Invention] The structure of the present invention that achieves the above object is as follows: First, carbonaceous material is blown into a melting furnace together with air, and the carbonaceous material is reacted with oxygen to generate combustible gases such as CO, H, etc. _2, etc., the charged raw material is melted by this reaction heat, and then the discharged high temperature combustible gas is introduced into the primary raw material preheater to preheat the raw material charged therein. recover heat,
Furthermore, the high-temperature exhaust gas obtained by burning the combustible gas after sensible heat recovery is introduced into the secondary raw material preheater, and the other raw materials charged therein are preheated at a high temperature, thereby recovering the residual heat. The main point is that the sensible heat and heat of the exhaust gas are effectively utilized.

[Example] Below, the method of the present invention will be explained in detail based on the accompanying drawings.

FIG. 1 is a schematic plan view showing melting furnace equipment for carrying out the method of the present invention.

As shown in the figure, this melting furnace equipment includes a melting furnace 1 that melts charged raw materials, a first raw material preheater 2 that recovers sensible heat from high-temperature combustible gas generated during melting, and a first raw material preheater 2 that burns the combustible gas after recovering the sensible heat. It mainly consists of a combustion tower 3 and a second raw material preheater 4 that preheats other raw materials at a high temperature using high-temperature exhaust gas discharged from the combustion tower 3 and recovers heat from the combustion tower.

Above the furnace lid 5 of the melting furnace 1, there is an electrode 6 that can be inserted into and removed from the furnace, and a high-temperature gas discharge port 7 for discharging flammable high-temperature gas generated during melting to the outside of the furnace. It is formed. In addition, a tapping port 8 is formed on the bottom side wall of the furnace to take out the molten steel produced in the furnace, and a carbon material injection port 8 is formed at the bottom of the furnace to blow carbon material such as pulverized coal into the furnace together with oxygen or air. A mouth 9 is formed.

The high-temperature gas outlet 7 of the melting furnace 1 is connected to the gas inlet 11 of the primary raw material preheater 2 via a high-temperature combustible gas passage 10. Further, the gas outlet 12 of the primary raw material preheater 2 is connected to the gas inlet 13 of the combustion tower 3.
The tower is connected to the tower through a passage 14, and the combustible gas introduced into the tower is combusted. A gas outlet 15 of the combustion tower 3 is connected to a high temperature exhaust gas inlet 17 of the secondary raw material preheater 4 via a high temperature exhaust gas passage 16. The gas outlet 18 of the secondary raw material preheater 4 is connected via a low temperature gas passage 21 to the gas inlet 20 of a combustion air preheater 19 for preheating the combustion air used in the combustion tower 3. There is. A gas outlet 22 of the combustion air preheater 19 is connected to a gas inlet 26 of a dust collector 25 via a gas passage 24 in which a blower fan 23 is interposed.
The exhaust gas from which dust has been removed by the dust collector 25 is discharged out of the system from a gas outlet 27.

Next, the method of the present invention will be specifically explained based on the melting furnace equipment configured as described above.

First, a carbon material such as pulverized coal, char, or coke is injected into the melting furnace 1 from a carbon material inlet 9 provided at the bottom of the melting furnace 1 together with oxygen or air. Initial molten steel is previously formed in the melting furnace 1 by arc heat or by leaving a small amount of molten steel produced in a previous process. The injected oxygen causes an exothermic reaction with the carbon injected into the molten iron, generating CO, H ₂ and hydrocarbon-based combustible gases. The amount of heat generated at this time heats up the charged raw material and melts it.

The generated high-temperature combustible gas has a temperature of about 600° C. and is discharged from the high-temperature gas outlet 7, passes through the high-temperature combustible gas passage 10, and is introduced into the primary raw material preheater 2. Other raw materials are charged in advance into the primary raw material preheater 2, and this raw material is primarily preheated with the above-mentioned high temperature combustible gas to recover the sensible heat possessed by the exhaust gas. In this primary preheating, the temperature of the high-temperature combustible gas serving as the heat source is relatively low at about 600°C, so the raw material can only be preheated to 200 to 300°C. Then, this preheated raw material is then transferred to the melting furnace 1.
It will be transported inside and dissolved. Above 1
In the next preheating, since the preheating temperature is low, organic components contained in the raw materials are decomposed to produce malodorous components, but these malodorous components are transported to the downstream side together with the combustible gas.

That is, the gas outlet 12 of the primary raw material preheater 2
The combustible gas discharged from the combustion chamber after sensible heat recovery contains malodorous components, and this combustible gas is introduced into the combustion tower 3 from the gas inlet 13 via the passage 14,
This combustible gas introduced into the combustion air preheater 19
Burned by combustion air supplied from the side, approximately
The result is high-temperature exhaust gas of around 1000℃. At this time, the malodorous components conveyed together with the combustible gas from the primary raw material preheater 2 are thermally decomposed due to the high heat within the combustion tower 3 and become malodorous.

Here, the generated high-temperature gas is discharged from the gas outlet 15 of the combustion tower 3, flows through the high-temperature exhaust gas passage 16, and is introduced into the secondary raw material preheater 4 through the high-temperature exhaust gas inlet 17. In this secondary raw material preheater 4, other raw materials are charged in advance,
This raw material is secondarily preheated using the high-temperature exhaust gas to recover heat from the heat. The high-temperature exhaust gas that is the heat source for this secondary preheating is particularly high at about 1000°C, so the raw material charged in the preheater 4 is preheated to a high temperature of about 600 to 800°C. In addition, the malodorous components generated during this high-temperature preheating are caused by the fact that the secondary preheating itself is carried out at a high temperature of 800°C or higher.
Immediately thermally decomposed.

The gas, which has become relatively low in temperature due to the heat recovery, is transferred to the gas outlet 18 of the secondary raw material preheater 4.
It flows through the low temperature gas passage 21 and is introduced into the combustion air preheater 19 through the gas inlet 20. Since this introduced exhaust gas is still at a high temperature compared to the outside temperature, the combustion air used in the combustion tower 3 is preheated by the sensible heat possessed by this exhaust gas,
Furthermore, heat recovery is performed. The combustion air preheated here is introduced into the combustion tower 3 through the passage 28 as described above and contributes to the combustion of combustible gas.

On the other hand, the exhaust gas discharged from the combustion air preheater 19 flows through the gas passage 24, passes through the blower fan 23 and the dust collector 25, and is then discharged into the atmosphere.

In this way, while melting the raw materials in the melting furnace 1, sensible heat recovery and radiant heat recovery are performed from the high-temperature combustible gas generated by the melting, and when the melting work is completed, the molten steel is taken out from the tapping port 8, Furthermore, raw materials preheated at a low temperature or at a high temperature in the primary raw material preheater 2 or the secondary raw material preheater 4 are charged into the now empty melting furnace 1 and melted in the same manner as described above.

As described above, in the method of the present invention, first, carbonaceous material is blown into a steel melting furnace together with air, etc., so that the carbonaceous material reacts with oxygen to generate combustible gas, and the charged raw material is melted by the heat of this reaction. Next, the discharged high temperature combustible gas is introduced into the primary raw material preheater,
Sensible heat is recovered by preheating the raw material charged in this chamber, and the high-temperature exhaust gas obtained by burning the combustible exhaust gas after the sensible heat recovery is introduced into the secondary raw material preheater. Since the heat is recovered by preheating other raw materials charged at high temperature, there is no need to perform arc heating throughout the entire process, and even if it is used, it is only used during the initial molten steel production, significantly reducing power consumption. can be reduced to

Specifically, in the past, depending on the size of the melting furnace, the electric energy used to melt raw materials was 450 ~
470KWH/T was required, and even if auxiliary combustion energy such as an oil burner was used, 360 to 400KWH/T was required, but according to the method of the present invention, 250KWH/T was required.
T or less, and significant power savings can be achieved.

In addition, since the high-temperature combustible gas generated when melting raw materials is recovered in two stages by performing sensible heat recovery and infrared heat recovery, the amount of heat recovered was conventionally 30 to 50 KWH/T, but the present invention 70~
The amount of heat recovery can be improved to 100KWH/T.

Furthermore, since the primary raw material preheater 2 and the secondary raw material preheater 4 can perform low-temperature preheating and high-temperature preheating, respectively, it is possible to select whether low-temperature preheating or high-temperature preheating should be performed depending on the type of raw material to be preheated. The degree of freedom in selecting preheating conditions can be increased. That is, since the melting temperature differs depending on the type of raw material, if the melting temperature of the raw material is low, low-temperature preheating is performed to suppress raw material melting during preheating, and if the raw material has a high melting temperature, high-temperature preheating is performed. Do it like this.

[Effects of the Invention] In summary, according to the present invention, the following excellent effects can be achieved.

(1) A combustible gas generation reaction is caused by injecting carbonaceous material,
Since the raw material is melted by this reaction heat and sensible heat and heat are recovered from the resulting high-temperature combustible gas, power consumption can be significantly reduced compared to the conventional example.

(2) Malodorous components generated during low-temperature preheating can be thermally decomposed by high-temperature gas generated during combustion of combustible gas in the combustion tower, thereby preventing malodor pollution.

(3) Since low-temperature preheating and high-temperature preheating are possible, the preheating state can be selected depending on the type of raw material, and the degree of freedom in selecting the preheating state can be increased.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing melting furnace equipment for carrying out the method of the present invention. In addition, in the figure, 1 is a melting furnace, 2 is a primary raw material preheater,
3 is a combustion tower, 4 is a secondary raw material preheater, 9 is a carbon material inlet, and 19 is a combustion air preheater.

Claims (1)

[Claims] 1. When melting raw materials such as scrap, carbonaceous materials undergo a reaction to generate combustible gas in the presence of oxygen-containing gas, the raw material is melted by the heat of reaction, and the resulting high-temperature combustible gas is used to preheat other raw materials to generate sensible heat. A method for melting scrap, etc., characterized in that the combustible gas after sensible heat recovery is burned, and then other raw materials are preheated using the high temperature exhaust gas generated to recover the heat.