JPH0535351B2 - - 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.

In addition, as a melting method that effectively utilizes the exhaust gas generated during melting, two melting furnaces are installed side by side and communicated with each other through an exhaust gas passage. Exhaust gas is introduced into the other melting furnace to preheat the raw material previously charged therein, and melting and preheating of the charged raw material are alternately repeated.

[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 provide a plurality of melting furnaces having both melting and preheating functions, and when melting and preheating are repeated alternately, high-temperature combustible material generated by injection of carbonaceous materials during melting of raw materials in one melting furnace is to be avoided. First, sensible heat is recovered from the gas, and then the high-temperature exhaust gas generated by burning this combustible gas is used to preheat the raw materials in other melting furnaces and recover the sensible heat, thereby significantly reducing power consumption. The purpose is to provide a method for dissolving scraps, etc. that can be used.

[Summary of the Invention] The configuration of the present invention that achieves the above object includes a plurality of melting furnaces having both functions of preheating and melting raw materials,
The exhaust gas generated when melting raw materials in one melting furnace is introduced into another melting furnace for preheating, and when preheating and melting the raw materials are repeated alternately, the carbonaceous material is heated in oxygen in the first melting furnace. By injecting them together, these react to generate combustible gas, and the raw materials are melted by this reaction heat, and the resulting high-temperature combustible exhaust gas is used to preheat other raw materials to first recover sensible heat, and then, after sensible heat recovery, The low-temperature combustible exhaust gas is combusted to raise the temperature, and the high-temperature gas is used to preheat the raw materials in other melting furnaces and the heat is recovered, thereby melting the raw materials with almost no arc heating. The gist is:

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

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

As shown in the figure, this melting furnace equipment includes a plurality of (two in the illustrated example) melting furnaces, namely a first melting furnace 1 and a second melting furnace 2, and a raw material preheater that recovers sensible heat from high-temperature combustible gas generated during melting. 3 and a combustion tower 4 that burns the combustible gas after sensible heat recovery. Both of the melting furnaces 1 and 2 have the same structure, and both have the functions of melting and preheating raw materials. That is, the furnace lid 5,
Above the electrode 5 is an electrode 6 which can be inserted into and removed from the furnace.
6, and tap ports 7, 7 for taking out the generated molten steel and preheating gas inlet ports 8, 8 for introducing preheating gas into the furnace when the furnace is used as a preheater are formed on the bottom side wall. has been done. Further, at the bottom part 9 of the furnace, an inlet 10 is provided for blowing carbonaceous material such as pulverized coal into the furnace together with oxygen or air during melting.
10 is formed, and the furnace lids 5, 5 are provided with high-temperature gas discharge ports 11, 1 for discharging high-temperature exhaust gas during melting.
1 and low-temperature gas discharge ports 12, 12 for discharging low-temperature gas during preheating are formed.

In the figure, a solid line indicates a route in which the first melting furnace 1 is made to function for melting the raw material and a second melting furnace 2 is made to function in order to preheat the raw material, and a broken line indicates the reverse case.

High temperature gas discharge ports 11, 11 of both melting furnaces 1, 2
are high-temperature combustible gas passages 15 and 16 in which a first on-off valve 13 and a second on-off valve 14 are interposed, respectively.
are connected to the gas inlet 17 of the raw material preheater 3 via the respective gas inlet ports 17 of the raw material preheater 3. The gas outlet 18 of the raw material preheater 4 is connected to the gas inlet 19 of the combustion tower 4 via a passage 20, and a first on-off valve 22 and a second on-off valve 23 are interposed in the middle of the gas outlet 21, respectively. The melting furnaces 1 and 2 are connected to preheating gas inlets 8 and 8 of the first and second melting furnaces 1 and 2 via high-temperature exhaust gas passages 24 and 25, respectively.

The low temperature gas discharge ports 12, 12 of each furnace are connected to the gas inlet of the combustion air preheater 30 via low temperature gas passages 28, 29 in which a first on-off valve 26 and a second on-off valve 27 are interposed, respectively. 31, and this gas outlet 32 is connected to a post-dust collector 34 via an exhaust gas fan 33.

Further, a passage 36 is provided which communicates the air outlet 35 with the gas inlet 19 of the combustion tower 4 in order to introduce the combustion air preheated in the combustion air preheater 30 into the combustion tower 4. .

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

First, the feature of the method of the present invention is that when the raw material is melted in one melting furnace, the exhaust gas is used to preheat the raw material in the other melting furnaces, and this is repeated alternately. It is something to do.

First, in order to preheat the raw material in the second melting furnace 2 while melting the raw material in the first melting furnace 1, an exhaust gas path shown by a solid line in the figure is established. That is,
Open the first on-off valve 13 and close the second on-off valve 14 of the high-temperature combustible gas passages 15 and 16, close the first on-off valve 22 of the high-temperature exhaust gas passages 24 and 25, and open the second on-off valve 23. Furthermore, the first on-off valves 26 of the low-temperature gas passages 28 and 29 are closed, and the second on-off valves 27 are opened.

Once the exhaust gas route shown by the solid line has been established, operation will begin.

First, carbonaceous materials such as pulverized coal, char, coke, etc. are sucked into the first melting furnace 1 through an inlet 10 provided at the bottom of the furnace 1 along with oxygen or air. An initial molten steel is previously formed in the melting furnace 1 by arc heating or by leaving a small amount of molten steel produced in a previous process. The injected oxygen causes an exothermic reaction with carbon contained in the charged raw material, such as carbon in injected carbonaceous materials or pig iron, and generates combustible gases such as CO, H ₂ and hydrocarbons. The amount of heat generated at this time heats up the charged raw material and melts it. The generated high-temperature combustible gas is discharged from the high-temperature gas outlet 11 at around 600°C, passes through the high-temperature combustible gas passage 15, passes through the first on-off valve 13, and then passes through the raw material preheater 3.
introduced into the world. A raw material is charged in advance into the preheater 3, and this raw material is primarily preheated to 200 to 300°C using the above-mentioned high temperature combustible gas, and the sensible heat possessed by the exhaust gas is recovered. Note that the preheated raw materials are introduced into each melting furnace and melted. Preheater 3
The combustible gas after sensible heat recovery discharged from the gas outlet 18 is introduced into the combustion tower 4 through the passage 20, and this introduced combustible gas is used for combustion supplied from the combustion air preheater 30 side. It is combusted by air and becomes high-temperature exhaust gas at around 1000℃. At this time, the malodorous components conveyed together with the combustible gas from the raw material preheater 3 are thermally decomposed due to the high heat within the combustion tower 4 and become odorless.

This high-temperature exhaust gas is discharged from the gas outlet 21 of the combustion tower 4, flows through the high-temperature exhaust gas passage 25, and is introduced into the second melting furnace 2 via the second on-off valve 23 provided therein. In this second melting furnace 2, other raw materials are charged in advance, and this raw material is secondarily preheated by the above-mentioned high-temperature exhaust gas to recover heat from the melting furnace. In this case, the second melting furnace 2 does not function to melt the raw material, but functions as a preheater.
Furthermore, the high temperature exhaust gas is particularly high at about 1000°C, so the charged raw material is preheated to a high temperature of around 600 to 800°C. Further, the bad odor generated during this preheating is immediately thermally decomposed because the secondary preheating itself is carried out at a high temperature of 800° C. or higher.

Incidentally, at this time, it goes without saying that no carbonaceous material is injected into the second melting furnace 2.

The gas, which has undergone heat recovery and has become relatively low temperature, is discharged from the low temperature gas outlet 12 of the second melting furnace 2, flows through the low temperature gas passage 29, and is passed through the second on-off valve 27.
After passing through, the first on-off valve is closed, so the air is introduced into the combustion air preheater 30. Since this introduced exhaust gas is still at a high temperature compared to the outside temperature, the combustion air is preheated by the sensible heat possessed by this exhaust gas, and further heat is recovered. The preheated combustion air is passed through the passage 36 to the combustion tower 4 as described above.
combustible gas and contributes to the combustion of combustible gas.

On the other hand, the exhaust gas discharged from the combustion air preheater 30 passes through an exhaust gas fan 33 and a dust collector 34, and then is released into the atmosphere.

In this way, while melting the raw material in the first melting furnace 1, melting is performed in the raw material preheater 3 and the second melting furnace 2.
When the melting work in the first melting furnace is completed by performing the next preheating and the second preheating, the molten steel is transferred to the tapping port 7.
Take it out.

Then, the raw material preheated in the raw material preheater 3 and new raw materials are charged into the empty first melting furnace 1, and the first melting furnace 1 is made to function for preheating the raw materials in the opposite manner to the above method. , the second melting furnace 2 is operated to melt the raw material. That is, the exhaust gas path shown by the broken line in the figure is established. To this end, contrary to the above method, the first on-off valves 13 of the high-temperature heating gas passages 15 and 16 are closed;
The second on-off valve 14 is opened, and the high-temperature exhaust gas passage 24,
The first on-off valve 22 of 25 is opened and the second on-off valve 23 is closed, and the first on-off valve 26 of low-temperature gas passages 28 and 29 is opened and the second on-off valve 27 is closed. The operation in this case is the same except that the functions of the first melting furnace 1 and the second melting furnace 2 are alternated, so a description thereof will be omitted.

In this way, in the present invention, a plurality of (two) melting furnaces 1 and 2 having both melting and preheating functions are made to alternately repeat melting and preheating, so that melting occurs when one melting furnace melts. In a melting method in which exhaust gas is used to preheat the raw material charged into the other melting furnace, carbon material is injected during the melting of the raw material in the first melting furnace to cause a combustible gas generation reaction, and the reaction heat is used to generate a combustible gas. It is obtained by melting raw materials and introducing the resulting high-temperature combustible gas into the raw material preheater 3 to preheat other raw materials, first recovering sensible heat, and then combusting the combustible gas after recovering the sensible heat. By introducing high-temperature exhaust gas into another melting furnace, the raw materials charged therein are preheated to a high temperature and the heat is recovered, so arc heating is not necessary or can be used throughout the entire process. However, it is only necessary to generate the initial molten steel, and power consumption can be significantly reduced.

Specifically, in the past, depending on the size of the melting furnace, electric energy of 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, resulting in significant power savings.

In addition, since two-stage heat recovery is performed by recovering sensible heat and recovering heat from the exhaust gas generated when melting raw materials, conventionally the amount of heat recovered was 30 to 50 KWH/T, but with the method of the present invention, the amount of heat recovered was 30 to 50 KWH/T. 70～100KWH/T
The amount of heat recovery can be improved.

Furthermore, the raw materials that have been preheated to a high temperature in each of the melting furnaces 1 and 2 are melted as they are without being transferred elsewhere, so that the handling of the raw materials can be greatly simplified.

Although the above embodiment has been described with reference to the case where two melting furnaces are provided, it is needless to say that the number is not limited to that number.

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

(1) By injecting carbonaceous materials into a reaction to produce combustible gas, the raw material is melted by the heat of reaction, and sensible heat and heat from the resulting high-temperature combustible gas are recovered, significantly reducing power consumption compared to conventional methods. can be reduced to

(2) Malodorous components generated during low-temperature preheating in the raw material preheater can be thermally decomposed by the high-temperature exhaust gas generated during combustion of combustible gas in the combustion tower, making it possible to prevent malodor pollution.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing melting furnace equipment for carrying out the method of the present invention. In the figure, 1 and 2 are the melting furnace, 3 is the raw material preheater, and 4 is the melting furnace.
10 is a combustion tower, 10 is a carbon material inlet, and 30 is a combustion air preheater.

Claims (1)

[Claims] 1 Equipped with multiple melting furnaces that have the functions of both preheating and melting raw materials such as scrap, the exhaust gas generated during melting of raw materials in one melting furnace is introduced into the other melting furnaces for preheating, and is used to preheat and melt raw materials. When melting and melting are repeated alternately, the carbonaceous material is subjected to a combustible gas generation reaction in the presence of oxygen-containing gas in the first melting furnace, the raw material is melted by the heat of reaction, and the resulting high temperature combustible gas is used to melt other materials. The feature is that the raw material is preheated to recover sensible heat, and then the combustible gas after the sensible heat recovery is combusted, and the generated high temperature exhaust gas is used to preheat the raw materials in other melting furnaces and the sensible heat is recovered. How to dissolve scraps, etc.