JPH09263812A - Operation of vertical type scrap melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the solution loss and to reduce the unit requirement of carbonaceous material by previously coating the charging carbonaceous material with a material hardly being oxidized with high-temp. CO2 and H2 O and capable of being eliminated by burning, vaporizing or melting at the lower part of a melting furnace at the time of melting scrap. SOLUTION: At the time of charging the carbonaceous material 2 into a vertical type scrap melting furnace provided with multi-step type blasting tuyeres 4-6 at the lower part of the furnace, the carbonaceous material 2 and iron source 3 are separated from each other in the cross sectional plane of the furnace. At the same time, the carbonaceous material 2 covered with one or more kinds of compounds selected from group consisting of oxides, carboxides, hydroxides and sulfides of alkali metals or alkaline-earth metals or with an ore containing these compounds on this surface is used. As the carbonaceous material to be used, lump coal or formed coal of fine coal and granular coal is used, and the surface coating material is applied spreading the slurry of the powdery and granular material thereof or by being dipped into the slurry.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when producing hot metal from scrap and carbon materials as raw materials, controls the distribution of the contents of the furnace interior of these materials, coats the carbon materials and suppresses the solution reaction, and The present invention relates to a method for operating a vertical scrap melting furnace that reduces the unit.

[0002]

2. Description of the Related Art A vertical scrap melting furnace represented by cupola is a cylindrical furnace having a relatively simple structure, and an iron source and a carbonaceous material such as coke are charged from the upper side of the furnace and the iron is charged. The source always descends while being in contact with the carbonaceous material, and is preheated and melted by the heat of combustion reaction between oxygen in the air sent from the tuyere installed in the lower part of the furnace and carbon in the coke.

At the tuyere, C in the carbonaceous material reacts with O _{2 in} the air blown from the tuyere according to the following formula to produce CO ₂ . This reaction is exothermic. C + O ₂ = CO ₂ +97,000 kcal / kmol
・ C The CO ₂ produced by this reaction rises in the furnace while exchanging heat with the iron source and the carbonaceous material falling from above the furnace. At that time, it is called the solution loss reaction with the carbonaceous material. An endothermic reaction occurred, which made the energy efficiency of the cupola poor.

C + CO ₂ = 2CO-38200kc
al / kmol C

[0005]

Therefore, in order to improve the energy efficiency of cupola, how to suppress this solution loss reaction is an important issue. As a conventional technique to solve this problem,
For example, in the invention described in Japanese Patent Laid-Open No. 7-70625, coke is charged in the peripheral portion of the furnace wall, an iron source is charged in the central portion of the furnace, and CO ₂ rising in the furnace is contacted with carbonaceous material as much as possible. It is disclosed that the solution loss reaction is reduced by utilizing it for heat exchange with the iron source without performing it.

However, when this conventional technique was applied to an actual operation, it was found that the following problems were still present.
In other words, considering the stable drop of the carbonaceous material itself and the loss into the exhaust gas, it is not preferable to use a remarkably fine carbonaceous material that makes the air permeability of the carbonaceous material portion practically zero, and the carbonaceous material has a certain size. The use of carbonaceous material with a grain size is inevitable. This causes gas to wrap around to the carbonaceous material side, and as a result,
The result is that the solution loss reaction cannot be suppressed sufficiently. Then, once solutions the loss reaction occurs, since the gap for carbonaceous material volume to the combustion is contracted by CO ₂ gas is increased ventilation resistance of the CO ₂ gas becomes smaller, more CO ₂ gas carbonaceous material filled As a result, the solution loss reaction that wraps around to the department side is promoted, and the above-mentioned problems have not been solved.

On the other hand, the inventors of the present invention previously disclosed in Japanese Patent Laid-Open No. 8-13
In Japanese Patent No. 015, the surface of the carbonaceous material is previously subjected to high temperature CO ₂
Disclosed is a technique for preventing a solution loss reaction in the upper part of the melting furnace by coating with a substance that is hard to be oxidized by H ₂ O and H ₂ O and is burned down by burning, evaporation, melting, etc. in the lower part of the melting furnace. In this conventional technique, when the height of the charge is increased to increase productivity, or when a heavy scrap to be charged is charged as a raw material, the carbon material itself is worn or crushed due to abrasion or crushing of the carbon material. The surface of was exposed, and the problem of a solution loss reaction occurred starting from the exposed part.

The present invention solves the above problems of the prior art, uses the combustion energy of the carbonaceous material to the maximum extent, and reduces the carbonaceous material unit required for melting the iron source to a large extent. A method for operating a melting furnace is provided.

[0009]

As a result of the examination of the reduction of the amount of heat source (carbonaceous material) used in the operation method of the vertical scrap melting furnace, the present invention makes CO gas generated at the primary tuyere an exothermic reaction. CO + (1/2) O ₂ → CO ₂ burns CO ₂ to completely exhaust the energy of the carbonaceous material in the furnace, and CO ₂ gas generated by this reaction causes CO ₂ + C → We have developed and completed a technology that simultaneously achieves both suppression of the endothermic reaction of 2CO 2. That is, as a method of suppressing the above endothermic reaction, cross-sectional views of the furnace are schematically shown in FIGS.
As shown in FIG. 5, the charging method was such that the iron source and the carbonaceous material were distributed separately from each other in the cross section of the furnace, and as shown in FIG. 1, the multi-stage tuyere provided in the height direction of the furnace wall. Is used to ensure that secondary combustion is completely performed.

According to the present invention, when a vertical scrap smelting furnace is provided in the lower part of the furnace with a large number of blast tuyere, the scrap is melted to produce hot metal or molten steel, a carbon material and an iron source are cross-sectioned in the furnace. Separately from each other and charged, the carbonaceous material is
Vertical scrap melting characterized by using a material whose surface is preliminarily coated with a substance which is hard to be oxidized by high temperature CO ₂ or H ₂ O and which disappears by burning, evaporation or melting in the lower part of the vertical scrap melting furnace. This is the operating method of the furnace.

That is, according to the present invention, one of the carbonaceous material and the iron source is charged into the central portion of the furnace and the other is charged into the furnace mold side separately from each other, and the carbonaceous material is hardly oxidized. Moreover, the surface is previously coated with a substance that disappears in the lower part of the melting furnace. In this case, it is preferable that the oxygen-enriched air is blown from the tuyeres of the plurality of stages to enable more efficient operation.

As the substance for coating the surface of the carbonaceous material, oxides or carbonates of alkali metals or alkaline earth metals,
It is preferable to use any one or more selected from the group consisting of hydroxides and sulfides, or those composed of minerals containing these. Then, as a method of applying a substance for coating the surface of these carbonaceous materials, a powdery or granular material of the substance is slurried using a liquid medium and then a slurry is applied to the surface of the carbonaceous material, or the slurry is applied. The carbonaceous material may be dipped into the surface of the carbonaceous material for application.

Further, in the above operating method, when the carbonaceous material used is agglomerated coal, or formed coal formed by molding powder or granular coal, it can be operated at a lower cost than coke.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The technique of the present invention realizes improvement of thermal efficiency by suppressing an endothermic reaction between carbon in carbonaceous material and CO ₂ gas contained in high-temperature exhaust gas that occurs in a vertical furnace. That is, C + O ₂ → CO ₂ reaction occurs due to the air sent from the tuyere installed in the lower part of the vertical furnace, and CO ₂ gas rises inside the furnace and is discharged outside the furnace. It comes into contact with the carbonaceous material in the bed and causes a reaction of carbon in the carbonaceous material and CO ₂ + C → 2CO. This reaction is an endothermic reaction, and in the entire furnace, only the CO content in the gas discharged to the outside of the furnace is discarded as a latent heat content, and the consumption of carbonaceous materials increases.

FIG. 1 is a schematic vertical sectional view of a vertical scrap melting furnace in which the present invention can be preferably implemented. Scrap 2, which is a charging raw material, is charged from a scrap charging point at the top of the iron source charging pipe 9, and coke as the carbonaceous material 3 and limestone as an auxiliary raw material are charged at the top of the carbonaceous charging pipe 8. Charge into the melting furnace shaft portion 1 from the coke charging position. Air is blown from the primary tuyere 4 installed at the bottom of the melting furnace shaft portion 1, and is blown from the secondary tuyere 5 and the third tuyere 6,
Accurately perform secondary combustion. By this secondary combustion, the scrap 2 is preheated, the charging raw material is continuously charged, and the molten pig iron 11 is obtained in the ladle 12 by melting.

Therefore, in order to completely use up the energy of the carbonaceous material 3 in the furnace, as a method of suppressing the above-mentioned endothermic reaction, a method of charging the scrap 2 and the carbonaceous material 3 in the vertical furnace, Attention was paid to coating the surface of No. 3. That is, as shown in FIGS. 2 to 5, the scrap 2 and the carbonaceous material 3 in the vertical furnace cross section are charged so that the scrap 2 and the carbonaceous material 3 are separated and distributed in the cross section of the furnace. . FIG.
5 is a schematic view of a cross-sectional view taken along the line AA of FIG. In FIG. 2, an iron source (scrap) 2 is charged on the furnace peripheral side of the melting furnace shaft portion 1, and a carbonaceous material 3 is charged on the center side. In FIG. 3, conversely, an iron source (scrap) 2 is charged on the center side and a furnace material 3 is charged on the furnace peripheral side. In FIG. 4, the carbonaceous material 3 is charged discontinuously in the circumferential direction on the furnace circumference side, and the iron source (scrap) 2 is charged between the center side and the furnace circumference. In FIG. 5, the distribution of the iron source and the carbonaceous material is exactly the opposite of that in FIG.

In the charging shown in FIGS. 2 to 5, the cross-sectional area of the carbonaceous material 3 portion is reduced, and the ventilation resistance of the carbonaceous material 3 portion is larger than that of the scrap 2 portion. It is possible to significantly reduce the ventilation gas flow rate of the part. Further, by coating the surface of the carbonaceous material 3 such as coke or coal with NaCO ₃ which is a carbonate of an alkali metal or CaO which is an oxide of an alkaline earth metal, CO _{2 in} the middle and upper parts of the furnace The solution loss reaction between the carbonaceous material 3 and the carbonaceous material 3 can be reduced.

Under these conditions, as shown in FIG. 1, a large number of tuyeres 5, 6 are provided on the upper portion of the bed coke and further on the upper portion thereof.
The secondary combustion can be improved and the temperature distribution in the height direction of the charged material packed bed can be properly controlled by installing the, so that optimum preheating that does not cause fusion of the scrap 2 can be performed. It can be carried out. That is, by improving the charging method and the operating method as described above, the reaction amount of the carbonaceous material and CO ₂ gas can be reduced, the secondary combustion can be improved, and the energy of the carbonaceous material can be effectively used. It can be used for preheating and melting scrap.

The surface coating material of the carbonaceous material used in the present invention includes limestone (CaCO ₃ is the same as the main component hereinafter), quick lime (CaO), slaked lime (Ca (OH) ₂ ), gypsum (CaS).
O ₄ ), dolomite (MgCO ₃ · CaCO ₃ ), calcined dolomite (MgO · CaO), soda ash (Na ₂ CO)
₃ ), barium carbonate, barium sulfate and the like. However, as a selection condition for these, it is necessary not to melt or corrode the refractory and the steel structure (metals of the raw material charging part) that constitute the furnace wall. In addition, limestone is added as a slag aid in the ordinary cupola operation, but in the case of the present invention, it is desirable to use a material having a slag action similar to this function. On the other hand, as the coating method, it is also possible to simply "spray" the powdery surface coating material on the carbon material, but in order to enhance the coating effect, the powdery material is treated with a liquid medium such as water, oil or an organic solvent. It is desirable to form a slurry and apply it by spraying it on a carbonaceous material or by immersing the carbonaceous material in a slurry-like bath.

Further, as the carbonaceous material used, ordinary coke for foundry may be used, but more economical blast furnace coke, or so-called formed coal obtained by agglomerating agglomerated coal or powder / granular coal can also be used. is there. Especially when using coal, if a brand with a large amount of volatiles is used, a large amount of gas is generated when it is heated in the furnace, which may destroy the coating layer on the surface of the carbonaceous material or cause the collapse of the lump itself. Be careful because it exists.

[0021]

【Example】

(Embodiment 1) As one embodiment of the present invention, a cupola having a capacity of 3 t / h is used as a vertical melting furnace for 100 t.
Was dissolved. The scrap used in this example was shredder scrap having a size of 25 to 150 mm, and blast furnace coke having a size of 30 to 75 mm coated with quicklime was used as a carbonaceous material. The coating is 25 g of quicklime powder on 100 g of water on the surface of the coke.
Quick lime powder was mixed at a rate of 0 g using a kneader, and the prepared solution (slurry) was applied. The total amount of quick lime charged including this quick lime applied is 120 kg, which is the same as the conventional one.
/ Hr. The inner diameter of the melting furnace shaft portion 1 is 6
00 mm. As for the operating conditions, as shown in Fig. 2, the charging of scrap and coke into the cupola is shown in Fig. 2. In the cross section of the cupola, the coke is charged in the center of the furnace and the scrap is charged in the vicinity of the furnace wall. ℃,
The amount of coke charged on the surface was adjusted from the furnace top so that the carbon concentration in the hot metal was 3.5 ± 0.5%. Meanwhile blowing amount from the primary tuyeres 4, from 1400Nm ³ / hr, 2 tuyeres 5, from 300 Nm ³ / hr, 3 tuyeres 6 10
It was supplied at a rate of 0 Nm ³ / hr. As a result of the operation in Example 1 above, the coke basic unit was 92 kg / t.

(Example 2) As Example 2, the same equipment as in Example 1 above was used, and the operating conditions were as follows: the distribution of the scrap and the coke charged on the surface of the cupola was as shown in FIG. Similar results were obtained by charging as shown in FIGS. 4 and 5. (Example-3) Oxygen was enriched from the multi-tuyer. The operating conditions are as follows: an iron source and carbonaceous material are charged so as to have the distribution shown in FIG. 2, and the air flow rate is 1400 Nm ³ / h from the primary tuyere 4.
r, 2 tuyeres 200Nm air from 5 ³ / hr, the air oxygen from 15Nm ³ / hr, ³ tuyeres 6 80 Nm
³ / hr and oxygen were supplied at a ratio of 10 Nm ³ / hr.
As a result of the operation, the basic unit of coke was 89 kg / t.

(Embodiment 4) Using the same equipment as in Embodiment 1, the operating conditions are shown in FIG. 3, FIG. 4 and FIG. 5 as the distribution of the charge of scrap and the coke coated on the surface of the cupola. As described above, the blowing rate was the same as in Example-3, and similar results were obtained. Table 1 shows the operating conditions.

(Comparative Example-1) In a cupola operation of a conventional method, a scrap tube and a coke tube were charged into the furnace in a layered manner from the iron source charging tube without using a carbon material charging tube. , The dissolution capacity is 3t / h, the production amount is 1 as in Example 1.
It was operated as 00t. The scrap and carbon materials used are the same in size and type as those used in Example-1, and the obtained hot metal temperature is 1540 ± 10 ° C. under the condition of the amount of quicklime to be charged of 120 kg / hr. The amount of coke charged from the furnace top was adjusted so that the medium carbon concentration was 3.5 ± 0.5%. The operating conditions are also shown in Table 1. As a result of the operation in Comparative Example 1 above, the coke basic unit is 140 k.
It became g / t.

(Comparative Example 2) In Comparative Example 1, 250 g of quicklime powder was added to 100 g of water on the surface of the charging coke.
As a result of using the coke coated with the solution prepared by mixing the quicklime powder at a ratio of 1 using a kneader, the coke basic unit was 126 kg / t. (Comparative Example-3) The same equipment as that of the conventional Japanese Patent Publication No. 1-501401 was used, and the dissolving capacity was 3 t / h and the production amount was 100 t, as in Example 1. Scrap size is 25 to 150 mm, carbon material size is 30 to 7
5 mm. As a result, the basic unit of coke is 130 kg.
Was / t. Next, in terms of operation, 3 per day
In contrast to the case of hanging the rack up to 4 times, the present invention was able to perform the operation smoothly without hanging the rack.

(Comparative Example 4) Conventional Japanese Patent Laid-Open No. 7-7062
As a result of operating in the same manner as in Comparative Example 3 using the same equipment as the apparatus described in Japanese Patent Publication No. 5, the coke unit was 110 kg / t. Next, in operation, the hanging at the protruding portion of the multi-stage tuyere occurred 2-3 times in the operation per day.

Table 1 shows the coke basic units of the above Examples and Comparative Examples. As is apparent from Table 1, the conventional unit of coke is 110 to 140 k with respect to the hot metal production amount.
g / ton, according to the invention 85-95 kg
It has become possible to melt scrap in an epoch-making unit of low carbonaceous material.

[0028]

[Table 1]

[0029]

EFFECTS OF THE INVENTION According to the present invention, in the charge distribution control charging of the iron source and the carbonaceous material in the transverse section of the vertical scrap melting furnace,
It is possible to coat the surface of carbon materials such as coke and coal, suppress the solution loss reaction in the furnace, improve secondary combustion with multi-stage tuyere, and control the temperature distribution of scrap in the height direction. , The energy of the carbonaceous material was completely used up in the furnace, and the energy efficiency was improved, that is, the unit consumption of carbonaceous material was greatly reduced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a vertical scrap melting furnace used for carrying out the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, showing an example of the radial distribution of the charged iron source and carbonaceous material in the vertical furnace.

FIG. 3 is a cross-sectional view taken along the line AA of FIG. 1, showing an example of the radial distribution of the charged iron source and carbonaceous material in the vertical furnace.

FIG. 4 is a cross-sectional view taken along the line AA of FIG. 1, showing an example of the radial distribution state of the charged iron source and carbonaceous material in the vertical furnace.

5 is a cross-sectional view taken along the line AA in FIG. 1, showing an example of the radial distribution of the charged iron source and carbonaceous material in the vertical furnace.

[Explanation of symbols]

1 Melting furnace shaft part 2 Scrap (iron source) 3 Carbon material (coke) 4 Primary tuyere 5 Secondary tuyere 6 Tertiary tuyere 7 Molten iron take-out port 8 Charcoal material loading pipe 9 Iron source loading Inlet pipe 10 Exhaust gas 11 Hot metal 12 Ladle 13 Vertical shaft

Claims (5)

[Claims] 1. A method for melting scrap by using a vertical scrap melting furnace having a multi-stage blower tuyere at the bottom of the furnace to produce hot metal or molten steel, a carbonaceous material and an iron source within the cross section of the furnace. The carbonaceous materials are charged separately from each other, and
A vertical scrap melting furnace characterized in that the surface of the vertical scrap melting furnace is preliminarily coated with a substance that is not easily oxidized by O ₂ or H ₂ O and disappears by combustion, evaporation or melting in the lower part of the vertical scrap melting furnace. Operating method. 2. The method for operating a vertical scrap melting furnace according to claim 1, wherein oxygen-enriched air is blown from the multi-stage blowing tuyere. 3. A material for coating the surface of the carbonaceous material, which is selected from the group consisting of oxides, carbonates, hydroxides and sulfides of alkali metals or alkaline earth metals, or a combination thereof. The method for operating a vertical scrap melting furnace according to claim 1, wherein the operating method is a mineral containing iron. 4. A method of applying a substance for coating the surface of a carbonaceous material, which comprises pulverizing a powder or granular material of the substance using a liquid medium and then spraying the slurry on the surface of the carbonaceous material, or The method for operating a vertical scrap melting furnace according to claim 1 or 2, wherein the carbonaceous material is applied to the surface of the carbonaceous material by immersing the carbonaceous material in the slurry. 5. The operating method of a vertical scrap melting furnace according to claim 1, wherein the carbonaceous material used is agglomerated coal, or coal formed by molding powder or granular coal. .