JP2014105370A - Method for producing molten iron using vertical scrap melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing molten iron using a vertical scrap melting furnace, reducing a coke ratio without requiring remarkable equipment reconstruction and without exerting influence on molten iron quality, further improving gas permeability, and capable of realizing high productivity.SOLUTION: In the method for producing molten iron using a vertical scrap melting furnace, large and small sieve meshes A, B (large sieve meshes A, small sieve meshes B) are used, and the sieving of coke is performed in such a manner that a sieve mesh ratio A/B≤1.7 is satisfied to uniformize coke particle size, thus the porosity of a coke packing layer is increased, solution loss reaction is suppressed, and a coke ratio is reduced.

Description

  The present invention is a method for producing hot metal by melting iron-based scrap by the combustion heat of coke using a vertical scrap melting furnace, and in particular, producing hot metal stably with a low coke ratio and high productivity. For the method.

  There is a cupola method as a scrap melting process in a vertical furnace. In this cupola method, scrap and coke are charged in layers or mixed from the top of the furnace, hot air is blown from a plurality of tuyere at the bottom of the furnace, and the scrap is melted by the combustion heat of the coke to produce hot metal. It is a technique to do.

  In the cupola method, large-diameter coke having a particle diameter of 150 mm or more called coke for casting is used as coke. However, since coke for casting is very expensive, operation using blast furnace coke that is small and inexpensive in recent years. Has also been done.

The hot metal production method using blast furnace coke has the advantage of lower cost compared to casting coke, but on the other hand, it has a large specific surface area due to its small diameter, and the solution loss reaction shown in the following equation in the furnace There is a problem that is likely to occur. Since this solution loss reaction is an endothermic reaction, the coke ratio generally tends to be higher than when casting coke is used.
C + CO ₂ → 2CO

  In order to reduce the coke ratio in a vertical scrap melting furnace, it is important to reduce the amount of solution loss reaction. As a technique to reduce the amount of solution loss reaction, a method of coating the coke surface with an inert substance ( Patent Document 1), a method of charging coke and scrap separately in the furnace radial direction (Patent Document 2), a method of charging refractory bricks together with coke (Patent Document 3), and the like.

Japanese Patent Laid-Open No. 8-13015 JP-A-8-67907 JP 2009-52074 A

  However, Patent Documents 1 to 3 have the following problems.

  First, the method of Patent Document 1 is a technique for suppressing the solution loss reaction by coating the coke surface with an inert substance so as to contact the gas, but the coating equipment is incorporated into the raw material transport system. There is a problem that it is necessary to introduce and remodel the equipment and to procure the covering material. There is also a problem that the components of the coating material dissolve into the hot metal in the lower part of the furnace, and the impurity concentration in the hot metal increases.

  In addition, the method of Patent Document 2 uses the fact that scrap and coke are charged separately in the radial direction of the furnace, and gas passes preferentially through a highly breathable scrap layer compared to the coke layer, This technology reduces the amount of gas flowing through the coke layer and reduces the solution loss reaction. However, in order to charge scrap and coke separately in the radial direction, significant modifications to the furnace top charging equipment are required. . Further, when the scrap is softened at high temperature, since coke as a spacer does not exist, there is a possibility that it may be fused to cause deterioration of air permeability, resulting in unstable operation.

  In addition, the method of Patent Document 3 is a technique for reducing the solution loss reaction by reducing the proportion of coke present in the lower part of the furnace by charging a refractory brick mass together with coke into the furnace. Need to be newly established. Further, since it is necessary to reduce the number of times of charging scraps or coke, or the amount of charging, the amount of charging the refractory brick blocks, a decrease in productivity becomes a problem. There are also problems such as an increase in the amount of slag, basicity adjustment due to a change in slag viscosity, and an increase in impurities in the hot metal. Furthermore, when there is a difference in the particle size between the refractory brick block and the coke, the porosity is lowered, leading to deterioration of the air permeability in the furnace.

  Therefore, the object of the present invention is to solve the above-mentioned problems, do not require major equipment modification, reduce the coke ratio without affecting the hot metal quality, and further improve the air permeability and increase the productivity. Is to provide a hot metal production method using a vertical scrap melting furnace.

In order to solve the above problems, the present invention has the following features: [1] In a vertical scrap melting furnace, iron-based scrap and coke are charged as main furnace charging materials from the top of the furnace. , A method of producing hot metal by blowing hot air from a plurality of tuyere provided in the lower part of the furnace and melting iron-based scrap with the combustion heat of coke,
The coke is obtained by sieving through a two-stage sieve having different sieves, which are a large sieve A and a small sieve B, on the sieve of the large sieve A and the sieve of the small sieve B,
A hot metal production method using a vertical scrap melting furnace characterized by being coke having a particle size satisfying the following formula (1).
A / B ≦ 1.7 (1)

  [2] The hot metal production method using the vertical scrap melting furnace according to [1], wherein the small sieve mesh B is 20 mm or more.

  [3] The hot metal production method using the vertical scrap melting furnace according to [2], wherein the small sieve mesh B is 25 mm or more.

  [4] The hot metal production method using the vertical scrap melting furnace according to any one of [1] to [3], wherein the large sieve mesh A is 80 mm or less.

  [5] The hot metal production method using the vertical scrap melting furnace according to [4], wherein the large sieve mesh A is 60 mm or less.

  [6] The coke is a coke having a grain size in each section obtained by sieving with three or more sieves having different mesh sizes, and the coke having a grain size in each section is separately charged into the vertical scrap melting furnace. A hot metal production method using the vertical scrap melting furnace according to the above [1].

  In the present invention, a vertical scrap melting furnace is used that does not require significant equipment modification, reduces the coke ratio without affecting the hot metal quality, and further improves air permeability to achieve high productivity. A hot metal production method can be provided.

  That is, according to the present invention, by controlling the particle size of the coke charged into the vertical scrap melting furnace more uniformly, the porosity in the coke packed bed at the lower part of the furnace is increased, and the gas flow rate in the same region is decreased. By doing so, the solution loss reaction is suppressed. Since the solution loss reaction is an endothermic reaction, being suppressed, energy loss in the furnace is reduced, and the coke ratio can be reduced. Further, the increase in the porosity improves the air permeability in the furnace, so that the operation can be stabilized and the productivity can be improved.

The schematic diagram which shows the vertical scrap melting furnace used by this invention, and its operation form. The figure which shows the relationship between sieve ratio A / B, solution loss reaction rate, and the porosity.

  The present invention suppresses the solution loss reaction by increasing the porosity of the coke packed bed at the bottom of the furnace and decreasing the gas flow rate by uniformly controlling the particle size of the charged coke in the vertical scrap melting furnace. This is a hot metal manufacturing method.

  FIG. 1 is a schematic diagram showing an example of a vertical scrap melting furnace used in the present invention and an operation mode thereof. As shown in FIG. 1, in the vertical scrap melting furnace 1, iron-based scrap 2 and coke 3 are charged from the furnace top charging inlet 7, blown air 5 is blown from the blower tuyere 4, and hot metal is discharged from the tapper 8. 9 out. In addition, 6 in FIG. 1 is exhaust gas.

  In such a vertical scrap melting furnace 1, the solution loss reaction mainly occurs in the region from the blower tuyere 4 to the upper surface of the coke packed bed. This region coincides with a region of 1500 ° C. or higher which is the melting temperature of scrap 2. Since the solution loss reaction is film diffusion controlled at 1500 ° C. or higher, the reaction rate increases as the gas flow rate increases. Moreover, the amount of reaction increases as the number of coke per unit layer volume increases. Since the gas flow rate and the number of cokes per unit layer volume decrease as the porosity of the coke packed layer increases, the solution loss reaction can be suppressed by increasing the porosity of the coke packed layer.

  Therefore, in the present invention, coke sieving is performed using large and small sieves A and B (large sieve A and small sieve B) so as to satisfy sieve ratio A / B ≦ 1.7. In this way, the coke particle size is made uniform, thereby increasing the porosity of the coke packed bed, suppressing the solution loss reaction, and reducing the coke ratio.

  In FIG. 2, the sieve ratios A and B are adjusted by changing the sieve meshes A and B so that the average value (A + B) / 2 of the sieve meshes A and B is 40 mm. Filling the above coke and measuring the porosity of the coke packed bed (simply described as “porosity” in FIG. 2) and the solution loss reaction rate (simply described as “reaction rate” in FIG. 2) Show.

The solution loss reaction rate was determined by filling the vertical scrap melting furnace 1 with 1 kg of coke sieved with each of A and B sieves, and reacting with CO ₂ / N ₂ (= 30/70) mixed gas. It measured from the weight change at the time.

  As shown in FIG. 2, when the sieve ratio A / B ≦ 1.7, the porosity of the coke packed bed increases rapidly, and the solution loss reaction rate is effectively suppressed. That is, by adjusting the particle size of the coke with a sieve that satisfies the sieve ratio A / B ≦ 1.7 (that is, the coke that has become the sieve under the large sieve A and the sieve with the small sieve B is charged. It can be seen that the coke ratio in the vertical scrap melting furnace can be reduced.

  At that time, the coke used in the present invention is more effective when using coke for blast furnace that has a particle size of 80 mm or less and easily causes a solution loss reaction than a coke for castings that has a large particle size and does not easily cause a solution loss reaction. Demonstrate. Therefore, it is preferable that the large mesh A is 80 mm or less. Furthermore, it is more preferable that the large sieve mesh A is 60 mm or less.

  On the other hand, if the particle size of the coke becomes too small, the porosity of the coke packed layer tends to decrease, so the small sieve mesh B is preferably 20 mm or more. Furthermore, it is more preferable that the small sieve mesh B is 25 mm or more.

  And the large sieve A and the small sieve B which did not become the sieve of the large sieve A and the sieve of the small sieve B can be used in a blast furnace or the like, Using three or more stages of sieves with different sieve meshes, coke that has been sieved to satisfy the sieve ratio A / B ≦ 1.7 in each section (between the front and rear sieves) is shifted in time so as not to mix. By charging the mold scrap melting furnace, it can be used in the vertical scrap melting furnace, and even in such a method, the coke ratio can be reduced compared to charging coke mixed with various grain sizes. Can do.

  In addition, as mentioned above, when using the sieve of 3 steps | paragraphs or more which differ in a mesh size, it is preferable to make it the largest mesh size into 80 mm or less. Furthermore, it is more preferable that the maximum sieve mesh be 60 mm or less. Similarly, it is preferable that the minimum sieve mesh is 20 mm or more. Furthermore, it is more preferable that the minimum sieve mesh is 25 mm or more.

  In this way, the coke ratio is reduced, and the air permeability in the furnace is improved by increasing the porosity of the coke packed bed, so that a coke having a smaller particle size can be used, thereby reducing the cost. Take it. In addition to improving productivity by utilizing the ventilation capacity, it is also possible to reduce manufacturing costs by using low-grade raw materials.

  In addition, the present invention can be carried out only by sieving the coke to be used, and if the sieving device is installed, it is not particularly necessary to modify the existing equipment, and therefore can be easily carried out.

  As an example of the present invention, a hot metal 9 was manufactured using the vertical scrap melting furnace 1 shown in FIG. The vertical scrap melting furnace 1 had an inner diameter of 3.4 m, and the furnace height direction distance from the tuyere 4 to the stock line was 8 m.

  In this example, H2 was used as the iron scrap. Similar results were obtained even when scraps other than H2 (HS, H1, H3, H4) were used. Incidentally, H1 to H4 and HS are scrap types (heavy scraps) standardized by the Japan Iron Source Association and Iron Scrap Inspection Standard.

  Table 1 shows the operation specifications and results of the examples (Examples 1 to 3) of the present invention. In addition, t described in Table 1 indicates the generated hot metal ton.

Example 1
In Invention Example 1, a two-stage sieve having a sieve mesh of 40 mm and a sieve mesh of 60 mm is used so that the sieve ratio A / B ≦ 1.7 is satisfied. That is, in Example 1 of the present invention, the large sieve mesh A = 60 mm and the small sieve mesh B = 40 mm (sieving ratio A / B = 1.5).

  Then, the coke obtained as the sieve under the large sieve A and the sieve with the small sieve B was charged into the vertical scrap melting furnace 1.

  As a result, in Example 1 of the present invention, the coke ratio was 215 kg / t, and as in Comparative Example 1, the average particle size was equal to the particle size of 35 to 65 mm (screen ratio A / B = 1.85). The coke ratio is reduced by 8 kg compared to the coke ratio of 223 kg / t when the wide coke is charged.

(Example 2)
Example 2 of the present invention uses a three-stage sieve having a mesh size of 60 mm, a mesh size of 40 mm, and a mesh size of 25 mm so that the mesh ratio A / B ≦ 1.7 is satisfied for each section. That is, in Example 2, the section 1 has a large sieve A = 60 mm and a small sieve B = 40 mm (screen ratio A / B = 1.5), and the section 2 has a large sieve A = 40 mm. The small mesh B = 25 mm (mesh ratio A / B = 1.6).

  Then, the coke obtained as the sieve under the large sieve A and the sieve with the small sieve B was charged into the vertical scrap melting furnace 1 for each of the sections 1 and 2.

  As a result, in Example 2 of the present invention, the coke ratio for each of sections 1 and 2 was 215 kg / t and 233 kg / t, and the average coke ratio was 224 kg / t. The coke ratio is reduced by 6 kg as compared with the coke ratio of 230 kg / t when the coke having the sieve ratio A / B = 2.4 is charged as it is.

(Example 3)
Example 3 of the present invention uses a four-stage sieve having a mesh size of 70 mm, a mesh size of 45 mm, a mesh size of 30 mm, and a mesh size of 20 mm. Is. That is, in Example 3 of the present invention, in section 1, large sieve A = 70 mm and small sieve B = 45 mm (screen ratio A / B = 1.56), and in section 2, large sieve A = 45 mm. , Small mesh B = 30 mm (sieving ratio A / B = 1.5), and in section 3, large mesh A = 30 mm, small mesh B = 20 mm (sieving ratio A / B = 1.5) It has become.

  Then, in each of the sections 1, 2, and 3, the coke obtained as the sieve under the large sieve A and the sieve over the small sieve B was charged into the vertical scrap melting furnace 1.

  As a result, in Example 3 of the present invention, the coke ratios were 240 kg / t, 228 kg / t, and 208 kg / t, respectively, and the average coke ratio was 225 kg / t. Compared to the coke ratio of 231 kg / t when the coke having a sieve ratio A / B = 3.5) is charged as it is, the coke ratio is reduced by 6 kg.

DESCRIPTION OF SYMBOLS 1 Vertical scrap melting furnace 2 Iron-based scrap 3 Coke 4 Blower tuyeres 5 Blowers 6 Exhaust gas 7 Charger 8 Outlet 9 Hot metal

Claims (6)

In a vertical scrap melting furnace, iron-based scrap and coke are charged from the top of the furnace as the main furnace charging materials, hot air is blown from a plurality of tuyere at the bottom of the furnace, and iron-based scrap is generated by the combustion heat of the coke. A method for producing hot metal by dissolving
The coke is obtained by sieving through a two-stage sieve having different sieves, which are a large sieve A and a small sieve B, on the sieve of the large sieve A and the sieve of the small sieve B,
A hot metal production method using a vertical scrap melting furnace characterized by being coke having a particle size satisfying the following formula (1).
A / B ≦ 1.7 (1)   The hot metal manufacturing method using the vertical scrap melting furnace according to claim 1, wherein the small sieve mesh B is 20 mm or more.   The hot metal manufacturing method using the vertical scrap melting furnace according to claim 2, wherein the small sieve mesh B is 25 mm or more.   The hot metal production method using the vertical scrap melting furnace according to any one of claims 1 to 3, wherein the large sieve mesh A is 80 mm or less.   The hot metal production method using the vertical scrap melting furnace according to claim 4, wherein the large sieve mesh A is 60 mm or less.   The coke is a coke having a particle size in each section obtained by sieving with a sieve having three or more stages having different mesh sizes, and charging the coke having a particle size in each section separately into the vertical scrap melting furnace. The hot metal manufacturing method using the vertical scrap melting furnace of Claim 1 characterized by the above-mentioned.

Images