JP4762855B2 - Blast furnace charging raw material manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a raw material charged with a blast furnace that improves the strength and reducibility of iron ore, particularly massive iron ore.

  The massive iron ore is often used in an amount of 10 to 20 mass% as a blast furnace charging raw material, and the massive iron ore containing crystal water is also used. At this time, the massive iron ore is used after being sieved to a particle size of 10 mm or more and 30 mm or less in order to maintain good ventilation in the blast furnace.

  In many cases, powdered iron ore is agglomerated as sintered ore or pellets and used as a blast furnace charging raw material in an amount of 80 to 90 mass%. Among these, sintered ore is often used in an amount of 70 to 80 mass% as a blast furnace charging raw material.

  As a method of improving the quality of sintered ore, tar heated at 60 ° C. is sprayed on the sintered ore stored in the yard, and the pores of the sintered ore are filled with tar. Patent Document 1 describes a method for improving the reducibility.

JP 2000-73127 A Tadahiro Inakaku: “Sintered Ore”, Japan Iron and Steel Institute, 2000

  Crystallized water contained in the massive iron ore begins to decompose at about 200 ° C. and is removed from the iron ore. When the crystal water contained in the iron ore is decomposed and removed, cracks occur in the iron ore, the amount of pores increases, and the strength decreases. Therefore, when the massive iron ore containing crystal water is charged into the blast furnace and heated, and the crystal water contained in the iron ore is decomposed and removed, the strength of the iron ore decreases in the blast furnace.

  As a result, iron ore is pulverized in the blast furnace, gas permeability in the blast furnace is inhibited, and blast furnace operation is inhibited.

  In particular, massive iron ores containing 4 mass% or more of crystal water, for example, limonite ore from Australia, contain 4 mass% or more of crystal water because the strength after crystal water is decomposed and removed is greatly reduced. Increasing the amount of massive iron ore will hinder blast furnace operation. Here, the analysis of crystal water is based on the Karl Fischer method (JIS M8211).

  The method of improving the reduced powdering property and reducibility of sintered ore described in Patent Document 1 is applied to massive iron ore containing crystal water, and the tar heated to 60 ° C. Even if sprayed over the massive iron ore contained, the crystal water contained in the massive iron ore is hardly thermally decomposed and removed because the temperature is lower than 200 ° C.

  When the tar is heated to 200 ° C. or higher at which the crystal water contained in the massive iron ore starts to thermally decompose, part of the tar is gasified and the viscosity of the remaining liquid tar increases. It has been found that such a liquid tar hardly penetrates into cracks formed by thermally decomposing and removing water of crystallization in the iron ore and has little effect on improving the strength of the iron ore.

  Therefore, the method for improving the reduced powdering property and reducibility of the sintered ore described in Patent Document 1 does not serve as a means for suppressing the strength reduction in the blast furnace of massive iron ore containing crystal water. .

  Furthermore, tar is an expensive product used as an industrial raw material, and it is economically desirable to use a cheaper product instead of tar.

  An object of this invention is to provide the manufacturing method of the blast furnace charging raw material which can improve the intensity | strength at the time of blast furnace charging of the iron ore containing crystal water in view of the said subject. Moreover, the manufacturing method of the raw material of a blast furnace charge which can improve the intensity | strength at the time of blast furnace charge of the iron ore containing crystal water using a comparatively cheap material, without using expensive materials like tar The purpose is to provide. Furthermore, it aims at providing the manufacturing method of the blast furnace charging raw material which can improve the reducibility at the time of blast furnace charging.

  The gist of the present invention for achieving the above object is as follows.

  (1) An iron ore containing crystal water and plastic are charged from the top of the shaft furnace supplied with heated gas from the tuyere, and the crystal water in the iron ore is pyrolyzed by sensible heat of the heated gas. In addition to generating pores, the plastic is melted and pyrolyzed and gasified, and the liquid pyrolyzed product generated by condensation of the molten plastic and pyrolyzed gas is formed in the pores of the iron ore. A method for producing a blast furnace charging raw material, which comprises infiltrating and carbonizing a plastic and a thermal decomposition product which have penetrated into the pores of the iron ore, and then cooling in the shaft furnace.

  (2) The method for producing a blast furnace charging raw material according to (1), wherein the iron ore is a massive iron ore having a particle diameter of 10 mm to 30 mm.

  (3) The method for producing a blast furnace charging raw material according to (1) or (2), wherein a ratio of crystallization water in the iron ore containing the crystallization water is 4 mass% or more.

  (4) The method for producing a blast furnace charging raw material according to any one of (1) to (3), wherein polyethylene, polypropylene, polystyrene, or a mixture containing these is used as the plastic.

  (5) Exhaust gas is discharged from the top of the shaft furnace, and the exhaust gas temperature is set to 200 to 500 ° C. The method for producing a blast furnace charging raw material according to any one of (1) to (4) .

  (6) The method for producing a blast furnace charging raw material according to any one of (1) to (5), wherein the temperature of the heated gas supplied to the shaft furnace is set to 700 to 1100 ° C.

  According to the method for producing a blast furnace charging raw material for improving the strength and reducibility of the massive iron ore of the present invention, it is economically possible to improve the strength and reducibility of the massive iron ore containing crystal water. It becomes possible and contributes to stabilization of blast furnace operation.

  The manufacturing method of the raw material charged with a blast furnace for improving the strength and reducibility of the iron ore according to the present invention is characterized in that the strength of the iron ore is improved by infiltrating plastic into pores in the iron ore. Furthermore, the reduction rate when the iron ore is reduced in the blast furnace is increased by carbonizing the plastic that has penetrated into the pores in the iron ore in the pores.

  Here, the iron ore as referred to in the present invention is an iron ore used without using pellets or sintered ore. In addition, the massive iron ore is iron ore that is adjusted to a particle size of 10 to 30 mm by sieving and charged into a blast furnace.

  Thermal decomposition of crystal water in iron ore starts at around 200 ° C and becomes active around 300 ° C. On the other hand, the melting temperature of plastic is about 150 ° C., although it depends on the type. When the plastic is further heated, the gasification of the plastic starts from about 400 ° C. and becomes active around 600 ° C.

  Therefore, if the iron ore and plastic containing crystal water are held in the range from 200 ° C. at which the crystal water in the iron ore starts thermal decomposition to 500 ° C. at which plastic gasification is not yet activated, the crystal water in the iron ore is retained. Are removed by thermal decomposition, and the plastic coexists in a molten state.

  As a result, the crystallized water is thermally decomposed and removed, so that the molten plastic can penetrate into cracks and pores formed in the iron ore.

  Here, it is shown in FIG. 3 that the iron ore is more likely to be pulverized by increasing the proportion of crystal water. FIG. 3 is a diagram showing the relationship between the water content of crystallization and the powder rate determined based on a method of indexing as an RDI (Reduction Degradation Index) by a reduction powdering test method for sintered ore. The temperature rise and reduction temperature conditions in the reduced pulverization test method for sintered ore are as follows.

The temperature was raised to 550 ° C. in 45 minutes in an N ₂ gas atmosphere, reached 550 ° C., held for 30 minutes, and then immediately switched to reducing gas (CO = 30 vol%, N ₂ = 70 vol%) to 30 Hold for a minute, then immediately switch to N ₂ gas and cool.

  In this strength test method, the temperature was changed from 550 ° C. to 300 ° C. The sample was 500 g having a size of 15 to 20 mm, all other conditions were made equal, and evaluation was made with a powder rate of 3 mm or less.

  As can be seen from FIG. 3, iron ore containing 4 mass% or more of crystal water is particularly pulverized due to the decrease in strength caused by thermal decomposition of crystal water in the blast furnace. Moreover, the effect of suppressing the pulverization of iron ore in the blast furnace and avoiding abnormalities in the blast furnace operation caused by the pulverization is particularly great by performing the heat treatment.

According to Non-Patent Document 1, the chemical formula of limonite Limonite is Fe ₂ O ₃ .nH ₂ O (n = 0.5 to 4.0), and at this time, the proportion of crystal water is 5 to 31 mass%. The upper limit of crystal water in iron ore is theoretically considered to be 31 mass%.

  As the plastic, polyethylene, polypropylene, polystyrene, or a mixture containing these can be used, and used waste plastic is also included. It is economical to use the used waste plastic, and resource recycling can be performed efficiently.

  Further, as a plastic, a liquid product obtained by heating polyethylene, polypropylene, polystyrene, or a mixture containing these and cooling and condensing the gas generated by thermal decomposition has a viscosity in a molten state at 200 ° C. It is extremely low and penetrates fine pores in iron ore.

  When the pores generated in the iron ore are fine, the presence of a liquid product in which the gas generated by such thermal decomposition is cooled and condensed is effective. The temperature at which gas is generated by this thermal decomposition is between 500 ° C. and 700 ° C. at which plastic carbonization does not occur so actively, centering on 600 ° C. at which gasification occurs actively.

  Plastic that has penetrated the pores of iron ore begins to carbonize at around 700 ° C. When carbides exist in the pores, when heated to 1000 ° C. or higher in the blast furnace, the carbides in the pores function as a reducing agent, and the reduction rate of iron oxide in the iron ore increases. Therefore, heating from 700 ° C. to 1000 ° C. has a great effect of improving the reducibility of iron ore by generating carbide in the pores.

  Further, when heated from 1000 ° C. to 1100 ° C., part of the iron oxide in the iron ore is reduced by a part of the carbides in the pores to produce metallic iron, so that an effect of improving the production efficiency of the blast furnace can be expected. . In addition, the effect of increasing the reduction rate of iron oxide in iron ore due to the remaining carbide can be similarly expected. However, if it becomes 1100 degreeC or more, iron oxide or a part of gangue of an iron ore will melt | dissolve, a pore will be obstruct | occluded and reducibility will fall.

  Therefore, the temperature for heating the iron ore infiltrated with the plastic is desirably 700 ° C. to 1100 ° C. The ore after carbonization is cooled with a reducing gas such as blast furnace gas at room temperature to a temperature that does not generate reoxidation heat in the atmosphere and does not exceed 300 ° C, and then discharged from a carbonization furnace such as a shaft furnace. It is desirable.

  (A) The iron ore containing plastic water and the plastic are heated to 200 to 500 ° C. to thermally decompose and remove the crystal water in the iron ore, and the plastic is melted to form pores in the iron ore. And (B) a process of pyrolyzing and gasifying the plastic at 500 to 700 ° C., and (C) a pyrolysis product of the plastic into pores in the iron ore. As a method for performing the process of infiltrating in a molten state, and (D) further heating the iron ore in which the plastic has penetrated into the pores to 700 to 1100 ° C. to carbonize the plastic in the pores, By using a furnace and controlling the temperature distribution in the height direction in the furnace, all the processes (A) to (D) described above are incorporated in one shaft furnace. It is possible to present.

  This will be described with reference to FIG. First, iron ore and plastic 3 are charged into the top of the shaft furnace 11.

  Preheated blast furnace gas (BFG), coke oven gas (COG), or plastic gasified gas recovered from the top of the shaft furnace 11 from the tuyere 12 installed in the middle of the shaft furnace 11 in the height direction. In addition, a partially heated reducing gas 1 having a temperature of 1000 ° C. is injected, and the iron ore 4 and the plastic 5 in the shaft furnace are heated with this gas.

  The heated gas 1 exchanges heat with iron ore and plastic while rising inside the shaft furnace 11, decreases in temperature, and is discharged out of the system as exhaust gas 2 from the upper part of the shaft furnace 11.

  The iron ore 4 and the plastic 5 charged in the shaft furnace 11 descend the interior of the shaft furnace 11 and are heated by the heating gas that ascends the interior of the shaft furnace 11, and the crystal water is thermally decomposed and removed. It becomes iron ore 6 and molten plastic 7. Here, the melted plastic 7 penetrates into pores in the iron ore 6 from which the crystal water has been thermally decomposed and removed.

  Here, in the high temperature part below the shaft furnace 11, the high-boiling components in the gas generated by thermal decomposition of the molten plastic are condensed and coexist as a liquid. This condensed liquid pyrolysis product also penetrates into the pores in the iron ore 6 from which the crystal water has been pyrolyzed and removed.

  The iron ore in which the plastic has permeated and the excess molten plastic remaining without completely penetrating into the pores of the iron ore descends inside the shaft furnace 11 and is further heated. First, the iron ore particles and the excess molten plastic existing between the particles have better contact efficiency with the heated gas rising inside the shaft furnace 11 than the plastic that has penetrated into the pores of the iron ore. Then, it is pyrolyzed and gasified.

  Furthermore, when the iron ore infiltrated with the plastic and the excessive molten plastic fall down inside the shaft furnace 11, the plastic in the iron ore is further heated in the high temperature region where the heated gas 1 at a temperature of 1000 ° C. is blown. The remaining molten plastic is carbonized and adheres as carbide in the iron ore particles or on the iron ore particle surfaces.

  The high-temperature iron ore to which the carbide has adhered is cooled by the normal temperature blast furnace gas used as the cooling gas 9 while further descending the inside of the shaft furnace 11, and the carbonized iron ore 8 is carbonized from the lower part of the shaft furnace 11. Discharged as. The cooled gas 9 exchanges heat with the iron ore after carbonization, the temperature rises, and is discharged out of the system as the cooled out gas 10.

  By adjusting the pressures of the heated gas 1 and the cooled gas 9, a part of the cooled gas 9 rises in the shaft furnace 11 together with the heated gas 1, but most of it is discharged out of the system as the cooled gas 10. Is done.

  An example of the gas temperature distribution measurement result inside the shaft furnace 11 at this time is shown in FIG. Inside the shaft furnace 11, in the region from the tuyere where the heated gas 1 is blown to 1 m above the tuyere, it is suitable for carbonizing the plastic in the iron ore and the remaining molten plastic at 1000 ° C. to 700 ° C. It is temperature.

  In the region from 1 m above the tuyere to 2 m above the tuyere, the temperature is 700 ° C. to 500 ° C., which is suitable for the pyrolysis and gasification of the molten plastic.

  In the region from 2 m above the tuyere to the charge surface, the water of crystallization in the iron ore is removed by thermal decomposition at 500 ° C to 300 ° C, and the plastic melts and is generated by thermal decomposition. The high-boiling components in the gas are condensed into a liquid, and the temperature is suitable for these molten plastics to penetrate into the pores in the iron ore.

  Examples of the method for producing a blast furnace charging raw material for improving the strength or reducibility of the iron ore of the present invention are shown below. As the iron ore, a massive iron ore having a particle diameter of 10 to 30 mm containing 8 mass% of crystal water was used. The analysis of crystal water is based on the Karl Fischer method (JIS M8211).

  The plastic used was a waste plastic containing 29 mass% polyethylene, 24 mass% polypropylene, and 28% polystyrene. The remaining components are other plastics such as polyvinyl chloride and impurities.

  A manufacturing method is demonstrated based on FIG. The iron ore was charged at 500 t / d and the waste plastic was charged at 500 t / d from the top of the shaft furnace 11. Since the exhaust gas 2 discharged from the top of the shaft furnace 11 contains plastic-derived tar, the exhaust gas 2 was partially burned with oxygen and reformed at 1100 ° C.

The reformed gas was purified to obtain a normal temperature process gas. This process gas has a calorific value of 2,190 kcal / Nm ³ , and a part of this process gas is used as a raw material gas for the heating gas 1.

This raw material gas 33,100 Nm ³ / h is partially burned with oxygen, and at 1050 ° C., H ₂ is 30 vol%, H ₂ O is 15 vol%, CO is 38 vol%, CO ₂ is 10 vol%, and N ₂ is 7 vol%. , 33,600 Nm ³ / h of heated gas 1 was produced, and this heated gas 1 was blown from the tuyere 12 installed in the middle part of the shaft furnace 11.

  A part of room temperature process gas that was not used as a raw material for the heating gas was charged into the furnace as a cooling gas 9 from the lower part of the shaft furnace 11, and the ore carbonized in the shaft furnace was cooled, From the bottom of the shaft furnace 11, the iron ore 8 was discharged after carbonization.

  The strength of iron ore after carbonization produced by this method was investigated. The test method for evaluating the strength of the iron ore was based on the method of indexing as RDI (Reduction Degradation Index) by the reduced powdering test method of sintered ore. The conditions that are different from those of the reduced pulverization test method for sintered ore are described below.

The temperature rise and reduction temperature conditions of the reduced pulverization test method for sintered ore are as follows. The temperature was raised to 550 ° C. in 45 minutes in an N ₂ gas atmosphere, reached 550 ° C., held for 30 minutes, and then immediately switched to reducing gas (CO = 30 vol%, N ₂ = 70 vol%) Hold for 30 minutes, then immediately switch to N ₂ gas and cool to room temperature.

  In this strength test method, the temperature was changed from 550 ° C. to 300 ° C. The sample was 500 g having a size of 15 to 20 mm, all other conditions were made equal, and evaluation was made with a powder rate of 3 mm or less. As a result, in the Example, the powder rate was 30 mass%.

  On the other hand, as a reference example, as a reference example, as a comparative example, a carbonization treatment produced in this example from a massive iron ore containing 8 mass% of crystal water and a massive iron ore containing 8 mass% of crystal water. The post iron ore was evaluated by the strength test method. As a result, the powder rate was 15 mass% for the sintered ore and 70 mass% for the massive iron ore containing 8 mass% of crystal water.

  That is, according to the present invention, it was found that even an iron ore having crystal water can greatly improve the strength and can approach the strength level of the sintered ore.

  Moreover, the reducibility of the iron ore after carbonization produced by this method was investigated. The test method for evaluating the reducibility of iron ore was based on the iron ore reduction test method (JIS M 8713). The conditions different from the iron ore reduction test method are described below.

The temperature rise and reduction temperature conditions of the iron ore reduction test method are as follows. The temperature was raised to 900 ° C. in an N ₂ gas atmosphere, and after reaching 900 ° C., held for 30 minutes, and then immediately switched to reducing gas (CO = 30 vol%, N ₂ = 70 vol%) and held for 180 minutes. Then, immediately switch to N ₂ gas and cool. In this test method for evaluating reducibility, the temperature was changed from 900 ° C. to 1050 ° C. All other conditions were made equal.

  Under the condition of a temperature of 1050 ° C., the reduction rate of the sintered ore of the reference example was 75%, and the reduction rate of the massive iron ore containing 8 mass% of the crystallization water of the comparative example was 55%, whereas the crystallization water The reduction rate of the carbonized iron ore produced from the massive iron ore containing 8 mass% of this example is 75%, which is equivalent to the sintered ore, and the massive iron ore containing 8 mass% of crystal water of the comparative example It was more reducible than stone.

  In addition, the ratio of the blast furnace that operates with 10% of iron ore raw material charged with massive iron ore containing 8% by mass of crystal water, and 90% of iron ore raw material charged with sintered ore and pellets is 2.10, when using the blast furnace charging raw material manufactured in the example, that is, the bulk iron ore containing 8 mass% of crystal water was charged 5% of the iron ore raw material The blast furnace output ratio increased to 2.21 when the plastic infiltrated iron ore was charged with 5% of the iron ore raw material and the sintered ore and pellets were charged with 90% of the iron ore raw material. It was possible to improve productivity.

In the manufacturing method of the raw material charged with a blast furnace which improves the intensity | strength or reducibility of the massive iron ore of this invention, it is a figure which shows an example which processes the massive iron ore containing 8 mass% of crystal water using a shaft furnace, and a plastic. is there. It is a figure which shows an example of the gas temperature distribution of the shaft furnace height direction in the case of using a shaft furnace for the manufacturing method of the blast furnace charging raw material which improves the intensity | strength or reducibility of the massive iron ore of this invention. It is a figure which shows the influence which acts on the powder rate of crystallization water content rate.

Explanation of symbols

1 Heating gas 2 Exhaust gas 3 Iron ore and plastic 4 Iron ore 5 Plastic 6 Iron ore (after hydrothermal decomposition of crystal)
7 Plastic (molten state)
8 Iron ore after carbonization 9 Cooled gas 10 Cooled out gas 11 Shaft furnace 12 Tuyere

Claims (6)

  A shaft furnace supplied with heated gas from the tuyere is charged with iron ore and plastic containing crystal water from the top of the furnace, and the sensible heat of the heated gas removes the crystal water in the iron ore by pyrolysis. In addition to generating pores and melting and pyrolytic gasifying the plastic, the liquid pyrolysis product generated by condensation of the molten plastic and pyrolytic gas is infiltrated into the pores of the iron ore, Furthermore, the plastics and thermal decomposition product which penetrated into the pores of the iron ore are carbonized and then cooled in the shaft furnace, and the method for producing a blast furnace charging raw material is characterized.   The method for producing a raw material for a blast furnace charge according to claim 1, wherein the iron ore is a massive iron ore having a particle size of 10 mm or more and 30 mm or less.   The method for producing a blast furnace charging raw material according to claim 1 or 2, wherein a ratio of crystallization water in the iron ore containing the crystallization water is 4 mass% or more.   The method for producing a blast furnace charging material according to any one of claims 1 to 3, wherein polyethylene, polypropylene, polystyrene, or a mixture containing these is used as the plastic.   The method for producing a blast furnace charging raw material according to any one of claims 1 to 4, wherein exhaust gas is discharged from a top of the shaft furnace, and the exhaust gas temperature is set to 200 to 500 ° C.   The temperature of the heating gas supplied to the said shaft furnace shall be 700-1100 degreeC, The manufacturing method of the blast furnace charging raw material of any one of Claims 1-5 characterized by the above-mentioned.

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