JPS62124210A - Production of pig iron - Google Patents

Abstract

PURPOSE:To decrease the content of Si in a molten iron and to increase the amt. of the gas to be generated in a process for production for gasifying coal and coke blown through tuyeres with O2 and steam, and melting and carburizing reduced iron, etc., with the formed gas by further blowing prescribed materials through said tuyeres. CONSTITUTION:A combustion chamber (a) consisting of a packed bed of coke, coal, and limestone charged from supply ports 6 is formed in front of the tuyeres 5 of a melting and gasifying furnace. A heating part (b) and melting part (c) consisting of the packed beds of coke 9 and reduced iron 10 successively charged from a supply port 8 are respectively formed in the central part of the furnace body and the upper part of the heating part (b) in front of the chamber (a). The coke and coal are burned and gasified when O2 2, steam 3 and pulverized coal 4 are blown from the tuyeres 5. The formed gas pass the heating part (b) and melts the reduced iron of the melting part (c). >=1 Kinds of iron oxide 25, reduced iron and basic auxiliary raw materials 26 are blown in the form of powder together with pulverized coal 4, etc., from the tuyeres 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing pig iron, and more particularly, the present invention relates to a method for producing pig iron, and more specifically, in which coal is blown through a tuyere and the coal and coke are gasified using oxygen and steam. 〇 (Conventional technology) Regarding improvements in the method of manufacturing molten pig iron by melting and carburizing reduced iron etc. using generated gas. Conventionally, a coke packed bed is formed inside the furnace, and acid ice, Steam and pulverized coal are injected, and the coke and pulverized coal are gasified by the oxygen and steam, and the resulting gas melts and carburizes the reduced iron charged from the top of the furnace to produce pig iron. The method of recovering the gas from the upper part of the furnace after being exposed to water is described in Japanese Patent Publication No. 59-18443 and Japanese Patent Application Laid-open No. 59-130.
These methods disclosed in Publication No. 06 and others use pulverized coal and coke as raw materials for gasification and production of molten pig iron, but unlike the blast furnace method, they use room temperature air instead of high temperature air. One of its features is that the combustibility of pulverized coal is improved and a large amount of pulverized coal can be blown into the air by using oxygen for blowing. Being able to inject a large amount of pulverized coal reduces the consumption of expensive coke and contributes to lower pig iron production costs, but pulverized coal that is injected through the tuyere
Since it burns in the highest temperature combustion zone in the furnace, approximately 2000 to 2500℃ in front of the tuyeres, it is possible to burn from 5iOz in the coal ash (1).
StO is generated by the reaction of the formula.

While rising through the high-temperature zone in the lower part of the furnace, it further becomes Si according to equation (2) and is absorbed into the hot metal, which has the disadvantage of increasing the Si content in the hot metal.

5iOz + C4SfO+ CO... (1) Si
O+ C-+St 10Co = = (2) S in hot metal
As for i, it is desirable to have it low when refining in the sea bream pot process, and it is also desirable to have it low in terms of both fuel ratio and furnace heat, so improvements have been made in terms of operation. In other words, it is well known that the process of Si transfer into the hot metal occurs in the high-temperature zone in front of the tuyere and in the lower part of the furnace, and is absorbed into the hot metal from the melting position of reduced iron to the sump in the lower part of the furnace via 1siO. Therefore, in the conventional low temperature operation method, the heat flow ratio is increased, the melting position is moved downward to shorten the Si absorption band, and the amount of FeO in the lower part of the furnace is increased. However, in the conventional method as described above, it is difficult to achieve low Si by manipulating the charging conditions of the charge. Because of this, the charge reaches from the top of the furnace to the bottom of the furnace.
It takes a long time and has no immediate effect. In addition, since an increase in the heat flow ratio results in an operation in which the furnace heat is kept low, there is a problem in that even slight fluctuations can easily cause operational troubles.

Therefore, an object of the present invention is to be able to reduce the Si content in hot metal without solving the above-mentioned problems, and at the same time, reduce the S content in the hot metal, increase the amount of iron tapped and the amount of gas generated,
An object of the present invention is to provide a method for producing pig iron that can also reduce the coke ratio. (Means for solving the problems) In order to solve the above problems and achieve the above objects, the present invention In this method, a coke packed bed is formed inside the furnace, oxygen, steam and pulverized coal are blown into the furnace through the tuyere at the bottom of the furnace, the coke and pulverized coal are gasified by the oxygen and steam, and the generated gas is charged from the top of the furnace. In a method for manufacturing pig iron by melting and carburizing reduced iron, and recovering gas from the upper part of the furnace after melting the reduced iron, from the tuyeres,
Further, the present invention, which is characterized by injecting powders of iron oxide, reduced iron, and basic auxiliary raw materials, will be described in more detail with reference to the accompanying drawings.

FIG. 1 shows an overview of a pig iron manufacturing system for carrying out the method of the present invention. It has a tuyere 5 for blowing pulverized coal 4 etc.'
A fixed bed furnace is used in which a feed port 6 for coke, limestone, etc. is provided above the tuyere, and a tap slag lower is provided at the bottom of the furnace body. In front of the tuyeres 5, there is formed a combustion chamber a consisting of a packed bed of coke, coal, and limestone, which is charged from the supply port 5. A heating section N is formed consisting of a packed bed of coke 9 to be charged, and a melting section C consisting of a packed bed of reduced iron 10, which is also charged from the supply port 8, is formed above this heating section. . In this way, coke and coal are combusted and gasified in the pre-tuyere combustion chamber a by the oxygen and water vapor blown in from the tuyere 5, and the combustion gas containing CO and H2 as main components and the ash of the coke and coal are produced. A molten slag is produced by mixing and melting quicklime produced by decomposing limestone. The generated combustion gas flows through the heating section consisting of a coke-filled bed in front of the combustion chamber to the furnace body stop, and after melting the reduced iron in the melting section C, the molten slag is recovered from the gas outlet 11. In this case, the molten reduced iron generated in the melting section C and dripping down the heating section is collected in the molten metal sump d.
, taken out from the tap slag lower. The supply port 6 may be omitted depending on the case.

According to the present invention, in the above-mentioned furnace, at least one of iron oxide, reduced iron, and basic auxiliary raw materials is blown in the form of powder from the tuyere 5 along with pulverized coal and the like. In the example, iron oxide is in the hopper 12.

13, a feeder 14, a transport pipe 15, and the basic auxiliary raw material is blown into the furnace through a hopper 16, 17, a feeder 18, and a transport pipe 19. Iron also has a similar hopper (not shown).

In the figure, 20 and 21 are pulverized coal hoppers, 2
2 indicates the same feeder, 23 indicates the same transport pipe, and 024 indicates the carrier gas.0 These iron oxides, basic auxiliary raw materials, reduced iron, and pulverized coal are transported through independent blowing as shown in Figure 1. It may be blown into the furnace using a combined system, or one or more types may be blown into the furnace, and there is no particular limitation. As for the method of blowing, gas transport is shown as an example in Figure 1, but it goes without saying that it is also possible to make a slurry with water or hydrocarbon fuel and blow it in. As for the iron oxide used for blowing, iron chain Stone powder, sintered ore powder, converter dust, etc. can be used, and as basic auxiliary raw materials, limestone, dolomite, etc., carbonates, oxides, and hydroxides of calcium and magnesium can be used. Further, as the reduced iron powder, reduced iron powder produced in a reducing furnace disclosed in, for example, Japanese Patent Application Laid-Open No. 57-210905 can be used.

(Operations) The functions of the iron oxide, reduced iron, and basic auxiliary raw materials that are blown into the melting and gasifying furnace configured as described above will be explained in detail.

l) In the case of iron oxide/reduced iron injection, the iron oxide injected from the tuyere melts in the high temperature zone in front of the tuyere, is reduced according to equation (3), and drips into the hearth.
One part is dropped into the hearth in the form of FeO, and the reaction of equation (4) lowers the Si in the hot metal〇FeOx +XC-+
Fe+X-Co...(3)2 ・Feo+Si
→ 2・Fe+5iOz ” ” (4) Both coke and pulverized coal can be considered as the C source in equation (3), but in the melting and gasifying furnace targeted by the present invention, approximately 300 to
500 kg/pig-t, several times that of a blast furnace ~10
Because twice as much pulverized coal is injected, most of the coke is reduced by the pulverized coal, and coke consumption is extremely low. (5) When injecting reduced iron, pre-tuyere combustion In the oxidation zone of the oxidation zone, it is re-oxidized according to equation (5), but the 0-generated FeO is characterized by being easy to melt because it generates heat in the oxidation reaction.
The reaction follows equation (4).

The particle size of the iron oxide used is not particularly limited, but can be selected depending on the purpose. In other words, focusing on the reaction of equation (3), if the purpose is to increase the amount of iron produced, using fine grained iron oxide will allow the reduction reaction with pulverized coal to proceed more quickly, achieving the initial purpose. can be reached. In the case of the present invention,
Unlike a blast furnace, a large amount of pulverized coal is injected, and a correspondingly large amount of iron oxide can also be injected. Since the reaction in equation (3) is an endothermic reaction, it is necessary to perform thermal compensation to prevent the temperature of the combustion zone before the tuyere from decreasing. This can be easily done by adjusting the amount. On the other hand, if you want the effect of reducing St in hot metal, use coarse-grained iron oxide, which suppresses the reaction in equation (3) and reduces the reaction amount in equation (4). This results in an increase in the Si reduction effect.

2) In the case of basic auxiliary raw materials: When carbonates and hydroxides of calcium, magnesium, etc. are blown into the tuyere, they are thermally decomposed in the high temperature zone in front of the tuyere according to equations (6) to (11) to form oxides. 7'c CO2 and H20 generated mainly react with pulverized coal to become CO and H20 CaCO3-CaO+COz... (6) Mg C
O3 part MgO + COz... (7) Ca (OH)2
- CaO+ H2O” ” (8) Mg (OH)z
→Mg O+Hz O...(9) CCh+C→2C
O...(10) H20+ C4CO+Hz... (11)(6)~
CaO and MgO produced by equation (9) melt in the high temperature zone in front of the tuyere and are assimilated with pulverized coal, coke ash, iron oxide gangue, and FeO, increasing the basicity of the slag. As the temperature increases, the activity of 5iOz in the slag decreases, and the generation of SiQ is suppressed, resulting in a decrease in Si in the hot metal. Since the S in the hot metal is well absorbed by the basic slag, the S in the hot metal can also be reduced by injecting the basic auxiliary raw material.

Furthermore, in the case of injecting iron oxide and basic auxiliary materials,
Since this is also an endothermic reaction, the immediate temperature decreases and the Si
Suppressing the generation of O also contributes to reducing Si in hot metal. The amount of gas generated increases according to equations (3), (4) and m).

(Example) Next, the effects of the present invention will be explained by examples. The results of the operation are shown for C case 2) when injected, when only basic auxiliary raw material is injected (case 3), and when both iron oxide and basic auxiliary raw material are injected at the same time (case 4). Shown in Table 1. The types, particle sizes, and compositions of the respective blown raw materials are shown in Table 2. Regarding Case 2, operations were carried out when the iron oxide was fine particles (Case 2-a) and when the iron oxide was coarse particles (Case 2-b). From Table 1, Si in the hot metal is clearly lower in cases 2, 3, and 4 compared to case 1.
The effect of reducing Si in hot metal according to the present invention is obvious. In addition.

For the reasons mentioned above, the Si reduction effect is greater in case 2-a than in case 2-a, and in case 4,
The Si reduction effect is large due to the synergistic effect of the suppression of SiO generation by reducing the Sigh activity in the front slag and the desiliconization effect by FeO.

On the other hand, in case 3.4 where basic auxiliary raw materials are injected, S in the hot metal also clearly decreases. °Furthermore, case 2.4
In this case, the coke ratio decreased, confirming the effect of reducing the amount of expensive coke used, and also confirming the effect of increasing the amount of tapped iron. It was also confirmed that the amount of gas generated increased in Case 2 and 4, confirming the effect of the present invention.

(Effects of the Invention) As described above, according to the present invention, coal is blown through the tuyere, the coal and coke are gasified using oxygen and steam, and reduced iron, etc. is dissolved and carburized by the generated gas. In the method for producing molten pig iron, powders of oxygen iron, reduced iron, and basic auxiliary raw materials are injected through the tuyere, so there is no operational trouble unlike the conventional method of reducing St in molten pig iron. While it is possible to reduce the St in hot metal, it is also possible to significantly increase the amount of raw gas. Furthermore, when injecting iron oxide or reduced iron, the effect of lowering the coke ratio and increasing the amount of iron tapped is achieved, and when injecting basic auxiliary raw materials, a reduction in the S concentration in the hot metal is achieved. can do.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a pig iron manufacturing system for implementing the present invention. 1. Furnace side wall 2. Oxygen 3. Water vapor 4.
Pulverized coal 5.Tuyere 6.Coke. Limestone supply port 7..Tapping slag port 8..Supply port 9..Coke 10..Reduced iron 1
1...Gas outlet 12.13.16.17.20.21...Hopper 14
．． 18.22...Feeder 15.19.23...Transport pipe 24...Carrier gas 25...Iron oxide 26...Basic auxiliary raw material patent applicant
Sumitomo Metal Industries Co., Ltd. 21・−1°−゛

Claims (1)

[Claims] (1) Form a coke packed bed inside the furnace, blow oxygen, steam and pulverized coal through the tuyere at the bottom of the furnace, gasify the coke and pulverized coal with the oxygen and steam, and charge the coke from the top of the furnace with the generated gas. In this method, the reduced iron is melted and carburized to produce pig iron, and the gas after melting the reduced iron is recovered from the upper part of the furnace. A method for producing pig iron, characterized by further injecting one or more of the following.