JPH0426713A - Smelting reduction iron-making method - Google Patents

Abstract

PURPOSE:To reduce unit consumption of coal by executing thermal decomposition before supplying the coal into a smelting reduction furnace to recover gas, supplying the gas into the smelting reduction furnace, using furnace waste gas as heat source for the thermal decomposition and utilizing sensible heat of heated iron ore. CONSTITUTION:The waste gas in the smelting furnace 1 is supplied to a suspension preheater 13 and the charged granular iron ore is stored in a hopper 14 after heating at >=500 deg.C. This iron ore and the coal from secondary coal hopper 16 are charged into a vessel out of the furnace. The coal is heated at >= about 400 deg.C with the sensible heat of high temp. iron ore to execute the thermal decomposition. Solid material after executing the thermal decomposition is continuously or intermittently charged into the smelting reduction furnace 1. Tar content in gaseous material discharged from the vessel 17 out of the furnace, is removed and the gas is blown into molten material in the furnace from bottom part of the smelting reduction furnace 1. By this method, the unit consumption of coal can be reduced without adoption of coal bottom blowing method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an iron manufacturing method in which granular iron ore is melted and reduced using one coal as a raw fuel and a reducing agent.

[Conventional technology]

A smelting reduction method is well known in which solid carbonaceous material and iron ore are supplied into a smelting furnace containing molten iron and molten slag, and oxidizing gas is supplied to melt and reduce iron ore. As a method of supplying carbonaceous material to the furnace,
The method of charging from the top of the furnace as proposed in JP-A No. 2-205206 and JP-A-61-64807;
A method of blowing from the bottom of the furnace, as proposed in Japanese Patent No. 222508, is known.

The former method of charging carbon material from the top of the furnace allows for simple charging equipment.

Since the coal thermally decomposes as it falls through the furnace, it is not possible to increase the secondary combustion rate, and as a result, there is a problem in that the coal consumption rate cannot be reduced. In Publication No. 64807, coal and iron ore are charged in advance into a pre-reduction furnace, and the coal is thermally decomposed in the pre-reduction furnace to obtain char and pre-reduced ore, which is further mixed with coal to form briquettes. , discloses a method of introducing this into a melting reduction furnace.

On the other hand, the latter method, in which coal is injected from the bottom of the furnace, has the advantage of improving the secondary combustion rate and reducing the coal consumption rate because the total amount of carbon in the coal can be effectively used for reduction and carburization. be. However, when melting and reducing iron ore, the coal consumption rate is 600 to 1,000 kg/T, so if you try to blow the entire amount from the bottom of the furnace, wear and tear on the piping and blowing siding will be inevitable, making long-term operation impossible. There are many difficulties in doing this stably.

[Problems to be Solved by the Invention] The present invention is intended to further improve the former method of charging carbonaceous material from above the furnace. The above-mentioned Japanese Patent Application Publication No. 61-648
If a part of the coal is charred as in Publication No. 07, the secondary combustion rate can be improved by that amount, but there is a problem that all the carbon in the raw coal cannot be used for reduction or carburization. In other words, the slag phase in the smelting reduction furnace and the slag
The carbon required for the reduction reaction of iron oxide that progresses at the metal interface and the carburization reaction in the molten iron must be obtained from raw coal.
When volatile matter is released when coal is thermally decomposed in the preliminary reduction furnace, the carbon in the volatile matter becomes co and co□ and is discharged outside the furnace, making the total amount of carbon in the raw coal effective. It cannot be subjected to reduction or carburization, and there is a problem in that the more volatile content of the coal used, the more the coal consumption rate must be increased.

The purpose of the present invention is to solve the above-mentioned problems of the prior art,
The object of the present invention is to provide a method that can reduce the coal consumption rate without adopting the coal bottom blowing method, which is problematic in terms of operation.

[Means to solve problems]

According to the present invention, iron ore and coal are charged from above into a smelting furnace containing molten iron and molten slag, and an oxidizing gas is supplied into the furnace to melt and reduce the iron ore. The iron ore is heated to at least 500°C by bringing the iron ore into contact with the high-temperature waste gas generated during the smelting reduction process outside the smelting furnace, and the high-temperature iron ore and coal are placed in a container outside the furnace. The coal is pyrolyzed in this container by the sensible heat of the iron ore, and the solid material after pyrolysis is charged into the smelting furnace from above, and a part of the gas produced by the pyrolysis or The above-mentioned problem was solved by injecting the entire amount into the molten material in the smelting furnace.

At that time, the normal flux charged into the furnace can also be heated to 500° C. or higher with high-temperature waste gas and charged into the outer container together with the iron ore. If the tar content is removed from the gas generated in the outer vessel before it is blown into the melt, and the removed tar content is supplied onto or into the melt in the furnace, it will be possible to remove the tar content from the raw coal. Effective use of virtually all carbon can be achieved. In addition, the sensible heat of the furnace waste gas, which is still at a high temperature after being used to heat the iron ore and flux, is transferred to the coal before it is charged into the 5 outer furnace container.
It is also possible to preheat the coal to a temperature below thermal decomposition temperature (for example, below 350° C.) before charging it into the outer vessel.

In this way, the present invention thermally decomposes coal before supplying it to a smelting reduction furnace to recover char, tar, and gas,
It is characterized by supplying them to a smelting reduction furnace, and by using the sensible heat of iron ore and flux heated using furnace waste gas as a heat source for this pyrolysis.

(Detailed Description of the Invention) Fig. 1 shows a process flow suitable for implementing the method of the present invention.The configuration and operation of the method of the present invention will be described in detail based on the figure.

1 is a smelting reduction furnace, and molten iron 2 and molten slag 3 are present in the furnace during smelting. The tuyere 55 at the bottom of the furnace is a nozzle on the side wall, and the reference numeral 6 is a lance for supplying oxidizing gas (oxygen gas). Solid iron ore, carbonaceous material, and flux are charged from the charging lower above the furnace. The smelting waste gas is discharged through an exhaust duct 8. The charging raw materials, iron ore, flux and coal, are each used in an iron ore hopper 9. A predetermined amount is cut out from the flux hopper 10 and the coal pumper 11.

In one aspect of the present invention in such a smelting reduction facility, iron ore is supplied to ore preheating facilities 12a, 12b, and 12c. Only iron ore may be supplied to this preheating equipment 12, but flux may also be supplied together. This example will be explained below. The preheating equipment 12 uses a suspension preheater 13, and while supplying waste gas from the smelting furnace to the suspension preheater 13, granular iron ore and flux are introduced into the suspension preheater 13. is heated. The illustrated example uses a three-stage cascade system.

The lower stage will come into contact with the high temperature waste gas. This preheating equipment is not limited to the one shown in this example, but may also be of the fluidized bed type or spouted bed type, as long as it brings the powder into solid-gas contact with a high-temperature gas. The iron ore and flux that have passed through such preheating equipment are kept at a high temperature with a predetermined composition, and are transferred to a high-temperature hopper 1 for ores lined with a fireproof insulation material.
4 - can be stored. The material stored in the high temperature hopper 14 is controlled to have a temperature of 500°C or higher. However, if the temperature exceeds 1200°C, the ore will sinter and become impossible to handle, so the temperature is preferably in the range of 500 to 1200°C.

On the other hand, raw coal for 1 coal hopper 11 is 1 coal drying equipment 1
Secondary coal hopper 16 lined with fireproof insulation material after passing through step 5
It can be stored in a large amount. Coal drying equipment 15 stores 100 coal
It preheats to ~350°C, and the waste gas that has passed through the ore preheating stage Wi12 can be used as the heat source for this preheating, but if the waste gas and coal are brought into direct contact, two coals It is best to use indirect heating for this heating as some of the coal may be heated to high temperatures and volatiles may be released from the coal. Specifically, it is convenient to circulate the heat medium between the waste gas passage and the coal drying equipment 15. Nitrogen gas or water vapor can be used as the heat medium.

If the waste gas that has passed through the ore preheating equipment 12 is insufficient in calorific value as a heat source for preheating the coal, part of the heat of the high temperature waste gas that has left the smelting reduction furnace 1 may be used. can. In any case, this coal drying equipment 15 has 1
It is important to control the preheating of the coal to a temperature range of 00-350°C. This is because if the temperature is lower than 100°C, moisture adhering to the coal cannot be removed sufficiently, and if the temperature exceeds 350°C, volatile matter will be released from the coal.

As described above, the high temperature hopper 14 for ore has 500
~1200 °C granular iron ore and optionally additional flux and 100 °C in the secondary coal hopper 16.
Coal at ~350°C is stored.

Then, both materials are cut out from the five-carrier hoppers 14 and 16 in a proportion appropriate to the blending ratio to the melting reduction furnace 1 while maintaining their temperature, and charged into the outer furnace container 17, where they are held for a predetermined time.

This outer-furnace container 17 is a closed container lined with a fireproof and insulating material, and while both materials are held here for a predetermined time, one coal is heated by 400 heated above ℃.

Thermal decomposition progresses. The thermal decomposition of this coal generates gaseous substances, and the solid substances change into char with a low volatile content. The gaseous substances generated include gases such as CH, Hz and tar, and these are sent from the gas outlet 18 of the outer vessel 17 to the cool removal device 20 and gas purification equipment 21 via the duct 19. It will be done. When the thermal decomposition of this coal is substantially completed, the solids in the outer vessel 17, that is, iron ore and
The flux-char mixture is fed into the melting reduction furnace 1 continuously or intermittently.

On the other hand, the gaseous material discharged from the outer vessel 17 is cooled in the tar removal device 20, and gas and tar are separated. At that time, the water vapor derived from the crystallized water in the coal in the gas also condenses to produce ammonium water 22, but this ammonium water 22 and tar 23
The tar 23 is separated and collected, and only the tar 23 is supplied to the melting reduction furnace I. The method for supplying this tar into the furnace is to blow it into the slag bath 3 through the nozzle 5, or to mix the tar with fine powder such as dust generated in the melting reduction process or other processes, and then to feed the mixed material from the input lower. It is sufficient to adopt a method in which the material is put into the furnace. According to the former method of blowing tar into a slag bath, the tar is thermally decomposed in the slag bath to generate carbon, and the carbon is subjected to the melt-reduction reaction that proceeds within the slag bath. If fine powder and tar are kneaded and the kneaded mixture is put in the form of a lump, it will directly reach the slag bath as a lump, and after reaching the slag bath, the tar will be subjected to a melt-reduction reaction in the same manner as in the case of blowing.

On the other hand, after the tar and ammonium water have been separated, the gas is removed from the gas purification equipment 21 to remove harmful substances such as H and S. Injected into the body. The blowing position may be either the geoslag bath 3 or the metal bath 2. Hydrocarbons contained in the gas are thermally decomposed into carbon and hydrogen in a high-temperature bath, and the carbon is subjected to carburization and reduction reactions. Since thermal decomposition of hydrocarbons is an endothermic reaction, when oxygen is bottom-blown from one tuyere 4, this hydrocarbon-containing gas can be used as a siding cooling gas.

In addition, this hydrocarbon-containing gas is 6000 to 7000kc.
Since it has a calorific value of about 1/Nm'', a part of the generated gas can be used as fuel gas for a heat source such as a heating furnace.

Figures 2 and 3 show cases in which 1 coal is directly charged into the furnace and 1.
This is a diagram illustrating the phenomena inside the furnace when char, tar, and gas are supplied separately according to the method of the present invention. When one coal is directly charged into the smelting reduction furnace as shown in FIG. 2, the temperature of the two coals increases as they fall toward the slag bath, and volatile matter is released. The coal that has released volatile matter turns into char and reaches the slag bath. The carbon in the char is subjected to iron oxide melting reduction reaction (■) and carburization reaction (■). However, the amount of carbon is only the fixed carbon content in coal, and steam coal with a high volatile content
The amount of fixed carbon is only about 70% of the total amount of carbon in coal.

In other words, when one coal is directly charged, only about 70% of the total carbon content in one coal is effectively utilized for the melt reduction reaction (1) and the carburization reaction (2). In this way, the unit consumption of 5 coal becomes higher due to the lower carbon utilization efficiency. From the slag bath, CO generated by the melt reduction reaction (■) is released, and the CO
A part of the gas is combusted (secondary combustion) by O2 injected from the lance, and CO2 is produced by formula (2).

In addition, the above volatile matter is thermally decomposed at high temperature in the furnace and becomes carbon and 8
2 is produced, but the carbon and CO□ produced by the secondary combustion react with each other (endothermic reaction), and CO is produced again according to equation 0. As a result, the secondary combustion rate becomes a low value. Therefore, the unit consumption of coal has to be high. In this way, when two coals are directly input, the coal consumption rate cannot be reduced in terms of carbon utilization efficiency and secondary combustion rate.

As shown in Fig. 3, 9 Chatard obtained by applying the method of the present invention,
When gas is supplied into the furnace, the temperature of the char is raised as it falls toward the slag bath.

Residual volatile matter is released, but the amount is small, and the main component is H2, and almost all of the carbon in the char can be fed into the slag. In addition, gas containing tar and hydrocarbons is also supplied to the slag bath and metal bath, so that the carbon decomposed according to Equation 0 is subjected to the smelting reduction reaction (1) and the carburization reaction (2) of iron oxide. Therefore, in the method of the present invention (1), most of the total carbon content in the coal (2) can be effectively utilized. Furthermore, CO generated by the reduction of the 0 type and H2 generated by the 0 type thermal decomposition are released from the 2 slag bath, and some of them are combusted by the 0□ sprayed from the lance.
Secondary combustion) COg and H2O are produced, but in this case, carbon-containing substances are not released from the char, so C02 + H20 is directly discharged from the furnace, resulting in a high secondary combustion rate. A part of the heat generated by the secondary combustion reaction is transferred to the slag bath to cover the heat required for the smelting reduction reaction. In this way, according to the method of the present invention, both the carbon utilization efficiency and the secondary combustion rate are improved, and the amount of raw coal can be reduced by one car.

〔Example〕

Using substantially the same flow process as shown in FIG. 1, iron ore having the chemical composition shown in Table 1 is melted and reduced,
Produced hot metal. Industrial analysis values of the coal used are shown in Table 2. The particle size of coal and iron ore is 30mm each.
and -10 mm.

In addition, quicklime and lightly calcined dolomite were used as auxiliary raw materials (flux). A fluidized bed type furnace was used as the coal drying equipment 15 for coal. As the ore preheating equipment I2, a one-type suspension preheater was used. The smelting reduction furnace is an iron bath furnace that is a modified 7T test converter.

Table 1: Chemical composition of iron ore (wt, χ) Table 2: Industrial analysis value of coal (IIT, χ) Table 3 shows the operational specifications when 1 smelting reduction is performed. In all operations, the coal consumption rate and oxygen consumption rate were adjusted so that the hot metal temperature was 1500 to 1510°C. In Examples 1 and 2.4, the preheating temperature of iron ore and coal was changed, and the thermal decomposition temperature of one coal was 480.6.
The temperature was changed from 00° to 810°C. At this time, the higher the pyrolysis temperature was, the more gas generation tended to increase slightly, but no difference was observed in other operating parameters, and the secondary combustion rate was high at approximately 75%. 8 Coal unit is approximately 650kg/T
was at a low level. In Example 3, collected dust (including carbonaceous iron ore, etc.) from the smelting reduction furnace and coal drying equipment was kneaded with tar and formed into a lump of approximately 60 mm in size, which was then charged into the smelting reduction furnace. In this case as well, the coal consumption rate was at a low level as in the other examples. On the other hand, in a comparative example in which the method of the present invention was not applied and preheated iron ore and coal were directly charged into the smelting reduction furnace, the secondary combustion rate was low, and the hot metal temperature was lowered to 1500
In order to reach 1510℃, one raw coal car needs 722kg/
It was necessary to increase it to T.

Table 3 Operating specifications during melt reduction

[Brief explanation of the drawing]

Figure 1 is an equipment layout system diagram of equipment for implementing the method of the present invention;
FIG. 2 is a diagram schematically showing the reaction in the furnace when coal is directly charged into the furnace, and FIG. 3 is a diagram schematically showing the reaction in the furnace when the method of the present invention is followed. ■...Melting reduction furnace, 2...Metal bath. 3. Slag bath, 4. Tuyere at the bottom of the furnace, 5. Side wall nozzle, 6. Lance. 7. Solid material inlet, 8. Exhaust duct. 9. Iron ore hopper, 10. Flux hopper,
11... Coal hopper 12... Ore preheating equipment, 14... High temperature hopper for ore,
15... Coal drying equipment. 16...Secondary coal hopper, 17...Outside furnace for pyrolysis, 20...Tar separation device 21...Gas purification device.

Claims (5)

[Claims] (1) In the smelting reduction method, iron ore and coal are charged from above into a smelting furnace containing molten iron and molten slag, and oxidizing gas is supplied into the furnace to melt and reduce the iron ore. The iron ore is heated to at least 500°C by bringing the iron ore into contact with the high-temperature waste gas generated during the smelting reduction process outside the smelting furnace.
The high-temperature iron ore and coal are charged into a container outside the furnace, and the coal is pyrolyzed in this container by the sensible heat of the iron ore, and the solids after pyrolysis are placed in the smelting furnace. A smelting reduction iron manufacturing method characterized by injecting gas from above the furnace and blowing some or all of the gas generated by pyrolysis into the molten material in the smelting furnace. (2) In the smelting reduction method, iron ore and coal are charged from above into a smelting furnace containing molten iron and molten slag, and oxidizing gas is supplied into the furnace to melt and reduce the iron ore. The iron ore and flux are heated to at least 500°C or higher by contacting the high-temperature waste gas generated during the smelting reduction process with the iron ore and the flux to be charged into the furnace outside the smelting furnace, and the iron ore and flux are heated to at least 500°C or higher. Coal is charged into a container outside the furnace, and the coal is pyrolyzed in this container by the sensible heat of the iron ore and flux.The solid material after pyrolysis is charged into the smelting furnace from above, and the A smelting reduction ironmaking method characterized by blowing some or all of the gas produced by decomposition into the molten material in a smelting furnace. (3) The smelting reduction iron manufacturing method according to claim 1 or 2, wherein the gas generated by thermal decomposition is blown into the melt after removing tar. (4) The smelting reduction iron manufacturing method according to claim 3, wherein the removed tar is supplied onto or into the melt in the furnace. (5) The smelting reduction iron manufacturing method according to claim 1, 2, 3, or 4, wherein the coal is charged into the outer vessel after being preheated to a temperature of 350° C. or less by the heat retained in the furnace waste gas.