JPH04314808A - Method and equipment for reforming exhaust gas in smelting reduction furnace - Google Patents

Abstract

PURPOSE:To reform exhaust gas to get gas very suitable for preliminary reduction by adding coal materials for reforming having different properties according to the property of the exhaust gas in preliminary reduction of a feed ore by the exhaust gas from a smelting reduction furnace. CONSTITUTION:Exhaust gas G from a smelting reduction furnace 2 enters a riser 5 through a flue 3 and a hot cyclone 4 installed in a fluidized bed preliminary reduction equipment 1 and preliminarily reduces a pulverized iron ore therein while it is fluidized to rise, and then discharges from a cyclone 7. The pulverized ore K in the riser 5 of the preliminary reduction equipment 1 is preliminarily reduced in the form of a fluidized bed by the exhaust gas G from the smelting reduction furnace 2 and the put into the smelting reduction furnace 2 as a preliminarily reduced ore RK. Coal materials having different properties, such as coal, char and coke are added from coal material feeding equipment for reforming exhaust gas 10 according to the degree of oxidation and temp. of the exhaust gas G to increase the quantity of reducing components, such as CO, H2 and CH4 in the exhaust gas and simultaneously to decrease the temp. of the exhaust gas to about 900 deg.C which is suitable for the preliminary reduction of an iron ore, and also added to the smelting reduction furnace as an ore with a high preliminarily reducing rate.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for reforming exhaust gas from a smelting reduction furnace for use in preliminary reduction of ore.

0002

[Prior Art] Conventionally, there has been a smelting reduction equipment that connects a fluidized bed reduction device for pre-reducing fine ore and a smelting reduction furnace that melts and reduces the ore that has been pre-reduced to about 30% by this reduction device. be.

[0003] In such equipment, the exhaust gas generated in the smelting reduction furnace is introduced into a fluidized bed reduction device, where it is often used as a reducing gas for preliminary reduction that functions as a fluidizing gas.

[0004] The appropriate temperature for the reducing gas used for this preliminary reduction is about 900°C, whereas during the oxygen injection operation in the smelting reduction furnace, the temperature of the exhaust gas near the furnace mouth is 2.
Temperatures may exceed 000°C. Therefore, in order to utilize this exhaust gas as a reducing gas for preliminary reduction, cooling is required.

As means for cooling the exhaust gas, there are also known methods such as cooling the exhaust gas using a heat exchanger such as a boiler, and lowering the temperature of the generated exhaust gas by introducing a coolant into the furnace.

On the other hand, when this exhaust gas is used as a reducing gas for a preliminary reduction furnace, the temperature must be adjusted and its oxidation degree (OD (%) = (CO2 + H2 O) / (CO
+CO2 +H2 +H2 O) ×100), that is, it is necessary to increase the amount of CO and H2 in this exhaust gas to improve the ability to reduce the ore.

[0007] For this reducing gas conversion, a method in which solid coal is directly charged into the furnace to convert the gas and lower the exhaust gas temperature to an appropriate temperature is also disclosed in JP-A-62-60806. has been done.

This method of charging solid coal improves the exhaust gas from the smelting reduction furnace, simultaneously reduces the pre-reduced ore, serves as a melting heat source for the charge, as a reducing agent for molten iron oxide, and as a material for carburization. Char, which is a carbon source, can be generated at the same time, and processes such as char conversion, char recovery, and charging can be omitted, which has the advantage of reducing equipment costs and other expenses.However, when performing oxygen injection operation However, there is a problem in that combustion occurs in advance and gas reformation is not performed much, and instead, CO2 and H2 in the exhaust gas increase, reducing reducing ability and reducing suitability as a preliminary reduction gas.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for effectively reforming exhaust gas from a smelting reduction furnace into a reducing gas highly suitable for preliminary reduction.

0010

[Means for solving the problems] The first invention of the present invention is
When exhaust gas from a smelting reduction furnace is used as a reducing gas for preliminary reduction, the carbon material for gas reforming is classified according to the gas reforming ability for the exhaust gas and stored in multiple hoppers, depending on the properties of the exhaust gas. A smelting reduction method characterized in that the amount of carbon material for gas reforming cut out from each hopper is adjusted to adjust the gas reforming ability, and the carbon material is introduced into the exhaust gas to adjust the degree of oxidation of the exhaust gas. This is a furnace exhaust gas reforming method, and the second
In the invention, a plurality of types of carbon materials for gas reforming are stored in a smelting reduction furnace that supplies exhaust gas to a pre-reduction device, a plurality of hoppers equipped with a cut-out device to the exhaust gas passage, and an exhaust gas provided in the exhaust gas passage. A smelting-reduction furnace characterized by being provided with a property detection device and an arithmetic control device that adjusts the amount of carbon material cut out from the hopper to the exhaust gas passage based on the gas property detection information from the exhaust gas property detection device. This is an exhaust gas reformer.

[0011] Furthermore, in the third invention, when the exhaust gas of the smelting reduction furnace is used as the reducing gas for preliminary reduction, the exhaust gas is reduced by charging carbon material for exhaust gas reforming from a plurality of hoppers provided in the smelting reduction furnace. After reforming, the exhaust gas contains volatile components from the reforming carbon material, as well as coal, coke, char, etc.
A method for reforming exhaust gas in a smelting reduction furnace, characterized in that a carbonaceous charging flux is introduced to lower the temperature of the reformed gas, and the cooled reformed gas is supplied to a preliminary reduction device, and the fourth method is The invention provides that when exhaust gas from a smelting reduction furnace is used as a reducing gas for preliminary reduction, carbon substances are introduced into the exhaust gas to reform the exhaust gas, and the exhaust gas is subjected to preliminary reduction together with the carbon substances in the reformed exhaust gas. This is a method for reforming exhaust gas in a smelting reduction furnace, which is characterized by charging the subsequent ore, lowering the temperature of the reformed gas, and further increasing the degree of reduction of the pre-reduced ore and supplying the pre-reduced ore to the smelting reduction furnace.

[0012] In a fifth invention, in the second invention, one of the hoppers contains coal with little vaporized matter (VM), coke with almost no vaporized matter (VM), or char recovered by a hot cyclone or the like. The temperature of the gas can be determined by storing the cooled material and injecting it into the flue gas of gas reforming coal from another hopper upstream of the preliminary reduction furnace introduction gas property detection device and the hot cyclone. This is an exhaust gas reforming method in a smelting reduction furnace that mainly adjusts the

[0013]

[Operation] Gas reforming by coal injection includes the following gasification reactions.

■Coal → H2, Cm Hn, C -1000kc
al reaction (1) (carbonized pyrolysis reaction) ■C+2H2 →CH4 +17900 kcal
Reaction (2) (
Methane production reaction by hydrogenation of char) ■C+H2O
→CO+H2 -31400 kcal
Reaction (3) (char water gas,
Reaction heterogeneous system)■C+2H2 O→CO2 +2H2
-18200 kcal reaction (4)
(Char water gas, reaction heterogeneous system) ■C + CO2
→2CO -38200 kcal
Reaction (5) (Generating Furnace Gas Reaction) Among these, "thermal decomposition" shown in reaction (1) is known to result in carbonization pyrolysis when heated to a relatively low temperature of 350° C. or higher. By thermal decomposition, CH4, CO, H
2, liquid components such as cracked oil and tar represented by Cm Hn, and solid components such as char represented by C. High-temperature carbonization for the purpose of complete gasification is carried out at 700°C or higher to reduce oil and tar content.
It is known to improve the gasification rate.

[0015] Since the methanation of char in reaction (2) occurs at a lower temperature than the reaction formula (for example, 700°C or less) and under conditions where hydrogen partial pressure is high, it is considered that the exhaust gas from the smelting reduction furnace is used in the pre-reduction furnace. In case, the gas temperature after reforming is about 1000
Since the target temperature is ~1200°C, this cannot occur as a main reaction.

It is said that when the gasification temperature is at a high temperature of 1,100°C or higher, reaction (3) is the main reaction, and at a gasification temperature of 1,000°C or lower, reaction (4) coexists and begins to produce CO2. The equilibrium composition of the water gasification reaction of reaction (3) is 1100~
In the range of 1200℃, the composition becomes only CO and H2,
It is known that the gas composition does not change even if the temperature is raised higher than that.

As an explanation of the above phenomenon, FIG.
Figure 3 shows the temperature and equilibrium gas composition at each pressure of carbon (char), oxygen, and water vapor conducted at Urgi Corporation, and the equilibrium composition of the water gasification reaction and the generator gas reaction. Furthermore, Table 1 shows the equilibrium constants of the gasification reaction.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

On the other hand, FIG. 4 shows the initial gasification reaction rate of coal/char during thermal decomposition, combustion, and gasification by Wen. Using these reference data, in order to effectively reform the exhaust gas from the smelting reduction furnace, we set multiple carbon material addition positions, taking into consideration the properties and size of the gas reforming carbon material that is suitable for the exhaust gas temperature. This is what you set.

As mentioned above, FIG. 4 is a diagram showing the initial reaction rate during thermal decomposition, combustion, and gasification of coal and char. As is clear from the figure, the thermal decomposition reaction of coal is equivalent to combustion with oxygen. ends instantly at a speed of On the other hand, the reaction between the generated char and CO2 and H2O slows down as the temperature decreases, making it less effective as a gas modifier.

[0023] Therefore, gas reforming by coal injection is
Cm Hn and CO2 volatilized from coal by pyrolysis
, H2O, and reactions with char and soot cannot be expected.

On the other hand, under the same exhaust gas conditions, the smaller the coal particle size, the faster the heating rate of the coal particles, and the larger the surface area (specific surface area) per unit coal weight. It has become clear that the amount of gas reforming increases, and if the coal is of the same type, the smaller the particle size of the coal added by blowing, the higher the gas reforming ability.
It can be said that the larger the particle size, the lower the modification ability.

Therefore, in the present invention, coal with high volatility and small particle size is used as a reforming agent for the exhaust gas from the smelting reduction furnace. The reforming efficiency of the exhaust gas changes depending on the gas properties such as exhaust gas temperature and exhaust gas composition, and the amount of exhaust gas, so the coal is classified and stored in advance according to its exhaust gas reforming ability (volatility and particle size are dominant). In order to maintain this exhaust gas reforming efficiency at a high level, the type of coal is selected from among the classified coals according to the properties of the exhaust gas, and at the same time, the supply amount, input speed, etc. are set, and the A predetermined amount of coal is supplied and the exhaust gas is reformed.

[0026] In the case of a normal smelting reduction furnace, 16
As a result of experiments, it has been confirmed that the particle size of coal used as an exhaust gas modifier is 2 to 5 mm in a temperature range of 00° C. or higher.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram schematically showing an example of a melt reduction process for carrying out the present invention.

The exhaust gas G from the smelting reduction furnace 2 is introduced from the hot cyclone 4 provided upstream of the fluidized bed pre-reduction device 1 from the flue 3 into the riser pipe 5 of the fluidized bed pre-reduction device 1, and is then introduced into the riser pipe 5 of the fluidized bed pre-reduction device 1. After being reduced while flowing upward, it passes through a cyclone type solid-gas separator located above a downcomer pipe 6 connected to a riser pipe 5, and then is discharged via a cyclone 7 provided downstream of the fluidized bed preliminary reduction equipment 1. Ru.

The ore K introduced from the ore charging section 8 at the lower part of the riser pipe 5 of the fluidized bed pre-reduction device 1 is formed into a fluidized bed by the exhaust gas G from the smelting reduction furnace 2 and is then discharged from the riser pipe 5. While circulating at high speed in the downcomer pipe 6, it is partially reduced,
The partially reduced ore RK is charged into the melting reduction furnace 2 from the top. Pre-reduced ore RK charged into smelting reduction furnace 2
The carbon material and flux are separately charged from the upper part of the melting reduction furnace, and the oxygen and bottom blowing are blown into the slag layer S by the oxygen lance 9 from above the slag layer S formed with the char CH separated in the hot cyclone 4. Refined by stirring gas.

10 is a carbon material supply device for gas reforming,
It has hoppers A, B, C, D, and E for separately storing five types of coal classified with different volatile contents. In order to reduce the negative impact on the bath composition, the hopper where the coal with the lowest thermal decomposition ability is classified is filled with quicklime, fluorite, dolomite, etc., which have the effect of reacting with components that do not contribute to gas reformation and turning into slag. It is preferable that a flux material of 100% is mixed with the coal.

[0031] Classified coal TA, TB,
The charging position of the TC is changed depending on the thermal decomposition ability of the volatile content of each coal, and there are three charging ports 11, 12, 13 in accordance with the temperature of the exhaust gas from the smelting reduction furnace 2.
is provided.

[0032] The first input port 11 is provided near the hot cyclone 4, and the position of the input port is between the second and third input ports.
Since the gas temperature is lower than that at the input port, even though it is possible to decompose the VM in the carbonaceous material, the gasification of the generated char does not proceed. Therefore, in order to provide the main function of gas temperature adjustment, the carbon materials used are those with a low VM rate,
In some cases, it is desirable to use coke or char recovered by the hot cyclone 4. On the other hand, in terms of size, the unreacted char after thermal decomposition is
It is desirable that they be separated by On the other hand, the melting point of ash in the carbonaceous material is the final gas temperature after reforming of 1000 to 12
It is desirable that the temperature is higher than 00°C and that it does not liquefy.

The second inlet 12 is disposed at approximately the same position as the inlet for the pre-reduced ore near the furnace mouth of the smelting reduction furnace 2, or closer to the furnace body than the same position. Since the gas temperature of the carbon material introduced at this position is still high, the VM
Since the rate is good and the char gasification reaction can be fully expected, there are relatively no restrictions in terms of size. That is,
The gasification of char may be performed from the input position to the hot cyclone 4. However, it is preferable for the gasification reaction of the char to be completed upstream of the first input port 11 in terms of gas temperature control, and experimental results have confirmed that the upper limit particle size is 2 to 5 mm.

On the other hand, is it possible that carbonaceous materials that are large in size and cannot be blown away by the flow rate of the exhaust gas from the smelting-reduction furnace fall into the furnace, and that the ash content in the carbonaceous materials can also be liquefied and dripped into the furnace?
The aim is to collect it in the hot cyclone 4 while it is attached to the solid carbon material.

The original aim of this injection position was to reduce the temperature distribution and gas flow rate deviation of the exhaust gas passing through the furnace mouth by adjusting the position (height level) and circle of the third injection port 13 as shown below. The purpose is to differ from both circumferential positions. Therefore, part or most of the gas reforming carbonaceous material inputted from the second input port 12 can also be inputted from the third input port 13.

Furthermore, depending on stricter size constraints and the VM level of the carbon material, it is also possible to use it as the carbon material for the first input port 11. In this case, the third input port 1
It is not desirable to use the same carbon material as No. 3 because it places restrictions on all of the reforming carbon materials.

[0037] The third inlet 13 opens into the furnace mouth of the melting reduction furnace 2, and is for injecting carbonaceous material into the position where the exhaust gas temperature is the highest. As a carbon material, even if unreacted char falls into the furnace after thermal decomposition, it will not go to waste because it will enter the slag layer and be used for the metallurgical reaction inside the furnace. Therefore, the size of the carbon material is relatively large, "lump carbon material" is 5m.
It is also possible to use more than m. On the other hand, from the perspective of maximizing the effective use of gas sensible heat, carbonaceous materials with a high VM rate are desirable. On the other hand, the higher the VM rate, the greater the endothermic reaction, which is also effective in protecting the furnace inner wall refractories from high-temperature gases.

[0038] In the above explanation, the classification of carbonaceous materials for gas reforming according to their gas reforming ability was done by VM ratio classification, but as mentioned above, since the reforming ability differs depending on the particle size of the carbonaceous material, Classification by particle size may be used, or VM rate classification and particle size classification may be used together.

Reference numeral 14 is a device for detecting the gas flow rate, gas composition and temperature, which is installed at the gas inlet of the pre-reduction furnace 2. In order to achieve this, by selecting the most effective classified coal and controlling its input amount, it becomes possible to reduce the coal consumption rate close to the theoretical value. Amount of exhaust gas generated,
Since the gas composition, temperature, etc. change according to a substantially constant pattern, it is also possible to automatically control the introduction of the carbonaceous material for gas reforming, taking this change pattern into consideration in advance.

[0040]

[Effects of the Invention] The following effects can be achieved by the present invention.

(2) The temperature of the exhaust gas from the smelting reduction furnace is lowered and the gas components after gas reformation can be stably obtained.

[0042] According to the above results, the reduction rate of the ore can be stabilized in the preliminary reduction furnace. On the other hand, since the reduction rate of the ore is stabilized, the operation of the smelting reduction furnace is also stabilized.

(2) The temperature of the reducing gas introduced into the preliminary reduction furnace can be controlled with less influence on the composition of the reducing gas, especially on the degree of oxidation (OD).

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of a system for explaining the invention.

FIG. 2 is an explanatory diagram of the relationship between temperature and equilibrium gas composition at each pressure of carbon (char), oxygen, and water vapor.

FIG. 3 is an explanatory diagram of the relationship between the water gasification reaction and the equilibrium composition.

FIG. 4 is an explanatory diagram of the initial gasification reaction rate of coal/char during pyrolysis, combustion, and gasification.

[Explanation of symbols]

1 Fluidized bed preliminary reduction device 2 Melting reduction furnace 3 Flue 4 Hot cyclone 5 Rising pipe 6 Downcoming pipe 7 Cyclone 8 Ore charging section 9 Oxygen lance 10: Carbon material supply device for gas reforming 11, 12, 13 For reforming Coal input port 14 Gas property detection device A, B, C, D, E Hopper

Claims (5)

[Claims] [Claim 1] When exhaust gas from a smelting reduction furnace is used as a reducing gas for preliminary reduction, carbon materials for gas reforming are classified according to gas reforming ability for the exhaust gas and stored in a plurality of hoppers, respectively. The amount of carbon material cut out from each hopper for gas reforming is adjusted according to the properties of the exhaust gas to adjust the gas reforming ability, and this is then added to the exhaust gas to adjust the degree of oxidation of the exhaust gas. Features of a method for reforming exhaust gas in a smelting reduction furnace. [Claim 2] A plurality of types of gas-reformed carbon substances are stored in a smelting reduction furnace that supplies exhaust gas to a pre-reduction device, and a plurality of hoppers equipped with cut-out devices to the exhaust gas passage, and an exhaust gas provided in the exhaust gas passage. A smelting-reduction furnace characterized by being provided with a property detection device and an arithmetic control device that adjusts the amount of carbon material cut out from the hopper to the exhaust gas passage based on the gas property detection information from the exhaust gas property detection device. exhaust gas reformer. [Claim 3] When using the exhaust gas of the smelting reduction furnace as a reducing gas for preliminary reduction, the exhaust gas is reformed by charging carbon material for exhaust gas reforming from a plurality of hoppers provided in the smelting reduction furnace. In addition to the volatile matter from the reforming carbon material, carbonaceous charging flux such as coal, coke, and char is injected into the subsequent exhaust gas to lower the temperature of the reformed gas, and this cooled reformed gas is pre-reduced. A method for reforming exhaust gas in a smelting reduction furnace, characterized by supplying the exhaust gas to a device. 4. When using the exhaust gas of the smelting reduction furnace as a reducing gas for preliminary reduction, carbon substances are introduced into the exhaust gas to reform the exhaust gas, and the exhaust gas after reforming contains the carbon substances together with the carbon substances. Inject the ore after preliminary reduction, cool the reformed gas,
A method for reforming exhaust gas in a smelting reduction furnace, which further comprises supplying the preliminary reduced ore to the smelting reduction furnace after further increasing its degree of reduction. 5. In claim 2, one of the hoppers stores coal with little vaporized matter (VM), coke with almost no vaporized matter (VM), or cooled char recovered with a hot cyclone or the like, A smelting reduction furnace that mainly adjusts the gas temperature by injecting gas reforming coal from another hopper into the exhaust gas upstream from the preliminary reduction furnace inlet gas property detection device and the hot cyclone. Exhaust gas reforming method.