KR100376506B1 - Method for agglomerating iron ore fines for coal based iron making using waste sludge - Google Patents

Abstract

The present invention relates to a method for agglomeration of finely reduced reduced iron by mixing waste sludge with finely reduced fine iron reduced in the preliminary reduction furnace in manufacturing molten pig iron in a molten iron production apparatus consisting of a fluidized bed preliminary reactor and a melt gasification furnace. The present invention relates to agglomeration of finely-reduced iron by using the coking force of carbonaceous material and reduced iron in the sludge at high temperature, which not only makes the process simple but also makes effective use of waste sludge and also improves the recovery rate of iron contained in the sludge. It is to provide a method of bulking finely reduced iron using sludge, which has its purpose.

The present invention is a method for producing molten pig iron by charging the finely reduced reduced iron pre-reduced in a fluidized bed reduction furnace in a molten gasifier, by mixing the sludge with the finely reduced iron, agglomerated the finely reduced reduced iron and charged into the molten gasifier. The grating method of finely-reduced iron for manufacturing molten iron using the main point is made.

Description

Mass refinement method of finely-reduced iron for manufacturing molten iron using sludge {METHOD FOR AGGLOMERATING IRON ORE FINES FOR COAL BASED IRON MAKING USING WASTE SLUDGE}

The present invention relates to a method for producing molten pig iron by using a ferrous iron ore in the molten iron manufacturing apparatus consisting of a fluidized bed pre-reduction reactor and a melt gasification furnace, more specifically, consisting of a fluidized bed pre-reduction reactor and a melt gasification furnace In manufacturing molten pig iron in a molten iron manufacturing apparatus, the present invention relates to a method of massifying finely reduced iron by mixing waste sludge with the finely reduced fine iron reduced in a preliminary reduction furnace.

As a method of manufacturing molten iron, a method of melting iron ore reduced by using a blast furnace method and a shaft furnace in an electric furnace has been conventionally employed. In the blast furnace process, re-dust prevention and To ensure breathability, it is charged into the blast furnace in the form of coke and sintered ore with a certain strength and size.

For this reason, the blast furnace method requires not only pre-treatment facilities such as coke oven facilities and sintering ore manufacturing facilities for carbonizing strong coking coal, but also requires a lot of energy during sintering.

Therefore, the blast furnace method requires enormous equipment investment costs, and moreover, strong coking coal, a raw material for producing coke, has a small amount of coke in the world.

Currently, about 80% of the reserves of iron ore are present in the form of iron ore with a particle size of 8mm or less, and the molten iron reduction iron method using the fluidized bed which can directly use the iron ore and coal powder without pretreatment is greatly highlighted as the next generation steelmaking process. In recent years, R & D is actively being carried out all over the world such as Europe, Japan and Korea.

The melt reduction process consists of a preliminary reduction process for reducing iron ore to a reducing gas of CO + H ₂ , which is a natural gas or coal gasification component, and a molten reduction process for melting and finally reducing the reduced ore.

The preliminary reduction process requires a process to allow the omission of the sintering process by using the ferrite ore with a large particle size distribution directly without pretreatment such as sinter ore and pellet ore which are used as raw materials of iron in the existing blast furnace process. Lose.

Therefore, it is expected that significant cost savings can be achieved by eliminating the auxiliary facilities in the intermediate process step that overcomes the constraints of raw materials and directly using the iron ore.

In gas reduction of such iron ore, the fluidized bed method is essential to ensure air permeability, uniform temperature distribution in the reactor, and to increase reactivity by increasing the contact area of gas and solid.

Representative processes for reducing iron ore using a fluidized bed currently being developed as a commercialization process include DIOS in Japan, HISMELT in Australia, FIOR Process in Venezuela / Austria, and FINEX method in Korea.

In such a melt reduction method, a method of producing molten pig iron by charging reduced iron reduced in a fluidized bed preliminary reduction furnace into a melt gasifier is employed.

In the melting reduction of the iron ore as described above, in the case of gravity input of the reduced iron discharged from the fluidized-bed reduction reactor to the melt gasifier, the high-speed rise flow of the reducing gas generated and discharged by the gasification of coal in the upper portion of the melt gasifier and At the same time, the concentration of fine iron ore in the flue-gas is increased due to the scattering of heavy and fine reduced iron, and the cyclone load is severe.

In order to solve the above problems, US Pat. No. 4,978,387, Korean Patent Application No. 87-12076, and Japanese Patent Laid-Open No. 62-224620 use a transport gas and a burner as a method of injecting fine reducing iron into a melting furnace.

However, this method requires not only a huge amount of gas for transporting the reduced fine iron ore from the fluidized bed from the outlet to the burner inlet, but also requires frequent replacement of the burner gas due to severe wear of the fine iron ore around the burner. Re-dusting of the powder by blowing causes dust to be introduced into the preliminary reduction reactor, which leads to blockage of the reduction plate distribution plate or adhesion to the fluidized bed furnace wall, which causes enormous disruption in equipment and operation time.

In addition, Japanese Patent Application Laid-Open Nos. 1-116035, 1-119631, 1-188635, and 1-252714 have a coal mixed briquette ore and the mixture is produced by cold or hot forming. Has been proposed to inject a gas into a melt gasifier.

In these methods, additional equipments such as molding machines to bulk the mixture should be separately installed, and even allergic ores that can be directly gravity-injected without bulking are mixed together with the fine iron ores so that the porosity of the molding having a wide particle size distribution increases. Briquette compressive strength decreases. This has a problem in that the capacity of the molding machine increases and the carbonaceous material requirements also increase.

On the other hand, Austrian Patent No. 1234/95 proposes a method of gravity charging finely-reduced iron while blowing oxygen through a fluidized bed pre-reduction reactor outlet and a charging pipe connected inside the melt gasifier.

However, this method has high difficulty in developing durable materials that can be used for long time operation in high temperature oxidizing atmosphere and high oxidation rate of reducing gas in the melting furnace due to additional oxygen. There is a problem that causes.

The present inventors have conducted research and experiments to solve all the problems of the conventional method as described above, and based on the results of the present invention, the present invention uses the coking force of carbonaceous material and reduced iron in the sludge at high temperature. By agglomerating finely-reduced iron, the process is not only simple, but it is possible to provide waste sludge usefully, and also to provide a method for agglomeration of finely-reduced iron using sludge which can improve the recovery rate of iron contained in the sludge. There is a purpose.

1 is a block diagram showing a molten iron manufacturing apparatus for producing molten iron using a conventional fluidized bed pre-reduction device

Figure 2 is a block diagram showing a molten iron manufacturing apparatus equipped with a mixer in accordance with the present invention

Explanation of symbols on the main parts of the drawings

20 ... Preliminary reduction furnace 32 ... Medium and fine reduced iron discharge pipe 40 ... Melting gasifier

50 ... mixer 51 ... drain screw 52 ... vibrator 53 ... sludge supply line

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention is a method for producing molten pig iron by charging the finely reduced reduced iron pre-reduced in a fluidized bed reduction furnace in a molten gasifier, by mixing the sludge with the finely reduced iron, agglomerated the finely reduced reduced iron and charged into the molten gasifier. The present invention relates to a method for massifying finely-reduced iron for manufacturing molten iron.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the method of manufacturing molten iron using the iron-iron ore, as shown in FIG. 1, the iron-iron ore is preliminarily reduced in the preliminary reduction furnace 20, that is, the lower part 21 and the medium / fine grain (fine powder) in which alleles exist. After the preliminary reduction in each of the upper portion 22 of the furnace), the reduced iron in the pre-reduced iron ore is charged into the molten gasifier 40 through the allele reduction iron discharge pipe 31 by gravity drop, Reduced iron is charged into the melt gasifier (40) through the medium / fine reduced iron discharge pipe (32) is melt-reduced molten iron is produced.

That is, when reducing the iron ore in the preliminary reduction furnace 20 by the reducing gas generated in the molten gasifier 40, 500 μm or less in the upper part of the furnace 22 based on the particle diameter of 500 μm of the iron ore according to the flow rate Differentials (medium / fine) exist, and in the lower part of the furnace 21, opposition of 500 micrometers or more exists.

At this time, the opposition of 500㎛ or more is gravity-charged into the molten gasifier 40 through the allele reduction iron discharge pipe 31, the fine powder of 500㎛ or less present in the upper portion of the furnace 22 to the molten gasifier 40 without bulking When charged, the cyclone increases the load by increasing the concentration of the fine reduced iron in the exhaust gas due to the re-flying of the reduced iron along with the high-speed ascending flow of the reducing gas generated and discharged by the coal gasification of the upper portion of the melt gasifier (40). As a result, the iron recovery rate is lowered due to an increase in the scattering loss of fines, which lowers the economic efficiency.

Accordingly, the present invention is intended to solve the above problems by charging the finely-distilled reduced iron mixed with the sludge and charging the molten gasifier 40 by using the coking property at the high temperature of the carbonaceous material component and finely-reduced iron in the sludge.

The molten iron manufacturing apparatus provided with an example of the mixer which concerns on this invention is shown in FIG.

As shown in FIG. 2, the mixer 50 of the present invention is installed in the medium / fine reduced iron discharge pipe 32 for supplying the reduced / reduced iron pre-reduced iron in the preliminary reduction furnace 20 to the molten gasifier 40. do.

The mixer 50 is connected to the medium / fine reduced iron discharge pipe 32 so that the upper portion thereof receives the medium / fine reduced iron discharged from the preliminary reduction path 20, one or a plurality of discharge screws 51 at the bottom thereof. And a vibrator 52 are respectively provided.

The sludge supply pipe 53 is connected to the upper portion of the mixer 50.

The vibrator 52 is configured to smoothly dry the charged liquid sludge and to mix the sludge with finely divided iron.

That is, the vibrator 52 is configured to smoothly mix the sludge and finely-reduced iron, so that the agglomeration of finely-reduced iron is smoothly performed.

The screw 51 is configured to discharge the mixture of sludge and finely-reduced iron to the heavy / fine reduced iron discharge pipe 32, so that the mixture of sludge and finely-reduced iron is melted through the medium / finely reduced iron discharge pipe (32) It is supplied to the furnace 40.

As described above, when the mixture of sludge and finely-reduced iron is supplied to the molten gasifier 40 through the medium / fine reduced iron discharge pipe 32, that is, finely reduced iron while moving the heavy / fine reduced iron discharge pipe 32 After being massed by sludge, it is supplied to the molten gasifier 40.

The finely-reduced iron which is agglomerated according to the present invention is finely-reduced iron that is charged into the molten gasifier 40 through the medium / fine particulate iron discharge pipe 32, and the particle size thereof is about 500 μm or less.

However, the present invention is not limited to this.

In addition, the present invention is not limited to the one-bed fluidized bed preliminary reactor shown in FIG. 2, but is also applied to the bulking of the finely-reduced iron which is pre-reduced in the multistage fluidized bed preliminary reactor and charged into the melt gasifier. .

Examples of the sludge that can be applied to the present invention include sludge produced by depositing dust generated in a molten gasifier and final dust generated in a preliminary reduction furnace in a molten iron manufacturing process after preliminary reduction.

Representative processes include the COREX process and the FINEX process.

Sludge which can be preferably applied to the present invention is T. Fe: 5-50%, SiO ₂ : 2-20%, CaO: 3-30%, Al ₂ O ₃ : 2.0-11.5%, MgO: 1.0-3.5%, C: 2-87%, TiO ₂ : 1% or less, P ₂ O ₅ : 1% or less, K ₂ O: 1.5% or less, Na ₂ O: 1% or less, S: 1% or less Sludge to be prepared.

C in the sludge has self-adhesiveness when thermally decomposed, and the greater the amount, the greater the effect. The increase in reducing power due to reducing gas generation and the reduction of the reduced iron in the melt gasifier act as a heat source and reducing gas to reduce the amount of extra coal. Can be reduced.

The amount of sludge mixed with the finely reduced iron is preferably 10-90% by weight.

When the amount of the sludge is less than 10%, it is difficult to secure the compressive strength necessary for falling, because the cohesiveness of the massed mixture is poor.

In addition, when the mixing amount of the sludge is 90% or more, 700-900 ° C. high temperature reduced iron discharged from the upper part of the preliminary reduction furnace is mixed with a large amount of room temperature sludge so that the temperature in the mixer 50 is lowered below 600 ° C. There is a fear that the bulking strength of the reduced iron is lowered, and when it is charged into the molten gasifier, it is re-dusted.

After mixing the finely reduced iron and sludge in the mixer 50, it is preferable to maintain at least 2 minutes in the temperature range of 600-900 ℃.

That is, by mixing the finely reduced iron and sludge while vibrating the vibrator 52 in the mixer 50, which is maintained at a temperature of 600-900 ℃, and maintained for at least 2 minutes, the finely reduced iron has a particle size of approximately 500㎛ or more by the sludge Is agglomerated.

When the holding temperature is 600 ° C. or less or the holding time is less than 2 minutes, the powdered coal is not aggregated well, and thus the compressive strength of the mixture is lowered.

On the other hand, the mass of pre-reduced finely-reduced reduced iron may vary depending on the drop distance and the rise of the gas to the melt gasifier when gravity is charged into the melt gasifier, but it is assumed that the drop height is 10 m in a typical melt gasifier. The preferred compressive strength of the agglomerated powder should be at least about 5kg / cm2.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Experiments were performed using an electric furnace using sludge having a component as shown in Table 1 below and reduced iron having a powder of iron ore 1 mm or less shown in Table 2 as a sample.

Traces of nitrogen (10 ml / min) were fed to prevent reoxidation of reduced iron and combustion of coal.

Sludge composition (Unit: weight%) T.Fe: 25.3%, SiO ₂ : 8.7%, CaO: 8.4%, Al ₂ O ₃ : 5.5%, MgO: 4.1%, C: 43.2%, TiO ₂ : 0.4%, P ₂ O ₅ : 0.3%, K ₂ O: 0.9%, Na ₂ O: 0.5%, S: 0.7% or less, other: 2%

Particle Size Distribution of Iron Iron Ore 0-106 μm: 16%. 106-250 μm: 34%, 250-500 μm: 31%, 500-1000 μm: 19%

The sample used in the experiment was 85% pre-reduced reduced iron, and the sludge and mixing ratio was set to 8: 2 by weight.

After putting the mixed sample in the crucible and putting it in an electric furnace preheated to 800 ° C., the reaction time was 30 seconds, 1 minute, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 25 minutes. , The compressive strength was measured, and the compressive strength of the measured sample is shown in Table 3 below.

Compressive Strength Change with Time Response time (minutes) 0.5 One 2 5 10 15 20 Compressive strength (kg / ㎠) 2 3 5.5 18 14 11 11

As shown in Table 3 above, when the reaction time was less than 2 minutes, the charging minimum compressive strength reached 5 kg / cm 2, and when the reaction time was 5 minutes, the maximum compressive strength was reached. The compressive strength was reduced.

Example 2

Under the same conditions as in Example 1, the reaction time was fixed at 5 minutes and the reaction temperature was changed to 400-900 ° C. to perform the experiment and showed the effect of compressive strength according to the temperature change after the reaction.

The compressive strength of the sample measured at this time is shown in Table 4 below.

Compressive Strength Change with Temperature Reaction temperature (℃) 400 500 600 700 800 850 900 Compressive strength (kg / ㎠) 5.5 7 12 16 18 20 24

As shown in Table 4, as the reaction temperature increases, the compressive strength of the sample after the reaction increases, but the heat loss and the reaction temperature in the real fluidized bed preliminary reactor are performed below 850 ° C. Therefore, 700-850 ° C is most preferable. Able to know.

Example 3

Under the same conditions as in Example 1, the reaction temperature was 800 ° C., the reaction time was fixed at 5 minutes, and the sludge blending ratio was changed to 5-20% by weight.

The compressive strength of the measured sample is shown in Table 5 below.

Compressive Strength Variation According to Sludge Mixing Ratio Compounding ratio (% by weight) 5 10 15 20 25 30 40 Compressive strength (kg / ㎠) 4 12 15 18 25 38 56

As shown in Table 5, as the sludge blending ratio increased, the compressive strength of the sample after the reaction increased, and when the blending ratio was 10% or more, the strength required for charging by melting gasification was obtained, and the compressive strength was above 20%. It can be seen that increases rapidly.

As described above, the present invention not only simplifies the process but also melts the waste sludge by mixing with a reduced iron ore reduced in the fluidized bed pre-reduction furnace at high temperature and charging it into the melt gasifier by the continuous gravity drop method. It is possible to suppress the scattering of the finely-reduced iron in the gasifier and to reduce the iron content contained in the sludge, thereby improving the iron recovery rate.

Claims (2)

In the method for manufacturing molten pig iron by charging the finely reduced reduced iron pre-reduced in the fluidized bed pre-reduction furnace 20 into the molten gasifier 40 through the medium / fine (fine) reduced iron discharge pipe (32), One or a plurality of medium / fine reduced iron discharge pipes 32 and a sludge supply pipe 53 are connected to an upper portion thereof, and a lower portion thereof is configured to discharge a mixture of finely reduced iron and sludge into the medium / fine reduced iron discharge pipes 32. Installing a mixer 50 each having an exhaust screw 51 and one or a plurality of vibrators 52; Supplying 10-90% by weight of sludge to the mixer 50 in the finely reduced iron which is supplied through the medium / fine reduced iron discharge pipe 32; Maintaining the temperature in the mixer 50 at 600-900 ° C. and mixing the finely divided reduced iron and sludge while vibrating the vibrator 52, and maintaining at least 2 minutes to bulk the finely reduced reduced iron; and Using the sludge composed of the fine iron reduced by the sludge as described above discharged to the medium / fine reduced iron discharge pipe 32 through the discharge screw 51 and supplied to the molten gasifier (40) Bulking method of finely-reduced iron for manufacturing molten iron The method according to claim 1, wherein the sludge is T.Fe: 5-50%, SiO ₂ : 2-20%, CaO: 3-30%, Al ₂ O ₃ : 2.0-11.5%, MgO: 1.0- 3.5%, C: 2-43.2%, TiO ₂ : 1% or less, P ₂ O ₅ : 1% or less, K ₂ O: 1.5% or less, Na ₂ O: 1% or less, and S: 1% or less A method of massifying finely-reduced iron for manufacturing molten iron using sludge, which is characterized by the above-mentioned.