JPS63149331A - Production of burnt agglomerated ore - Google Patents

Abstract

PURPOSE:To produce burnt agglomerated ore for iron ore under excellent product yield and productivity by coating and burning the coke powder having the specific grain size on the surface of green pellet, after pelletizing into the green pellet by adding flux in the powdery iron ore. CONSTITUTION:At the time of producing the burnt ore for blast furnace or raw material for directly reducing iron-making from the powdery iron ore, at least one kind of material or more among lime, slaked lime, limestone, bentonite, dolomite, water granulated blast furnace slag, etc., are added as the flux to the granular iron ore having <8mm grain size, so that basicity CaO/SiO2 of the burnt agglomerated ore as the finished product becomes 1.0-2.5, and pelletized into the green pellet by kneading with water. The green pellet having 3-13mm grain size is made by coating the powdery coke having 20-70wt% of <0.1mm grain size and the remaining part of 0.1-5mm grain size thereof and 2.5-4.0wt% ratio to the green pellet. This is burnt by endlessly moving grate type burning furnace, and the burnt agglomerated ore with powdery iron ore is produced under excellent product yield and productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing calcined agglomerates suitable as raw materials for blast furnaces or directly reduced iron.

[Prior art and its problems]

Calcined agglomerate, which is made by pelletizing powdered iron ore and calcining it, is known as a raw material for blast furnaces or direct reduction iron manufacturing.
Its use is expanding.

This calcined agglomerate ore is usually produced as follows.

That is, a solvent consisting of at least one of quicklime, slaked lime, limestone, bentonite, granulated blast furnace slag, dolomite, etc. is added to powdered iron ore with a particle size of about 81 or less,
Ca O/8102 value in calcined agglomerate is 1.0-2
．． Add so that it is about 5% and mix with a mixer. Then, the obtained mixture is supplied to a disk-shaped first granulator, and water is added to the granulator. (2) Then, the mixture is granulated using a first granulator, and formed into green pellets having a particle size of, for example, about 3 to 13 m. Next, the obtained raw pellets are supplied to a second disk-shaped granulator, and the steps 2.5 to 4 are carried out. Approximately Owt% of coke powder is added and the green pellets are further granulated by a second granulator, thereby preparing green pellets whose surfaces are coated with coke powder.

The green pellets thus obtained are charged into an endless moving grate type kiln, and the layer of the charged green pellets is placed on the grate of the kiln, and then placed in the drying zone of the kiln.
Pass through the ignition zone and firing zone in sequence. In the dry zone, the raw pellet layer is heated from above at a temperature of 150 to 350°C.
Blow in drying gas to dry the raw pellets. In the ignition zone, high-temperature combustion gas is blown into the layer of dried green pellets from above to ignite the coke powder on the surface of the green pellets. In the combustion zone, the hot combustion gas produced by the combustion of coke breeze is sucked downward through the green pellet bed to heat the green pellets to the calcination temperature. The green pellets are calcined by heating in a calcining zone into large block-like masses of calcined agglomerates consisting of calcined pellets bound by at least one of calcium ferrite and slag formed on their surfaces.

The large block-shaped lumps of calcined agglomerate thus obtained are discharged from the downstream end of the calcining furnace, crushed by a crusher, and then sieved by a screen. The calcined agglomerate pieces are removed, and the calcined agglomerate ore in the form of a plurality of calcined pellets combined has a maximum particle size of about 50mm, and the particle size of a single calcined pellet is about 3 to 13cm. of calcined agglomerate ore is produced.

The calcined agglomerate ore produced as described above has excellent reducibility, since it mainly contains a large amount of fine calcium ferrite and fine hematite, which have excellent reducibility. In addition, not only in the case of a lump-like shape in which multiple fired pellets are combined, but also in the case of a single fired pellet, it has an irregular shape, so when charged into a blast furnace, Since the reducing gas does not flow biasedly toward the center of the blast furnace, and gaps are formed between the fired agglomerated ores, smooth passage of the reducing gas is not obstructed. Furthermore, even if it collapses due to impact or the like during transportation, the calcined agglomerate, which is a lump of a plurality of calcined pellets combined, will simply separate into a single calcined pellet, so it can be used without any problem.

However, conventionally, as coke powder to coat the surface of raw pellets, particles with a particle size of 5 mm or less were used at 20 to 70 wt%.
Because coke powder with a relatively coarse composition consisting of particles with a particle size of more than 5 m was used, the coke powder did not adhere well to the surface of the raw pellets, resulting in insufficient or uneven coke coverage. There were some drawbacks. For this reason,
When raw pellets are fired in a kiln, the firing is not performed well, and as a result, the yield of fired agglomerates is less than 70%, and the production rate is 1.5 tons/n? There was a low level of problem below -b.

[Purpose of the invention]

In view of the above-mentioned current situation, this invention involves adding a solvent to powdered iron ore, forming the mixture into green pellets, pouring coke powder onto the obtained green pellets, and converting the green pellets into an endless moving grate. When charging into a calcining furnace to continuously produce calcined agglomerates, it is possible to easily achieve high product yields and production rates by selecting the particle size and blending ratio of the coke breeze used to coat the green pellets. The purpose is to produce calcined agglomerate ore.

[Summary of the invention]

This invention involves adding a solvent to powdered iron ore, granulating a mixed mixture to form raw pellets, coating the obtained raw pellets with coke powder, and placing the raw pellets in an endless moving grate type kiln. In a method for producing calcined agglomerate ore in which the coke powder is charged and continuously calcined to continuously produce calcined agglomerate ore, the coke powder has a particle size of 0. IW or less is 20
It is characterized by the use of coke powder with a composition of ~70 wt% and a particle size of more than 0.1 and less than 5, with the remainder being 70% by weight.

[Structure of the invention]

Hereinafter, the method for producing calcined agglomerate ore of the present invention will be described in detail.

The inventors of the present invention formed a mixture of fine iron ore with a solvent additive and mixed it into raw pellets, coated the obtained raw pellets with coke powder, and charged the raw pellets into an endless moving grate type kiln. Therefore, in order to improve the product yield and production rate of calcined agglomerate ore in the continuous production of calcined agglomerate ore, we have repeatedly investigated the coke breeze to be used.

If the blending ratio of fine coke powder increases and the particle size of the coke powder used becomes relatively fine, the coke powder will more easily adhere to the surface of the green pellets. - and can be sufficiently covered,
As a result, it is expected that the raw pellets can be fired satisfactorily in the firing furnace, and the product yield and production rate of fired agglomerate ore can be improved.

Therefore, we conducted an experiment in which the particle size and blending ratio of coke breeze were varied and coated on green pellets to produce fired agglomerate ore, and the product yield and production rate of the fired agglomerate ore were investigated. Ta.

As a result, the particle size was 0. If fine coke powder with a composition consisting of 20 to 70 vt of 1 m or less and the remainder of particle size of 0.1 to 5 fi or less is used to coat raw pellets, the product yield and production rate of calcined agglomerate ore can be greatly increased. It turns out that it can be improved.

Figure 1 shows the relationship between the blending ratio of coke powder with a particle size of 0.1 mm or less in the coke powder with a particle size of 5 mm or less used to coat the green pellets, and the product yield of the obtained calcined agglomerate ore. Similarly, FIG. 2 is a graph showing the relationship between the blending ratio of coke breeze with a particle size of 0.14 or less and the production rate of the obtained calcined agglomerates. In addition, the particle size of powdered iron ore is about 8- or less, the particle size of raw pellets is about 3-13+m,
The amount of coke powder added was 3.5 wt.

As shown in FIG. 1, the particle size is 0. As the blending ratio of coke powder of 1 m or less increases, the green pellets become better covered with coke powder and are sintered better, so the yield per product of calcined agglomerated ore increases, and the blending ratio increases. is 20 wt% or more, the product yield is as high as 75% or more. However, when the blending ratio exceeds 70 wt%, although the product yield exceeds 90%, the rate of increase is small, and the only disadvantage is that the cost of crushing coke breeze increases considerably.

As shown in Figure 2, the production rate of calcined agglomerates increases for the same reason as the blending ratio of coke breeze with a particle size of 0.1 or less increases;
Above vtfy, the production rate is 1.5 tons/rr?・h
That's high. However, if the blending ratio exceeds 50%, the production rate will be 2 tons/? Although it exceeds A and H, the rate of increase is small.

Therefore, the product yield of calcined agglomerate ore should be 75 cm or more, and the production rate should be 1.5 tons/lT?・In order to significantly improve the particle size to 6 or more, the particle size must be 0. IW or less is 20~'70 wt, particle size 0
, l W greater than 5+m, with the balance remaining, should be used for coating the green pellets.

In this invention, as in 1 or above, coke powder is a mixture of 20 to 70 wt% of particles with a particle size of 0.1 mm or less, and the balance of particle sizes of more than 0.1 m and 5III m or less? , used to coat raw pellets, greatly improving the product yield and production rate of calcined agglomerate ore.

In this invention, it is preferable that the amount of coke powder coated on the green pellets is 2.5 to 4.0 wt% as in the conventional method. This means that the amount of coated coke powder is 2.5wt%.
This is because if the amount is less than 4.0 wt, the firing efficiency of the green pellets in the kiln cannot be improved, and the raw pellets cannot be calcined into high-strength calcined agglomerates in a short time. This is because if the temperature exceeds 1, the temperature of the raw pellet during firing becomes too high, and the structure of the fired agglomerate becomes too dense.

In this invention, the particle size of the powdered iron ore used is preferably about 8 grains or less, as in the prior art. This is because powdered iron ore with a grain size of more than 8 grains can be used as is without being converted into agglomerated mineralized by firing, and iron ore powder with a grain size of 8 grains or less needs to be mineralized by fired agglomerates.

In this invention, the particle size of the raw pellets is preferably about 3 to 13 a as in the conventional method. The reason is as follows. Immediately 5. When the particle size of the raw pellets is less than 3 parrots,
During the firing of green pellets in the firing T, the high-temperature combustion gas generated by the combustion of coke powder is prevented from passing through the layer of green pellets, resulting in a reduction in the production rate of fired agglomerate ore. arise. In addition, fired agglomerates in the form of single fired pellets also have a particle size of less than 3 mm (=,
When calcined agglomerate having such a small particle size is charged into a blast furnace, smooth passage of reducing gas is obstructed. the result,
Shelving and slipping occur within the blast furnace, resulting in the problem of unstable blast furnace operation. On the other hand, if the particle size of the green pellets exceeds 13 mm, the resistance to impact becomes weak, resulting in the problem of the green pellets collapsing when transferred to a firing furnace. In addition, when the firing time is short as in this process, heat is not transmitted to the core of the raw pellets, resulting in insufficient heat (higher quality fired agglomerate cannot be obtained. The particle size of the fired agglomerates exceeds 13 m, so when such large calcined pellets of calcined agglomerates are charged into a blast furnace, it takes a long time for the reducing gas to penetrate into the center of the calcined agglomerates. As a result, the reducibility of the calcined agglomerate ore in the blast furnace deteriorates, and unreduced cores remain, resulting in problematic noise that deteriorates the high-temperature properties of the calcined agglomerate under load.

〔Example〕

The fine iron ore having the particle size composition shown in Table 1 and the chemical composition shown in Table 2 and the coarse iron ore having the particle size structure shown in Table 3 and the chemical composition shown in Table 4 were mixed into fine iron ore 4o vt%
, coarse grained iron ore was used at a ratio of 60 wt%, and 2.7 wt% of quicklime-Ji having the particle size composition shown in Table 5 was added as a solvent and a binder, and the resulting mixture was granulated. By doing so, raw pellets having a particle size distribution shown in Table 6 and a moisture content of 8 to 9 wt% were formed.

(WZ CH) (WT CH) Next, 3.5 vt% of coke powder having a composition within the scope of this invention as shown in Table 7 was added to the raw pellets and granulated.
The raw pellets were coated with coke powder. For comparison, green pellets were similarly coated with coke breeze having a formulation outside the scope of this invention, also shown in Table 7.

Then, the green pellets are charged onto the grate of an endless moving grate type kiln to a thickness of f 400 m, and the drying zone 2 ignition zone and the calcination zone of the whole kiln are sequentially moved, and the fired agglomerated ore is heated. It was fired. The large block-shaped calcined agglomerate ore obtained in this way is discharged from the downstream end of the kiln, and after being crushed by a crusher, the calcined agglomerate pieces under the sieve with a particle size of less than 3 are separated by a screen. In this way, calcined agglomerate in the form of a lump with a maximum particle size of about 50 m in which a plurality of calcined pellets are combined and calcined agglomerate in the form of a single calcined pellet with a particle size of about 3 to 13 m are produced. Ta.

The product yield, production rate, reduction rate, and reduction powdering rate of the calcined agglomerate ore produced as described above are as follows.

It was as shown in Table 8.

Table 8 As shown in Table 8, floors 1-
In all cases, the yield of calcined agglomerate ore was 75 inches or more, and the production rate was high, 1.5 tons β·h or more. Also,
The reduction rate is also maintained at 80 degrees or more, and the reduction powdering rate is 25 degrees or less, which is the same as before. In contrast, in Comparison Measurements 4 to 5, in which green pellets were coated with coke powder of a composition outside the scope of the present invention and fired, the product yield of fired agglomerate ore was less than 75 inches, and the production rate was low. 1.5 tons/rr?・h
It was low.

〔Effect of the invention〕

According to the present invention, calcined agglomerate ore can be easily produced at a high product yield and production rate by selecting the particle size and blending ratio of the coke powder used to coat the green pellets.

[Brief explanation of the drawing]

Figure 1 shows the blending ratio of coke powder with a particle size of 0.1 square meters or less in coke powder with a particle size of 5 days or less used for coating green pellets, and the product yield of the obtained calcined agglomerate ore. FIG. 2 is a graph showing the relationship between the blending ratio of coke breeze having a particle size of 0.1 days or less and the production rate of the obtained calcined agglomerate ore.

Claims (1)

[Claims] A mixture of powdered iron ore and a solvent is added and mixed and granulated to form raw pellets, the obtained raw pellets are coated with coke powder, and the raw pellets are fired in an endless moving grate. In a method for producing calcined agglomerate ore, which comprises charging the coke into a furnace and continuously calcining it to thereby continuously produce calcined agglomerate ore, the coke powder has a particle size of 0.1 mm or less and is 20 to 7 mm.
A method for producing calcined agglomerate ore, characterized by using coke powder having a composition of 0 wt% and the remainder having a particle size of more than 0.1 mm and less than 5 mm.