JPH0645828B2 - Agglomeration method of baked pellets - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving the properties of pellets, which are blast furnace charges, and more specifically, solves the drawback that the pellets are spherical and have a small angle of repose and tend to roll. For agglomeration of fired pellets.

Conventional technology and its problems Currently, pellets, sinter, lump ore, etc. are used as blast furnace charges, and among them, pellets have high reducibility and good reduction powderability, It is an excellent raw material with high production yield.

However, since the pellets are spherical, they roll more easily than other raw materials (the angle of repose measured by the injection method is about 30 degrees for pellets, about 35 degrees for sinter, and about 36 degrees for lump ore. is there). For this reason, the distribution tends to be non-uniform inside the blast furnace, and it may be difficult to use a large amount because it may disturb the gas flow and destabilize the furnace condition. This is the current situation.
Therefore, if the drawback of the pellet that it rolls easily and the angle of repose is small is improved, it is possible to increase the blast furnace charging amount of the pellet having the excellent properties as described above.

Therefore, many techniques for improving the shape of pellets have been conventionally proposed.

For example, at the stage of so-called green pellets before firing,
A method in which a powdery mixture of carbonaceous material and silica is sprinkled on the surface of the green pellets, and a plurality of pellets are combined by the slag on the surface of the pellets generated during the firing to form an agglomerate (Japanese Patent Publication No. 58-53697). JP-A-58-
No. 185726), or a method in which green pellets are granulated into a two-layer structure so that the surface layer has a high basicity and then fired, and the pellets are adhered to each other with the slag generated on the pellet surface ( JP-A-61-201
No. 710) and the like.

However, these methods have a problem that the granulation cost increases because the granules must be granulated to have a two-layer structure while adjusting the components of the surface layer at the stage of green pellets. Moreover, since the surface layer of the green pellets is melted during firing, it is inevitable that the green pellets adhere to the kiln, which tends to hinder the operation of the kiln.

Furthermore, since imported pellets, which make up the majority of the pellets, have already been fired, it is not possible to perform the above-mentioned treatment.Therefore, it is difficult to roll the spherical pellets by rolling them. Method (JP-A-51-138)
However, in this method, since the generation of powder at the time of crushing is accompanied to some extent, the advantage of high yield in pellet production as described above is diminished, and the generated powder is not recovered. There is a problem that it has to be solved.

The present invention is intended to solve the above-mentioned problems of the prior art and propose a method for agglomerating fired pellets, by which pellets for blast furnace charging having a large angle of repose can be obtained by an inexpensive and reliable means.

Means for Solving the Problems The method for agglomerating fired pellets according to the present invention is characterized in that the fired pellets are used as a bedding floor of a sintering machine, a plurality of fired pellets are bonded to each other, and the repose angle is increased ( The first invention), and a compounding material obtained by adding one or two kinds of CaO source and SiO ₂ source to the fired pellets is used as a bedding of a sintering machine, and a plurality of fired pellets are combined to increase the angle of repose. (Second invention), coke is added to the fired pellets, and one or two of CaO source and SiO ₂ source is further added.
The compounding material containing seeds is used as a floor covering of a sintering machine, and a plurality of fired pellets are combined to increase the angle of repose (third invention).

Next, the method of the present invention will be described in detail with reference to the drawings.

1 and 2 are schematic views showing one embodiment of the present invention, FIG. 1 is a sectional view of a sintering machine showing a state after sintering, and FIG. 2 (a) is a dotted line portion in FIG. Enlarged view (near Great), 2nd
The figure (b) shows an agglomerated fired pellet.

That is, when the fired pellets 1 are placed on the sinter machine grade 2 as a bedding to a predetermined thickness and the sintering compounding raw material is placed thereon and sintered, the sintered cake 3 is generated, and the voids 6 are provided therebetween. Is formed. As the lower layer of the sintering bed becomes overheated and the temperature rises, the raw material melts well, so Fig. 2 (a)
As shown in an enlarged view of the vicinity 5 of the Great, a melt 4 of the raw material for compounding (hereinafter referred to as "dripping slag") droops on the portion of the fired pellet 1 on the Great 2, and this drooling slag serves as a binder. As a result, the fired pellets 1 are joined together to form a nodule (FIG. 2B).

In a normal operation of a sintering machine, the dripping slag adheres the grate 2 and the sintered cake 3 to each other and hinders smooth mine drainage. In addition, a so-called bedding with a thickness of about 5 cm of sinter ore or the like having a particle size of about 10 mm is laid to prevent the Great 2 and the sintered cake 3 from adhering to each other.

The present invention conversely makes effective use of the drooping slag having such a bad effect, and uses the drooping slag as a binder for binding the fired pellets. Therefore, according to this method, the fired pellets are agglomerated and become hard to roll, so that fired pellets having a large repose angle can be obtained.

The reason why the pellets used in the present invention are limited to the fired pellets is that the fired pellets have higher strength than the green pellets and do not collapse during operations such as transportation to the floor hopper and charging on the grate. As the fired pellets satisfying such strength, for example, fired imported pellets such as algarobo, savage, nibrasco, carroll, weiera, hamaslei, lobe river are preferable.

The layer thickness of the fired pellets is to prevent the seizure between the Great 2 and the sintered slag 3, which is the original function of the bedding, to prevent the raw materials from falling through the gaps between the Great 2 and to prevent the non-agglomeration of the fired pellets. It is preferable to adjust to an appropriate value in consideration.
That is, if the layer thickness is too thin, it is not possible to prevent seizure of the grate and the sintered cake due to slag, and it is not possible to prevent the raw material from falling through the gap of the grate 2, and if the layer thickness is too thick, Since the amount of slag is limited, the number of fired pellets that cannot be agglomerated increases, and the fired pellets that have not been agglomerated segregate inside the sinter storage tank, making it impossible to evenly cut them out. This is because they are mixed and charged into the blast furnace, which causes disturbance of the furnace condition.

The coke ratio and production rate are the layer thickness of the fired pellets to prevent seizure between the grate and the sintered slag, which is the original function of bedding, to prevent the raw material from falling through the gaps in the grate, and to prevent unagglomeration. It has been confirmed by experiments that the thickness is preferably about 2 to 6 cm, though it is somewhat affected by the sintering operation conditions such as.

Examples of the binder to be mixed with the calcined pellets include CaO sources such as lime powder, quick lime, nickel slag, return mineral powder, and serpentine, and SiO ₂ sources.
The O ₂ sources are blended into the calcined pellets individually or simultaneously, and the compounding amount is preferably in the range of about 5 to 6% or less with respect to the calcined pellets. So that it adheres well.

The fired pellets containing these are loaded onto a grate to make a bedding, and the waste heat from the sintered ore on this bedding is used to melt these binders and combine the fired pellets to drop the slag. In addition to this, slag generation is promoted to agglomerate the fired pellets, and therefore the fired pellet layer thickness can be made thicker than when the binder is not mixed.

Further, in this case, some coke powder can be blended in the fired pellet together with the binder as a heat source for melting the binder, and it is possible to adjust the particle size of the binder to be small and facilitate the melting. It is the preferred means of promoting pellet agglomeration.

When adding a binder or coke to the baked pellets, add a small amount of water around 3% as a guide, and the binder and coke will adhere well to the baked pellets and will be blown off before baking by suction with a blower. It is preferable because it does not occur.

Charging of the fired pellets onto the grate can be carried out using a bedding hopper as in the case of forming an ordinary bedding.

Next, an example in which the present invention is applied to an actual machine will be described below.

Example 1 Using a sintering machine having a nominal capacity of 10,000 T / D, imported pellets (savage) were layered to a thickness of about 5 cm (weight: 71 kg / m ² ).
As the floor bedding of the above, and the raw materials for sintering as shown in Table 1 are charged on it, the total layer thickness is 500 mm, the negative pressure is 1800 mmA.
Sintered with q.

The ratio of nodular pellets recovered from the mine, namely,
The agglomeration rate was expressed as an agglomeration rate = 100 x {1- (amount of un-agglomerated pellets / amount of charged pellets)}% (the amount of un-agglomerated pellets refers to the amount of single pellets that are not agglomerated) and investigated As a result, the agglomeration rate is 9
It was about 0%.

Also, the angle of repose was measured by the injection method for pellets formed by combining two or more pieces into a nodule, and the result was 36 degrees, +5 mm
It was not inferior to the sinter ore (repose angle of about 35 degrees) and lump ore (repose angle of about 36 degrees).

Furthermore, the obtained pelletized pellets account for 15% of the blast furnace charging raw material (remaining 80% is sinter ore, 5% is lump ore).
Table 2 shows the operating status of the blast furnace when used in the above. The furnace is used according to the increase in the ratio of nodular pellets compared to the base time when the pellets are used without any treatment. The situation was stable and the fuel ratio also dropped.

Fig. 3 shows the results of measuring the nodulation rate by changing the charging amount of bedding.

That is, if it is 2 cm or less, seizure of the grate and the sintered cake occurs, and if it is 6 cm or more, there are many fired pellets that are not agglomerated, and unaggregated pellets segregate inside the sinter storage tank, resulting in a uniform blast furnace. The raw materials could not be cut out, and those with different repose angles were charged into the blast furnace in a mixed state, making the furnace conditions unstable.

Example 2 Limestone that is a CaO source as a binder (average particle size 1.2 m
m) was used to prepare calcined pellets (savage) in which the amount of limestone added was changed, and the nodulation process was performed in the same manner as in Example 1. The relationship between the amount of limestone added and the rate of nodule
Shown in the figure.

As a result, it was confirmed that the agglomeration rate could be increased by adding up to about 6% to the fired pellets. When blending the binder, water corresponding to half the blending amount of the binder was added.

It was confirmed that the furnace conditions when using the obtained agglomerated fired pellets could be improved similarly to those shown in Table 2.

Example 3 FIG. 5 shows the result of carrying out the same agglomeration treatment as in Example 2 by using CaO source and return ore (average particle size 2.1 mm) which are SiO ₂ sources as the binder.

From the results shown in Fig. 5, when the return ore was used, the nodularization rate could be gradually increased with the compounding amount up to about 4%. It was also confirmed that the furnace conditions when using the obtained agglomerated and fired pellets could be improved similarly to those shown in Table 2.

Example 4 1.5% of limestone (average particle size 2.5 mm) as a CaO source of a binder and 1.0% of Ni slag (average particle size 1.1 mm) as a SiO ₂ source were added to a calcined pellet (Nibrasco). Then, the nodulation process was performed in the same manner as in Example 1.

As a result, an agglomeration rate of 90% was obtained, and the furnace conditions were good when used in a blast furnace.

Example 5 2% of CaO source and return ore (average particle size 2.3 mm), which are a source of SiO ₂ , was added to calcined pellets (argarobo), and further 3 parts of coke (average particle size 0.54 mm) was added.
FIG. 6 shows the result of performing the nodulation process in the same manner as in Example 1 with the bedding having a composition of up to 100% sequentially added, and the amount of water added to the bedding being the same weight as the coke.

From the results of FIG. 6, it was confirmed that the agglomeration rate increased as the coke content increased as compared with the case without coke composition (dotted line in the figure), and the coke composition promotes agglomeration of the fired pellets. It was also confirmed that the furnace conditions of the blast furnace using the obtained agglomerated and fired pellets were improved similarly to those in Table 2.

EFFECTS OF THE INVENTION In the present invention, the fired pellets are used as a floor covering of a sintering machine, and further, a binder or coke is mixed and charged as a floor covering to be aggregated into agglomerates. Agglomeration of the fired pellets can be easily performed without complicated treatment such as etc., a fired pellet with a large angle of repose can be obtained, and the properties of the fired pellets as a blast furnace charge can be improved. Play.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a sintering machine showing a state after sintering in an embodiment of the present invention, and FIG. 2 (a) is an enlarged schematic view showing a dotted line portion (near the great) in FIG. , Fig. 2 (b)
4 is a schematic diagram showing agglomerated fired pellets, FIG. 3 is a diagram showing a relationship between the amount of fired pellets charged (horizontal axis) and the agglomeration rate (vertical axis) in Example 1 of the present invention, FIG. Is a diagram showing the relationship between the charging amount (horizontal axis) and the agglomeration rate (vertical axis) of calcined pellets with different limestone compounding amounts in Example 2, and FIG. FIG. 6 is a graph showing the relationship between the amount of the fired pellets charged (horizontal axis) and the nodularization rate (vertical axis), and FIG. It is a figure which shows the relationship between the amount of baked pellets (horizontal axis) and the agglomeration rate (vertical axis). 1 ... Baked pellets 2 ... Great 3 ... Sintered cake 4 ... Dripping slag 5 ... Near Great area 6 ... Void

Claims (3)

[Claims] 1. A method for agglomerating fired pellets, characterized in that the fired pellets are used as a floor covering of a sintering machine, and a plurality of fired pellets are combined to increase the angle of repose. 2. A CaO source or a SiO ₂ source for the fired pellet.
A method for agglomerating fired pellets, characterized in that a bedding material of a sintering machine is used as a seed material or a combination material containing two kinds of fuel, and a plurality of fired pellets are combined to increase a repose angle. 3. Coke is added to the fired pellets, and C is further added.
Agglomeration of fired pellets characterized by increasing the angle of repose by combining a plurality of fired pellets with a compounding material containing one or two kinds of aO source and SiO ₂ source and connecting the fired pellets to each other. Method.