CN119256099A

CN119256099A - Method for producing granulated raw material for sintering and method for producing sintered ore

Info

Publication number: CN119256099A
Application number: CN202380042603.5A
Authority: CN
Inventors: 竹原健太; 山本哲也; 樋口隆英; 广泽寿幸
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2022-06-03
Filing date: 2023-04-25
Publication date: 2025-01-03
Also published as: JPWO2023233871A1; TW202348805A; JP7616523B2; KR20250004310A; EP4506475A1; WO2023233871A1; TWI849926B

Abstract

By studying the suitability of stirring conditions (stirring energy) obtained in consideration of the properties of varying (micronizing, etc.) iron ores, a method has been proposed for improving the manufacturability of sintered ores by using a granulating raw material obtained by this method in order to establish a more advanced manufacturing technique for a granulating raw material for sintering. A method for producing a granulated material for sintering, and a method for producing a sintered ore using the method, characterized in that, when producing a granulated material for sintering by granulating a sinter batch material after stirring at a high speed, the stirring power at the time of stirring at a high speed is adjusted according to the particle size distribution of an iron-containing material in the sinter batch material.

Description

Method for producing granulated material for sintering and method for producing sintered ore

Technical Field

The present invention relates to a method for producing a sintering granulation raw material used in a DL-type sintering machine or the like, and a method for producing a sintered ore using the method.

Background

The sinter is produced by mixing a plurality of kinds of powdery iron ore (generally, a material called a sintering material (SINTER FEED) of about 125 to 1000 μm) with a proper amount of auxiliary raw material powder such as limestone, silica, serpentine, etc., mixed raw material powder such as dust, scale, return ore, etc., and solid fuel such as powdery coke, etc., to form a sintering mixture, adding water to the sintering mixture, mixing, granulating, and charging the obtained granulating material into a sintering machine, and sintering.

In general, the sintering blend materials contain moisture to aggregate with each other and become quasi-particles (quasi-particles) when granulated. In addition, it is known that this quasi-granular granulated sintering material is put on a pallet (pallet) of a DL sintering machine, and helps to ensure good ventilation of the sintering material-put layer, and to allow the sintering reaction to proceed smoothly. In the sintering reaction, the water content of the heated granulated raw material particles evaporates, and the downwind granulated raw material particles become high water content, thereby forming a region (wet zone) where the strength is lowered. In this wet zone, the particles of the granulated raw material are liable to break to obstruct the flow in the raw material filling layer, and the air permeability is deteriorated.

On the other hand, in recent years, it has been known that the micronization of iron ore is advancing, and the strength of granulated particles produced using micronized iron ore is small. Particularly, when water is added to the fine iron ore, the strength is greatly lowered, which causes a decrease in air permeability. In addition, in some cases, fine iron ore powder is difficult to granulate during the production of a raw material for sintering granulation. In the environment surrounding the fine iron ore for sintering, recently, a technique for producing high-quality sintered ore using hard-to-granulate iron ore containing a large amount of fine powder has been proposed.

For example, as one of such conventional techniques, there is an HPS method (Hybrid Pelletized Sinter method) described in patent document 1 (mixed pellet sintering method). This technique is intended to produce a sintered lump ore having a low slag ratio and a high reducibility by granulating a fine iron ore having a high iron content by using a barrel mixer and a granulator. However, this technique has a problem in that a large number of granulators must be provided when granulating a large amount of fine iron ore, and the manufacturing cost increases.

Next, a method has been proposed in which a raw material containing fine iron ore is subjected to a preliminary treatment or granulation using a high-speed rotary mixer before the granulation step of sintering the blended raw material powder. Specifically, there have been proposed a method in which a fine iron ore powder and a fine iron powder-making dust are mixed in advance by a mixer and then granulated by the mixer, and a method in which a sintered material mainly composed of fine iron powder is stirred by a mixer and then granulated by a granulator (patent documents 2 to 3). However, these methods have a problem that the granulated particles are mainly composed of a fine powder raw material, and the strength of the granulated particles is lowered as compared with the case of using core particles (iron ore) having a higher strength than the granulated particles.

Next, a method has been proposed in which a sintering material obtained by mixing a fine powder and a sintering material is previously mixed by an Eirich mixer and then granulated by a barrel mixer (patent documents 4 to 6). However, in these methods, there is a concern that the powder adhering layer becomes excessive when the proportion of the fine powder increases, and the combustibility of the granulated particles deteriorates. Further, there is a problem that the core particles are insufficient, so that the pelletizability is deteriorated, and the firing is performed in a state where the pelletization is incomplete.

Next, a technique for treating hardly pelletizable ore containing fine powder and a large amount of crystal water has been proposed (patent documents 7 to 9). However, in these prior arts, there is a problem that it is difficult to prevent the pressure loss in the wetting belt from rising due to evaporation of a large amount of moisture from the highly crystallized ore during sintering. In these methods, there is also a problem that, when a fine iron ore having a large amount of granulated particles and easily decreasing the strength is used, the pressure loss in the wet zone is easily increased further.

Regarding a method of using high-speed stirring when using fine powder, a method of granulating ore properties such as stirring conditions, device size, and core ore (patent documents 10 and 11) has been proposed. However, the protocols disclosed in these documents have not actually achieved studies of stirring conditions matching the properties of ores.

Prior art literature

Patent literature

Patent document 1 Japanese patent laid-open No. 62-37325

Patent document 2 Japanese patent laid-open No. 1-312036

Patent document 3 Japanese patent laid-open No. 2007-247020

Patent document 4 Japanese patent laid-open No. 11-061282

Patent document 5 Japanese patent laid-open No. 7-331342

Patent document 6 Japanese patent laid-open No. 7-48634

Patent document 7 Japanese patent laid-open publication No. 2005-194616

Patent document 8 Japanese patent laid-open No. 2006-63350

Patent document 9 Japanese patent laid-open publication No. 2003-129139

Patent document 10 International publication No. 2017/094255

Patent document 11 International publication No. 2017/150428

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to establish a technique capable of overcoming the problems of the prior art described above, and in particular, to provide a method for improving the manufacturability of sintered ore by using a granulating raw material obtained by this method by establishing a production technique for a more advanced granulating raw material for sintering by researching the suitability of stirring conditions (stirring energy) obtained by taking into consideration the properties of iron ore varying every day (micronization, etc.).

Means for solving the problems

During the intensive studies on the problems of the prior art, the inventors have repeatedly studied focusing on the properties of iron ore, in particular, the adhesion of fine powder portions. As a result, in the case of iron ore having poor adhesion of the fine powder, the stirring treatment is performed in a large amount or not, whereby the effect of high-speed stirring can be exhibited to the maximum extent. On the other hand, it was found that in the case of iron ore having low adhesion, it is effective to impart low stirring energy to exert the effect of high-speed stirring. Here, the stirring energy cannot be estimated from the circumferential speed of the blade or the length of the blade, but is a variable factor depending on mechanical conditions such as moisture related to the adhesiveness of the raw material, and the position of the raw material at which height the blade or the mineral type collides with, and it is difficult to easily estimate the stirring energy.

It is known that the conventional problems can be controlled by focusing on the particle Size Distribution Index (SDI), which is an index obtained by taking into consideration the particle size distribution of iron ore itself. Therefore, the energy to be applied when the sintering blend material is stirred is determined based on the index (SDI), and the productivity of the sintering granulation material and the sintered ore is maximized.

That is, the present invention provides a method for producing a granulated material for sintering, characterized in that, when producing a granulated material for sintering by granulating a sinter batch material after stirring at a high speed, stirring power at the time of stirring at a high speed is adjusted in accordance with a particle size distribution of an iron-containing material in the sinter batch material.

The present invention also provides a method for producing a sintered ore, characterized by charging a sintering granulation raw material produced by the above-mentioned method for producing a sintering granulation raw material into a sintering machine and sintering the material.

In the present invention, it is considered that the following embodiments are more preferable if the following means are adopted:

(1) During high-speed stirring of the sintering mixture, the stirring power is adjusted based on the particle Size Distribution Index (SDI) of the following formula (1),

Wherein,

W _io500 (mass%) is the proportion of the iron-containing raw material not exceeding 500 mu m,

W _fL (mass%) is the proportion of particles having a particle diameter of 15 to 500 μm in the iron-containing raw material,

W _fS (mass%) is the proportion of particles having a particle diameter of less than 15 μm in the iron-containing raw material,

D _L (mm) is the average particle diameter of the particles with the particle diameter of 15 to 500 mu m in the iron-containing raw material,

D _S (mm) is the average particle size of the particles having a particle size of less than 15 μm in the iron-containing raw material.

(2) Using a sintering blend material having a particle Size Distribution Index (SDI) represented by the formula (1) satisfying the relationship of SDI >7 during high-speed stirring of the sintering blend material,

(3) During the high-speed stirring of the sintering mixed raw material, the high-speed stirring is performed with stirring power satisfying the following (2),

0.172×{1+(1.12SDI-8.95)}×Q>0...(2)

Where Q (kWh/t) is a value obtained by dividing the difference between the power consumption (kWh) of the rotor of the stirring blade between the load time and the no-load time by the weight (t) of the sintered compact raw material subjected to high-speed stirring. (under load: with sinter batch. Under no load: without sinter batch).

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, since high-speed stirring, which is a treatment before granulation, can be suitably performed, a more complete mixing state can be gradually brought about, and the so-called granulation property after high-speed stirring can be improved. And, this can lead to a yield increase of the sintered ore.

Drawings

Fig. 1 is a graph showing a relationship between stirring energy and granulation particle diameter.

Fig. 2 is a graph showing a relationship between a granulation particle diameter and sintering productivity.

Fig. 3 is a graph showing the relationship between the particle size distribution index and the influence coefficient.

Fig. 4 is a graph showing a relationship between stirring energy and an increase in particle diameter of the granulated material.

Detailed Description

First, the present inventors studied the physical properties of the powder-adhering layer in order to improve the effect of high-speed stirring, which is a treatment before granulation. As a result, in the case where the adhesion of the adhering powders is poor, the adhering powders that have adhered to each other are peeled off instead due to high-speed stirring, and the subsequent granulation process requires more time. On the other hand, it was found that in the case of a powder with high adhesion, if the powder is in a completely mixed state, the adhesion is high, and the granulation is promoted, but in the case of no mixing, the particle size distribution is not optimized, and the particle size is hard to grow during granulation, and the present invention has been developed.

Hereinafter, examples will be described in order to confirm the effects of the present invention. In the study using this example, first, a sintering blend material containing an iron-containing material was stirred at a high speed, then granulated by a barrel mixer to obtain a granulated material for sintering, and then sintered by a DL sintering machine using the granulated material, and the effect of improving the productivity of the sintered ore as a result thereof was studied.

The raw material formulation at this time is shown in table 1. In this test, the blending ratio of three kinds of the sintering material, ore C as concentrate (concentrate) and ore D as pellet was changed and used as the iron-containing material. Tests were performed to prepare the fine powder concentrate by basic addition and the ore C, D added as the fine powder concentrate, and to prepare the fine powder concentrate to 15 mass%. Since the ore D is a pellet, it is very fine compared to the ore C, and the influence on the fine particles can be evaluated. Here, as the iron-containing raw material of the fine powder, a pellet (ore D) is used, but similar to the pellet (ore D), dust generated in the iron-making process including particles having a particle diameter of less than 15 μm may be used.

TABLE 1

Sample No.	Example 1	Example 2	EXAMPLE 3	EXAMPLE 4
					Sintering material	78.0	73.4	65.0	65.0
Concentrate: ore C	0.0	5.3	13.4	0.0
					Pellet material and ore D	0.0	0.0	0.0	13.4
Dolomite (Dolomite)	7.6	6.8	7.1	6.9
					Rolling scale	1.9	2.2	2.2	2.2
Limestone powder	11.5	11.1	10.6	10.9
					Quicklime	1.0	1.1	1.1	1.1
Totalizing	100.0	100.0	100.0	100.0
					Coke scraps	4.5	4.4	44	4.4

In this test, in order to evaluate the performance of the high-speed mixer, the change in the granulation particle diameter with respect to the residence time (stirring time) in the high-speed mixer was examined. Since this mixer is used in continuous operation, the retention time T (sec) is determined by the ratio of the amount of the charged raw material M _f (T/sec) and the amount of the accumulated raw material M _in (T), as shown in the following expression (3).

In order to evaluate the stirring energy applied to the raw material to be stirred, the power consumption of the rotor attached to the stirring blade of the high-speed stirrer was measured. The electric power applied to the raw material is obtained by subtracting the value obtained when the raw material is not being fed (at the time of idling) from the electric power fed under each condition, and the amount of consumed electric power is calculated from the electric power and the residence time of the above formula (3). The value obtained by dividing the power consumption by the amount of the product is the power consumption per unit raw material, and is defined as the stirring energy per unit raw material.

Fig. 1 shows the relationship of the particle size of the ore C, D to the stirring energy per unit of raw material in a real machine stirrer. As shown in the figure, in the case where there is no fine powder concentrate, the stirring energy increases, and the granulation particle size increases. In addition, when the ore C as the concentrate (concentrate) is 5.3 mass%, the granulation particle size slightly increases by the high-speed stirring method, but when the amount is greatly increased to 13.4 mass%, the granulation particle size conversely decreases. On the other hand, when the amount of the ore D as the pellet is increased to 13.4 mass%, the granulation particle size is greatly increased by the high-speed stirring method.

Fig. 2 shows the relation between the grain size and the sintering productivity when the fine powder concentrate was mixed in the test using the solid machine. As shown in the figure, even if the fine powder of any one of the ores C, D is added, the particle size of the granulated ore is smaller in both the conventional method and the high-speed stirring method than in the case of granulating the ore C which is a basic condition (conventional method) by blending 5.3 mass%. On the other hand, focusing on the effect of the preliminary treatment by high-speed stirring, when 5.3 mass% of ore C is blended, the sintering productivity increases from 1.01t/h/m ² to 1.04t/h/m ² by 0.03t/h/m ² by high-speed stirring, and when 13.4 mass% of ore C is blended, the effect of the high-speed stirring is small as compared with the conventional method. On the other hand, in the case where ore D as a pellet was added, the productivity increased from 0.92t/h/m ² to 0.99t/h/m ² by 0.07t/h/m ² by the high-speed stirring method as compared with the case where stirring was not performed.

From the above results, it was found that, although it is inevitable that the sintering productivity is lowered with the reduction of the granulation particle size in the case of using fine-grained fine powder concentrate in the solid sintering process, the reduction of the granulation particle size can be suppressed and the sintering productivity can be improved by introducing the high-speed stirring method according to the present invention according to the above results.

Next, in order to quantitatively develop the characteristic high-speed stirring effect in the method for producing a granulated raw material for sintering of the present invention, the influence of stirring energy on the increase in the granulation particle diameter was studied. As a result, the increase in the granulation particle size under the same type and addition ratio of the fine powder concentrate can be said to be a value obtained by subtracting the granulation particle size of the conventional method from the granulation particle size of the high-speed stirring method. Therefore, the increase in the granulation particle size by the high-speed stirring method when the fine powder concentrate was 0 mass% of the raw material was evaluated first. That is, the increase in the particle size of the granulated particles by the high-speed stirring method under the condition that the fine powder concentrate is 0 mass% was defined as Δd (Q) (mm), and the stirring energy was defined as a function of Q (kWh/t). Then, when the relationship between Q and Δd (Q) is determined as a function according to fig. 1, the following expression (4) can be obtained.

ΔD(Q)=0.172Q...(4)

In order to evaluate the influence of the type of fine powder concentrate on the increase Δd _p (mm) of the granulation particle diameter under the conditions that the type of fine powder concentrate and the addition amount are arbitrary as shown in fig. 2, the influence coefficient α is defined according to the expression (4) for each type of fine powder concentrate, and the following expression (5) is obtained.

α=(ΔDp-ΔD(Q))/ΔD(Q)...(5)

It is considered that the ultrafine powder having a particle size of 15 μm or less improves the adhesion between ores, and the particle size of 15 μm or more reduces the adhesion. (S.Kawachi, S.Kasama: tetsu-to-Hagane,94 (2008), 475.) therefore, the particle size distribution index (Size Distribution Index: SDI) is redefined using a proportion W _io500 (mass%) of iron ore which can be regarded as a cohesive powder of not more than 500 μm, a particle proportion W WfL (mass%) of particles having a particle size of 15 to 500 μm in the iron-containing raw material, a particle proportion W _fS (mass%) of not more than 15 μm, an average particle size d _L (μm) of particles having a particle size of 15 to 500 μm, and an average particle size d _S (μm) of not more than 15 μm.

Here, the average diameter of 15 to 500 μm is 87 μm as a geometric average of 15 μm and 500 μm, and as for the particle diameter of not more than 15 μm, 4 μm as a geometric average of 1 μm and 15 μm is used. In the following expression (6), the reason why the weight ratio of each particle is divided by the average particle diameter d _L、d_S is to reflect the influence of the specific surface area of the particles which is considered to have an influence on adhesion.

In the present invention, the particle size is a particle size obtained by sieving with a sieve having a nominal mesh according to JIS (Japanese Industrial Standard) Z8801-1. For example, the particle diameter of 1mm or less means the particle diameter of a sieve having a nominal mesh size of 1mm in accordance with JIS Z8801-1, and is also referred to as-1 mm hereinafter. Further, the minimum value of the nominal mesh defined in JIS (Japanese Industrial Standard) Z8801-1 is 20. Mu.m, and when the nominal mesh is smaller than the minimum value of the nominal mesh, for example, 15. Mu.m or smaller, the minimum value is a particle diameter of substantially 100% as a cumulative fraction of 15. Mu.m or smaller as determined by a laser diffraction/scattering method according to JIS Z8825 and a liquid-phase gravity precipitation method according to JIS Z8820-2.

Next, using the data shown in fig. 2, the following expression (7) can be obtained from the analysis result obtained from the relationship between the influence coefficient α of expression (5) and the particle size distribution index SDI of expression (6). The relationship is shown in fig. 3.

α=1.12.SDI-8.95...(7)

As shown in fig. 3, there is a clear positive correlation between the particle size distribution index SDI and the influence coefficient α. This shows that the larger the particle size distribution index SDI, the larger the rise value Δd _p of the granulation particle size by the high-speed stirring method becomes. From these results, it was found that it is effective to increase the particle ratio of the fine powder concentrate of not more than 15 μm and decrease the particle ratio of 15 to 500 μm in order to achieve an increase in the granulation particle size by high-speed stirring. It is considered that, as an effect of adding particles of not more than 15 μm, they are uniformly dispersed among the raw material particles at the time of high-speed stirring, and as a result, an effect of improving adhesion is exhibited.

On the other hand, it is estimated that the particles 15 to 500 μm have low adhesion, and cannot be fixed to each other, but rather have an effect of preventing the adhesion of the particles to each other during granulation.

Then, when Δd _p (an increase in the granulation particle diameter) is decomposed from the above-described formula (5) and formula (7), the following formula (8) can be obtained.

AD_P=(1+α)·ΔD(Q)

=(1+(1.12SDI-8.95))·ΔD(Q)...(8)

Next, fig. 4 shows the results obtained by calculating the influence of the increase value Δd _p of the particle size by using the particle size distribution index SDI and the stirring energy Q as parameters. As is clear from fig. 4, if the SDI is the same, the larger the stirring energy (kWh/t) applied to the raw material is, the larger the rise Δd _p of the granulation particle diameter becomes, and if the stirring energy is the same, the larger the SDI becomes, the larger the rise Δd _p of the granulation particle diameter becomes. Therefore, when the proportion of particles of 15 to 500 μm, which have decreased adhesion, is increased and the SDI is decreased as in the case of the concentrate (concentrate) blending, a larger stirring energy is required to obtain the same particle diameter increasing effect. In contrast, when the proportion of particles not exceeding 15 μm increases and the SDI increases as in the case of blending pellets, the effect of improving the pelletizability by the high-speed stirring method can be obtained by applying relatively small stirring energy.

From the above results, it is found that when a large amount of fine ore is used in the production of a granulated material for sintering, it is important to mix a large amount of pellet materials and stir them at high speed in order to maintain the granulation property. This effect is considered to be because the pellet material having the powder layer adhered thereto is mixed and reinforced, so that the filling property is improved and the adhesion of the granulated particles is improved.

Industrial applicability

The present invention can be applied not only to a raw material for granulating for sintering but also to a technique for granulating and agglomerating other raw materials for producing iron.

Claims

1. A method for producing a granulated raw material for sintering, characterized in that:

When a granulated raw material for sintering is produced by granulating a sintering raw material at a high speed after stirring the sintering raw material, the power during the high speed stirring is adjusted according to the particle size distribution of the iron-containing raw material in the sintering raw material.

2. The method for producing a granulated raw material for sintering according to claim 1, characterized in that:

During high-speed stirring of the sintering raw materials, the stirring power is adjusted based on the particle size distribution index (SDI) of the following formula (1):

in,

W _io500 (mass %) is the proportion of the iron-containing raw material that does not exceed 500 μm,

W _fL (mass %) is the ratio of particles with a particle size of 15 to 500 μm in the iron-containing raw material.

_WfS (mass %) is the ratio of particles with a particle size of less than 15 μm in the iron-containing raw material.

d _L (mm) is the average particle size of particles with a particle size of 15 to 500 μm in the iron-containing raw material,

d _S (mm) is the average particle size of particles having a particle size of less than 15 μm in the iron-containing raw material.

3. The method for producing a granulated raw material for sintering according to claim 2, characterized in that:

During the high-speed stirring of the sintering raw material, a sintering raw material having a particle size distribution index (SDI) expressed by the formula (1) satisfying the relationship of SDI>7 is used.

4. The method for producing a granulated raw material for sintering according to any one of claims 1 to 3, characterized in that:

When the sintering raw materials are stirred at high speed, stirring is performed at high speed with a stirring power satisfying the following formula (2):

0.172×{1+(1.12SDI-8.95)}×Q>0…(2)

Among them, Q (kWh/t) is the value obtained by dividing the difference in power consumption (kWh) of the rotor of the stirring blade between load and no-load by the weight (t) of the sintering raw materials subjected to high-speed stirring (load: with sintering raw materials; no-load: idling without sintering raw materials).

5. A method for producing sintered ore, characterized in that:

The granulated raw material for sintering produced by the method for producing a granulated raw material for sintering according to claim 4 is charged into a sintering machine and sintered.