JP2012067348A - Pretreatment method for sintering raw materials - Google Patents

Abstract

The present invention provides a pretreatment method for a raw material for sintering, which can sinter a hardly granulated fine powder raw material without lowering productivity and yield when agglomerated using a sintering machine.
When a raw material containing 30% by mass or more of limestone and having a particle size constitution ratio of 50% by mass or more having a diameter of 0.25 mm or less is agglomerated with a sintering machine, (i) , Granulated into a granulated product of 8 mm or less with a high-speed agitation granulator or vibration type granulation, and then (ii) passed through a rotating drum or the like to crush the granulated product with a crushing strength of less than 30 N, Finally, (iii) it is characterized by classifying and removing ungranulated material of 1 mm or less.
[Selection] Figure 1

Description

  The present invention relates to a pretreatment method for a fine powder material when the fine powder material is agglomerated using a sintering machine.

  When the raw material is agglomerated using a sintering machine, in order to smoothly burn the mixed solid fuel and allow the sintering reaction to proceed stably, ensure the air permeability of the raw material packed bed appropriately. There is a need. For this reason, before supplying a raw material to a sintering machine, a raw material is granulated. That is, by stirring the raw material with an appropriate amount of water in the granulator, the fine raw material is adhered with water around the coarse particles in the raw material, and the raw material is granulated (hereinafter referred to as this granule). The granulated product is called pseudo particle).

  In general, since the productivity of the sintering machine increases in proportion to the ventilation speed, the productivity of the sintering is determined by whether or not sufficient granulation treatment can be performed to ensure the air permeability of the raw material packed layer appropriately.

  Currently, in the iron ore sintering method adopted by the steel industry, a drum type rolling granulator is used for this granulation treatment. This is because the drum type rolling granulator is suitable for mass production, and here, the amount of fine particles (0.25 mm or less) to be adhered is about 20 to 30% by mass, and only the rolling operation is performed. This is because pseudo particles having an appropriate particle size configuration and strength can be obtained.

  Further, when a raw material with a high content of fine particles is targeted, the layer of adhering powder particles surrounding the core particles becomes thick, so that the solid fuel is buried therein and combustion is hindered. In order to avoid this, a solid fuel is packaged.

  That is, first, a raw material not containing solid fuel is granulated, and then the granulated product and solid fuel are mixed to prevent the solid fuel from being buried. A method called a HPS method (see Non-Patent Document 1), which uses a dish mold for a rolling granulator and combines this with a solid fuel exterior method, is typical of this method.

  In the case of raw materials mainly composed of iron ore for pellets (pellet feed) and dust, the rolling granulation method cannot be applied to the pretreatment of the sintering method. In such a raw material, the content of fine particles further increases, and in rolling granulation, the particle size of the granulated product becomes excessive, and in the short time heat treatment in the sintering method, the center of the granulated product is sufficiently obtained. The temperature does not rise and sintering does not proceed sufficiently.

  The pellet method uses this coarsening, and the particle diameter usually exceeds 10 mm. On the other hand, the heating device uses a device that can sufficiently secure the heating time such as a kiln. .

  On the other hand, a high-speed agitation type (see Patent Document 1) having a function of crushing coarse particles by applying a strong impact force to the raw material, or a vibration type granulator as a rolling granulator It is conceivable to use it instead to prevent enlargement of the pseudo particle size.

  However, these granulators can control the impact force and control the particle size of the granulated product to be smaller than that of the rolling granulator. There is a disadvantage that the amount increases. As a means for solving this drawback, in the prior method (see Patent Document 2), a new sieve is provided after the high-speed agitation type or vibration type granulator, granulation while preventing coarsening, and The raw material with insufficient granulation is removed to obtain a preferable particle size distribution for the sintering method.

  However, even in the prior method, it has been found that raw materials that are difficult to granulate have the following problems. That is, even if an appropriate particle size configuration is obtained immediately after processing, the strength of the granulated product varies greatly, and the pseudo particles having low strength collapse in the transport process after the pre-processing, and are used in the sintering machine. In the immediately preceding raw material, the amount of fine powder increases again.

  The raw material that is difficult to granulate is specifically a raw material in which the amount of limestone is increased with respect to the iron-containing raw material such as dust and pellet feed. Limestone is thought to be difficult to adhere because it has many rhombohedral cleavages and flat surfaces, and it is difficult to form strong pseudo particles.

Japanese Patent No. 2953308 International Publication WO2007 / 063603 Pamphlet

Sakai and Steel, 73 (1987), 1504.

  Based on the present state of the prior art, the present invention has an appropriate particle size configuration in order to smoothly agglomerate a hardly granulated raw material with a large amount of limestone using a sintering machine. It is an object of the present invention to provide a pretreatment method for producing a granulated pseudo particle having strength that does not collapse even during transportation.

  The present invention is characterized in that an operation for breaking a granulated material having a low strength is newly added to the prior art granulating method, thereby solving the above-mentioned problems.

  The gist of the present invention is as follows.

  When a raw material containing 30% by mass or more of limestone and having a particle size composition ratio of 50% by mass or less having a diameter of 0.25 mm or less is agglomerated with a sintering machine, (i) the raw material is a high-speed stirring type Granulate into a granulated product of 8 mm or less with a granulator or vibration granulation, then (ii) pass through a rotating drum or the like to crush the granulated product with a crushing strength of less than 30 N, and finally ( iii) A pretreatment method for a raw material for sintering, characterized by classifying and removing ungranulated material of 1 mm or less.

  According to the present invention, agglomeration can be smoothly performed using a sintering machine even for a hardly granulated fine powder material having a large amount of limestone. Specifically, calcium ferrite sintering is used in which limestone is used in a large amount in comparison with the range of production of ordinary blast furnace sinter (see Japanese Patent Application Laid-Open No. 2007-169707, Japanese Patent Application Laid-Open No. 51-133200). ), The sintering operation can be performed without reducing productivity, yield, strength, and the like.

It is a figure which shows the manufacturing process explaining the outline of embodiment of this invention. It is a figure which compares and shows the intensity distribution of the pseudo particle before and behind the process by a rotating drum.

  First, the configuration of the present invention will be described in detail with reference to FIG.

  First, the raw materials are mixed and granulated with water in a high-speed agitation granulator or a vibration granulator. At this time, the maximum diameter of the pseudo particles after granulation can be controlled by adjusting the rotation speed of the rotary blade in the high-speed agitation granulator, and the frequency can be adjusted in the vibration granulator. Can be controlled. In any of the granulators, the larger the impact force to the raw material, the larger the granulated material collapses, so that the maximum diameter of the pseudo particles can be reduced.

  Next, the granulated raw material is passed through a rotating drum having a lifter. Of course, no water is sprayed in the rotating drum. The raw material is lifted upward by a lifter and passes through the rotating drum while repeatedly receiving a downward movement. Due to the drop impact at this time, the low-strength pseudo-particles collapse, and only the high-strength particles remain.

  Since the upper limit of the strength to be collapsed is determined by the drop height and the number of drops, it can be adjusted by the drum diameter and the drum length. At this time, it is preferable that all or part of the solid fuel is introduced into the rotating drum and mixed with the raw material. This is a so-called solid fuel exterior. The purpose of this step is to destroy low-intensity pseudo particles, and any apparatus other than the rotating drum having the same function can be applied to the present invention.

  Finally, the raw material subjected to the above treatment is sieved to remove fine powder. If excessively fine powder remains in the raw material, the air permeability of the raw material packed layer will be hindered during sintering, which will lead to a decrease in productivity of the sintering machine and non-uniformity in the progress of sintering. Therefore, only the granulated raw material on the sieve is charged into a sintering machine and sintered. The fine powder (under the sieve) is returned to the granulator and reused as a raw material.

  Subsequently, numerical conditions defined in the present invention will be described.

  The present invention first assumes that calcium ferrite as a dephosphorizing agent for steel making is produced by a sintering machine. This raw material is composed of fine iron raw materials such as steelmaking dust and pellet feed and powdered limestone for sintering (usually 3 mm or less), and the ratio of limestone to all raw materials is 30 to 60% by mass.

  Furthermore, this raw material has a particle size smaller than that of an ordinary blended raw material for blast furnace ore, and a composition ratio of 0.25 mm or less is 20 to 30 mass for an ordinary blended raw material for blast furnace ore. %, But 50% by mass or more.

  The upper limit particle size of the granulated product when granulated with a high-speed stirring granulator or a vibration granulator was defined as 8 mm. This is because, when the particle size of the granulated product exceeds 8 mm, the heat treatment for a short time in sintering does not sufficiently raise the temperature to the center of the granulated product, and the sintering does not proceed sufficiently.

  With the rotating drum, the minimum crushing strength of the pseudo particles to be left was set to 30N. Pseudo particles having an intensity of less than 30 N have a risk of collapsing due to dropping or the like when transferring by a belt conveyor during transportation.

  When removing the ungranulated material with a sieve, the sieve mesh was 1 mm. In the wet raw material which is the subject of the present invention, clogging with a mesh size of less than 1 mm causes clogging and smooth operation is not possible. By adjusting the sieve efficiency of the sieve, the fine powder residual ratio of the raw material after the treatment is adjusted. From the viewpoint of sintering, 1 to 10% by mass is preferable at a 0.25 mm% ratio.

  In the present invention, limestone is assumed as the hardly granulated raw material. However, the present invention is not limited to raw materials containing a large amount of limestone, but can also be applied to the case of using a large amount of Australian maramba-based iron ore, iron sand, and the like. In Mara Mamba, a martin small crystal having a smooth surface, and in iron sand, a self-shaped magnetite crystal has reduced granulation properties, and both are raw materials classified as hardly granulated raw materials.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
The invention example in which the raw material for calcium ferrite production was sintered using the raw material granulated according to the manufacturing process shown in FIG. 1 and the manufacturing process shown in FIG. Comparative examples in which sintering was performed using the raw materials thus prepared were compared.

  The raw materials consisted of steelmaking dust: 43% by mass, limestone: 50% by mass, quick lime: 2% by mass, and powdered coke: 5% by mass, and the ratio of 0.25 mm or less before granulation treatment was 65%. As the vibration type granulator, VMPC200 type (maximum processing capacity: 7 tons per hour) manufactured by Abe Iron Works was used, and the target moisture was 10% by mass.

As the rotating drum, a cylinder having a diameter of 1 m and a length of 3 m and four lifters having a height of 10 cm attached thereto was used. A sieve having a sieve area of 1.5 m ² and a sieve mesh of 1 mm was used.

  FIG. 2 shows a comparison of the intensity distributions of the pseudo particles after treatment when the rotating drum process is performed (invention example) and without the rotating drum process (comparative example). It can be seen that the pseudo-particles of less than 30N have disappeared by the treatment with the rotating drum.

  In the raw material after the final sieving treatment, the ratio of 0.25 mm or less was 1 to 10% by mass. Moreover, the processing speed of the raw material by these series of facilities was 1 t / min.

The pretreated raw material was once stored in a hopper and agglomerated by a circular sintering machine having a sintered area of 0.5 m ² . The production rate and product yield at that time were measured.

  Table 1 shows productivity and product yield at the time of sintering in the inventive examples and the comparative examples. In the inventive examples, it can be seen that the sintering productivity and the product yield are remarkably improved.

  As described above, according to the present invention, agglomeration can be smoothly performed using a sintering machine even for a hardly granulated fine powder material having a large amount of limestone. Specifically, limestone, compared to the range of ordinary blast furnace sinter ore production, even in the case of calcium ferrite sintering used in large quantities, without reducing productivity, yield, strength, Sintering operation becomes possible. Therefore, the present invention has high applicability in the raw material processing technology of the steel industry.

Claims (1)

  When a raw material containing 30% by mass or more of limestone and having a particle size composition ratio of 50% by mass or less having a diameter of 0.25 mm or less is agglomerated with a sintering machine, (i) the raw material is a high-speed stirring type Granulate into a granulated product of 8 mm or less with a granulator or vibration granulation, then (ii) pass through a rotating drum or the like to crush the granulated product with a crushing strength of less than 30 N, and finally ( iii) A pretreatment method for a raw material for sintering, characterized by classifying and removing ungranulated material of 1 mm or less.

Images