KR100431840B1 - A method for producing a cold bonded pellet - Google Patents

Abstract

The present invention relates to a method for producing non-fired pellets composed mainly of fine iron ore or iron-containing dusts, and to which a hydraulic binder is added, wherein the assembling step of non-fired pellets is divided into two steps and the type of binder used in each step is changed. It is an object of the present invention to provide a method for producing non-plastic pellets having good strength and low adhesion.

The present invention provides a method for producing non-fired pellets, which is composed of finely divided iron ore or iron-containing dust and mainly cured after blending a blended raw material containing a hydraulic binder.

A primary granulation step of primary granulation of a primary blended raw material in which one or more conventional binders are added to a particle size of 70 to 96% of the final particle size of the pellet;

A secondary assembly step of attaching the secondary compounded material to which the crude steel cement is added to the fresh pellet surface layer first assembled in the primary assembly step to secondary assembly to the final particle diameter of the pellet; And

In the second assembling step, the main method is a method for producing non-fired pellets comprising the step of curing the raw pellets assembled secondarily.

Description

A method of manufacturing non-fired pellets {A METHOD FOR PRODUCING A COLD BONDED PELLET}

The present invention relates to a method for producing non-fired pellets mainly composed of fine iron ore or iron-containing dusts, and to which a hydraulic binder is added, and more particularly, to a non-fired pellet having excellent strength and low adhesion with two steps of assembling. A method for producing pellets.

As the binder of the non-fired pellets, cements such as ordinary portland cement, effervescent steel cement, cement clinker, and blast furnace cement are used.

On the other hand, blast furnace quenching slag powder is mainly used as a material to replace expensive cements, and fine powder slag, gypsum, and quicklime generated during stainless steel manufacturing to prevent delay of curing time when blast furnace quenching slag powder is used. In addition, dust generated in the quicklime process may be added as a curing accelerator.

The amount of binder added in the preparation of non-fired pellets depends on the use of the non-fired pellets. In the case of blast furnaces, the amount of the binder added to the curing treatment to have a compressive strength of about 150 kgf or more is about 8 to 10%. In the case of steelmaking, the compressive strength is maintained at about 40-50 kgf or more, and the amount of binder required is about 3-6%.

In the case of non-plastic agglomerates using a hydraulic binder, it takes a certain time for the hydraulic material to hydrate and cure with water. As such, the curing time, i.e. curing time, required for the non-baked mass to reach a predetermined strength at room temperature varies depending on the raw material conditions, the operating conditions, and the curing conditions, but generally takes about 3 to 14 days. do. As a method of shortening the curing time of the non-plasticized bulk material, the curing temperature is set to about 60 to 70 ° C. or less higher than room temperature under constant raw material and binder conditions. It has been proposed to use finer cements and to further refine the particle size of the quenched slag powder. For example, in the conventional non-fired pellet manufacturing, in order to shorten the total curing time or to prevent the delay of the curing time in winter, about 20% of the total cements were used by replacing the super-tough steel cement. This super rough steel cement has a specific surface area of about 3800-4500 cm 2 / g, which is higher than that of ordinary ordinary cement, Portland cement (about 2600-3000 cm 2 / g). There was an advantage.

In addition, a method for producing non-fired pellets is also known, wherein the non-fired bulk granules are assembled in two stages in a state where the total amount of the binder is kept constant or slightly reduced.

The non-fired pellets (lumped products) are deposited in indoor or outdoor yards in a wet state immediately after their manufacture until they reach a predetermined compressive strength, depending on the application, and are therefore essentially cured by a hydration reaction between the binder and water. The non-baked bulk cargo, which has reached a certain strength in the yard, is then transported by belt conveyors or trucks to each load storage tank for use in processes such as blast furnaces or converters, and then waits for actual loading into the furnace. Done. In the abnormal atmosphere, such as a large amount of differentiated mass in the furnace and a large amount of excess water in the bulk, such as the bulk of the bulk or a part of the bulk of the bulk The situation occurs when it is attached to the wall and then fixed. In this way, if there are deposits on the wall of the reservoir, the discharge of the bulked product to the lower part of the reservoir is not smooth, which makes it difficult to quantitatively use the bulked product and causes disturbance in the steelmaking or steelmaking reaction. In this case, the field workers during the operation will be to remove and remove the attachments on the wall of the reservoir by manual work.

As a method for preventing the attachment of non-fired masses or powders in a charge reservoir, the following have been proposed. That is, when charging a block in a storage tank, spectroscopy is added together as a filler in a storage tank. Since the spectral stones in which the hydration reaction does not occur are coated on the surface of the block or powder in the storage tank, the block or block can be prevented from adhering to and fixed to the inner wall of the storage tank. At this time, the lumped substance and the spectroscopy discharged are separated through a sieve before being charged into the blast furnace or converter, and the spectroscopy dropped into the sieve is recycled back to the filler. Another method is to manage the moisture of the bulk material charged into the storage tank. In this method, if the moisture of the bulk material is about 5-7% or less, the hydration reaction rate is considerably slowed. Cargo or powder is hard to stick to the inner wall.

However, these methods are not practically preferable because they have to use a separate filling spectroscopy, and there is a problem of using a drier or treating the rain indoors when curing the bulk.

On the other hand, the method of using a certain amount of the cemented steel cement as the binder of the non-fired pellets has the effect of improving the adhesion in addition to the reduction of the curing time and the compressive strength of the original purpose.

However, in the case of the above method, not only the effect of improving the adhesiveness is high but also the use amount of the super-steel cement is not economically increased because it is expensive. Will be required.

In addition, the conventional non-fired pellet manufacturing method using the above-described assembling step in two stages improves the function of the pelletizer mainly for the purpose of improving the pellet compressive strength, or the ratio of the binder added to the primary granulator and the secondary granulator. It is not effective for improving the adhesion of pellets because it is controlled.

In other words, simply increasing the binder addition ratio of cement to the surface layer of the pellet has a problem that the effect of improving the adhesion in addition to the improvement of the compressive strength cannot be expected.

In the case of the above method, the amount of cement in the blended raw material is about 30-40% of the total raw material in the first granulation step, and the granulated particle is grown to about 80% of the final particle diameter, and the pellet discharged in the second granulation step is assembled. Again, assemble to the final particle size with the blended raw material added about 60-70% of the total cement amount.

However, the method described above has the problem that the strength of the pellets is improved at the same cement addition amount, but the adhesion improvement effect cannot be expected.

In order to solve the above problems of the prior arts, the present inventors have conducted research and experiments, and proposed the present invention based on the results. In the manufacturing method of non-plastic pellets to which the hydraulic binder is added, the non-plastic pellets are divided into two steps, and the binders used in each step are changed to prepare non-plastic pellets having excellent strength and low adhesion. The purpose is to provide a method.

The present invention provides a method for producing non-fired pellets, which is composed of finely divided iron ore or iron-containing dust and mainly cured after blending a blended raw material containing a hydraulic binder.

A primary granulation step of primary granulation of a primary blended raw material in which one or more conventional binders are added to a particle size of 70 to 96% of the final particle size of the pellet;

A secondary assembly step of attaching the secondary compounded material to which the crude steel cement is added to the fresh pellet surface layer first assembled in the primary assembly step to secondary assembly to the final particle diameter of the pellet; And

It relates to a method for producing non-plastic pellets comprising the step of hardening the second pellets assembled pellets in the secondary assembly step.

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

The present inventors have found that in the course of examining the strength-expressing behavior of conventional non-fired pellets, the curing completion period differs depending on the type of binder used in the production of the non-fired pellets.

That is, the present inventors made the assumption that if the curing reaction of the non-baked pellet surface portion was completed early, the pellets could be prevented from sticking to the inner wall. It's time to complete the method.

In the case of preparing non-fired pellets by dividing the granulation step into two steps according to the present invention, the type of binder used is different in each step.

As the binder used in the first granulation step, any binder that is commonly used may be used, and examples thereof include hydraulic materials such as cements, slags, and quicklime.

Examples of the cements include portland cement or ultra-light steel cement, cement clinker, blast furnace cement, and the like, and the slag may include blast furnace quenching slag.

In the first granulation step, one or two or more kinds of conventional binders are added to the blended material in a conventional range.

The amount of binder added in the preparation of non-fired pellets depends on the use of the non-fired pellets. In the case of blast furnaces in general, the amount of the binder is about 8 to 10 wt% based on the total blended raw materials. In the case of steelmaking, the amount of the binder is about 3 to 6 wt% with respect to the total blended raw material. The blended raw material also includes a binder.

In the present invention, the preferred amount of binder added in the primary granulation step is 15 wt% or less with respect to the primary blended raw material.

If too much binder is added in the first assembly step, the strength is improved, but the impurities are increased during the steelmaking process.

In the present invention, the roughened steel cement is used as the binder in the secondary assembly step.

The addition amount of the cemented steel is preferably selected to be 5wt% or more with respect to the secondary compounding material, since the adhesion rate increases when the addition amount is less than 5wt%.

On the other hand, in the present invention, the pellets are assembled to 70 to 96% of the final particle diameter in the primary granulation step.

If the particle size of the pellet in the first granulation step is less than 70% of the final particle size, the amount of binder used in the second assembly increases, and as a result, the total amount of the binder increases, resulting in low economical efficiency and When the particle size exceeds 96% of the final particle size, the amount of the binder-added blending material adhering to the surface of the pellets pelleted in the second granulation step is small, thereby achieving sufficient adhesion rate reduction. Since it becomes impossible, the particle size of the pellet assembled at the primary granulation step is set to 70 to 96% of the final particle size.

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

(Example)

In order to manufacture non-fired pellets, iron ore powder and sintering and dusts generated in the blast furnace were mixed as shown in Table 1 below, and the amount of the binder was kept constant at 10%. And the type and amount of binder added according to the kind are shown in Table 2 below.

Conventional Examples 1 to 4 show examples of the binder addition method of the prior art, and Inventive Examples 5 to 7 show examples of the binder addition method of the present invention.

In Table 2, Conventional Example 1 is a method of adding Portland cement alone while assembling step 1, and Conventional Example 2 is a method of adding Portland cement and cemented steel cement at a ratio of 8: 2. 3 is a method of adding a quicklime cement and a quick steel cement as a reaction accelerator by mixing portland cement and blast furnace quench slag 1: 1, and the conventional example 4 is a step 1 and 2 while the assembly step is composed of two steps as the present invention It is an addition method that varies the ratio of the iron-containing raw material and the binder added in the step granulation.

In contrast, the method of the present invention (inventive example 5 to inventive example 7) in which the granulation is performed in two steps is assembled to about 95% of the final particle size of the pellet in one step, and to an average of about 12 mm in two steps. The amount of added binder was 8-9% of the total blended raw material in the first stage granulation process, and 11.1-20.0% of the binder was blended in the second blending process.

Although the total amount of the binders in the Inventive Examples 5 to 7 is the same as the conventional addition amount level, the binder or less than the normal amount is added to the blending raw material in the first stage granulation process, and in the second stage, the cemented steel is more than the normal level. (A ratio of binder to secondary blend raw material).

For the non-fired pellets assembled as described above, the strength and adhesion rate after curing period 7, 14, 21, 28, and 35 days were measured, and the results are shown in Table 3 below.

The adhesion rate in Table 3 was measured as follows.

In the present invention, the non-plastic pellets are attached to the inner wall in the storage tank so that the pellets in contact with the inner wall are further hydrated in the presence of excess water, and the hydration reaction causes the pellets to adhere to the steel walls of the inner wall in contact with the pellets. The adhesion of non-plastic pellets to the inner wall of the reservoir was evaluated experimentally.

That is, in order to measure adhesiveness, 100 kg of non-baking pellets of diameter 10-15 mm were put into the iron box of 30 cm width, 30 cm length, and 60 cm height. The non-fired pellets put into the iron box were immersed in water for 10 minutes after a predetermined curing time had elapsed, and the adhered water on the surface of the pellets was removed. In this way, the non-fired pellets are immersed in water to reach about 11-12% of the water content in the pellets, and the pellets are placed in an iron box for 24 hours, after which the non-fired pellets of excess moisture are added in the storage tank. It was reproduced to cause a curing reaction. After 24 hours in the iron box, the non-fired pellet was poured out of the box and the amount of non-fired pellets attached to the box was weighed. The adhesion rate was calculated as follows.

Adhesion rate = (weight of non-fired pellets in the box × 100%) / (weight of non-fired pellets in the box)

division ironstone Sintered Dust Blast Furnace / Raw Material Dust Blast Furnace / Column Dust Blast furnace sludge Binder weight% 12 24 16 19 19 10

Example No. Primary assembly Secondary assembly Iron-containing raw materials Binder Iron-containing raw materials Binder Portland cement Barb steel cement Blast furnace / quench slag quicklime Portland cement Barb steel cement Conventional Example 1 90 10 － － － － － － Conventional Example 2 90 8 2 － － － － － Conventional Example 3 90 3.5 2 3.5 0.5 － － － Conventional Example 4 82 8 － － － 8 2 － Inventive Example 5 82 8 － － － 8 － 2 Inventive Example 6 82 4.0 － 3.5 0.5 8 － 2 Inventive Example 7 82 8 One － － 8 － One

Example No. 7 days 14 days 21st 28 days 35 days Strength (kgf) Adhesion Rate (%) Strength (kgf) Adhesion Rate (%) Strength (kgf) Adhesion Rate (%) Strength (kgf) Adhesion Rate (%) Strength (kgf) Adhesion Rate (%) Conventional Example 1 88 43 156 23 181 15 216 9 221 5 Conventional Example 2 102 41 176 19 195 12 223 5 230 4 Conventional Example 3 82 45 159 24 187 17 218 10 222 5 Conventional Example 4 91 39 160 21 185 14 218 9 221 5 Inventive Example 5 112 28 192 9 198 2 226 0 232 0 Inventive Example 6 101 31 189 10 199 4 228 0 233 0 Inventive Example 7 104 33 178 15 197 7 224 2 231 0

As shown in Table 3, the compressive strength of the non-fired pellets prepared by the prior art according to the addition method is somewhat different depending on the curing time, but after about 14 days of normal curing time, It can be seen that the target compressive strength is 150 kgf or more. However, it can be seen that the adhesion rate according to the curing period of these non-fired pellets does not coincide with the tendency of the compressive strength. That is, in the case of the conventional example 1 and the conventional example 3, the compressive strength after curing 14 days of non-fired pellets was 156 kgf and 159 kgf, respectively, and the blast furnace slag was added more than the ordinary cement added. Although the adhesion rate at this time is 23% and 24%, respectively, it can be seen that the pellet exhibited a higher adhesion rate when the blast furnace slag was added.

In addition, compared to the conventional example 2, the invention example 5 had an effect of improving from 102 kgf, 176 kgf to 112 kgf, 192 kgf in strength after 7 days and 14 days, respectively. Furthermore, in the non-baked pellets after 14 days of curing, the adhesion rate of the pellets of the prior art examples 1 to 4 was 19 to 24% level, but the adhesion rate of the invention examples 5 to 7 pellets was significantly low, 9 to 15% level, This tendency is more prominent as the curing time is extended.

On the other hand, as shown in Table 3, the adhesion rate of the non-plastic pellets tends to decrease as the curing period increases, which is interpreted to be related to the curing reaction, that is, the progress of the hydration reaction of the hydraulic binder present in the pellets. do. That is, as curing of the pellet particles progresses, the adhesion rate between the pellets or between the pellets and the inner wall of the storage tank is lowered. This may be because the additional hydration reaction does not proceed even if present.

As described above, the present invention can be more economically produced non-plastic pellets having excellent strength and low adhesion by dividing the non-plastic pellets into two stages and varying the type of binder used in each stage. It works.

Claims (4)

In the manufacturing method of the non-baking pellet which mainly pulverizes the compounding raw material which has a fine iron ore or iron-containing dust, and added the hydraulic binder, Selecting the use of non-fired pellets in either blast furnace or steelmaking; If the use of non-fired pellets is selected for the blast furnace, one or two or more conventional binders are added to the primary compounding material by 8 to 10 wt% based on the total blended raw material, and the use of the non-fired pellets is selected for steelmaking. In the case of the primary granulation step of adding one or two or more conventional binders to the primary blended raw material by 3 to 6wt% relative to the total blended raw material to the first granulation to 70-96% of the final particle diameter of the pellet; 5 ~ 20wt% of the crude steel cement for the secondary blended raw material is added to the secondary blended raw material, and the secondary blended raw material with the roughened steel cement is attached to the surface layer of fresh pellets assembled in the primary granulation step. A secondary assembly step of secondary assembly to pellet final particle diameter; And Method for producing non-plastic pellets comprising the step of curing the second pellets assembled pellets in the secondary assembly step The method for producing non-plastic pellets according to claim 1, wherein the binder added to the blending raw material in the first granulation step is one or two or more selected from the group consisting of cements, slags and quicklime hydraulic materials. The method for producing non-fired pellets according to claim 2, wherein the cements are composed of Portland cement, cemented steel cement, cement clinker, and blast furnace cement, and the slag is blast furnace quenching slag. delete