KR100226944B1 - Method for manufacturing non-sintering pellet - Google Patents

Abstract

The present invention relates to a method for manufacturing non-fired pellets by mixing iron ore or iron-containing dust mainly with a hydraulic binder, and utilizing waste resources by using lime sludge, which is discarded in steel mills, as an additive water for assembling. To provide a method for producing non-fired pellets that can improve the strength of the non-fired pellets, and its purpose is to.

The present invention is a method for producing non-plastic pellets by mixing iron ore or iron-containing dust and the hydraulic binder, and then adding the granulated additive water to assemble the blended raw material, and curing to add non-plastic pellets, which is added instead of the granulated additive water. The manufacturing method of a high strength non-baking pellet is made into the summary.

Description

[Name of invention]

Manufacturing method of high strength non-fired pellet

Detailed description of the invention

[Purpose of invention]

[Technical field to which the invention belongs and the prior art in that field]

The present invention relates to a method for producing non-fired pellets mainly composed of iron ore or iron-containing dust, and cement and steel slag as binders, and more particularly, to fabricate lime sludge that has been disposed of in steel mills. It relates to a method for producing high strength non-fired pellets using.

Lime sludge is a material that is disposed of in steel mills, and the process of collecting fine dust generated in the process of washing impurities of limestone with water to collect dust containing flue gas from the process of making lime and raw lime made of limestone as water. And sludge mixed with them. Because this slurry is bulky, it cannot be disposed of as it is.The slurry is concentrated in a concentration tank, and then made into a sludge cake having a water content of about 30% dehydrated by a press filter or a vacuum drum filter, and then landfilled in a landfill site. It is recirculated and used as process water to supplement only evaporation.

On the other hand, in the steelmaking process, non-plastic masses mainly composed of powdered iron ore or iron-containing dusts and hydraulic binders are used for cements (usually cement, cement clinker, crude steel, etc.) as binders for main raw materials such as fine iron ore and dust. Cement) or slag and additives (blast furnace slag, gypsum, quicklime, etc.) are mixed in a mixer, and the raw material is supplied to a motorized granulator (disc pelletizer, drum pelletizer). After sprinkling, the raw materials are assembled to a predetermined size, and then placed in a predetermined place to cure, thereby producing a solid mass. It is generally known that non-fired pellets produced in this way have a greater effect in terms of reduction in manufacturing cost and reduction of pollution compared to other photonic production methods.

According to the patents and operating techniques disclosed so far regarding the manufacture of non-fired pellets, the most necessary quality for non-fired pellets used as a charging material for steel and steelmaking is strength, and in general, the blast furnace is about 150 kgf or more, Steelmaking is managing the target strength of about 30-50kgf or more. The amount of cement or crushed slag added to prepare such non-plastic pellets of practical strength is about 10% by weight for blast furnace pellets and about 5% by weight for steelmaking pellets. The use of crude steel cements takes about 10 days, and usually cements require up to about 28 days for long periods of time. Therefore, improvement measures to increase the strength of non-fired pellets are required.

Solid particles separated from lime sludge, that is, sludge, can be regarded as a useful raw material because they are similar to limestone ores due to their chemical composition, but are discarded due to the following problems. In other words, the sludge has extremely fine particle size and high water content, so that it is difficult to recycle it for steelmaking or other materials because it has poor handling properties such as transportation, mixing, and classification, and it is sintered when dried and crushed in a separate facility. It can be used as a solvent or a raw material for other purposes, but it is eventually disposed of because of the processing cost.

On the other hand, in the non-fired pellet manufacturing process, as a known technique (NKK Technical Report, 1984, No. 40, p. 77, NKK-CORAC Process) for shortening the curing time until the required strength is reached, pellets in a two-stage reactor There is a way to charge and nurture. In this method, raw pellets discharged immediately after assembly from the pelletizer are charged into a primary reactor, and a dry-steam curing-carbonation reaction occurs at a temperature of 150 ° C. or lower. When the pellets are discharged after controlling the carbonation reaction at a temperature below ℃, the final product pellets have a strength of about 150 kgf or more through a short curing time of about 10 hours. There is a disadvantage that a lot of auxiliary equipment such as gas supply device takes. On the other hand, when the cement is usually replaced with the crude cement as a binder, the curing period is shortened, but since the price of the crude cement is significantly high, it is difficult to replace it by a certain amount or more.

Therefore, the present inventors conducted research and experiments to solve the above-mentioned problems of the prior arts, and based on the results, the present invention proposes the present invention mainly based on iron ore or iron dust, and a hydraulic binder. In the step of assembling non-fired pellets, lime slurry, which is discarded in steel mills, is used as an additive water for assembling, thereby providing a method for producing non-fired pellets that can improve utilization of waste resources and strength of non-fired pellets. The purpose is.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention is a method for producing non-plastic pellets by mixing iron ore or iron dust and the hydraulic binder, and then adding the granulated additive water to assemble the blended raw material, and curing to produce a non-plastic pellet, Ca ^{+ 2} : 165-607ppm, pH: 9.3-12.2 and solids: relates to a method for producing a high-strength non-fired pellet characterized by adding a lime slurry containing 3.5-43% by weight.

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

The inventors have conducted a series of experiments in which lime slurry is used as an additive water used when assembling non-fired pellets. When the lime slurry is added to the raw material of the non-fired pellets and assembled, the inventors recover the useful components in the lime slurry, The effect of improving the strength of the pellet was confirmed.

In the manufacture of non-fired pellets, a mixture of a hydraulic material such as cement, slag and gypsum or quicklime as a binder is mixed with a raw material mainly composed of powdered iron ore or iron dust, and the mixture is a disk or a drum. At the same time, the raw pellets are sprinkled with lime sludge while being supplied to a pelletizer of a type, and the pellets are discharged to the pelletizer, and then the final curing is performed to prepare a non-plastic pellet.

When preparing non-plastic pellets according to the present invention, hydraulic binders must be used as binders.

Examples of the hydraulic binder which can be preferably applied to the present invention include cements, a mixture of slag and lime or / and quicklime.

Examples of the cements include ordinary cement and crude steel cement, and examples of slag include blast furnace crushed slag and the like.

In the present invention, the lime slurry replaced with the granulated additive water preferably contains Ca ⁺² : 165-607ppm, pH: 9.3-12.2 and solids: 3.5-43% by weight.

Moreover, it is more preferable that the particle size of the solid has a particle size of 128 µm or less and 90% or more.

In the present invention, lime sludge which may be more preferably used is a slurry containing fine particle washing water generated in the process of washing impurities of limestone with water and dust-containing exhaust gas generated in the process of manufacturing limestone as raw material of limestone. Examples of the lime slurry in which the slurry generated in the process are mixed with each other may be mentioned, and the physical properties of the lime slurry and the dehydrated lime slurry are shown in Tables 1 and 2, respectively.

On the other hand, in general, in the production of non-fired pellets, the water content in the raw pellets prepared by adding water to the blended raw materials is largely varied by 5.15% depending on the type and size of raw materials.

In the case of producing non-fired pellets according to the present invention, it is preferable to add lime slurry so that the water content in the granulated raw pellets is 5 to 15%.

The general curing mechanism of non-plastic pellets with a hydraulic binder is as follows. The strength of the initial raw pellet stage in non-plastic pellets is characterized by the interfacial chemical and capillary forces between the added water and the finely divided particles for granulation, and the added binder dispersed in the colloidal phase by the water to fill the four pores of the pellet. In the subsequent curing process, the strength of the pellets varies somewhat depending on the binder. When cements are used as binders for non-plastic pellets, the strength of the pellets is mainly due to the hydration reaction between the cement component minerals and water, that is, CaO-SiO _2. CaO, CaO-SiO ₂ -Al ₂ O _3, etc. The compound is reacted with water to produce a hydrate such as CaO (OH) ₂ , CaO-SiO ₂ -H ₂ O system, CaO-SiO ₂ -Al ₂ O ₃ -H ₂ O system, or the like.

And if therefore the addition of slag materials and plaster as binding material is eluted CaO components from the slag and the Al ₂ O ₃ component, SiO ₂ components are in the presence of a _{CaSO 4 3CaO · Al 2 O 3} · 3CaSO 4 · 32H 2 O The compound It is known that the strength of the pellet is filled with hydrates of CaO-SiO ₂ -H ₂ O-based. Therefore, when using slag as a binder, generally, alkaline compounds such as quicklime, slaked lime and sodium hydroxide are selectively used in parallel to promote the hydration reaction of slag.

As in the present invention, when the lime slurry is used as the granulated water of the non-suited pellets, the strength of the pellet is improved because extremely fine dust particles exist in the slurry in the case of the lime slurry, and the aqueous solution is caused by quicklime. It is thought that Ca ions are dissolved. That is, when lime slurry is used, fine particles in the slurry are well dispersed in the voids in the fillet, thereby increasing the packing density of the pellet, and Ca ions additionally present in the aqueous solution promote the hydration reaction of various hydraulic binders. In general, the role of the solution and the alkalinity of the aqueous solution increase the viscosity of the aqueous solution to increase the bonding strength between the particles.

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

EXAMPLE

In order to manufacture the non-fired pellets, titanium iron ore as a raw material of iron and dust generated in the sintering and blast furnace processes were mixed as shown in Table 3 below, and the binder was added at a constant amount of 10%, and the type thereof was shown in Table 4 below. As shown, three types were used, and the water added for granulation was a conventional freshwater as a comparative example and lime slurries as shown in Tables 1 and 2, which are inventive examples. Regardless of the type of water added, the water content of the raw pellets was 12%, which was cured while maintaining the moisture of the pellets at about 5% or more at room temperature. In order to investigate the effect of the inventive example, the compressive strength of the pellets on the 7th, 14th, and 21st days of the raw pellets and curing were measured, and the results are shown in Table 5 below.

As shown in Table 5, in the manufacture of non-plastic pellets, the addition amount of the hydraulic binder was the same, and the type thereof was changed. As a result, the compressive strength of the pellets showed a high tendency in the order of crude cement, ordinary cement, and slag mixture. Also in all three cases it can be seen that the replacement of the added water in the fresh water with lime sludge as in the present invention is an effective method for improving the compressive strength of the pellets.

In other words, the use of lime slurry discarded in steel mills as coarse water in the manufacture of non-plastic pellets improved the strength of the pellets compared to the case of using fresh water regardless of the type of hydraulic binder. It can be seen that the strength improvement effects of 7.1%, 6.6%, and 10.6% are obtained when the ordinary cement, the rough cement, and the slag mixture are used. Also. When lime slurry is used as the number of granulated water of non-plastic pellets, the improvement effect is different depending on the type of hydraulic binder. However, when the slag mixture is used as the binder according to the type of binder, the absolute value of the compressive strength is different. Although somewhat lower than the case, the compressive strength improvement effect can be seen that the largest.

Claims (3)

In a method of mixing iron ore or iron dust with a hydraulic binder, and then adding the granulated additive water to assemble the blended raw material, and curing the non-plastic pellet, Ca ⁺² : 165 instead of the granulated additive water. -607ppm, pH: 9.3-12.2 and solids: a method for producing a high-strength non-fired pellets, characterized in that the lime slurry containing 3.5-43% by weight is added. The method of claim 1, wherein the lime slurry has a particle size of less than 90% of the particle size less than 128u; And the amount of lime slurry is selected so that the water content in the assembled pellet stage is 5-15%. The slurry according to claim 1 or 2, wherein the lime slurry collects dust containing flue gas generated in the process of preparing lime and raw lime produced from limestone as a raw material. Method for producing a high-strength non-fired pellets, characterized in that the slurry produced in the process is a mixed lime slurry.