KR20000039462A - Method of manufacturing sintered ores having high ferro dose using steel manufacturing sludge - Google Patents

Abstract

PURPOSE: A method of manufacturing sintered ores having high ferrite content is provided to improve the quality and productivity of sintered ores by mixing and sintering lime sludge in a process of sintering steel manufacturing sludge and limestone. CONSTITUTION: A sintered substance with hemi-calcium ferrite as a main ore is produced by mixing steel-making sludge and lime sludge at a ratio of 0.5-2.0:1 and sintering the sludge at a temperature of 1150-1250°C. After that, the sintered substance is crushed and replaced with the limestone lower than 30%. Therefore, the combination between particles of ores is easily performed and heat loss is reduced.

Description

Sintered ore manufacturing method with high iron content using steelmaking sludge

The present invention relates to a method for producing a sintered ore having a high Fe content while improving the quality and productivity of the sintered ore as a raw material for steelmaking blast furnace, and the limestone sludge generated in the steelmaking sludge and the limestone firing process generated in the steelmaking process. The present invention relates to a method for producing a sintered ore using mixed firing to manufacture a sintered compact and use it as a sintering raw material.

At present, many technical developments have been attempted in connection with the treatment and recycling of various wastes generated in the industrial field in relation to environmental regulations that are intensifying worldwide.

Most of the wastes generated in the steelmaking process, such as sintering, blast furnace, and steelmaking, contain components that adversely affect the steelmaking process.

However, when the proper treatment process considering the physical and chemical properties of these wastes is applied, it contains a large amount of valuable components that can be used as raw materials for steel.

In the case of Pohang Steel, the steelmaking sludge produced during the steelmaking process is about 400,000 tons per year, and 50% of the production is made of mini pellets, cold pellets, briquettes, etc. It is reused in processes and the rest is sold at low cost as it is.

In addition, limestone sludge generated in the process of washing limestone generates about 200,000 tons per year, but only 40% of the mini pellets are produced due to the fact that secondary dust is generated during transportation and handling. ), And the rest is landfilled.

However, steelmaking sludge and limestone sludge contain a large amount of valuable components as shown in Table 1, and when it is recovered by applying the appropriate process, it can be used as a raw material of the steelmaking process with a high added value than the conventional recycling method.

(Unit: weight%) division T.Fe SiO ₂ Al ₂ O ₃ CaO (CaCO ₃ ) MgO (MgCO ₃ ) Mn Zn C S K ₂ O + Na ₂ O Average particle size (mm) Steel Sludge 74.5 1.99 0.35 7.66 0.35 0.40 0.06 2.1 0.02 0.19 0.49 Limestone sludge - 2.71 0.42 (93.78) 2.85 - - - - 0.24 0.12

As a method of recycling various dusts and sludges generated in the existing steel making process (Method of Patent No. 100138) from limestone sludge, sintered electrostatic dust containing Fe ₂ O ₃ component, CaCO ₃ and A method of preparing and sintering a limestone and dolomite powder sludge containing a large amount of MgCO ₃ in a constant ratio to produce a sintered body in which calcium ferrite and magnesio calcium ferrite are the main minerals and reusing it as a sintering raw material (Patent application 94-35832 , 95-56113).

Recycling steelmaking sludge is a method of natural drying, crushing, blending with other dusts and sludges, and reusing in sintering and blast furnace processes.However, in this method, environmental pollution, Due to problems such as deterioration of quality due to the change of components during blending, erosion of refractory by alkali components such as K ₂ O and Na ₂ O and deterioration of efficiency of electrostatic precipitator, they have recently been dried and shredded It is agglomerated into pellets and briquettes and reused as raw materials for sintering, blast furnaces, and converter coolants.

In the blast furnace operation to produce pig iron, most of the raw material used (about 80%) is sintered ore. Therefore, quality control and productivity of sintered ore are the most important factors for the smooth operation of the blast furnace.

The sintering process adopted for the roasting and sintering of lead coal was originally a suction suction sintering machine, and its raw materials are iron ore, limestone, silica, serpentine, and powdered coke. In the process of transferring the heat, the so-called molten type, which reacts and melts the surrounding iron ore and by-products by the combustion of powdered coke, and solidifies the melt by cold air continuously flowing from the top, so-called melting type. Sintering method.

Therefore, the components forming the melt and the mineral phases generated during cooling have a great influence on the quality of the sintered ore. The main mineral phase of the sintered ore thus prepared is composed of hematite, magnetite, calcium ferrite, calcium silicate and slag.

It is well known that calcium ferrite is the most important binder in soluble sintered ore. Iron ore and limestone used as sintering raw materials are known to react with each other in the sintering process to form calcium ferrite having various compositions as follows.

Calcination of limestone: CaCO ₃ → CaO + CO ₂ --- (1): lime formation

Reaction of iron ore with limestone: CaO + Fe ₂ O ₃ → 2CaO · Fe ₂ O ₃ --- (2)

¡Æ CaO · Fe ₂ O ₃ --- (3)

¡Æ CaO ₂ Fe ₂ O ₃ --- (4)

Di calcium-ferrite, Mono calcium-ferrite and Hemi calcium-ferrite of (2), (3) and (4) are crystallized according to the state diagram composition. Or a precipitated mineral phase.

Limestone added as a sintering raw material reacts as in Formula (1) in the sintering process to generate quicklime, which is an endothermic reaction, so heat loss occurs because it absorbs a lot of heat in this process.

In addition, as the iron ore and limestone react to melt and crystallize, various kinds of calcium ferrites are formed around the iron ore as described above (2) to (4) to combine the mineral phases constituting the sintered ore.

In the case of artificially synthesizing the sintered body in which calcium ferrite is the main mineral in the outside and using it as a raw material for sintering, the reaction of iron ore and limestone is already performed because the (1) to (4) reactions are already performed during the manufacturing process of calcium ferrite. In the sintering process, the particles can be more easily bonded to each other than the calcium ferrite produced by the sintering process, and the heat loss due to the calcination reaction of limestone can be reduced. It is possible to manufacture high-quality sintered ore with high Fe content while saving raw materials.

Recent studies related to the production of sintered ore used as blast furnace raw materials are proceeding to improve the productivity of the blast furnace by increasing the content of Fe while maintaining the quality of the sintered ore.

In general, the amount of the raw materials used to manufacture the sintered ore is about 76% of the iron ore of the Fe component, and the amount of the subsidiary materials such as limestone, quicklime, and silica added for the component adjustment and the sintering reaction is about 24%.

In order to increase the Fe content of the sintered ore, the mixing ratio of the iron ore should be increased, but in this case, the amount of secondary raw materials is relatively small, making it difficult to adjust the composition of the sintered ore and reducing the bonding strength of the iron ore particles, thereby degrading the quality of the sintered ore such as room temperature strength do.

Therefore, technology development is progressing in order to maintain the quality and operation efficiency by adjusting the type and amount of additives while keeping the mixing ratio of iron ore constant, and the typical one of these methods is the existing sintered electrostatic dust and limestone sludge. Calcium ferrite is manufactured and replaced with limestone in the sinter feedstock.

In the conventional method of manufacturing a sintered body in which calcium ferrite is the main mineral phase using limestone sludge and recycling it in the sintering process, the total Fe content in the sintered electrostatic dust is about 40%, and when reacted with the CaO component in the limestone sludge, Mono calcium ferrite (Mono Calcium-ferrite: CaoFe ₂ O ₃ ), in which CaO and Fe ₂ O ₃ bond 1: 1, is produced as the main mineral phase.

However, when the same amount of steelmaking sludge is added to sintered electrostatic dust and reacted with CaO, CaO and Fe ₂ O ₃ are 1: 2 because the total content of Fe in steelmaking sludge is about 75% higher than that of sintered electrostatic dust. Hemi Calcium-ferrite (CaO.2Fe ₂ O ₃ ) can be produced as the main mineral phase, and sintered ore with higher Fe content can be produced compared to the existing method. In addition to the Fe component, the content of the Alkali component is more than 10 times higher than that of steelmaking sludge. Therefore, the present inventors have focused on the fact that the amount of the Alkali component is limited because the amount of the sintered ore decreases in efficiency and the efficiency of the sintering operation.

In the present invention, the steelmaking sludge and the limestone sludge are mixed and sintered to produce a sintered body in which hemicalcium ferrite having a high Fe content is the main mineral phase, and then replace it with limestone in the sintered raw material while maintaining or improving the productivity and quality of the sintered ore. The purpose is to provide a method for producing a sintered ore with a high Fe content.

In the sintered ore manufacturing method of the present invention for achieving the above object, the steelmaking sludge discharged during steelmaking industry and the limestone sludge generated during the washing of limestone are mixed at a ratio of 0.5 to 2.0: 1 and calcined at 1150-1250 ° C. to hemicalcium ferrite. A sintered compact is prepared as a main mineral, and is pulverized and replaced with limestone in the sintered raw material by 30% or less.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments.

Steelmaking sludge / limestone sludge was mixed at a ratio of 0.5 to 2.0 to produce briquettes, and then fired while changing the temperature at 50 ° C intervals in a temperature range of 1100 to 1300 ° C using an electric furnace capable of maintaining the temperature.

Table 2 shows the results of X-ray diffraction analysis to investigate the production phases according to the mixing ratio of steelmaking sludge / limestone sludge, and Table 3 shows the results of X-ray diffraction analysis to investigate the production phases according to the firing temperature change. It is shown.

Hemicalcium ferrite was the main constituent at the mixing ratio of steelmaking sludge / limestone sludge, and at less than 0.5, most of the steelmaking and limestone sludge were unreacted due to the nonuniformity of CaO and Fe ₂ O ₃ components and a small amount of calcium ferrite. Generated. When it exceeds 2.0, calcium ferrite is formed, and the remaining Fe ₂ O ₃ component is crystallized as hematite upon cooling, thereby reducing the amount of calcium ferrite produced.

In the case of the firing temperature, the reaction with calcium ferrite did not proceed due to the lack of calories at less than 1150 ° C. When the baking temperature was higher than 1250 ° C, calcium ferrite was produced, but a significant portion of the fired material appeared to be melted. It lowers the efficiency.

Therefore, the optimum firing conditions for the production of calcium ferrite were 0.5 to 2.0 of the steelmaking sludge / limestone sludge, and a calcination temperature of 1150 to 1250 ° C.

The hemicalcium ferrite prepared as described above was replaced with limestone, which is a sintering subsidiary material, with a 10 to 40% weight ratio, and a sintered simulation test was performed.

At this time, when the replacement ratio with limestone is 40% or more, it is difficult to adjust the composition of the sintered ore (base degree, SiO ₂ , CaO, MgO, etc.) on the basis of the normal sintering compounding ratio and lose the replacement effect.

Table 5 shows the sintering operation index, the quality of the sintered ore, and the total Fe content in the sintered ore measured after the sintering simulation experiments were carried out at the mixing ratios of Table 4.

As the replacement ratio of the crude preparation of the present invention to limestone increased from 0 to 30%, the total Fe content in the sintered ore was continuously increased to 56.2 to 58.3%, which makes it possible to manufacture a sintered ore having a higher Fe content than the conventional method. I could confirm it.

division Replacement ratio of preparations (% by weight) Fe component (wt%) of sintered ore Operation index quality Productivity (tons / day, ㎡) % Recovery Room temperature strength (TI,%) Reduction rate (RI,%) Reduction Differentiation Rate (RDI,%) Conventional example 0 56.2 34.1 75.2 71.3 65.8 38.5 Inventive Example 10 56.7 34.5 76.5 71.9 66.0 38.2 20 57.5 35.1 78.9 73.2 65.7 37.7 30 57.8 34.2 75.4 74.2 65.9 37.3 Comparative example 40 58.3 33.6 74.8 71.5 66.4 38.7

In the sintering operation index, when the replacement ratio with limestone was 20%, the productivity of sintered ore increased by 3% and the recovery rate was about 5%. At 30%, the replacement ratio was almost the same as that of the conventional method. It appeared to worsen somewhat.

In the case of sintered ore quality, room temperature strength and reduction differentiation rate gradually improved as limestone and replacement rate increased. At 30% replacement rate, room temperature intensity improved by about 4% and reduction differentiation rate by about 3%. There was no change in the case. The reason that the sintering operation index and quality deteriorates at an alternative ratio of 40% or more is that it is difficult to set the content of the components required for the sintered ore by the excessive addition of the preparation, which makes the structure of the sintered ore weak.

The reason why the sintering operation index and quality is improved by replacing the crude agent of the present invention with less than 30% of limestone is that the time required for melting of the subsidiary materials added during sintering is shortened, and at the same time, it is diffused and melted even with a small amount of heat. It is because of the effect of increasing the amount of binder relatively easy to facilitate interparticle bonding.

The reason why the quality of the sintered ore is improved is that the binding force between the particles of the sintered ore is improved by adding calcium ferrite, which is already artificially produced and whose structure is well controlled.

Therefore, as described above, according to the present invention, the hemicalcium ferrite is manufactured as a main mineral in the outside, and it can be used as a sintering material by replacing it with limestone to facilitate the interparticle bonding of the constituent minerals in the sintering process. It is possible to reduce the heat loss due to the calcination of the sintered ore can be produced with a high Fe content while saving fuel and raw materials, and the productivity and quality of the sintered ore can also be maintained or improved.

Claims (1)

In the production of sintered ore, which is a raw material of steel blast furnace, steelmaking sludge discharged during steelmaking operation and limestone sludge generated during washing with limestone are mixed at a ratio of 0.5 to 2.0: 1, and calcined at 1150 to 1250 ° C to prepare a sintered body. Sintered ore manufacturing method having a high Fe content, characterized in that the pulverized and replaced by limestone and less than 30% in the raw material.