CN1077752A - Sintered ore for ironmaking using pea stone iron ore as raw material and method for producing the same - Google Patents

Abstract

When iron-containing raw materials such as iron ore, carbonaceous materials, and water are sintered with a sintering machine, as iron-containing raw materials other than returning ore, 40 to 70% (weight) of pea stone iron ore and _SiO2 less than 1.5% by weight of high-grade iron ore was sintered, and as a result, in the cross-section of sintered ore, the unmelted residue of sintered raw materials except pea stone iron ore was produced, and more than 80% of the solid part was composed of particles with a size of less than 10 μm. Densified peastone iron ore surrounded by finely divided calcium ferrite, or consisting of granular hematite particles with traces of peastone iron ore and calcium ferrite binding the granular hematite particles to each other, or a mixture thereof of sintered ore.

Description

The invention relates to a sintered ore for blast furnace ironmaking which uses pea stone iron ore as a raw material and a manufacturing method thereof.

The pig iron smelting method in the blast furnace is a representative method of iron smelting, and the sintered ore as its main raw material is generally manufactured as follows. First, add CaO-containing auxiliary materials such as limestone, dolomite, and converter slag (called CaO-based auxiliary materials), and _SiO2 -containing auxiliary materials such as serpentine, silica, and olivine ( It is called SiO ₂ series auxiliary raw material), and carbonaceous materials such as coke powder and anthracite, and then mixed and granulated after adding an appropriate amount of water. Fill the mixed raw materials (pseudo-particles) after such pseudo-granulation on the trolley of the grate mobile sintering machine at a height of about 500mm, ignite the carbonaceous material on the surface of the packed bed, suck air downward and make it The carbonaceous material is burned, and the matching raw materials are sintered by the combustion heat generated at this time, and the resulting sintered blocks are broken and sized, and the 3-5mm particles are loaded into the blast furnace as finished sintered ore. The powdery sintered ore that is not suitable for loading into the blast furnace is called returned ore, and it is used as the raw material of sintered ore again.

In order to operate the blast furnace stably and efficiently, high-quality sinter is required, and its properties such as cold strength, reducibility, and reduction pulverization resistance are strictly controlled. In addition, a high yield rate (finished sintered ore/agglomerate) is expected from the viewpoint of production cost of sintered ore.

Examining the world's iron ore resources, due to the depletion of high-quality hematite in the past, it is predicted that if production continues as it is, the main mines will be exhausted before 2000. On the other hand, there is bean stone iron ore classified as a kind of iron ore, which is iron ore containing SiO ₂ 4.5-6%. Its representative is the iron ore named after Yandicoojina produced in Robe River, Australia. Because this kind of iron ore has a large amount of burial in the deposit, and because the low-grade part removed during mining (strip ratio) is small, the mining cost is low, and it has the characteristics of stable supply. Therefore, if this ore is used in large quantities, not only economic effects such as cost reduction can be obtained, but also it is of great significance to make full use of resources.

However, since this ore has a so-called fish egg structure in which hematite (Fe ₂ O ₃ ) particles are surrounded by goethite particles (Fe ₂ O ₃ ·H ₂ O), there are many problems. That is, the decomposition of crystal water is caused during the heating process, and large cracks are selectively generated in the goethite part. The first is that the ore becomes brittle. Next, molten liquid is generated by the reaction of the auxiliary raw material and the iron ore, and the molten liquid rapidly intrudes into the cracks, and large pores are formed in the molten liquid portion, thereby reducing the strength of the sintered body. In the sintering operation, the said yield and cold state strength are reduced. In addition, the assimilation part (the part where the melt reacts with the ore) generates small granular hematite particles and vitreous silicate, which deteriorates the resistance to low-temperature reduction pulverization. Therefore, the usage of pea stone iron ore has not increased. As described above, the development of a sintering method using a large amount of pea stone iron ore is of great significance in view of efficient use of resources and cost reduction.

The basic countermeasure for pea stone iron ore is to suppress the rapid intrusion of a large amount of molten liquid into the above-mentioned cracks. As a method of suppressing the rapid immersion of this molten liquid, the inventors have explained the method of forming a protective layer with a special composition structure on the surface around the ore as described in Patent Application No. 1-184047 and No. 2-115730, and as described in Patent Application No. 3 -146481 and the method of forming a high-viscosity molten liquid described in Ping 3-303854. However, these methods also have the following disadvantages: special auxiliary raw materials are required, and equipment for segregating the special raw materials into pre-granulation equipment or sintering machines is necessary.

Therefore, the inventors of the present invention thought that the intrusion of the molten liquid could be suppressed if the molten liquid existing around the pea stone iron ore was limited to an extremely small amount, and conducted a lot of basic studies on the conditions for this purpose, and found that The method of the present invention is applicable as a specific countermeasure for an existing sintering machine.

That is, the object of the present invention is to provide a high-quality sintered ore using cheap and abundant iron ore, particularly pea stone iron ore.

Another object of the present invention is to produce high-quality sintered ore using the above-mentioned iron ore and without requiring special equipment.

In order to achieve the above-mentioned purpose, the present invention uses pea stone iron ore and high-grade iron ore containing SiO ₂ below 1.5% (weight) (hereinafter all represent weight) as iron-containing raw materials outside the returned ore, and will be equipped with 40 - The iron-containing raw materials of 70% bean stone iron ore, auxiliary raw materials, carbonaceous materials, water, etc. are sintered by a sintering machine under the heating condition of 1200° or more. On the cross-section of sintered ore, more than 80% of the unmelted residue of sintering raw materials other than pea-stone iron ore is provided with micro-densified pea-stone iron surrounded by fine calcium ferrite with a size of 10 μm or less. ore, ② granular hematite particles with traces of peastone iron ore and calcium ferrite binding the hematite particles together, or ③ a mixture of granular hematite particles and calcium ferrite, or A sintered ore for ironmaking consisting of a mixed structure of ①②③.

In addition, in the above-mentioned sintering method, as the iron-containing raw material other than the returned ore provided, less than 60% of the high-grade iron ore with a SiO ₂ content of 1.5% or less can be used with an Al ₂ O ₃ /SiO ₂ weight ratio of 0.3 The following iron ores are used instead, and the total amount of the above-mentioned pea stone iron ore, high-grade iron ore and low Al ₂ O ₃ iron ore can be compounded by more than 80%.

The sintered ore obtained in this way has the same excellent yield and performance as the high-quality hematite in the past.

In addition, all the % which shows a chemical composition below means weight.

Brief description of the drawings

Figure 1 shows the ratio of SiO ₂ in the iron ore, fine calcium ferrite and slag in the sintered ore with a size of 10 μm or less in the sintered ore produced by a single type of iron ore with a basicity of 1.6-2.2 in a sintering pot relation chart.

Figure 2 shows the ratio of Al ₂ O 3 /SiO 2 in iron ore and the ratio of Al ₂ O ₃ /SiO ₂ in iron ore in sintered ore produced by sintering pot with a single variety of ore with an alkalinity of 1.6-2.2. The proportion relationship diagram of fine calcium ferrite and slag with the size less than 10μm.

Fig. 3 shows the microstructure diagram of the sintered ore of the present invention.

Fig. 4 shows another microstructure diagram of the sinter of the present invention.

Fig. 5 shows yet another microstructure diagram of the sintered ore of the present invention.

Fig. 6 shows a microstructure diagram of an example of a conventional sinter.

Figure 7 shows the results of the sintering pot test using pea stone iron ore and iron ore with SiO ₂ less than 1.5% as raw materials, the proportion of pea stone iron ore and the yield of finished products in the sum of the two iron ores Relational graph of yield and JIS drop strength of sintered ore.

Figure 8 shows that in the sintering pot test, in the raw material composed of pea stone iron ore and iron ore with _SiO2 less than 1.5%, the proportion of pea stone iron ore is 40% or 70%, and the SiO2 ₂ When a part of the iron ore less than 1.5% is replaced by iron ore with a weight ratio of Al ₂ O ₃ /SiO ₂ less than 0.3, the relationship between the replacement rate, the yield of the finished product, and the JIS drop strength of the sintered ore picture.

Figure 9 shows that in the sintering pot test, in the raw material composed of pea stone iron ore and iron ore with SiO ₂ less than 1.5%, the proportion of pea stone iron ore was 40% or 70%, followed by the SiO2 ₂ 60% of iron ore less than 1.5% is replaced with iron ore with Al ₂ O ₃ /SiO ₂ weight ratio less than 0.3, and a part of the raw material is replaced with iron with Al ₂ O ₃ /SiO ₂ weight ratio greater than 0.3 In the case of ore substitution, the relationship between the substitution rate, the finished product yield, and the JIS drop strength of sintered ore.

The best mode for carrying out the present invention will be described in detail below.

First, the basic principle of the present invention will be explained.

As mentioned above, the feature of the present invention is to suppress the actually existing melt which changes momentarily to an extremely small amount. The basic principle is that starting from the heating stage of the sintering process at about 1200°C, due to the reaction of solid and liquid, the initial calcium ferrite (in the form of needles or flakes with a size of 10 microns) is promoted. This calcium ferrite is formed as soon as the CaO/SiO ₂ melt is produced, resulting in a so-called melt generation rate, but the amount of actually existing melt becomes extremely small. The present invention pursues the characteristics of ore and the generation of calcium ferrite thereof.

First, the inventors conducted a single-species sintering test. The test used iron ore and limestone and adjusted CaO/ _SiO2 within the range of 1.6-2.2 of the usual sintered ore, and ground sintered ore particles of about 20mm in size. The proportion of fine calcium ferrite with a size of 10 μm or less was quantified using an optical microscope with a television camera and an image analyzer. 4% coke powder is still added in the ingredients.

As a result, in order to generate the above-mentioned fine calcium ferrite, it is necessary to have a high CaO/SiO ₂ in the melt, and it is important to take a low value of SiO ₂ % in iron ore, or take a low value of SiO 2 % in iron ore. The SiO ₂ portion in quartz (SiO ₂ ) or clay (SiO ₂ -Al ₂ O ₃ ) is not easily dissolved into the melt. As a result of various investigations on ore containing 0.5-7.6% SiO ₂ about the degree of difficulty of melting, it was confirmed that the ore is sorted by the ratio of Al ₂ O ₃ /SiO ₂ in the ore.

Figure 1 shows the relationship between SiO ₂ % in iron ore and the amount of fine calcium ferrite with a size below 10 μm and slag. The amount of calcium ferrite slag is considered to be corresponding to the actual amount of molten liquid. From this result, SiO ₂ in iron ore below 1.5% plays a good role in the formation of fine calcium ferrite. Figure 2 is related to the iron ore containing 0.5-7.6% SiO ₂ that is usually introduced, and shows the relationship between the weight ratio of Al ₂ O ₃ /SiO ₂ in the iron ore and the amount of fine calcium ferrite and slag with a size below 10 μm. When the amount of fine calcium ferrite and slag is about the same as that of iron ore containing less than 1.5% of SiO ₂ , Al ₂ O ₃ /SiO ₂ is less than 0.3, and iron containing this Al ₂ O ₃ /SiO ₂ value can be The ore replaces the ore containing less than 1.5% SiO ₂ .

On the basis of the above insights, the CaO/SiO ₂ (basicity) of sintered ore is adjusted according to the usual range of 1.6-2.2 for pea stone iron ore, and for low SiO ₂ iron ore with SiO ₂ content less than 1.5%. A variety of mixed raw materials were sintered. Add 4% coke powder as solid fuel to the raw materials.

The test results show that in the obtained sinter, when the proportion of pea stone iron ore accounts for 40 to 70%, a mineral structure with different characteristics from the past is obtained. This structure is shown in Fig. 3 to Fig. 5 . In addition, the mineral structure of the pea stone iron ore part in the sintered ore when the conventional method is used is shown in Fig. 6 as a comparison.

In the coarse-grained peastone iron ore of about 2 mm or more, ① as shown in Figure 3(a), the unmelted beanstone iron ore is densified, and its periphery is changed from 10 μm or less as shown in Figure 3(b). Surrounded by fine calcium ferrite, or (2) as shown in Figure 4(a), there are traces of the original shape of pea stone iron ore, and the whole body is completely assimilated by melting, granular hematite particles and ferric acid bound to the particles Calcium precipitation (Fig. 4(b)). In addition, structures ① and ② are mixed in some sinter particles. In addition, the fine-grained bean stone iron ore powder or intermediate particles attached to other raw materials below about 0.5 mm, ③ as shown in Figure 5, consists of granular hematite particles and calcium ferrite (as a part of the extreme size grow up to 20-30μm), which is roughly similar to the structure in Figure 4 of the previous coarse pea stone iron ore part. That is, calcium ferrite is combined with the organization as its characteristic.

In the production of sintered ore for ironmaking, the sinter bed maintains air permeability, that is, in order to ensure the combustion of coke, the method of not completely melting all the raw materials is adopted so as not to block the voids. Thus, a part of the raw material remains unmelted. Figure 5 is a deliberate photograph of the surface of the unmelted ore. In addition, since the coke powder with a wide particle size distribution and MgO-containing raw materials such as serpentine are mixed with the iron-containing raw materials, calcium ferrite will not form around these coarse particles theoretically. In addition, 20 samples with a size of about 20mm were randomly selected from the sintering test 1 for analysis. In each particle cross section, the ratio of each structure was obtained and averaged for the solid part No. 1-6 of the unmelted material except the soy stone iron ore. The results are shown in Table 1.

Table 1 Bean stone iron ore and low SiO ₂ (≤1.5%) iron ore

Combined sintering test results (CaO/SiO ₂ =1.6)

No. Bean stone iron ore ratio Organization ① Organization ② Organization ③ Organization ④ Organization ⑤ Organization ⑥

1 30% 5% 10% 49% 10% 7% 19%

2 40% 16 16 50 4 2 12

3 50% 16 19 46 5 3 11

4 60% 18 20 45 4 2 11

5 70% 19 22 41 5 3 10

6 80% 17 12 33 6 9 23

Remarks: Organization ①... Densified pea stone iron ore particles surrounded by fine particles with a size of less than 10 μm

Tissue ②...with traces of bean stone iron ore particles, assimilated on granular hematite particles and calcium ferrite

Organization ③...Granular hematite particles and calcium ferrite

Organization ④...Granular hematite particles and vitreous silicate

Organization ⑤...Magnetite particles, calcium ferrite and vitreous silicate

Organization ⑥...Re-oxidized hematite particles, magnetite particles, calcium ferrite and vitreous silicate

It can be seen from Table 1 that since the proportion of No.2-5 bean stone iron ore is 40%-70%, the area ratios of structures ①, ② and ③ are large, totaling more than 80%. In addition, No. 1 has a small proportion of 30% pea stone iron ore _, and its structure ④ and structure ⑥ increase. In addition, in the case of No. 6 with pea stone iron ore ratio of 80% and higher, the structure 6 increases, which can be considered to be due to the impeded gas permeability of the material bed resulting in non-uniform combustion.

In the past sintered ore, as shown in Figure 6(a), the unmelted residual pea stone iron ore was in the shape of concentric circles or large cracks were formed from the surface to the center, and there were many different types of iron ore around it. Surrounded by shaped pores, the wall thickness between the pores is extremely thin, forming an extremely brittle structure. In addition, the porous part surrounding the residual pea stone iron ore has a structure of vitreous silicate combined with granular hematite particles as shown in Fig. 6(b), which has the characteristics of low-temperature reduction pulverization and poor reducibility. The aforementioned binding phases in Figures 3 to 5 are calcium ferrite, which is known to have good resistance to low-temperature reduction pulverization and reducibility. In fact, the low-temperature reduction resistance index (RDI) was 37±3 in the past method, compared with 34±2 in the present invention, which is greatly improved. In addition, the pore structure shown in Figures 3-5 is not amorphous but circular, and the thickness of the pore partition wall increases, and the strength also becomes higher. The change of the pore structure is closely related to the fluidity of the molten liquid. Since the calcium ferrite-based molten liquid has high fluidity, it has a unique relationship with the formation of the calcium ferrite bonded phase.

The results of the sintering pot test for the raw material consisting of pea stone iron ore and iron ore with _SiO2 less than 1.5% are shown in Fig. 7. When the ratio of the pea stone iron ore characterized by the above-mentioned calcium ferrite bond phase is 40-70%, the yield of sintered ore and the significant improvement in cold strength (JIS drop strength) are obvious. In addition, when the low SiO ₂ iron ore ingredients are greater than 70%, the yield is greatly reduced, which is due to less SiO ₂ and a decrease in the melt forming the bonded phase.

Next, the low-SiO ₂ iron ore in the above batch was replaced with low-Al ₂ O ₃ ore with Al ₂ O ₃ /SiO ₂ less than 0.3, and a sintering test was carried out. Since the basicity of sintered ore tends not to change within 1.6-2.2, the case of basicity 1.6 is shown in FIG. 8 . If the ore with low Al ₂ O ₃ is used for replacement and the replacement rate is controlled below 60%, the yield and the maintenance of cold strength are obvious. In addition, when the substitution rate is 60% or less, the sintered ore structure is substantially the same as that in FIGS. 3 to 5 , but the ratio of fine calcium ferrite of several μm or less increases.

In the actual sintering operation, the amount obtained from the ore origin is insufficient due to strikes on the mine site and other reasons.

For this reason, to what extent are the above _- mentioned "combined raw materials of soy stone iron ore and low- _SiO2 iron ore" and "combined raw materials of soy stone iron ore, low- _SiO2 iron ore and low _Al2O3 ore" It can be replaced by "iron ore with Al ₂ O ₃ /SiO ₂ greater than 0.3". The results of the sintering test are shown in Figure 9. In addition, since this result does not show a big difference by alkalinity, the result of alkalinity 1.9 is shown. The amount of coke powder added in this experiment was 4%. It can be seen from Fig. 9 that when the substitution rate reaches 20%, the yield only decreases slightly, while the cold strength remains unchanged. That is to say, as iron-containing raw materials other than returned ore, high-grade iron ore with a SiO ₂ content of less than 1.5% and iron ore with a weight ratio of Al ₂ O ₃ /SiO ₂ less than 0.3 are mixed in a total amount of more than 80%, both of which can be obtained The above organizations ①, ②, ③.

The effect of the present invention is illustrated below with examples. The mineral structure is a mixture of Figure 3-Figure 5, with a total of more than 80%.

Example 1

Table 2 is the representative batching (hematite ore as the main body) and its sintering operation results in the existing practice. Condition A in Table 3 is sintering with only bean stone iron ore, and condition B is the case where the raw materials in Table 2 are used for sintering, and the proportion of bean stone iron ore in the new raw material is 30%. In addition, conditions C and D are examples of the results of sintering operations according to the method of the present invention. In the case of a single variety of bean stone iron ore, the yield, productivity and cold strength are significantly lower, and when the proportion of bean stone iron ore in the new raw material is 30%, the yield is worse than that in Table 2. On the other hand, according to the conditions of the present invention through the coordination of SiO ₂ iron ore less than 1.5% as shown in conditions C and D, shown by Table 2 obtained with the existing average yield, productivity, cooling properties of equal strength.

Table 2 Representative batching conditions (dry basis) and sintering operation results in practice

＊Proportion relative to new raw materials (%)

Table 3 According to the present invention a large amount of sintering operation results using pea stone iron ore

＊Return ore and coke are relative to the proportion of new raw materials (%)

Remarks: Chemical composition of iron ore

Example 2

Table 4 shows that in the raw materials composed of pea stone iron ore and low SiO ₂ iron ore containing SiO ₂ less than 1.5%, the iron ore with Al ₂ O ₃ /SiO ₂ less than 0.3 is used for a part of _the low SiO 2 ore Stone is replaced within the scope of the conditions of the present invention, in such cases the result of sintering. In this case, the same results as in Table 2 are generally obtained.

Table 4. Examples of operating results by the method of the present invention

＊Return ore and coke are relative to the proportion of new raw materials (%)

Example 3

Table 5 lists the sintering results obtained when a part of the iron ore mixed raw material in Table 4 is replaced by iron ore with Al ₂ O ₃ /SiO ₂ greater than 0.3. In this case, the yield and productivity were slightly lower than those of the usual raw materials in Table 2, but were much higher than those of Conditions A and B in Table 3. In addition, the cold strength is roughly unchanged compared with Table 2.

＊Return ore and coke are relative to the proportion of new raw materials (%)

As described above, if the present invention uses a large amount of bean stone iron ore, which has been considered to cause low yield and quality of sintered ore in the past, it is possible to obtain the same results as in the past. The depletion of past quality hematite ore is evident. As the method of the present invention that can use a large amount of abundant and low-priced pumice iron ore, it solves the problem of its resources, and great expectations are placed on the reduction of the ironmaking coke ratio.

Claims (5)

1, ironmaking agglomerate, it is characterized in that, in the section of agglomerate, raw materials for sintering except the peastone iron ore is the fusion residue not, its solid partly is the peastone iron ore that is surrounded densification by calcium ferrite more than 80% (weight), perhaps have peastone iron ore vestige and constitute, or constitute by their mixture by granular hematite particle and calcium ferrite that this rhombohedral iron ore particle is combined.

2, the ironmaking agglomerate of claim 1 is characterized in that it is to be mixed by above-mentioned agglomerate tissue and granular hematite particle and calcium ferrite tissue to constitute.

3, ironmaking is characterized in that with the manufacture method of agglomerate, with sinter machine iron-bearing material such as iron ore and auxiliary material, carbonaceous material and water being carried out in the manufacture method of agglomerating sintered ore for iron-smelting, uses the peastone iron ore and contains SiO ₂Less than 1.5%(weight) the high grade iron ore as the iron-bearing material beyond returning mine, and allocate peastone iron ore 40～70%(weight into).

4, the ironmaking sintering mine making method of claim 3 is characterized in that, as the iron-bearing material beyond returning mine, with SiO ₂Content less than 1.5% high grade iron ore less than 60%(weight) use Al ₂O ₃/ SiO ₂Part by weight replaces less than 0.3 iron ore.

5, the ironmaking sintering mine making method of claim 4 is characterized in that, as the iron-bearing material beyond returning mine, with the peastone iron ore, contain SiO ₂Less than 1.5%(weight) high grade iron ore and Al ₂O ₃/ SiO ₂Part by weight less than 0.3 iron ore total amount greater than 80%(weight) mode prepare burden.

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