Pellet produced by utilizing low-sulfur Mongolia concentrate and preparation method of pellet

Abstract

The invention provides pellets produced by using low-sulfur Mongolia concentrate, the content of TFe in the pellets is 62.5%-65.5%, the content of SiO2 is 3.0%-6.0%, and the reduction expansion rate of the pellets is less than 20%. The pellet is prepared from the following raw materials in parts by mass: 40-50 parts of iron ore concentrate, 10-50 parts of low-sulfur Mongolia concentrate, 10-60 parts of high-silicon iron concentrate, 1-3 parts of bentonite and 1-5 parts of silica stone. According to the method, low-sulfur Mongolian concentrates in different proportions are used for replacing outsourced concentrates, the production operation problem that raw materials for a large belt type pellet roasting machine are insufficient is solved, and the application effect is remarkable.

Description

Technical Field

[0001] This invention relates to the field of pellet preparation technology, specifically to a pellet produced using low-sulfur Mongolian concentrate and its preparation method. Background Technology

[0002] Utilizing a continuous equipment like a belt roaster to produce iron ore pellets is one of the mainstream methods for producing high-quality iron ore pellets in modern large-scale steel enterprises. By spreading green pellets onto a moving trolley and sequentially passing them through different process sections (drying, preheating, roasting, and cooling), finished iron ore pellets that meet the requirements of blast furnace smelting are ultimately obtained. Using a belt roaster to produce iron ore pellets offers advantages such as continuous and efficient production, high and stable product quality, high thermal efficiency, and good environmental performance.

[0003] Currently, large-scale belt roasting mills use a large amount of purchased concentrate in the production of ore pellets. The extensive use of purchased concentrate in belt pelleting negatively impacts pellet quality and the process itself. Specifically, the purchased concentrate is produced by numerous small, surrounding mines, resulting in a diverse range of feedstocks with poor moisture and chemical stability, and coarser particle size (below 70% -200 mesh), leading to poor pelletizing performance and consequently, lower green pellet quality. Therefore, there is an urgent need for a low-cost formula and process that produces high-quality green pellets that meet the requirements of blast furnace smelting. Summary of the Invention

[0004] The purpose of this invention is to provide a pellet production method using low-sulfur Mongolian concentrate, in which the performance of green pellets is guaranteed by adjusting the appropriate amount of low-sulfur Mongolian concentrate and silica during the production process.

[0005] According to one aspect of this application, a pellet produced from low-sulfur Mongolian concentrate is provided, wherein the pellet has a TFe content of 62.5% to 65.5%, a SiO2 content of 3.0% to 6.0%, and a pellet reduction expansion rate of less than 20%.

[0006] In some specific implementations, the pellets are prepared from raw materials comprising the following parts by weight: 40-50 parts iron concentrate, 10-50 parts low-sulfur Mongolian concentrate, 10-60 parts high-silicon iron concentrate, 1-3 parts bentonite, and 1-5 parts silica.

[0007] Among them, the low-sulfur Mongolian concentrate contains more than 32% FeO and less than 0.8% S.

[0008] In some specific implementations, the pellets are prepared from raw materials comprising the following parts by weight: 40-50 parts iron concentrate, 30-50 parts low-sulfur Mongolian concentrate, and 10-30 parts high-silicon iron concentrate.

[0009] In some specific implementations, the iron concentrate includes iron concentrate A and iron concentrate B, wherein the sulfur content in iron concentrate A is 0.5-0.6% and the sulfur content in iron concentrate B is 0.1-0.2%.

[0010] Specifically, the pellet also includes the following raw materials by weight: 30-40 parts of iron concentrate A and 10 parts of iron concentrate B.

[0011] According to another aspect of this application, a method for preparing pellets is provided, the method comprising the following steps:

[0012] 1) Mix the following raw materials in parts by weight: 40-50 parts iron concentrate, 10-50 parts low-sulfur Mongolian concentrate, 10-60 parts high-silicon iron concentrate, 1-3 parts bentonite and 1-5 parts silica evenly, and make green pellets on a pelletizing plate.

[0013] 2) Raw pellets are dried, preheated and roasted to obtain pellet ore.

[0014] In some specific implementations, in step 1), green balls are made on a φ1000mm surface. The green ball control parameters are: mother ball generation time is 2-4 min, green ball growth time is 5-10 min, and green ball compaction time is 8-12 min.

[0015] In some specific implementations, in step 1), green balls are made on a φ1000mm surface. The green ball control parameters are: mother ball generation time is 3 min, green ball growth time is 8 min, and green ball compaction time is 10 min.

[0016] In some specific implementations, in step 2), the roasting temperature is 1150℃~1210℃.

[0017] Specifically, in step 2), the roasting temperature is 1170℃.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) Through experimental research, this invention shows that under the condition of 30% iron concentrate A, when the proportion of low-sulfur Mongolian concentrate is 30%, 40%, and 50%, adding 1.2%, 1.4%, and 2.0% of silica can reduce the pellet reduction expansion rate to less than 20%, and the pellet quality meets the production requirements of belt pellets. Under the condition of 40% iron concentrate A, when the proportion of low-sulfur Mongolian concentrate is 10%, 20%, 30%, 40%, and 50%, adding 1.3%, 1.5%, 2.0%, 2.5%, and 3.5% of silica can reduce the pellet reduction expansion rate to less than 20%, and the pellet quality meets the production requirements of belt pellets.

[0020] (2) This invention uses low-sulfur Mongolian concentrate in different proportions to replace purchased concentrate, which solves the problem of insufficient raw materials for production and operation of large belt pellet roasters, and the application effect is significant. Attached Figure Description

[0021] Figure 1 Photographs of the mineral composition and structure of the reduced pellets after a 1:1 ratio;

[0022] Figure 2 Photographs of the mineral composition and structure of reduced pellets with a ratio of 1-2;

[0023] Figure 3 Photographs of the mineral composition and structure of the reduced pellets after mixing ratio 1-3;

[0024] Figure 4 Photographs of the mineral composition and structure of reduced pellets with a ratio of 1-4;

[0025] Figure 5 Photographs of the mineral composition and structure of the reduced pellets with a ratio of 1-5;

[0026] Figure 6 Photographs of the mineral composition and structure of reduced pellets with ratios 1-6;

[0027] Figure 7 Photograph of the mineral composition and structure of the reduced pellets of formulation 1A;

[0028] Figure 8 Photograph of the mineral composition and structure of pellets after reduction to ratio 1B;

[0029] Figure 9 Photographs of the mineral composition and structure of pellets after reduction with a 1C ratio;

[0030] Figure 10 Photographs of the mineral composition and structure of the pellets after reduction to 1D ratio;

[0031] Figure 11 Photograph of the mineral composition and structure of the reduced pellets with a 1E ratio;

[0032] Figure 12 Photographs of the mineral composition and structure of reduced pellets with a ratio of 2-1.

[0033] Figure 13 Photographs of the mineral composition and structure of reduced pellets with a ratio of 2-2.

[0034] Figure 14 Photographs of the mineral composition and structure of the reduced pellets after a ratio of 2-3;

[0035] Figure 15 Photographs of the mineral composition and structure of reduced pellets with a ratio of 2-4;

[0036] Figure 16 Photographs of the mineral composition and structure of reduced pellets with a ratio of 2-5;

[0037] Figure 17 Photographs of the mineral composition and structure of reduced pellets with a ratio of 2-6;

[0038] Figure 18 Photographs of the mineral composition and structure of the reduced pellets of formulation 2A;

[0039] Figure 19 Photographs of the mineral composition and structure of pellets after reduction with a 2B ratio;

[0040] Figure 20 Photographs of the mineral composition and structure of pellets after reduction with a 2C ratio;

[0041] Figure 21 Photographs of the mineral composition and structure of the reduced pellets in 2D for sizing.

[0042] Figure 22 Photographs of the mineral composition and structure of pellets after reduction with a 2E ratio;

[0043] The above Figures 1-22 In the image, the left photo is the edge photo; the right photo is the center photo. Detailed Implementation

[0044] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0045] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0046] Table 1. Chemical composition and particle size distribution of raw materials, %

[0047]

[0048] Low-sulfur Mongolian concentrate: Obtained by desulfurization of imported Mongolian ore through flotation. Its advantages include fine particle size, with -200 mesh accounting for 77.6%, making it suitable for pelletizing. It also has a low sulfur content and strong process adaptability.

[0049] Iron concentrate A (Bayan Obo iron concentrate): Particle size of -200 mesh reaches over 75.9%, and TFe can reach over 65%. Considering only particle size and grade, it is ideal for pellet production. However, studies have shown that when this ore is used in the pelletizing process, when the proportion exceeds 30%, it will lead to an increase in the reduction expansion rate of the pellets, or even abnormal expansion. Therefore, it limits its large-scale use in the pelletizing process.

[0050] Iron concentrate B (fixed iron concentrate): With a coarser particle size, -200 mesh accounts for only 54.2%. Its high price and presence of harmful elements such as arsenic and tin limit its large-scale use in pelletizing processes. Based on the requirement that the content of impurities tin, zinc, and arsenic in blast furnace feed should be below 0.08%, and considering that the removal rate of tin, zinc, and arsenic from pellets is extremely low under oxidizing atmospheres, resulting in excessive levels of tin and zinc in the pellets, which will adversely affect blast furnace and steelmaking production, the fixed iron concentrate ratio is set at 10%.

[0051] High-silicon iron concentrate: Concentrate purchased from external sources has poor stability in moisture and chemical composition, and coarser particle size, with -200 mesh content below 72.1%. However, compared to other iron materials used in pelletizing, it has a higher SiO2 content and a lower CaO content.

[0052] Test Plan

[0053] 1. Experimental scheme under the condition of 30% iron concentrate A ratio

[0054] (1) Experimental scheme for adding low-sulfur Mongolian concentrate

[0055] Table 2 shows a series of experimental schemes for gradually increasing the proportion of low-sulfur Mongolian concentrate under the condition of 30% iron concentrate A.

[0056] Table 2. Experimental scheme for adding low-sulfur Mongolian concentrate pellets, %

[0057]

[0058] (2) Experimental scheme for adding silica to inhibit pellet expansion rate

[0059] The experimental scheme shown in Table 3 below is to suppress the reduction expansion rate of pellets by adding 1.0%-2.0% silica when the proportion of low-sulfur Mongolian concentrate is 30%, 40%, and 50% under the condition of 30% iron concentrate A.

[0060] Table 3. Test scheme for inhibiting pellet expansion rate with silica addition, %

[0061]

[0062] 2. Test scheme under the condition of 40% iron concentrate A ratio

[0063] (1) Experimental scheme for adding low-sulfur Mongolian concentrate

[0064] Table 4 shows a series of experimental schemes for gradually increasing the proportion of low-sulfur Mongolian concentrate under the condition of 40% iron concentrate A.

[0065] Table 4. Experimental scheme for adding low-sulfur Mongolian concentrate pellets, %

[0066]

[0067]

[0068] (2) Experimental scheme for adding silica to inhibit pellet expansion rate

[0069] The experimental scheme shown in Table 5 below is to suppress the reduction expansion rate of pellets by adding 1.3%-3.5% silica in the following technical measures under the condition of 40% iron concentrate A and low sulfur Mongolian concentrate ratios of 10%, 20%, 30%, 40%, and 50%.

[0070] Table 5. Test scheme for inhibiting pellet reduction expansion rate by adding silica, %

[0071]

[0072] This experiment was conducted in a φ1000mm pelletizing pan. The raw materials from Tables 2, 3, 4, or 5 were mixed evenly and formed into green pellets on the pan. The green pellets were then dried, preheated, and roasted to obtain pelletized ore. The experimental process was controlled to simulate actual production process parameters. The pelletizing control parameters were: mother pellet formation time 3 min, green pellet growth time 8 min, and green pellet compaction time 10 min. The roasting temperature was 1150℃~1210℃. Based on past production experience, when the proportion of iron concentrate A in the pellet mix exceeds 40%, the pellet reduction expansion rate is greater than 20%, which does not meet the requirements of the pelletizing process. Therefore, the proportion of iron concentrate A was set at 30% and 40%.

[0073] Experimental Example 1: Analysis of green pellet quality under conditions of 30% and 40% iron concentrate A

[0074] 1. Quality analysis of green pellets under condition A (30% iron concentrate)

[0075] (1) Weight of green pellets with added low-sulfur Mongolian concentrate

[0076] Table 6. Weight of green pellets for pellets containing low-sulfur Mongolian concentrate

[0077]

[0078]

[0079] As shown in Table 6 above, with the increase of the proportion of low-sulfur Mongolian concentrate, the overall drop strength of green pellets does not change significantly, but the strength of both green and dry pellets shows a decreasing trend. Compared with the benchmark, adding 40% low-sulfur Mongolian concentrate reduces the drop strength by 0.4 drops / pellet, the green pellet strength by 5.13 N / pellet, and the dry pellet strength by 33.43 N / pellet. This is because low-sulfur Mongolian concentrate has poor pelletizing properties, and the quality of green pellets deteriorates as the proportion of low-sulfur Mongolian concentrate increases.

[0080] (2) Mass of raw silica pellets added

[0081] Table 7. Weight of green balls in silica pellets

[0082]

[0083] As can be seen from Table 7 above, adding different amounts of silica has little effect on the strength of green balls and drop strength. However, under the same low-sulfur Mongolian concentrate ratio, adding silica can improve the dry ball strength. Under the conditions of 30%, 40%, and 50% low-sulfur Mongolian concentrate ratio, adding 1.0%, 1.4%, and 1.8% silica respectively can increase the dry ball strength by 2.98 N / ball, 11.71 N / ball, and 10.64 N / ball respectively.

[0084] 2. Quality analysis of green pellets under condition A (40% iron concentrate)

[0085] (1) Weight of green pellets with added low-sulfur Mongolian concentrate

[0086] Table 8. Weight of green pellets for pellets containing low-sulfur Mongolian concentrate

[0087]

[0088] As shown in Table 8, with the increase of the proportion of low-sulfur Mongolian concentrate, the green ball strength does not change significantly, while the green ball drop strength and dry ball strength generally show a decreasing trend. Compared with proportion 2-1, when the proportion of low-sulfur Mongolian concentrate reaches 50%, the green ball drop strength decreases by 0.35 drops / ball, and the dry ball strength decreases by 11.3 N / ball.

[0089] (2) Mass of raw silica pellets added

[0090] Table 9. Mass of added silica green balls

[0091]

[0092] As can be seen from Table 9 above, adding 10%, 20%, 30%, 40%, and 50% low-sulfur Mongolian concentrate, along with different amounts of silica, has little effect on green ball drop strength, green ball strength, and dry ball strength.

[0093] Comprehensive analysis of the test results shows that, under the conditions of 30% and 40% iron concentrate A, the addition of different proportions of low-sulfur Mongolian concentrate and silica resulted in different changes in the quality of green pellets as the proportion of low-sulfur Mongolian concentrate increased. However, under the conditions of this test, all performance indicators of green pellet quality met the production requirements of belt pelleting.

[0094] Experimental Example 2: Analysis of Pellet Bursting Temperature under Condition A (30% and 40% Iron Concentrate)

[0095] 1. Analysis of pellet bursting temperature under condition A with 30% iron concentrate

[0096] The dynamic bursting test of green pellets was conducted on a tubular electric furnace. The test procedure was as follows: first, pellets of about 33 mm (particle size of 10-12.5 mm) were placed horizontally in a sample basket, and then placed into the preheated electric furnace. Air was introduced into the furnace from bottom to top, and the airflow velocity was controlled at 1.8 m / s.

[0097] (1) Analysis of the bursting temperature of pellets with added low-sulfur Mongolian concentrate

[0098] Table 10 Dynamic bursting temperature of green pellets with low-sulfur Mongolian concentrate.

[0099]

[0100] (2) Analysis of the bursting temperature of silica pellets

[0101] Table 11 Dynamic bursting temperature of added silica green pellets

[0102]

[0103] 2. Analysis of pellet bursting temperature under condition A with 40% iron concentrate

[0104] (1) Analysis of the bursting temperature of pellets with added low-sulfur Mongolian concentrate

[0105] Table 12 Dynamic bursting temperature of green pellets with low-sulfur Mongolian concentrate

[0106]

[0107]

[0108] (2) Analysis of the bursting temperature of silica pellets

[0109] Table 13 Dynamic bursting temperature of added silica green pellets

[0110]

[0111] As shown in Table 10-13, under the conditions of 30% and 40% iron concentrate A ratio, the addition of different proportions of low-sulfur Mongolian concentrate and silica resulted in green pellets with dynamic and static bursting temperatures greater than 700℃, indicating good thermal stability, which can meet the requirements of belt pellet production.

[0112] Experiment 3: Study on the chemical composition and metallurgical properties of pellets under conditions A of 30% and 40% iron concentrate.

[0113] The chemical composition, reduction expansion rate, and degree of reduction of pellets were determined under the conditions of 30% and 40% iron concentrate A ratio, with different proportions of low-sulfur Mongolian concentrate and silica added. The results are shown in Tables 13-16.

[0114] 1. Analysis of chemical composition and metallurgical properties of pellets under the condition of 30% iron concentrate A ratio

[0115] (1) Chemical composition and metallurgical properties of low-sulfur Mongolian concentrate pellets

[0116] Table 14 Chemical composition and metallurgical properties of low-sulfur Mongolian concentrate pellets (%)

[0117]

[0118]

[0119] Analysis of Table 14 above shows that as the proportion of low-sulfur Mongolian concentrate in the pellets increases, the TFe content in the pellets increases, the SiO2 content decreases, and both the reduction expansion rate and the degree of reduction increase. When the proportion of low-sulfur Mongolian concentrate reaches 20%, the reduction expansion rate of the pellets reaches 20.0%, and the degree of reduction is 42.1%, which basically meets the requirements of blast furnace smelting production. When the proportion of low-sulfur Mongolian concentrate is greater than 20%, the reduction expansion rate is >20%, which does not meet the requirements of blast furnace smelting production. This indicates that under the condition of 30% iron concentrate A proportion, the proportion of low-sulfur Mongolian concentrate should not exceed 20%.

[0120] Under the condition of 30% iron concentrate A, different proportions of low-sulfur Mongolian concentrate were added. With the increase of the proportion of low-sulfur Mongolian concentrate, the TFe in the pellet increased, the reduction expansion rate of the pellet increased, and the degree of reduction increased.

[0121] (2) Chemical composition and metallurgical properties of added silica pellets

[0122] Table 15 Chemical composition and metallurgical properties of the silica pellets (%)

[0123]

[0124] According to the analysis in Table 15 above, under the conditions of low sulfur Mongolian concentrate ratios of 30%, 40%, and 50%, adding 1.0%-2.0% silica content can effectively reduce the pellet reduction expansion rate.

[0125] 2. Analysis of chemical composition and metallurgical properties of pellets under the condition of 40% iron concentrate A ratio

[0126] (1) Analysis of chemical composition and metallurgical properties of pellets made with low-sulfur Mongolian concentrate

[0127] Table 16 Chemical composition and metallurgical properties of low-sulfur Mongolian concentrate pellets (%)

[0128]

[0129]

[0130] As shown in Table 16 above, with the increase of the proportion of low-sulfur Mongolian concentrate in the pellets, the TFe content of the pellets increases, the SiO2 content decreases, the reduction expansion rate of the pellets increases, and the overall reduction degree does not change much. When the proportion of low-sulfur Mongolian concentrate reaches 10%, the reduction expansion rate is 28.0%, which does not meet the requirements of blast furnace smelting production. This indicates that under the condition of 40% iron concentrate A ratio, when the proportion of low-sulfur Mongolian concentrate reaches 10%, it will lead to a reduction expansion rate of the pellets >20%, which does not meet the requirements of blast furnace smelting production.

[0131] Under the condition of 40% iron concentrate A, different proportions of low-sulfur Mongolian concentrate were added. With the increase of the proportion of low-sulfur Mongolian concentrate, the TFe in the pellet increased, the reduction expansion rate of the pellet increased, and the degree of reduction increased.

[0132] (2) Analysis of chemical composition and metallurgical properties of the added silica pellets

[0133] Table 17 Chemical composition and metallurgical properties of the silica pellets added, %

[0134]

[0135] According to the analysis in Table 17 above, under the conditions of adding 10%, 20%, 30%, 40%, and 50% of low-sulfur Mongolian concentrate, adding 1.3%-3.5% of silica can effectively reduce the pellet reduction expansion rate.

[0136] Experimental Example 4: Study on the mineral composition of pellets under conditions A of 30% and 40% iron concentrate.

[0137] 1. Mineral composition analysis of pellets under the condition of 30% iron concentrate A ratio

[0138] (1) Mineral composition analysis of pellets containing low-sulfur Mongolian concentrate

[0139] As the proportion of low-sulfur Mongolian concentrate increases to 40%, the pellets in this series have similar structures, with loose edges and denser centers. The metallic iron content at the edges gradually increases. When the proportion of low-sulfur Mongolian concentrate increases from 40% to 50%, the grains become finer and more dispersed, and the interlocking weakens.

[0140] Photographs of the mineral composition and structure of the reduced pellets with a 1-1 ratio are shown below. Figure 1 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. The edge of the pellet is metallic iron, the pellet as a whole is reduced, there is no black core structure in the center of the pellet, and the center is mainly composed of Fuji body.

[0141] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 1-2 are shown below. Figure 2 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. There is metallic iron at the edge of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0142] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 1-3 are shown below. Figure 3 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. There is metallic iron at the edge of the pellet, the pellet as a whole is reduced, and the center is mainly composed of Fuji body.

[0143] Images of the mineral composition and structure of the reduced pellets with ratios of 1-4 are shown below. Figure 4 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. There is metallic iron at the edge of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0144] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 1-5 are shown below. Figure 5 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. There is metallic iron at the edge of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0145] Images of the mineral composition and structure of the reduced pellets with ratios of 1-6 are shown below. Figure 6 As shown, it is mainly composed of metallic iron, fusiform and fir olivine. Metallic iron is present from the edge to the center of the pellet. The entire pellet is reduced, but the reduced grains are fragmented and dispersed.

[0146] (2) Mineral composition analysis of added silica pellets

[0147] Photographs of the mineral composition and structure of the reduced pellets with ratio 1A are shown below. Figure 7 As shown, it is mainly composed of metallic iron, fuji body and a small amount of fir olivine. Metallic iron is present from the edge to the center of the pellet. The pellet as a whole is reduced, and the center of the pellet still retains part of the pellet structure. The edge and center of the pellet structure are relatively dense.

[0148] Photographs of the mineral composition and structure of the pellets after reduction with a 1B ratio are shown below. Figure 8 As shown, it is mainly composed of metallic iron, fuji body, a small amount of fir olivine and a small amount of gangue. Metallic iron is only present at the edge of the pellet, and the pellet structure is relatively uniform and dense.

[0149] The above analysis shows that under the condition of 30% iron concentrate A, the mineral phase structure after reduction indicates that the pellets with 1.0% silica contain metallic iron in the center, while the pellets with 1.2% silica do not. The increase in silica ratio leads to an increase in the amount of liquid phase and gangue content in the pellets, which in turn prevents the center of the pellets from being fully oxidized, thus reducing the pellet expansion rate.

[0150] Photographs of the mineral composition and structure of the pellets after reduction with a 1C ratio are shown below. Figure 9As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. There is metallic iron at the edge of the pellet. The edge of the pellet structure is relatively dense, while the center is relatively loose.

[0151] Photographs of the mineral composition and structure of the pellets after reduction with a 1D ratio are shown below. Figure 10 As shown, it is mainly composed of metallic iron, fuji body and a small amount of fir peridot. Metallic iron is present from the edge to the center of the pellet, and the content of metallic iron decreases from the edge to the center. The pellet structure is relatively uniform and not dense.

[0152] Photographs of the mineral composition and structure of the reduced pellets with a 1E ratio are shown below. Figure 11 As shown, it is mainly composed of metallic iron, fuji body and a small amount of fir peridot. There is metallic iron at the edge of the pellet. The pellet structure is relatively dense at the edge and relatively loose in the center.

[0153] The above analysis shows that, under the condition of 30% iron concentrate A, the mineral composition and microstructure after reduction indicate that the mineral composition of pellets with 1.8% silica contains metallic iron, while that with 2.0% silica does not. Furthermore, the edge structure of pellets with 2.0% silica is denser than that with 1.8% silica. The increase in silica content leads to an increase in the liquid phase and gangue content of the pellets, resulting in tighter grain connections at the edge of the pellets and insufficient oxidation of the pellet center, thus reducing the reduction expansion rate of the pellets.

[0154] 2. Mineral composition analysis of pellets under the condition of 40% iron concentrate A ratio

[0155] (1) Mineral composition analysis of pellets containing low-sulfur Mongolian concentrate

[0156] As the proportion of low-sulfur Mongolian concentrate increases in this series of pellets, the content of metallic iron at the edges gradually increases, and the grains gradually separate. When the low-sulfur Mongolian concentrate increases to 40%, there are still connected crystals in the center of the pellets. When it increases from 40% to 50%, the grains are dispersed and there are no connected crystals between the grains.

[0157] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 2-1 are shown below. Figure 12 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. There is metallic iron at the edge of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0158] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 2-2 are shown below. Figure 13 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. Metallic iron is present from the edge to the center of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0159] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 2-3 are shown below. Figure 14As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. Metallic iron is present from the edge to the center of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0160] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 2-4 are shown below. Figure 15 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. Metallic iron is present from the edge to the center of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0161] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 2-5 are shown below. Figure 16 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. Metallic iron is present from the edge to the center of the pellet. The pellet as a whole is reduced. There is no black core structure in the center of the pellet. The center is mainly composed of Fuji body.

[0162] Photographs of the mineral composition and structure of the reduced pellets with a ratio of 2-6 are shown below. Figure 17 As shown, it is mainly composed of metallic iron, fusiform and fir olivine. Metallic iron is present from the edge to the center of the pellet. The entire pellet is reduced, but the reduced grains are fine and fragmented, with no crystal bridges connecting the grains, and the liquid phase content is low.

[0163] (2) Mineral composition analysis of added silica pellets

[0164] Photographs of the mineral composition and structure of the reduced pellets with ratio 2A are shown below. Figure 18 As shown, it is mainly composed of metallic iron, fuji body and a small amount of fir olivine. There is metallic iron from the edge to the center of the pellet. The pellet is completely reduced, and large pores appear in the center of the pellet. The edge of the pellet structure is relatively dense.

[0165] Photographs of the mineral composition and structure of the pellets after reduction with a 2B ratio are shown below. Figure 19 As shown, it is mainly composed of metallic iron, fuji body and a small amount of fir olivine. Metallic iron is present from the edge to the center of the pellet. The pellet as a whole is reduced, and large arc-shaped pores appear locally. The pellet structure is relatively dense at both the edge and the center.

[0166] Photographs of the mineral composition and structure of the pellets after reduction with a 2C ratio are shown below. Figure 20 As shown, it is mainly composed of metallic iron, fuji body and a small amount of fir olivine. Metallic iron is only present at the edge of the pellet. The pellet structure is relatively dense at the edge and relatively loose in the center.

[0167] Photographs of the mineral composition and structure of the reduced pellets after 2D mixing are shown below. Figure 21 As shown, it is mainly composed of metallic iron, Fuji body and a small amount of fir peridot. Metallic iron is only present at the edge of the pellet, and a "black heart" appears in the center of the pellet. Large air pores and arc-shaped air pores appear in some parts of the pellet, and the edge of the pellet is relatively dense.

[0168] Photographs of the mineral composition and structure of the reduced pellets with a 2E ratio are shown below. Figure 22 As shown, it is mainly composed of metallic iron, fuji body, a small amount of fir olivine and a small amount of gangue. Metallic iron is present from the edge to the center of the pellet. The pellet structure is relatively dense at the edge and relatively loose in the center.

[0169] Experimental Example 5: Determination of a suitable roasting regime for adding low-sulfur Mongolian concentrate and silica pellets

[0170] Based on the current belt pelletizing process roasting regime, the reasonable roasting temperature of pellets with added low-sulfur Mongolian concentrate and silica was studied in the laboratory to determine its reasonable roasting process parameters.

[0171] 1. Study on pellet roasting regime under 30% iron concentrate A ratio

[0172] (1) Study on roasting regime of pellets with added low-sulfur Mongolian concentrate

[0173] Table 18. Roasting performance of pellets with added low-sulfur Mongolian concentrate, N / P

[0174]

[0175] Analysis of Table 18 above shows that: ① Under the same low-sulfur Mongolian concentrate ratio, the strength of the finished pellets tends to increase with the increase of roasting temperature; at the same roasting temperature, the strength of the finished pellets generally tends to decrease with the increase of the low-sulfur Mongolian concentrate ratio, and the decrease in strength of the finished pellets varies with different roasting temperatures; ② When adding 10%-50% of low-sulfur Mongolian concentrate at a roasting temperature of 1190℃, the strength of the finished pellets is greater than 2300 N / P, which meets the requirements of blast furnace production and smelting.

[0176] Therefore, under the condition of 30% iron concentrate A ratio, adding 10%-50% low-sulfur Mongolian concentrate, the suitable roasting temperature is 1190℃. Considering the requirements of energy conservation and consumption reduction, the roasting temperature can be set at 1170℃.

[0177] (2) Study on the roasting regime of silica pellets

[0178] Table 19. Calcination performance of silica pellets, N / P

[0179]

[0180]

[0181] Analysis of Table 19 above shows that: ① Under the same low-sulfur Mongolian concentrate ratio, the strength of the finished pellets tends to increase with the increase of roasting temperature; ② When adding 30%, 40%, and 50% low-sulfur Mongolian concentrate, the strength of the finished pellets with the addition of 1.0%-2.0% silica is greater than 2300 N / P at 1170℃, which meets the requirements of blast furnace smelting production, and the suitable roasting temperature is 1170℃.

[0182] Therefore, under the condition of 30% iron concentrate A, the suitable roasting temperature is 1170℃ when 30%, 40%, and 50% of low-sulfur Mongolian concentrate and 1.0%-2.0% of silica are added.

[0183] 2. Study on pellet roasting regime under 40% iron concentrate A ratio

[0184] (1) Roasting performance of pellets with added low-sulfur Mongolian concentrate

[0185] Table 20. Roasting performance of pellets with added low-sulfur Mongolian concentrate, N / P

[0186]

[0187] Analysis of Table 20 above shows that: ① When the same proportion of low-sulfur Mongolian concentrate is added, the strength of the finished pellets increases with the increase of roasting temperature; under the same roasting temperature, the compressive strength of the finished pellets does not change much with the increase of the proportion of low-sulfur Mongolian concentrate; ② When 10%-50% of low-sulfur Mongolian concentrate is added, the strength of the finished pellets is greater than 2300 N / P when the roasting temperature is 1170℃, which meets the requirements of blast furnace production and smelting.

[0188] (2) Calcination performance of silica pellets

[0189] Table 21. Calcination performance of silica pellets with added silica, N / P

[0190]

[0191] As shown in Table 21 above, when the same proportion of low-sulfur Mongolian concentrate is added, the addition of 1.3%-3.5% silica increases the strength of the finished pellets with the increase of roasting temperature. The strength of the finished pellets is greater than 2300 N / P at 1170℃, which meets the requirements of blast furnace smelting production.

[0192] The foregoing has provided a detailed description of the pellet production method using low-sulfur Mongolian concentrate and the preparation method thereof. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the invention.

Claims

1. A type of pellet produced from low-sulfur Mongolian concentrate, characterized in that: The pellets contain 62.5%–65.5% TFe, 3.0%–6.0% SiO2, and have a reduction expansion rate of less than 20%.

2. The pelletized ore according to claim 1, characterized in that: The pellets are prepared from the following raw materials in parts by weight: 40-50 parts iron concentrate, 10-50 parts low-sulfur Mongolian concentrate, 10-60 parts high-silicon iron concentrate, 1-3 parts bentonite, and 1-5 parts silica. Among them, the low-sulfur Mongolian concentrate contains more than 32% FeO and less than 0.8% S.

3. The pelletized ore according to claim 1, characterized in that: The pellets are prepared from raw materials comprising the following parts by weight: 40-50 parts iron concentrate, 30-50 parts low-sulfur Mongolian concentrate, and 10-30 parts high-silicon iron concentrate.

4. The pelletized ore according to claim 3, characterized in that: The iron concentrate includes iron concentrate A and iron concentrate B, wherein the sulfur content in iron concentrate A is 0.5-0.6% and the sulfur content in iron concentrate B is 0.1-0.2%.

5. The pelletized ore according to claim 4, characterized in that: The pellet also includes the following raw materials by weight: 30-40 parts of iron concentrate A and 10 parts of iron concentrate B.

6. The method for preparing pellets according to claim 1, characterized in that: The method includes the following steps: 1) Mix the following raw materials in parts by weight: 40-50 parts iron concentrate, 10-50 parts low-sulfur Mongolian concentrate, 10-60 parts high-silicon iron concentrate, 1-3 parts bentonite and 1-5 parts silica evenly, and make green pellets on a pelletizing plate. 2) Raw pellets are dried, preheated and roasted to obtain pellet ore.

7. The preparation method according to claim 6, characterized in that: In step 1), green balls are made on a φ1000mm surface. The green ball control parameters are: mother ball generation time is 2-4 min, green ball growth time is 5-10 min, and green ball compaction time is 8-12 min.

8. The preparation method according to claim 6, characterized in that: In step 1), green balls are made on a φ1000mm surface. The green ball control parameters are: mother ball generation time is 3min, green ball growth time is 8min, and green ball compaction time is 10min.

9. The preparation method according to claim 6, characterized in that: In step 2), the roasting temperature is 1150℃~1210℃.

10. The preparation method according to claim 6, characterized in that: In step 2), the roasting temperature is 1170℃.

Images