Production method for preparing all-hematite limonite oxidized pellets through preheating section zoning and hydrogen enrichment

Abstract

The invention discloses a production method for preparing all hematite and limonite oxidized pellets in a pre-heating section partition hydrogen-rich mode. The production method comprises the following steps that hematite and limonite are subjected to dry grinding or wet type ore grinding, filter pressing and dewatering, and then hematite and limonite fine powder is obtained; the hematite and limonite fine powder and bentonite are subjected to strong mixing, high-pressure roller milling, pelletizing and roller screen grading, and green pellets are obtained; the green pellets enter a belt type roasting machine to be subjected to forced air drying and then enter a preheating section after being subjected to air draft drying; green pellets enter a preheating section first area, the ratio of coke oven gas to combustion air is adjusted, and the coke oven gas is excessive; green pellets enter a second preheating section area, the ratio of coke oven gas to combustion air is adjusted, and the combustion air is excessive; and the subsequent green pellets enter the roasting section and then enter the first cooling section and the second cooling section, and finally the all-hematite limonite oxidized pellets meeting the blast furnace smelting requirement are obtained. The method has the advantages that the roasting temperature of the whole hematite and limonite is reduced, the quality index of the oxidized pellets prepared from the whole hematite and limonite is improved, and the process energy consumption and carbon emission of preparing the oxidized pellets from the whole-proportion hematite and limonite are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of pellet production, and in particular to a production method for preparing all-hematite oxidized pellets by hydrogen enrichment in a preheating section. Background Art

[0002] Oxidized pellets are a high-quality blast furnace ironmaking material with high iron grade, good strength and excellent reduction performance. The combination of acidic pellets and high-alkalinity sintered ore can increase blast furnace production and save coke, and reduce the production cost of steel enterprises. With the increasing requirements of modern blast furnaces for ironmaking raw materials, and the energy consumption of the pelletizing process is only 1 / 2 to 1 / 3 of that of sintering, under the background of dual carbon, pellets have become an important process path for long-process carbon reduction, so the role of pellets has become more and more important. The existing pellet production process mainly includes vertical furnaces, rotary kilns and belt roasters. With the development of belt roasters, it provides a great idea for expanding the raw material structure of pellets, which can increase the application ratio of hematite in pellets, but full-proportion hematite is rarely used in China. The existing full-hematite production technology mainly focuses on the zoned oxygen control after the pellets are carbonized to achieve a local reducing atmosphere and strengthen the reduction of hematite; in addition, there is graded carbonization of pellets to achieve graded heat supplement and reduction. All of the above technologies require carbon addition to pellets. Under the current dual-carbon background, it is worth exploring in depth how to reduce carbon consumption and achieve full-proportion hematite production pellets. Summary of the invention

[0003] The purpose of the present invention is to provide a production method for preparing oxidized pellets of whole hematite by hydrogen enrichment in a preheating section, reduce the roasting temperature of whole hematite, improve the quality index of oxidized pellets prepared from whole hematite, and reduce the energy consumption and carbon emission of the process of preparing oxidized pellets from full-proportion hematite.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions:

[0005] A production method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section, characterized by comprising the following steps:

[0006] The hematite concentrate is obtained by dry grinding or wet grinding, filtration and dehydration of the hematite;

[0007] The hematite concentrate and bentonite are mixed vigorously, and then subjected to high pressure roller grinding to form balls, and then classified by roller sieve to obtain green balls;

[0008] The green balls enter the belt roasting machine and are dried by blast and exhaust air before entering the preheating section;

[0009] The green balls enter the first zone of the preheating section, and the ratio of coke oven gas to combustion air is adjusted in the first zone of the preheating section, so that the coke oven gas is in excess;

[0010] The green balls enter the second zone of the preheating section, and the ratio of coke oven gas to combustion air is adjusted in the second zone of the preheating section, so that the combustion air is in excess;

[0011] The subsequent green balls enter the roasting stage and then the cooling stage one and two, and finally obtain the full hematite oxide pellets that meet the requirements of blast furnace smelting.

[0012] Preferably, the particle size composition of the hematite concentrate is required to be more than 85% of -200 mesh.

[0013] Preferably, the ratio of the hematite concentrate to the bentonite in the bentonite is less than or equal to 0.4%.

[0014] Preferably, the particle size of the green balls is 8-12 mm accounting for more than 90%.

[0015] Preferably, the temperature of the forced air drying section is 200-280°C, and the temperature of the exhausted air drying section is 300-360°C.

[0016] Preferably, two groups of long wind boxes are arranged in front and behind the preheating section, which are arranged as preheating section zone 1 and preheating section zone 2 respectively by exhaust method. A coke oven gas combustion system is arranged on both sides of the preheating section zone 1 and preheating section zone 2, totaling 4 sets.

[0017] Preferably, the ratio of the coke oven gas to the combustion air flow in the first zone of the preheating section is 1:3, the combustion air in the first zone of the preheating section is non-compressed air at room temperature, and the oxygen concentration is 21%, and the coke oven gas flow on both sides of the first zone of the preheating section is 900-1000m 3 / h, adjust the temperature of the first zone of the preheating section to 800-850℃.

[0018] Preferably, the ratio of the coke oven gas to the combustion air flow in the second zone of the preheating section is 1:20, the combustion air in the second zone of the preheating section is the circulating hot air of 200-300°C in the cooling section, the oxygen concentration is 21%, and the coke oven gas flow on both sides of the second zone of the preheating section is 600-700m 3 / h, adjust the temperature of the second zone of the preheating section to 950-1000℃.

[0019] Preferably, the temperature in the roasting section is 1220-1260°C, the temperature in the first cooling section is 700-900°C, and the temperature in the second cooling section is 200-700°C.

[0020] Preferably, the full hematite oxidized pellets meeting the requirements of blast furnace smelting have a compressive strength greater than 2500N / P, a reduction expansion less than 15%, and a reducibility greater than 65%.

[0021] In summary, the beneficial effects of the present invention are as follows: the present invention is based on a production method for preparing oxidized hematite pellets by zoning hydrogen enrichment in the preheating section of a belt roaster. After the raw balls are dried by blast drying and exhaust drying in the belt roaster, zoning control is implemented in the preheating section, the preheating temperature of the first zone of the preheating section is controlled, the ratio of coke oven gas to combustion-supporting air is adjusted, and excess coke oven gas is achieved in the first zone of the preheating section, and H2-containing gas is provided as a reducing agent to participate in the reduction of hematite, the preheating temperature of the second zone of the preheating section is controlled, and the ratio of coke oven gas to combustion-supporting air is adjusted to achieve excess oxygen in the second zone of the preheating section to form an oxidizing atmosphere, and the magnetite reduced from hematite in the first zone of the preheating section is reoxidized to release heat to form regenerated hematite crystals. The oxidation heat release can reduce the temperature required for the pellets to form regenerated hematite crystals, thereby reducing the roasting temperature of the whole hematite, improving the quality indicators of oxidized pellets prepared from the whole hematite, and reducing the energy consumption and carbon emissions of the process for preparing oxidized pellets from the full proportion of hematite. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flow chart of a production method for preparing whole hematite oxide pellets by hydrogen enrichment in a preheating section. DETAILED DESCRIPTION

[0023] The specific implementation manner of the present invention is further described below in conjunction with the accompanying drawings, and this embodiment does not constitute a limitation of the present invention.

[0024] like Figure 1 As shown, a production method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section comprises the following steps:

[0025] The hematite concentrate is obtained by dry grinding or wet grinding, filtration and dehydration of the hematite;

[0026] The hematite concentrate and bentonite are mixed vigorously, and then subjected to high pressure roller grinding to form balls, and then classified by roller sieve to obtain green balls;

[0027] The green balls enter the belt roasting machine and are dried by blast and exhaust air before entering the preheating section;

[0028] The green balls enter the first zone of the preheating section, and the ratio of coke oven gas to combustion air is adjusted in the first zone of the preheating section, so that the coke oven gas is in excess;

[0029] The green balls enter the second zone of the preheating section, and the ratio of coke oven gas to combustion air is adjusted in the second zone of the preheating section, so that the combustion air is in excess;

[0030] The subsequent green balls enter the roasting stage and then the cooling stage one and two, and finally obtain the full hematite oxide pellets that meet the requirements of blast furnace smelting.

[0031] The particle size composition of hematite concentrate requires that -200 mesh accounts for more than 85%.

[0032] The proportion of the hematite concentrate to the bentonite is less than or equal to 0.4%.

[0033] The particle size of the raw balls is 8-12mm, accounting for more than 90%.

[0034] The temperature of the forced air drying section is 200-280℃, and the temperature of the exhaust air drying section is 300-360℃.

[0035] Two groups of long bellows are arranged in front and behind the preheating section, which adopt exhaust method and are arranged as preheating section zone 1 and preheating section zone 2 respectively. A coke oven gas combustion system is arranged on both sides of preheating section zone 1 and preheating section zone 2, totaling 4 sets.

[0036] The ratio of coke oven gas to combustion air in the first zone of the preheating section is 1:3. The combustion air in the first zone of the preheating section is non-compressed air at room temperature with an oxygen concentration of 21%. The coke oven gas flow rates on both sides of the first zone of the preheating section are 900-1000m 3 / h, adjust the temperature of the first zone of the preheating section to 800-850℃.

[0037] The ratio of coke oven gas to combustion air in the second zone of the preheating section is 1:20. The combustion air in the second zone of the preheating section is the circulating hot air of 200-300℃ in the cooling section, with an oxygen concentration of 21%. The coke oven gas flow on both sides of the second zone of the preheating section is 600-700m 3 / h, adjust the temperature of the second zone of the preheating section to 950-1000℃.

[0038] The temperature in the roasting section is 1220-1260°C, the temperature in the first cooling section is 700-900°C, and the temperature in the second cooling section is 200-700°C.

[0039] The full hematite oxide pellets that meet the requirements of blast furnace smelting have a compressive strength greater than 2500N / P, a reduction expansion less than 15%, and a reducibility greater than 65%.

[0040] Embodiment 1:

[0041] After the hematite concentrate and bentonite are mixed in the proportions shown in Table 1, the pelletizing is carried out to prepare green balls with a particle size range of 8-12 mm and a ratio of 90%; the requirements for the green balls entering the belt roaster are as follows: the temperature control range of the blast drying section is 200-280°C, the exhaust drying section is 300-360°C, and the combustion system on both sides of the first zone of the preheating section is set to have a coke oven gas flow rate: combustion air flow rate = 1:3, which are 1000m 3 / h、3000m 3 / h, the temperature of the first zone of the preheating section is controlled at 830℃; the combustion system on both sides of the second zone of the preheating section is set to a coke oven gas flow rate of 700m 3 / h, the combustion air adopts circulating hot air in the cooling stage, the temperature of the second zone of the preheating stage is 980℃; the roasting temperature is 1240℃; after roasting, it enters the cooling stage and the second stage, the temperature of the cooling stage is controlled at 700-900℃, and the temperature of the cooling stage is controlled at 200-700℃, and the compressive strength is above 2506N / P, the reduction expansion is 13.9%, and the reducibility is 67.7%, which meets the requirements of blast furnace smelting.

[0042] Table 1 Material ratios in Example 1

[0043] materials Ratio TFe C Feo <![CDATA[SiO2]]> CaO MgO <![CDATA[Al2O3]]> Ig <![CDATA[H2O]]> Limonite concentrate 99.6％ 61.99 0.31 6.03 0.05 0.20 1.75 5.64 8.12 Bentonite 0.4％ 62 2.8 3.2 14

[0044] Embodiment 2:

[0045] After the hematite concentrate and bentonite are mixed in the proportions shown in Table 2, the pelletizing is carried out to prepare green balls with a particle size range of 8-12 mm and a ratio of 90%; the requirements for the green balls entering the belt roaster are: the temperature control range of the blast drying section is 200-280°C, the exhaust drying section is 300-360°C, and the combustion system on both sides of the first zone of the preheating section is set to have a coke oven gas flow rate: combustion air flow rate = 1:3, which are 950m 3 / h、2850m 3 / h, the temperature of the first zone of the preheating section is controlled at 820℃; the combustion system on both sides of the second zone of the preheating section is set to have a coke oven gas flow rate of 600m 3 / h, the combustion air adopts circulating hot air in the cooling stage, the temperature of the second zone of the preheating stage is 980℃; the roasting temperature is 1250℃; after roasting, it enters the cooling stage and the second stage, the temperature of the cooling stage is controlled at 700-900℃, and the temperature of the cooling stage is controlled at 200-700℃, and the compressive strength is above 2588N / P, the reduction expansion is 14.1%, and the reducibility is 70.7%, which meets the requirements of blast furnace smelting.

[0046] Table 2 Ratio of materials in Example 2

[0047] materials Ratio TFe C Feo <![CDATA[SiO2]]> CaO MgO <![CDATA[Al2O3]]> Ig <![CDATA[H2O]]> Limonite concentrate 99.6％ 61.99 0.31 6.03 0.05 0.20 1.75 5.64 8.12 Bentonite 0.4％ 62 2.8 3.2 14

[0048] Embodiment 3:

[0049] After the hematite concentrate and bentonite are mixed in the proportions shown in Table 3, the pelletizing is carried out to prepare green balls with a particle size range of 8-12 mm and a ratio of 90%; the requirements for the green balls entering the belt roaster are: the temperature control range of the blast drying section is 200-280°C, the exhaust drying section is 300-360°C, and the combustion system on both sides of the first zone of the preheating section is set to have a coke oven gas flow rate: combustion air flow rate = 1:4, which are 950m 3 / h、3800m 3 / h, the temperature of the first zone of the preheating section is controlled at 790℃; the combustion system on both sides of the second zone of the preheating section is set to have a coke oven gas flow rate of 600m 3 / h, the combustion air adopts circulating hot air in the cooling stage, the temperature of the second zone of the preheating stage is 980℃; the roasting temperature is 1260℃; after roasting, it enters the cooling stage and the second stage, the temperature of the cooling stage is controlled at 700-900℃, and the temperature of the cooling stage is controlled at 200-700℃, and the compressive strength is above 2435N / P, the reduction expansion is 13.6%, and the reducibility is 68.5%, and the compressive strength is low.

[0050] Table 3 Material ratios in Example 3

[0051] materials Ratio TFe C Feo <![CDATA[SiO2]]> CaO MgO <![CDATA[Al2O3]]> Ig <![CDATA[H2O]]> Limonite concentrate 99.6％ 61.99 0.31 6.03 0.05 0.20 1.75 5.64 8.12 Bentonite 0.4％ 62 2.8 3.2 14

[0052] Embodiment 4:

[0053] After the hematite concentrate and bentonite are mixed in the proportions shown in Table 4, the pelletizing is carried out to prepare green balls with a particle size range of 8-12 mm and a proportion of 90%; the requirements for the green balls entering the belt roaster are as follows: the temperature control range of the blast drying section is 200-280°C, the exhaust drying section is 300-360°C, and the combustion system on both sides of the first zone of the preheating section is set to have a coke oven gas flow rate: combustion air flow rate = 1:3, which are 900m 3 / h、27800m 3 / h, the temperature of the first zone of the preheating section is controlled at 790℃; the combustion system on both sides of the second zone of the preheating section is set to have a coke oven gas flow rate of 600m 3 / h, the combustion air adopts circulating hot air in the cooling stage, the temperature of the second zone of the preheating stage is 980℃; the roasting temperature is 1220℃; after roasting, it enters the cooling stage and the second stage, the temperature of the cooling stage is controlled at 700-900℃, and the temperature of the cooling stage is controlled at 200-700℃, and the compressive strength is above 2622N / P, the reduction expansion is 14.6%, and the reducibility is 68.9%, which meets the requirements of blast furnace smelting.

[0054] Table 4 Material ratios in Example 4

[0055] materials Ratio TFe C Feo <![CDATA[SiO2]]> CaO MgO <![CDATA[Al2O3]]> Ig <![CDATA[H2O]]> Limonite concentrate 99.8％ 61.99 0.31 6.03 0.05 0.20 1.75 5.64 8.12 Bentonite 0.2％ 62 2.8 3.2 14

[0056] Comparative Example 1:

[0057] After the hematite concentrate and bentonite are mixed in the proportions shown in Table 5, the pelletizing is carried out to prepare green balls with a particle size range of 8-12 mm and a proportion of 90%; the requirements for the green balls entering the belt roaster are: the temperature control range of the blast drying section is 200-280°C, the exhaust drying section is 300-360°C, the combustion system on both sides of the preheating section zone 1 and the preheating section zone 2 is set to a coke oven gas flow rate of 700m 3 / h, the combustion air adopts circulating hot air in the cooling stage, the temperature of the second zone of the preheating stage is 980℃; the roasting temperature is 1290℃; after roasting, it enters the cooling stage and the second stage, the temperature of the cooling stage is controlled at 700-900℃, and the temperature of the cooling stage is controlled at 200-700℃, and the compressive strength is above 2202N / P, the reduction expansion is 16.6%, and the reducibility is 72.1%. The compressive strength and reduction expansion do not meet the requirements of blast furnace smelting.

[0058] Table 5 Ratio of materials in comparative example 1

[0059] materials Ratio TFe C Feo <![CDATA[SiO2]]> CaO MgO <![CDATA[Al2O3]]> Ig <![CDATA[H2O]]> Limonite concentrate 99.8％ 61.99 0.31 6.03 0.05 0.20 1.75 5.64 8.12 Bentonite 0.2％ 62 2.8 3.2 14

[0060] The present invention is based on a production method for preparing oxidized hematite pellets by zoning hydrogen enrichment in a preheating section of a belt roaster. After the green balls are dried by blast drying and exhaust drying in the belt roaster, zoning control is implemented in the preheating section, the preheating temperature of the first zone of the preheating section is controlled, the ratio of coke oven gas to combustion-supporting air is adjusted to achieve excess coke oven gas in the first zone of the preheating section, H2-containing gas is provided as a reducing agent to participate in the reduction of the hematite, the preheating temperature of the second zone of the preheating section is controlled, the ratio of coke oven gas to combustion-supporting air is adjusted to achieve excess oxygen in the second zone of the preheating section to form an oxidizing atmosphere, and magnetite reduced from hematite in the first zone of the preheating section is reoxidized to release heat to form regenerated hematite crystals. The oxidation heat release can reduce the temperature required for the pellets to form regenerated hematite crystals, thereby reducing the roasting temperature of the whole hematite, improving the quality index of the oxidized pellets prepared from the whole hematite, and reducing the energy consumption and carbon emission of the process for preparing oxidized pellets from the full-proportion hematite.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be deemed to fall within the protection scope of the technical solution of the present invention.

Claims

1. A production method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section, characterized in that: The steps include: The hematite concentrate is obtained by dry grinding or wet grinding, filtration and dehydration of the hematite; The hematite concentrate and bentonite are mixed vigorously, and then subjected to high pressure roller grinding to form balls, and then classified by roller sieve to obtain green balls; The green balls enter the belt roasting machine and are dried by blast and exhaust air before entering the preheating section; The green balls enter the first zone of the preheating section, and the ratio of coke oven gas to combustion air is adjusted in the first zone of the preheating section, so that the coke oven gas is in excess; The green balls enter the second zone of the preheating section, and the ratio of coke oven gas to combustion air is adjusted in the second zone of the preheating section, so that the combustion air is in excess; The subsequent green balls enter the roasting stage and then the cooling stage one and two, and finally obtain the full hematite oxide pellets that meet the requirements of blast furnace smelting.

2. The method for preparing whole hematite oxidized pellets by hydrogen enrichment in preheating section according to claim 1, characterized in that: The particle size composition of the hematite concentrate is required to be more than 85% of -200 mesh.

3. The method for preparing whole hematite oxidized pellets by hydrogen enrichment in preheating section according to claim 1, characterized in that: The ratio of the hematite concentrate to the bentonite in the bentonite is less than or equal to 0.4%.

4. The method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section according to claim 1, characterized in that: The particle size of the raw balls is 8-12 mm, accounting for more than 90%.

5. The method for preparing whole hematite oxidized pellets by hydrogen enrichment in preheating section according to claim 1, characterized in that: The temperature of the blast drying section is 200-280°C, and the temperature of the exhaust drying section is 300-360°C.

6. The method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section according to claim 1, characterized in that: Two groups of long wind boxes are arranged in the front and back of the preheating section, which adopt exhaust mode and are arranged as preheating section zone 1 and preheating section zone 2 respectively. A coke oven gas combustion system is arranged on both sides of the preheating section zone 1 and preheating section zone 2, totaling 4 sets.

7. The method for preparing whole hematite oxidized pellets by hydrogen enrichment in preheating section according to claim 6, characterized in that: The ratio of the coke oven gas to combustion air flow in the first zone of the preheating section is 1:

3. The combustion air in the first zone of the preheating section is non-compressed air at room temperature with an oxygen concentration of 21%. The coke oven gas flow on both sides of the first zone of the preheating section is 900-1000m 3 / h, adjust the temperature of the first zone of the preheating section to 800-850℃.

8. The method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section according to claim 6, characterized in that: The ratio of the coke oven gas to combustion air flow in the second zone of the preheating section is 1:

20. The combustion air in the second zone of the preheating section is the circulating hot air of 200-300℃ in the cooling section, with an oxygen concentration of 21%. The coke oven gas flow on both sides of the second zone of the preheating section is 600-700m 3 / h, adjust the temperature of the second zone of the preheating section to 950-1000℃.

9. The method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section according to claim 1, characterized in that: The temperature in the roasting section is 1220-1260°C, the temperature in the first cooling section is 700-900°C, and the temperature in the second cooling section is 200-700°C.

10. The method for preparing whole hematite oxide pellets by hydrogen enrichment in preheating section according to claim 1, characterized in that: The full hematite oxidized pellets meeting the requirements of blast furnace smelting have a compressive strength greater than 2500N / P, a reduction expansion less than 15%, and a reducibility greater than 65%.

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