A fluxed pellet containing specularite and a preparation method thereof

Abstract

The object of the present invention is to solve the problems existing in the effective use of specularite in the production of pellet ore in the prior art, and to provide a fluxed pellet containing specularite and a preparation method thereof. A technical solution of a fluxed pellet containing specularite includes raw materials with the following mass percentages: specularite (calculated as dry ore) 80% - 100%, magnetite (calculated as dry ore) 20 - 0%, and additionally anthracite coal powder 7% - 12%, limestone powder 1.0% - 5.5%, and composite bentonite 1.5% - 2.5%; and the basicity range is 0.6 - 1.2. In the present invention, the proportion of specularite added is relatively large, and the addition of other raw materials will not reduce the iron grade of the pellet ore, thus reducing the cost of the pellet ore.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a technology for producing oxidized pellet ore using specularite. Background Art

[0002] In recent years, pellet ore has become an important burden for blast furnace ironmaking, and fluxed pellets have received increasing attention from iron and steel enterprises. The main raw material used for producing pellet ore is high-quality magnetite concentrate obtained from ore dressing, but the production cost of high-quality iron concentrate is relatively high. In order to reduce production costs and improve the performance indexes of pellet ore as much as possible, iron and steel enterprises have begun to explore adding specularite, which was previously considered not very suitable for pellet production, to iron concentrate. As an iron ore, specularite has the advantages of high iron grade, few harmful impurities, large existing reserves, and relatively low price. However, due to the intact crystal grain size, smooth particle surface, and dense structure of specularite, the hydrophilicity and pelletizing performance of specularite are relatively poor, and it is not easy to form pellets or the green pellet indexes are very poor during use. At the same time, due to the poor high-temperature reaction performance of specularite, it is difficult to form low-melting compounds and it is not easy to form recrystallization interconnection between particles, resulting in poor preheated pellet indexes and low strength of pellet ore. Due to the above disadvantages, specularite has not been widely used in the pellet industry at present.

[0003] In order to effectively utilize specularite resources, the prior art has studied the production of pellet ore using specularite.

[0004] For example, Zhang Daoyuan of Central South University mentioned that after pretreating specularite, when the specific surface area of specularite reaches 1600 cm 2 / g, using 1.0% of the special binder MHA for pelletizing, the green pellet indexes can basically meet the production requirements. Professor Zhu Deqing of Central South University mentioned that the strengthening measures for using specularite in pellet production mainly include using high-quality and efficient binders, producing fluxed pellets, adding fuel in batches, mechanical activation, etc. In on-site production, various strengthening measures can be comprehensively used to achieve the purpose of improving the pelletizing effect. However, the above researchers also all mentioned that the addition amount of specularite in pellet ore cannot exceed 20%. In order to increase the use ratio of specularite, Tang Yanyun of Central South University also studied the strengthening of Brazilian specularite pellets using the high-pressure roller grinding process and obtained that when specularite and magnetite are used in combination, through mechanical activation, the incorporation amount of specularite can reach 70%. The research also pointed out that the preheating temperature of the pellets after mechanical activation is still above 1000°C. He Aoping of Central South University solved the technical problem of preparing pellets using single Brazilian specularite by adding iron-containing miscellaneous materials and limestone mud cake to Brazilian specularite and performing wet grinding on the mixture. There are clear requirements for the properties of the raw materials in the research, and both the preheating time and the roasting time are 15 minutes.

[0005] Some patents also introduce methods for producing pellets from specularite. For example, the patent with the application number CN202010645043.0 discloses a method for producing oxidized pellets from specularite. The method involves pelletizing specularite with a specific surface area ≥ 1200 cm 2 / g, magnetite with a specific surface area ≥ 1400 cm 2 / g, sinter return fines with a -200 mesh content ≥ 85%, and composite bentonite according to the dry material weight ratio and then mixing and pelletizing. Under the conditions of a preheating temperature of 950 - 980 °C, a preheating time of 10 min, a roasting temperature of 1200 - 1250 °C, and a roasting time of 10 min, roasted pellets with a compressive strength ≥ 2300 N / pellet are obtained. Adding sinter return fines in pellet production, and the return fines are the products of the sintering plant and generally need to be returned to sintering production. Although adding return fines with a certain alkalinity can improve the formation of liquid phase in pellet ore and thus increase the strength of pellet ore, the process is relatively complex, and the sinter return fines will reduce the grade of pellet ore and the cost is relatively high. For example, the patent with the application number CN201610056164.5 discloses a roasting method for a high proportion of specularite, which introduces that the specific surface area of specularite reaches 2000 cm 2 / g after high-pressure roll milling and is used to produce pellets. The proportion of specularite incorporated can reach 60% - 75%, but the preheating temperature of the pellets is still relatively high, at 1100 - 1180 °C.

[0006] Therefore, a large amount of research work is still needed for the effective use of specularite in pellet production, especially in fluxed pellets. Summary of the Invention

[0007] The purpose of the present invention is to provide a fluxed pellet containing specularite and a preparation method to solve the problems existing in the effective use of specularite in pellet production in the prior art. In the present invention, the incorporation ratio of specularite is relatively large, and the addition of other raw materials will not reduce the iron grade of pellet ore, thus reducing the cost of pellet ore.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A fluxed pellet containing specularite of the present invention comprises raw materials with the following mass percentages: specularite (calculated as dry ore) 80% - 100%, magnetite (calculated as dry ore) 20 - 0%, and additionally anthracite powder 7% - 12%, limestone powder 1.0% - 5.5%, and composite bentonite 1.5% - 2.5%; and the alkalinity range is 0.6 - 1.2.

[0010] Further, for the above-mentioned fluxed pellet containing specularite, the specific surface area of specularite ≥ 1200 cm 2 / g; the particle size of anthracite coal fines with -200 mesh is ≥95%; the magnetite raw material is magnetite concentrate, and its specific surface area is ≥1500 cm 2 / g.

[0011] Furthermore, for the fluxed pellets containing specularite mentioned above, the mass percentage contents of each component in the composite bentonite are as follows: corn starch 30 - 50%, bamboo fiber 20 - 30%, and sodium-based bentonite 20 - 40%.

[0012] A preparation method of a fluxed pellet containing specularite according to the present invention comprises the following steps:

[0013] Step 1: Raw material preparation

[0014] Crush the specularite by extrusion with a high-pressure roller mill to make the specific surface area of the specularite ≥1200 cm 2 / g; grind the anthracite coal fines to a particle size with -200 mesh ≥95% by using a ball mill; take magnetite concentrate and crush it by extrusion with a high-pressure roller mill, and its specific surface area is ≥1500 cm 2 / g;

[0015] Step 2: Batching and pelletizing

[0016] Mix the specularite, magnetite, and anthracite coal fines obtained in Step 1 with limestone powder and composite bentonite in proportion, and control the basicity range of the mixed raw materials to be 0.6 - 1.2; mix the mixed raw materials evenly and then pelletize, control the total water content of the mixed raw materials to be 7.5 - 8.5% of the dry weight of the specularite and magnetite, and the mixed raw materials form green pellets, and then dry them for standby;

[0017] Step 3: Preheating and roasting

[0018] Preheat and roast the dry green pellets obtained in Step 2. Under the conditions of a preheating temperature of 950°C - 1000°C and a preheating time of 9 - 11 min, obtain preheated pellets; then roast the preheated pellets at a temperature of 1200°C - 1250°C for 9 - 11 min to obtain roasted pellets.

[0019] Furthermore, for the preparation method of the fluxed pellet containing specularite mentioned above, in Step 2, the green pellets have the following strength parameters: the drop strength ≥5.0 times / ball, and the compressive strength ≥10.0 N / ball.

[0020] Furthermore, for the preparation method of the fluxed pellet containing specularite mentioned above, in Step 3, the compressive strength of the obtained preheated pellets ≥450 N / ball; the compressive strength of the obtained roasted pellets ≥2300 N / ball.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] 1. The specific surface area of the specularite used in the present invention is relatively low;

[0023] 2. The proportion of specularite incorporated in the present invention is relatively large, within the range of 80% to 100%;

[0024] 3. When the compressive strength of the preheated balls in the present invention is ≥450 N / ball, the preheating temperature is 950 °C to 1000 °C, and the preheating time is 9 to 11 min. The preheating temperature is relatively low and the preheating time is relatively short, saving energy and reducing consumption;

[0025] 4. When the compressive strength of the roasted balls in the present invention is ≥2500 N / ball, the roasting temperature is 1200 °C to 1250 °C, and the roasting time is 9 to 11 min. The roasting temperature is relatively low and the roasting time is relatively short, also saving energy and reducing consumption;

[0026] 5. The magnetite, anthracite coal powder, limestone powder, and composite bentonite used in combination with specularite in the present invention are all relatively easy to obtain;

[0027] 6. The composite bentonite used in the present invention can not only reduce the amount of bentonite used, but also enable the pellets obtained by mixing specularite, magnetite, anthracite coal powder, and limestone powder to have good properties before entering the preheating section. Mixing corn starch with bentonite or bamboo fiber with bentonite alone cannot achieve such an effect. Detailed implementation mode

[0028] Example 1

[0029] A preparation method of a flux pellet containing specularite, comprising the following steps:

[0030] Step 1. Raw material preparation

[0031] The main chemical components of the specularite and magnetite in Example 1 are shown in Table 1:

[0032] Table 1

[0033]

[0034] After the specularite is subjected to high-pressure roll grinding, the specific surface area increases to more than 1200 cm 2 / g, the specific surface area of the magnetite is 1570 cm 2 / g, and the -200 mesh content of the limestone powder, anthracite coal powder, and composite bentonite is all more than 95%;

[0035] Step 2. Batching and pelletizing

[0036] In the case where the basicity of the pellet is 0.6, the mass percentage ratio of the concentrate is: specularite (calculated as dry ore) 80%, magnetite (calculated as dry ore) 20.0%. The externally added anthracite powder is 7%, the composite bentonite is 1.8%, and the limestone powder is 4.2%. The mass percentage content of each component in the composite bentonite is 30% corn starch, 30% bamboo fiber, and 40% sodium-based bentonite. The total water content of the mixed raw materials is controlled to be 7.5% of the dry weight of specularite and magnetite. After mixing the materials evenly, pelletizing is carried out on a disk pelletizer. The obtained green pellet has a drop strength of 5.8 times / ball, and the compressive strength of the green pellet is 12.0 N / ball;

[0037] Step 3: Preheating and roasting

[0038] After the green pellets are dried, preheating and roasting are carried out on a horizontal tube furnace. Under the conditions of a preheating temperature of 950 °C and a preheating time of 10 min, preheated pellets are obtained, and the compressive strength of the preheated pellets is about 560 N / ball; then the preheated pellets are roasted at a roasting temperature of 1200 °C and a roasting time of 10 min to obtain roasted pellets, and the compressive strength of the roasted pellets is 2840 N / ball.

[0039] Example 2

[0040] Step 1: Raw material preparation

[0041] The raw materials used in Example 2 are the same as those in Example 1.

[0042] Step 2: Batching and pelletizing

[0043] In the case where the basicity of the pellet is 0.8, the mass percentage ratio of the concentrate is: specularite (calculated as dry ore) 90%, magnetite (calculated as dry ore) 10%. The externally added anthracite powder is 9%, the composite bentonite is 2.0%, and the limestone powder is 3.8%. The mass percentage content of each component in the composite bentonite is 40% corn starch, 20% bamboo fiber, and 40% sodium-based bentonite. The total water content of the mixed raw materials is controlled to be 8% of the dry weight of specularite and magnetite. After mixing the materials evenly, pelletizing is carried out on a disk pelletizer. The obtained green pellet has a drop strength of 5.2 times / ball, and the compressive strength of the green pellet is 11.8 N / ball;

[0044] Step 3: Preheating and roasting

[0045] After the green pellets are dried, preheating and roasting are carried out on a horizontal tube furnace. Under the conditions of a preheating temperature of 960 °C and a preheating time of 10 min, preheated pellets are obtained, and the compressive strength of the preheated pellets is about 530 N / ball; then the preheated pellets are roasted at a roasting temperature of 1200 °C and a roasting time of 10 min to obtain roasted pellets, and the compressive strength of the roasted pellets is 2600 N / ball.

[0046] Example 3

[0047] Step 1: Raw material preparation

[0048] The raw materials used in Example 3 are the same as those in Example 1.

[0049] Step 2: Batching and pelletizing

[0050] When the basicity of the pellet ore is 1.0, the mass percentage ratio of the concentrate: specularite (calculated as dry ore) 90%, magnetite (calculated as dry ore) 10%. Externally added anthracite coal powder 9%, composite bentonite 2.1%, limestone powder 4.6%. The mass percentage content of each component in the composite bentonite is corn starch 50%, bamboo fiber 30%, sodium-based bentonite 20%. Control the total water content of the mixed raw materials to be 7.5% of the dry weight of specularite and magnetite. After mixing the materials evenly, pelletize them on a disc pelletizer. The obtained green pellet drop strength is 5.5 times / ball, and the green pellet compressive strength is 12.1 N / ball;

[0051] Step 3: Preheating and roasting

[0052] After drying the green pellets, preheat and roast them on a horizontal tube furnace. Under the conditions of a preheating temperature of 970 °C and a preheating time of 10 min, preheated pellets are obtained, and the preheated pellet compressive strength is about 503 N / ball; then the preheated pellets are roasted at a roasting temperature of 1200 °C and a roasting time of 10 min to obtain roasted pellets, and the roasted pellet compressive strength is about 2480 N / ball.

[0053] Example 4

[0054] Step 1: Raw material preparation

[0055] The raw materials used in Example 4 are the same as those in Example 1.

[0056] Step 2: Batching and pelletizing

[0057] When the basicity of the pellet ore is 1.2, the mass percentage ratio of the concentrate: specularite (calculated as dry ore) 100%, magnetite 0. Externally added anthracite coal powder 10%, composite bentonite 2.5%, limestone powder 5.5%. The mass percentage content of each component in the composite bentonite is corn starch 45%, bamboo fiber 25%, sodium-based bentonite 30%. Control the total water content of the mixed raw materials to be 8.5% of the dry weight of specularite. After mixing the materials evenly, pelletize them on a disc pelletizer. The obtained green pellet drop strength is 5.9 times / ball, and the green pellet compressive strength is 12.0 N / ball;

[0058] Step 3: Preheating and roasting

[0059] After drying the green pellets, preheat and roast them on a horizontal tube furnace. Under the conditions of a preheating temperature of 1000 °C and a preheating time of 10 min, preheated pellets are obtained, and the preheated pellet compressive strength is about 510 N / ball; then the preheated pellets are roasted at a roasting temperature of 1250 °C and a roasting time of 10 min to obtain roasted pellets, and the roasted pellet compressive strength is about 2430 N / ball.

[0060] Example 5

[0061] Step 1: Raw material preparation

[0062] The raw materials used in Example 5 are the same as those in Example 1.

[0063] Step 2: Batching and pelletizing

[0064] In the case where the pellet basicity is 1.2, the mass percentage ratio of the concentrate: specularite (calculated as dry ore) 100%, magnetite 0. The externally added anthracite coal is 9%, the composite bentonite is 2.3%, and the limestone powder is 5.1%. The mass percentage content of each component in the composite bentonite is 45% corn starch, 25% bamboo fiber, and 30% sodium-based bentonite. Control the total water content of the mixed raw materials to be 8% of the dry weight of the specularite. After mixing the materials evenly, pelletize them on a disc pelletizer. The obtained green pellet drop strength is 5.0 times / ball, and the green pellet compressive strength is 10.0 N / ball;

[0065] Step 3: Preheating and roasting

[0066] After drying the green pellets, preheat and roast them on a horizontal tube furnace. Under the conditions of a preheating temperature of 1000 °C and a preheating time of 10 min, preheated pellets are obtained, and the preheated pellet compressive strength is about 480 N / ball; then the preheated pellets are roasted at a roasting temperature of 1250 °C and a roasting time of 10 min to obtain roasted pellets, and the roasted pellet compressive strength is about 2320 N / ball.

Claims

1. A flux pellet containing specularite, characterized in that, The raw materials include the following mass percentages: specularite 80% - 100% based on dry ore, magnetite 20% - 0% based on dry ore, with an additional anthracite coal powder 7% - 12%, limestone powder 1.0% - 5.5%, and composite bentonite 1.5% - 2.5%; and the basicity range is 0.6 - 1.2; The specific surface area of specularite ≥ 1200 cm 2 / g; The particle size of the anthracite coal powder is such that the content of -200 mesh is ≥95%; The magnetite raw material is magnetite concentrate, and its specific surface area ≥ 1500 cm 2 / g; The mass percentages of the components in the composite bentonite are: corn starch 30% - 50%, bamboo fiber 20% - 30%, and sodium-based bentonite 20% - 40%.

2. The preparation method of the fluxed pellets containing specularite according to claim 1, characterized in that, It includes the following steps: Step 1. Raw material preparation Crush specularite by extrusion with a high-pressure roller mill to make the specific surface area of specularite ≥ 1200 cm 2 / g; finely grind anthracite coal powder to a particle size with a content of -200 mesh ≥ 95% using a ball mill; take magnetite concentrate and crush it by extrusion with a high-pressure roller mill, with its specific surface area ≥ 1500 cm 2 / g; Step 2. Batching and pelletizing Mix the specularite, magnetite, and anthracite coal powder obtained in Step 1 with the limestone powder and composite bentonite in proportion, and control the basicity range of the mixed raw materials to be 0.6 - 1.2; after mixing the mixed raw materials evenly, pelletize them, and control the total water content of the mixed raw materials to be 7.5% - 8.5% of the dry weight of the specularite and magnetite to obtain green pellets, and then dry them for standby; Step 3. Preheating and roasting Preheat and roast the dry green pellets obtained in Step 2. Under the conditions of a preheating temperature of 950°C - 1000°C and a preheating time of 9 - 11 min, obtain preheated pellets; then roast the preheated pellets at a temperature of 1200°C - 1250°C for 9 - 11 min to obtain roasted pellets.

3. The preparation method of the fluxed pellet containing specularite according to claim 2, characterized in that, In Step 2, the green pellets have the following strength parameters: drop strength ≥5.0 times / ball, compressive strength ≥10.0 N / ball.

4. The preparation method of the fluxed pellets containing specularite according to claim 2, characterized in that, In Step 3, the compressive strength of the obtained preheated pellets ≥450 N / ball; the compressive strength of the obtained roasted pellets ≥2300 N / ball.

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