Novel low-melting-point additive suitable for high-aluminum iron ore and sintering method of novel low-melting-point additive

Abstract

The invention relates to the field of ferrous metallurgy, in particular to a novel low-melting-point additive suitable for high-aluminum iron ore and a sintering method of the novel low-melting-point additive. The low-melting-point additive used in the invention is mature in preparation process, environment-friendly, low in preparation cost, free of extra equipment investment, low in addition proportion in the sintering process, free of increasing the production cost of the sintering procedure, wide in industrialization prospect, capable of being applied to iron ore resources such as high-aluminum iron ore and low-silicon iron ore, and suitable for industrial production. And the sintering temperature in the sintering process is obviously reduced. The method is different from a conventional low-carbon sintering process, high-aluminum iron ore low-carbon sintering can be achieved under the ultrahigh alkalinity, the method conforms to the structure that the high-aluminum iron ore is applied to the blast furnace slag in a full-proportion mode, meanwhile, the high-aluminum iron ore sintering product quality index is remarkably improved, and the carbon emission is greatly reduced.

Description

Technical Field

[0001] The invention relates to the field of iron and steel metallurgy, and in particular to a novel low melting point additive suitable for high-aluminum iron ore and a sintering method thereof. Background Art

[0004] High-aluminum iron ore has high Al2O3 content, aluminum-containing phase, poor reactivity, and complex occurrence state. Its liquid phase viscosity increases during sintering, the formation temperature rises, and the amount of production is insufficient. Its large-scale application not only leads to the deterioration of the technical and economic indicators of sintered ore, but also further aggravates the problem of high carbon emissions in the sintering process. In the traditional sintering process, the solid fuel for sintering conventional iron ore powder is mostly 30-50kg / t, while the solid fuel consumption for sintering high-aluminum iron ore can be as high as 70-90kg / t. The difficulty of sintering high-aluminum iron ore and its high carbon emissions have become one of the main problems in the steel industry.

[0005] At present, the research on low-carbon sintering of iron ore powder is mostly focused on optimizing ore blending technology, thick layer sintering technology, flue gas circulation and surface injection of hydrogen-rich fuel sintering technology, enhanced granulation technology, biomass fuel sintering technology, etc. (such as patents CN201210061527.6, CN201911144878.1, CN201810185838.0, CN201911028000.1, CN202210380967.1, CN202210371964.1, CN202210061505.3, CN201910205006.5, CN202310891992.0, etc.). The above-mentioned low-carbon sintering technologies mostly reduce carbon emissions by improving the external conditions of sintering. Even if one or more sintering technologies are used in combination, the emission reduction effect on the sintering process of full-proportion high-aluminum iron ore is very limited. Although the use of biomass fuels can reduce carbon emissions from the source, its substitution ratio is greatly limited, mostly not exceeding 40%, and can only partially replace fossil fuels such as coke powder.

[0006] The main reasons for the difficulty in sintering high-aluminum iron ore and high carbon emissions are that the liquid phase formation temperature in the sintering process is high, the amount generated is small, and the bonding effect is poor. The sintering temperature is above 1350°C, and a sufficiently high amount of solid fuel is often maintained to meet the needs of liquid phase formation. Therefore, adding low-melting point additives is one of the effective ways to sinter high-aluminum iron ore with low carbon. Patent CN202210050748.7 prepares calcium ferrite in advance, and then adds it to the sintering mixture for sintering, which has a carbon reduction effect in the sintering of vanadium-titanium magnetite. Patent CN202310222382.1 prepares low-melting point calcium-iron composite oxide by reduction method, which is also used in the conventional iron ore powder sintering process to reduce carbon. None of the relevant patents have research and examples on low-carbon sintering of high-aluminum iron ore. On the one hand, the sintering basicity of the former is around 2.2 at the conventional level. According to the inventor's patent CN202111093545.8, when high-aluminum iron ore is used in full proportion, its slag composition is converted to the sintering process, and the basicity of the sintered ore should be controlled at around 3.2. The application basicity of low-melting-point additives in the prior art is generally 2.2. Therefore, conventional low-melting-point additives cannot achieve full-proportion application of high-aluminum iron ore. On the other hand, the latter prepares calcium-iron composite oxide by reduction method, which has high initial preparation cost and poor process industrialization effect; its calcium-iron composite oxide ratio is high, and the embodiments are all above 7.5%, which greatly increases the sintering production cost and reduces the total iron content of the sintered ore; at its high ignition temperature of 1150±50℃, it is supplemented by processes such as adding better quality blast furnace return ore and grinding treatment of sintered return ore. Compared with the comparative example, the drum strength of the sintered ore in the optimal embodiment is only increased by 2.89%, which is only 4.23% higher than the same period last year, the solid fuel consumption is only reduced by 2.73kg / t, which is only 4.27% lower than the same period last year, and the yield is only increased by 2.98%, which is only 4.25% higher than the same period last year. The improvement does not exceed 5%, and the improvement effect is limited; in addition, it does not involve changes in production indicators such as sintered ore utilization coefficient, because the increase in the amount of liquid phase in the sintering process will inevitably slow down the sintering speed. It is not in line with actual production conditions to reduce carbon emissions at the expense of sintered ore output. Patent CN202310249656.6 adds MgF2 to the sintering mixture. Although it can improve the bonding phase composition of high-aluminum sintered ore and is beneficial to improving the strength of the sintered ore, its ignition temperature is as high as 1150-1250°C, and the basicity is in the conventional range of 1.7-2.1. At the same time, MgF2 is a harmful fluoride, which is easy to melt and volatilize during the sintering process, which is not conducive to the green and low-carbon development of the sintering process, and is also not conducive to the subsequent blast furnace process.

[0007] Therefore, a sintering method for high-aluminum iron ore with full proportion application that reduces the liquid phase formation temperature during the sintering process of high-aluminum iron ore, increases the amount of liquid phase formed, improves the sintering index of high-aluminum iron ore and reduces carbon emissions is urgently needed in the art. Summary of the invention

[0008] In view of the above problems, the purpose of the present invention is to provide a new low melting point additive suitable for high aluminum iron ore and a sintering method thereof. The melting point of the low melting point additive is only 1205°C. When added to the sintering raw material of high aluminum iron ore, the liquid phase formation temperature of the high aluminum iron ore can be significantly reduced during the sintering process, thereby reducing the sintering temperature, improving the sintering index of the high aluminum iron ore and reducing carbon emissions.

[0009] To this end, the first technical solution of the present application discloses a low melting point additive, comprising the following components:

[0010] Total iron: 38.69wt%;

[0011] FeO content 0.32wt%;

[0012] CaO content 31.75wt%;

[0013] SiO2 content 1.56wt%;

[0014] MgO content 1.23wt%;

[0015] Al2O3 content 0.52wt%;

[0016] The rest are impurities.

[0017] Furthermore, in the additive, the part with a particle size of ≤3 mm accounts for 60 to 80%.

[0018] The second technical solution of the present application discloses the use of the above-mentioned low melting point additive in reducing the liquid phase formation temperature during the sintering of high-aluminum iron ore.

[0019] Furthermore, the mass percentage of the low melting point additive in the sintering raw material is ≤8.00wt%.

[0020] The third technical solution of the present application discloses a high-aluminum iron ore sintering method, which comprises adding the above-mentioned low melting point additive to the sintering raw material.

[0021] Furthermore, after the sintering raw materials are mixed, the moisture content of the mixed material is controlled to be 9.65-10.40wt%.

[0022] Furthermore, the mass percentage of high-aluminum iron ore in the sintering raw material is 58.87wt% to 66.37wt%.

[0023] Furthermore, the ignition temperature during sintering is (1050±50)°C.

[0024] The beneficial effects of the present application are as follows: the preparation process of the low-melting-point additive used in the present application is mature and environmentally friendly, with low preparation cost and no need for additional equipment investment. At the same time, its addition ratio during the sintering process is low, which will not increase the production cost of the sintering process. It has broad industrial prospects and can be applied to iron ore resources such as high-aluminum iron ore and low-silicon iron ore, significantly reducing the sintering temperature during the sintering process.

[0025] This application is different from the conventional low-carbon sintering process. It can achieve low-carbon sintering of high-aluminum iron ore under ultra-high basicity, which is consistent with the blast furnace slag structure with full proportion application of high-aluminum iron ore (100% high-aluminum iron ore in iron ore powder). At the same time, the quality indicators of high-aluminum iron ore sintering are significantly improved, and carbon emissions are greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Attached Figure 1 The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific examples. This implementation case is implemented based on the technology of the present invention, and a detailed implementation method and specific operation process are now given to illustrate that the present invention is creative, but the protection scope of the present invention is not limited to the following examples.

[0028] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0029] In order to explain the present invention clearly, relevant technical terms are defined first.

[0030] The term "high-alumina iron ore" generally refers to iron ore powder with an Al2O3 content higher than 1.5wt%.

[0031] The term "low silicon iron ore" generally refers to iron ore powder with a SiO2 content of less than 4.0wt%.

[0032] The liquid phase formation temperature during the sintering process of two types of iron ore powder is relatively high.

[0033] The first embodiment of the present application discloses a low melting point additive, comprising the following components:

[0034] Total iron: 36.2-39.8wt%;

[0035] FeO content 0.3~5.5wt%;

[0036] CaO content 35.0~39.5wt%;

[0037] SiO2 content 1.2~4.0wt%;

[0038] MgO content 0.3-1.2wt%;

[0039] Al2O3 content 0.2~3.0wt%;

[0040] The rest are impurities.

[0041] In this embodiment, the additive has a thickness of 60-80 wt% in the 0-3 mm portion and a melting point of only 1205°C.

[0042] It should be noted that the particle size composition of the low melting point additive is similar to that of conventional sintering flux, and does not increase the difficulty of its sintering utilization.

[0043] It should be noted that the additive uses cheap 60-70wt% limonite and 30-40wt% limestone as raw materials, based on the belt roasting machine process (furnace size ), prepared under the conditions of preheating temperature of 800-850℃, preheating time of 6-10min, roasting temperature of 1000-1050℃, and roasting time of 6-8min. This preparation process adopts the belt roasting machine equipment commonly used in steel plants, without the need for additional equipment investment; at the same time, the use of the belt roasting machine process reduces the consumption of solid fossil fuels and solves the problem of kiln sticking and ring formation in the chain grate-rotary kiln preparation process. This preparation process is low-cost, low-carbon, environmentally friendly, and feasible.

[0044] It should be noted that, compared with other additives, the melting point of the additive in the present application is only 1205°C as measured by the hemispherical point test method. Compared with the additives mainly based on quicklime in the prior art (melting point above 2000°C) and other low-melting point additives, the additive in the present application has a lower melting point.

[0045] The second embodiment of the present application discloses the use of the low melting point additive in reducing the liquid phase formation temperature during the sintering of high-alumina iron ore.

[0046] In this embodiment, the low melting point additive accounts for ≤8.00wt% of the sintering raw material mass percentage. Compared with other additives, the additive is added at a low ratio during the sintering process, does not increase the production cost of the sintering process, and has broad industrial prospects.

[0047] It should be noted that the sintering raw materials include high-aluminum iron ore, the low-melting point additives of the present application, and other raw materials known to those skilled in the art, such as dolomite, quicklime, coke powder, returned ore, etc. The present application does not make any special limitations and only provides preferred embodiments.

[0048] In some preferred embodiments, the sintering raw materials include high-aluminum iron ore, dolomite, limestone, rubber powder, returned ore and low-melting point additives, wherein the mass percentage of the high-aluminum iron ore is 58.87-66.37wt%, the mass percentage of dolomite is 4.05-4.58wt%, the mass percentage of quicklime is 4.54-8.29wt%, the mass percentage of the new low-melting point additive is 0.00-8.00wt%, the mass percentage of coke powder is 4.50wt%, and the mass percentage of returned ore is 20.00wt%.

[0049] The above-mentioned return ore includes the return ore produced by the sintering process and the return ore from the blast furnace.

[0050] The third embodiment of the present application discloses a high-aluminum iron ore sintering method, which includes adding the above-mentioned low-melting point additive to the sintering raw materials. When the raw materials contain the above-mentioned low-melting point additive, the quality indicators of the sintered ore are significantly improved, the solid fuel consumption is greatly reduced, and the carbon emissions of the sintering process are significantly reduced.

[0051] It should be noted that, except for the above limitations, the remaining sintering steps such as mixing, granulation, ignition sintering and other processes are not beyond the consistent cognition of those skilled in the art. This application only provides preferred implementations, such as the specific implementations of this application disclosed below:

[0052] S1. Batching: batching high-aluminum iron ore, dolomite, quicklime, new low-melting-point additives, coke powder, returned ore and other raw materials according to the corresponding proportions of the ore batching plan;

[0053] S2, mixing and granulating: the sintered mixture in S1 is put into a drum mixer, water is added, and the mixing and granulating process is completed;

[0054] S3, ignition and sintering: After placing the base material at the bottom of the sintering cup (base material mass 2kg, material layer height 760mm), the sintering mixture after granulation in S2 is loaded into the sintering cup and ignited and sintered: the ignition time is 90s, the ignition temperature is (1050±50)℃, the ignition negative pressure is 6kPa, and the sintering negative pressure is 10kPa;

[0055] S4, cooling: after sintering, the sintered ore is cooled, and the cooling negative pressure is 6kPa. When the sintering flue gas temperature is lower than 100℃, the unloading begins;

[0056] S5. Sintered ore testing: After the S4 sintered ore is dropped (dropping height 2m, dropping times 3 times), the whole particles are screened, the mass of sintered ore of each particle size is recorded, and the drum strength of the sintered ore is measured by a drum device.

[0057] The low melting point additive described in the present application and its specific application in the sintering process of high-aluminum iron ore will be described below in conjunction with the accompanying drawings and specific embodiments.

[0058] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0059] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0060] Example Sintering of high-aluminum iron ore

[0061] The specific composition of the high-aluminum iron ore used in this embodiment is: total iron content 51.46wt%, FeO content 0.79wt%, CaO content 0.02wt%, SiO2 content 2.52wt%, MgO content 0.02wt%, Al2O3 content 6.18wt%, burn loss 8.11wt%, +8mm accounts for 6.32wt%, 3-6.3mm accounts for 33.77wt%, 1-3mm accounts for 25.25wt%, 0.5-1mm accounts for 7.29wt%, and -0.5mm accounts for 27.38wt%.

[0062] The suitable sintering ore basicity for the high-aluminum iron ore to achieve full-proportion application is 3.2. According to the inventor's preliminary research (patent CN202111093545.8), the blast furnace slag composition has a suitable slag-making range when the basicity is 2.0 and the aluminum-silicon ratio is 1.5. During the blast furnace smelting process, the components in the slag, in addition to the oxides brought in by the ore, also contain gangue components brought in by the combustion of fuel, mainly SiO2 and Al2O3, which will inevitably reduce the basicity of the slag. After calculation, when the basicity of the high-aluminum iron ore sinter is 3.2, the slag basicity can be guaranteed to be around 2.0, and a high-aluminum slag composition suitable for blast furnace smelting can be obtained through reasonable ore matching.

[0063] The specific sintering process used in this embodiment is as follows: Figure 1 As shown, specifically:

[0064] S1. Batching: Batching the raw materials to form a sintering mixture;

[0065] S2, mixing and granulation: put the S1 sintered mixture into a drum mixer, add water, and complete the mixing and granulation process. The mixing time is 8 minutes, the granulation time is 2 minutes, and the mixer speed is 8 r / min -1 , filling rate is 15%, and the moisture content of the mixture is controlled at 9.65~10.40wt%.

[0066] S3, ignition and sintering: After placing the base material at the bottom of the sintering cup, the base material mass is 2kg, and the sintering mixture after granulation in S2 is loaded into the sintering cup, the material layer height is 760mm, and ignition and sintering are carried out, the ignition time is 90s, the ignition temperature is (1050±50)℃, the ignition negative pressure is 6kPa, and the sintering negative pressure is 10kPa;

[0067] S4. Cooling: After sintering, the sintered ore is cooled with a cooling negative pressure of 6 kPa. When the sintering flue gas temperature is lower than 100°C, unloading begins.

[0068] S5. Sintered ore testing: After the S4 sintered ore is crushed by a double-roll crusher, it is screened for whole particles, the mass of sintered ore of each particle size is recorded, and the drum strength of the sintered ore is measured by a drum device.

[0069] The raw materials and proportions used in this embodiment are shown in Table 1.

[0070] Table 1 Raw materials and proportions

[0071]

[0072]

[0073] The quality indicators of the sintered ore obtained after the step S5 in the above embodiment are shown in Table 2.

[0074] Table 2 Sintered ore quality indicators

[0075]

[0076] Experimental results: Table 2 shows the quality indicators of high-aluminum iron ore sintered ore without low-melting-point additives at a basicity of 3.2. It can be seen that at a basicity of 3.2, the drum strength of the sintered ore is 52.63%, and the utilization coefficient is 1.47 t·m -2 ·h -1 , the yield is 75.81%, and the solid fuel consumption is 79.88kg / t. Under the condition of full application of high-aluminum iron ore and suitable sintering ore basicity of 3.2, the sintering ore quality indicators are poor, the solid fuel consumption is high, and the carbon emission is large.

[0077] Examples 1-6 show the effect of adding low melting point additives on the quality indicators of sintered ore under the basicity of high aluminum iron ore to achieve full proportion application: after adding 2.00-8.00wt% of the new low melting point additives during the sintering process of high aluminum iron ore, the drum strength of the sintered ore is 58.44-61.38%, and the utilization coefficient is 0.89-1.68t·m -2 ·h -1 , the yield is 79.84-81.88%, and the solid fuel consumption is 67.82-72.43 kg / t. Compared with comparative example 1, the method of the present invention, under the optimal conditions (Example 3), the sintering drum strength increased by 8.65%, an increase of 16.44% year-on-year, the yield increased by 6.07%, an increase of 8.01% year-on-year, and the utilization coefficient increased by 0.08 t·m -2 ·h -1 , an increase of 5.54% year-on-year, solid fuel consumption decreased by 12.06kg / t, a decrease of 15.10% year-on-year. Compared with the relevant inventions, it fills the gap in the full-proportion sintering of high-aluminum iron ore with ultra-high basicity. After applying the method of the present invention, under the condition of a low proportion of new low-melting-point additives, the quality index of high-aluminum iron ore is more significantly improved, and the carbon emission is more significantly reduced.

[0078] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred implementation cases, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A low melting point additive, characterized in that: Includes the following ingredients: Total iron: 36.2-39.8wt%; FeO content 0.3~5.5wt%; CaO content 35.0~39.5wt%; SiO2 content 1.2~4.0wt%; MgO content 0.3-1.2wt%; Al2O3 content 0.2~3.0wt%; The rest are impurities.

2. The low melting point additive according to claim 1, characterized in that: In the additive, the part with a particle size of ≤3 mm accounts for 60 to 80%.

3. Use of the low melting point additive according to claim 1 in reducing the liquid phase formation temperature during sintering of high-aluminum iron ore.

4. The use according to claim 3, characterized in that: The mass percentage of the low melting point additive in the sintering raw material is ≤8.00wt%.

5. A high-aluminum iron ore sintering method, characterized in that: The method comprises adding the low melting point additive as claimed in claim 1 to the sintering raw materials.

6. The sintering method according to claim 5, characterized in that: After the sintering raw materials are mixed, the moisture content of the mixed materials is controlled to be 9.65-10.40wt%.

7. The sintering method according to claim 5, characterized in that: The mass percentage of high-aluminum iron ore in the sintering raw material is 58.87wt% to 66.37wt%.

8. The sintering method according to claim 5, characterized in that: The ignition temperature during sintering is (1050±50)°C.

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