Method for sintering high proportion of fortified specularite

Abstract

This invention belongs to the field of iron ore sintering technology and discloses a method for strengthening the sintering of high-ratio specular hematite. S1. Raw material pretreatment: Returned ore and dried limonite are sieved using a 0.25mm sieve. Returned ore and limonite with a particle size smaller than 0.25mm are mixed with specular hematite powder and then pretreated by high-pressure roller milling. S2. Mixing and granulation: The mixture is mixed with returned ore and limonite larger than 0.25mm, other iron-containing minerals, flux, and fuel, and then granulated. S3. Pre-oxidation: The granulated mixture is distributed, and after distribution, the material layer is pre-oxidized using hot air. S4. Sintering: The mixture undergoes ignition, sintering, crushing, and cooling sequentially to produce the finished sintered ore. This invention effectively improves the proportion of specular hematite, significantly reduces sintering energy consumption, and increases the strength of the sintered ore.

Description

Technical Field

[0001] This invention relates to the field of iron ore sintering technology, and more specifically to a new method for strengthening the sintering of high-ratio specular hematite powder. Background Technology

[0002] In my country, 90% of crude steel is produced through a long process of sintering-blast furnace-converter. Therefore, sintering plays an important role in my country's steel smelting process, with sinter production exceeding 1.3 billion tons.

[0003] Specularite is a common variety of hematite and an important raw material for iron ore sintering. Specularite has a high iron grade, low levels of gangue components such as silica and alumina, and low content of harmful elements such as sulfur, phosphorus, potassium, and sodium, and its price is relatively low. Increasing the proportion of specularite in sintering blends plays a significant role in improving the iron grade of sintered ore, reducing sintering costs, and enhancing blast furnace ironmaking.

[0004] However, specular hematite has a coarse particle size, smooth surface, and extremely poor hydrophilicity. Furthermore, due to its good crystallinity, it has poor high-temperature performance, resulting in poor granulation performance, poor permeability of the mixture, high sintering energy consumption, and low sintering yield and quality. Therefore, the proportion of specular hematite in sintering blends is generally low, not exceeding 15%. Patent No. CN202511466233.5 provides a method for sintering high-alumina limonite and specular hematite blends, aiming to utilize the excellent composition of specular hematite to improve the high aluminum content of high-alumina limonite, thereby increasing the proportion of aluminum ore and reducing sintering costs. Patent No. CN202310930133.8 discloses a method for jointly inhibiting sintering embrittlement using limonite and specular hematite, aiming to improve the strength of the sintered ore through the combined effect of limonite and specular hematite. Patent No. CN201410644844.X provides a sinter containing specular hematite and a preparation method thereof, which improves the granulation performance of specular hematite by using binders and briquettes.

[0005] Currently, the utilization of specular hematite is mainly addressed through enhanced granulation, such as adding a high proportion of additives, pre-compression molding, pre-granulation, and high-pressure roller mill activation, to improve its pelletizing properties and increase its utilization ratio. However, the results are poor and the costs are high. Therefore, there is an urgent need to develop a new low-cost, enhanced sintering technology for high-proportion specular hematite. Summary of the Invention

[0006] In view of this, the present invention provides a sintering method for enhancing high-proportion specular hematite, the purpose of which is to utilize refractory specular hematite in a high proportion to provide high-quality sintered ore feedstock for blast furnace iron production.

[0007] To achieve the above objectives, the present invention provides a sintering method for enhancing high-ratio specular hematite, the specific steps of which include:

[0008] S1. Raw material pretreatment: After drying, the limonite is screened to separate two particle sizes: larger than 0.25 mm and smaller than 0.25 mm. At the same time, the return ore is screened with a 0.25 mm sieve. The return ore smaller than 0.25 mm and the limonite are mixed with specular hematite powder and then pretreated by high-pressure roller mill to obtain a mixture for later use. S2. Mixing and granulation: Mix the mixture with return ore and limonite larger than 0.25mm, other iron-bearing minerals, flux and fuel, and then granulate to obtain granulated mixture for later use. S3. Pre-oxidation: The granulated mixture is spread out, and after spreading, hot air is used to pre-oxidize the material layer. S4. Sintering: The finished sintered ore is prepared by sequentially igniting, sintering, crushing and cooling.

[0009] Further, the specific operation of step S1 is as follows: the limonite is dried in a drying kiln until the moisture content is less than 2%, and then screened in a 0.25mm vibrating screen; the return ore is also screened in a 0.25mm vibrating screen; the return ore smaller than 0.25mm and the limonite powder are mixed with the specular hematite powder, the moisture content is adjusted to 6.5%~7.5%, and then pre-treated by high-pressure roller mill.

[0010] Preferably, the pressure of the high-pressure roller mill pretreatment is 1.0~4.0 N / mm. 2 The scrap recycling rate is 20%~50%.

[0011] Preferably, the limonite powder is one or more of the following: limonite powder from Australia, Africa, or Brazil, such as super-fine powder, Silk Road powder, mixed powder, Yangdi powder, etc.

[0012] The beneficial effects of using the above-mentioned technical means are as follows: Because the limonite has good sphericity and high viscosity, wet ore is difficult to screen. Therefore, it needs to be dried in a drying kiln to a moisture content of less than 2%, and then screened in a 0.25mm vibrating screen. Particles larger than 0.25mm are core particles, and particles smaller than 0.25mm are adhering powder. Return ore is also screened in a 0.25mm vibrating screen to separate return ore core particles larger than 0.25mm and return ore adhering powder smaller than 0.25mm.

[0013] Furthermore, in step S2, the other iron-bearing minerals are one or more of hematite, magnetite, and steel plant solid waste; the flux is limestone, quicklime, and dolomite; and the fuel is one or more of coke powder and anthracite.

[0014] Preferably, the particle size of both flux and coke powder needs to be crushed to less than 3mm, accounting for more than 80%.

[0015] Furthermore, in step S2, the composition of the raw materials by mass is as follows: specular hematite accounts for 20-40%, limonite accounts for 15-40%, return ore accounts for 25-30%, and other iron-containing minerals account for 0-30%. Based on the aforementioned iron-containing minerals, the proportion of quicklime is 3%~5%, and the proportion of fuel is 3.5%~4.5%. It also includes adjusting the ratio of dolomite and limestone to achieve a binary basicity of 1.8 to 2.2 and an MgO content of 1.5% to 2.1% in the sinter.

[0016] Furthermore, the specific operation of step S2 is as follows: a high-intensity mixer and a cylindrical pelletizer are used respectively. The high-intensity mixer has a mixing moisture content of 7.0%~8.0%, a mixing time of 60~120s, and a rotation speed of 1000~3000r / min; the cylindrical pelletizer has a pelletizing time of 3~5min.

[0017] The beneficial effects of using the above-mentioned technical means are as follows: by using a high-power mixer and a cylindrical pelletizer, the proportion of particles larger than 3mm in the pellet mixture is more than 75%, and the air permeability index exceeds 45J.PU.

[0018] Furthermore, the specific operation of step S3 is as follows: the hot exhaust gas in the sintering ring cooler is introduced into the sintering material layer for pre-oxidation, and the temperature of the hot exhaust gas is controlled at 250~350℃, the oxidation time is 1-3min, and the exhaust negative pressure is 5-8kPa.

[0019] Further, the specific operation of step S4 is as follows: the height of the sintering material layer is 700~1000mm, the ignition negative pressure is controlled at 6kPa, the ignition temperature is (1100±50)℃, the ignition time is 1.5min, sintering is carried out under a sintering negative pressure of 13kPa, and after sintering, the hot sintered ore is crushed and cooled to obtain sintered ore.

[0020] Preferably, the negative pressure for cooling is 5 kPa, and the cooling time is 5 min.

[0021] As can be seen from the above technical solution, compared with the prior art, the beneficial effects achieved by the present invention include at least the following: (1) This invention addresses the problems of hematite having a dense structure, smooth surface, and poor hydrophilicity, resulting in poor surface wettability, poor granulation effect, and poor high-temperature reactivity, making it difficult to form low-melting-point compounds during conventional sintering and leading to high sintering energy consumption. A high-pressure roller mill mechanical activation pretreatment technology was developed. By increasing the lattice deformation degree of hematite, microcracks are formed within the particles, increasing surface roughness, increasing the fine particle size, significantly improving the specific surface area of ​​the iron concentrate, and significantly increasing the surface wetting heat, thereby improving its granulation performance. Simultaneously, the high-pressure roller mill, through mechanical activation, can convert some mechanical energy into free energy. Utilizing structural destruction such as the amorphization of iron ore, changes in surface area, grain size and strength, and phase transitions, internal fractures form numerous lattice defects, enhancing the surface activity of the material. This reduces the activation energy required for the reaction, promotes the solid-phase reaction during sintering, increases the amount of liquid phase formed during sintering, significantly reduces sintering energy consumption, and improves the strength of the sintered ore.

[0022] (2) This invention addresses the problems of poor high-temperature performance and granulation properties of specular hematite. It utilizes the characteristics of limonite adhesive powder (less than 0.25 mm), such as large specific surface area, strong adhesion, good high-temperature performance, and strong liquid-phase fluidity. The limonite adhesive powder is separated by sieving and then mixed with specular hematite. Under the action of a high-pressure roller mill, the limonite adhesive powder and specular hematite powder are brought into close contact. On the one hand, the good wettability and spheroidizing properties of the limonite adhesive powder improve the granulation performance of specular hematite and increase the air permeability of the granulated mixture. On the other hand, the good high-temperature reactivity of limonite improves the liquid-phase forming ability of specular hematite.

[0023] (3) In view of the problem that the poor reaction of specular hematite leads to high energy consumption of sintered solids, the present invention screens out the adhering powder of the returned ore. The returned ore is a clinker with advantages such as high alkalinity, good liquid phase formation ability and good high temperature reactivity. Through the action of high pressure roller mill, its contact with specular hematite is strengthened, the solid phase reaction is promoted, the formation of calcium ferrite is improved, the sintering quality is improved, and the solid energy consumption is reduced.

[0024] (4) This invention creatively developed a low-temperature pre-oxidation technology before sintering ignition. In response to the problem that when the proportion of limonite in the sintering process is high, the moisture content of the granulation mixture is high, which leads to severe over-wetting in the sintering process, reduces permeability, and affects the quality of sintering products, the hot waste gas of the sintering ring cooler is used to remove some moisture and increase the temperature of the sintering mixture, thereby reducing the over-wetting zone, improving the permeability and gas diffusion kinetics of the sintering process, and thus solving the contradiction between high moisture granulation and low water and low carbon sintering when sintering high proportion limonite. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The chemical composition and particle size distribution of the specular hematite, limonite, other iron ores (iron ore 1, iron ore 2, iron ore 3, and iron ore 4), flux (limestone, dolomite, and quicklime), and coke powder described in this invention are shown in Tables 1 and 2. During the sintering process, by maintaining a fixed proportion of quicklime (4%) and controlling the addition amounts of limestone and dolomite, the MgO content of the sintered product is kept constant at 1.8%, and the basicity is kept constant at 2.0.

[0027] Table 1 Chemical composition analysis of raw materials / wt%

[0028] Table 2. Particle composition of sintering raw materials / wt%

[0029] Example 1: The mixture consists of 25% specular hematite, 25% limonite, 22% other iron ores, and 28% recycled ore, for a total iron ore content of 100%. Based on the above iron-bearing ores, quicklime is added at a rate of 4%, coke powder at a rate of 3.8%, and the addition of limestone and dolomite is controlled to fix the MgO content of the sinter at 1.8% and the basicity at 2.0.

[0030] S1. Raw Material Pretreatment: The limonite is dried in a drying kiln to a moisture content of 1.8%, then sieved using a 0.25mm sieve to separate particles larger than 0.25mm and smaller than 0.25mm. Simultaneously, the returned ore is also sieved using a 0.25mm sieve. The limonite and returned ore smaller than 0.25mm are mixed with specular hematite powder, and the moisture content is adjusted to 6.5%~7.5%. Then, activation pretreatment is performed using a high-pressure roller mill; the high-pressure roller mill pressure is 3.0 N / mm². 2 The scrap recycling rate is 40%.

[0031] S2. Mixing and Granulation: The high-pressure roller milled material, limonite and return ore larger than 0.25mm, iron ore 1, iron ore 2, iron ore 3 and iron ore 4, flux and coke powder, with 8.5% water added, are then mixed in a high-intensity mixer for 120 seconds at a speed of 3000 r / min. Subsequently, the mixture is granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3mm in the granulated mixture was only 85.32%, and the air permeability index was 45.67 JPU.

[0032] S3. Pre-oxidation: The above granulated mixture is distributed in the sintering machine to a height of 800 mm. Then, the hot exhaust gas from the sintering ring cooler is introduced into the sintering material layer for pre-oxidation. The temperature of the hot exhaust gas is controlled at 300℃, the oxidation time is 2 min, and the exhaust negative pressure is 6 kPa.

[0033] S4. Sintering: After pre-oxidation, the ore is ignited, sintered, crushed, and cooled in a sintering machine. The ignition negative pressure is controlled at 6 kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5 min. Sintering is carried out under a sintering negative pressure of 13 kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5 kPa for 5 min to obtain the sintered ore.

[0034] The sintering utilization coefficient is only 1.32t / (m 2 The solid energy consumption is 58.72 kg / t, and the sinter drum strength is 72.34%.

[0035] Example 2: The mixture consists of 30% specular hematite, 30% limonite, 12% other iron ores, and 28% recycled ore, for a total iron ore content of 100%. Based on the above iron-bearing ores, quicklime is added at a rate of 4%, coke powder at a rate of 3.9%, and the addition of limestone and dolomite is controlled to keep the MgO content of the sintered product fixed at 1.8% and the alkalinity fixed at 2.0.

[0036] S1. Raw Material Pretreatment: The limonite is dried in a drying kiln to a moisture content of 1.8%, then sieved using a 0.25mm sieve to separate particles larger than 0.25mm and smaller than 0.25mm. Simultaneously, the returned ore is also sieved using a 0.25mm sieve. The limonite and returned ore smaller than 0.25mm are mixed with specular hematite powder, and the moisture content is adjusted to 7.0%. Then, activation pretreatment is performed using a high-pressure roller mill; the high-pressure roller mill pressure is 3.5 N / mm². 2 The scrap recycling rate is 40%.

[0037] S2. Mixing and Granulation: The high-pressure roller milled material, limonite and return ore larger than 0.25mm, iron ore 1, iron ore 2, iron ore 3 and iron ore 4, flux and coke powder, with 8.5% water added, are then mixed in a high-performance mixer for 100 seconds at a speed of 3000 r / min. Subsequently, the mixture is granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3mm in the granulated mixture was only 82.12%, and the air permeability index was 44.88 JPU.

[0038] S3. Pre-oxidation: The above granulated mixture is distributed in the sintering machine to a height of 800 mm. Then, the hot exhaust gas from the sintering ring cooler is introduced into the sintering material layer for pre-oxidation. The hot exhaust gas temperature is controlled at 300℃, the oxidation time is 1 min, and the exhaust negative pressure is 6 kPa.

[0039] S4. Sintering: The ore undergoes ignition, sintering, crushing, and cooling sequentially in the sintering machine. The ignition negative pressure is controlled at 6 kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5 min. Sintering is carried out under a sintering negative pressure of 13 kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5 kPa for 5 min to obtain the sintered ore.

[0040] The sintering utilization coefficient is only 1.30 t / (m 2 The solid energy consumption is 59.3 kg / t, and the sinter drum strength is 74.44%.

[0041] Example 3: The mixture consists of 40% specular hematite, 30% limonite, 25% return ore, and 5% other iron ores, totaling 100% iron minerals. Based on the above iron-bearing ores, quicklime is added at a rate of 4%, coke powder at a rate of 3.6%, and the amounts of limestone and dolomite are controlled to keep the MgO content of the sintered product fixed at 1.8% and the basicity fixed at 2.0.

[0042] S1. Raw Material Pretreatment: The limonite is dried in a drying kiln to a moisture content of 1.8%, then sieved using a 0.25mm sieve to separate particles larger than 0.25mm and smaller than 0.25mm. Simultaneously, the returned ore is also sieved using a 0.25mm sieve. The limonite and returned ore smaller than 0.25mm are mixed with specular hematite powder, and the moisture content is adjusted to 7.0%. Then, activation pretreatment is performed using a high-pressure roller mill; the high-pressure roller mill pressure is 4.0 N / mm². 2 The scrap recycling rate is 40%.

[0043] S2. Mixing and Granulation: The high-pressure roller milled material, limonite and return ore larger than 0.25mm, iron ore 1, iron ore 2, iron ore 3 and iron ore 4, flux and coke powder, with 8.5% water added, are then mixed in a high-intensity mixer for 110 seconds at a speed of 2800 r / min. Subsequently, the mixture is granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3mm in the granulated mixture was only 84.33%, and the air permeability index was 45.69 JPU.

[0044] S3. Pre-oxidation: The above granulated mixture is distributed in the sintering machine to a height of 800 mm. Then, the hot exhaust gas from the sintering ring cooler is introduced into the sintering material layer for pre-oxidation. The temperature of the hot exhaust gas is controlled at 250°C, the oxidation time is 1 min, and the exhaust negative pressure is 5 kPa.

[0045] S4. Sintering: The ore undergoes ignition, sintering, crushing, and cooling sequentially in the sintering machine. The ignition negative pressure is controlled at 6 kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5 min. Sintering is carried out under a sintering negative pressure of 13 kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5 kPa for 5 min to obtain the sintered ore.

[0046] The sintering utilization coefficient is only 1.33t / (m 2 The solid energy consumption is 55.56 kg / t, and the sinter drum strength is 75.38%.

[0047] Example 4: The mixture consists of 40% specular hematite, 35% limonite, and 25% recycled ore, for a total iron mineral content of 100%. Based on the above iron-bearing ore, quicklime is added at a rate of 4%, coke powder at a rate of 3.6%, and the addition of limestone and dolomite is controlled to fix the MgO content of the sinter at 1.8% and the basicity at 2.0.

[0048] S1. Raw Material Pretreatment: The limonite is dried in a drying kiln to a moisture content of 1.8%, then sieved using a 0.25mm sieve to separate particles larger than 0.25mm and smaller than 0.25mm. Simultaneously, the returned ore is also sieved using a 0.25mm sieve. The limonite and returned ore smaller than 0.25mm are mixed with specular hematite powder, and the moisture content is adjusted to 7.0%. Then, activation pretreatment is performed using a high-pressure roller mill; the high-pressure roller mill pressure is 4.0 N / mm². 2 The scrap recycling rate is 40%.

[0049] S2. Mixing and Granulation: The high-pressure roller milled material, limonite and return ore larger than 0.25mm, iron ore 1, iron ore 2, iron ore 3 and iron ore 4, flux and coke powder, with 8.5% water added, are then mixed in a high-intensity mixer for 110 seconds at a speed of 2800 r / min. Subsequently, the mixture is granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3mm in the granulated mixture was only 84.33%, and the air permeability index was 45.69 JPU.

[0050] S3. Pre-oxidation: The above granulated mixture is distributed in the sintering machine to a height of 800 mm. Then, the hot exhaust gas from the sintering ring cooler is introduced into the sintering material layer for pre-oxidation. The temperature of the hot exhaust gas is controlled at 300°C, the oxidation time is 2 min, and the exhaust negative pressure is 6 kPa.

[0051] S4. Sintering: The ore undergoes ignition, sintering, crushing, and cooling sequentially in the sintering machine. The ignition negative pressure is controlled at 6 kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5 min. Sintering is carried out under a sintering negative pressure of 13 kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5 kPa for 5 min to obtain the sintered ore.

[0052] The sintering utilization coefficient is only 1.37t / (m 2 The solid energy consumption is 52.16 kg / t, and the sinter drum strength is 78.92%.

[0053] Comparative Example 1: The iron ore composition consists of 30% specular hematite, 10% iron ore 1, 10% iron ore 2, 10% iron ore 3, and 12% iron ore 4, plus 28% return ore, totaling 100% iron minerals. Based on the above iron-bearing ore, quicklime is added at a ratio of 4%, coke powder at a dosage of 4.2%, and the addition of limestone and dolomite is controlled to fix the MgO content of the sinter at 1.8% and the basicity at 2.0.

[0054] After mixing the iron ore, flux, and coke powder, 8.0% water was added, and then the mixture was stirred in a high-intensity mixer for 120 seconds at a speed of 3000 r / min. Next, the mixture was granulated in a cylindrical pellet mill for 5 minutes. Testing showed that only 68% of the granulated mixture had particles larger than 3 mm, and the air permeability index was 37.6 JPU.

[0055] The material undergoes sequential processes in the sintering machine, including feeding, ignition, sintering, crushing, and cooling. The feeding height is 800 mm, the ignition negative pressure is controlled at 6 kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5 min. Sintering is carried out under a sintering negative pressure of 13 kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5 kPa for 5 min to obtain the sintered ore.

[0056] The sintering utilization coefficient is only 1.12t / (m 2 The solid energy consumption is 62.4 kg / t, and the sinter drum strength is 68.72%.

[0057] Comparative Example 2: The iron ore composition consists of 40% specular hematite, 8% iron ore 1, 8% iron ore 2, 8% iron ore 3, and 8% iron ore 4, plus 28% return ore, totaling 100% iron minerals. Based on the above iron-bearing ore, quicklime is added at a ratio of 4%, coke powder at a dosage of 4.4%, and the addition of limestone and dolomite is controlled to fix the MgO content of the sinter at 1.8% and the basicity at 2.0.

[0058] After mixing the iron ore, flux, and coke powder, 8.5% water was added, and then the mixture was stirred in a high-intensity mixer for 120 seconds at a speed of 3000 r / min. Subsequently, the mixture was granulated in a cylindrical pellet mill for 5 minutes. Testing showed that the proportion of particles larger than 3 mm in the granulated mixture was only 63.2%, and the air permeability index was 34.2 JPU.

[0059] The material undergoes sequential processes in the sintering machine, including feeding, ignition, sintering, crushing, and cooling. The feeding height is 800 mm, the ignition negative pressure is controlled at 6 kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5 min. Sintering is carried out under a sintering negative pressure of 13 kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5 kPa for 5 min to obtain the sintered ore.

[0060] The sintering utilization coefficient is only 1.02 t / (m 2 The solid energy consumption is 64.4 kg / t, and the sinter drum strength is 65.72%.

[0061] Comparative Example 3: The iron ore composition consists of 30% specular hematite, 10% iron ore 1, 10% iron ore 2, 10% iron ore 3, and 12% iron ore 4, plus 28% return ore, totaling 100% iron minerals. Based on the above iron-bearing ore, quicklime is added at a ratio of 4%, coke powder at a dosage of 4.1%, and the addition of limestone and dolomite is controlled to fix the MgO content of the sinter at 1.8% and the basicity at 2.0.

[0062] S1. Raw material pretreatment: Specimenite is activated and pretreated using a high-pressure roller mill; the high-pressure roller mill pressure is 3.5 N / mm. 2 The scrap recycling rate is 40%, and the moisture content is 7.0%.

[0063] S2. Mixing and Granulation: The high-pressure roller mill material, return ore, iron ore 1, iron ore 2, iron ore 3, and iron ore 4, flux, and coke powder were mixed with 8.5% water in a high-intensity mixer for 120 seconds at 3000 rpm. Subsequently, the mixture was granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3 mm in the granulated mixture was only 74.56%, and the air permeability index was 39.87 JPU.

[0064] S3. Sintering: The sintering process involves feeding, ignition, sintering, crushing, and cooling in the sintering machine. The feeding height is 800mm. The ignition negative pressure is controlled at 6kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5min. Sintering is carried out under a sintering negative pressure of 13kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5kPa for 5min to obtain the sintered ore.

[0065] The sintering utilization coefficient is only 1.20 t / (m 2 The solid energy consumption is 60.7 kg / t, and the sinter drum strength is 73.66%.

[0066] Comparative Example 4: The mixture consists of 30% specular hematite, 30% limonite, 12% other iron ores, and 28% recycled ore, for a total iron ore content of 100%. Based on the above iron-bearing ores, quicklime is added at a rate of 4%, coke powder at a rate of 3.9%, and the addition of limestone and dolomite is controlled to keep the MgO content of the sintered product fixed at 1.8% and the alkalinity fixed at 2.0.

[0067] S1. Raw Material Pretreatment: The return ore is also screened using a 0.25mm sieve. Return ore particles smaller than 0.25mm are mixed with specular hematite powder, and the moisture content is adjusted to 7.0%. Then, activation pretreatment is performed using a high-pressure roller mill; the high-pressure roller mill pressure is 3.5 N / mm². 2 The scrap recycling rate is 40%.

[0068] S2. Mixing and Granulation: The high-pressure roller milled material, return ore larger than 0.25mm, limonite, iron ore 1, iron ore 2, iron ore 3, and iron ore 4, flux, and coke powder were mixed with 8.5% water and then homogenized in a high-performance mixer for 100 seconds at a speed of 3000 r / min. Subsequently, the mixture was granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3mm in the granulated mixture was only 80.11%, and the air permeability index was 41.45 JPU.

[0069] S3. Pre-oxidation: The above granulated mixture is distributed in the sintering machine to a height of 800 mm. Then, the hot exhaust gas from the sintering ring cooler is introduced into the sintering material layer for pre-oxidation. The hot exhaust gas temperature is controlled at 300℃, the oxidation time is 1 min, and the exhaust negative pressure is 6 kPa.

[0070] S4. Sintering: The ore undergoes ignition, sintering, crushing, and cooling sequentially in the sintering machine. The ignition negative pressure is controlled at 6 kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5 min. Sintering is carried out under a sintering negative pressure of 13 kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5 kPa for 5 min to obtain the sintered ore.

[0071] The sintering utilization coefficient is only 1.27t / (m 2 The solid energy consumption is 60.22 kg / t, and the sinter drum strength is 69.88%.

[0072] Comparative Example 5: The mixture consists of 40% specular hematite, 30% limonite, 25% return ore, and 5% other iron ores, totaling 100% iron minerals. Based on the above iron-bearing ores, quicklime is added at a rate of 4%, coke powder at a rate of 3.6%, and the amounts of limestone and dolomite are controlled to keep the MgO content of the sintered product fixed at 1.8% and the basicity fixed at 2.0.

[0073] S1. Raw Material Pretreatment: The limonite is dried in a drying kiln to a moisture content of 1.8%, then sieved using a 0.25mm sieve to separate particles larger than 0.25mm and smaller than 0.25mm. The limonite particles smaller than 0.25mm are mixed with specular hematite powder, and the moisture content is adjusted to 7.0%. Then, a high-pressure roller mill is used for activation pretreatment; the high-pressure roller mill pressure is 4.0 N / mm². 2 The scrap recycling rate is 40%.

[0074] S2. Mixing and Granulation: The high-pressure roller milled material, limonite and return ore larger than 0.25mm, iron ore 1, iron ore 2, iron ore 3 and iron ore 4, flux and coke powder, with 8.5% water added, are then mixed in a high-performance mixer for 110 seconds at a speed of 2800 r / min. Subsequently, the mixture is granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3mm in the granulated mixture was only 81.983%, and the air permeability index was 44.72 JPU.

[0075] S3. Pre-oxidation: The hot exhaust gas from the sintering ring cooler is introduced into the sintering material layer for pre-oxidation. The temperature of the hot exhaust gas is controlled at 250°C, the oxidation time is 1 minute, and the negative pressure of the exhaust is 5 kPa.

[0076] S4. Sintering: The sintering process involves ignition, sintering, crushing, and cooling in a sintering machine. The sintering material height is 800mm, the ignition negative pressure is controlled at 6kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5min. Sintering is carried out under a sintering negative pressure of 13kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5kPa for 5min to obtain the sintered ore.

[0077] The sintering utilization coefficient is only 1.27t / (m 2 The solid energy consumption is 59.78 kg / t, and the sinter drum strength is 72.12%.

[0078] Comparative Example 6: The mixture consists of 40% specular hematite, 35% limonite, and 25% recycled ore, for a total iron mineral content of 100%. Based on the above iron-bearing ore, quicklime is added at a rate of 4%, coke powder at a rate of 3.6%, and the addition of limestone and dolomite is controlled to fix the MgO content of the sinter at 1.8% and the basicity at 2.0.

[0079] S1. Raw Material Pretreatment: The limonite is dried in a drying kiln to a moisture content of 1.8%, then sieved using a 0.25mm sieve to separate particles larger than 0.25mm and smaller than 0.25mm. Simultaneously, the returned ore is also sieved using a 0.25mm sieve. The limonite and returned ore smaller than 0.25mm are mixed with specular hematite powder, and the moisture content is adjusted to 7.0%. Then, activation pretreatment is performed using a high-pressure roller mill; the high-pressure roller mill pressure is 4.0 N / mm². 2 The scrap recycling rate is 40%.

[0080] S2. Mixing and Granulation: The high-pressure roller milled material, limonite and return ore larger than 0.25mm, iron ore 1, iron ore 2, iron ore 3 and iron ore 4, flux and coke powder, with 8.5% water added, are then mixed in a high-intensity mixer for 110 seconds at a speed of 2800 r / min. Subsequently, the mixture is granulated in a cylindrical granulator for 5 minutes. Testing showed that the proportion of particles larger than 3mm in the granulated mixture was only 84.33%, and the air permeability index was 45.69 JPU.

[0081] S3. Sintering: Without pre-oxidation, the material passes through the sintering machine sequentially, including feeding, ignition, sintering, crushing, and cooling. The feeding height is 800mm. The ignition negative pressure is controlled at 6kPa, the ignition temperature at (1100±50)℃, and the ignition time at 1.5min. Sintering is carried out under a sintering negative pressure of 13kPa. After sintering, the hot sintered ore is crushed and then cooled by a ring-type blower cooler at a cooling negative pressure of 5kPa for 5min to obtain the sintered ore.

[0082] The sintering utilization coefficient is only 1.32t / (m 2 The solid energy consumption is 54.79 kg / t, and the sinter drum strength is 76.12%.

[0083] Comparison of Comparative Example 1 and Comparative Example 2 shows that increasing the amount of specular hematite leads to a comprehensive deterioration in granulation and sintering performance.

[0084] Comparison of Comparative Example 1 and Comparative Example 3 shows that the activation pretreatment of specular hematite using high-pressure roller mill pretreatment technology improves its granulation performance and sintering effect.

[0085] A comparison of Comparative Example 4 and Example 2 shows that by utilizing the characteristics of goethite adhesive powder (less than 0.25 mm), such as large specific surface area, strong adhesion, good high-temperature performance, and strong liquid phase fluidity, sieving it separately can improve the granulation performance of specular hematite powder and improve the sintering effect.

[0086] A comparison of Comparative Example 5 and Example 3 shows that by screening out the adhering powder of the returned ore, and utilizing its advantages such as high alkalinity, good liquid phase formation ability, and good high-temperature reactivity, the contact between it and specular hematite is enhanced through the action of high-pressure roller mill, promoting solid-phase reaction, improving the formation of calcium ferrite, improving sintering quality, and reducing solid energy consumption.

[0087] A comparison of Comparative Example 6 and Example 4 shows that the low-temperature pre-oxidation technology before sintering removes some moisture and increases the temperature of the sintering mixture, thereby reducing the wet zone, improving the permeability and gas diffusion kinetics during the sintering process, and thus improving the quality of the sintering product.

[0088] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sintering method for enhancing high-ratio specular hematite, characterized in that, The specific steps include: S1. Raw material pretreatment: The returned ore and dried limonite are screened using a 0.25mm sieve. The returned ore and limonite with a particle size smaller than 0.25mm are mixed with specular hematite powder and then pretreated by high-pressure roller mill to obtain a mixture for later use. S2. Mixing and granulation: Mix the mixture with return ore and limonite larger than 0.25mm, other iron-bearing minerals, flux and fuel, and then granulate to obtain granulated mixture for later use. S3. Pre-oxidation: The granulated mixture is spread out, and after spreading, hot air is used to pre-oxidize the material layer. S4. Sintering: The finished sintered ore is prepared by sequentially igniting, sintering, crushing and cooling.

2. The sintering method for strengthening high-ratio specular hematite according to claim 1, characterized in that, The specific operation of step S1 is as follows: dry the limonite to a moisture content of less than 2%, and then screen it in a 0.25mm vibrating screen; the return ore is also screened in a 0.25mm vibrating screen; after mixing the return ore smaller than 0.25mm and the limonite powder with the specular hematite powder, adjust the moisture content to 6.5%~7.5%, and then perform high-pressure roller mill pretreatment.

3. The sintering method for strengthening high-ratio specular hematite according to claim 2, characterized in that, The pressure of the high-pressure roller mill pretreatment is 1.0~4.0 N / mm. 2 The scrap recycling rate is 20%~50%.

4. The sintering method for strengthening high-ratio specular hematite according to claim 2, characterized in that, The limonite powder is one or more of the following: limonite powder from Australia, Africa, or Brazil.

5. The sintering method for strengthening high-ratio specular hematite according to claim 1, characterized in that, In step S2, the other iron-bearing minerals are one or more of hematite, magnetite, and steel plant solid waste; the flux is limestone, quicklime, and dolomite; and the fuel is one or more of coke powder and anthracite.

6. The sintering method for strengthening high-ratio specular hematite according to claim 5, characterized in that, In step S2, the raw materials are composed of the following by mass ratio: specular hematite 20-40%, limonite 15-40%, return ore 25-30%, and other iron-containing minerals 0-30%. Based on the aforementioned iron-containing minerals, the proportion of quicklime is 3%~5%, and the proportion of fuel is 3.5%~4.5%. It also includes adjusting the ratio of dolomite and limestone to achieve a binary basicity of 1.8 to 2.2 and an MgO content of 1.5% to 2.1% in the sinter.

7. The sintering method for strengthening high-ratio specular hematite according to claim 1, characterized in that, The specific operation of step S2 is as follows: a high-intensity mixer and a cylindrical pelletizer are used respectively. The high-intensity mixer has a mixing moisture content of 7.0%~8.0%, a mixing time of 60~120s, and a rotation speed of 1000~3000r / min. The pelletizing time of the cylindrical pelletizer is 3~5min.

8. The sintering method for strengthening high-ratio specular hematite according to claim 1, characterized in that, The specific operation of step S3 is as follows: the hot exhaust gas in the sintering ring cooler is introduced into the sintering material layer for pre-oxidation, and the temperature of the hot exhaust gas is controlled at 250~350℃, the oxidation time is 1-3min, and the exhaust negative pressure is 5-8kPa.

9. The sintering method for strengthening high-ratio specular hematite according to claim 1, characterized in that, The specific operation of step S4 is as follows: the height of the sintering material layer is 700~1000mm, the ignition negative pressure is controlled at 6kPa, the ignition temperature is (1100±50)℃, the ignition time is 1.5min, and sintering is carried out under a sintering negative pressure of 13kPa. After sintering, the hot sintered ore is crushed and cooled to obtain sintered ore.

10. A sintering method for strengthening high-ratio specular hematite according to claim 9, characterized in that, The cooling negative pressure is 5 kPa, and the cooling time is 5 min.

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