Process for producing magnetite fine powder by utilizing siderite rich powder

Abstract

The invention discloses a process for producing magnetite fine powder by utilizing siderite rich powder. The process specifically comprises the following steps: (1) feeding a raw material siderite into a dry-method vertical ore grinding machine through a variable-frequency vibrating feeder; (2) mineral particles generated by ore grinding are heated and separated by using circulating flue gas; (3) dust-containing flue gas firstly passes through a gravity dust collector and a primary heat exchanger for heat exchange, then passes through a cloth bag dust collector for dust removal and passes through a secondary heat exchanger for heat exchange; and (4) the flue gas subjected to heat exchange enters a backflow baffle door through a variable-frequency circulating fan, part of the flue gas is discharged, the rest of the flue gas is conveyed to a flue gas inlet header pipe of a dry-method vertical ore grinding machine through the backflow baffle door to be mixed with flue gas of a flue gas furnace, the mixed flue gas enters the dry-method vertical ore grinding machine to be used for heating and sorting siderite, the siderite is decomposed in the heating process, and the siderite is discharged. Magnetite fine powder is obtained; the process is simple and easy to implement, and the magnetite fine powder is produced from the siderite rich powder through dry grinding, so that the purposes of reducing the production cost of sintered ore and pellets, improving the productivity and reducing the comprehensive energy consumption are achieved.

Description

Technical Field

[0001] The present invention relates to a production process of magnetite concentrate powder, specifically to a process for producing magnetite concentrate powder by using siderite rich powder, belonging to the technical field of mineral processing. Background Art

[0002] The proven reserves of siderite in China are about 1 billion to 2 billion tons, and China is a large country with siderite reserves in the world. Siderite is a kind of carbonate, and its chemical formula is: FeCO3, with a theoretical iron content of 48.2%. Due to the low iron content of siderite (the theoretical iron content is only 48.2%, and the actual mining grade is even lower), and the high smelting cost, large-scale development is less.

[0003] In China, when applying siderite to the iron and steel smelting industry, it cannot be directly used in the sintering and pelletizing processes, which will cause the granulated balls to burst during the heating and roasting processes, deteriorate the working conditions of the sintering and pelletizing production processes, and increase the return ore rate. Generally, it is first crushed into blocks and then subjected to magnetization roasting before being used as the raw material for the sintering process. Due to roasting in blocks, it is difficult for O +2 to migrate from the surface of the lump ore to the inside, and it is also difficult for external heat to transfer to the inside of the lump ore. The roasting time is long, the equipment for magnetization roasting consumes a high amount of energy, resulting in a decrease in the cost performance of the roasted product; the porosity of the roasted magnetite is high, which causes a decrease in the physical strength of the sintered ore when used as the iron raw material in the sintering process. To be used as concentrate powder, it must go through the grinding process. Therefore, siderite is less used in the iron and steel smelting industry.

[0004] In the processing of products (sintered ore, pelletized ore) in the front-end process of iron in iron and steel enterprises, in order to ensure that the sintered ore and pelletized ore have appropriate physical properties and metallurgical properties, a certain proportion of concentrate powder needs to be added. Adding concentrate powder to the sintered ore for granulation can generate an appropriate proportion of liquid phase for bonding and agglomeration; for pelletized ore, taking advantage of the characteristics of the large specific surface area and strong capillary water adsorption ability of the concentrate powder, granulation and ball-making are carried out, and through roasting, solid-liquid phase reaction occurs for consolidation. By using the dry grinding process to grind, heat decompose, oxidize, and separate siderite, it is equivalent to combining the magnetization roasting and grinding processes for producing magnetite concentrate powder from siderite into one process. During the process of grinding siderite, it is heated and decomposed, which takes a short time, consumes relatively less energy, and requires less equipment investment.

[0005] Currently, the mainstream of iron concentrate powder is magnetite concentrate powder. Magnetite concentrate powder is produced through the grinding - beneficiation process. During the roasting and oxidation process of magnetite, heat is released from the inside of the pelletized ore, reducing the required amount of external flue gas heating, shortening the roasting time and temperature, and making the pelletized ore heat more evenly. Therefore, magnetite is superior to hematite as the raw material for pellets. The demand for magnetite is increasing. Finding a process to convert siderite rich powder into magnetite concentrate powder can not only effectively utilize siderite resources but also meet the demand for magnetite.

[0006] Patent CN101348860B describes a method for producing porous activated magnetite. After grinding and classifying the raw materials, a magnetic separator is used to remove small particle minerals and non-magnetic materials, and then porous activated magnetite is obtained through dehydration and reduction, which has strong adsorption capacity and high activity. Patent CN108504855B discloses a method for producing iron concentrate by reduction suspension magnetization roasting of siderite. The content of siderite in refractory iron ore is controlled, and CO generated by the decomposition of siderite is fully utilized as a reducing agent during roasting. Weakly magnetic minerals such as hematite and limonite are reduced to magnetite by CO. However, there are problems in separating non-magnetic impurities in the above two patents. To separate non-magnetic impurities, a multi-stage magnetic separation - reverse flotation combined process is required, which has a high cost, and strongly magnetic mineral particles are prone to agglomeration, resulting in the "magnetic capping" phenomenon, entraining gangue, and affecting the concentrate grade.

[0007] Therefore, it has become an urgent technical problem for those skilled in the art to develop a process for converting siderite rich powder into magnetite concentrate powder that is simple to operate, low in cost, and low in energy consumption. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a process for producing magnetite concentrate powder using siderite rich powder. This process is simple and feasible, and uses siderite rich powder to produce magnetite concentrate powder through dry grinding, obtaining concentrate powder with a large specific surface area, good pelletizing effect, and being more suitable for sintering and pellet production needs, so as to achieve the purpose of reducing the production cost of sintered ore and pellet ore, improving productivity, and reducing comprehensive energy consumption.

[0009] To solve the above technical problems, the present invention provides a process for producing magnetite concentrate powder using siderite rich powder, which specifically includes the following steps: (1) The raw material siderite is fed into a dry vertical grinding mill through a variable frequency vibrating feeder to adjust the flow rate. (2) The mineral particles generated during grinding are heated and separated using recycled flue gas, and then captured by a gravity dust collector and a bag filter. (3) The dust-containing flue gas first removes ≥70% of the mineral particles through a gravity dust collector, then exchanges heat through a primary heat exchanger to reduce the flue gas temperature to ≤350°C, and then is dusted by a bag filter. After dust removal, the flue gas exchanges heat again through a secondary heat exchanger, and the temperature of the flue gas after heat exchange is ≤150°C. (4) The flue gas after heat exchange in step (3) enters an adjustable reflux baffle door through a variable frequency circulation fan. Part of the flue gas is directly discharged, and the remaining part is transported by the reflux baffle door to the main flue gas inlet pipe of the dry vertical grinding mill. It is mixed with the high-temperature flue gas of the flue gas furnace at the main flue gas inlet pipe of the dry vertical grinding mill, and the mixed high-temperature flue gas enters the dry vertical grinding mill to heat and separate the siderite. During the heating process, the siderite decomposes to obtain magnetite concentrate powder.

[0010] The further limited technical solution of the present invention is as follows: Further, in the process of using siderite rich powder to produce magnetite concentrate powder, in step (1), the moisture content of the raw material siderite is ≤ 9%.

[0011] In the process of using siderite rich powder to produce magnetite concentrate powder, in step (2), the flue gas is the mixed high-temperature flue gas in step (3), and the flue gas temperature is 550°C ≤ flue gas temperature ≤ 650°C.

[0012] In the process of using siderite rich powder to produce magnetite concentrate powder, in step (3), after passing through the gravity dust collector, the removal rate of mineral particles is ≥ 70%.

[0013] In the process of using siderite rich powder to produce magnetite concentrate powder, in step (3), after passing through the bag filter, the dust content of the flue gas is ≤ 10 mg / m 3 .

[0014] In the process of using siderite rich powder to produce magnetite concentrate powder, in step (3), the heat exchange all adopts air series heat exchange. The cold air is connected through the secondary heat exchanger, passes through the primary heat exchanger, and finally enters the flue gas furnace. The heated air after heat exchange is used for the combustion support of the flue gas furnace; the fuel of the flue gas furnace uses blast furnace gas.

[0015] In the process of using siderite rich powder to produce magnetite concentrate powder, the particle size requirement of the obtained magnetite concentrate powder is: the particle size grade of -0.074 mm ≥ 80%.

[0016] The present invention also designs a device for using siderite rich powder to produce magnetite concentrate powder, which includes a storage bin, a vibrating feeder, a dry grinding mill, a gravity dust collector, a primary heat exchanger, a bag filter, a secondary heat exchanger, a variable frequency circulating fan and a reflux baffle door connected in sequence. The dry grinding mill is externally connected to the flue gas main pipe and the flue gas furnace in sequence. The reflux baffle door is connected to the flue gas main pipe through a pipeline. The inlet end of the secondary heat exchanger is externally connected to cold air, the outlet end of the secondary heat exchanger is connected in series with the primary heat exchanger through a pipeline, the outlet end of the primary heat exchanger is connected to the inlet end of the flue gas furnace through a pipeline, the inlet end of the flue gas furnace is also externally connected to blast furnace gas, and the outlet end of the flue gas furnace is communicated with the flue gas main pipe.

[0017] The beneficial effects of the present invention are as follows: The conditions for siderite to decompose into magnetite by heating are as follows: 1) Temperature range: 500°C to 700°C (optimal range): Therefore, in the present invention, the temperature of the flue gas is strictly controlled at 550 - 650°C. If the temperature is too low, the reaction is slow; if it is too high, it may lead to over-oxidation (formation of Fe2O3). 2) Oxygen control: Limited oxygen supply needs to be maintained (such as moderate air flow or partial oxidation in a closed system) to avoid complete oxidation to hematite (Fe2O3). 3) Reaction atmosphere: In a neutral or weakly oxidizing atmosphere (such as a mixture of air and inert gas), it promotes the conversion of FeO to Fe3O4. The dry grinding process of the present invention meets the above conditions. Siderite can be decomposed by heating during the transportation and separation process using high-temperature flue gas through the dry grinding process to obtain magnetite concentrate powder. Since siderite (hardness 3.5 ≤ hardness ≤ 4.5) is relatively soft and may be fragile due to carbonate cleavage, it has good grindability, low grinding energy consumption, and low cost. The magnetite concentrate powder produced from siderite-rich powder has a large specific surface area and good pelletizing properties, which can reduce the dosage of additives for enhancing pelletizing effect during the pelletizing process. The price of siderite-rich powder is the lowest among all iron ore powders. The present invention uses siderite-rich powder to produce magnetite concentrate powder by grinding, which not only reduces the costs of sintered ore and pellet ore, but also, due to the large specific surface area and good pelletizing effect of the magnetite concentrate powder produced from siderite, is more suitable for the sintering and pelletizing production processes, can reduce the production costs of sintered ore and pellet ore, improve productivity, and reduce comprehensive energy consumption.

[0018] In the present invention, magnetite concentrate powder is produced by dry grinding of siderite. During the grinding process, siderite undergoes thermal decomposition and oxidation to form magnetite, obtaining concentrate powder with a large specific surface area and good pelletizing effect, which can improve the productivity of the sintering and pelletizing processes, reduce emissions, and reduce the cost per ton of iron.

[0019] This application can reduce the comprehensive iron material cost before ironmaking, utilize the siderite resources that are not conducive to smelting, expand the range of iron raw materials for the pelletizing process, make the pelletizing production raw materials have a wider range, and reduce the dependence on foreign iron ore resources. The present invention can be applied to all iron and steel enterprises that use concentrate powder as raw materials for the sintering and pelletizing processes.

[0020] In the present invention, heat exchange and cooling are carried out in two stages by two heat exchangers, and the waste heat of the hot exhaust gas is utilized to heat the combustion-supporting air of the flue gas furnace, saving energy.

[0021] Through two-stage capture, one is a gravity dust collector and the other is a bag dust collector. The function of the gravity dust collector is to remove large particles of the product to reduce the working load of the dust collector, and the dust collector captures fine particles, so that the emission ≤ 10mg / m 3 , achieving the purpose of qualified emission. Description of the Drawings

[0022] Figure 1 It is a process flow diagram for the present invention to produce magnetite concentrate powder using siderite-rich powder in an embodiment. Detailed implementation mode

[0023] The present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the scope of protection of the present invention. Embodiment 1

[0024] A process for producing magnetite concentrate from siderite rich powder provided in this embodiment has a process flow as Figure 1 shown. The corresponding equipment used in this process includes a storage bin, a vibrating feeder, a dry grinding mill, a gravity dust collector, a primary heat exchanger, a bag filter, a secondary heat exchanger, a variable frequency circulating fan, and a reflux baffle door, which are connected in sequence. The dry grinding mill is externally connected to a flue gas main pipe and a flue gas furnace in sequence. The reflux baffle door is connected to the flue gas main pipe through a pipeline. The inlet end of the secondary heat exchanger is externally connected to cold air, and the outlet end of the secondary heat exchanger is connected in series with the primary heat exchanger through a pipeline. The outlet end of the primary heat exchanger is connected to the inlet end of the flue gas furnace through a pipeline. The inlet end of the flue gas furnace is also externally connected to blast furnace gas, and the outlet end of the flue gas furnace is communicated with the flue gas main pipe; The gravity dust collector and the bag dust collector store the captured minerals in the storage bin through pipelines and the existing pneumatic conveying system respectively; The above process specifically includes the following steps: (1) The raw material siderite with a moisture content ≤ 9% is fed into the dry vertical grinding mill from the limonite storage bin through a variable frequency vibrating feeder to adjust the flow rate; (2) The mineral particles generated by grinding are heated and separated using circulating flue gas, and then captured by a gravity dust collector and a bag dust collector; (3) The dust-containing flue gas first removes ≥ 70% of the mineral particles through a gravity dust collector, which means capturing 70% of the weight of the generated minerals, and then exchanges heat through a primary tube heat exchanger to reduce the flue gas temperature ≤ 350 °C. Then, it is dusted by a bag filter, and the dust content of the flue gas after dust removal is ≤ 10 mg / m 3 , and the flue gas after dust removal exchanges heat again through a secondary tube heat exchanger, and the temperature of the flue gas after heat exchange is ≤ 150 °C; The heat exchange adopts air series heat exchange. The cold air is introduced by the secondary tube heat exchanger, passes through the primary tube heat exchanger, and finally enters the flue gas furnace. The heated air after heat exchange is used for combustion support of the flue gas furnace. The fuel of the flue gas furnace uses blast furnace gas; (4) The flue gas after heat exchange in step (3) enters the adjustable reflux baffle door through a variable-frequency circulation fan. Part of the flue gas is directly discharged, and the remaining part is transported by the reflux baffle door to the main pipe of the flue gas inlet of the dry vertical grinding mill, where it is mixed with the high-temperature flue gas of the flue gas furnace. The temperature of the mixed flue gas is: 550°C ≤ flue gas temperature ≤ 650°C. The mixed high-temperature flue gas enters the dry vertical grinding mill and is used to heat and separate siderite. During the heating process, siderite decomposes to obtain magnetite concentrate powder. The particle size requirement of the magnetite concentrate powder is: the particle size of -0.074mm particle size grade ≥ 80%. In this embodiment, the flue gas volume generated by the flue gas furnace is adjusted by a fuel regulating valve installed on the flue gas furnace. The fuel and air consumption are set according to the required air-fuel ratio. The total flue gas volume required by the dry vertical grinding mill = the flue gas volume generated by the flue gas furnace + the reflux flue gas volume; the connection and transportation between each device are selected from existing pumps, fans, etc. as needed to ensure the normal operation of the work.

[0025] In this embodiment, the particle size control of the product magnetite dust is controlled by the high-temperature flue gas flow rate. According to the formula in the prior art: critical wind speed V ∝ k • (d • ρ) -2 (k is the correction coefficient for the target iron concentrate particle size corresponding to air separation, d is the particle diameter, and ρ is the particle density), and the high-temperature flue gas flow rate is adjusted by a variable-frequency circulation fan using prior art means.

[0026] The present invention solves the problem that domestic siderite is applied in the iron and steel industry, expands the range of iron raw materials for the sintering and pelletizing processes, reduces the production costs of sintered ore and pelletized ore, improves productivity, and reduces comprehensive energy consumption.

[0027] In addition to the above embodiments, the present invention may also have other embodiments. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A process for producing magnetite concentrate from siderite-rich powder, characterized in that, Specifically, it includes the following steps: (1) Adjust the flow rate of the raw material siderite through a variable-frequency vibrating feeder and feed it into a dry vertical grinding mill; (2) Heat and separate the mineral particles generated by grinding using recycled flue gas; (3) The dust-containing flue gas is first passed through a gravity dust collector to remove ≥70% of the mineral particles, then heat-exchanged by a primary heat exchanger to reduce the flue gas temperature ≤350°C, and then dusted by a bag dust collector. After dust removal, the flue gas is heat-exchanged again by a secondary heat exchanger, and the temperature of the heat-exchanged flue gas ≤150°C; (4) The flue gas after heat exchange in step (3) enters an adjustable reflux baffle door through a variable-frequency circulation fan. Part of the flue gas is directly discharged, and the remaining part is transported by the reflux baffle door to the main pipe at the flue gas inlet of the dry vertical grinding mill. It is mixed with the high-temperature flue gas of the flue gas furnace at the main pipe at the flue gas inlet of the dry vertical grinding mill. After mixing, the high-temperature flue gas enters the dry vertical grinding mill and is used to heat and separate the siderite. During the heating process, the siderite decomposes to obtain magnetite concentrate powder.

2. The process for producing magnetite concentrate from siderite rich powder according to claim 1, characterized in that: In step (1), the moisture content of the raw material siderite ≤9%.

3. The process for producing magnetite concentrate from siderite rich powder according to claim 1, characterized in that: In step (2), the flue gas is the high-temperature flue gas after mixing in step (3), and the flue gas temperature is 550°C ≤ flue gas temperature ≤ 650°C.

4. The process for producing magnetite concentrate from siderite rich powder according to claim 1, characterized in that: In step (3), after passing through the gravity dust collector, the dust-containing flue gas removes ≥70% of the mineral particles.

5. The process for producing magnetite concentrate from siderite-rich powder according to claim 1, wherein: After passing through the bag dust collector in step (3), the dust content in the flue gas ≤ 10 mg / m 3 .

6. The process for producing magnetite concentrate from siderite rich powder according to claim 1, characterized in that: In step (3), the heat exchange is all carried out by air in series. The cold air is connected through the secondary heat exchanger, passes through the primary heat exchanger, and finally enters the flue gas furnace. The heat-exchanged hot air is used for combustion support of the flue gas furnace; the fuel of the flue gas furnace uses blast furnace gas.

7. The process for producing magnetite concentrate from siderite rich powder according to claim 1, characterized in that: The particle size requirement of the obtained magnetite concentrate powder: the particle size of -0.074mm grade ≥80%.

8. An apparatus for producing magnetite concentrate using siderite rich powder, characterized in that: It includes a storage bin, a vibrating feeder, a dry grinding mill, a gravity dust collector, a primary heat exchanger, a bag dust collector, a secondary heat exchanger, a variable-frequency circulation fan, and a reflux baffle door connected in sequence. The dry grinding mill is externally connected to a flue gas main pipe and a flue gas furnace in sequence. The reflux baffle door is connected to the flue gas main pipe through a pipeline. The inlet end of the secondary heat exchanger is externally connected to cold air, and the outlet end of the secondary heat exchanger is connected in series with the primary heat exchanger through a pipeline. The outlet end of the primary heat exchanger is connected to the inlet end of the flue gas furnace through a pipeline. The inlet end of the flue gas furnace is also externally connected to blast furnace gas, and the outlet end of the flue gas furnace is communicated with the flue gas main pipe.

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