CN111763820B - Slag modified reducing agent, preparation method thereof and method for recycling iron by using slag waste heat - Google Patents
Slag modified reducing agent, preparation method thereof and method for recycling iron by using slag waste heat Download PDFInfo
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- CN111763820B CN111763820B CN202010499488.2A CN202010499488A CN111763820B CN 111763820 B CN111763820 B CN 111763820B CN 202010499488 A CN202010499488 A CN 202010499488A CN 111763820 B CN111763820 B CN 111763820B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/005—Preliminary treatment of scrap
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0066—Preliminary conditioning of the solid carbonaceous reductant
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/008—Use of special additives or fluxing agents
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B3/00—General features in the manufacture of pig-iron
- C21B3/02—General features in the manufacture of pig-iron by applying additives, e.g. fluxing agents
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/10—Dry methods smelting of sulfides or formation of mattes by solid carbonaceous reducing agents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
The invention discloses a slag modified reducing agent which is spherical particles with the particle size of 10-30mm and comprises 100 parts by weight of flux, 5-24 parts by weight of reducing agent, 8-18 parts by weight of binder and 0-10 parts by weight of fluxing agent. The invention also discloses a method for recycling iron by using the slag waste heat, which comprises the following steps: a, in the process of discharging molten slag from a smelting furnace and pouring the molten slag into a heat-preservation container, adding a molten slag modification reducing agent into molten slag flow to perform modification reduction reaction; b, after the molten slag and the modified reducing agent react, crushing the solid slag in the heat-preservation container, and magnetically separating to obtain metal iron particles and/or iron concentrate powder. The method of the invention aims at a large amount of residual heat and residual iron resources contained in the slag, directly carries out high-temperature residual heat modification on the slag, adjusts the chemical components and melting temperature of the slag, reduces the reduction potential energy of iron oxide, and realizes the high-efficiency recovery of iron in the slag by a medium-low temperature roasting technology and a grinding and selecting technology.
Description
Technical Field
The invention belongs to the technical field of non-ferrous metal smelting, and particularly relates to a slag modified reducing agent and a preparation method thereof, in particular to a method for recycling iron by using slag waste heat.
Background
Copper slag and nickel slag (hereinafter referred to as copper-nickel slag) are solid waste slag generated in the process of smelting copper and nickel by a pyrogenic process, and belong to non-ferrous metal smelting waste slag. Because most of the copper and nickel smelting technical processes are similar to smelting slag shapes, the chemical components and slag phase compositions of the solid copper slag and the nickel slag are similar, for example, the contents of Fe and Si are high, the content of Ca is low, and the solid slag mineral phases belong to fayalite, the copper slag and the nickel slag can be collectively called iron-containing acid slag or fayalite type slag.
The method has incomplete estimation, the yield of copper slag is 1800 million tons per year, the yield of nickel slag is 400 million tons per year, and the accumulated stockpiling is nearly 2 hundred million tons till now. The waste residues not only occupy a large amount of land, but also cause environmental problems such as dust flying, heavy metal seepage, underground water pollution, land dilution and the like, and bring serious harm to human survival and social development. In China, due to the reasons that the importance degree of recycling copper-nickel slag is not enough and related process technologies are not mature, the high-efficiency comprehensive utilization of the copper-nickel slag is not realized in large-scale application, a large amount of copper-nickel slag is still directly piled up in a slag warehouse and cannot be effectively utilized for a long time, valuable metal elements in the slag are lost, the temperature of the copper-nickel slag after the copper-nickel slag is discharged from a furnace is high, the waste heat is rich, but the waste heat is not efficiently utilized, and the serious waste of resources is caused.
In the prior art, a plurality of problems exist in the extraction of iron in copper slag and nickel slag and the recovery of residual heat of molten slag, the recovery rate of iron is low, the process economy is poor, and the residual heat cannot be effectively utilized, so that the problems of the residual heat utilization of the copper-nickel slag and the recovery of iron in the copper-nickel slag are urgently needed to be solved.
Disclosure of Invention
The present application is based on the discovery and recognition by the inventors of the following facts and problems:
for most of copper-nickel slag, the content of total iron (TFe) is generally 30-40%, which is far higher than the recoverable grade of iron ore (TFe > 27%) in China, so the utilization research of copper-nickel slag is mainly to recover residual iron in slag at present. However, in these copper-nickel slags, iron mainly exists in the form of mineral phases such as fayalite and FeO, and these mineral phases are tightly embedded with other non-magnetic mineral phases, or are dissolved in the non-magnetic glass phase of the slag by water quenching process during discharge, or have the characteristic of weak magnetism, such as fayalite, so that it is difficult to recover iron from the slag with high efficiency by directly passing through the grinding and separation process, and the recovery rate of iron is low, and the process economy is not good. Therefore, in many related researches, the solid slag is mostly prepared into metallized pellets or briquettes by adding various additives and adopting a high-temperature reduction process, and then is subjected to a grinding and selecting process to obtain metallic iron or iron concentrate powder, so that the iron resource recovery is realized. However, the method needs to crush the solid slag, and a large amount of cold raw and auxiliary materials are also added, so that the cold material treatment capacity is large, and the energy consumption of a unit product is high.
The tapping temperature of the copper-nickel smelting slag is usually 1150-1400 ℃, the specific heat capacity is about 0.9-1.2 kJ/kg-DEG C, the total heat of each ton of slag is equivalent to 50kg of standard coal (7000 Kcal/kg), and the waste heat resources are more. However, under the influence of the factors such as low thermal conductivity, high viscosity and low heat conversion efficiency of the molten slag, the existing residual heat of the molten slag cannot be efficiently and economically utilized, so that the molten slag is directly quenched by water, and the waste of the residual heat is serious.
Patent CN101921919B discloses a comprehensive utilization process of molten copper slag and a system thereof. According to the patent, molten copper slag discharged from a furnace is directly loaded into a copper extracting furnace, and inert gas is blown into the copper extracting furnace for stirring after reducing agents I and CaO are added. After the copper water is reduced, the copper water is collected, the residual slag is sent into a copper-iron extracting furnace, then reducing agent II steam is sent into the furnace through a spray gun, then oxygen is blown into the slag in the furnace from the bottom of the furnace, and the slag in the furnace can be reduced to obtain copper-iron alloy. In the technique described in this patent, the stirring of the slag is achieved by pressurizing inert gas or oxygen, but this generates a large amount of hot flue gases and carries away a large amount of heat. The blowing action of the gas on the slag can also bring the reducing agent and CaO added into the furnace into the flue gas, so that the loss rate of the raw materials is high. Oxygen is blown into the slag from the furnace bottom in the reduction process, so that the oxygen content in the copper slag and the oxygen potential of the slag can be increased, the reduction process of iron oxides in the slag is not facilitated, and the combustion of a reducing agent is increased.
Patent CN101736112B discloses a method for extracting iron from copper slag by smelting reduction using inert gas blowing. According to the method, discharged high-temperature copper slag is directly poured into a high-temperature reduction furnace, then a reducing agent and a slagging agent are directly added into the furnace for reduction ironmaking, the temperature of the reaction furnace is 1540-and 1700 ℃, the reaction time is 1-10h, and inert gas is blown into a molten pool in the reaction process to stir the molten slag. In the technology disclosed in the patent, a reducing agent and a slagging agent are directly added into high-temperature copper slag, because the wettability of the reducing agent and the slag is poor, the reducing agent is difficult to melt into the slag, a solid reducing agent floats on the surface of the slag after contacting the slag, and a liquid or gas reducing agent is directly gasified after contacting the high-temperature slag and is discharged along with flue gas or burnt, so that the utilization efficiency of the raw material of the reducing agent is low. In the reaction process, a large amount of heat can be taken away by using a gas stirring measure, and the burden of a dust removal system can be increased by adding powder. In addition, the reaction furnace has a high temperature and a long reaction time, which increases energy consumption and inhibits the improvement of productivity.
Patent CN103614607B discloses a method for preparing stainless steel raw material by melting and reducing hot copper slag under the action of nickel-containing material. Directly charging high-temperature molten copper slag discharged from a copper smelting furnace into a metallurgical furnace, and reducing molten iron containing nickel and copper under the action of adding a reducing agent, a slagging agent and a nickel-containing material into the furnace to be used as a raw material for smelting stainless steel. In the technology disclosed in the patent, the reduction reaction belongs to a high-temperature melting reduction technology, the reaction temperature is high, the slag quantity is large, and the unit iron energy consumption is increased. The reducing agent is added in a mode of being sprayed into slag in the furnace by gas carrying, and is easily carried away by high-temperature high-speed flue gas. The slag former and the reducing agent are added into the slag at the same time, and because the iron oxide is reduced, the melting temperature and viscosity of the slag are correspondingly improved, thereby further influencing the melting-in of the slag former and the slag reduction effect.
Therefore, although some methods for utilizing metal smelting slag are provided in the related art, the problems of low waste heat utilization rate and high unit energy consumption exist.
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, one purpose of the embodiment of the invention is to provide a slag modified reducing agent, and the appropriate raw material proportion of the slag modified reducing agent is designed, so that the deep and efficient recovery of residual iron in slag is realized, and the unit energy consumption of products is reduced.
To this end, an embodiment of the first aspect of the present invention provides a slag-modifying reducing agent, which is spherical particles having a particle size of 10 to 30mm, comprising 100 parts by weight of a flux, 5 to 24 parts by weight of a reducing agent, 8 to 18 parts by weight of a binder, and 0 to 10 parts by weight of a flux, wherein the flux is selected from at least one of limestone, dolomite, quicklime, or slaked lime; the reducing agent is at least one of anthracite powder, coke powder, blue carbon powder or reducing coal; the binder is at least one of clay, cement, sodium silicate, resin or water; the fluxing agent is at least one of industrial soda ash, fluorite or iron ore powder.
The slag modification reducing agent of the embodiment of the invention has the beneficial effects that a large amount of flux is added in the proportion of the modification reducing agent, the flux and the slag carry out chemical reaction, the chemical components and the mineral phase structure of the slag are changed, and CaO/SiO in the slag is enabled to be 2 Gradually increasing to 0.7-1.0, further reducing the melting point and viscosity of the slag, increasing the reduction performance of the iron oxide, carrying out reduction reaction on the reducing agent in the modified reducing agent and the iron oxide in the modified slag, reducing the iron oxide in the slag to form metal Fe particles or low-valence iron-rich oxide, and improving the recovery rate of iron.
The slag-modifying reducing agent is spherical particles with a core-shell structure, the particle size of the spherical particles is 15-25mm, the particle size of the inner core is 5-10mm, the inner core comprises 5-24 parts by weight of reducing agent, 6-12 parts by weight of binder and 0-3 parts by weight of activator, the activator is at least one of industrial soda ash, sodium chloride, potassium carbonate or fluorite, the outer part of the inner core is coated with a shell, and the shell comprises 100 parts by weight of flux, 2-6 parts by weight of binder and 0-10 parts by weight of fluxing agent.
The embodiment of the second aspect of the invention provides a preparation method of a slag modified reducing agent, 100 parts by weight of flux, 5-24 parts by weight of reducing agent, 8-18 parts by weight of binder and 0-10 parts by weight of fluxing agent in the slag modified reducing agent provided by the embodiment of the first aspect of the invention are uniformly mixed, ground and prepared into powder, and then granulated to obtain the spherical particle modified reducing agent with the particle size of 10-30 mm.
The preparation method of the slag modified reducing agent according to the embodiment of the second aspect of the invention comprises the following steps: a. respectively grinding 5-24 parts by weight of reducing agent, 6-12 parts by weight of binder and 0-3 parts by weight of activating agent into powder, uniformly mixing, and carrying out primary granulation to obtain particles with the particle size of 5-10mm, wherein the activating agent is selected from at least one of industrial soda ash, sodium chloride, potassium carbonate or fluorite; b. uniformly mixing 100 parts by weight of flux, 2-6 parts by weight of binder and 0-10 parts by weight of flux, and grinding into powder; c. and (b) adding the material particles obtained in the step (a) into a granulator to serve as an inner core of a slag modification reducing agent, coating the powder obtained in the step (b) on the inner core, and carrying out secondary granulation to obtain spherical particles with a core-shell structure and the particle size of 15-25 mm.
According to the preparation method of the slag modified reducing agent, the granulation mode is rotary disc granulation or extrusion granulation.
The embodiment of the invention also aims to provide a method for recycling iron by using the slag waste heat, which directly modifies the slag by using high-temperature waste heat, adjusts the chemical components and melting temperature of the slag, reduces the reduction potential energy of iron oxide, realizes the high-efficiency recycling of iron in the slag by using a medium-low temperature roasting technology and a grinding and selecting technology and reduces the new input energy aiming at a large amount of waste heat and residual iron resources contained in the slag.
The embodiment of the third aspect of the invention also provides a method for recovering iron by using the slag waste heat, which comprises the following steps: a. in the process of discharging the slag from the smelting furnace and pouring the slag into the heat-preserving container, adding the slag modification reducing agent in the first aspect of the embodiment of the invention into the slag flow to carry out modification reduction reaction; b. and c, after the molten slag and the modified reducing agent are reacted in the step a, crushing the solid slag in the heat-preservation container, and performing magnetic separation to obtain metal iron particles and/or iron concentrate powder. The heat-insulating container in the embodiment of the invention can adopt a special container with a heat-insulating cover or similar heat-insulating measures, such as a slag ladle, a slag pot, a hot smoldering slag pit and the like.
The method for recycling iron by using the slag waste heat has the beneficial effects that: the slag and the modified reducing agent are directly subjected to modification reaction at high temperature by directly utilizing the high-temperature residual heat of the slag, secondary heating is not needed in the modification process, the modified reducing agent is continuously added into the slag flow in the process of discharging the slag from the smelting furnace, and the modified reducing agent is subjected to high-impulse stirring by means of the impact force of the slag flow, so that the rapid reaction of the slag and the modified reducing agent is promoted. A large amount of flux in the slag modified reducing agent is melted into slag under the action of waste heat, crystal structures such as fayalite in the slag are damaged, mechanical processing performances such as breaking easiness and grindability of modified solid slag are improved, processing energy consumption is reduced, iron in the modified reducing slag is fully recovered through a crushing magnetic separation process, the iron recovery rate is improved, the waste heat utilization rate of the slag is high, investment is low, economy is good, energy consumption is low, new water consumption is low, full-component utilization of waste slag can be achieved, and the potential value is high.
According to the third aspect of the embodiment of the invention, the method for recycling iron by using the slag waste heat further comprises a step c of adding a flux, a reducing agent and a binder into the tailings which are not subjected to magnetic separation in the step b, uniformly mixing, grinding and granulating to obtain particles with the particle size of 15-30mm, feeding the particles into a roasting reduction furnace at the roasting temperature of 1200-1400 ℃ to obtain metallized pellets, crushing, and performing magnetic separation to obtain metal iron particles and/or iron concentrate powder.
According to the method for recovering iron by using the residual heat of the slag, the modification reducing agent added in the step a accounts for 14-50% of the total mass of the slag.
According to the method for recovering iron by using the residual heat of the slag, the heat preservation container in the step a is connected with a flue gas recovery device and is used for recovering valuable metals in the flue gas.
According to the method for recovering iron by using the slag afterheat of the third aspect of the invention, the mass ratio of the tailings, the fluxing agent, the reducing agent and the binding agent in the step c is 100:5-22:8-20:4-16, wherein the fluxing agent is selected from at least one of limestone, dolomite, quicklime or hydrated lime; the reducing agent is at least one of anthracite powder, coke powder, blue carbon powder or reducing coal; the binder is at least one selected from clay, cement, sodium silicate, resin or water.
Drawings
FIG. 1 is a process flow diagram of iron recovery from residual heat of slag according to one embodiment of the present invention;
fig. 2 is a process flow diagram for iron recovery from residual heat of slag according to another embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the invention is intended to be illustrative, and is not to be construed as limiting the invention.
A slag-modifying reducing agent according to an embodiment of the first aspect of the present invention, which is a spherical particle having a particle diameter of 10 to 30mm, comprises 100 parts by weight of a flux selected from at least one of limestone, dolomite, quicklime or slaked lime, 5 to 24 parts by weight of a reducing agent, 8 to 18 parts by weight of a binder and 0 to 10 parts by weight of a flux; the reducing agent is at least one of anthracite powder, coke powder, blue carbon powder or reducing coal; the binder is at least one of clay, cement, sodium silicate, resin or water; the fluxing agent is at least one of industrial soda ash, fluorite or iron ore powder. In the slag modified reducing agent of the embodiment of the invention, a large amount of flux is added, and the flux is used for mixing with SiO in the slag 2 Reacting to reduce the chemical bonding force with FeO, wherein the chemical reaction formula is as follows: CaO +2FeO SiO 2 ＝2FeO+CaO·SiO 2 The chemical composition and the mineral phase structure of the slag are changed, so that CaO/SiO in the slag is changed 2 Gradually increasing to 0.7-1.0, further reducing the melting point and viscosity of the slag, increasing the reduction performance of iron oxide, reducing the melting point of the flux by the aid of the flux, promoting the flux to quickly react with the slag to form modified slag, wherein the reducing agent mainly comprises solid powdery raw materials with high C content and low volatile substances and is used for promoting the reduction reaction of iron oxide in the slag, and reducing the reducing agent in the reducing agent and the iron oxide in the modified slag to reduce the iron oxide in the slag to form metal Fe particles or low-valence iron-rich oxide, so that the recovery rate of iron is improved.
The slag-modifying reducing agent is spherical particles with a core-shell structure, the particle size of the spherical particles is 15-25mm, the particle size of the inner core is 5-10mm, the inner core comprises 5-24 parts by weight of reducing agent, 6-12 parts by weight of binder and 0-3 parts by weight of activator, the activator is at least one of industrial soda ash, sodium chloride, potassium carbonate or fluorite, the outer part of the inner core is coated with a shell, and the shell comprises 100 parts by weight of flux, 2-6 parts by weight of binder and 0-10 parts by weight of fluxing agent. The slag modified reducing agent adopts a core-shell structure, the reducing agent, the active agent and the binder are used as an inner core, the outer part of the core is coated with the flux, the fluxing agent and the binder and used as a shell, when the modified reducing agent in the embodiments is added into the slag, the outer layer flux of the modified reducing agent is firstly subjected to chemical reaction with the slag, the chemical composition of the slag is adjusted, the melting point is reduced, the metallurgical performance is improved, then the modified reducing agent is subjected to reaction with the reducing agent in the inner core, the iron oxide is reduced into metallic iron or magnetic oxide, the active agent added into the inner core is mainly composed of active metal oxides and used for increasing the reducing activity of the reducing agent and promoting the iron oxide to be rapidly reduced.
According to the preparation method of the slag modified reducing agent, 100 parts by weight of the flux, 5-24 parts by weight of the reducing agent, 8-18 parts by weight of the binder and 0-10 parts by weight of the flux are uniformly mixed, ground and granulated to obtain the spherical particle modified reducing agent with the particle size of 10-30 mm. The granulation mode is rotary disk granulation or extrusion granulation. The preparation method of the slag modified reducing agent provided by the embodiment of the invention is simple and feasible, and the prepared slag modified reducing agent can change the chemical components and the mineral phase structure of the slag when reacting with the slag, destroy the crystal structures of fayalite and the like in the slag, improve the mechanical treatment performances of the modified solid slag, such as the breaking easiness, the grinding easiness and the like, and reduce the treatment energy consumption.
The preparation method of the slag modified reducing agent according to the embodiment of the second aspect of the invention comprises the following steps: a. respectively grinding 5-24 parts by weight of a reducing agent, 6-12 parts by weight of a binder and 0-3 parts by weight of an activating agent into powder, uniformly mixing, and carrying out primary granulation to obtain particles with the particle size of 5-10mm, wherein the activating agent is selected from at least one of industrial sodium carbonate, sodium chloride, potassium carbonate or fluorite; b. uniformly mixing 100 parts by weight of flux, 2-6 parts by weight of binder and 0-10 parts by weight of flux, and grinding into powder; c. and (c) adding the material particles obtained in the step (a) into a granulator to serve as an inner core of a slag modification reducing agent, coating the powder obtained in the step (b) on the inner core, and performing secondary granulation to obtain spherical particles with a core-shell structure and the particle size of 15-25 mm. In the method of the embodiment of the invention, a twice granulation mode is adopted, and the modified reducing agent is prepared into spherical particles with a nuclear shell structure, so that the outer layer flux of the modified reducing agent and the slag are subjected to chemical reaction, the chemical composition of the slag is adjusted, the melting point is reduced, the metallurgical performance is improved, and then the modified reducing agent reacts with the reducing agent in the modified reducing agent to reduce the iron oxide into metallic iron or magnetic oxide.
According to the third aspect of the invention, the method for recovering iron by using the residual heat of the slag comprises the following steps: a. in the process of discharging the slag from the smelting furnace and pouring the slag into the heat preservation container, adding the slag modification reducing agent in the first aspect of the invention into the slag flow to carry out modification reduction reaction; b. and c, after the molten slag and the modified reducing agent are reacted in the step a, crushing the solid slag in the heat-preservation container, and performing magnetic separation to obtain metal iron particles and/or iron concentrate powder. The heat-insulating container in the embodiment of the invention can adopt a special container with a heat-insulating cover or similar heat-insulating measures, such as a slag ladle, a slag pot, a hot smoldering slag pit and the like. According to the method for recycling iron by using the slag waste heat, provided by the embodiment of the invention, the slag and the modified reducing agent are directly subjected to modification reaction at high temperature by directly using the high-temperature slag waste heat, secondary heating is not required in the modification process, the modified reducing agent is continuously added into the slag flow in the process of discharging the slag from the smelting furnace, and the high-impulse stirring is carried out on the modified reducing agent by means of the slag flow impact force, so that the rapid reaction of the slag and the modified reducing agent is promoted. A large amount of flux in the slag modified reducing agent is melted into slag under the action of waste heat, crystal structures such as fayalite in the slag are damaged, mechanical processing performances such as breaking easiness and grindability of modified solid slag are improved, processing energy consumption is reduced, iron in the modified reducing slag is fully recovered through a crushing magnetic separation process, the iron recovery rate is improved, the waste heat utilization rate of the slag is high, investment is low, economy is good, energy consumption is low, new water consumption is low, full-component utilization of waste slag can be achieved, and the potential value is high.
According to the third aspect of the embodiment of the invention, the method for recycling iron by using the slag waste heat further comprises a step c of adding a flux, a reducing agent and a binder into the tailings which are not subjected to magnetic separation in the step b, uniformly mixing, grinding and granulating to obtain particles with the particle size of 15-30mm, feeding the particles into a roasting reduction furnace at the roasting temperature of 1200-1400 ℃ to obtain metallized pellets, crushing, and performing magnetic separation to obtain metal iron particles and/or iron concentrate powder. In the method of the embodiment of the invention, low-iron tailings which are subjected to modification reduction and crushing, separating and grinding are subjected to deep reduction by adopting medium-low temperature roasting reduction, nonmagnetic iron in the tailings is fully converted into metallic iron or magnetic iron powder, and iron elements are recovered.
According to the method for recovering iron by using the residual heat of the slag, the added modified reducing agent in the step a accounts for 14-50% of the total mass of the slag. In the method of the embodiment of the invention, because the residual heat of the slag is limited, a proper amount of modified reducing agent needs to be added into the slag to ensure sufficient slag heat and stirring impact force in the heat-insulating container.
According to the method for recovering iron by using the slag afterheat of the third aspect of the invention, the heat-preserving container of the step a is connected with a flue gas recovery device and is used for recovering valuable metals in the flue gas. In the method of the embodiment of the invention, the flue gas can be recovered, the obtained smoke dust contains volatile metals such as lead, zinc and the like, and the smoke dust can be recovered by other processes.
According to the third aspect of the invention, the mass ratio of the tailings, the fluxing agent, the reducing agent and the binder in the step c is 100:5-22:8-20:4-16, wherein the fluxing agent is at least one of limestone, dolomite, quicklime or hydrated lime; the reducing agent is at least one of anthracite powder, coke powder, blue carbon powder or reducing coal; the binder is at least one selected from clay, cement, sodium silicate, resin or water. In the method of the embodiment of the invention, the tailings, the flux, the reducing agent and the binder are roasted and reduced in a proper proportion to recover iron in the tailings.
The method for recovering iron by using the residual heat of slag according to the embodiment of the present invention will be described with reference to fig. 1.
Example 1
Preparation of slag modified reducing agent
Uniformly mixing 100 parts by weight of quicklime, 6 parts by weight of anthracite powder, 10 parts by weight of cement and 3 parts by weight of fluorite, and performing ball milling until the particle size is less than 0.1mm to obtain modified reducing agent powder. Then, pelletizing is carried out in a disc pelletizer, and a small amount of water can be added during pelletizing to promote the pelletizing nucleation process. Discharging the pellets onto a conveyer belt after the granularity of the pellets reaches 15-25 mm. And conveying the modified reducing agent spherulites on the conveying belt to a curing bin, introducing water vapor into the bin to promote the mechanical strength of the modified reducing agent spherulites to be rapidly increased, and curing to obtain the slag modified reducing agent used for production.
Second, method for recovering iron by using residual heat of slag
In the process of pouring molten copper slag discharged from a copper smelting furnace at the temperature of 1320-1350 ℃ into a slag ladle, the molten slag modified reducing agent prepared in the embodiment is added into the slag ladle, the weight of the copper slag in the ladle is about 20 tons, and the adding amount of the molten slag modified reducing agent is 4 tons. After the feeding is stopped, the heat-preserving cover is covered to carry out the modification reduction reaction for about 1 hour, and the smoke generated by the reaction is pumped out from the smoke vent on the cover. The extracted flue gas can be sent into a flue gas recovery device to recover valuable metals in the flue gas, and the flue gas contains volatile metals such as lead, zinc and the like, and the flue gas can be recovered by other processes.
After the reaction is finished, pouring out the copper slag in the slag ladle, carrying out mechanical crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron concentrate powder, analyzing that the iron recovery rate can reach 50 percent, the waste heat utilization rate can reach 85 percent, and the obtained metal iron particles and iron concentrate powder can be returned to an iron and steel plant for smelting.
The residual low-iron tailings which are not magnetically separated are mixed with the lime hydrate, the anthracite powder and the cement according to the mass ratio as tailings: quick lime: anthracite coal powder: 100 parts of cement: 15: 8: 15, uniformly mixing, grinding and granulating to obtain reduced material particles with the particle size of 20-25 mm. Then the reducing material particles are sent into a rotary kiln for reduction roasting, the temperature in the rotary kiln is 1220-1320 ℃, and the roasting time is 1.5 h. After the roasting and sintering, discharging from the rotary kiln, and performing crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron concentrate powder, which can be returned to an iron and steel plant for smelting. And the residual tailings can be used as artificial broken stones for external building material enterprises with the granularity of more than 5mm, and can be used as artificial sand with the granularity of less than 5mm for manufacturing building materials.
Example 2
Uniformly mixing 100 parts by weight of limestone, 21 parts by weight of coke powder, 16 parts by weight of clay powder and 8 parts by weight of fluorite, and performing ball milling until the particle size is less than 0.1mm to obtain modified reducing agent powder. Then, adding a small amount of water into the modified reducing agent powder, stirring the modified reducing agent powder into a semi-wet material, and pelletizing the semi-wet material in a pelletizer, wherein the particle size of the pellets is 25 mm. And discharging the manufactured spherulites onto a conveying belt, conveying the spherulites to a curing bin, introducing air into the curing bin to promote the mechanical strength of the modified reducing agent spherulites to be rapidly increased, and curing to obtain the slag modified reducing agent for production.
Second, method for recovering iron by using residual heat of slag
In the process of pouring molten nickel slag discharged from a nickel smelting furnace at the temperature of 1350-1420 ℃ into a hot slag disintegrating pit, adding the slag modified reducing agent prepared by the embodiment into the molten nickel slag, wherein the weight of the nickel slag in the hot slag disintegrating pit is 60t, and the adding amount of the slag modified reducing agent is 18 t. After the feeding is stopped, covering a heat-insulating cover for carrying out modification reduction reaction for about 2 hours, and pumping out smoke generated by the reaction from a smoke vent on the cover. The extracted flue gas can be sent into a flue gas recovery device to recover valuable metals in the flue gas, and the flue gas contains volatile metals such as lead, zinc and the like, and the flue gas can be recovered by other processes.
After the reaction is finished, the nickel slag in the hot slag-tight pit is poured out, and is subjected to mechanical crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron concentrate powder, the iron recovery can reach 60% through analysis, the waste heat utilization rate can reach 78%, and the obtained metal iron particles and iron concentrate powder can be returned to an iron and steel plant for smelting.
The residual low-iron tailings which are not magnetically separated are mixed with limestone, coke powder and clay powder according to the mass ratio as tailings: limestone: coke powder: clay powder 100: 22: 19: 5, uniformly mixing, grinding and granulating to obtain reducing material granules with the granularity of 30 mm. And then, conveying the reducing material particles into a rotary kiln for reducing roasting, wherein the temperature in the rotary kiln is 1250-. After the roasting and sintering, discharging from the rotary kiln, and performing crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron concentrate powder, which can be returned to an iron and steel plant for smelting. And the residual tailings can be used as artificial broken stones for external building material enterprises with the granularity of more than 5mm, and can be used as artificial sand with the granularity of less than 5mm for manufacturing building materials.
The method for recovering iron by using the residual heat of slag according to the embodiment of the present invention will be described with reference to fig. 2.
Example 3
Preparation of slag modified reducing agent
Respectively grinding 5 parts by weight of anthracite powder, 6 parts by weight of cement and 0.3 part by weight of industrial soda ash into powder with the particle size of less than 0.1mm, and uniformly mixing to obtain the reducing powder. Then, the mixture is granulated in a disc pelletizer for one time, and a small amount of water can be added during granulation to promote the granulation nucleation process. And when the grain size of the material grains is 5mm, screening out the material grains, and sending the material grains to a secondary granulation process.
Quicklime powder, fluorite powder and clay powder are respectively used as a flux, a fluxing agent and a binder, and after 100 parts by weight of quicklime powder, 8 parts by weight of fluorite powder and 2 parts by weight of clay powder are uniformly mixed, the mixture is ground until the particle size is less than 0.1mm, so that modified powder is obtained.
Adding the material granules produced by primary granulation into a secondary granulation disc granulator to serve as an inner core of a modified reducing agent, adding modified powder in the process of atomizing and spraying water to the secondary granulation disc granulator, wrapping the modified reducing agent inner core obtained by primary granulation until the granulation particle size is 15-25mm, discharging the modified reducing agent inner core onto a conveying belt, conveying the modified reducing agent inner core onto a maintenance bin, introducing water vapor into the maintenance bin to promote the mechanical strength of the modified material granules to be increased, and obtaining the slag modified reducing agent used for production after maintenance.
Second, method for recovering iron by using residual heat of slag
In the process of pouring molten copper slag discharged from a copper smelting furnace at the temperature of 1320-1350 ℃ into a slag ladle, the modified reducing agent prepared in the embodiment is added into the slag ladle, the weight of the copper slag in the ladle is 20 tons, and the adding amount of the modified reducing agent is 4 tons. After the feeding is stopped, covering a heat-insulating cover for carrying out modification reduction reaction for about 1h, and pumping out smoke generated by the reaction from a smoke vent on the cover. The extracted flue gas can be sent into a flue gas recovery device to recover valuable metals in the flue gas, and the flue gas contains volatile metals such as lead, zinc and the like, and the flue gas can be recovered by other processes.
After the reaction is finished, pouring out the copper slag in the slag ladle, carrying out mechanical crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron ore concentrate powder, analyzing that the iron recovery can reach 68 percent, the waste heat utilization rate can reach 90 percent, and the obtained metal iron particles and iron ore concentrate powder can be returned to an iron and steel plant for smelting.
The residual low-iron tailings which are not magnetically separated are mixed with limestone, coke powder, fluorite and cement according to the mass ratio as tailings: coke powder: clay powder 100: 5: 10: 8, uniformly mixing, grinding and granulating to obtain reduced material particles with the particle size of 15 mm. Then the reducing material particles are sent into a rotary kiln for reducing roasting, the temperature in the kiln is 1300-. After the roasting and sintering, discharging from the rotary kiln, and performing crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron concentrate powder, which can be returned to an iron and steel plant for smelting. And the residual tailings can be used as artificial broken stones for external building material enterprises with the granularity of more than 5mm, and can be used as artificial sand with the granularity of less than 5mm for manufacturing building materials.
Example 4
Respectively grinding 20 parts by weight of coke powder, 12 parts by weight of clay powder and 3 parts by weight of industrial potassium carbonate into powder with the particle size of less than 0.1mm, and uniformly mixing to obtain reducing powder. The reducing powder and water are mixed into plastic mud press, and then primary granulation is carried out, and the mud press is pressed into material particles with the particle size of 8mm in a ball press machine and sent to a secondary granulation process.
Limestone, industrial soda-iron ore powder and sodium silicate-quicklime powder are respectively used as a fusing agent, a fluxing agent and a binding agent, 100 parts by weight of limestone, 10 parts by weight of industrial soda-iron ore powder and 5 parts by weight of sodium silicate-quicklime powder are uniformly mixed, and then mixed and ground until the particle size is less than 0.1mm, so that modified powder is obtained.
Adding the material granules produced by the primary granulation process into a secondary granulation disc granulator to serve as modified reducing agent cores, adding modified powder in the process of atomizing and spraying water to the modified reducing agent cores, coating the modified reducing agent cores obtained by primary granulation until the granulation grain size is 15-25mm, discharging the modified reducing agent cores onto a conveying belt, conveying the modified reducing agent cores to a maintenance bin, introducing water vapor into the maintenance bin to promote the mechanical strength of the modified material granules to be increased, and obtaining the slag modified reducing agent used for production after maintenance.
Second, method for recovering iron by using residual heat of slag
In the process of pouring molten copper slag discharged from a nickel smelting furnace at the temperature of 1350-1420 ℃ into a slag ladle, the slag modified reducing agent prepared in the embodiment is added into the slag ladle, the weight of nickel slag in the ladle is 22 tons, and the adding amount of the slag modified reducing agent is 3.2 tons. After the feeding is stopped, covering a heat-insulating cover for carrying out modification reduction reaction for about 1h, and pumping out smoke generated by the reaction from a smoke vent on the cover. The extracted flue gas can be sent into a flue gas recovery device to recover valuable metals in the flue gas, and the flue gas contains volatile metals such as lead, zinc and the like, and the flue gas can be recovered by other processes.
After the reaction is finished, pouring out the copper slag in the slag ladle, carrying out mechanical crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron ore concentrate powder, analyzing that the iron recovery can reach 76 percent and the waste heat utilization rate can reach 86 percent, and returning the obtained metal iron particles and iron ore concentrate powder to an iron and steel plant for smelting.
The residual low-iron tailings which are not magnetically separated are mixed with the regenerated lime, the coke powder and the clay powder according to the mass ratio as tailings: quick lime: coke powder: clay powder 100: 22: 18: 16, uniformly mixing, grinding and granulating to obtain reduced material particles with the particle size of 20 mm. And then, conveying the reducing material particles into a rotary kiln for reducing roasting, wherein the temperature in the rotary kiln is 1250-. After the roasting and sintering, discharging from the rotary kiln, and performing crushing, screening, grinding and magnetic separation to obtain metal iron particles and iron concentrate powder, which can be returned to an iron and steel plant for smelting. And the residual tailings can be used as artificial broken stones for external building material enterprises with the granularity of more than 5mm, and can be used as artificial sand with the granularity of less than 5mm for manufacturing building materials.
Comparative example 1
Comparative example 1 is the same as the method for recycling iron by using slag waste heat in example 1, except that a slag modifying and reducing agent is added into a slag ladle, 100 parts by weight of quicklime, 6 parts by weight of anthracite powder and 3 parts by weight of fluorite powder are added into the comparative example 1, after the modification reduction reaction is finished, copper slag in the slag ladle is poured out, mechanical crushing, screening, grinding and magnetic separation are carried out to obtain metal iron particles and iron concentrate powder, the iron recovery rate is 28% by analysis, and the waste heat utilization rate is 71%.
In the description of the invention, the term "molten slag" is acidic molten metallurgical slag rich in Fe and Si, which is generated after nonferrous metals such as copper and nickel are smelted by a pyrogenic process. The term "industrial soda ash" refers to industrial sodium carbonate, the mass percentage of which is more than 98%.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (9)
1. The slag modification reducing agent is characterized by being spherical particles with the grain diameter of 10-30mm and comprising the following components: 100 parts of flux, 5-24 parts of reducing agent, 8-18 parts of binder and 0-10 parts of fluxing agent, wherein the flux is selected from at least one of limestone, quicklime or hydrated lime; the reducing agent is at least one of anthracite powder, coke powder, blue carbon powder or reducing coal; the binder is at least one of clay, cement, sodium silicate, resin or water; the fluxing agent is at least one of industrial soda ash, fluorite or iron ore powder.
2. The slag-modifying reducing agent according to claim 1, wherein the slag-modifying reducing agent is spherical particles having a core-shell structure, and has a particle size of 15 to 25mm, wherein the core has a particle size of 5 to 10mm, and comprises 5 to 24 parts by weight of a reducing agent, 6 to 12 parts by weight of a binder, and 0 to 3 parts by weight of an activator, wherein the activator is at least one selected from the group consisting of industrial soda ash, sodium chloride, potassium carbonate, and fluorite, and the core is externally coated with a shell comprising 100 parts by weight of a flux selected from at least one of limestone, dolomite, quicklime, and slaked lime, 2 to 6 parts by weight of a binder, and 0 to 10 parts by weight of a flux.
3. A preparation method of the slag modified reducing agent according to claim 1, characterized in that 100 parts by weight of the flux, 5-24 parts by weight of the reducing agent, 8-18 parts by weight of the binder and 0-10 parts by weight of the flux are uniformly mixed, ground into powder and then granulated to obtain the spherical particle modified reducing agent with the particle size of 10-30 mm.
4. The method of preparing a slag-modifying reductant according to claim 3, comprising the steps of:
a. respectively grinding 5-24 parts by weight of reducing agent, 6-12 parts by weight of binder and 0-3 parts by weight of activating agent into powder, uniformly mixing, and carrying out primary granulation to obtain particles with the particle size of 5-10mm, wherein the activating agent is selected from at least one of industrial soda ash, sodium chloride, potassium carbonate or fluorite;
b. uniformly mixing 100 parts by weight of flux, 2-6 parts by weight of binder and 0-10 parts by weight of flux, and grinding the mixture into powder, wherein the flux is selected from at least one of limestone, dolomite, quicklime or hydrated lime;
c. and (b) adding the material particles obtained in the step (a) into a granulator to serve as an inner core of a slag modification reducing agent, coating the powder obtained in the step (b) on the inner core, and carrying out secondary granulation to obtain spherical particles with a core-shell structure and the particle size of 15-25 mm.
5. The method for preparing a slag-modified reducing agent according to claim 3, wherein the granulation is rotary disk granulation or extrusion granulation.
6. The method for recovering iron by using the residual heat of the molten slag is characterized by comprising the following steps of:
a. in the process of discharging the molten slag from the smelting furnace and pouring the molten slag into a heat preservation container, simultaneously adding the molten slag modified reducing agent of any one of claims 1-2 into the molten slag flow to carry out modified reduction reaction, wherein the molten slag is copper slag and/or nickel slag, and the modified reducing agent is 14-50% of the total mass of the molten slag;
b. and c, after the molten slag and the modified reducing agent are reacted in the step a, crushing the solid slag in the heat-preservation container, and performing magnetic separation to obtain metal iron particles and/or iron concentrate powder.
7. The method for recovering iron by utilizing the residual heat of the molten slag as claimed in claim 6, wherein the method further comprises the step c of adding a flux, a reducing agent and a binder into the tailings which are not subjected to magnetic separation in the step b, uniformly mixing, grinding and granulating to obtain particles with the particle size of 15-30mm, feeding the particles into a roasting furnace for reduction at the roasting temperature of 1200-1400 ℃ to obtain metallized pellets, crushing, and performing magnetic separation to obtain metal iron particles and/or iron concentrate powder.
8. The method for recovering iron by using the residual heat of the slag according to the claim 6 or 7, wherein the heat preservation container in the step a is connected with a flue gas recovery device and is used for recovering valuable metals in the flue gas.
9. The method for recovering iron by using the residual heat of the molten slag according to claim 7, wherein the mass ratio of the tailings, the fluxing agent, the reducing agent and the binding agent in the step c is 100:5-22:8-20:4-16, wherein the fluxing agent is selected from at least one of limestone, dolomite, quick lime or hydrated lime; the reducing agent is at least one of anthracite powder, coke powder, blue carbon powder or reducing coal; the binder is at least one selected from clay, cement, sodium silicate, resin or water.
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