CN112410493A - Method for preparing metal powder by hydrogen reduction - Google Patents
Method for preparing metal powder by hydrogen reduction Download PDFInfo
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- CN112410493A CN112410493A CN202011204201.5A CN202011204201A CN112410493A CN 112410493 A CN112410493 A CN 112410493A CN 202011204201 A CN202011204201 A CN 202011204201A CN 112410493 A CN112410493 A CN 112410493A
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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
- C21B13/0073—Selection or treatment of the reducing gases
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- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
- B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
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Abstract
The invention discloses a method for preparing metal powder by hydrogen reduction, belongs to the technical field of powder metallurgy, and solves the problems of low reduction efficiency, long time and unsuitability for mass production in the existing iron powder preparation. The method comprises the following steps: step S1, preparing materials, and then mixing uniformly and pelletizing; step S2, drying the green pellets; step S3, carrying out primary hydrogen reduction on the dried pellets; s4, crushing the material subjected to primary hydrogen reduction cooling, and then performing secondary hydrogen reduction on the crushed material; and step S5, crushing, ball-milling and screening the iron powder obtained by secondary hydrogen reduction to obtain the metal iron powder. The method has the advantages of zero carbon emission, environmental protection and the like, and accords with the low-carbon metallurgy policy advocated by the state.
Description
Technical Field
The invention relates to the technical field of hydrogen reduction and powder metallurgy preparation, in particular to a method for preparing metal powder by hydrogen reduction.
Background
The powder metallurgy industry is one of the important industries in the field of new materials in China. The powder metallurgy parts are widely applied to various mechanical industries such as airplanes, firearms, motorcycles, family cars, automobiles, agricultural machinery, mines, electric tools, machine tools, transportation and the like.
In the prior art, reduced iron powder is usually prepared into sponge iron by using two-time reduction, namely, solid carbon reduction, and the main process of the one-time reduction is as follows: (iron ore concentrate, steel rolling iron scale, etc.) → drying → magnetic separation → crushing → sieving → canning → entering into a primary reduction furnace → sponge iron. And (3) secondary fine reduction process: sponge iron → cleaning and brushing → crushing → magnetic separation → secondary reduction furnace → powder block → disintegration → magnetic separation → sieving → classification → mixing → packaging → finished product. The high-quality iron powder produced by the reduction method has various parameters reaching the standard, wherein Fe is more than or equal to 98 percent, carbon is less than or equal to 0.1 percent, phosphorus and sulfur are less than 0.03 percent, and the hydrogen loss is 0.1 to 0.2 percent.
The temperature in the reduction kiln of the tunnel kiln is controlled to be 1150-1200 ℃, the coal consumption per ton of iron is as high as 1500kg (if gas heating is adopted, the coal consumption is about 1000 kg), the service life of tank materials is short, the smelting period is long (about 70 hours including preheating, heating and cooling), the equipment is too long, and the occupied area is large.
With the good pursuit of the environment, hydrogen reduction is receiving attention as a zero-emission reduction mode. In the powder metallurgy industry, hydrogen reduction occurs in the secondary reduction of metallic iron powder in order to remove residual oxygen and carbon.
CN108080649A discloses a method for preparing metal iron powder for powder metallurgy by low-temperature carbon reduction and hydrogen secondary reduction, which reduces the coal consumption from 1000 kg per ton of metal powder to 300 kg per ton of metal powder and has obvious effect.
CN201710407863 discloses a method for preparing superfine iron powder by low-cost low-temperature direct reduction, which comprises the steps of firstly preparing pure iron concentrate into superfine iron concentrate powder of 1-20 microns, and then reducing the superfine iron concentrate powder with hydrogen in one step at 600-750 ℃ in a pusher furnace to obtain the superfine metal iron powder. The method is suitable for the superfine iron powder with small amount and high added value. At present, no related process exists for preparing large-scale metal powder with the granularity of 100-200 meshes for powder metallurgy by reducing pure iron concentrate powder by using pure hydrogen.
Disclosure of Invention
In view of the above analysis, the present invention provides a method for preparing metal powder by hydrogen reduction, and mainly provides a method for preparing large-scale metal powder with a particle size of 100-200 meshes for powder metallurgy by hydrogen reduction of pure iron concentrate powder.
The purpose of the invention is mainly realized by the following technical scheme:
the invention provides a method for preparing metal powder by hydrogen reduction, which comprises the following steps:
step S1, pelletizing: mixing pure iron concentrate powder with total iron content of more than 71.0% and a binder according to a mass ratio of 100: 1-5, and then uniformly mixing; pelletizing the uniformly mixed materials to obtain green pellets;
step S2, drying: drying the green pellets, and controlling the water content in the pellets to be below 2%;
and S3, feeding the dried pellets into a primary hydrogen reduction furnace, introducing hydrogen gas, and performing primary hydrogen reduction, wherein the reduction parameters are as follows: the thickness of the cloth is 20 mm-150 mm, the temperature of the high-temperature section in the furnace is 800-950 ℃, the material stays in the high-temperature section in the furnace for 30 min-180 min, then the heated material enters a cooling water jacket for cooling, and the cooling time is 30-180 min;
step S4, crushing the material after primary hydrogen reduction cooling, then sending the crushed material into a secondary hydrogen reduction furnace for secondary hydrogen reduction, wherein the temperature in the furnace is 800-950 ℃, the thickness of the material is 10-60 mm, the heating time is 60-240 min, the iron powder obtained after reduction is discharged after cooling, and the retention time in a cooling section is 60-240 min;
and step S5, crushing, ball-milling and screening the iron powder obtained by secondary hydrogen reduction to obtain the metal iron powder with the granularity of 100-600 meshes and the total iron mass content of more than or equal to 98%.
Further, in step S1, the binder is an organic binder.
Further, in step S1, the green pellets have a particle size of 5mm to 20 mm.
Further, in step S3, the primary hydrogen reduction furnace is an enclosed mesh-belt hydrogen reduction furnace.
Further, in step S3, the pressure in the closed mesh-belt-type hydrogen reducing furnace is 100Pa to 10000 Pa.
Further, in the step S3, the amount of hydrogen gas introduced into the primary hydrogen reduction furnace is 1000 to 1500Nm3Per ton of pellets.
Further, in the step S4, the particle size of the crushed material is 50 to 200 meshes.
Further, the hydrogen gas leaving the primary hydrogen reduction furnace is sent into a hydrogen buffer tank after being dedusted and dehydrated, a part of hydrogen gas in the hydrogen buffer tank is preheated by a preheating system and then is used as reducing gas in the primary hydrogen reduction furnace or the secondary hydrogen reduction furnace for recycling, and the other part of hydrogen gas is used as a heat source of the preheating system.
Further, in step S4, the secondary hydrogen reduction furnace is a steel strip furnace or a pusher furnace.
Further, in step S1, alloy oxide powder or metal powder is added in the batching process to prepare alloy metal powder; or reducing by using iron ore powder with common purity to prepare the sponge iron powder with the reduction rate not lower than 90 percent.
The invention has the following beneficial effects:
(1) the method changes the technological method for preparing the metal powder by carbon reduction and realizes zero carbon emission. The current situation that the existing pure hydrogen reduction can only produce superfine iron powder which is a small-scale product is changed, and the large-scale comprehensive hydrogen reduction of the iron powder used in the powder metallurgy industry becomes possible.
(2) A mesh belt type hydrogen reduction furnace is adopted, iron concentrate powder is made into pellets and then is laid on the mesh belt, and hydrogen can penetrate through the whole pellets in the furnace, so that the reduction effect is good; the pellet does not move on the mesh belt, so the pellet has small bearing capacity and friction force and low pellet strength requirement, and the green pellet does not need to be oxidized and roasted to form an oxidized pellet with higher strength, thereby reducing smelting procedures and manufacturing cost.
(3) The invention preheats hydrogen, and the mesh belt furnace adopts an electric heating mode for heat supply, thereby reducing the use amount of the hydrogen, and the utilization rate of the hydrogen can reach 30 percent and is far higher than the utilization rate of the hydrogen reduced by a pure hydrogen shaft furnace by 20 percent.
(4) The hydrogen after reduction is sent into the hydrogen buffer tank after dust removal and dehydration, one part of hydrogen in the hydrogen buffer tank is used as reducing gas for recycling after passing through the preheating system, and the other part of hydrogen is used as a heat source of the preheating system, so that the hydrogen recycling is realized, and the energy is saved.
(5) The method has wide application range, can be used for preparing metal iron powder for powder metallurgy, and can be used for preparing alloy metal powder by adding nickel-based metal, cobalt-based metal or oxide powder in the burdening process; or the common-purity iron ore powder is adopted for primary hydrogen reduction, so that the sponge iron powder with the reduction rate of not less than 90 percent can be obtained.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a process flow diagram of example 1;
FIG. 2 is a process flow diagram of example 2;
FIG. 3 is a process flow diagram of example 3;
FIG. 4 is a process flow diagram of example 4.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention.
The invention provides a method for preparing metal powder by hydrogen reduction, which comprises the following steps:
step S1, pelletizing: mixing pure iron concentrate powder (acid insoluble matter is less than 0.5%) with total iron content of more than 71.0% and an organic binder according to the mass ratio of 100: 1-5, and then uniformly mixing in a mixer; pelletizing the uniformly mixed materials to obtain green pellets, wherein the particle size of the green pellets is 5-20 mm;
step S2, drying: drying the green pellets, and controlling the water content in the pellets to be below 2%;
and S3, feeding the dried pellets into a primary hydrogen reduction furnace, introducing hydrogen gas, performing primary hydrogen reduction, realizing positive pressure operation of 100-10000 Pa in the hydrogen reduction furnace, and ensuring the temperature in the furnace required by reduction through electric heating. The reduction parameters are as follows: the thickness of the cloth is 20 mm-150 mm, the temperature of the high-temperature section in the furnace is 800-950 ℃, the material stays in the high-temperature section in the furnace for 30 min-180 min, then the heated material enters a cooling water jacket along with a mesh belt to be cooled for 30-180 min;
step S4, crushing the material after primary hydrogen reduction cooling to an average particle size of 50-200 meshes, then sending the crushed material into a secondary hydrogen reduction furnace for secondary hydrogen reduction, wherein the temperature in the furnace is 800-950 ℃, the thickness of the material is 10-60 mm, the heating time is 60-240 min, the iron powder obtained after reduction is discharged after cooling, and the retention time in a cooling section is 60-240 min;
and step S5, crushing, ball-milling and screening the iron powder obtained by secondary hydrogen reduction to obtain metal iron powder with various particle sizes (100-600 meshes) and total iron mass content of more than or equal to 98%.
Specifically, in step S1, in order to ensure high purity of the prepared metallic iron powder, the purity of the raw material pure iron concentrate powder is high, and the total iron content in the pure iron concentrate powder is controlled to be 71.0% or more by mass, and the mass content of acid-insoluble substances is controlled to be less than 0.5%.
Specifically, in step S1, in order to reduce new impurities substituted by the inorganic binder or the mixed binder, the purity of the product is affected; the binder is selected from organic binders such as waste molasses, starch, dextrin, etc. In order to ensure that pellets with good quality are prepared and no binder is wasted, the mass ratio of the pure iron concentrate powder to the organic binder is controlled to be 100: 1-5.
Specifically, in step S1, disk pelletizing is adopted; or by using a press ball, a roller, a rotary granulator and the like. Considering that the energy consumption of the reduction process is also related to the particle size of the formed pellets, the particles are too large, and the time required for reduction is long; the particles are too small and dust entrainment is easily formed. Therefore, the particle size of the pellets is controlled to be 5 mm-20 mm.
Specifically, in step S2, the water content in the dried pellets is controlled to be 2% or less in order to prevent the pellets from bursting in the reduction furnace due to the excessively high water content.
Specifically, in the step S2, the pellets may be dried by a chain plate dryer or a drum dryer; waste heat flue gas generated in the system can be used for heating and drying, and gases such as hydrogen or natural gas can also be used for heating and drying.
It should be noted that, in the conventional secondary hydrogen reduction in the powder metallurgy industry, a boat pushing furnace or a steel belt furnace is adopted for reduction, metal powder is laid in a boat or on a steel belt, hydrogen diffuses and reduces downwards on the surface of the powder, the reaction speed is very slow, the method is suitable for reducing the metal powder with the metallization rate of more than 95%, and finally the residual oxygen of the metal powder is controlled below 0.5%. If the reduction of the raw material iron oxide is carried out, the reduction efficiency is very low, the paving thickness is below 10mm, the hydrogen conversion rate in the furnace is low, generally only about 10%, the circulating hydrogen quantity is too large, the repeated heating power consumption is too high, and the method is only used for superfine iron powder with high product selling price and small using amount at present. If the method is applied to ordinary metallic iron powder with lower price, the treatment cost is too high, and the economy is not realized, which is the root reason why the ordinary metallic iron powder is not directly reduced by hydrogen.
The applicant has conducted extensive studies to provide that, in step S3, the primary hydrogen reduction furnace employs a closed mesh belt type primary hydrogen reduction apparatus (e.g., a closed mesh belt type hydrogen reduction furnace) to form pellets of pure iron concentrate powder and then to lay the pellets on a mesh belt, and hydrogen gas can pass through the entire pellets in the furnace. Compared with the conventional shaft furnace pellet reduction, the pellet in the invention does not move on the mesh belt, so the pellet has small bearing force and friction force, and the pellet strength requirement is low, so the green pellet does not need to be oxidized and roasted to form an oxidized pellet with higher strength, thereby the smelting process can be reduced, and the manufacturing cost can be reduced.
Specifically, in step S3, the mesh-belt-type hydrogen reduction furnace is closed, the pressure in the mesh-belt-type hydrogen reduction furnace can be positive pressure of 100Pa to 10000Pa (indicated pressure), and the feeding, discharging, mesh belt feeding and discharging of the mesh-belt-type hydrogen reduction furnace need to be sealed.
In step S3, too little hydrogen gas is introduced into the mesh-belt hydrogen reduction furnace, which leads to insufficient reduction, and too much hydrogen gas leads to too much unreacted hydrogen gas, which wastes energy; therefore, the amount of the hydrogen introduced into the mesh belt type hydrogen reduction furnace is controlled to be 1000-1500 Nm3Per ton of pellets.
In the conventional shaft furnace pellet reduction, because a supplementary heating means is not arranged in the furnace, the reduction reaction heat consumption and pellet physical heat in the furnace are from external preheated hydrogen, so the hydrogen consumption is high, the utilization rate is only about 20 percent, and a large amount of hydrogen needs to be repeatedly used. The invention changes the traditional heating mode, firstly preheats the hydrogen, and simultaneously adopts an electric heating mode to supply heat in the mesh belt type hydrogen reduction furnace, thereby reducing the usage amount of the hydrogen, ensuring that the utilization rate of the hydrogen can reach 30 percent and is far higher than the utilization rate of the hydrogen reduced by 20 percent in the shaft furnace. Therefore, in step S3, the charging temperature of hydrogen gas is controlled to 700 to 950 ℃.
Specifically, in step S3, the high temperature section in the hydrogen reduction furnace has too high temperature and the high temperature section has too long residence time, which may cause sintering of iron powder, increase difficulty in subsequent crushing and grinding, and increase energy consumption; the reduction rate is reduced when the temperature is too low; the time is too short, the pellet reduction effect is poor, and the purity is low; the paving thickness is too small, and the production economy is not good; too large, slow heat transfer and poor reduction effect; the retention time in the cooling section is too long, the cooling water jacket is too long, and the equipment is wasted; the time is too short, and the cooling effect is not good; therefore, the thickness of the cloth is controlled to be 20 mm-150 mm, the temperature of the high-temperature section in the furnace is controlled to be 800-950 ℃, the material stays for 30 min-180 min in the high-temperature section in the furnace, and the cooling time is controlled to be 30 min-180 min.
In order to be able to recycle the unused hydrogen gas in the primary hydrogen reduction furnace, the hydrogen gas leaving the primary hydrogen reduction furnace is subjected to dust removal (e.g. high temperature dust removal), dehydration (and/or CO removal)2) And the pressurized hydrogen is sent into a hydrogen buffer tank which plays a role in stabilizing the hydrogen flow. A part of the hydrogen gas in the hydrogen buffer tank is preheated by a preheating system (for example, a gas preheating system) and then is recycled as the reducing gas in the hydrogen reducing furnace, and the other part of the hydrogen gas is used as the heat source of the preheating system.
Specifically, in step S3, the hydrogen gas source introduced into the primary hydrogen reduction furnace includes externally supplied hydrogen gas and recycled hydrogen gas. The amount of hydrogen supplied from the outside is reduced by recycling the hydrogen, thereby reducing the cost.
Specifically, in step S4, the metallization ratio of the material after primary hydrogen reduction cooling is about 95%. The reason is that if the metallization rate is over 97 percent directly, the efficiency of reaction equipment is obviously reduced, so the invention adopts two-step reduction, firstly adopts primary hydrogen reduction (rough reduction) to obtain primary metal iron balls with the metallization rate of about 95 percent, and then carries out secondary hydrogen after crushing to obtain the final qualified metal powder with the total iron content of over 98 percent.
Specifically, in step S4, the reaction speed is slow and the reaction is insufficient due to the particle size (average particle size) of the crushed material being too large, and therefore, the material is crushed to an average particle size of 50 to 200 mesh.
Specifically, in step S4, the secondary hydrogen reduction furnace may be a heating furnace type such as a steel strip furnace or a pusher furnace. The hydrogen in the secondary hydrogen reduction furnace can be normal temperature hydrogen, or the hydrogen can be preheated to 800-950 ℃ and then is introduced into the furnace.
Specifically, in step S4, the hydrogen containing water reduced in the secondary hydrogen reduction furnace may be subjected to dust removal (e.g., high temperature dust removal), dehydration (and/or CO removal)2) The pressurizing machine is pressurized and sent into the hydrogen buffer tank for recycling, and the traditional direct ignition mode outside the furnace can be adopted for treatment.
Specifically, in step S4, the hydrogen gas in the secondary hydrogen reduction furnace may be pure hydrogen gas supplied from the outside, or may be reduced by using a mixed gas of hydrogen gas and nitrogen gas prepared by thermal decomposition of liquid ammonia instead of pure hydrogen.
In step S1, various alloy powders can be prepared by adding nickel-based, cobalt-based metal or oxide powders during the compounding process.
In the above preparation method, the secondary hydrogen reduction step is omitted (i.e., steps S4 and S5 are omitted), and the cooled material obtained in steps S1 to S3 is the sponge iron balls, and the sponge iron balls are crushed to obtain the sponge iron powder. Sponge iron balls or sponge iron powder can be used as metallurgical raw materials.
Specifically, in step S1, the pure iron concentrate powder is replaced with iron ore powder of ordinary purity (total iron content 62% to 68%), so that sponge iron balls or sponge iron powder (after crushing) with a reduction rate of not less than 90% can be obtained. The binder used in the pelletization under such conditions may be an inorganic binder (e.g., bentonite) or an inorganic-organic hybrid binder.
Specifically, in the steps S3 and S4, in addition to the reduction with hydrogen gas, a hydrogen-rich gas may be used for the reduction, and the hydrogen content in the hydrogen-rich gas is not less than 50%.
Compared with the prior art, the method for preparing the metal iron powder by hydrogen reduction changes the process method for preparing the metal iron powder by carbon reduction, and realizes zero emission of carbon. The current situation that only superfine iron powder can be produced by hydrogen reduction at present is changed, and the large-scale comprehensive hydrogen reduction of the iron powder for the powder metallurgy industry becomes possible.
The invention adopts the mesh belt type hydrogen reduction furnace, iron ore concentrate powder is made into pellets and then is laid on the mesh belt, and hydrogen can pass through the whole pellets in the furnace, so the reduction effect is good; the pellet does not move on the mesh belt, so the pellet has small bearing capacity and friction force and low pellet strength requirement, and the green pellet does not need to be oxidized and roasted to form an oxidized pellet with higher strength, thereby reducing smelting procedures and manufacturing cost.
The invention preheats hydrogen, and the mesh belt furnace adopts an electric heating mode for heat supply, thereby reducing the use amount of the hydrogen, and the utilization rate of the hydrogen can reach 30 percent and is far higher than the utilization rate of the hydrogen reduced by a pure hydrogen shaft furnace by 20 percent.
According to the invention, the reduced hydrogen is sent into the hydrogen buffer tank after being dedusted and dehydrated, one part of the hydrogen in the hydrogen buffer tank is used as the reducing gas for recycling after passing through the preheating system, and the other part of the hydrogen is used as the heat source of the preheating system, so that the recycling of the hydrogen is realized, and the energy is saved.
Example 1
This example provides a method for preparing metallic iron powder by hydrogen reduction, which adopts the above-mentioned method for preparing metallic iron powder by hydrogen reduction, and the process flow chart is shown in fig. 1. The specific details are as follows:
the composition of the pure iron ore concentrate powder is shown in Table 1, and the average particle size is 300 mesh. The organic binder is waste syrup.
TABLE 1 main component/wt% of pure iron ore concentrate powder
| All iron | Moisture content | Acid insoluble substance |
| 71.6 | <1.0 | 0.2 |
The mass ratio of the pure iron concentrate powder to the organic binder is 100: 3, uniformly mixing the pure iron concentrate powder and the organic binder in a continuous mixer, and feeding the uniformly mixed material into a disc pelletizer to pelletize, wherein the granularity of the green pellets is 10-15 mm; the green pellets are dried by a chain plate dryer, and the water content in the pellets is controlled to be below 2 percent.
And (3) conveying the dried pellets into closed mesh belt type primary hydrogen reduction equipment (a primary hydrogen reduction furnace), and electrically heating in the reduction furnace to ensure the temperature in the furnace required by reduction. The reduction parameters are as follows: the thickness of the cloth is 50mm, the temperature of the high-temperature section in the furnace is 900 ℃, the material stays for 90min in the high-temperature section in the furnace, and then the heated material enters the cooling water jacket along with the mesh belt to be cooled for 90 min.
And crushing the metal pellets (namely sponge pellets) after primary hydrogen reduction cooling to obtain fine metal iron powder with the average particle size of 100-150 meshes, and then conveying the fine metal iron powder into a secondary hydrogen reduction steel belt furnace for reduction. Cold hydrogen is fed into the furnace, the furnace is electrically heated, the temperature in the furnace is 800-950 ℃, the thickness of the material is 50mm, the retention time of the iron powder in a preheating section and a heating section is 120min, the reduced iron powder is cooled by a water cooling jacket and then discharged, and the retention time in a cooling section is 120 min. The water-containing hydrogen leaving the secondary hydrogen reduction steel belt furnace returns to the hydrogen buffer tank after dust removal and dehydration.
And crushing, ball-milling and screening the iron powder subjected to secondary hydrogen reduction to obtain the metal iron powder with various particle sizes (100-600 meshes) and the total iron mass content of 98.5%.
Preheating hydrogen provided by the primary hydrogen reduction furnace and recycled hydrogen, introducing the preheated hydrogen into the primary hydrogen reduction furnace, and enabling the hydrogen to enter the primary hydrogen reduction furnace to be 1200Nm3Per ton of pellets, the charging temperature of hydrogen is 800 ℃; and (3) the hydrogen leaving the primary hydrogen reduction furnace is sent into a hydrogen buffer tank after dust removal and dehydration, part of the hydrogen enters the gas preheating system again for recycling, and the other part of the hydrogen is used as a heat source of the gas preheating system.
The hot flue gas generated by the gas preheating system is used as a drying heat source for the green pellets.
The total iron content of the sponge pellets obtained by primary hydrogen reduction in the process flow reaches 97%, so that the sponge pellets can be directly sold as products without secondary hydrogen reduction or sold after being crushed into sponge iron powder according to different product user requirements.
Example 2
This example provides a method for preparing metallic iron powder by hydrogen reduction, which adopts the above-mentioned method for preparing metallic iron powder by hydrogen reduction, and the process flow chart is shown in fig. 2. The specific details are as follows:
the pure iron ore concentrate powder has the components shown in Table 2, and the average particle size is 300 meshes. The organic binder used is dextrin.
TABLE 2 main component/wt% of pure iron ore concentrate powder
| All iron | Moisture content | Acid insoluble substance |
| 71.9 | <1.0 | 0.15 |
The mass ratio of the pure iron concentrate powder to the organic binder is 100: 2.5. then mixing the pure iron concentrate powder and the organic binder uniformly in a continuous mixer, and feeding the uniformly mixed material into a roller granulator to form pellets, wherein the particle size of the green pellets is 8-15 mm; the green pellets are dried by a roller dryer, and the water content in the pellets is controlled below 2 percent.
And (3) feeding the dried pellets into closed mesh belt type primary hydrogen reduction equipment (a primary hydrogen reduction furnace), wherein positive pressure operation of 100-10000 Pa can be realized in the reduction furnace, and the temperature in the reduction furnace is ensured by electric heating. The reduction parameters are as follows: the thickness of the cloth is 100 mm-150 mm, the temperature of the high temperature section in the furnace is 900-950 ℃, the material stays for 120 min-180 min in the high temperature section in the furnace, then the heated material enters a cooling water jacket along with a mesh belt to be cooled, and the cooling time is 120-180 min.
And crushing the metal pellets after primary hydrogen reduction cooling to obtain fine metal iron powder with the average particle size of 80-130 meshes, and then conveying the fine metal iron powder into a secondary hydrogen reduction furnace (secondary hydrogen reduction steel belt furnace) for reduction. The secondary hydrogen reduction furnace is a steel belt furnace, hydrogen is preheated to 850 ℃ and enters the steel belt furnace, the furnace is electrically heated, the temperature in the furnace is 850 ℃, the thickness of the material is 40mm, the retention time of iron powder in a preheating section and a heating section is 120min, the reduced iron powder is cooled by a water cooling jacket and then discharged, and the retention time in a cooling section is 120 min. The hydrous hydrogen leaving the secondary hydrogen reduction furnace returns to the hydrogen buffer tank after high-temperature dust removal, dehydration and pressurization.
And crushing, ball-milling and screening the iron powder subjected to secondary hydrogen reduction to obtain metal iron powder with various particle sizes (100-600 meshes) and total iron mass content of 99.0%.
Preheating hydrogen provided by the primary hydrogen reduction furnace and recycled hydrogen, introducing the preheated hydrogen into the primary hydrogen reduction furnace, and enabling the amount of the hydrogen entering the primary hydrogen reduction furnace to be 1000-1500 Nm3Per ton of pellets, the charging temperature of hydrogen is 900-950 ℃; and (2) sending the hydrogen leaving the primary hydrogen reduction furnace into a hydrogen buffer tank after dedusting and dehydration, reusing the hydrogen after entering the preheating system for preheating, and preheating the hydrogen entering the primary hydrogen reduction furnace to 700-950 ℃ by using natural gas as a heat source of the gas preheating system.
The hot flue gas generated by the gas preheating system is used as a drying heat source for the green pellets.
Example 3
This example provides a method for preparing metallic iron powder by hydrogen reduction, which adopts the above-mentioned method for preparing metallic iron powder by hydrogen reduction, and the process flow chart is shown in fig. 3. The specific details are as follows:
the pure iron ore concentrate powder has the components shown in Table 3, and the average particle size is 300 meshes. Pure nickel oxide powder is adopted as an additive of nickel, the impurity mass content is less than 0.5%, and the average particle size is 200 meshes. The organic binder used is starch.
The mass ratio of the pure iron concentrate powder, the pure nickel oxide and the organic binder is 100: 5: 4. then evenly mixing the materials in a continuous mixer, and feeding the evenly mixed materials into a ball press machine to form balls, wherein the granularity of the green balls is 7-15 mm; the green pellets are dried by a roller dryer, and the water content in the pellets is controlled below 2 percent.
And (3) conveying the dried pellets into closed mesh belt type primary hydrogen reduction equipment (a primary hydrogen reduction furnace) for reduction, wherein positive pressure operation of 100-10000 Pa can be realized in the reduction furnace, and the temperature in the furnace required by reduction is ensured through electric heating. The reduction parameters are as follows: the thickness of the cloth is 20 mm-50 mm, the temperature of the high temperature section in the furnace is 800-850 ℃, the material stays for 30 min-90 min in the high temperature section in the furnace, then the heated material enters a cooling water jacket along with a mesh belt to be cooled, and the cooling time is 30-90 min.
And crushing the metal pellets after primary hydrogen reduction cooling to obtain fine metal powder with the average particle size of 50-200 meshes, and then feeding the fine metal powder into a secondary hydrogen reduction furnace for reduction. The secondary hydrogen reducing furnace is a push boat furnace, liquid ammonia decomposition gas is used as a hydrogen source, cold liquid ammonia decomposition gas is fed into the push boat furnace, electric heating is adopted in the push boat furnace, the temperature in the push boat furnace is 800-850 ℃, the material thickness is 10-30 mm, the stay time of iron powder in a preheating section and a heating section is 60-120 min, the reduced iron powder is cooled by a water cooling sleeve and then discharged from the push boat furnace, and the stay time in a cooling section is 60-120 min. The hydrogen leaving the boat pushing furnace is directly ignited for treatment, and the waste heat is comprehensively utilized.
Crushing, ball-milling and screening the iron powder after secondary hydrogen reduction to obtain the ferronickel alloy powder with various particle sizes (100 meshes-600 meshes), 93.2 percent of total iron mass content and 5.1 percent of nickel content.
Make-up hydrogen-rich gas (60% H)2-35％CO-5％N2) Preheating the recycled gas, introducing the preheated gas into a primary hydrogen reduction furnace, wherein the gas amount entering the primary hydrogen reduction furnace is 1100Nm3Per ton of pellets, the charging temperature is 700 ℃; the hydrogen-rich gas leaving the primary hydrogen reduction furnace is subjected to high-temperature dust removal, dehydration and CO removal2And the hydrogen-rich gas enters a hydrogen buffer tank (hydrogen-rich gas buffer tank) after the pressurizer, the purified hydrogen-rich gas enters a hydrogen-rich preheating system again for recycling, a part of the hydrogen-rich gas before the carbon dioxide is removed is taken as a heat source of the preheating system for use, and the hydrogen-rich gas entering the closed mesh belt type primary hydrogen reduction equipment is preheated to 700-950 ℃.
The hot flue gas generated by the gas preheating system is used as a drying heat source for the green pellets.
Example 4
This example provides a method for preparing metallic iron powder by hydrogen reduction, which adopts the above-mentioned method for preparing metallic iron powder by hydrogen reduction, and the process flow chart is shown in fig. 4. The specific details are as follows: the iron ore concentrate powder has the components shown in Table 4, and the average particle size is 200 meshes. The adopted inorganic binder is bentonite.
TABLE 3 main component/wt% of iron ore concentrate powder
| All iron | SiO2 | CaO | Al2O3 | MgO | S | P |
| 67.52 | 4.62 | 0.27 | 0.23 | 1.58 | 0.05 | 0.005 |
The mass ratio of the iron ore concentrate powder to the bentonite is 100: 2. then evenly mixing the materials in a continuous mixer, and feeding the evenly mixed materials into a disc pelletizer to be pelletized, wherein the granularity of the green pellets is 5-20 mm; the green pellets are dried by a roller dryer, and the water content in the pellets is controlled below 2 percent.
And (3) conveying the dried pellets into closed mesh belt type primary hydrogen reduction equipment (a primary hydrogen reduction furnace) for reduction, wherein positive pressure operation of 100-10000 Pa can be realized in the reduction furnace, and the temperature in the furnace required by reduction is ensured through electric heating. The reduction parameters are as follows: the thickness of the cloth is 50 mm-100 mm, the temperature of the high temperature section in the furnace is 850-900 ℃, the material stays in the high temperature section in the furnace for 90 min-150 min, then the heated material enters a cooling water jacket along with the mesh belt to be cooled, and the cooling time is 90 min-150 min.
The total iron content of the cooled sponge iron balls reaches 90%, and the sponge iron balls can be briquetted (agglomerated) or crushed into iron powder for sale according to users of subsequent users.
The supplemented hydrogen and the recycled hydrogen are preheated and then are introduced into a primary hydrogen reduction furnace, and the amount of the hydrogen entering the primary hydrogen reduction furnace is 1400Nm3Per ton of pellets, the charging temperature of hydrogen is 900 ℃; the hydrogen leaving the primary hydrogen reduction furnace is sent into a hydrogen buffer tank (H) after being dedusted, dehydrated and pressurized by a pressurizer2Buffer tank), hydrogen is recycled after reentering the gas preheating system, and natural gas is used as the heat source of the gas preheating system.
The hot flue gas generated by the gas preheating system is used as a drying heat source for the green pellets.
Comparative example 1
This comparative example provides a method for preparing metallic iron powder by hydrogen reduction, which is the same as example 1 except that: the temperature of the high-temperature section in the primary hydrogen reduction furnace is 1000 ℃, and the material stays in the high-temperature section in the furnace for 120 min. Other steps are not described in detail.
In the method of the comparative example, the metal pellets cooled by primary hydrogen reduction are easy to sinter and difficult to crush, thereby greatly prolonging the time, improving the time cost and reducing the economic benefit.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. A method for preparing metal powder by hydrogen reduction is characterized by comprising the following steps:
step S1, pelletizing: mixing pure iron concentrate powder with total iron content of more than 71.0% and a binder according to a mass ratio of 100: 1-5, and then uniformly mixing; pelletizing the uniformly mixed materials to obtain green pellets;
step S2, drying: drying the green pellets, and controlling the water content in the pellets to be below 2%;
and S3, feeding the dried pellets into a primary hydrogen reduction furnace, introducing hydrogen gas, and performing primary hydrogen reduction, wherein the reduction parameters are as follows: the thickness of the cloth is 20 mm-150 mm, the temperature of the high-temperature section in the furnace is 800-950 ℃, the material stays in the high-temperature section in the furnace for 30 min-180 min, then the heated material enters a cooling water jacket for cooling, and the cooling time is 30-180 min;
step S4, crushing the material after primary hydrogen reduction cooling, then sending the crushed material into a secondary hydrogen reduction furnace for secondary hydrogen reduction, wherein the temperature in the furnace is 800-950 ℃, the thickness of the material is 10-60 mm, the heating time is 60-240 min, the iron powder obtained after reduction is discharged after cooling, and the retention time in a cooling section is 60-240 min;
and step S5, crushing, ball-milling and screening the iron powder obtained by secondary hydrogen reduction to obtain the metal iron powder with the granularity of 100-600 meshes and the total iron mass content of more than or equal to 98%.
2. The method for producing metal powder by hydrogen reduction according to claim 1, wherein in step S1, the binder is an organic binder.
3. The method for producing metal powder by hydrogen reduction according to claim 1, wherein in step S1, the green pellets have a particle size of 5mm to 20 mm.
4. The method for producing metal powder by hydrogen reduction according to claim 1, wherein the primary hydrogen reduction furnace is a closed mesh-belt hydrogen reduction furnace in step S3.
5. The method for producing metal powder by hydrogen reduction according to claim 4, wherein in step S3, the pressure in the closed mesh belt type hydrogen reducing furnace is 100Pa to 10000 Pa.
6. The method for producing metal powder by hydrogen reduction according to claim 1, wherein in step S3, the amount of hydrogen gas introduced into the primary hydrogen reduction furnace is 1000 to 1500Nm3Per ton of pellets.
7. The method for producing metal powder by hydrogen reduction according to claim 1, wherein in step S4, the particle size of the crushed material is 50 to 200 mesh.
8. The method for preparing metal powder by hydrogen reduction according to claim 1, wherein the hydrogen gas leaving the primary hydrogen reduction furnace is dedusted and dehydrated and then fed into a hydrogen buffer tank, a part of the hydrogen gas in the hydrogen buffer tank is preheated by a preheating system and then recycled as a reducing gas in the primary hydrogen reduction furnace or the secondary hydrogen reduction furnace, and the other part of the hydrogen gas is used as a heat source of the preheating system.
9. The method for preparing metal powder by hydrogen reduction according to claim 1, wherein the secondary hydrogen reduction furnace is a steel belt furnace or a pusher furnace in step S4.
10. The method for preparing metal powder by hydrogen reduction according to claims 1 to 9, wherein in step S1, alloy oxide powder or metal powder is added during batching to prepare alloy metal powder; or reducing by using iron ore powder with common purity to prepare the sponge iron powder with the reduction rate not lower than 90 percent.
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