CN114085939B - Smelting method of carbon-free sponge iron - Google Patents

Smelting method of carbon-free sponge iron Download PDF

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CN114085939B
CN114085939B CN202111296403.1A CN202111296403A CN114085939B CN 114085939 B CN114085939 B CN 114085939B CN 202111296403 A CN202111296403 A CN 202111296403A CN 114085939 B CN114085939 B CN 114085939B
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iron
molten iron
slag
molten
purity
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CN114085939A (en
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张俊
周和敏
郝晓东
杨光浩
沈朋飞
徐洪军
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Linyi Iron And Steel Industry Collaborative Innovation Center
CISRI Sunward Technology Co Ltd
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Linyi Iron And Steel Industry Collaborative Innovation Center
CISRI Sunward Technology Co Ltd
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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
    • C21B13/02—Making spongy iron or liquid steel, by direct processes in shaft furnaces
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
    • C01D1/04—Hydroxides
    • C01D1/20—Preparation by reacting oxides or hydroxides with alkali metal salts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/46—Sulfates
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C2200/00—Recycling of waste material
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Engineering & Computer Science (AREA)
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  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Abstract

The invention discloses a smelting method of carbon-free sponge iron, belongs to the technical field of sponge iron smelting, and solves the problems of complexity, high production cost and low productivity of the existing high-purity iron preparation method. The method comprises the following steps: step 1, preparing carbon-free sponge iron; step 2, adding the carbon-free sponge iron and lime flux into a vacuum induction furnace under a normal pressure state, heating and melting, and obtaining high-oxygen molten iron and molten slag after materials are completely melted; 3, transferring the molten slag from the vacuum induction furnace to a slag ladle in a vacuum state, and transferring the high-oxygen molten iron to a refining unit through a taphole of the eccentric furnace; step 4, spraying a deoxidizing agent into the high-oxygen molten iron of the refining unit by using the Ar blowing powder spraying unit to obtain high-purity molten iron; and 5, casting the high-purity molten iron in a vacuum environment, and stopping vacuumizing after casting is finished to obtain the high-purity cast iron. The invention shortens the smelting process of the sponge iron, improves the smelting efficiency of the carbon-free sponge iron and improves the quality of pure iron.

Description

Smelting method of carbon-free sponge iron
Technical Field
The invention relates to the technical field of sponge iron smelting, in particular to a smelting method of carbon-free sponge iron.
Background
In order to meet the steel requirements of important technical equipment and important engineering in different industries. High-end steel materials need to meet certain performance, and the basic requirement is 'cleanness'. The cleanliness of ferrous materials is often characterized by the total oxygen content (t.o) and S content of the steel in industrial production. With the development of steelmaking technology, higher requirements are provided for molten steel purity, which is generally represented by the sum of S + P + N + O + H, and the requirements for clean steel at present are that Sigma S + P + N + O + H is less than or equal to 50ppm. Except for the requirement of S, P, N, O, H, the contents of Si and Mn are generally required to be less than or equal to 0.02 percent, ti, V and Nb are less than or equal to 0.01 percent, and C is less than or equal to 0.01 percent, so that the carbon content of pure iron is within the range of less than or equal to 0.0218 percent. Therefore, the key to the preparation of high-end materials is the preparation of pure iron substrates.
The production by adopting the traditional long flow of iron ore-sintering (or pellet ore) -blast furnace ironmaking-steelmaking can still meet the requirement of industrial pure iron on the carbon content, but the production of the high-purity iron needs special refining process and equipment, and the large-scale production still has certain difficulty. At present, high-purity iron production enterprises are mainly concentrated abroad, pure iron products in China are all in industrial pure iron grade, the purity is mostly lower than 99.9%, high-purity iron mainly depends on import, and the high-purity iron becomes a bottleneck limiting the development of high-end steel materials in China.
The common process flow for preparing high-purity iron comprises the following steps: ion exchange method + solvent extraction method → electrolytic refining → cold crucible melting → zone melting. The electrolytic method is adopted to produce pure iron, the iron to be purified is taken as an anode, the salt solution of the iron is taken as electrolyte, the other pure metal is taken as a cathode for electrolysis, and the quite pure iron can be obtained on the cathode, and the purity is up to 99.999 percent. However, the main problems of the current high-purity iron production are high production cost and low productivity, and the demand gap of the market for the high-purity iron cannot be met in a short time.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a method for smelting carbon-free sponge iron, which is used to solve the problems of complex preparation method, high production cost and low productivity of the existing high purity iron.
The purpose of the invention is mainly realized by the following technical scheme:
the invention provides a smelting method of carbon-free sponge iron, which comprises the following steps:
step 1, carrying out shaft furnace reduction on the oxidized pellets by using hydrogen in a shaft furnace to obtain carbon-free sponge iron;
step 2, adding the carbon-free sponge iron and lime flux into a vacuum induction furnace under a normal pressure state, heating and melting, completing self-dephosphorization of molten slag in the melting process, and obtaining high-oxygen molten iron and molten slag after the materials are completely melted;
3, transferring the molten slag from the vacuum induction furnace to a slag ladle in a vacuum state, and transferring the high-oxygen molten iron to a refining unit through a taphole of the eccentric furnace;
step 4, spraying a deoxidizing agent into the high-oxygen molten iron of the refining unit by using Ar as a carrier gas and a stirring gas and using an Ar powder spraying unit, and synchronously deoxidizing, desulfurizing and degassing the high-oxygen molten iron in a vacuum environment to obtain high-purity molten iron;
and 5, casting the high-purity molten iron in a vacuum environment, and stopping vacuumizing after casting is finished to obtain the high-purity cast iron.
Further, in the step 2, the alkalinity of the slag is 3-3.5; the high-oxygen molten iron has a phosphorus content of <20ppm.
Further, in the step 2, 20-30% of high-oxygen molten iron is reserved in the vacuum induction furnace in the tapping process.
Further, in the step 2, pouring the molten slag once after the vacuum induction furnace is smelted for multiple times, and retaining 10% -15% of the molten slag in the vacuum induction furnace.
Further, in the step 4, the deoxidizer is metallic sodium particles; the molar ratio Na/O of the Na content in the metal sodium particles to the oxygen content in the high-oxygen molten iron is 1.05-1.1.
Further, in the step 4, after the synchronous deoxidation, the desulphurization and the degassing, the oxygen content and the sulfur content in the high-purity molten iron are both less than 10ppm.
Further, in the step 4, after the injection of the metal sodium particles is completed, continuously injecting Ar, wherein the Ar is used as a stirring gas to promote the removal of N, H gas impurities.
Further, in the step 4, the continuous blowing of Ar is carried out for 10-15 min, and after the blowing of Ar is finished, both the nitrogen content and the hydrogen content in the high-purity molten iron are less than 4ppm.
Further, in the step 4, the deoxidation product and the desulfurization product overflow in a gaseous state and enter a gas phase, and the gas phase is subjected to waste heat recovery and dust removal to obtain Ar and dust removal ash; returning the obtained Ar to an Ar powder spraying unit for recycling; and (3) sequentially carrying out water dissolving, lime replacement and filtering on the obtained fly ash, and recovering sodium hydroxide and gypsum.
Further, in the step 5, the purity of the high-purity cast iron is more than 99.9%.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
(1) In the aspect of raw material utilization, the invention takes the carbon-free sponge iron (namely the carbon-free low-sulfur low-phosphorus sponge iron) obtained by pure hydrogen reduction as a raw material, reduces the burden of removing sulfur and phosphorus in the smelting process, and avoids the smelting decarburization process and the reduction problem of phosphorus caused by the smelting decarburization process.
(2) The invention fully utilizes the high oxidizability (FeO content is 70%) of the smelting slag generated after the pure hydrogen sponge iron is smelted, realizes self-dephosphorization in the heating and smelting process, eliminates the reducing atmosphere generated in the decarbonization process, and has higher dephosphorization limit.
(3) The method adopts the metallic sodium particles as the deoxidizer to carry out synchronous coupling deoxidation and desulfurization on the molten iron, fully utilizes the low boiling point characteristics of the deoxidation product and the desulfurization product, promotes the deep progress of the deoxidation and desulfurization reaction in a vacuum state, and simultaneously avoids the generation of refining slag.
(4) According to the invention, the deoxidation and desulfurization products are subjected to water dissolving, lime displacement, filtering and other simple wet processes, so that full recovery can be realized, and the problem of stockpiling of the deoxidation and desulfurization products is avoided.
(5) The vacuum smelting system of the carbon-free sponge iron provided by the invention is a vacuum treatment device integrating smelting and refining, the vacuum induction furnace is arranged in the vacuum chamber, and refining is carried out in a vacuum state, so that the oxidation condition of high-oxygen molten iron in the processes of tapping and refining is avoided.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. 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 high purity smelting process diagram of carbon-free sponge iron;
FIG. 2 is a schematic diagram of a carbon-free sponge iron high-purity smelting device.
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 and not to limit its scope.
On one hand, the invention also provides a full vacuum smelting method of the carbon-free sponge iron, as shown in figure 1, the vacuum smelting method comprises the following steps:
step 1, adding a carbon-free sponge iron and lime flux into a vacuum induction furnace to be melted under a normal pressure state, controlling the mass ratio of lime to sponge iron within 5-6%, ensuring the dephosphorization effect, simultaneously avoiding excessive reduction of slag fluidity by lime to influence the dephosphorization effect, vacuumizing a vacuum chamber after materials are completely melted, melting sponge iron in a vacuum environment, and obtaining high-oxygen molten iron and slag after the melting process is completed;
step 2, opening a slag discharging valve, transferring the molten slag to a slag ladle, and transferring the high-oxygen molten iron to a refining unit through a tapping hole of the eccentric furnace;
step 3, taking Ar as a carrier gas and a stirring gas, introducing a metallic sodium particle deoxidizer into the high-oxygen molten iron of the refining unit by utilizing an Ar blowing powder spraying unit, stirring the molten iron by utilizing a stirring part, and synchronously deoxidizing, desulfurizing and degassing the high-oxygen molten iron in a vacuum environment to obtain high-purity molten iron;
step 4, casting the high-purity molten iron to obtain high-purity cast iron; and after the molten iron is cast, stopping vacuumizing, respectively opening an iron outlet door and a slag outlet door of the vacuum chamber, and pulling a slag ladle car and a cast iron car. Wherein the purity of the high-purity cast iron is more than 99.9 percent.
Compared with the prior art, the high-quality carbon-free sponge iron is added into the vacuum induction furnace together with the lime flux for melting, melting slag self-dephosphorization is completed in the melting process, after the melting is completed, high-oxygen molten iron is transferred to the ladle through tapping at the eccentric furnace bottom in a vacuum state, slag is tapped through the tapping valve after tapping, and slag is transferred to the slag ladle; the ladle is used as refining equipment, argon is used as carrier gas and stirring gas, the sodium metal particles are sprayed into the ladle for deep coupling synchronous deoxidation and desulfurization, and N, H gas impurities are removed; carrying out vacuum ingot casting on the molten iron to obtain high-purity cast iron; after waste heat recovery and dust removal are carried out on the refined flue gas, argon is recycled, and the sodium hydroxide and gypsum are recovered for utilization after water dissolving, lime replacement and filtering treatment are carried out on the dust removal ash.
In the step 1, the alkalinity of the molten slag generated in the melting process is controlled within the range of 3-3.5, so that the dephosphorization effect is ensured, and the fluidity of the molten slag is ensured; in addition, the phosphorus content of the high-oxygen molten iron produced in the melting process is <20ppm.
Specifically, the high-quality carbon-free sponge iron and a small amount of lime are loaded into the vacuum induction furnace under a normal pressure state, the alkalinity of molten slag is controlled within a range of 3-3.5, and the vacuum is pumped after the materials are completely melted. Because the oxidation degree of the melting slag of the carbon-free sponge iron is higher, the high-oxygen molten iron has good dephosphorization conditions, and the pure hydrogen sponge iron can carry out self-dephosphorization in the melting process to obtain the high-oxygen molten iron with the phosphorus content of less than 20ppm.
8FeO+2[P]+3CaO＝8Fe+Ca 3 (PO 4 ) 2 (1)
It is noted that after melting self-dephosphorization, high-oxygen molten iron is generated and is discharged through a taphole at the eccentric furnace bottom, and then the high-oxygen molten iron is transferred to a ladle, and because the ladle is positioned in a vacuum chamber, the ladle does not need to be slagging to prevent oxidation, and the surface of the high-oxygen molten iron can be in a naked state; and after tapping is finished, slag is discharged through a slag outlet, and the slag is transferred to a slag ladle.
In step 1, the carbon-free sponge iron is sponge iron obtained by reduction with pure hydrogen, and the prior art generally adopts a carbonaceous solid reducing agent or CO and H 2 Reducing the mixed gas to obtain the sponge iron.
Carbon-free sponge iron component and content
Figure BDA0003336713460000061
In the step 1, the high-oxygen molten iron refers to molten iron with high oxygen content, the oxygen content reaches 200-300 ppm, and the high-oxygen molten iron is relative to the blast furnace molten iron which is carbon saturated molten iron and does not contain oxygen.
In step 2, in order to prevent the slag from entering the ladle, 20-30% of high-oxygen molten iron is reserved in the vacuum induction furnace during the tapping process. In addition, in order to reduce the loss of molten iron in the deslagging process, the vacuum induction furnace produces primary molten slag after being smelted for multiple times, and 10% -15% of the molten slag is reserved in the vacuum induction furnace, so that the loss of the molten iron is avoided.
In the step 3, the method takes the metallic sodium particles as the deoxidizer and the argon gas as the carrier gas, and sprays the metallic sodium particles into the ladle molten pool for deoxidation, wherein the molar ratio of Na to the oxygen content of the molten iron in the deoxidizer is 1.05-1.1, so that the better deoxidation effect can be ensured, and the excessive consumption of Na can be avoided.
2Na+[O]＝Na 2 O (2)
The metallic sodium deoxidizes the molten iron, and the product Na is deoxidized 2 The O further reacts with the sulfur in the molten iron to form Na 2 SO 4 Deoxygenation is promoted by coupling with desulfurization, and Na 2 O and Na 2 SO 4 The oxygen-removing and desulfurizing agent is gaseous at high temperature, and the concentration of products of oxygen removal and desulfurization can be obviously reduced in a vacuum state, so that the oxygen removal and desulfurization reaction is promoted. After deoxidation and desulphurization, the oxygen content and the sulfur content in the high-purity molten iron are both less than 10ppm.
Na 2 O+[S]+3[O]＝Na 2 SO 4 (3)
In the step 3, after the injection of the metal sodium particles is finished, continuously injecting Ar serving as stirring gas to promote the removal of N, H gas impurities; and continuously blowing Ar for 10-15 min, and degassing to obtain high-purity molten iron with nitrogen content and hydrogen content less than 4ppm.
2[H]＝H 2 (4)
2[N]＝N 2 (5)
In the above step 3, the deoxygenated product Na is produced 2 O and desulfurization product Na 2 SO 4 Overflowing in a gaseous form and entering a gas phase, and performing waste heat recovery and dust removal on the gas phase to obtain Ar and dust removal ash; returning the obtained Ar to an Ar powder spraying unit for recycling; and (3) dissolving the obtained dedusting ash in water, replacing with lime and filtering to recover sodium hydroxide and gypsum.
Na 2 O+H 2 O＝2NaOH (6)
Na 2 SO 4 +H 2 O+CaO＝2NaOH+CaSO 4 (7)
And 4, casting the deoxidized, desulfurized and degassed high-purity molten iron in a vacuum state to obtain the high-purity cast iron. And after the molten iron is cast, stopping vacuumizing, respectively opening an iron outlet door and a slag outlet door of the vacuum chamber, and pulling a slag ladle car and a cast iron car.
It is also emphasized that the present invention has the following advantageous effects compared to the prior art:
(1) In the aspect of raw material utilization, the invention takes the carbon-free sponge iron (carbon-free low-sulfur low-phosphorus sponge iron, namely pure hydrogen reduced sponge iron) obtained by pure hydrogen reduction as a raw material, reduces the burden of removing sulfur and phosphorus in the smelting process, and avoids the smelting decarburization process and the reduction problem of phosphorus brought by the smelting decarburization process.
(2) The invention fully utilizes the high oxidizability (FeO content is 70%) of the pure hydrogen sponge iron smelting slag to realize self-dephosphorization in the heating and melting process, eliminates the reducing atmosphere generated in the decarburization process, and has higher dephosphorization limit.
(3) The method adopts the metallic sodium to carry out synchronous coupling deoxidation and desulfurization, fully utilizes the low boiling point characteristics of deoxidation product sodium oxide (the boiling point of 1275 ℃) and desulfurization product sodium sulfate (the boiling point of 1404 ℃), promotes the deep progress of deoxidation and desulfurization reactions in a vacuum state, and simultaneously avoids the generation of refining slag.
(4) According to the invention, the deoxidation and desulfurization products are subjected to water dissolving, lime displacement, filtering and other simple wet processes, so that full recovery can be realized, and the problem of stockpiling of the deoxidation and desulfurization products is avoided.
The smelting method of the carbon-free sponge iron provided by the invention can be realized by adopting a vacuum smelting system.
The invention also provides a full vacuum smelting system of the carbon-free sponge iron, which comprises a vacuum chamber, a vacuum induction unit, a refining unit and an Ar powder blowing unit; the vacuum induction unit and the refining unit are both arranged in the vacuum chamber; the Ar powder blowing and spraying unit is arranged outside the vacuum chamber; the vacuum induction unit, the refining unit and the Ar powder blowing unit are sequentially connected; the vacuum induction unit is used for smelting pure hydrogen reduced sponge iron; molten iron generated by smelting enters a refining unit, and an Ar blowing and powder spraying unit is used for spraying a deoxidizer into the molten iron in the refining unit; the refining unit carries out synchronous deoxidation, desulfurization and degassing treatment on the molten iron generated by the vacuum induction unit by using a deoxidizing agent; the vacuum chamber is provided with a smoke outlet.
Specifically, as shown in fig. 2, the full vacuum smelting system of the invention comprises a vacuum chamber, wherein a vacuum induction unit is arranged in the vacuum chamber, the vacuum induction unit is respectively connected with a slag ladle and a refining unit, and the refining unit is arranged below the vacuum induction unit; in addition, an Ar powder blowing unit arranged outside the vacuum chamber is connected with the refining unit through a pipeline, wherein the vacuum induction unit is used for smelting the pure hydrogen reduced sponge iron; the refining unit is used for deoxidizing, desulfurizing and degassing the high-oxygen molten iron generated by smelting; and the Ar powder blowing unit is used for spraying a deoxidizing agent into the refining unit.
The invention is characterized in that pure hydrogen is adopted in the shaft furnace to reduce high-quality oxidized pellets to obtain the low-sulfur low-phosphorus carbon-free sponge iron, namely the pure hydrogen reduced sponge iron.
In the prior art, the common process flow for preparing high-purity iron is as follows: ion exchange method + solvent extraction method → electrolytic refining → cold crucible melting → zone melting. The main problems of the existing high-purity iron production are high production cost, low productivity and incapability of meeting the gap of the market for high-purity iron in a short time.
Compared with the prior art, the vacuum smelting system for pure hydrogen reduction of sponge iron provided by the invention has the advantages that the vacuum induction unit and the refining unit are arranged in the vacuum chamber, namely, the smelting and the refining processes are integrally designed, the vacuum induction furnace is arranged in the vacuum chamber, and the refining process is carried out in a vacuum state, so that the oxidation condition of molten iron in the tapping and refining processes is avoided.
The air smelting system also comprises a slag ladle which is arranged in the vacuum chamber and is communicated with the vacuum induction unit.
In order to better smelt the pure hydrogen reduced sponge iron, the vacuum induction unit comprises a vacuum induction furnace, wherein a slag outlet is formed in the middle of the vacuum induction furnace and is communicated with a slag ladle; an eccentric furnace is arranged on one side of the bottom of the vacuum induction furnace, and the vacuum induction furnace is communicated with the eccentric furnace; a taphole is arranged on the eccentric furnace; the refining unit comprises a ladle which is arranged below the tap hole and communicated with the ladle through the tap hole.
Specifically, the vacuum induction unit comprises a vacuum induction furnace, wherein a slag outlet is arranged in the middle position (slag layer position) of the vacuum induction furnace and is communicated with a slag ladle; after smelting is finished, when slag needs to be discharged, the slag can be discharged by opening the slag discharging valve. The vacuum chamber is also provided with an iron outlet door and a slag outlet door; the tapping door is used for the entrance and exit of the cast iron car; the slag outlet door is used for the entrance and exit of the slag ladle car.
It should be noted that the vacuum induction unit of the invention sequentially comprises a reducing flue gas accommodating layer, a slag accommodating layer and a molten iron accommodating layer from top to bottom; the slag containing layer is a slag layer; the molten iron containing layer is a molten iron layer. And a slag hole is formed in the slag containing layer in the middle of the vacuum induction furnace and communicated with the slag ladle. In order to conveniently convey the generated high-purity cast iron and the slag out of the vacuum chamber, the vacuum chamber is provided with an iron outlet door and a slag outlet door; the tapping door is used for the entrance and exit of the cast iron car; the slag outlet door is used for the entrance and exit of the slag ladle car. And a slag discharging valve is arranged on the vacuum induction furnace, and the slag is discharged through the slag discharging valve. In addition, the vacuum chamber of the invention is also provided with a smoke outlet, and smoke generated by the vacuum induction furnace is led out through the smoke outlet.
It should be noted that the Ar powder injection unit of the invention uses Ar as carrier gas and stirring gas and is used for injecting a deoxidizer into a high-oxygen ladle.
In order to spray the deoxidizer into the molten iron more uniformly, the Ar blowing and powder spraying unit comprises a deoxidizer hopper and an argon source; an argon source is communicated with the deoxidizer hopper through a first branch pipe; the deoxidizer hopper is communicated with the ladle through a second branch pipe; the first branch pipe is provided with a flow control valve and a pass-stop valve; a discharging valve is arranged on the second branch pipe; the bottom of the deoxidizer hopper is provided with a feed opening, and the second branch is communicated with the ladle through the feed opening.
Specifically, the deoxidizer adopted by the invention is metallic sodium particles, the metallic sodium particles are placed in a closed deoxidizer hopper, a top cover is arranged at the top of the deoxidizer hopper, and when the metallic sodium particles need to be placed in the deoxidizer hopper, the operation can be carried out by opening the top cover; in addition, the top of the deoxidizer hopper is also provided with an argon gas inlet, a first branch pipe connected with an argon gas source (an argon gas tank) enters the deoxidizer hopper through the argon gas inlet, and in addition, the first branch pipe is provided with a flow control valve which is used for controlling the flow of argon gas; and the first branch pipe is also provided with a through-stop valve, when the through-stop valve is opened, argon can be conveyed into the deoxidizer hopper through the argon tank, and when the through-stop valve is closed, the conveying of argon into the deoxidizer hopper is stopped.
The bottom of the deoxidizer hopper is provided with a feed opening, a second branch is communicated with the ladle through the feed opening, a feed control valve is arranged on the second branch, the feed control valve is opened, and the metallic sodium particles enter the ladle through a second branch pipe.
In order to enhance the deoxidation effect and further increase the contact area of the deoxidizer and the molten iron, the deoxidizer hopper is arranged above the ladle; the top of the ladle is provided with an argon gas blowing opening, the first end of the second branch pipe is communicated with the deoxidizer hopper, the second branch pipe penetrates through the argon gas blowing opening, the second end of the second branch pipe extends into the molten iron, and the second end of the second branch pipe is located at 1/3 of the height of the ladle.
Compared with the prior art, the argon source is communicated with the deoxidizer hopper through the first branch pipe; the deoxidizer hopper is communicated with the ladle through a second branch pipe; the bottom of the deoxidizer hopper is provided with a feed opening, and the second branch is communicated with the ladle through the feed opening. When a deoxidizer needs to be sprayed into the ladle, the argon gas through-stop valve is opened, the argon gas enters the deoxidizer hopper through the first branch pipe, the deoxidizer (metal sodium particles) in the deoxidizer hopper is sprayed into the molten iron from the bottom of the ladle by utilizing the argon gas, the argon gas gradually flows towards the top of the ladle after entering the bottom of the ladle, when the argon gas floats upwards, the deoxidizer can be in more uniform contact with the molten iron, the defect that the deoxidizing effect is poor due to the fact that the deoxidizer is attached to slag when the molten iron is discharged from the top of the ladle is avoided, the deoxidizer entering the ladle can completely participate in reaction, and accurate control of molten iron components is facilitated.
In order to further enhance the deoxidation effect and improve the deoxidation rate, the second branch pipe is a rotatable hollow round rod, and argon and a deoxidizer are injected into molten iron through the aperture of the rotatable hollow round rod; the bottom surface of the rotatable hollow round rod is provided with a stirring component which is used for stirring molten iron, so that the contact area of the molten iron and the deoxidizer is increased.
Compared with the prior art, the rotatable hollow round rod can rotate, so that a certain stirring effect can be generated on molten iron, and the deoxidation of the molten iron is promoted. It should be noted that the motor is arranged at the top of the ladle, the motor drives the rotatable hollow round rod to rotate through the transmission belt, when the rotatable hollow round rod rotates, the stirring component plays a role in stirring molten iron, in addition, the argon sprayed into the molten iron can also enable the molten iron to flow to a certain extent, and finally the deoxidation effect of the molten iron is improved.
In order to further enhance the deoxidation effect, the stirring component comprises a first U-shaped blade and a second U-shaped blade, wherein the first U-shaped blade and the second U-shaped blade are opposite in installation direction and are mutually embedded; the stirring member is obliquely disposed on the bottom surface of the rotatable hollow cylindrical rod.
Similarly, in order to further enhance the deoxidation effect, the stirring member of the present invention comprises a first arcuate blade and a second arcuate blade which are disposed in parallel with each other and on the bottom surface of the rotatable hollow cylindrical rod.
The full vacuum smelting system of the carbon-free sponge iron provided by the invention is a vacuum treatment device integrating smelting and refining, wherein the smelting and refining are carried out in a vacuum state, the oxidation condition of molten iron in the tapping and refining processes is avoided, and the use of refining slag is eliminated.
Example 1
10kg of sponge iron and quicklime (CaO) are mixed according to the mass ratio of 1: 0.042-0.069, then the mixture is added into a vacuum induction furnace with the molten iron capacity of 30kg for smelting, the binary alkalinity of the mixture formed by the sponge iron and the quicklime (CaO) is controlled within the range of 2.5-4.0, and the components of the sponge iron are shown in Table 1.
TABLE 1 sponge iron composition
Sponge iron component TFe MFe FeO CaO SiO 2 MgO Al 2 O 3 P S
Content (%) 94.133 87.614 9.313 0.314 1.805 0.793 1.174 0.236 0.003
After the slag and iron are completely separated, the molten iron is cast into ingots in a vacuum state through an iron outlet at the lower part of the induction furnace, and the phosphorus content of the ingots is measured by a chemical analysis method, and the results are shown in table 2. It can be seen that the slag alkalinity has a remarkable influence on the dephosphorization effect of the molten iron, and when the binary alkalinity is controlled to be between 3 and 3.5, the phosphorus content of the molten iron can be controlled to be within 20ppm.
TABLE 2 influence of slag basicity on dephosphorization limit of molten iron
Alkalinity of 2.5 3.0 3.5 4.0
Phosphorus content (%) 0.006 0.002 0.0016 0.0014
Example 2
Melting the iron ingot with the phosphorus content of 0.0016 percent in the example 1 in a vacuum induction furnace, and after the iron ingot is completely melted, spraying metallic sodium particles by taking argon as carrier gas to deoxidize and desulfurize the molten iron, wherein the molar ratio of the sprayed Na to O in the molten iron is 1.0-1.2, the argon flow is 6.5L/min, and the duration is 1min; wherein, the metal Na is added at one time in the initial stage, and the molten iron is stirred by a stirring component. As shown in Table 3, it can be seen that when the Na/O ratio is controlled to 1.05 or more, the oxygen and sulfur contents of the molten iron are both less than 10ppm, and when the Na/O ratio exceeds 1.1, the oxygen and sulfur contents of the molten iron hardly change, and the Na/O ratio is preferably in the range of 1.05 to 1.1 in order to reduce the consumption of metallic Na.
TABLE 3 influence of Na/O ratio on the deoxidation and desulfurization limits of molten iron
Figure BDA0003336713460000131
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Example 3
Melting the iron ingot with the Na/O ratio of 1.1 and removed oxygen and sulfur in the embodiment 2 in a vacuum induction furnace, continuously blowing Ar as stirring gas to promote the removal of N, H gas impurities in molten iron after the iron ingot is completely melted, and stirring the molten iron by using a stirring part; the time for continuously blowing Ar is 5-20 min, the nitrogen and hydrogen contents of the degassed molten iron are determined by vacuum ingot casting and chemical analysis, and the results are shown in Table 4, it can be seen that when the argon blowing stirring time is more than 10min, the nitrogen and hydrogen contents of the molten iron are both lower than 4ppm, and since the change of the nitrogen and hydrogen contents is small after the argon blowing stirring time exceeds 15min, in order to ensure the treatment efficiency and reduce the argon consumption, the argon blowing stirring time is preferably 10-15 min.
TABLE 4 influence of Na/O ratio on the deoxidation and desulfurization limits of molten iron
Figure BDA0003336713460000132
Figure BDA0003336713460000141
Example 4
10kg of sponge iron with the components shown in the table 1 is added with quick lime and then added into a vacuum induction furnace for melting, the binary alkalinity of a slag phase is controlled to be 3.5, slag is removed in a vacuum state after complete melting, complete removal of molten slag is realized, and pollution to molten iron caused by rephosphorization in the refining and deoxidation process is avoided; spraying sodium metal particles into a molten iron molten pool by using argon as carrier gas, controlling the Na/O ratio to be 1.1, controlling the argon flow to be 6.5L/min, controlling the argon blowing duration to be 10min, and stirring the molten iron by using a stirring component; after the argon blowing was completed, ingots were cast under vacuum, and the composition of the ingots was determined by chemical analysis, as shown in table 5. It can be seen that the chemical composition of the iron ingot meets the requirement of high-purity iron, the sum of S + P + N + O + H content is lower than 30ppm, and the carbon content is zero, so that the production requirement of high-end materials is met.
TABLE 5 ingot chemical composition
Composition (I) TFe O N H P S Others
Content (%) 99.983 0.0006 0.0003 0.0003 0.0014 0.0002 0.014
In conclusion, the carbon-free sponge iron (carbon-free low-sulfur-phosphorus sponge iron) is prepared by reducing high-quality oxidized pellets with pure hydrogen, the decarburization step is eliminated, and the melting dephosphorization is realized by adopting lime flux in the smelting process of the carbon-free sponge iron to obtain the dephosphorization slag; sodium-based synchronous deep deoxidation, desulfurization and degassing are adopted in the refining process, so that the removal efficiency of impurity elements is greatly improved, and the smelting slag amount is reduced.
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 (5)

1. The smelting method of the carbon-free sponge iron is characterized by comprising the following steps:
step 1, performing shaft furnace reduction on the oxidized pellets by using hydrogen in a shaft furnace to obtain carbon-free sponge iron;
step 2, adding the carbon-free sponge iron and lime flux into a vacuum induction furnace under a normal pressure state, heating and melting, completing self-dephosphorization of molten slag in the melting process, and obtaining high-oxygen molten iron and molten slag after the materials are completely melted; the FeO content in the high-oxygen molten iron is 70 percent;
the mass ratio of the lime flux to the sponge iron is controlled within the range of 5-6%;
the self-dephosphorization process of the molten slag comprises the following steps:
8FeO+2[P]+3CaO＝8Fe+Ca 3 (PO 4 ) 2 (1)；
3, transferring the molten slag from the vacuum induction furnace to a slag ladle in a vacuum state, and transferring the high-oxygen molten iron to a refining unit through a taphole of the eccentric furnace;
step 4, using Ar as carrier gas and stirring gas, spraying a deoxidizing agent into the high-oxygen molten iron of the refining unit by utilizing an Ar powder spraying unit, stirring the molten iron by utilizing a stirring component, and synchronously deoxidizing, desulfurizing and degassing the high-oxygen molten iron in a vacuum environment to obtain high-purity molten iron;
the deoxidizer is metallic sodium particles; the molar ratio Na/O of the Na content in the metal sodium particles to the oxygen content in the high-oxygen molten iron is 1.05-1.1;
the deoxidation process comprises the following steps:
2Na+[O]＝Na 2 O (2)；
metallic sodium pairDeoxidizing molten iron, and obtaining a deoxidized product Na 2 The O further reacts with the sulfur in the molten iron to form Na 2 SO 4 (ii) a Deoxygenated product Na 2 O and desulfurization product Na 2 SO 4 Both overflow in gaseous form and enter the gas phase; performing waste heat recovery and dust removal on the gas phase to obtain Ar and dust removal ash; returning the obtained Ar to the Ar powder spraying unit for cyclic utilization; dissolving the obtained fly ash in water, replacing with lime and filtering to recover sodium hydroxide and gypsum;
Na 2 O+H 2 O＝2NaOH (6)
Na 2 SO 4 +H 2 O+CaO＝2NaOH+CaSO 4 (7)
after the injection of the metal sodium particles is finished, continuously injecting Ar, wherein the Ar is used as stirring gas to promote the removal of N, H gas impurities;
after synchronous deoxidation, desulfurization and degassing, the oxygen content and the sulfur content in the high-purity molten iron are both less than 10ppm;
step 5, casting the high-purity molten iron in a vacuum environment, and stopping vacuumizing after casting is finished to obtain high-purity cast iron; the purity of the high-purity cast iron is more than 99.9 percent;
the vacuum induction furnace and the refining unit are arranged in a vacuum chamber, and the refining unit is arranged below the vacuum induction furnace; the Ar blowing powder spraying unit is arranged outside the vacuum chamber; the vacuum induction furnace, the refining unit and the Ar powder blowing unit are sequentially connected; the vacuum chamber is provided with a smoke outlet;
the vacuum induction furnace sequentially comprises a reducing flue gas containing layer, a slag containing layer and a molten iron containing layer from top to bottom; the slag containing layer is internally provided with a slag layer; a molten iron layer is arranged in the molten iron containing layer;
a slag outlet is arranged on the vacuum induction furnace, a slag ladle is also arranged in the vacuum chamber, and the slag outlet is communicated with the slag ladle; the bottom of the vacuum induction furnace is provided with an eccentric furnace communicated with the vacuum induction furnace; the bottom of the eccentric furnace is provided with a tap hole;
molten iron produced by smelting in the vacuum induction furnace enters the refining unit, and the Ar powder blowing unit is used for spraying a deoxidizer into the molten iron in the refining unit; the refining unit carries out synchronous deoxidation, desulfurization and degassing treatment on the molten iron generated by the vacuum induction furnace by using the deoxidizer to obtain high-purity molten iron, and the high-purity molten iron is cast in vacuum to obtain high-purity cast iron;
the refining unit comprises a ladle which is arranged below a tapping hole of the eccentric furnace and communicated with the eccentric furnace;
the Ar blowing powder spraying unit comprises a deoxidizer hopper and an argon source; the argon source is communicated with the deoxidizing agent hopper through a first branch pipe; the deoxidizer hopper is communicated with the foundry ladle through a second branch pipe; the first branch pipe is provided with a flow control valve and a pass-stop valve; a blanking valve is arranged on the second branch pipe; the bottom of the deoxidizer hopper is provided with a feed opening, and the second branch pipe is communicated with the ladle through the feed opening;
the second branch pipe is a rotatable hollow round rod, and argon and a deoxidizer are injected into molten iron through the central aperture of the rotatable hollow round rod; the bottom surface of the rotatable hollow round rod is provided with a stirring component, and the stirring component is used for stirring molten iron so as to increase the contact area of the molten iron and the deoxidizer.
2. The method for smelting carbon-free sponge iron as claimed in claim 1, wherein in the step 2, the basicity of the slag is 3 to 3.5; the high-oxygen molten iron has a phosphorus content of <20ppm.
3. The method for smelting carbon-free sponge iron as claimed in claim 1, wherein in the step 2, 20-30% of high-oxygen molten iron is retained in the vacuum induction furnace during tapping.
4. The method for smelting carbon-free sponge iron as claimed in claim 1, wherein in step 2, the vacuum induction furnace is used for melting for a plurality of times, then the molten slag is poured once, and 10% -15% of the molten slag is remained in the vacuum induction furnace.
5. The method for smelting carbon-free sponge iron as claimed in claim 1, wherein in the step 4, the time for continuously blowing Ar is 10-15 min, and after the blowing of Ar is finished, the nitrogen content and the hydrogen content in the high-purity molten iron are both less than 4ppm.
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