A method for separating iron and phosphorus from steel slag and then oxidizing it to prepare phosphorus-rich slag

Abstract

The present invention provides a method for preparing phosphorus-rich slag by separating iron and phosphorus from steel slag and then oxidizing it. The method comprises the following steps: S1: charging the molten steel slag discharged from converter steelmaking into a closed DC electric furnace, and adding a reducing agent and a modifier at the same time to obtain high-phosphorus molten iron; S2: charging the high-phosphorus molten iron obtained by reducing S1 into an induction melting furnace, blowing in oxygen, adding a flux and a coolant at the same time, blowing in an inert gas from the bottom of the furnace for stirring, completing the separation of iron and phosphorus from the steel slag, and obtaining phosphorus-rich slag at the same time. The present invention produces a high reduction rate and a high thermal efficiency by using a low oxygen potential in the closed DC electric furnace, and a low exhaust volume. The DC electric furnace has the characteristics of promoting the flow in the slag, reducing the electrode strength, and being easy to operate. The present invention is of great significance to the recycling of large-scale solid waste resources in metallurgy and energy conservation.

Description

[Technical field]

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for separating iron and phosphorus from steel slag and then oxidizing it to prepare phosphorus-rich slag. [Background technology]

[0002] As steel production continues to rise, the amount of slag discharged also continues to increase.

[0003] The internal circulation of steel smelting and the preparation of building materials are the two main ways of converting and utilizing steel slag. In terms of internal circulation, the harmful phosphorus element in steel slag limits its large-scale and efficient conversion and utilization. In terms of preparing raw materials for building materials, the harmful phosphorus element and unstable iron-containing substances make it known as "inferior cement clinker".

[0004] During the converter steelmaking process, a large amount of high-temperature molten slag is produced, with a temperature of up to about 1600℃ and a specific heat capacity of about 1.2J / (kg·℃). The sensible heat contained in each ton of slag is approximately equivalent to the heat generated by the complete combustion of 50-70kg of standard coal. If the sensible heat of this part of the slag can be recovered, the total energy saving will reach 6 million tons of standard coal. Due to cost issues, the sensible heat utilization rate of slag is very low, resulting in a huge waste of thermal energy. Making full use of the sensible heat of slag is of great significance to achieving efficient utilization of resources and energy and reducing energy conservation and consumption in steel enterprises.

[0005] High-phosphate ore is an extremely difficult iron ore resource to process. my country has about 3 to 5 billion tons of reserves, mainly distributed in Hunan, Hubei, Guangxi, Guizhou and other regions. This iron ore has a high phosphorus content (0.4% to 1.8%) and a low iron grade (35% to 50%). The phosphorus in the iron ore is stored in the collophanite and mixed with the iron oxide-rich oolitic chlorite to form a concentric layered oolide structure. Due to the unique oolide structure in high-phosphate ore and the complex intercalation relationship between phosphorus-containing gangue minerals and iron minerals, when conventional mineral processing methods such as gravity separation, magnetic separation, and flotation are used to directly process high-phosphate ore, although iron concentrate with a certain iron grade can be obtained, it is very difficult to effectively reduce the phosphorus content in the iron concentrate. When using methods such as magnetic roasting and chemical leaching to treat oolide iron ore for iron extraction and dephosphorization, there are also problems such as poor dephosphorization effect, poor product quality, low iron recovery rate, high cost and severe environmental pollution.

[0006] As a slag reduction process, various forms such as converter type, electric furnace type, and vertical furnace type have been proposed. Among them, the present invention selects a closed DC electric furnace to reduce steel slag and high-phosphate ore. This process was developed by MINTEK in South Africa and is mainly used for ferroalloy manufacturing. Unlike the dissolving type general electric furnace, there is no air intrusion, and it does not form a filling layer of solid raw materials like the submerged arc furnace of the general reduction electric furnace. The sealed furnace has the following characteristics: 1) High reduction rate due to the reduction of oxygen potential in the furnace; 2) High thermal efficiency due to low exhaust volume; 3) Low flow rate gas in the furnace can make the powder raw material be thrown upward. In addition, the DC electric furnace has the characteristics of promoting the flow in the slag, reducing the electrode strength, and easy operation.

[0007] In view of this, the present invention uses a method for separating iron and phosphorus from steel slag and then reoxidizing it to prepare phosphorus-rich slag. [Summary of the invention]

[0008] In view of this, the present invention provides a method for separating iron and phosphorus from steel slag and then oxidizing it to prepare phosphorus-rich slag, so as to overcome the difficulties in the prior art in recycling steel slag, recycling steel slag waste heat, and developing and utilizing high-phosphate mines.

[0009] In one aspect, the present invention provides a method for separating iron and phosphorus from steel slag and then oxidizing it to prepare phosphorus-rich slag, the method comprising the following steps:

[0010] S1: The molten steel slag discharged from converter steelmaking is charged into a closed DC electric furnace, and a reducing agent and a modifier are added to obtain high-phosphorus molten iron;

[0011] S2: The high-phosphorus molten iron obtained by reducing S1 is charged into an induction melting furnace, oxygen is blown in, and flux and coolant are added at the same time. Inert gas is blown in from the bottom of the furnace for stirring to complete the separation of iron and phosphorus from the steel slag, and phosphorus-rich slag is obtained at the same time.

[0012] According to the above aspects and any possible implementation, an implementation is further provided, wherein S1 specifically includes:

[0013] S11: charging molten iron into a closed DC electric furnace and leaving a layer of reducing slag;

[0014] S12: charging the molten steel slag at 1500°C to 1700°C discharged from the converter steelmaking process into the holding furnace, and slowly adding the molten steel slag into the closed DC electric furnace by tilting;

[0015] S13: continuously feeding the reducing agent and the modifying agent into the closed DC electric furnace through a raw material feeding pipe arranged on the furnace cover;

[0016] S14: When the reduction treatment in the closed DC electric furnace is completed, the reduced slag is discharged from the slag outlet. As the molten iron increases, when the molten iron level approaches the slag outlet, the high-phosphorus molten iron obtained by the reduction is discharged from the iron outlet.

[0017] According to the aspects and any possible implementation methods described above, an implementation method is further provided, wherein the S13 is calculated based on the grade of steel slag and high phosphate ore, and the ratio of carbon to iron is in the range of 150 to 300 kg / tFe; the amount of high phosphate ore added is 1 to 50% of the total mass of the steel slag, the amount of SiO2 added is 15 to 25% of the total mass of the steel slag, and the amount of Al2O3 added is 5 to 15% of the total mass of the steel slag.

[0018] According to the aspects described above and any possible implementation, an implementation is further provided, wherein the reducing agent is coke, and the modifier includes high-phosphate ore, SiO2 and Al2O3, the high-phosphate ore contains 70% hematite, 2.5% apatite and 10% quartz, 40-50% iron and 0.4-1% phosphorus.

[0019] According to the aspects described above and any possible implementation method, an implementation method is further provided, wherein the target composition of the steel slag after reduction in S14 is basicity (CaO) / (SiO2)=1.0~1.2, basicity (Al2O3)=10~12%, and the composition of the steel slag after reduction is the same as that of blast furnace slag.

[0020] According to the above aspects and any possible implementation manner, an implementation manner is further provided, wherein S2 specifically includes:

[0021] S21: The high-phosphorus molten iron obtained by reduction is charged into the induction melting furnace, and then the molten iron is heated from the spray gun at a speed of 30-60Nm 3 Blow oxygen at a rate of / h to carry out dephosphorization treatment;

[0022] S22: adding flux and coolant from above the induction melting furnace;

[0023] S23: Blow 2-10 Nm from the porous plug at the bottom of the induction melting furnace 3 / h of argon is used as stirring gas to obtain phosphorus-rich slag.

[0024] According to the above aspects and any possible implementation manner, there is further provided an implementation manner, wherein the flux includes quicklime, dolomite and silica sand.

[0025] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the furnace temperature during stirring in S23 is set between 1200° C. and 1600° C.

[0026] According to the aspects and any possible implementations described above, an implementation is further provided, wherein the slag obtained by dephosphorization in S23 has a P2O5 content of 10-20%, the molten iron after dephosphorization has a P2O5 content of less than 0.1%, and the molten iron is returned to the converter for steelmaking.

[0027] Compared with the prior art, the present invention can achieve the following technical effects:

[0028] 1. The closed DC furnace has a low oxygen potential in the furnace, resulting in a high reduction rate, and a low exhaust volume, resulting in high thermal efficiency. The low flow rate of gas in the furnace can make the powder raw materials flow upward. In addition, the DC furnace has the characteristics of promoting the flow of slag, reducing electrode strength, and easy operation;

[0029] 2. In a closed DC electric furnace, since the steel slag contains a large amount of alkaline substances such as calcium oxide, the steel slag will absorb part of the CO2 gas produced after reduction and play a role in fixing the CO2;

[0030] 3. The present invention is of great significance to the recycling of bulk metallurgical solid waste resources and energy conservation.

[0031] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time.

Brief Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a flow chart of separation of iron and phosphorus from steel slag and reoxidation preparation provided by one embodiment of the present invention;

[0034] Figure 2 is a system schematic diagram of a closed DC electric furnace provided by an embodiment of the present invention;

[0035] Figure 3 It is a system schematic diagram of a smelting induction furnace provided by one embodiment of the present invention.

[0036] Among them, in the figure:

[0037] 1-blast furnace, 2-molten iron pretreatment device, 3-converter, 4-slag holding furnace, 5-tailings recovery device, 6-induction melting furnace, 7-closed DC electric furnace, 8-air burner, 9-oxygen nozzle, 10-feeder, 11-slag outlet, 12-iron outlet, 13-holding furnace, 14-electrode, 15-sliding sleeve, 16-high-temperature slag inlet, 17-oxygen spray gun, 18-argon bottom blowing porous brick. [Specific implementation method]

[0038] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0041] The present invention provides a method for separating iron and phosphorus from steel slag and then oxidizing it to prepare phosphorus-rich slag, the method comprising the following steps:

[0042] S1: The molten steel slag discharged from converter steelmaking is charged into a closed DC electric furnace, and a reducing agent and a modifier are added to obtain high-phosphorus molten iron;

[0043] S2: The high-phosphorus molten iron obtained by reducing S1 is charged into an induction melting furnace, oxygen is blown in, and flux and coolant are added at the same time. Inert gas is blown in from the bottom of the furnace for stirring to complete the separation of iron and phosphorus from the steel slag, and phosphorus-rich slag is obtained at the same time.

[0044] The S1 specifically includes:

[0045] S11: charging molten iron into a closed DC electric furnace and leaving a layer of reducing slag;

[0046] S12: charging the molten steel slag at 1500°C to 1700°C discharged from the converter steelmaking process into the holding furnace, and slowly adding the molten steel slag into the closed DC electric furnace by tilting;

[0047] S13: continuously feeding the reducing agent and the modifying agent into the closed DC electric furnace through a raw material feeding pipe arranged on the furnace cover;

[0048] S14: When the reduction treatment in the closed DC electric furnace is completed, the reduced slag is discharged from the slag outlet. As the molten iron increases, when the molten iron level approaches the slag outlet, the high-phosphorus molten iron obtained by the reduction is discharged from the iron outlet.

[0049] The S13 is calculated based on the grade of steel slag and high phosphate ore, and the ratio of carbon to iron is in the range of 150-300 kg / tFe; the amount of high phosphate ore added is 1-50% of the total mass of steel slag, the amount of SiO2 added is 15-25% of the total mass of steel slag, and the amount of Al2O3 added is 5-15% of the total mass of steel slag. The reducing agent is coke, and the modifier includes high phosphate ore, SiO2 and Al2O3. The high phosphate ore contains 70% hematite, 2.5% apatite and 10% quartz, 40-50% iron and 0.4-1% phosphorus. The target composition of the steel slag after reduction in the S14 is basicity (CaO) / (SiO2)=1.0-1.2, basicity (Al2O3)=10-12%, and the steel slag after reduction has the same composition as blast furnace slag.

[0050] The S2 specifically includes:

[0051] S21: The high-phosphorus molten iron obtained by reduction is charged into an induction smelting furnace, and then oxygen is blown into the lance at a rate of 30 to 60 Nm3 / h for dephosphorization treatment;

[0052] S22: adding flux and coolant from above the induction melting furnace;

[0053] S23: 2 to 10 Nm3 / h of argon is blown into the bottom of the induction melting furnace as a stirring gas through a porous plug to obtain phosphorus-rich slag.

[0054] The flux includes quicklime, dolomite and silica sand. The furnace temperature during stirring in S23 is set between 1200°C and 1600°C. The slag obtained by dephosphorization in S23 has 10-20% P2O5, and the molten iron after dephosphorization has a P2O5 content of less than 0.1%, and the molten iron is returned to the converter for steelmaking.

[0055] The method of the present invention is carried out based on the following system: Figure 1 As shown, the system includes a blast furnace 1, a molten iron pretreatment device 2, a converter 3, a slag holding furnace 4, an induction melting furnace 6, a closed DC electric furnace 7 and a tailings recovery device 5. The blast furnace 1 is connected to the converter 3 through the molten iron pretreatment device 2. One end of the slag holding furnace 4 is simultaneously connected to the converter 3 and the molten iron pretreatment device 2, and the other end is connected to the closed DC electric furnace 7. The bottom of the closed DC electric furnace 7 is connected to the induction melting furnace 6. The bottom of the induction melting furnace 6 is connected to the converter 3. The slag holding furnace 4 and the induction melting furnace 6 are both connected to the tailings recovery device 5.

[0056] like Figure 2As shown, the closed DC electric furnace 7 includes a sealed furnace body, an electrode 14 and a holding furnace 13, one end of the holding furnace 13 is connected to the top of the sealed furnace body, and the other end is connected to the slag holding furnace 4, one end of the electrode 14 is arranged in the sealed furnace body, and the other end is connected to the power supply outside the sealed furnace body, a feeder 10 is also arranged above the sealed furnace body, and an iron outlet 12 and a slag outlet 11 are respectively arranged on both sides of the sealed furnace body, the iron outlet 12 is 200mm lower than the slag outlet 11, and the iron outlet 12 is connected to the induction smelting furnace 6, and an air combustion port and an oxygen port are arranged on the holding furnace 13, the air combustion port is connected to the air burner 8, and the oxygen port is connected to the oxygen nozzle 9, and a high-temperature slag inlet is also arranged above the holding furnace 13, and the high-temperature slag inlet is connected to the slag holding furnace 4. A sliding sleeve 15 is also arranged between the slag holding furnace 4 and the tailings recovery device 5.

[0057] like Figure 3 As shown, an oxygen lance 17 and a feeder 10 are simultaneously provided above the induction melting furnace 6 , and an argon bottom-blown porous brick 18 is provided at the bottom of the induction melting furnace 6 .

[0058] The smelting process of the method of the present invention is specifically as follows:

[0059] (1) The molten slag at 1500-1700° C. discharged from the converter 3 during steelmaking is charged into a closed DC electric furnace 7, and a carbonaceous reducing agent and high phosphate ore, SiO2 and Al2O3 as modifiers are added into the reduction furnace, wherein the carbonaceous reducing agent is calculated based on the grade of the slag (TFe) and the high phosphate ore, and the ratio of carbon to iron is in the range of 150-300 kg / tFe, the amount of high phosphate ore added is 1-50% of the total mass of the slag, the amount of SiO2 added is 15-25% of the total mass of the slag, and the amount of Al2O3 added is 5-15% of the total mass of the slag.

[0060] (2) The high-phosphorus molten iron obtained by the reduction step above is charged into an induction melting furnace 6, and oxygen is blown in from a lance, while quicklime, dolomite, and silica sand are added from above as flux, and iron ore is used as a coolant. In addition, argon is blown in from a porous plug at the bottom of the furnace as a stirring gas.

[0061] The closed DC furnace 7 has a low oxygen potential in the furnace, resulting in a high reduction rate, a low exhaust volume, and a high thermal efficiency. The low flow rate of gas in the furnace allows the powder raw material to be fed upward. A holding furnace 13 for storing slag is arranged above the closed DC furnace 7. The high-phosphate ore contains 40-50% iron, mainly in the form of hematite; contains 0.4-1% phosphorus, mainly in the form of apatite; the other main gangue is quartz, with a content between 10-15%. The carbonaceous reducing agent is coke.

[0062] The target composition of the reduced slag is (CaO) / (SiO2)=1.0-1.2, (Al2O3)=10-12%, which is the same as the slag of blast furnace 1. The spray gun in the smelting furnace is 30-60Nm 3 Blow oxygen at a rate of / h. Blow 2~10Nm 3 / h argon is used as stirring gas. The temperature in the induction melting furnace 6 is set between 1200 and 1600°C. The molten iron [P] after dephosphorization is less than 0.1% and is returned to the converter 3 for steelmaking. The phosphorus-rich slag (P2O5) obtained by dephosphorization is 10-20% and is used to produce high-phosphate fertilizer.

[0063] Example 1

[0064] The 1400℃ molten slag discharged from converter steelmaking is charged into a closed DC electric furnace, and a carbonaceous reducing agent and high phosphate ore, SiO2 and Al2O3 as modifiers are added into the reduction furnace. The coke is calculated according to the grade of slag (TFe) and high phosphate ore, the ratio of carbon to iron is 175kg / tFe, the amount of high phosphate ore added is 15% of the total mass of slag, the amount of SiO2 added is 25% of the total mass of slag, and the amount of Al2O3 added is 10% of the total mass of slag. The reduced slag is the same as blast furnace slag, and the high phosphorus molten iron obtained by reduction is charged into an induction melting furnace, and then the spray gun in the furnace is heated at 30Nm 3 Oxygen is blown in at a rate of / h, and quicklime, dolomite, and silica sand are added from above as flux, and iron ore is used as coolant. In addition, 4Nm 3 / h of argon was used as stirring gas and the furnace temperature was set at 1300°C.

[0065] Example 2

[0066] The 1450℃ molten slag discharged from converter steelmaking is charged into a closed DC electric furnace, and a carbonaceous reducing agent and high phosphate ore, SiO2 and Al2O3 as modifiers are added into the reduction furnace. The coke is calculated according to the grade of slag (TFe) and high phosphate ore, the ratio of carbon to iron is 250kg / tFe, the amount of high phosphate ore added is 20% of the total mass of slag, the amount of SiO2 added is 21% of the total mass of slag, and the amount of Al2O3 added is 12% of the total mass of slag. The reduced slag is the same as blast furnace slag, and the high phosphorus molten iron obtained by reduction is charged into an induction melting furnace, and then the spray gun in the furnace is heated at 40Nm 3 Oxygen is blown in at a rate of / h, and quicklime, dolomite, and silica sand are added from above as flux, and iron ore is used as coolant. In addition, 6Nm 3 / h of argon was used as stirring gas and the furnace temperature was set at 1400°C.

[0067] Example 3

[0068] The 1500℃ molten slag discharged from converter steelmaking is charged into a closed DC electric furnace, and a carbonaceous reducing agent and high phosphate ore, SiO2 and Al2O3 as modifiers are added into the reduction furnace. The coke is calculated based on the grade of slag (TFe) and high phosphate ore, the ratio of carbon to iron is 275kg / tFe, the amount of high phosphate ore added is 25% of the total mass of slag, the amount of SiO2 added is 18% of the total mass of slag, and the amount of Al2O3 added is 12% of the total mass of slag. The reduced slag is the same as blast furnace slag, and the high phosphorus molten iron obtained by reduction is charged into an induction melting furnace, and then the spray gun in the furnace is heated at 45Nm 3 Oxygen is blown in at a rate of / h, and quicklime, dolomite, and silica sand are added from above as flux, and iron ore is used as coolant. In addition, 7Nm 3 / h of argon was used as stirring gas and the furnace temperature was set at 1500°C.

[0069] Example 4

[0070] The 1600℃ molten slag discharged from converter steelmaking is charged into a closed DC electric furnace, and a carbonaceous reducing agent and high phosphate ore, SiO2 and Al2O3 as modifiers are added into the reduction furnace. The coke is calculated according to the grade of slag (TFe) and high phosphate ore, the ratio of carbon to iron is 300kg / tFe, the amount of high phosphate ore added is 30% of the total mass of slag, the amount of SiO2 added is 15% of the total mass of slag, and the amount of Al2O3 added is 15% of the total mass of slag. The reduced slag is the same as blast furnace slag, and the high phosphorus molten iron obtained by reduction is charged into an induction melting furnace, and then the spray gun in the furnace is heated at 55Nm 3 Oxygen is blown in at a rate of / h, and quicklime, dolomite, and silica sand are added from above as flux, and iron ore is used as coolant. In addition, 8Nm 3 / h of argon was used as stirring gas and the furnace temperature was set at 1600°C.

[0071] The above is a detailed introduction to a method for separating iron and phosphorus from steel slag and then oxidizing it to prepare phosphorus-rich slag provided in an embodiment of the present application. The description of the above embodiment is only used to help understand the method and its core idea of ​​the present application; at the same time, for a person skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0072] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0073] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0074] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0075] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A method for separating iron and phosphorus from steel slag and then oxidizing it to prepare phosphorus-rich slag, characterized in that: The method comprises the following steps: S1: charging the molten steel slag discharged from converter steelmaking into a closed DC electric furnace, and adding a reducing agent and a modifier to obtain high-phosphorus molten iron; S2: The high-phosphorus molten iron obtained by reduction of S1 is charged into an induction melting furnace, oxygen is blown in, and flux and coolant are added at the same time, and inert gas is blown in from the bottom of the furnace for stirring, so as to separate iron and phosphorus from the slag and obtain phosphorus-rich slag; The S1 specifically includes: S11: charging molten iron into a closed DC electric furnace and leaving a layer of reducing slag; S12: charging the molten steel slag at 1500°C to 1700°C discharged from the converter steelmaking process into the holding furnace, and slowly adding the molten steel slag into the closed DC electric furnace by tilting; S13: continuously feeding the reducing agent and the modifying agent into the closed DC electric furnace through a raw material feeding pipe arranged on the furnace cover; S14: when the reduction treatment in the closed DC electric furnace is completed, the reduced slag is discharged from the slag outlet, and as the molten iron increases, when the molten iron level approaches the slag outlet, the high-phosphorus molten iron obtained by the reduction is discharged from the iron outlet; The reducing agent is coke, the modifier includes high phosphate ore, SiO2 and Al2O3, the S13 is calculated based on the grade of steel slag and high phosphate ore, and the ratio of carbon to iron is in the range of 150 to 300 kg / tFe; The amount of high phosphate ore added is 1-50% of the total mass of the steel slag, the amount of SiO2 added is 15-25% of the total mass of the steel slag, and the amount of Al2O3 added is 5-15% of the total mass of the steel slag; The high-phosphate ore contains 70% hematite, 2.5% apatite and 10% quartz, 40-50% iron and 0.4-1% phosphorus; the target composition of the steel slag after reduction in the S14 is basicity CaO / SiO2=1.0-1.2, Al2O3 content=10-12%, and the steel slag after reduction has the same composition as blast furnace slag; The S2 specifically includes: S21: The high-phosphorus molten iron obtained by reduction is charged into an induction smelting furnace, and then oxygen is blown into the lance at a rate of 30 to 60 Nm3 / h for dephosphorization treatment; S22: adding flux and coolant from above the induction melting furnace; S23: blowing 2-10 Nm3 / h of argon gas as stirring gas from a porous plug at the bottom of the induction melting furnace to obtain phosphorus-rich slag; The furnace temperature during stirring in S23 is set between 1200° C. and 1600° C.; The slag obtained by dephosphorization in S23 contains 10-20% P2O5, and the molten iron [P] after dephosphorization is less than 0.1%, and the molten iron is returned to the converter for steelmaking.

2. The method according to claim 1, characterized in that: The flux includes quicklime, dolomite and silica sand.

3. The method according to claim 1, characterized in that The coolant is iron ore.

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