阅读说明：本技术 一种熔融还原工艺生产纯铁的方法 (Method for producing pure iron by smelting reduction process ) 是由 张冠琪 王林顺 张晓峰 王金霞 王建磊 *** 魏召强 张静波 马宗礼 韩军义 于 2020-05-29 设计创作，主要内容包括：本发明涉及金属冶炼技术领域,尤其涉及一种熔融还原工艺生产纯铁的方法。该熔融还原工艺生产纯铁的方法,包括从初铁制备YT4等级纯铁的过程,原料是使用铁浴熔融还原法生产的初铁。通过该方法得到的产品中铁含量可以达到99.95％以上,满足YT4等级工业纯铁及高纯铁的成分条件,可以实现YT4等级工业纯铁的规模化生产,产品纯度高、生产成本低、安全环保,质量满足YT4等级工业纯铁和高纯铁的要求,生产过程控制稳定、产品质量优异。(The invention relates to the technical field of metal smelting, in particular to a method for producing pure iron by a smelting reduction process. The method for producing pure iron by the smelting reduction process comprises the step of preparing YT4 grade pure iron from primary iron, wherein the raw material is the primary iron produced by using an iron bath smelting reduction method. The iron content of the product obtained by the method can reach more than 99.95 percent, the component conditions of YT4 grade industrial pure iron and high-purity iron are met, the large-scale production of YT4 grade industrial pure iron can be realized, the product purity is high, the production cost is low, the safety and the environmental protection are realized, the quality meets the requirements of YT4 grade industrial pure iron and high-purity iron, the production process is controlled stably, and the product quality is excellent.)

1. A method for producing pure iron by a smelting reduction process is characterized by comprising the step of preparing YT4 grade pure iron from primary iron, wherein the raw material is the primary iron produced by using an iron bath smelting reduction method.

2. The method of producing pure iron according to the smelting reduction process of claim 1, wherein the iron bath smelting reduction process is a HIsmelt smelting reduction process, a core SRV furnace process control procedure of which comprises:

controlling the oxygen content of an oxygen-enriched hot air gun in the melting reduction furnace, taking the oxygen content of air as a base number, increasing the ore spraying amount by 5 tons and the oxygen-enriched content by 0.2-0.5%, controlling the pressure of a hot air outlet at 80-200kPa, and controlling the total content of five-harmful elements of lead, tin, arsenic, antimony and bismuth to be lower than 0.001 wt%;

controlling the total heat load of the smelting reduction furnace at 35-65MW, the heat load of each spray gun in the slag at 0.5-1.5MW and the height of a spring at 1-5m, and controlling the parameters to ensure that the content of phosphorus in the prepared primary iron is less than 0.015 wt% and the content of sulfur in the prepared primary iron is 0.09-0.12 wt%;

controlling the thickness of slag in the smelting reduction furnace to be 1.5-2.5m, so that the content of manganese, vanadium and titanium in the prepared primary iron is lower than 0.001 wt%, 0.001 wt% and 0.005 wt%;

the change coefficient of a pressure control system in the smelting reduction furnace is controlled by controlling a cone valve, the control pressure is increased by 1kPa every 3 seconds, and the total tapping time is controlled to be 8-10 min.

3. The method of producing pure iron by smelting reduction process according to claim 2, wherein said process of making YT4 grade pure iron from primary iron comprises: external pretreatment, oxygen converter smelting or continuous charging electric furnace smelting, LF refining furnace refining, and VOD vacuum furnace decarburization and deoxidation.

4. A method of producing pure iron according to the smelting reduction process of claim 3, wherein the out-of-furnace pretreatment comprises: and desulfurizing and adjusting carbon of the primary iron by using a composite desulfurizer to ensure that the sulfur content of the molten iron after desulfurization and adjustment is lower than 0.0010 wt%, and slagging off the molten iron after desulfurization and adjustment until the residual slag amount in the molten iron is less than 5 wt% of the total slag amount.

5. The method of producing pure iron according to the smelting reduction process of claim 4, wherein the composite desulfurizing agent comprises: 15-20 parts of magnesium powder, 30-50 parts of calcium oxide, 5-10 parts of coke particles, 5-10 parts of calcium fluoride and 5-10 parts of iron particles;

the coke particles are obtained by performing secondary treatment on dust particles generated in the process of the HIsmelt technology; the iron particles are separated from slag of the HIsmelt smelting reduction furnace.

6. The method for producing pure iron according to the smelting reduction process of claim 5, wherein the step of adding each component of the composite desulfurizing agent comprises:

1) sequentially blowing coke particles, magnesium powder and calcium oxide, controlling the total blowing time to be 5-10min, and controlling the blowing flow of nitrogen to be 50-160m³Min, controlling the pressure in the blowing process to be 80-350kPa, and positioning the spray gun at the position of the ladle 500-800mm away from the bottom of the ladle;

2) adding iron particles when the temperature of molten iron is not lower than 1300 ℃;

3) adding calcium fluoride when the temperature of the slag is not lower than 1300 ℃.

7. The method of producing pure iron according to claim 3, wherein the oxygen converter smelting comprises:

transferring the molten iron pretreated outside the furnace into an oxygen converter for smelting by using full molten iron, and adding pretreated slag into the full molten iron for slagging;

adding a slag modifier before slag splashing furnace protection to modify the slag, and controlling the content of ferric oxide in the slag to be lower than 20 wt% and the alkalinity of the slag to be 2.8-3.2; a rotational flow oxygen lance is used in the slag splashing protection furnace;

controlling the carbon content of the end point of the oxygen converter to be lower than 0.03%, the silicon content to be lower than 0.005%, the manganese content to be not higher than 0.001%, the phosphorus content to be lower than 0.005%, the sulfur content to be lower than 0.0010%, and controlling the tapping temperature to be 1590-1620 ℃;

the pre-treatment of the slag comprises: 30-40 parts of calcium oxide, 15-20 parts of silicon dioxide, 8-12 parts of magnesium oxide and 10-20 parts of coke particles;

the slag modifier comprises: 30-50 parts of coke particles, 10-20 parts of magnesium oxide and 20-30 parts of calcium oxide;

the coke particles are obtained by performing secondary treatment on dust particles generated in the process of the HIsmelt technology;

the pretreatment slag charge and the slag modifier are added once before the oxygen blowing of the converter, and the total amount of the addition is 25-35 kg/t.

8. The method of producing pure iron according to claim 3, wherein the continuous charging electric furnace smelting comprises:

transferring the molten iron pretreated outside the furnace into an electric furnace for smelting, adding pretreated slag charge into the electric furnace for slagging, wherein the addition amount of the pretreated slag charge is 25-35kg/t, the content of ferric oxide in the slag is controlled to be lower than 28 wt%, the alkalinity of the slag is 2.2-2.8, 100 kg/time of slag former is added, the total addition amount is 400-600kg, the interval is 4-6min each time, and the thickness of a slag layer is controlled to be 0.8-1.5 m;

the pre-treatment of the slag comprises: 30-40 parts of calcium oxide, 15-20 parts of silicon dioxide, 8-12 parts of magnesium oxide and 10-20 parts of coke particles; the slagging agent is carbon balls with carbon element content higher than 75 wt%;

in the early stage of smelting, oxygen blowing, decarburization and temperature raising are carried out; controlling the temperature in the furnace at 1540-plus 1580 ℃ in the middle stage of smelting; controlling the carbon content to be lower than 0.03%, the silicon content to be lower than 0.005%, the manganese content to be not higher than 0.001%, the phosphorus content to be lower than 0.005% and the sulfur content to be lower than 0.0010% in the later stage of smelting, and then controlling the tapping temperature to be 1590-1620 ℃ by heating a graphite electrode.

9. The method of producing pure iron according to the smelting reduction process of claim 3, wherein the LF refining furnace refining includes:

adding fine processing slag into molten iron smelted by an oxygen converter or a continuous charging electric furnace for slagging and purifying; adding the composite additive at 1/3 time point of total refining time of the LF refining furnace for modification, wherein the LF end point oxygen content is controlled at 380-500ppm, and the end point temperature is controlled at 1685-1710 ℃;

the fine processing slag charge comprises: 75-85 parts of calcium oxide and 10-15 parts of calcium fluoride; the addition amount of the fine processing slag charge is 6-8 kg/t;

the composite additive comprises: 30-40 parts of calcium fluoride, 30-40 parts of calcium oxide, 10-20 parts of aluminum oxide and 5-10 parts of foaming agent.

10. The method of producing pure iron according to claim 3, wherein the VOD vacuum furnace decarburization deoxygenation comprises:

adding molten iron refined by an LF refining furnace into a ladle, carrying out vacuum decarburization operation after the molten iron reaches a VOD vacuum furnace, sequentially opening a three-stage vacuum system, and simultaneously inserting an oxygen lance into the upper part to blow oxygen at a flow rate of 2000-3000m and at a stirring flow rate of 80-120L/min³And h, controlling the vacuum degree within 100Pa for 8-9min, stopping oxygen extraction, controlling the vacuum degree within 67Pa for 10-12min, measuring the temperature and determining the oxygen after VOD is broken, feeding an aluminum wire and a calcium core-spun wire for deoxidation and desulfurization treatment, blowing argon gas at the bottom for 10-30L/min, controlling the rolling diameter of molten steel to be less than 300mm, soft blowing for 15-16min, controlling the end point temperature at 1602-.

Technical Field

The invention relates to the technical field of metal smelting, in particular to a method for producing pure iron by a smelting reduction process.

Background

Pure iron is a steel material with very low carbon content (C < 0.01%), and has the properties of high iron purity, good toughness, good magnetic property, excellent electrical property and the like. As industrial pure iron for realizing industrial production and application, the content of iron element in the product reaches 99.6-99.8 percent, and the industrial pure iron is an important steel base material and is mainly used for smelting aerospace, military and civil alloys or steel products such as various high-temperature alloys, heat-resistant alloys, precision alloys, maraging steel, high-temperature bearing steel and the like.

The preparation of high-purity iron mainly comprises an electrolytic method, electroslag remelting, space purification, plasma smelting and the like, most of the high-purity iron is in a small-scale laboratory stage, the existing market demand cannot be met, the cost of the prepared high-purity iron is high, when the content of Fe reaches 99.95% -99.9999%, the price of the product can reach 1-150 ten thousand yuan/t, and the higher the purity, the greater the difficulty and the higher the value. The preparation process of high-purity iron at home and abroad is still not mature, and the supply of the high-purity iron cannot meet the demand, so the demand of the industrial pure iron with low production cost and high purity is urgent.

Disclosure of Invention

The invention provides a method for producing pure iron by a smelting reduction process, which uses low-cost primary iron produced by a HIsmelt smelting reduction method to smelt high-purity pure iron, the iron content in the product can reach more than 99.95 percent, the component conditions of YT 4-grade industrial pure iron and high-purity iron are met, and the method has the advantages of low cost, high purity, high added value and the like, and effectively solves the problems in the prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a method for producing pure iron by a smelting reduction process comprises the step of preparing YT4 grade pure iron from primary iron, wherein the raw material is the primary iron produced by an iron bath smelting reduction method.

Preferably, the iron bath smelting reduction method is a HIsmelt smelting reduction method, and the core SRV furnace process control process of the HIsmelt smelting reduction method comprises the following steps:

controlling the oxygen content of an oxygen-enriched hot air gun in the melting reduction furnace, taking the oxygen content of air as a base number, increasing the ore spraying amount by 5 tons and the oxygen-enriched content by 0.2-0.5%, controlling the pressure of a hot air outlet at 80-200kPa, and controlling the total content of five-harmful elements of lead, tin, arsenic, antimony and bismuth to be lower than 0.001 wt%;

controlling the total heat load of the smelting reduction furnace at 35-65MW, the heat load of each spray gun in the slag at 0.5-1.5MW and the height of a spring at 1-5m, and controlling the parameters to ensure that the content of phosphorus in the prepared primary iron is less than 0.015 wt% and the content of sulfur in the prepared primary iron is 0.09-0.12 wt%;

controlling the thickness of slag in the smelting reduction furnace to be 1.5-2.5m, so that the content of manganese, vanadium and titanium in the prepared primary iron is lower than 0.001 wt%, 0.001 wt% and 0.005 wt%;

the change coefficient of a pressure control system in the smelting reduction furnace is controlled by controlling a cone valve, the control pressure is increased by 1kPa every 3 seconds, and the total tapping time is controlled to be 8-10 min.

By controlling the total heat load of the smelting reduction furnace, the heat load in the slag of each spray gun and the height of the Yongquan, the content of phosphorus in molten iron in the smelting reduction furnace can be reduced, so that the content of phosphorus and sulfur reaches a preset value, and the quality of primary iron and the requirement of subsequent pretreatment outside the furnace are ensured.

The oxidation reduction atmosphere of the slag is adjusted by controlling the thickness of the slag in the smelting reduction furnace, so that trace elements such as manganese, vanadium, titanium and the like in the ore migrate into the slag in the smelting reduction furnace, and further the content of manganese, vanadium and titanium in the primary iron reaches the preset requirement.

The temperature change of the molten iron in the smelting reduction furnace in the tapping process of the smelting reduction furnace is reduced by controlling the pressure in the smelting reduction furnace and the tapping time of the smelting reduction furnace, so that the sedimentation elements such as lead in the molten iron in the smelting reduction furnace are prevented from floating from the bottom of the smelting reduction furnace and entering the primary iron.

The Yongquan is characterized in that hot air is blown into the upper part of the smelting reduction furnace to perform oxidation combustion exothermic reaction of carbon monoxide and hydrogen with self gas, carbon monoxide generated by reaction in a molten iron pool, hydrogen generated by cracking of volatile components in coal and nitrogen blown into a material carrier form mixed gas, and the strongly escaped rising gas forms the mixed Yongquan from high-temperature liquid iron slag.

Preferably, the primary iron comprises, by mass, 3.6-4.0% of carbon, 0.010-0.015% of phosphorus, 0.09-0.12% of sulfur, less than 0.01% of silicon, not more than 0.001% of manganese, and 0.0001-0.001% of five-harmful elements, wherein the five-harmful elements refer to lead, tin, arsenic, antimony and bismuth.

Preferably, the temperature of the molten iron of the primary iron is 1320-1380 ℃.

Preferably, the process for preparing YT4 grade pure iron from primary iron comprises the following steps: external pretreatment, oxygen converter smelting or continuous charging electric furnace smelting, LF refining furnace refining, and VOD vacuum furnace decarburization and deoxidation.

Preferably, the out-of-furnace pretreatment comprises: and desulfurizing and adjusting carbon of the primary iron by using a composite desulfurizer to ensure that the sulfur content of the molten iron after desulfurization and adjustment is lower than 0.0010 wt%, and slagging off the molten iron after desulfurization and adjustment until the residual slag amount in the molten iron is less than 5 wt% of the total slag amount.

Preferably, the composite desulfurizing agent includes: 15-20 parts of magnesium powder, 30-50 parts of calcium oxide, 5-10 parts of coke particles, 5-10 parts of calcium fluoride and 5-10 parts of iron particles;

the coke particles are obtained by performing secondary treatment on dust particles generated in the process of the HIsmelt technology; the iron particles are separated from slag of the HIsmelt smelting reduction furnace, and preferably, the iron particles are hollow granular simple substance iron and have the characteristics of light weight and large specific surface area.

Preferably, the step of adding each component of the composite desulfurizing agent comprises the following steps:

1) sequentially blowing coke particles, magnesium powder and calcium oxide, controlling the total blowing time to be 5-10min, and controlling the blowing flow of nitrogen to be 50-160m³Min, controlling the pressure in the blowing process to be 80-350kPa, and positioning the spray gun at the position of the ladle 500-800mm away from the bottom of the ladle;

2) adding iron particles when the temperature of molten iron is not lower than 1300 ℃;

3) adding calcium fluoride when the temperature of the slag is not lower than 1300 ℃.

The composite desulfurizer comprises the following components in sequence: coke particles, magnesium powder, calcium oxide, iron particles and furnace slag.

Preferably, the oxygen converter smelting comprises:

transferring the molten iron pretreated outside the furnace into an oxygen converter for smelting by using full molten iron, and adding pretreated slag into the full molten iron for slagging;

adding a slag modifier before slag splashing furnace protection to modify the slag, and controlling the content of ferric oxide in the slag to be lower than 20 wt% and the alkalinity of the slag to be 2.8-3.2; a rotational flow oxygen lance is used in the slag splashing protection furnace;

controlling the carbon content of the end point of the oxygen converter to be lower than 0.03%, the silicon content to be lower than 0.005%, the manganese content to be not higher than 0.001%, the phosphorus content to be lower than 0.005%, the sulfur content to be lower than 0.0010%, and controlling the tapping temperature to be 1590-1620 ℃;

the pre-treatment of the slag comprises: 30-40 parts of calcium oxide, 15-20 parts of silicon dioxide, 8-12 parts of magnesium oxide and 10-20 parts of coke particles;

the slag modifier comprises: 30-50 parts of coke particles, 10-20 parts of magnesium oxide and 20-30 parts of calcium oxide;

the coke particles are obtained by performing secondary treatment on dust particles generated in the process of the HIsmelt technology;

the pretreatment slag charge and the slag modifier are added once before the oxygen blowing of the converter, and the total amount of the addition is 25-35 kg/t.

Preferably, the continuous charging electric furnace smelting comprises the following steps:

transferring the molten iron pretreated outside the furnace into an electric furnace for smelting, adding pretreated slag charge into the electric furnace for slagging, wherein the addition amount of the pretreated slag charge is 25-35kg/t, the content of ferric oxide in the slag is controlled to be lower than 28 wt%, the alkalinity of the slag is 2.2-2.8, 100 kg/time of slag former is added, the total addition amount is 400-600kg, the interval is 4-6min each time, and the thickness of a slag layer is controlled to be 0.8-1.5 m;

the pre-treatment of the slag comprises: 30-40 parts of calcium oxide, 15-20 parts of silicon dioxide, 8-12 parts of magnesium oxide and 10-20 parts of coke particles; the slagging agent is carbon balls with carbon element content higher than 75 wt%;

in the early stage of smelting, oxygen blowing, decarburization and temperature raising are carried out; controlling the temperature in the furnace at 1540-plus 1580 ℃ in the middle stage of smelting; controlling the carbon content to be lower than 0.03%, the silicon content to be lower than 0.005%, the manganese content to be not higher than 0.001%, the phosphorus content to be lower than 0.005% and the sulfur content to be lower than 0.0010% in the later stage of smelting, and controlling the tapping temperature to be 1590-1620 ℃ by heating a graphite electrode;

the early smelting period is a time period before 1/3 of the total smelting time of the continuous charging electric furnace; the middle smelting period refers to a time period between 1/3 and 2/3 of the total smelting time of the continuous charging electric furnace; the later smelting period is a time period after 2/3 of the total smelting time of the continuous charging electric furnace.

In the middle stage of smelting, the graphite electrode can be used for supplying electricity for heating, and when the temperature is high, the graphite electrode is not used for heating.

The continuous charging electric furnace is provided with a furnace wall oxygen lance, and oxygen is blown to molten iron in the electric furnace for decarburization through the furnace wall oxygen lance so as to control the carbon content and the phosphorus and sulfur content of the molten iron; the continuous charging electric furnace adopts eccentric bottom tapping, and slag is effectively prevented from being carried in molten steel in the tapping process.

Preferably, the LF refining furnace refining comprises:

adding fine processing slag into molten iron smelted by an oxygen converter or a continuous charging electric furnace for slagging and purifying; adding the composite additive at 1/3 time point of total refining time of the LF refining furnace for modification, wherein the LF end point oxygen content is controlled at 380-500ppm, and the end point temperature is controlled at 1685-1710 ℃;

the fine processing slag charge comprises: 75-85 parts of calcium oxide and 10-15 parts of calcium fluoride; the addition amount of the fine processing slag charge is 6-8 kg/t;

the composite additive comprises: 30-40 parts of calcium fluoride, 30-40 parts of calcium oxide, 10-20 parts of aluminum oxide and 5-10 parts of foaming agent.

Preferably, the VOD vacuum furnace decarburization and deoxidation comprises the following steps:

adding molten iron refined by an LF refining furnace into a ladle, carrying out vacuum decarburization operation after the molten iron reaches a VOD vacuum furnace, sequentially opening a three-stage vacuum system, and simultaneously inserting an oxygen lance into the upper part to blow oxygen at a flow rate of 2000-3000m and at a stirring flow rate of 80-120L/min³And h, controlling the vacuum degree within 100Pa for 8-9min, stopping oxygen extraction, controlling the vacuum degree within 67Pa for 10-12min, measuring the temperature and determining the oxygen after VOD is broken, feeding an aluminum wire and a calcium core-spun wire for deoxidation and desulfurization treatment, blowing argon gas at the bottom for 10-30L/min, controlling the rolling diameter of molten steel to be less than 300mm, soft blowing for 15-16min, controlling the end point temperature at 1602-.

In the pretreatment outside the furnace, the composite desulfurizer is sprayed into the foundry ladle through a spray gun arranged on the foundry ladle, and the position of the spray gun on the foundry ladle is 500mm-800mm away from the bottom of the ladle. The composite desulfurizer pretreatment system is provided with a blowing pipeline, the blowing composite desulfurizer is positioned in a storage tank, the lower part of the blowing composite desulfurizer is connected with a tundish and a conveying pipeline through a valve, nitrogen is used as conveying carrier gas, the pipeline is connected with a special spray gun, and the special spray gun is inserted into a position of a ladle 500mm-800mm away from the bottom of the ladle for blowing desulfurization treatment. The spray gun is inserted into the ladle at a position 500mm-800mm away from the bottom of the ladle for spraying, because the molten iron of primary iron produced by the HIsmelt reduction method has the characteristics of low temperature and high sulfur, the common treatment process can not ensure that a desulfurizer and the molten iron react, and after a plurality of tests and fluid analysis, the spray gun is arranged at a position 500mm-800mm in consideration of the specification of the ladle and the using effect of the special spray gun, so that the bottom molten pool can be ensured to have a better stirring effect, and the desulfurization efficiency and the uniformity of the molten iron in the ladle are ensured. Meanwhile, as the primary molten iron produced by the HIsmelt reduction method has the characteristic of very high impact strength during desulfurization, if the gun position is too low, the airflow can scour the bottom refractory material, the service life of the ladle is greatly reduced, and if the gun position is too high, the stirring effect and the desulfurization effect of the bottom of the ladle cannot be ensured.

Spraying a composite desulfurizer into the ladle by using a spray gun, wherein the sulfur content in the molten iron after desulfurization treatment is lower than 0.0010 wt%; and after the molten iron is desulfurized, slagging off is carried out by using a surface filtration method, and the residual slag amount in the ladle is ensured to be less than 5 wt% of the total slag amount, so that the molten iron meets the requirement of the purity of high-purity pig iron, and the reverse osmosis of residual elements in the subsequent treatment process is avoided.

The function of the composite desulfurizer is as follows: because the temperature of the primary molten iron produced by the HIsmelt smelting reduction method is low, the sulfur content is more than 3 times of that of blast furnace molten iron, the traditional blast furnace molten iron pure iron smelting process cannot process the primary molten iron, and the temperature drop in the process is large, the coke particles in the composite desulfurizer used by the invention can supplement partial heat for the primary molten iron and provide carburizing conditions for subsequent processing, the calcium fluoride can improve the fluidity of furnace slag pretreated outside the furnace under the low-temperature condition, and the iron particles can improve the stirring effect of the composite desulfurizer in the ladle and improve the low-temperature stirring performance. Tests prove that the hollow granular elementary iron separated from the slag of the HIsmelt smelting reduction furnace has the components serving as a composite desulfurizer, and has the effects of improving stirring performance and avoiding temperature from being greatly reduced.

The slag modifier is used for the following functions: because the oxidability of the molten iron of the primary iron produced by the HIsmelt smelting reduction method is higher than that of the molten iron of a blast furnace, the end point carbon content is lower, and the smelting process of the converter lacks a front stage (silicomanganese oxidation period), the erosion of the smelting process to a furnace lining is higher than that of the traditional blast furnace molten iron, the slag is not easy to adhere to the surface of the furnace lining in the slag splashing furnace protection process, the service life of the furnace lining is influenced, and the continuous production cannot be realized by utilizing the traditional smelting method. Therefore, in order to enhance the protection of the furnace lining, a slag modifier is added before slag splashing protection to modify the slag, wherein the slag modifier is mainly used for adjusting the components, alkalinity and physical state of the slag and improving the fluidity and adhesiveness of the slag; meanwhile, a slag splashing furnace protection gun is used for improving the furnace protection effect, a rotational flow oxygen gun is used for replacing a common straight-through oxygen gun, the furnace slag is blown to the surface of the furnace lining under the action of rotational flow gas, and the furnace slag is attached to the surface of the furnace lining in a centrifugal motion mode under the action of rotational flow gas, so that the function of enhancing the protected furnace lining is achieved.

A converter steelmaking system for oxygen converter smelting is provided with an elevated bunker, and slagging is carried out by using pretreated slag. The method is characterized in that all slag materials are added at one time before oxygen blowing refining of a converter, which is different from the traditional steelmaking technology that slag materials such as lime and the like are added in batches, because the silicon content of molten iron of a blast furnace is high, more slag materials such as lime and the like need to be added in order to maintain certain slag alkalinity, the adding amount of the slag materials is more than 45kg/t, and the slag materials are added in batches in order to avoid influence on temperature and blowing effect caused by adding at one time; but the molten iron of the primary iron produced by the HIsmelt reduction method does not contain silicon, so that less-slag smelting can be realized, the total addition of the pretreated slag charge is 25-35kg/t, and the addition of the pretreated slag charge can be reduced by 30-50% compared with the addition of the slag charge in the traditional steelmaking technology; the optimal dephosphorization efficiency is ensured by controlling the end point temperature to be 1590-1620 ℃.

When the traditional molten iron is smelted in a converter, slagging materials such as lime, dolomite and the like are adopted, and elements such as silicon, manganese and the like in the molten iron are oxidized by blowing oxygen through an oxygen lance to form the molten iron with certain alkalinity (R ═ CaO/SiO)₂) The metallurgical slag charge of (1). Aiming at the characteristic that the molten iron of the primary iron produced by the HIsmelt smelting reduction method does not contain silicon and manganese, the slagging smelting is carried out without using traditional materials and processes, the slagging smelting is carried out by adopting the pretreated slag charge provided by the invention, the slagging smelting is more suitable for the smelting condition that the molten iron does not contain silicon, and meanwhile, coke particles contained in the pretreated slag charge can provide partial heat for smelting, so that the problems of insufficient heat of low-temperature, low-carbon, silicon-free oxidation and heat release of the molten iron of the primary iron produced by the HIsmelt smelting reduction method and the like are solvedThe difficult problem is that the slagging smelting operation is better carried out.

In order to reduce the consumption of raw materials and develop a low-silicon and low-slag smelting technology, molten iron (0.5 +/-0.2%) is subjected to desiliconization before entering a converter, the silicon content is controlled to be 0.2-0.3% (the lowest level which can be achieved by the prior art), so that the aim of smelting steel with less lime and less slag is fulfilled, and the consumption of slag materials for steel-making is controlled to be about 35kg/t (the consumption of slag in the traditional steel-making technology in China is controlled to be more than 45kg/t-75 kg/t). The ferrosilicon-free water steelmaking technology adopted by the invention is combined with the pretreated slag provided by the invention, and the consumption of the slag is controlled to be 25-35kg/t, which is lower than the slag consumption level of the foreign advanced steelmaking technology.

In the refining of the LF refining furnace, the composite additive is mainly used for adjusting the condition of slag, adsorbing harmful elements in molten iron, carrying out slag washing on the molten iron and reducing the content of residual elements in the molten iron. The application range of each component of the composite additive is mainly determined according to different requirements of smelting different grades of pure iron on residual elements in molten steel and the slag washing degree of the residual elements according to the requirements of steel grades.

The VOD vacuum furnace is adopted for decarburization and deoxidation, because the VOD vacuum furnace is provided with a special oxygen lance, oxygen can be continuously blown for deep decarburization in a vacuum environment, the end point carbon content of the molten steel can reach 0.0010 percent (10ppm), and the purity of the molten steel is improved.

The invention has the beneficial effects that:

the method prepares the pure iron by using primary iron with lower cost produced by a HIsmelt reduction method, performing external pretreatment, oxygen converter smelting or continuous charging electric furnace smelting, LF refining furnace refining, and VOD vacuum furnace decarburization and deoxidation, wherein the iron content in the obtained product can reach more than 99.95 percent, the component conditions of YT4 grade industrial pure iron and high-purity iron are met, the large-scale production of YT4 grade industrial pure iron can be realized, the product has high purity and low production cost, the quality meets the requirements of YT4 grade industrial pure iron and high-purity iron, the production process is controlled stably, the product quality is excellent, and the industrial stable production of high-end pure iron can be realized.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

fig. 1 is a flow chart of the process of preparing YT4 grade pure iron from primary iron according to the embodiment of the application.

Detailed Description

In order to clearly illustrate the technical features of the present invention, the present invention is explained in detail by the following embodiments.

At present, the existing pure iron production method aims at blast furnace molten iron, the contents of phosphorus, silicon, manganese and trace elements in the blast furnace molten iron are high, and the method is used for smelting pure iron and has the disadvantages of complex process control, large quality fluctuation and high production cost.

And the metal is smelted by an iron bath smelting reduction method, particularly by an HIsmelt smelting reduction method by adopting a production process different from that of a traditional blast furnace, and compared with blast furnace molten iron, the primary iron produced by the HIsmelt smelting reduction method has the characteristics of low temperature, high sulfur content, low silicon content, low titanium content, low manganese content, low phosphorus content, low five-harmful elements and the like.

The core SRV furnace process control process using the HIsmelt reduction process comprises the following steps:

controlling the oxygen content of an oxygen-enriched hot air gun in the melting reduction furnace, taking the oxygen content of air as a base number, increasing the ore spraying amount by 5 tons and the oxygen-enriched content by 0.2-0.5%, controlling the pressure of a hot air outlet at 80-200kPa, and controlling the total content of five-harmful elements of lead, tin, arsenic, antimony and bismuth to be lower than 0.001 wt%;

controlling the total heat load of the smelting reduction furnace at 35-65MW, the heat load of each spray gun in the slag at 0.5-1.5MW and the height of a spring at 1-5m, and controlling the parameters to ensure that the content of phosphorus in the prepared primary iron is less than 0.015 wt% and the content of sulfur in the prepared primary iron is 0.09-0.12 wt%;

controlling the thickness of slag in the smelting reduction furnace to be 1.5-2.5m, so that the content of manganese, vanadium and titanium in the prepared primary iron is lower than 0.001 wt%, 0.001 wt% and 0.005 wt%;

the change coefficient of a pressure control system in the smelting reduction furnace is controlled by controlling a cone valve, the control pressure is increased by 1kPa every 3 seconds, and the total tapping time is controlled to be 8-10 min.

The contents of each element and the temperature of blast furnace molten iron and primary iron produced by the HIsmelt reduction method of the present application are compared in table 1.

TABLE 1 blast furnace molten iron and the primary iron produced by the HIsmelt reduction method of the present application, contents of respective elements and molten iron temperature

As can be seen from table 1, the blast furnace molten iron and the primary iron produced by the HIsmelt reduction method of the present application have significant differences in the contents of the respective elements.

The traditional blast furnace molten iron contains certain elements such as silicon, manganese, phosphorus and the like, and the converter smelting process is divided into three stages: in the early stage of blowing (silicomanganese oxidation period), in the middle stage of blowing (carbon oxidation period) and in the final stage of blowing (carbon oxidation period), the oxidation of silicon and manganese is required to be completed in the early stage of blowing, certain lime and other slag materials are added to produce smelting slag with certain alkalinity and components, elements such as residual manganese and the like in pure iron smelted by blast furnace molten iron are high, the pure iron smelted by the blast furnace molten iron is limited to be smelted into high-quality pure iron, and therefore the pure iron prepared by using the traditional pure iron smelting process is low in smelting level. The primary molten iron produced by the HIsmelt reduction method does not contain elements such as silicon, manganese and the like, if the silicon-manganese alloy is added into the primary molten iron, the cost is increased, the heat loss is caused, and if the alloy is not added, slagging and smelting can not be completed by slag materials (lime, dolomite and the like) of a traditional blast furnace molten iron converter, so that the traditional process method for producing pure iron by the blast furnace molten iron is not suitable for the primary molten iron produced by the HIsmelt reduction method.

Referring to fig. 1, the present invention adopts a process different from the conventional blast furnace molten iron for producing pure iron to accomplish the smelting of YT4 grade industrial pure iron and ultra pure iron using the primary molten iron produced by the HIsmelt reduction process.