Self-heating ilmenite low-carbon iron-titanium separation method

Abstract

The invention provides a self-heating ilmenite low-carbon iron-titanium separation method, which comprises the following steps of: pre-reducing titanium-containing iron ore in a preheating section of an electric heating rotary kiln, and directly electrifying the iron ore or a solid material (hereinafter referred to as a material) obtained by changing the iron ore in a heating process through a power supply electrode in a heating section of the electric heating rotary kiln, the materials are heated through heating of the resistor of the material pile located at the heating section, so that iron in the oxidation state in the iron ore is reduced into iron in the metal state; and the iron ore discharged from the electric heating rotary kiln is subjected to slag-iron separation on oxidation-state titanium and metal-state iron through the melting separation process. The method has the advantages that the technological process is simple, carbon emission is low, the production capacity is large, and the titanium content in the titanium-containing slag obtained through separation when the titanium content in the ilmenite is high is close to that of titanium concentrate.

Description

Technical Field

[0001] The invention belongs to the field of iron and steel metallurgy and relates to a process for separating iron and titanium in an ironmaking process. Background Art

[0002] my country's vanadium-titanium magnetite is widely distributed in Panzhihua and Chengde. According to a report by Panzhihua Daily on April 10, 2023, the Panzhihua region has a proven reserve of 8.67 billion tons of vanadium-titanium magnetite, ranking first in the world in terms of titanium resource reserves, but the utilization rate of titanium resources is only 29%. In the process of blast furnace ironmaking, titanium-containing iron ore needs to control the titanium content in blast furnace slag to avoid problems such as excessive viscosity of molten blast furnace slag. Taking the vanadium-titanium magnetite in Panzhihua as an example, after beneficiation, balling and oxidative roasting, the oxidized pellets obtained generally have an iron content of 53-55%, and the titanium content is calculated as titanium dioxide, reaching more than 10%. If such an ore is used entirely in blast furnace ironmaking, the content of titanium dioxide in the slag will be as high as about 43% based on the iron ore grade of 54% and the iron recovery rate of 100% (the actual general ore iron recovery rate is more than 99%, and the vanadium-titanium magnetite iron recovery rate is about 96%) without the addition of other furnace charges. Such a high titanium dioxide content partially generates low-valent titanium oxide and titanium carbide, resulting in a high viscosity of the molten blast furnace slag. It is necessary to add general ore and / or other slag-making materials to reduce the titanium dioxide content in the blast furnace slag and control the titanium dioxide content below 23%. With such a blast furnace ironmaking process, not only are the raw materials diverse and complicated, but the blast furnace slag cannot be used directly to extract titanium. The most advanced process for blast furnace slag with a titanium dioxide content of 23% is to reduce it to titanium carbide by high-temperature carbon thermal reduction, in which the titanium carbide reacts with chlorine at a lower temperature to form titanium tetrachloride, which is then used in the production of chloride titanium dioxide or sponge titanium. However, even such a process has not yet been industrialized on a large scale due to its high process difficulty. The vast majority of steel mills using vanadium-titanium magnetite control the titanium dioxide in blast furnace slag to a lower level, generally around 16~18%. Its blast furnace slag is used to produce cement or building bricks. The titanium resources inside are wasted.

[0003] The existing solution generally adopts the direct reduction iron process, which reduces vanadium-titanium magnetite with carbon or hydrogen at about 1000°C to produce direct reduced iron, and then performs smelting, magnetic separation or gravity separation to separate titanium and iron to obtain direct reduced iron and titanium slag. Direct reduced iron can enter the electric furnace for steelmaking, and titanium slag is used to extract titanium. The direct reduction iron process using coke or other coal not only has high carbon emissions, but also carbon will bring in a certain amount of impurities, reducing the grade of titanium in the obtained titanium slag. The key is that the direct reduction iron process using coke or coal, whether it is a rotary kiln or a vertical kiln, is difficult to mass produce. The largest rotary kiln process has a production capacity of about 150,000 tons, and the equipment utilization rate is very low. In fact, there is no large-scale production capacity and process route.

[0004] Under the general background of carbon peak and carbon neutrality, the gas-based reduction ironmaking process is used to produce direct reduced iron, which is applied to vanadium-titanium magnetite, which can solve the problem of iron-titanium separation while maintaining low carbon or even micro-carbon emissions. However, the gas-based (hydrogen or hydrogen-rich gas) direct reduction iron process currently also has great problems, and there is no safe and feasible process so far. When the gas-based direct reduction ironmaking process is adopted, because the reduction of ferric oxide by hydrogen is a strong endothermic reaction, heat supply for the reaction becomes a serious problem. In May 2021, Zhangxuan Technology (using the vertical furnace direct reduction iron technology of Tenova, Italy) started the construction of a 1.2 million tons / year hydrogen metallurgy demonstration project in Zhangjiakou, which is a gas-based direct reduction ironmaking process. The project takes advantage of the Zhangjiakou National Renewable Energy Demonstration Zone to develop a new hydrogen reduction process that can replace the traditional blast furnace carbon metallurgical process, and is expected to reduce carbon emissions by 60%. In principle, the project can use green electricity (photovoltaic wind power, hydropower and plant straw power generation) and green hydrogen (hydrogen obtained by electrolyzing water with green electricity) to achieve more than 90% carbon emission reduction. It is estimated that it uses coke oven gas as a reducing agent, and coke oven gas also contains a large amount of carbon-containing gas, which cannot reach the level of carbon emission reduction of more than 90%. On the other hand, in order to provide heat for the reaction of hydrogen reduction of hematite, some oxygen is added to the raw gas in the reaction process, and some methane, CO or hydrogen in the raw gas is burned with oxygen to provide heat for the reaction. In the process flow of this project, in order to provide heat for the reduction reaction, hydrogen or coke oven gas is also heated to 850℃, and then oxygen is introduced to burn to heat the gas entering the furnace to about 950℃. However, the sensible heat of the oxidized pellets and the gas entering the vertical furnace is very small compared with the latent heat of the reaction required for the reaction, and an excessive amount of gas is required to bring in heat. Moreover, hydrogen or hydrogen-rich gas, when heated to such a high temperature, has very low safety and high requirements for the heat resistance and hydrogen corrosion resistance of the equipment material. Furthermore, the combustion reaction of oxygen does not necessarily occur at the site of the reduction reaction of hydrogen oxidation iron. The addition of additional oxygen also wastes reducing gas, and the generated water or CO2 is not conducive to the reduction reaction of iron oxide. At present, this process should be the most advanced process for gas-based direct reduction of iron in the field of hydrogen metallurgy. Due to the huge production capacity of the steel industry, the hydrogen reduction ironmaking process must be planned to have an annual production capacity of at least 500,000 tons. Whether using a vertical kiln or a rotary kiln, for large-scale endothermic reactions, heating and heat transfer in such a large reactor is a huge challenge. Heating hydrogen or hydrogen-rich gas poses a huge safety risk.

[0005] In summary, the use of vanadium-titanium magnetite in blast furnace ironmaking has the problem that the titanium content in blast furnace slag cannot be too high and the titanium in blast furnace slag cannot be effectively utilized at present. In order to recover the titanium in vanadium-titanium magnetite, the direct reduction iron process is used, but the direct reduction iron process is not mature, safe and reliable. Summary of the invention

[0006] The purpose of the present invention is to provide a low-carbon or low-carbon direct reduction iron and iron-titanium separation process on a scale of 100,000 tons to 1 million tons, so as to obtain high-grade titanium slag in the ironmaking process to achieve the purpose of titanium-iron separation and effective utilization of titanium resources in ilmenite.

[0007] The object of the present invention is achieved by directly electrifying titanium-containing iron ore or solid material generated during the reaction (hereinafter referred to as material) with power supply electrodes in an electric heating rotary kiln, and heating the material and supplying heat for the endothermic reaction by generating heat under the action of the electric current by relying on the resistance of the material pile itself. In this way, a large-scale low-carbon ironmaking process can be realized, and a high titanium content in the material is maintained, and then the material is melted to separate slag from iron, and titanium slag with a high titanium content is obtained by separation. At the same time, the separated direct reduced iron can be directly used for electric furnace steelmaking.

[0008] A self-heating ilmenite low-carbon iron-titanium separation method, characterized in that: titanium-containing iron ore is fed into an electric heating rotary kiln for heating, and during the heating process, the oxidized iron reacts with hydrogen or hydrogen-rich gas to obtain metallic iron, and the reduced iron ore exiting the electric heating rotary kiln is then subjected to a slag-iron separation process, i.e., melted and separated to obtain molten iron and titanium slag. The heating process is as follows: in the heating section of the electric heating rotary kiln, the ilmenite and / or the material obtained by the change during the heating process (hereinafter referred to as the material) are directly energized through the power supply electrode, and the material pile is heated by its own resistance, and the material passes through the preheating section, the heating section, and the cooling section in the electric heating rotary kiln in sequence, and then the material is discharged; and the highest temperature of the material in the electric heating rotary kiln is not less than 650°C; the material is preheated by the gas withdrawn from the heating section in the preheating section and partially pre-reduced so that its conductivity is improved; the iron oxide is reduced in the heating section to generate direct reduced iron or sponge iron. The titanium-containing iron ore is one or more of sea sand ore, ilmenite, vanadium-titanium magnetite, and the concentrate, pellets, sintered ore, and sintered pellets of the aforementioned ore. The technical solution of the present invention has no special requirements on the type of raw material ore, the occurrence form or crystal phase of iron, vanadium, and titanium in the raw material ore, and has no special requirements on the common impurities in the ore and their existence form, but has certain requirements on the iron content in the ore, requiring the total average total iron content of various iron-containing raw materials fed to the electric rotary kiln to be more than 40%, preferably more than 45%. The gas pressure in the electric rotary kiln is less than 1MPa.

[0009] Furthermore, the hydrogen-rich gas is pure hydrogen, which enters the electric heating rotary kiln and passes through the cooling section, heating section and preheating section in sequence, and then withdraws from the electric heating rotary kiln; the hydrogen is preheated by heat exchange with the material withdrawn from the heating section in the cooling section. Alternatively, the hydrogen-rich gas is one or more of coal gas, shale gas, coalbed methane, coke oven gas, blast furnace gas, water gas, synthesis gas, methanol, ammonia, straw gasification gas, and natural gas, or hydrogen is added to the above gases.

[0010] Furthermore, the separation process is to melt the reduced iron ore from the electric heating rotary kiln, that is, heat and melt it, separate it into molten iron and slag containing oxidized titanium, and separate the slag from the iron. When the hydrogen-rich gas used contains carbon, part of the carbon in the gas phase will enter the reduced iron to form iron carbide, which is collectively referred to as reduced iron. For vanadium-titanium magnetite, the vanadium and part of the unreduced iron enter the titanium slag.

[0011] Alternatively, during the smelting process, the residual carbon in the reduced iron ore or the additionally added carbon or silicon is further used to deeply reduce or finely reduce the oxidized vanadium and part of the unreduced iron in the reduced vanadium-titanium magnetite, so that the vanadium enters the molten iron for vanadium extraction by the existing converter or atomization vanadium extraction process. The further reduction of part of the unreduced iron also improves the recovery rate of iron.

[0012] Furthermore, for vanadium-titanium magnetite, slag-iron separation is carried out in two steps. The first step is as mentioned above, first separating a large amount of reduced iron and slag, and the vanadium and part of the unreduced iron enter the titanium slag. Then the slag is deeply reduced at high temperature to reduce most of the vanadium and iron therein, and a secondary smelting is performed to obtain titanium slag with high titanium content and vanadium-containing molten iron. The carbon required for deep reduction is deposited by the reaction of carbon-containing hydrogen-rich gas, or external carbon. The reductant for deep reduction can also be externally added metallic silicon. For deep reduction, it is generally necessary to increase the temperature of the titanium slag to above 1400°C, preferably above 1600°C, to reduce the viscosity of the slag.

[0013] Furthermore, the electric heating rotary kiln is: an electric heating rotary kiln (hereinafter referred to as the electric heating rotary kiln) having a heating section in its furnace, wherein the heating section is provided with a plurality of electrodes of a heating power source, voltage is applied to the heated material through the electrodes so as to feed current into the heated material, and the heated material is heated by utilizing the resistance heating of the heated material accumulated in the heating section; the electric heating rotary kiln also has a preheating section and a cooling section; the material passes through the preheating section, the heating section and the cooling section in the electric heating rotary kiln in sequence; the electric heating rotary kiln is provided with a gas inlet at one end of the cooling section and a gas outlet at one end of the preheating section.

[0014] The process of the present invention can use low-grade titanium-containing iron ore as raw material. The titanium-containing iron ore also includes concentrate, raw ore and tailings with an iron grade of more than 45% and their sintered or oxidized pellets.

[0015] Compared with the prior art, the present invention has the following advantages: Compared with the traditional blast furnace ironmaking process, the ironmaking process of the present invention can reduce carbon emissions by 60%, or when full hydrogen gas is used as the reducing gas, carbon emissions can be reduced by more than 90%.

[0016] When the melting process is adopted, molten iron and high-titanium slag can be obtained in one step. For vanadium-titanium magnetite, according to the requirements of the subsequent vanadium and titanium extraction process, vanadium can enter the molten iron or the titanium slag.

[0017] Compared with the existing vanadium-titanium magnetite blast furnace ironmaking process, it can effectively utilize the titanium resources in the iron ore. It avoids the waste of titanium resources in the iron concentrate. The vanadium-titanium magnetite in the Panxi area is directly reduced and then separated from the slag and iron. The titanium content in the titanium slag can reach more than 40%, which is close to the 47% titanium content in the titanium concentrate, and the iron content is much lower than the iron content in the titanium concentrate in the Panxi area, which is conducive to the subsequent extraction of titanium.

[0018] Since the titanium resources in the vanadium-titanium magnetite can be utilized, the process cost of the present invention is comparable to or even better than the corresponding blast furnace ironmaking cost, and is economically feasible.

[0019] Compared with the existing rotary kiln direct reduction iron process, the electric heating rotary kiln that directly heats the material by electricity eliminates the limitation of heat transfer on the thickness of the material pile, and the material filling rate of the heating section can be greatly improved, thereby improving the kiln chamber utilization rate and equipment production capacity of the rotary kiln.

[0020] Compared with the vertical furnace direct reduction iron process, the problem of material adhesion in the heating section, that is, the reaction section, is avoided, and the occurrence of material or kiln blockage is avoided, and the process reliability is improved. The reaction temperature can also be raised to a high enough level to increase the reduction percentage of iron in the ironbrook tantalum ore.

[0021] The process and equipment of the present invention are simplified, the safety is improved, the equipment investment is reduced, the operation cost is lowered, and there are no insurmountable technical difficulties in large-scale production. It has technical feasibility, safety and economic feasibility.

[0022] In summary, the present invention has opened up a technical route for the utilization of titanium resources in vanadium-titanium magnetite or other ilmenite ores with low carbon emissions, high safety, low investment and operating costs, high reliability, practical technology and high titanium resource utilization. DETAILED DESCRIPTION Example

[0023] Iron ore pellets are oxidized and roasted to obtain oxidized pellets. In this embodiment, vanadium-titanium magnetite oxidized pellets with an iron content of about 54%, a vanadium oxide content of 0.34%, and a titanium dioxide content of 10.2% are used as raw materials. According to XRD analysis, the titanium dioxide in the raw material exists in the form of iron brookite, and compared with hematite, iron brookite is more difficult to reduce. The oxidized pellets are not preheated and directly enter the charging hopper of the electric rotary kiln. As the electric rotary kiln rotates, the oxidized pellets enter the preheating section of the electric rotary kiln, and heat is exchanged with the high-temperature gas from the heating section of the electric rotary kiln in the preheating section. When it is preheated to about 650°C, the oxidized pellets are partially reduced and obtain conductivity. The oxidized pellets then move into the heating section. Electrodes of a heating power supply are provided at both ends of the heating section, which feed current into the material in the heating section. The material is heated by the current, and the temperature is further increased to 950~1200°C. In the heating section, the iron oxide in the oxidized pellets is reduced to direct reduced iron. The average material filling rate of the preheating section of the electric rotary kiln is ~80%, ~60% in the heating section, and ~50% at the outlet of the cooling section. The material leaving the heating section exchanges heat with the room temperature or low temperature coke oven gas entering the kiln, which reduces the material temperature and preheats the coke oven gas. The coke oven gas has a high temperature when it enters the heating section, and the coke oven gas is 2 times excessive. After analysis, ~93% of the iron in the reduced pellets is reduced to metallic iron, which also contains ~2% carbon. The above-mentioned reduced iron is added to the electric furnace for melting, and the melting time is 60 minutes, and then the slag and molten iron are separated. The titanium dioxide content in the slag is 39.3%, and the titanium recovery rate is close to 99%. About 80% of the vanadium enters the molten iron. In comparison, the total iron in the titanium concentrate in the Panxi area is about 30%. This process has a good separation degree of iron and titanium. The titanium slag contains relatively low levels of iron and calcium and can be used as a raw material for producing titanium dioxide powder using the sulfuric acid process, which can significantly reduce sulfuric acid consumption. Example

[0024] The electric heating rotary kiln is the same as that in Example 1, and only differs from Example 1 in the slag iron separation process. In this embodiment, the metallization rate of the direct reduced iron can be controlled to be lower in the electric heating rotary kiln, and the metallization rate can be controlled to 80%, which can reduce the energy consumption and material residence time in the electric heating rotary kiln process and improve the equipment capacity. Then, the slag iron separation is performed twice by the method of melting, deep reduction of titanium slag, and melting again.

[0025] Specifically, the direct reduced iron from the electric heating rotary kiln is melted by electric heating auxiliary heating, and slag iron separation is performed to obtain titanium slag containing vanadium and part of the unreduced iron. The molten iron obtained by the first melting has low impurity content and high cleanliness. Then the aforementioned titanium slag is further heated, and carbon or metallic silicon is used as a reducing agent for deep reduction. The residual iron oxides and most of the vanadium in the titanium slag are reduced to form vanadium-containing molten iron, and then slag iron separation is performed again to obtain titanium slag and vanadium-containing molten iron. The titanium content in the titanium slag obtained by the secondary slag iron separation is further improved.

[0026] Although the iron content of the iron ore raw materials used in the embodiments is relatively high, laboratory-scale principle verification experiments have shown that some types of ores with an iron content as low as 40% can also adopt the technical solution of the present invention; iron ores with an iron content higher than 45% or dust from other steel industries can definitely adopt the technical solution of the present invention.

Claims

1. A self-heating ilmenite low-carbon iron-titanium separation method, characterized in that: The titanium-containing iron ore is fed into an electric heating rotary kiln for heating. During the heating process, the oxidized iron reacts with the hydrogen-rich gas to obtain metallic iron. The reduced iron ore exiting the electric heating rotary kiln is then subjected to a slag-iron separation process to separate the oxidized titanium from the metallic iron. The heating process is as follows: in the heating section of the electric heating rotary kiln, the ilmenite and / or the material obtained by the change in the heating process (hereinafter referred to as the material) are directly electrified through the power supply electrode, the material pile generates heat with its own resistance, the material passes through the preheating section, the heating section, the cooling section in the electric heating rotary kiln in sequence, and then is discharged; and the highest temperature of the material in the electric heating rotary kiln is not less than 650°C; the material is preheated by the gas withdrawn from the heating section in the preheating section and is partially pre-reduced so that its conductivity is improved; the iron oxide is reduced in the heating section to generate direct reduced iron or sponge iron; The titanium-containing iron ore is one or more of sea sand ore, ilmenite, vanadium-titanium magnetite, titanium-containing iron concentrate, oxidized pellets or sintered ore obtained by roasting pellets or particles of ilmenite, oxidized pellets or sintered ore obtained by roasting pellets or particles of vanadium-titanium magnetite, and oxidized pellets or sintered ore obtained by roasting pellets or particles of titanium-containing iron concentrate; The slag-iron separation process is to subject the reduced iron ore leaving the electric heating rotary kiln to a melting process, that is, heating and melting, to separate it into molten iron and slag containing oxidized titanium, and then to separate the slag-iron; The gas pressure in the electric heating rotary kiln is less than 1 MPa.

2. The method for separating low-carbon iron and titanium from self-heating ilmenite according to claim 1, characterized in that: The hydrogen-rich gas is pure hydrogen, which enters the electric heating rotary kiln and passes through the cooling section, heating section and preheating section in sequence, and then withdraws from the electric heating rotary kiln; the hydrogen is preheated by heat exchange with the material withdrawn from the heating section in the cooling section.

3. The method for separating low-carbon iron and titanium from self-heating ilmenite according to claim 1, characterized in that: The hydrogen-rich gas is one or more of coal gas, shale gas, coalbed methane, coke oven gas, water gas, blast furnace gas, synthesis gas, methanol, ammonia, straw gasification gas, natural gas, or hydrogen is added to the above gases; after the hydrogen-rich gas enters the electric heating rotary kiln, it passes through the cooling section, heating section and preheating section in sequence, and then withdraws from the electric heating rotary kiln; the hydrogen-rich gas is preheated by heat exchange with the material withdrawn from the heating section in the cooling section.

4. A self-heating ilmenite low-carbon iron-titanium separation method according to any one of claims 1 to 3, characterized in that: In the slag-iron separation process, the oxygen-state vanadium and / or part of the unreduced oxidized iron in the reduced iron ore enter the slag together with the oxidized titanium to form titanium slag.

5. A self-heating method for separating low-carbon iron and titanium from ilmenite according to any one of claims 1 to 3, characterized in that: In the slag-iron separation process, the oxygen-state vanadium and / or part of the unreduced oxidized iron in the reduced iron ore are reduced into molten iron by the residual carbon or added carbon or silicon in the reduced iron ore.

6. The method for separating low-carbon iron and titanium from self-heating ilmenite according to claim 4, characterized in that: The titanium slag is deeply reduced, and the vanadium and residual oxidized iron therein are reduced to form vanadium-containing molten iron, which is then separated from the slag and iron again to obtain vanadium-containing molten iron and titanium-containing secondary slag.

7. A self-heating method for separating low-carbon iron and titanium from ilmenite according to any one of claims 1 to 6, characterized in that: The electric heating rotary kiln is as follows: the furnace has a heating section, and a plurality of electrodes of a heating power supply are arranged in the heating section. Voltage is applied to the heated material through the electrodes so that current is fed into the heated material, and the heated material is heated by utilizing the resistance heating of the heated material accumulated in the heating section; the electric heating rotary kiln also has a preheating section and a cooling section; the material passes through the preheating section, the heating section and the cooling section in the electric heating rotary kiln in sequence; the electric heating rotary kiln is provided with a gas inlet at one end of the cooling section and a gas outlet at one end of the preheating section.