Method for directly reducing vanadium-titanium magnetite by using gas-based shaft furnace

Abstract

The application provides a method for directly reducing vanadium-titanium magnetite in a gas-based shaft furnace, and belongs to the technical field of metallurgical processes. The method comprises the following steps: mixing: uniformly mixing 10-15 parts by weight of pulverized bituminous coal, 80-85 parts by weight of iron vanadium-titanium magnetite powder, 5-10 parts by weight of a high-temperature accelerator and 8-12 parts by weight of hot water to obtain mixed materials; balling: balling the mixed materials to obtain briquettes, which do not need to be heated, dried or roasted; and reducing: directly reducing the briquettes in a gas-based shaft furnace to obtain finished vanadium-titanium DRI. The application uses 100% vanadium-titanium ore, adopts non-blast furnace technology and a gas-based shaft furnace direct reduction process, the carbon in the prepared bituminous coal and the hot water are subjected to a gasification reaction at high temperature to generate CO and H2 required by the reduced iron, the amount of reducing gas used is reduced, and the technical problem of unstable supply of reduced coke in the prior art for deeply reducing vanadium-titanium magnetite is fundamentally solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metallurgical process, and particularly relates to a method for directly reducing vanadium-titanium magnetite by using a gas-based shaft furnace. BACKGROUND

[0002] Vanadium-titanium magnetite is a multi-element symbiotic iron ore mainly containing iron, vanadium and titanium, and also containing other useful elements such as cobalt, nickel, chromium, scandium and gallium, and has a high comprehensive utilization value. In terms of mineral composition, vanadium-titanium magnetite is a complex body closely coexisting with magnetite (Fe3O4), titanomelinite (2FeO·TiO2), magnesium-aluminum spinel (MgO·Al2O3) and ilmenite (FeO·TiO2). Iron is present in magnetite (Fe3O4) which is easy to reduce, and titanomelinite (2FeO·TiO2) and ilmenite (FeO·TiO2) which are difficult to reduce, and the iron in the difficult-to-reduce iron minerals accounts for about 1 / 3 of the total iron. Vanadium-titanium magnetite is difficult to reduce, and titanium is easy to form titanium nitride and titanium carbide under a strong reducing atmosphere, which causes the molten iron to have a large viscosity and makes it difficult to separate slag and iron, and thus there is a great difference in smelting technology from ordinary iron ore, and it has been considered as "dull ore" by some foreign experts, and the comprehensive utilization of iron, vanadium and titanium resources thereof is a world problem.

[0003] The utilization of vanadium-titanium magnetite mainly includes a blast furnace method and a non-blast furnace method.

[0004] In the smelting of vanadium-titanium ore by a blast furnace, about 30% of ordinary ore is added, the iron grade entering the furnace is 52%, the Ti content in the molten iron is 0.2%, the slag ratio is 550-600 kg, the TiO2 content in the slag is about 22%, 80% of vanadium enters the molten iron, and in the steelmaking process, vanadium slag is obtained by blowing oxygen and is comprehensively utilized. About 25% of titanium enters the molten iron in the form of titanium nitride or titanium carbide, and the remaining most part enters the blast furnace slag. Because the TiO2 content in the slag is low and exists in the form of difficult-to-utilize perovskite, there is no good utilization technology, and the recovery and utilization rate of titanium is 0%. Therefore, the smelting of vanadium-titanium ore by a blast furnace has the following serious deficiencies: long process, large system, complex process, and must use coke; high energy consumption and high production cost, large emission of air pollutants and serious environmental pollution; under the smelting conditions of a blast furnace, the slag and molten iron have a large viscosity and poor fluidity, and the smelting difficulty is increased; the cold strength and low-temperature reduction pulverization performance of vanadium-titanium ore are poor, and cannot meet the smelting requirements; titanium resources cannot be recovered, and a large amount of titanium resources are discarded or filled, which causes serious pollution to the surrounding environment (especially the underground water system).

[0005] In the non-blast furnace smelting of vanadium-titanium ore, enterprises and research institutions at home and abroad have also carried out a lot of research and practice. After mixing concentrate, coal and limestone, heating in a multi-chamber furnace, reducing in a rotary kiln, and then deep reducing and melting in a rectangular electric furnace, both iron and vanadium are well utilized, and the slag contains 30% titanium dioxide, which is still not recycled. And in the production process of this process, there is a technical problem of easy ring formation in the rotary kiln. Some research structures begin to try to use hydrogen shaft furnace direct reduction process, and the process flow is: raw material processing → oxidized pellet → hydrogen shaft furnace direct reduction → titanium extraction by melting → vanadium extraction by converter. This process has the problems of easy powdering and insufficient strength when making pellets. The existing non-blast furnace smelting of vanadium-titanium ore has the problems of small single-machine production scale, ash in the reducing agent entering the titanium slag, resulting in a decrease in the grade of the titanium slag, and the titanium resource has not been effectively utilized. The shaft furnace process needs to strengthen the pellet. It can be seen that, combined with the utilization of vanadium-titanium magnetite resources and the prospect of vanadium and titanium resources in the new energy field, exploring the non-blast furnace utilization process of vanadium-titanium ore can ensure the smooth progress of the process, make efficient use of iron, vanadium and titanium, and reduce the dependence on external resources, which has practical economic value and social value. SUMMARY

[0006] In order to solve the technical problems of large demand for traditional blast furnace reducing agent coke, insufficient supply of coke, insufficient strength of pellets in non-coking method, and low grade of titanium slag in the prior art, a preparation method of iron-carbon composite charge and iron-carbon composite charge are provided.

[0007] The present application provides a method for directly reducing vanadium-titanium magnetite by using a gas-based shaft furnace, comprising:

[0008] Mixing: 10-15 parts by weight of pulverized bituminous coal, 80-85 parts by weight of vanadium-titanium magnetite powder, 5-10 parts by weight of high-temperature promoter and 8-12 parts by weight of hot water are mixed uniformly to obtain a mixture;

[0009] Pelletizing: the mixture is pelletized to obtain pellets without heating, drying or roasting the pellets;

[0010] Reduction: the pellets are placed in a gas-based shaft furnace for direct reduction to obtain finished vanadium-titanium direct reduced iron (DRI).

[0011] In some embodiments, no other auxiliary mineral material is added in the mixing step.

[0012] In some embodiments, the mixing step comprises: 10 parts by weight of pulverized bituminous coal, 85 parts by weight of vanadium-titanium magnetite powder, 5 parts by weight of high-temperature promoter and 10 parts by weight of hot water are mixed uniformly to obtain a mixture.

[0013] In some embodiments, the high-temperature accelerator is bitumen powder and / or tar. The added bitumen powder or tar functions as a cold-state binder. The reduction reaction can be carried out from the inside out, and the voids left by the decomposition and escape of the bituminous coal powder are filled by the overflow of the bitumen and tar accelerator, which fills the gaps and avoids loose pellets. The bituminous coal undergoes carbonization in a reducing atmosphere, enhancing the mechanical properties of the pellets.

[0014] In some embodiments, the ash content of the bituminous coal powder is ≤12%. Specifically, the bituminous coal with ash content ≤12% is ground by a grinding machine to a fine powder with particle size of -200 mesh accounting for more than 80%, and the moisture content is based on smooth grinding production (generally H20 < 8%). The vanadium-titanium magnetite concentrate powder has a particle size of -300 mesh (natural particle size after beneficiation), and the bitumen powder has a particle size of -200 mesh. Controlling the particle size and moisture content helps the pellets to form.

[0015] In some embodiments, the temperature of the hot water is ≥80℃. Water with a temperature of 80℃ or higher is beneficial to promote the toughness of the mixture, achieve the effect of difficult material, and improve the forming rate and strength during ball pressing.

[0016] In some embodiments, in the balling step, the ball pressing strength is ≥500N, and the ball forming rate is ≥90%. Reasonable particle size distribution of raw materials combined with hot water with a temperature of 80℃ or higher ensures the strength and forming rate of the ball, and the dried and baked pellets can meet the use requirements.

[0017] In some embodiments, the reduction step includes a low-temperature reduction section and a high-temperature reduction section, and the reduction time is 5-7 hours, preferably 6 hours.

[0018] In some embodiments, the temperature of the low-temperature reduction section is 400℃-500℃, and the temperature of the high-temperature reduction section is 650℃-1050℃.

[0019] In some embodiments, the temperature of the low-temperature reduction section is 450℃, and the temperature of the high-temperature reduction section is 800℃-900℃.

[0020] The principle of action of the application consists in that:

[0021] The present application 100% uses vanadium-titanium ore, without adding other auxiliary mineral materials, adopts non-blast furnace technology, gas-based shaft furnace direct reduction process, uses high reduction potential coal gas as reducing agent, without adding additional reducing agent, the reducing gas comes from the gasification reaction of carbon in the prepared bituminous coal with hot water at a temperature above 80 DEG C at high temperature, produces the reducing gas CO and H2 required for reduced iron, the reaction formula is H2O+C→CO+H2, achieves the purpose of saving energy consumption; in addition, using water at a temperature above 80 DEG C is beneficial to promote the toughness of the mixture, achieves the effect of difficult material, ensures that the forming rate is above 90% and the strength is above 500 N when balling, the-200 mesh coal powder and the-300 mesh iron powder are fully mixed in the strong mixer to ensure that the organic volatile matter of the coal powder is rapidly decomposed, the reducing gas produced reacts with FeOx and V2O5, FeOx+H2→[Fe]+H2O, V2O5+H2→[V]+H2O or FeOx+CO→[Fe]+CO2, V2O5+CO→[V]+CO2, and a series of reactions, the water and carbon dioxide flow in the opposite direction with the gas flow, and after the cooling device, the washing and purification decarburization system, the remaining coal gas is returned to the pipe network for recycling. The added asphalt powder acts as a cold binder, the thermal decomposition gas escapes to promote the reduction reaction, which can be carried out from inside to outside, the void left by the coal powder decomposition and escape is filled with asphalt promoter overflow, which fills the vacancy and avoids loose ball material, the bituminous coal occurs carbonization reaction under the reducing gas atmosphere. The reduced FeOx produces metal [Fe] and [C] to form a hinge, which strengthens the high temperature strength of the ball material, the carbon content of the carbonized carbon C reaches about 6%, which will provide a reducing agent for subsequent melting and separation deep reduction, and improve the electrical resistance ratio of the material, which provides convenience for melting and separation energy saving.

[0022] Compared with the prior art, the present application achieves the following technical effects:

[0023] (1) The present application 100% uses vanadium-titanium ore, without adding other auxiliary mineral materials, adopts non-blast furnace technology, gas-based shaft furnace direct reduction process, the carbon in the prepared bituminous coal gasifies with hot water at high temperature, produces CO and H2 required for reduced iron, without adding additional reducing agent, fundamentally solves the technical problem of insufficient coke supply in the blast furnace reduction of vanadium-titanium magnetite in the prior art.

[0024] (2) The present application adds hot water above 80 DEG C in the material, which is beneficial to promote the toughness of the mixture, achieves the effect of difficult material, combines with a certain required pressure (above 500 N), ensures that the forming rate is above 90% when balling, and the phenomenon of loose ball material is not easy to occur, the balling is directly sent into the gas-based direct reduction shaft furnace for drying and reduction, omitting the pelletizing process, without pelletizing process, compared with the traditional long process ironmaking process, one ton of molten iron directly reduces carbon emission by more than 25 kg.

[0025] (3) The present application uses bituminous coal with ash content of less than or equal to 12%, which simultaneously plays the role of binder, reducing agent and carbon additive, and the bituminous coal undergoes carbonization reaction under reducing atmosphere, and the C content after carbonization reaches about 6%, thus providing convenience for the next process.

[0026] (4) Compared with the traditional vanadium-titanium ore processing process, the present application has short process flow, low energy consumption, small environmental pollution and no solid waste emission; the whole process can reduce CO2 emission by more than 25%, and can realize zero emission if hydrogen is used as reducing agent; NO X , SO2 emission is reduced by more than 90%, the recovery rates of titanium, vanadium and iron are more than 95%, 75% and 90% respectively, the resource utilization efficiency is improved, and the energy saving and environmental protection benefits are remarkable. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a process flow diagram of the method for directly reducing vanadium-titanium magnetite by using a gas-based shaft furnace in the present application;

[0028] Figure 2 is a photo of the finished product cold-state vanadium-iron DRI prepared in the embodiment of the present application. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described below by specific embodiments in combination with the drawings. It should be understood that one or more steps mentioned in the present application do not exclude other methods and steps before and after the combined steps, or other methods and steps can be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present application and do not limit the scope of the present application. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and is not limited to the arrangement order of each method or the scope of the implementation of the present application. Changes or adjustments of the relative relationship, without substantial technical content changes, can also be considered as the implementation scope of the present application.

[0030] The raw materials and instruments used in the embodiments are not specifically limited in source, and can be purchased in the market or prepared according to the conventional methods well known to those skilled in the art.

[0031] The process flow diagram of the method for directly reducing vanadium-titanium magnetite by using a gas-based shaft furnace provided by the present application is shown in Figure 1 as follows:

[0032] (1) three kinds of materials according to the weight ratio of 10-15 parts of bituminous coal powder, 80-85 parts of vanadium titanium magnetite concentrate powder, 5-10 parts of high temperature promoter, after weighing, add 300-500 kg per batch into the intensive mixer, plus 8-12 parts of water at 70-90℃, mix for 3-5 min; wherein, the bituminous coal is ground by a pulverizer to a particle size of more than 80% of -200 mesh fine powder, the moisture is based on smooth grinding production (generally H20<8%), the particle size of vanadium titanium magnetite concentrate reaches -300 mesh (natural particle size after beneficiation), -200 mesh asphalt powder;

[0033] (2) the mixed material is added to the roller-type ball press for balling, the shape and size of the ball are not limited, and the olive kernel type or oval shape is preferred, and the diameter is preferably 15-20 mm, and the thickness is more than 10 mm;

[0034] (3) the pressed ball is directly put into the intermediate bin, and is sent into the gas-based direct reduction shaft furnace by a vertical belt or a small material car: after the ball material is heated and dried, the reduction reaction occurs at the same time, and the ball material is sequentially lowered along the shaft furnace, and the Fe, V in the reduction section at 650-1050℃ is reduced to elemental iron and vanadium, the whole process from entering to leaving takes about 6 hours. The metallization rate of the reduced vanadium titanium magnetite ball is more than 80%, the iron is reduced by more than 90%, the vanadium is reduced by more than 70%, and the titanium is not reduced.

[0035] The finished vanadium iron DRI is cooled (CDRI) for use or made into hot briquetted iron (HBI) for export use, or directly enters the subsequent melting system for direct smelting application as hot direct reduced iron (HDRI).

[0036] In some embodiments, the composition of the vanadium titanium magnetite concentrate raw material is as shown in Table 1:

[0037] Table 1 Main chemical components of vanadium titanium magnetite concentrate

[0038]

[0039] In the table, TFe is the total iron content, TFe=Fe2O3x112 / 160+FeOx56 / 72.

[0040] Take the above vanadium-titanium magnetite concentrate 85 parts by weight, 10 parts by weight of bituminous coal powder, 5 parts by weight of pitch powder, plus 10 parts by weight of hot water at 80℃, mix evenly, balling, without pellet preparation, roasting, directly into the gas-based direct reduction shaft furnace, through the shaft furnace top cooler and 450℃ reduction gas in this energy quality exchange, at this time the ball material is heated and dried at the same time the reduction reaction occurs, in turn along the vertical furnace downlink, in the high temperature reduction section of 650℃-1050℃, the length of this reduction section is about 10m, Fe, V in it are reduced to elemental iron and vanadium, the whole process from the entrance to the place needs about 6 hours, to get finished vanadium-titanium DRI. The metallization rate of the reduced vanadium-titanium magnetite ball is more than 80%, iron is 90% reduced, vanadium is 70% reduced, and titanium is not reduced.

[0041] The shape of the finished vanadium-titanium DRI after reduction is as shown in Figure 2 The composition of the finished vanadium-titanium DRI is shown in Table 2.

[0042] Table 2 Chemical composition of vanadium-titanium DRI

[0043]

[0044] In the table, TFe is the total iron content;

[0045] MFe is the magnetic iron content;

[0046] Natural refers to the natural content in the raw material.

[0047] The present application is to use non-blast furnace technology, gas-based shaft furnace direct reduction process to treat vanadium-titanium ore, which can use vanadium-titanium ore as raw material by 100%, use high reduction potential coal gas as reducing agent, the product purity is high (titanium slag grade > 45%, vanadium slag grade > 20%), which can be used as subsequent vanadium-titanium deep processing raw material, realizing the comprehensive recovery and utilization of vanadium, titanium and iron resources in vanadium-titanium ore; using smelting separation titanium converter to extract vanadium process, which is beneficial to slag-iron separation, and improves the metal recovery rate (titanium, vanadium and iron recovery rate is more than 95%, 75% and 90% respectively); compared with the traditional vanadium-titanium ore treatment process, the process flow is short, the energy consumption is low, the environmental pollution is small, and there is no solid waste emission; the whole process CO2 emission is reduced by more than 25%, if hydrogen is used as reducing agent, zero emission can be realized, NO X , SO2 emission is reduced by more than 90%, improves the resource utilization efficiency, and the energy saving and environmental protection benefit is remarkable.

[0048] The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A method for directly reducing vanadium-titanium magnetite by using a gas-based shaft furnace, characterized in that, The application relates to a preparation method of vanadium-titanium direct-reduced iron, and belongs to the technical field of metallurgy. Mixing: 10-15 parts by weight of pulverized bituminous coal, 80-85 parts by weight of vanadium-titanium magnetite concentrate, 5-10 parts by weight of a high-temperature promoting agent and 8-12 parts by weight of hot water are uniformly mixed to obtain mixed materials; Pelletizing: the mixed materials are pelletized to obtain pellets, and the pellets do not need to be heated, dried or baked; Reducing: the pellets are directly reduced in a gas-based shaft furnace to obtain finished vanadium-titanium direct-reduced iron; The mixing step does not need to add other auxiliary materials; The temperature of the hot water is higher than or equal to 80 DEG C.

2. The method of claim 1, wherein, The mixing step includes the following steps: 10 parts by weight of pulverized bituminous coal, 85 parts by weight of vanadium-titanium magnetite concentrate, 5 parts by weight of a high-temperature promoting agent and 10 parts by weight of hot water are uniformly mixed to obtain mixed materials.

3. The method of claim 1, wherein, The high-temperature promoting agent is bitumen powder and / or tar.

4. The method of claim 1, wherein, The ash content of the pulverized bituminous coal is less than or equal to 12%.

5. The method of claim 1, wherein, In the pelletizing step, the pelletizing strength is higher than or equal to 500 N, and the pelletizing forming rate is higher than or equal to 90%.

6. The method of claim 1, wherein, The reducing step includes a low-temperature reducing section and a high-temperature reducing section, and the reducing time is 5-7 hours.

7. The method of claim 6, wherein, The temperature of the low-temperature reducing section is 400 DEG C.-500 DEG C., and the temperature of the high-temperature reducing section is 650 DEG C.-1050 DEG C.

8. The method of claim 6, wherein, The temperature of the low-temperature reducing section is 450 DEG C., and the temperature of the high-temperature reducing section is 800 DEG C.-900 DEG C.

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