Vanadium-titanium iron ore coal-based hydrogen metallurgical rotary kiln steelmaking method

Abstract

The application discloses a kind of vanadium-titanium iron ore coal-based hydrogen metallurgical rotary kiln steelmaking methods, using iron ore direct reduction produces metallized material, again through dry grinding dry selection produces iron concentrate and high-grade vanadium-titanium tailings, iron concentrate is smelted again through electric furnace to generate high-purity molten iron and rich vanadium-titanium slag;Above process iron utilization rate can reach more than 85%, the yield of titanium and vanadium can reach more than 60%;The comprehensive utilization rate of various resources is much higher than blast furnace (the utilization rate of iron, vanadium and titanium is 70%, 47% and 21% respectively) and other non-blast furnace processes, can give full play to the value of each valuable element in vanadium-titanium iron ore.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical and mineral engineering technology, and relates to a method for producing steel from vanadium-titanium iron ore using a coal-based hydrogen metallurgical rotary kiln. Background Technology

[0002] Vanadium-titanium magnetite contains various valuable elements such as cobalt, chromium, nickel, gallium, and scandium, and has considerable comprehensive utilization value. In nature, more than 90% of vanadium and titanium resources exist in the form of vanadium-titanium magnetite.

[0003] The traditional methods for utilizing vanadium-titanium magnetite mainly include the blast furnace method and the non-blast furnace method. The blast furnace method was the earliest method for processing vanadium-titanium magnetite, and it still holds the mainstream position in vanadium-titanium magnetite processing due to its large processing capacity and relatively low cost.

[0004] The following problems exist when processing vanadium-titanium magnetite using the blast furnace method: (1) Ordinary iron concentrate needs to be added. Titanium will be reduced in the blast furnace to form Ti(C,N), which will increase the viscosity of the slag, reduce the permeability of the furnace, and increase the difficulty of operation. Therefore, a certain proportion of ordinary high-grade iron ore needs to be added during the sintering process. Generally, the addition ratio can reach about 20%. (2) Resource utilization rate is low. The utilization rates of iron, vanadium, and titanium are 70%, 47%, and 21%, respectively; (3) Dependence on coke. The blast furnace process requires coke as a framework, heating agent and reducing agent due to the permeability requirements. The average coke consumption per ton of iron in my country is about 350 kg. (4) Large amounts of solid waste and hazardous waste are emitted. In the sintering process, the amount of high-temperature waste gas emitted for every ton of iron produced is 6500 m³. 3 The above are the sintering smoke and dust PM10, SO2, NO. X Dioxin emissions account for more than 60% of the total emissions from steel enterprises; in terms of the coking process, the coke oven quenching process emits a large amount of smoke and dust, and the smoke and dust emissions from coking plants account for more than 30% of the total emissions from steel enterprises; SO2, ammonia, benzene, benzopyrene and other waste gases and wastewater that are toxic to humans and organisms account for more than 80% of the total emissions from enterprises.

[0005] Non-blast furnace methods for processing vanadium-titanium magnetite mainly include the "vanadium-first, iron-later process" and the "iron-first, vanadium-later process." The "vanadium-first, iron-later process" is represented by the sodium roasting vanadium extraction-rotary kiln pre-reduction-electric furnace melting process. This process can achieve a vanadium recovery rate of up to 80%, but it has problems such as being only suitable for vanadium-titanium magnetite with a high vanadium content (>1%), large sodium salt consumption, high cost, easy pulverization of residual sodium salt pellets, poor stability of rotary kiln reduction, and failure to recover iron and titanium.

[0006] The "iron-first-vanadium-later process" can be mainly divided into the following process routes: rotary kiln pre-reduction-electric furnace final reduction and smelting process, rotary hearth furnace pre-reduction-electric furnace final reduction and smelting process, vertical shaft furnace pre-reduction-electric furnace final reduction and smelting process, fluidized bed pre-reduction-electric furnace final reduction and smelting process, deep reduction-electric furnace smelting process, and reduction-grinding and classifying process.

[0007] Rotary kiln pre-reduction followed by electric arc furnace final reduction smelting is a relatively mature non-blast furnace process. Two companies worldwide (Hayveld of South Africa and Steel New Zealand) use this process for industrial production. This process produces vanadium-containing molten iron and titanium slag. The main difference between the two companies is that Steel New Zealand uses sea sand iron ore powder as raw material, while Hayveld uses vanadium-titanium magnetite. A major problem with this process is that the titanium-containing slag produced is either discarded or used as paving material, failing to be utilized effectively.

[0008] The rotary hearth furnace pre-reduction-electric furnace final reduction melting process has not yet been successfully applied in industrial applications. In 2007 and 2010, Panzhihua Longmang Mining and Metallurgy Co., Ltd. and Panzhihua Iron and Steel Research Institute successively built 70,000-ton and 100,000-ton rotary hearth furnace pilot production lines, respectively, and equipped them with electric furnaces for titanium slag smelting. During the long-term testing of the pilot lines, the furnace bottom rose, which seriously affected the smooth operation. At the same time, the rotary hearth furnace is limited by the combustion heating and radiant heat transfer in the furnace, and generally uses a single-layer pellet feeding method, resulting in very low capacity. All of these processes have now been shut down.

[0009] The gas-based vertical shaft furnace process for reducing ordinary iron ore has been scaled up and is highly mature. Currently, the achievable reduction temperature is around 900℃. Between 1977 and 1979, Chengdu Iron and Steel Plant, in collaboration with Panzhihua Iron and Steel Research Institute and other units, conducted a 5m... 3 In a semi-industrial trial of a gas-based vertical shaft furnace-1.5t electric arc furnace, the metallization rate was greater than 85% when the reduction zone temperature was above 1100℃, the melting temperature was controlled at 1510-1550℃, the iron recovery rate was greater than 95.9%, and the vanadium and titanium recoveries in the molten slag were greater than 85% and 99.3%, respectively. The main problems with this process are as follows: (1) Vanadium-titanium magnetite oxidized pellets are prone to expansion and sticking during the reduction process, which leads to poor feeding and further reduces the metallization rate; (2) Poor economic efficiency. The total investment of gas-based vertical shaft furnace projects with a capacity of one million tons in China is about RMB 1.9 billion, including the furnace body, feeding and discharging system, cooling system, gas circuit system, as well as supporting energy system and information system. (3) The reduction temperature is low, the high temperature zone of the gas-based vertical furnace pre-reduction is extremely narrow, the overall reduction reaction kinetics are poor, and the reduction advantage of the reducing gas cannot be fully utilized. This is the main reason why the vertical furnace reduction technology is difficult to achieve a high metallization rate.

[0010] The FINEX process is a typical example of fluidized bed direct reduction. Around the 1980s, the Institute of Chemical Metallurgy of the Chinese Academy of Sciences conducted a ton-scale industrial test of fluidized bed reduction of vanadium-titanium magnetite concentrate in Zaozhuang, Shandong. The reactor consisted of two stages: a pre-reduction fluidized bed and a reduction fluidized bed. However, the problem of iron particle adhesion and flow loss during direct reduction has not yet been completely solved.

[0011] Vanadium-titanium magnetite concentrate is subjected to deep reduction treatment using rotary kilns (or vertical shaft furnaces, rotary hearth furnaces), and the pre-reduced product is then transferred to an electric furnace for melting and separation. This process enriches vanadium in titanium slag, forming vanadium-titanium slag and molten steel, which are then separated using pyrometallurgical or hydrometallurgical processes. This method significantly reduces the energy consumption of electric furnaces. Numerous domestic universities and research institutions, including the Institute of Process Engineering of the Chinese Academy of Sciences, Northeastern University, Panzhihua Iron and Steel Research Institute, and COSRED, have conducted research on this approach. However, due to the inability to quickly solve the problem of deep reduction of vanadium-titanium magnetite, these processes have remained at the laboratory research level.

[0012] The reduction-grinding process, operating below the ore's melting temperature, selectively reduces iron oxides in vanadium-titanium magnetite to metallic iron by exploiting the differences in the reducibility of iron, vanadium, and titanium oxides. Vanadium and titanium remain as oxides. By controlling the reduction conditions, the metallic iron particles are grown to a certain size, and iron concentrate and vanadium-titanium-rich materials are obtained through magnetic separation. Institutions such as the Changsha Research Institute of Mining and Metallurgy, Central South University, Northeastern University, and Panzhihua Iron and Steel Group have conducted research on this process. Similar to the deep reduction-electric furnace smelting process, none of these institutions have been able to solve the problem of rapid deep reduction of vanadium-titanium magnetite, resulting in no substantial progress.

[0013] In summary, traditional metallurgical processes cannot effectively process vanadium-titanium magnetite. The fundamental reason is that traditional metallurgical processes are based on carbon as a reducing agent. However, carbon metallurgy is limited by factors such as the weak reduction and penetration capabilities of CO, and cannot solve the problem of high reduction rate of vanadium-titanium magnetite under solid-state conditions.

[0014] The carbon metallurgical process has not adequately addressed the reduction of vanadium-titanium magnetite in the solid state; it can only be solved in the molten liquid state. However, during final reduction in the molten liquid state, large amounts of silicon, manganese, vanadium, and carbon in the slag are simultaneously reduced and incorporated into the molten iron. This creates numerous problems for subsequent steelmaking and the extraction of titanium and vanadium, resulting in a significantly higher overall production cost compared to the blast furnace method. Summary of the Invention

[0015] The purpose of this invention is to provide a rotary kiln steelmaking process for vanadium-titanium iron ore in coal-based hydrogen metallurgy, in order to solve the problems of low reduction rate and low resource utilization of vanadium-titanium magnetite under solid-state conditions in traditional processes.

[0016] To achieve the above objectives, the present invention adopts the following technical solution: (1) Crush the iron ore to a particle size of 0~50mm; screen and select 20~50mm particle size coal and 0~50mm particle size iron ore, mix them evenly, and then add the mixture to the rotary kiln from the feed end of the rotary kiln. The total volume of the material should not exceed 25% of the internal space of the rotary kiln. The iron ore is vanadium-titanium iron ore with an iron grade of 40-60%, titanium content of over 5%, and vanadium content of over 0.4%; the volatile matter content of the 20-50mm particle size coal is 10-20%; the mass ratio of 0-50mm particle size iron ore to 20-50mm particle size coal is 100:40-50.

[0017] The above mixture tumbles and moves forward inside the rotary kiln; the counter-current high-temperature flue gas heats the surface material through radiation and convection; the high-temperature kiln wall heats the bottom material through conduction and radiation; all materials gradually heat up from the surface inward during the heating process; (2) Control the total time of the mixture in the kiln in step 1) to 150~210 min, control the temperature of the highest temperature section of the mixture to 1100~1200℃, and control the final discharge temperature to 800~900℃; After the temperature of the mixture reaches 1100~1200℃, 5~30mm coal particles are screened and injected into the high-temperature section from the discharge end of the rotary kiln, and the reaction time is controlled at 30~60min. Among them, the volatile matter content of 5-30mm coal is over 40%, and the amount of 5-30mm coal fed into the kiln accounts for 40-50% of the amount of 0-50mm iron ore fed into the kiln at the same time; (3) Cool the material discharged from the rotary kiln in step 2) to below 200°C, and control the cooling time to within 50 minutes. Then, magnetic separation is used to obtain metallized material with an iron content of 55-75% and non-magnetic material with residual carbon as the main component. (4) The non-magnetic material obtained in step 3) is fed back to the feed end of the rotary kiln to replace the 20-50mm particle size coal with the same calorific value. The amount of non-magnetic material added should be 40-50% of the amount of 20-50mm particle size coal fed into the kiln at the same time; after replacing the equivalent amount of 20-50mm particle size coal, the total volatile matter of the mixture of non-magnetic material and 20-50mm particle size coal should be 10-20%; (5) The metallized material obtained in step 3) is dry-ground and dry-separated, and after tailings are discarded, iron concentrate with an iron grade of 75-85% and high-grade vanadium-titanium tailings are obtained. (6) Press the iron concentrate obtained in step 4) into iron blocks with a diameter of 30-50 mm and dry them; the moisture content after drying is controlled within 3% and the strength is controlled above 600 N / piece. (7) Put 5-15% of the rated feed amount of ordinary scrap steel into the electric furnace under no-load conditions, control the power of the electric furnace to 40-60% of the rated power, and put the iron blocks obtained in step 6) into batches when the scrap steel begins to melt. At the same time, control the power of the electric furnace to 100% of the rated power. Control the average thickness of the slag to <60mm during the melting process. When the temperature of the molten steel reaches 1580-1620℃, hold it for 5-8 minutes and then tap the steel. You can get pure molten steel with an iron content of more than 99% and vanadium-titanium rich molten slag.

[0018] The reaction principle inside the coal-based hydrogen metallurgical rotary kiln is as follows: (1) When the mixture enters the rotary kiln, the moisture in the mixture will be gradually removed from the surface to the inside when the temperature reaches above 100℃. (2) When the temperature of the mixture reaches above 300℃, the coal with a particle size of 20~50mm will undergo pyrolysis, producing reducing gases such as H2 and CO; (3) When the temperature of the mixture is between 300 and 570°C, the reducing gas mainly composed of H2 produced by coal pyrolysis will reduce the main phase Fe3O4 and auxiliary phase FeTiO3 in the iron ore from the surface to the inside, respectively generating Fe, H2O, CO2 and Fe, TiO2, H2O, CO2. (4) When the temperature of the mixture is 570~810℃, the reducing gas mainly composed of H2 produced by coal pyrolysis will gradually reduce the main phase Fe3O4 and auxiliary phase FeTiO3 in the iron ore from the surface to the inside. First, FeO, H2O, CO2 and FeO, TiO2, H2O, CO2 are generated respectively, and then Fe, H2O, CO2 and Fe, TiO2, H2O, CO2 are generated respectively. (5) When the temperature of the mixture is 810~1100℃, the pyrolysis process of coal and the reduction process of pyrolysis gas in the mixture are basically completed; the H2O and CO2 generated in step 4) will react with the residual carbon inside the material layer to generate H2 and CO, which will gradually reduce the main phase Fe3O4 and auxiliary phase FeTiO3 in the iron ore from the surface to the inside. The reduction process is the same as in step 4). (6) When the temperature of the mixture is 1100~1200℃, 5~30mm particle size coal is injected from the discharge end of the rotary kiln to the high temperature section; the 5~30mm particle size coal rolls in the material layer and heats up rapidly, gradually carrying out the first pyrolysis of the coal to generate H2, CO and macromolecular substances such as tar, benzene, naphthalene, alkanes, alkenes, and hydrocarbons; the macromolecular substances such as tar, benzene, naphthalene, alkanes, alkenes, and hydrocarbons continue to heat up in the material layer and complete the full pyrolysis to generate reducing gases mainly composed of H2 and CO; (7) The reducing gas generated in step 6) passes through the pores formed by the previous reduction in the material layer and further reduces the main phase Fe3O4 and auxiliary phase FeTiO3 in the iron ore. First, FeO, H2O, and CO2 are generated respectively, as well as FeO, TiO2, H2O, and CO2. Then, Fe, H2O, and CO2 are reduced respectively, as well as Fe, TiO2, H2O, and CO2. The newly generated H2O and CO2 will continue to react with the carbon inside the material layer to generate H2 and CO, which will continue to reduce Fe3O4 and FeTiO3 in the depth of the iron ore. In this process, due to the fact that H2 has a better reducing ability than CO, H2 will be the main reducing agent for reduction, and most of the CO will escape from the material layer and be used as fuel for combustion and heating. The material continues to tumble forward towards the kiln head and is discharged, completing the reduction process. At this point, the metallization rate of iron can reach over 90%, and titanium and vanadium exist in the form of TiO2 and V2O5, respectively.

[0019] The advantages of this invention compared to traditional vanadium-titanium-iron ore resource comprehensive utilization processes are as follows: (1) No need to add ordinary iron concentrate Compared with molten reduction methods such as blast furnaces, this invention uses a gas-solid reaction method, which solves the problems of increased slag viscosity, decreased permeability in the furnace, and increased operation difficulty in the molten reduction of pure vanadium-titanium magnetite. Therefore, there is no need to add ordinary iron concentrate. (2) High resource utilization rate This invention uses direct reduction of iron ore to produce metallized materials, followed by dry grinding and separation to produce iron concentrate and high-grade vanadium-titanium tailings. The iron concentrate is then smelted in an electric furnace to produce high-purity molten iron and vanadium-titanium-rich slag. In the above process, the utilization rate of iron can reach more than 85%, and the yields of titanium and vanadium can both reach more than 60%. The comprehensive utilization rate of various resources is much higher than that of blast furnace (the utilization rates of iron, vanadium, and titanium are 70%, 47%, and 21%, respectively) and other non-blast furnace processes. (3) Cancel the use of coke This invention uses high-volatile lignite, which can solve the dependence on coke in the traditional comprehensive utilization process of vanadium-titanium-iron ore resources in blast furnaces; (4) Small amount of solid waste and hazardous waste emissions This invention eliminates sintering and coking processes, thereby reducing waste gas emissions and preventing the emission of toxic waste gases and wastewater such as sintering smoke and dust, quenching smoke and dust, SO2, ammonia, benzene, and benzo[a]pyrene, which are harmful to humans and organisms. This invention also employs hydrogen metallurgy technology, which can reduce CO2 emissions. (5) Fast recovery speed This invention employs a direct reduction method for vanadium-titanium iron ore, primarily using hydrogen metallurgy and secondarily using carbon metallurgy. This method can achieve a metallization rate of over 90% in approximately 3 hours, which is significantly higher than traditional carbon metallurgy processes (which typically require 6-10 hours) and hydrogen metallurgy processes such as vertical shaft furnaces (which typically require approximately 8 hours). (6) Good overall economic performance This invention utilizes low-cost vanadium-titanium magnetite and lignite, solving the problem of lack of thermal connection between coke ovens, sintering, and blast furnaces, and has a fast reduction rate, resulting in a low overall process cost. This invention employs a rotary kiln device, which has high thermal efficiency and low construction cost. This invention has a high resource utilization rate and can fully utilize the value of each valuable element in the vanadium-titanium iron ore. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0021] The present invention will be further explained and described below with reference to specific embodiments. Example

[0022] (1) A vanadium-titanium magnetite from a certain place in South Africa was used. The average iron content of the ore was 53.08%, titanium content was 14.48%, and vanadium content was 1.78%. The iron ore was crushed to a particle size of 0~50mm. (2) A modified coal from Xinjiang was used, with volatile matter of 10.6%, fixed carbon of 75.76%, ash content of 11.31%, and calorific value of 24507 KJ / Kg. The 20~50mm particle size was selected by sieving. (3) The non-magnetic material produced by the early discharge of the rotary kiln and magnetic separation is used. The non-magnetic material is mainly composed of residual carbon, with volatile matter of 2.72%, fixed carbon of 77.52%, ash content of 22.35%, and calorific value of 22375 KJ / Kg. (4) A certain type of lignite from Xinjiang was used, with volatile matter of 49.5%, fixed carbon of 47.6%, ash content of 4.5%, and calorific value of 21203 KJ / Kg. The particle size was selected from 5 to 30 mm by sieving. (5) 533 tons of iron ore crushed to 0~50mm particle size, 231 tons of modified coal of 20~50mm particle size and 98 tons of non-magnetic material were mixed evenly through a granulator with an internal diameter of 1.2m. Then, the mixture was fed into the rotary kiln from the feed end of the rotary kiln with an internal diameter of 2.2m and a length of 48m via a conveyor belt. The hourly feed rate was 20.5 tons and the material was in the kiln for 2 hours and 50 minutes. The total volume of the material reached 22.1% of the internal space of the rotary kiln. (6) The above mixture tumbles and moves forward in the rotary kiln; the counter-current high-temperature flue gas heats the surface material through radiation and convection; the high-temperature kiln wall heats the bottom material through conduction and radiation; all materials gradually heat up from the surface to the inside during the heating process; (7) After controlling the temperature of the highest temperature section of the mixture to 1100~1200℃, 108 tons of 5~30mm particle size coal were screened and injected from the discharge end of the rotary kiln to the high temperature section, and the temperature of the material discharged from the discharge end of the rotary kiln was controlled to 800~900℃. (8) The material discharged from the rotary kiln is cooled to 50~80℃ by a slag cooler with an inner diameter of 2m and a length of 15m, and the cooling time is 30~50min; (9) After being cooled, the material discharged from the rotary kiln outlet is magnetically separated by an online drum magnetic separator to obtain 415 tons of metallized material with an iron content of 70.21% and 107 tons of non-magnetic material mainly composed of residual carbon. (10) The metallized material produced by magnetic separation is dry-grinded and dry-separated, and after tailings are discarded, 357 tons of iron concentrate with an iron grade of 76.58%, titanium content of 12.02% and vanadium content of 1.71% and 58 tons of vanadium-titanium tailings with an iron grade of 18.68%, titanium content of 41.20% and vanadium content of 5.66% are obtained. (11) Iron concentrate powder, pellet binder (bentonite), and water are pressed into briquettes in a ratio of 100:2:11 to form iron blocks with a diameter of 30~50mm and then dried. The moisture content after drying is controlled at 1.8%, the strength is 880N / piece, and 365 tons of iron concentrate powder briquettes are prepared. (12) 7 tons of ordinary scrap steel were put into a 50-ton electric furnace under no-load conditions. The power of the electric furnace was controlled at 40% of the rated power. When the scrap steel began to melt 6 minutes later, 35 tons of iron concentrate briquettes were added in 3 batches. When the iron concentrate briquettes were added for the first time, the power of the electric furnace was controlled at 100% of the rated power. During the melting process, the average thickness of the slag was controlled to be <60mm. If it exceeded this, the slag was dumped. When the temperature of the molten steel reached 1600℃, it was held for 5 minutes before tapping the steel. The above method was used to continuously produce 10 heats, resulting in 260 tons of pure molten steel with an iron content of 99.65% and 110.8 tons of vanadium-titanium rich molten slag with an iron content of 19.42%, a titanium content of 34.60%, and a vanadium content of 5.21%.

Claims

1. A method for steelmaking in a coal-based hydrogen metallurgical rotary kiln using vanadium-titanium iron ore, characterized in that, Includes the following steps: (1) Crush the iron ore to 0~50mm size; screen and select 20~50mm size coal and 0~50mm size iron ore, mix them evenly, and then add the mixture quantitatively to the rotary kiln from the feed end of the rotary kiln; (2) Control the total time of the mixture in the kiln in step 1) to 150~210 min, control the temperature of the highest temperature section of the mixture to 1100~1200℃, and control the final discharge temperature to 800~900℃; (3) Cool the material discharged from the rotary kiln in step 2) to below 200°C, and then magnetically separate it to obtain metallized material with an iron content of 55-75% and non-magnetic material mainly composed of residual carbon. (4) The non-magnetic material obtained in step 3) is fed back to the feed end of the rotary kiln to replace the 20-50mm particle size coal with the same calorific value. (5) The metallized material obtained in step 3) is dry-ground and dry-separated, and after tailings are discarded, iron concentrate with an iron grade of 75-85% and high-grade vanadium-titanium tailings are obtained. (6) Press the iron concentrate obtained in step 5) into iron blocks with a diameter of 30-50 mm and dry them; the moisture content after drying is controlled within 3% and the strength is controlled above 600 N / piece. (7) The iron block obtained in step 6) is put into an electric furnace for smelting and refining to obtain pure molten steel with an iron content of more than 99% and vanadium-titanium rich molten slag. In step 1), the iron ore is vanadium-titanium iron ore with an iron grade of 40-60%, a titanium content of more than 5%, and a vanadium content of more than 0.4%; the volatile matter of the 20-50mm particle size coal is 10-20%; the mass ratio of 0-50mm particle size iron ore to 20-50mm particle size coal is 100:30-40. In step 2), after the temperature of the mixture reaches 1100~1200℃, 5~30mm particle size coal is screened and injected into the high-temperature section from the discharge end of the rotary kiln, controlling the reaction time to 30~60min; the volatile matter of the 5~30mm particle size coal is above 40%, and the amount of 5~30mm particle size coal thrown in accounts for 40~50% of the amount of 0~50mm iron ore fed into the kiln at the same time; In step 4), the amount of non-magnetic material added is 40% to 50% of the amount of 20-50mm particle size coal fed into the kiln at the same time; after replacing the equivalent amount of 20-50mm particle size coal, the total volatile matter of the mixture of non-magnetic material and 20-50mm particle size coal should be 10-20%. In step 6), the moisture content after drying is controlled to be below 3%, and the strength is controlled to be above 600N / piece.

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