Processing and utilizing method of vanadium-titanium magnetite concentrate

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a processing and utilizing method of vanadium-titanium magnetite concentrate. The method comprises the steps that vanadium-titanium-iron concentrate and slaked lime are mixed, wet-ground and then pelletized, green pellets are obtained, the green pellets are subjected to drying, first-stage preheating treatment and second-stage preheating treatment and then roasted, calcified roasted pellets are obtained, vanadium is extracted through acid leaching, the pellets obtained after acid leaching are subjected to secondary roasting, and pellet ore is obtained; the slaked lime is added according to 1.5-5.5 wt% of the vanadium-titanium-iron concentrate; the pellets subjected to acid leaching are dried and dehydrated at the temperature of 300-400 DEG C in the secondary roasting process, the temperature of first-stage preheating treatment is 800-950 DEG C, the temperature of second-stage preheating treatment is 950-1050 DEG C, the roasting temperature is 1150-1250 DEG C, the compressive strength of the prepared pellets is larger than 2200 N / pellet, and the requirement for the compressive strength of the pellets for a blast furnace is met. The process is simple and controllable, and a new method is provided for efficient utilization of the vanadium titano-magnetite.

Description

Technical Field

[0001] The present invention belongs to the field of metallurgical technology, and particularly relates to a method for processing and utilization of vanadium-titanium magnetite concentrate. Background Art

[0002] Vanadium-titanium magnetite is an important strategic mineral resource, rich in various valuable metal elements such as iron, vanadium, and titanium, and has extremely high comprehensive utilization value. The reserves of vanadium-titanium magnetite in China rank third in the world, among which the reserves in Panzhihua area of Sichuan are 10 billion tons and the reserves in Chengde area of Hebei are 8 billion tons. At present, the blast furnace-converter process is mainly used to smelt vanadium-titanium magnetite and recover iron and vanadium resources therein. The main problem of this process flow is that a large amount of vanadium is lost during the blast furnace reduction-converter vanadium blowing process of vanadium-titanium magnetite pellets. According to statistics, about 40% of vanadium is lost during the blast furnace reduction-converter vanadium blowing process, and the overall recovery rate of vanadium in vanadium-titanium magnetite in Panxi area is currently less than 50%.

[0003] To improve the recovery rate of vanadium in vanadium-titanium magnetite, a direct vanadium extraction process for vanadium-titanium iron concentrate has been developed, that is, the sodium roasting-water leaching-ammonium salt vanadium precipitation process. A certain amount of sodium salt is added to the vanadium-titanium iron concentrate and pelletized, and after oxidation roasting, vanadium is converted into water-soluble sodium vanadate. After water leaching-ammonium salt vanadium precipitation, the vanadium recovery rate can reach 80%. However, in order to improve the vanadium conversion rate during the sodium roasting process, an excessive amount of sodium salt needs to be added, resulting in a large amount of sodium salt remaining in the pellets after water leaching, and it is difficult to economically recover iron and titanium resources therein. On this basis, a calcium roasting-acid leaching vanadium extraction-ammonium salt vanadium precipitation process for vanadium-titanium iron concentrate has been developed, using calcium salt to replace sodium salt, which is beneficial to the recovery and utilization of iron and titanium resources in the pellets after vanadium extraction.

[0004] Patent application CN 110317958A discloses "a method for preparing basic oxidized pellets for ironmaking and extracting vanadium from vanadium-iron materials", which includes steps such as mixing and pelletizing, pellet preparation, vanadium leaching, recovery of vanadium solution and pellet cleaning, pellet dehydration and drying, etc. This application uses bentonite or activated calcium-based bentonite as the binder, and additives are CaO, CaCO 3 、Ca(OH) 2 、CaSO 4 、CaCl 2 、Ca(NO 3 ) 2 、MgO、MgCO 3 、Mg(OH) 2 、MgSO 4 、MgCl 2 、Mg(NO 3 ) 2One or more of them. After the pellets are dried, they are directly heated to 1100-1300 °C for roasting. After acid leaching, the strength of the dehydrated and dried pellets is about 2200 N / piece. In this application, binder bentonite and calcifying agent (CaO) are added at the same time. During the roasting stage of the pellets, SiO in the bentonite 2 reacts with the calcifying agent to form acid-soluble CaSiO 3 , consuming part of the calcifying agent, and CaSiO 3 reacts with H + in the acid leaching solution to form H 2 SiO 3 which dissolves in the vanadium mother liquor. As the acid leaching process progresses, the content of H 2 SiO 3 in the vanadium mother liquor continuously increases, and finally forms silica gel, which affects the subsequent vanadium extraction from the vanadium mother liquor. At the same time, directly roasting the dried pellets at 1100-1300 °C is not conducive to the full oxidation of vanadium, resulting in a vanadium leaching rate of only 66.14% in the examples. After leaching, the strength of the dehydrated and dried pellets is still lower than 2500 N / piece, which does not meet the requirements of large blast furnaces for the compressive strength of pellets, and does not consider whether other physical and metallurgical properties of the leached pellets meet the blast furnace standards.

[0005] Patent CN 202011333297.5 discloses "a method for countercurrent circulating acid leaching of vanadium-titanium magnetite basic oxidized pellets". In order to increase the concentration of vanadium in the mother liquor and reduce the influence of silica gel on vanadium leaching, this patent adjusts and controls the acid concentration of the leaching solution, and adopts the method of countercurrent leaching of secondary (multi-stage) leaching solution circulation to achieve the purpose of increasing the concentration of vanadium in the mother liquor. Specifically, the method of periodically discharging the leaching solution for desilication treatment is adopted to prevent the influence of silica gel on the vanadium leaching of the pellets. However, in the process of preparing calcined roasted pellets, this patent still uses bentonite as the pellet binder, and does not fundamentally solve the formation of silica gel during the vanadium leaching process. The external discharge of the mother liquor for desilication will reduce the vanadium leaching rate, and the vanadium leaching rate in the examples is only 61.7%.

[0006] Patent CN.201710217661.3 discloses "a method for extracting vanadium by calcification oxidation-leaching of low-grade chromium-containing vanadium-titanium magnetite". In order to increase the vanadium leaching rate during acid leaching, the pellets obtained by calcination roasting of vanadium-titanium magnetite are ground into pellet powder smaller than 200 mesh and leached in a sulfuric acid system. The vanadium leaching rate in the examples can reach 81.42%. However, in the process of preparing pellets, this patent also uses 2% bentonite as the binder, which does not solve the problem of silica gel formation during leaching, and continuously heating the pellets in a muffle furnace to 1150-1250 °C is not conducive to the full oxidation of vanadium. In addition, the powdered ore after sulfuric acid leaching needs to be prepared into qualified roasted pellets by a pellet process before entering the blast furnace ironmaking process, which increases the subsequent recovery cost of iron and titanium resources.

[0007] In summary, for the process of calcination roasting - acid leaching vanadium from vanadium - titanium iron concentrate, the following problems still exist: 1) The use of bentonite in the preparation process of vanadium - titanium iron concentrate green balls increases the dosage of calcifying agent and causes the formation of silica gel due to silicon dissolution during acid leaching, which is not conducive to improving the vanadium leaching rate; 2) Insufficient vanadium oxidation occurs during the calcination roasting process of vanadium - titanium magnetite pellets, resulting in a low vanadium leaching rate; 3) It is difficult for the pellets after acid leaching to meet the smelting standards of blast - furnace pellets, causing difficulties in the recycling of iron and titanium resources. To solve the above problems, the present invention proposes a processing and utilization method for vanadium - titanium magnetite concentrate. Summary of the Invention

[0008] The present invention provides a method for successfully preparing vanadium - titanium iron concentrate green balls with qualified green - ball properties by using vanadium - titanium iron concentrate without adding bentonite or organic binder and only adding hydrated lime as a calcifying agent under the condition of wet grinding pretreatment; under an optimized thermal regime, preparing vanadium - titanium iron concentrate calcination - roasting pellets with sufficient vanadium oxidation and a high vanadium leaching rate; using dilute acid leaching to obtain a vanadium - containing leaching solution and vanadium - extraction pellets; after acid leaching and vanadium extraction, the pellets are subjected to secondary roasting, and the physical and metallurgical properties of the pellets both reach the first - grade standard of blast - furnace pellets. The present invention avoids the use of bentonite in the preparation process of green balls, and at the same time optimizes the thermal regime during the calcination roasting process to strengthen the oxidation of vanadium oxides and improve the vanadium leaching rate. The calcination - roasting pellets have qualified compressive strength after acid leaching and secondary roasting, and maintain a well - developed porosity, with excellent physical and metallurgical properties, meeting the requirements of blast - furnace smelting for pellets. To achieve the above object, the present invention includes the following steps:

[0009] Mix and wet - grind the dried vanadium - titanium iron concentrate with hydrated lime, then pelletize to obtain green balls. The green balls are dried, subjected to a first - stage pre - heating treatment, a second - stage pre - heating treatment, and then calcination roasting to obtain calcination - roasting pellets. Then, acid leaching is carried out, followed by solid - liquid separation. After the solid is dried, it is subjected to secondary roasting to obtain secondary - roasting pellets; the hydrated lime is added in an amount of 1.5 - 5.5 wt% based on the vanadium - titanium iron concentrate; the binary basicity R of the calcination - roasting pellets 2 is 0.6 - 1.5;

[0010] The temperature of the first - stage pre - heating treatment is 800 - 950 °C, the temperature of the second - stage pre - heating treatment is 950 - 1050 °C, the temperature of the calcination roasting is 1150 - 1250 °C; the temperature of the secondary roasting is 1150 - 1250 °C.

[0011] For the processing and utilization method of vanadium - titanium magnetite concentrate of the present invention, the vanadium - titanium magnetite concentrate used, by mass percentage, contains TFe 50 - 60%, TiO 2 8 - 15%, V 2 O 5 0.5 - 1.50%.

[0012] To make the vanadium-titanium magnetite concentrate have better pelletizing characteristics and improve the vanadium leaching rate in the subsequent acid leaching process, the vanadium-titanium magnetite concentrate is pretreated by high-pressure roller grinding to increase its specific surface area, improve its surface activity, and improve its pelletizing characteristics. After the vanadium-titanium magnetite concentrate is pretreated by high-pressure roller grinding, the proportion of particles with a size of -0.074 mm is not less than 90%.

[0013] The function of slaked lime in the present invention is as a binder for pelletizing and a calcifying agent for calcination roasting. Therefore, the addition amount of slaked lime should meet both the need for pelletizing of the vanadium-titanium magnetite concentrate and the calcification need of vanadium in the vanadium-titanium magnetite concentrate. The dried vanadium-titanium magnetite concentrate and slaked lime are added by weight at 1.5 - 5.5 wt% of the vanadium-titanium magnetite concentrate (preferably, 1.5 - 3.5 parts of dry slaked lime are added to 100 parts of the vanadium-titanium magnetite concentrate), and are fully mixed in a mixer. In the present invention, no other commonly used binders such as bentonite need to be added during the raw material mixing process.

[0014] Pelletizing is an important link in the pellet process. The quality of the green pellets directly affects the normal progress of the pellet preheating roasting process and the quality of the finished pellets. Many factors affecting pelletizing should be fully considered, such as the feeding amount and the water addition method. 0.5 - 1.0 wt% of supplementary water is added during the pelletizing process to make the moisture content of the mixed material the optimal value for pelletizing. The moisture content of the green pellets is 7 - 10 wt%, and the water addition method is spray type. The pelletizer is a disk pelletizer. Finally, through a green pellet roller screen, the unqualified green pellets with a size of -9 mm and +16 mm are broken and returned to the mixer. The qualified green pellets with a size of 9 - 16 mm should meet the requirements of a drop strength of ≥ 3 times / each, a compressive strength of ≥ 20 N / each, and a bursting temperature of ≥ 600 °C.

[0015] In the present invention, the 9 - 16 mm green pellets are dried at a temperature of 300 - 400 °C for 5 - 10 min to remove free water. The dried pellets are preheated at 800 - 950 °C for 5 - 15 min to remove the remaining crystal water of the green pellets and decompose Ca(OH) 2 into CaO. As the temperature rises, the spinel structure of the titanomagnetite in the vanadium-titanium magnetite concentrate is destroyed, and part of the FeO and V 2 O 3 begin to oxidize to Fe 2 O 3 and V 2 O 5 . The pellets after the first-stage preheating are further oxidized at 950 - 1050 °C for 10 - 20 min. Due to the increase in the second-stage preheating temperature and the extension of the preheating time, the unoxidized V 2 O 3 and FeO are rapidly oxidized, and the oxidation of vanadium and iron oxides is more complete. After the preheating ends, the Fe 2+<0.5%. The preheated pellets are further heated to 1150 - 1250 °C in a rotary kiln or a belt machine for pellet oxidation roasting, and the roasting time is 10 - 15 min. After roasting, the average compressive strength of the roasted pellets is greater than 1800 N / piece, and the vanadium oxide is fully oxidized and the pellet porosity is relatively high, which is beneficial to subsequent acid leaching for vanadium extraction. The high-temperature pellets are cooled to a temperature below <150 °C and discharged.

[0016] In the present invention, the dilute acid solution for acid leaching is a mixture of one or more of sulfuric acid, nitric acid or hydrochloric acid solutions, and the concentration of [H + is 0.1 - 4 mol / L. The higher the concentration of [H + , the higher the V leaching rate. At the same time, more Fe is leached and lost in the mother liquor. The dilute acid solution for acid leaching contains ions such as V, Fe, Al, and Mg. The concentration of V ions is 3 - 6 g / l, and the concentrations of the other ions change with the change of the V ion concentration. The vanadium leaching method is heap leaching, column leaching or soaking, and heap leaching is preferred. The dilute acid solution for acid leaching with different V ion concentrations is used for staged leaching, preferably 3 - 5 stages. The leaching temperature is room temperature. The higher the leaching temperature, the faster the vanadium leaching kinetics and the higher the leaching rate. Under the condition of comprehensive utilization of waste heat, heating leaching is preferably adopted. The liquid-solid ratio affects the vanadium leaching kinetics and leaching rate. The higher the liquid-solid ratio, the faster the vanadium leaching kinetics and the higher the leaching rate, but the lower the concentration of vanadium in the vanadium mother liquor. The preferred liquid-solid ratio is 0.3 - 2. The leaching time is 5 to 30 days.

[0017] In the present invention, the calcined pellets have developed pores after acid leaching, resulting in the compressive strength of the pellets after leaching being only 500 N / piece. After acid leaching for vanadium extraction, the pellets are dried and dehydrated at 300 - 400 °C (the dehydration time can be 8 - 15 min, preferably 10 min) during the secondary roasting process, and then secondary roasting is carried out. The roasting temperature is 1150 - 1250 °C, preferably 1200 - 1250 °C, and the roasting time is 20 - 30 min. After the leached pellets are subjected to secondary roasting, they still maintain a developed porosity, and the compressive strength of the pellets reaches 2200 N / piece, meeting the strength requirements of pellets for blast furnaces.

[0018] The main mechanism involved in this patent is as follows:

[0019] SiO in the vanadium-titanium magnetite concentrate pellets and bentonite 2 will react with CaO at high temperature as follows:

[0020] SiO 2 +CaO = CaSiO 3

[0021] When acid leaching vanadium from vanadium-titanium magnetite concentrate pellets, CaSiO formed at high temperature 3 will react in an acidic solution as follows:

[0022] CaSiO3 +H 2 SO 4 =CaSO 4 (s)+H 2 SiO 3 (l)

[0023] CaSO 4 fills the pores of the leached pellets, while H 2 SiO 3 enters the vanadium mother liquor. As the sulfuric acid leaching time prolongs, the concentration of H 2 SiO 3 in the acid leaching mother liquor continuously increases. When the concentration of H 2 SiO 3 exceeds a certain concentration, silica gel will be formed. The silica gel fills the pores of the pellets, hindering the internal diffusion of the acid solution and the external diffusion of the leaching products. For example, in Patent CN 202011333297.5, the vanadium mother liquor needs to be discharged for desilication treatment before silica gel is formed. However, in the present invention, the addition of bentonite is avoided during the pellet preparation process, and silica gel will not be formed during the acid leaching process, which is beneficial to improving the vanadium leaching rate and significantly reducing the SiO 2 content in the pellets, which is beneficial to improving the iron grade of the pellet ore.

[0024] The present invention uses slaked lime as the calcifying agent and pellet binder. Slaked lime is made by fully mixing small pieces of quicklime (CaO) with a size of 10 - 20 mm with water or steam in a closed stirring tank to undergo a digestion reaction, and then making dry slaked lime after classification. The digestion process of slaked lime is that the digestion water first contacts the outer surface of the quicklime to undergo a chemical reaction to form calcium hydroxide, which covers the surface of the unreacted quicklime core. When the digestion water is in excess, the digestion water passes through the capillary channels of calcium hydroxide and then continues to contact the quicklime core to form a second layer of calcium hydroxide. As the stirring progresses, calcium hydroxide falls off from the surface of the quicklime. The chemical formula of the reaction product obtained repeatedly is CaO x (OH) (2-2x) , where X = 0.05 - 0.17. CaO x (OH) (2-2x) can be considered as an intermediate compound in which CaO has not been completely converted into Ca(OH) 2 . It will adsorb moisture in the air like quicklime. However, it is a stable compound when not in contact with moisture. The reaction product CaO x (OH) (2-2x) is formed under the condition of lack of digestion agent water, resulting in the product CaO x (OH) (2-2x) having good fluidity, dispersibility and high specific surface area, and adhering Figure 2It is the thermogravimetric analysis (TG-DSC) diagram of dry-process slaked lime. Due to the high specific surface area and reactivity with water of dry-process slaked lime, during the pelletizing process of vanadium-titanium iron concentrate, dry-process slaked lime undergoes a chemical reaction with the surface water of vanadium-titanium iron concentrate (CaO x (OH) (2-2x) +xH 2 O (surface water) → Ca(OH) 2 ), thus generating a chemical bond between the surface water of vanadium-titanium iron concentrate and dry-process slaked lime, which is beneficial to strengthening the green pellet properties and further avoiding the use of bentonite during the pelletizing process. It significantly reduces the SiO 2 content in the calcined pellet, so no silica gel is formed during the acid leaching process, which is beneficial to improving the vanadium leaching rate and increasing the iron grade of the pellet ore.

[0025] The present invention adopts a two-stage preheating method. During the first-stage preheating, the spinel structure of titanomagnetite is destroyed to fully expose the vanadium oxide. During the second-stage preheating, the preheating temperature is increased and the preheating time is extended to fully oxidize the iron oxide and vanadium oxide, significantly reducing the Fe 2+ content in the pellet and significantly increasing the V 5+ content in the pellet, which is beneficial to subsequent acid leaching for vanadium extraction. At the same time, the roasting temperature during the roasting process is appropriately reduced, so that the pellet has a certain strength and maintains a relatively high porosity, thereby strengthening the acid leaching kinetics and indirectly increasing the vanadium leaching rate.

[0026] After the calcined pellet is leached with acid for vanadium extraction, the compressive strength of the pellet is reduced to 500 N / piece. By adopting the method of secondary roasting and controlling the roasting temperature and roasting time, the connection of microcrystals of titanohematite and the connection of slag phase inside the roasted pellet can be strengthened, significantly improving the strength of the secondary roasted pellet, and the secondary roasted pellet still maintains a relatively high porosity. During the reduction in the solid burden area of the blast furnace, the reduction of the pellet mainly occurs through indirect reduction (reduction by CO gas). The CO gas enters the inside of the pellet through the pores of the pellet. The roasted pellet has a relatively high porosity, which is beneficial to strengthening the external diffusion of the reducing agent and the internal diffusion of the reduction product, strengthening the reduction kinetics of the roasted pellet, and thus significantly increasing the reduction degree of the secondary roasted pellet in the solid burden area of the blast furnace. At the same time, the relatively high porosity is also the main reason for the low reduction swelling rate after the pellet is reduced by CO. After the leached pellet is subjected to secondary roasting, its physical properties and metallurgical properties both meet the first-class product standards of the blast furnace. Description of the Drawings

[0027] Figure 1 It is the particle size curve of the slaked lime used in the examples and comparative examples of the present invention;

[0028] Figure 2 It is the thermogravimetric analysis (TG-DSC) diagram of the slaked lime used in the examples and comparative examples of the present invention;

[0029] Figure 3 SEM diagram of the pellet after secondary roasting in Example 2. Detailed implementation manners

[0030] The present invention will be further described below with specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but do not limit the present invention.

[0031] The typical chemical components of the vanadium-titanium iron concentrate used in the embodiments and comparative examples of the present invention are shown in Table 1, the typical chemical components of the slaked lime are shown in Table 2, and the particle size distribution of the dry slaked lime is as Figure 1 .

[0032] Table 1. Typical chemical components of vanadium-titanium iron concentrate

[0033] Component TFe FeO CaO <![CDATA[Al 2 O 3 > <![CDATA[SiO 2 > MgO <![CDATA[TiO 2 > Wt% 57.32 30.37 0.47 2.34 1.46 2.23 10.54 Component <![CDATA[V 2 O 5 > <![CDATA[Cr 2 O 3 > MnO P S Loss on ignition Wt% 0.58 1.13 0.20 0.001 0.48 -2.41

[0034] Table 2. Typical chemical components of slaked lime

[0035] Composition CaO <![CDATA[Ca(OH) 2 > Wt% 74.90 98.97

[0036] Comparative Example 1

[0037] In this comparative example, the calcined basic oxidation pellets of the patent (CN 202011333297.5) are prepared from the Panxi vanadium-titanium iron concentrate. The pellet production conditions are as follows: the addition amount of the binder bentonite is 1.2%, the addition amount of the calcifying agent Ca(OH) 2 is 1.8%, the drying temperature is 400 °C, the time is 10 min, the preheating temperature is 900 °C, the time is 10 min, the roasting temperature is 1220 °C, and the time is 30 min. The chemical component analysis is shown in Table 1-1.

[0038] Table 1-1 Chemical component analysis of the calcined basic oxidation pellets in Example 1

[0039] Composition MgO <![CDATA[Al 2 O 3 > <![CDATA[SiO 2 > <![CDATA[P 2 O 5 > CaO Content 2.79 2.78 3.54 0.036 2.2 Composition <![CDATA[TiO 2 > <![CDATA[V 2 O 5 > <![CDATA[Cr 2 O 3 > <![CDATA[SO 3 > TFe Content 9.31 0.58 0.64 0.001 54.65

[0040] Take 180 kg of the pellets in Table 2-1 and place them in a leaching column with a diameter of 300 mm and a height of 1400 mm. Add 30 L of a sulfuric acid solution with a concentration of 0.5 mol for the first-stage leaching. After spraying and leaching for 12 h, add 300 ml of 18.4 mol concentrated sulfuric acid to the leaching solution for acid supplementation. Acid supplementation is carried out twice a day, each time 300 ml. The acid supplementation system and the elemental analysis results of the first-stage mother liquor are listed in Table 1-2. When the leaching reaches the 3rd day, the first-stage leaching mother liquor is discharged for desilication treatment.

[0041] Table 1-2 Acid supplementation system for the first-stage leaching and elemental analysis results of the first-stage mother liquor in Example 1

[0042] Leaching time (h) 0 24 48 72 V (g / l) / 1.51 2.75 3.39 Si (g / l) / 3.15 5.34 7.12 Fe (g / l) / 5.08 7.91 9.07

[0043] For the secondary leaching, 35 L of sulfuric acid solution with a concentration of 0.6 mol was re-prepared for secondary leaching. After spray leaching for 12 h, 18.4 mol concentrated sulfuric acid was used to adjust the acidity of the leaching solution to ensure that the acid [H + in the leaching solution was about 1.2 mol. It was adjusted twice a day. The elemental analysis results of the secondary mother liquor are listed in Table 1-3.

[0044] Table 1-3 Elemental Analysis Results of the Secondary Mother Liquor in Example 1

[0045]

[0046]

[0047] For the tertiary leaching, 35 L of sulfuric acid solution with a concentration of 0.75 mol was re-prepared for tertiary leaching. After spray leaching for 12 h, 18.4 mol concentrated sulfuric acid was used to adjust the acidity of the leaching solution to ensure that the acid [H + in the leaching solution was about 1.5 mol. It was adjusted twice a day. The elemental analysis results of the tertiary mother liquor are listed in Table 1-4.

[0048] Table 1-4 Elemental Analysis Results of the Tertiary Mother Liquor in Example 1

[0049] Leaching time (d) 0 2 4 6 8 10 12 14 V (g / l) / 0.45 0.85 1.12 1.42 1.68 1.75 1.85 Si (g / l) / 0.08 0.08 0.09 0.09 0.09 0.09 0.1 Fe (g / l) / 1.21 2.13 2.89 3.46 4.21 4.98 5.68

[0050] 20 L of water was added for the primary washing, and it was drained after spray leaching for 72 h. The pellets were dried at 140 °C, and the component analysis of the washing solution is listed in Table 1-5. When the total leaching time was 39 days, the leaching rates of vanadium, silicon, and iron were 61.7%, 6.26%, and 0.94% respectively. The results showed that after adding bentonite, the mother liquor desilication process must be carried out during the sulfuric acid leaching process, which not only increased the treatment cost but also reduced the vanadium leaching rate.

[0051] Table 1-5 Elemental Analysis Results of the Primary Washing Solution in Example 1

[0052]

[0053]

[0054] Example 2

[0055] Mix the vanadium-titanium iron concentrate with 1.5% slaked lime and wet-grind for 3 min. Pelletize in a disk pelletizer. The diameter of the pellets is 12 ± 2 mm, the water content is 7.35%. After drying at 400 °C for 15 min, use the grate-kiln process to prepare calcined pellets with a preheating temperature of 800 °C for the first stage and a preheating time of 6 min; a preheating temperature of 1050 °C for the second stage and a preheating time of 10 min; a roasting temperature of 1170 °C and a roasting time of 20 min. The compressive strength of the roasted pellets is 1954.5 N / pellet, and the Fe 2+ content in the pellets is 0.38%. Place 500 g of pellets in a 1000 ml graduated cylinder and leach vanadium by soaking at room temperature. The liquid-solid ratio is 2, and the acid concentration of the leaching solution [H + is 2.0 M respectively. Make up the addition every day according to the acid consumption of the leaching solution. After 27 days of soaking and 1 day of washing, the vanadium leaching rate is 79.56%. The chemical composition of the pellets before and after leaching is shown in Table 2-1. After sulfuric acid leaching, the compressive strength of the leached pellets decreases to 507.8 N / pellet. After acid leaching, the pellets are dried at 300 °C for 10 min and roasted at 1250 °C for 20 min. The average compressive strength of the secondary roasted pellets reaches 2362.8 N / pellet, meeting the compressive strength requirements of pellets for blast furnaces.

[0056] Table 2-1 Analysis of Pellet Composition before and after Leaching (2.0 M)

[0057] Pellet TFe% <![CDATA[SiO 2 %]]> <![CDATA[Al 2 O 3 %]]> CaO% MgO% <![CDATA[TiO 2 %]]> <![CDATA[V 2 O 5 %]]> <![CDATA[R 2 > Pellet before leaching 56.12 2.10 2.09 1.54 2.68 11.13 0.64 0.73 Pellet after leaching 57.50 1.54 1.62 1.21 2.53 10.80 0.20 0.79

[0058] In this example, the recovery rate of Fe is 98.42% and the recovery rate of titanium is 99.91%.

[0059] Example 3

[0060] Mix the vanadium-titanium iron concentrate with 2.0% slaked lime and wet-grind for 3 min. Pelletize in a disk pelletizer. The diameter of the pellets is 12 ± 2 mm, the water content is 7.96%. After drying at 400 °C for 15 min, use the grate-kiln process to prepare calcined pellets with a preheating temperature of 900 °C for the first stage and a preheating time of 6 min; a preheating temperature of 1050 °C for the second stage and a preheating time of 15 min; a roasting temperature of 1200 °C and a roasting time of 20 min. The compressive strength of the roasted pellets is 2384.6 N / pellet, the porosity is 20.93%, and the Fe 2+ content in the pellets is 0.23%. Place 500 g of pellets in a 1000 ml graduated cylinder and leach vanadium by soaking at room temperature. The liquid-solid ratio is 2, and the acid concentration of the leaching solution [H +It is 2.0M and is replenished daily according to the acid consumption of the leaching solution. After 27 days of soaking and 1 day of washing, the vanadium leaching rate is 80.46%. The compressive strength of the pellets after leaching is reduced to 589.2 N / piece, and the porosity of the leached pellets is 25.78%. The pellets after acid leaching are dried at 300 °C for 10 min and roasted at 1230 °C for 20 min. The average compressive strength of the secondary roasted pellets is 2370.1 N / piece, and the porosity of the secondary roasted pellets is 24.96%.

[0061] In this example, the recovery rate of Fe is 98.55% and the recovery rate of titanium is 99.95%.

[0062] Example 4

[0063] Mix the vanadium-titanium iron concentrate with 1.8% dry slaked lime and wet-grind for 3 min. Pelletize in a disc pelletizer. The diameter of the pellets is 12 ± 2 mm, the water content is 7.99%. After drying at 400 °C for 15 min, use the grate-kiln process to prepare calcined pellets with a preheating temperature of 800 °C for the first stage and a preheating time of 6 min; a preheating temperature of 1050 °C for the second stage and a preheating time of 15 min; a roasting temperature of 1170 °C and a roasting time of 20 min. The compressive strength of the roasted pellets is 1974.6 N / piece, the porosity is 21.49%, and the Fe content in the pellets 2+ content is 0.28%. Place 500 g of pellets in a 1000 ml graduated cylinder and leach vanadium by soaking at room temperature. The liquid-solid ratio is 2, and the acid concentration [H + of the leaching solution is 2.0M respectively, and it is replenished daily according to the acid consumption of the leaching solution. After 27 days of soaking and 1 day of washing, the vanadium leaching rate is 80.89%. The compressive strength of the pellets after leaching is reduced to 545.3 N / piece, and the porosity of the leached pellets is 26.26%. The pellets after acid leaching are dried at 300 °C for 10 min and roasted at 1200 °C for 20 min. The average compressive strength of the secondary roasted pellets is 2281.7 N / piece, and the porosity of the secondary roasted pellets is 25.26%.

[0064] In this example, the recovery rate of Fe is 98.81% and the recovery rate of titanium is 99.94%.

Claims

1. A method for processing and utilizing vanadium-titanium magnetite concentrate, characterized in that: The following steps are involved: The dried vanadium-titanium iron concentrate is mixed with slaked lime and then balled to obtain green balls. The green balls are dried, subjected to a first-stage preheating treatment, a second-stage preheating treatment, and then calcified and roasted to obtain calcified and roasted pellets. Acid leaching is then performed, followed by solid-liquid separation, and the solid is dried, followed by a second roasting to obtain a second roasted pellet. Slaked lime is added according to 1.5-5.5wt% of the vanadium-titanium iron concentrate. The binary basicity R2 of the calcified and roasted pellets is 0.6-1.

5. The temperature of the first stage preheating treatment is 800-950°C, the temperature of the second stage preheating treatment is 950-1050°C, the temperature of the calcification roasting is 1150-1250°C; the temperature of the secondary roasting is 1150-1250°C.

2. The method for processing and utilizing vanadium-titanium magnetite concentrate according to claim 1, characterized in that: The vanadium-titanium iron concentrate used contains, by mass percentage, 50-60% TFe, 8-15% TiO2, and 0.5-2.0% V2O5.

3. The method for processing and utilizing vanadium-titanium magnetite concentrate according to claim 1, characterized in that: The vanadium-titanium iron concentrate is pre-treated by a high-pressure roller mill. After the pre-treatment by the high-pressure roller mill, the proportion of -0.074 mm particle size is controlled to be no less than 90%.

4. The method for processing and utilizing vanadium-titanium magnetite concentrate according to claim 1, characterized in that: The slaked lime is added in an amount of 1.5-5.5 wt% of the vanadium-titanium-iron concentrate, and then the mixture is pretreated by grinding. The time for the pretreatment of the mixture by grinding is controlled within 3-5 minutes.

5. The method for processing and utilizing vanadium-titanium magnetite concentrate according to claim 1, characterized in that: During the ball making process, 0.5-1.0wt% of supplementary water is added, and the moisture content of the obtained green balls is 7-10wt%. The water is added by spraying. The ball making machine is a disc ball making machine, and finally the green balls are screened out by a green ball roller screening machine, and the unqualified green balls of -9mm and +16mm are crushed and returned to the mixer.

6. The method for processing and utilizing vanadium-titanium magnetite concentrate according to claim 1, characterized in that: The 9-16 mm green pellets are dried at a temperature of 300-400°C for 5-10 minutes to remove free water; the dried pellets are preheated at 800-950°C for 5-15 minutes, the preheated pellets are further oxidized at 950-1050°C for 10-20 minutes, the preheated pellets are further heated to 1150-1250°C in a rotary kiln or a belt mill to oxidatively roast the pellets for 10-15 minutes, and the high-temperature pellets are cooled to <150°C and discharged; the average compressive strength of the roasted pellets prepared under the above system is greater than 1800N / piece.

7. The method for processing and utilizing vanadium-titanium magnetite concentrate according to claim 1, characterized in that: The dilute acid solution for pickling is a mixture of one or more of sulfuric acid, nitric acid or hydrochloric acid solution. + ] The concentration is 0.1~4mol / L, the liquid-to-solid ratio is 0.3~2 during leaching, and the leaching time is 5 to 30 days for vanadium extraction.

8. The method for processing and utilizing vanadium-titanium magnetite concentrate according to claim 1, characterized in that: The calcified calcined pellets are dried and dehydrated at 300-400°C for 10 minutes after acid leaching, and then subjected to secondary calcination; the secondary calcination temperature is 1150-1250°C, preferably 1200-1250°C, and the calcination time is 20-30 minutes; after the secondary calcination, the compressive strength of the pellets reaches 2200N / piece, meeting the strength requirements of pellets for blast furnaces.

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