Method for preparing nano titanium dioxide and rutile titanium dioxide by chlorination leaching of titanium middlings

Abstract

The present invention discloses a method for preparing nano titanium dioxide and rutile titanium dioxide by chlorination leaching of titanium middlings, comprising the following steps: (1) grinding and microwave pre-activating the titanium middlings; (2) chlorination leaching; (3) filtering to obtain a fine filtered leachate; (4) freezing and crystallizing the fine filtered leachate to obtain a clear titanium dioxide solution; and (5) dividing the clear titanium dioxide solution into two parts, one for preparing nano titanium dioxide and the other for preparing rutile titanium dioxide. The present invention realizes the comprehensive utilization of vanadium-titanium magnetite, develops a method for preparing nano titanium dioxide and rutile titanium dioxide by chlorination leaching of titanium middlings with high added value, has low production cost, is capable of recycling hydrochloric acid, and is environmentally friendly. In addition to utilizing titanium middlings as raw materials, the method can also reduce the grade requirements of titanium concentrate as raw materials, thereby enabling mineral processing enterprises to improve TiO2 mineral processing yield, increase titanium resource rate, and avoid environmental pollution caused by increasing titanium yield in mineral processing processes.

Description

Technical Field

[0001] The invention relates to the technical field of nano titanium dioxide and titanium dioxide production, in particular to a method for preparing nano titanium dioxide and rutile titanium dioxide by chlorination leaching of titanium middlings. Background Art

[0002] Titanium dioxide (chemical formula: TiO2) is a polymorphic compound found in nature in three crystalline forms: rutile, anatase, and brookite. Rutile titanium dioxide, in particular, has the highest refractive index among white pigments (anatase is the second highest). Titanium dioxide (primarily composed of titanium dioxide, with a particle size of 200-350nm, treated with organic, inorganic, or composite coatings) is currently the best-performing and most commonly used white pigment and one of the most important inorganic chemical products. Titanium dioxide exhibits semiconductor properties, with its electrical conductivity increasing rapidly with temperature and being highly sensitive to oxygen deficiency. Rutile titanium dioxide has an average dielectric constant of 114 and is chemically and thermally stable. Nano-titanium dioxide (particle size 1-100nm) possesses a range of excellent properties (such as color effects, photocatalytic activity, UV shielding, high thermal conductivity, high magnetism, good transparency, and excellent antibacterial properties). Both are widely used in coatings, plastics, papermaking, electronics, water treatment, catalysis, rubber, inks, chemical fibers, ceramics, and other industrial fields. There are two main methods for preparing nano-titanium dioxide: physical and chemical. Physical methods use photoelectric technology combined with mechanical processes such as ball milling and spraying to refine the material to the nanometer scale, but this method is costly and cannot be scaled up. Chemical methods are further subdivided into gas-phase, liquid-phase, and solid-phase methods. However, all of these methods have high requirements for titanium raw materials, complex processes, and high preparation costs, making them difficult to scale up on an industrial scale.

[0003] The currently mature wet process for producing titanium dioxide is the sulfuric acid process, while hydrochloric acid production is under development. The titanium raw materials primarily consist of acid-soluble titanium slag and titanium concentrate. Sulfuric acid decomposes the titanium mineral to produce a mixed solution of titanyl sulfate and titanium sulfate, while hydrochloric acid decomposes the titanium mineral to produce a titanium oxychloride solution. Other acid-soluble impurities, such as ferrous, calcium, and magnesium salts, are decomposed into soluble sulfates and chlorides. Undecomposed minerals remain in the solution as solid impurities and can be removed by filtration. This solution, known as titanium liquid, undergoes a series of processes, including impurity removal, concentration increase, hydrolysis to produce hydrated titanium dioxide, filtration, washing, calcination, and post-processing, to produce pigment-grade titanium dioxide. Complex processes, including magnetic separation and flotation, yield titanium concentrate, iron concentrate, and tailings, respectively. Approximately 50% of the titanium in the vanadium-titanium magnetite enters the blast furnace along with the iron concentrate after beneficiation. The tailings also contain a large amount of TiO2. In order to make full use of titanium resources, titanium ore further selected from the iron ore tailings is called titanium middlings. Its typical TiO2 grade is about 36%~38%, which is about 10% lower than the grade of titanium concentrate. It has a high impurity content and does not meet the industrial requirements for directly producing sponge titanium, artificial rutile, titanium dioxide and high-titanium slag. Its economic efficiency is not high when used alone in existing industrial production, and it puts great pressure on environmental protection. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: how to provide a method for preparing nano titanium dioxide and rutile titanium dioxide by chloride leaching of titanium middlings, which can utilize titanium middlings to produce nano titanium dioxide and rutile titanium dioxide for pigments, thereby improving the resource utilization rate of titanium in vanadium titanium magnetite, expanding the application field of by-products, and solving the problems of insufficient market supply of titanium concentrate and green and environmentally friendly production.

[0005] The technical solution of the present invention is: a method for preparing nano titanium dioxide and rutile titanium dioxide by chlorination leaching of titanium ore, comprising the following steps:

[0006] (1) Grinding and microwave pre-activating the titanium ore raw material to obtain pre-activated titanium ore fine material;

[0007] (2) adding mother liquor roasting absorption acid into the chlorination leaching kettle, adding the pre-activated titanium ore fine material of step (1) into the chlorination leaching kettle under stirring and introducing hydrogen chloride gas generated by the hydrochloric acid analysis system; utilizing the heat of dissolution of the hydrogen chloride gas to heat and perform acid hydrolysis to obtain a chlorinated slurry; adding iron powder and a deflocculating compound agent in the later stage of the acid hydrolysis to maintain the effective hydrochloric acid concentration in the kettle greater than 265 g / L, and recovering the acid hydrolysis tail gas generated during the acid hydrolysis process by the hydrochloric acid analysis system;

[0008] (3) hot filtering the chlorinated slurry of step (2) to obtain leaching residue and leachate; acid leaching the leaching residue to prepare a porous silicon titanium material, and fine filtering the leachate through the porous silicon titanium material to obtain a fine filtered leachate;

[0009] (4) freezing and crystallizing the fine filtered leachate from step (3), and then filtering by pressure to obtain a ferrous chloride filter cake and a titanium-clear solution; dissolving the ferrous chloride filter cake with hydrochloric acid generated by a hydrochloric acid analysis system, and then spray roasting to obtain ferric oxide, and recovering hydrogen chloride using the hydrochloric acid analysis system;

[0010] (5) The titanium dioxide removal solution in step (4) is divided into two parts, one part is used to prepare nano-titanium dioxide, and the other part is used to prepare rutile titanium dioxide;

[0011] (5.1) The steps for preparing nano-titanium dioxide are:

[0012] a. Concentrating the clear titanium solution to obtain concentrated titanium solution and recovering the condensed acid;

[0013] b. The concentrated titanium solution is hydrolyzed by self-crystal seeding to obtain nano-titanium dioxide precursor and recover the condensed acid;

[0014] c. Filter the nano-titanium dioxide precursor with a membrane and wash it with the hydrochloric acid generated by the hydrochloric acid analysis system or the recovered condensed acid to obtain a clean filter material. The filtered hydrolysis mother liquor and washing liquid are returned to step (3) for fine filtration;

[0015] d. Wash the filter material and neutralize it with dilute ammonia water, then centrifuge and concentrate it and flash dry it to obtain powder;

[0016] e. calcining the powder to obtain nano titanium dioxide and recovering ammonium chloride;

[0017] (5.2) The steps for preparing rutile titanium dioxide are:

[0018] a. Concentrating the clear titanium solution to obtain concentrated titanium solution and recovering the condensed acid;

[0019] b. adding heterogeneous crystal nuclei to concentrated titanium solution and performing hydrolysis under normal pressure to obtain hydrated titanium dioxide and recover condensed acid;

[0020] c. Filtering the hydrated titanium dioxide and washing it with recovered condensed acid to obtain a hydrated titanium dioxide filter cake; spray-roasting the hydrolysis mother liquor and the washing liquid after filtration to obtain iron oxide powder and the mother liquor roasting absorption acid;

[0021] d. The hydrated titanium dioxide filter cake is calcined to obtain rutile titanium dioxide powder.

[0022] Furthermore, in step (1), the particle size of the pre-activated titanium ore fine material is less than 38 μm.

[0023] Furthermore, in step (2), the acid hydrolysis temperature is 90° C., and the acid hydrolysis time is 1.5-2.0 h.

[0024] Furthermore, in step (2), at the end of the acid hydrolysis, the Ti in the acid hydrolysis slurry 3+ 1.5~2g / L.

[0025] Furthermore, in step (5.1) a, the concentration of free hydrochloric acid in the concentrated titanium solution is 25-30 g / L, and the concentration of titanium ions is about 300 g / L calculated as TiO2.

[0026] In the present invention, according to the mineral coating characteristics of the titanium ore raw material, the titanium ore decomposed material used is a fine material that has been pre-activated by mechanochemical method and activated by microwave treatment through vertical mill grinding. The mineral particles undergo crushing, smashing, grinding, bending and other actions in the mechanical activation process, and the dielectric material in the microwave treatment process produces electronic polarization, atomic polarization, dipole steering polarization and interface polarization, resulting in particle refinement and structural changes, such as crystal transformation, recrystallization, amorphization, and the breaking of surface chemical bonds to produce unsaturated groups, free ions and electrons, etc., and thus produce new surfaces, resulting in lattice defects, leading to an increase in the internal energy of the mineral crystal, being in an unstable chemically active state, and making many reactions that cannot occur under normal pressure and room temperature possible. Compared with ordinary titanium ore powder, it has higher surface energy and is easily acidified by chlorination leaching. The particle size of the titanium ore activated for chlorination leaching is controlled to be D max <38μm.

[0027] After chlorination leaching, leaching slurry filtration, leachate filtration, and ferrous chloride crystallization, the resulting clear titanium solution is evaporated and concentrated, and the condensed acid is recovered to produce a concentrated titanium solution that meets the conditions for preparing nano-titanium dioxide by hydrolysis. The concentrated titanium solution has a free acidity of 25-30 g / L and a titanium ion concentration (as TiO2) of approximately 300 g / L. Self-nucleation hydrolysis occurs at a relatively low temperature (≤65°C) and a low titanium ion hydrolysis rate (60%-70%). Under these controlled conditions of low effective acidity, low temperature, and low hydrolysis rate, the nucleation and growth rates of the crystals are both slow, allowing the primary crystal particles to grow to several nanometers in size, avoiding the formation of large micelles and flocculated particles.

[0028] The partially hydrolyzed nano-titanium dioxide precursor-containing hydrolysis slurry is filtered and washed to obtain purified nano-titanium dioxide precursor slurry, unhydrolyzed hydrolysis mother liquor and acid washing liquid. Nanofiltration and washing are achieved using a nanofiltration element with a composite structure of high-precision ceramic membrane-diatomaceous earth, activated carbon-high-precision ceramic membrane. The washing liquid is the acid after hydrochloric acid analysis or the condensed acid produced when the titanium liquid is concentrated. Both are pure acids, which can enhance the washing process and avoid the hydrolysis of impurities such as iron, and clean Fe 2+ 、Fe 3+ Mg 2+ , Ca 2+ and Al 3+ and other impurity ions.

[0029] The washed nano-titanium dioxide precursor slurry is neutralized with dilute ammonia to neutralize adsorbed and entrained HCl to form ammonium chloride. After concentration and flash drying, the powder is then heat-treated in a tunnel kiln at a calcination temperature below 600°C for 1-1.5 hours to complete dehydration and complete conversion to the rutile crystal form. Entrained ammonium chloride sublimes at temperatures above 337.8°C and is recovered as crystals in a cooling cabinet attached to the tunnel kiln flue. (Essentially, it completely decomposes into ammonia and hydrogen chloride gases, which then combine at low temperatures to form snowflake-shaped ammonium chloride crystals.) Because ammonium chloride first decomposes into ammonia and hydrogen chloride gases during the calcination process, they act as a bulking agent to deagglomerate particles. This solves the problem of severe agglomeration and particle growth that can occur during high-temperature dehydration and crystallization of nanopowder materials. Chloride ions are also thoroughly removed, meeting the quality requirements of specialized nano-titanium dioxide products, such as those for electronic ceramics. The nano-titanium dioxide can undergo conventional post-processing depending on the intended application.

[0030] The incompletely hydrolyzed titanium mother liquor and acid wash water from the hydrolysis slurry of the nano-titanium dioxide precursor are filtered through membrane filtration and then incorporated into the leachate produced by the leaching slurry filtration for fine filtration, enabling the recycling of components such as titanium, iron, and chlorine. Fine filtration removes nano-titanium dioxide particles entrained in the hydrolysis mother liquor and acid wash water, preventing direct incorporation into the rutile titanium dioxide production system from affecting the nucleation process and titanium-iron ratio in the hydrolysis process.

[0031] It is used to concentrate the titanium liquid in the production system of rutile titanium dioxide to produce pure condensed acid. The concentrated titanium liquid is hydrolyzed at normal pressure to prepare hydrated titanium dioxide by adding heterogeneous crystal nuclei. The heterogeneous crystal nuclei can reduce the energy of the system and promote the 4+ Hydrolysis is performed on heterogeneous crystal nuclei to increase the production rate of hydrated titanium dioxide particles. The heterogeneous crystal nuclei are amorphous silicon dioxide nano-spherical particles with a particle size of several nanometers, produced by the hydrochloric acid decomposition of mica. The filtered and washed hydrated titanium dioxide filter cake is calcined in a rotary kiln to produce a primary rutile titanium dioxide powder. The hydrolysis mother liquor is spray-roasted and absorbed to produce low-end iron oxide powder and acid hydrolysis. The primary rutile titanium dioxide powder is ground, coated with aluminum and silicon, and then jet milled to produce rutile titanium dioxide powder.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This method achieves comprehensive utilization of vanadium-titanium magnetite and develops a method for producing high-value-added nano-titanium dioxide and rutile titanium dioxide by chlorination leaching of titanium middlings. This method offers low production costs, recycling of hydrochloric acid, and an environmentally friendly production process. In addition to utilizing titanium middlings as raw material, this method also reduces the grade requirements for titanium concentrates. This allows mineral processing companies to increase TiO2 beneficiation yields and titanium resource rates, while avoiding the environmental pollution associated with increasing titanium yields during the mineral processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0035] The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0036] Example 1

[0037] In this embodiment, the titanium ore raw material is Panzhihua titanium ore, with a TiO2 content of 37.51%, a FeO content of 38.57%, a Fe2O3 content of 7.20%, a P content of 0.051%, and a Dmax of ≤74μm (200 mesh). The titanium concentrate powder [2] is pre-activated by vertical milling and microwave activation heat treatment to obtain pre-activated titanium ore fine material with a particle size of D 98 <35.3μm, Dmax<37μm (400 mesh).

[0038] Add 1400L of mother liquor roasting absorption acid (HCl: 320-330g / L) to a sealed 2m³ chlorination leaching reactor and start stirring. Then add 700kg of pre-activated titanium ore fines to the chlorination leaching reactor and stir to mix. The ore-acid ratio (mass to volume) is 1:2.0.

[0039] The hydrochloric acid gas obtained by the hydrochloric acid decomposition system was introduced, and the system was heated to 90°C by the heat of solution of the hydrochloric acid gas. The system temperature was maintained to increase the acidity of the system. [3] The acid decomposition was stirred for 1.5 hours. The acid decomposition tail gas generated during the acid decomposition process was condensed and absorbed by the hydrochloric acid produced by the hydrochloric acid decomposition system.

[0040] Add 13kg iron powder (elemental iron content 95%) to make Fe 3+ Reduction to Fe 2+ , add 320g of deflocculating compound [4] (pre-dissolved), continue stirring for 0.5 hours, and ensure that the Ti content in the acid hydrolysis slurry is less than 1% by the end of the acid hydrolysis. 3+ Reach 1.5~2g / L. Maintain the effective hydrochloric acid concentration of the acid hydrolysis reactor at above 270g / L[5].

[0041] When the slurry temperature drops to 85°C, the material is discharged and pumped to the silicon-titanium liquid supply tank, and then pumped to the acid-hydrolysis slurry diaphragm filter press for hot filtration. The acid-hydrolysis slurry filter cake is transported to the porous silicon-titanium composite material preparation section.

[0042] The acid solution from the acid solution slurry filtration is pumped to the acid solution transfer tank and then pumped to the acid solution diaphragm filter press, and the fine filtrate is pumped to the crystallized titanium liquid intermediate storage tank.

[0043] Open the discharge valve of the intermediate storage tank of the crystalline titanium liquid, pump the refined filtrate into the closed crystalline titanium liquid tank, start stirring, turn on the ice water pump, and use ice water to cool the crystalline titanium liquid from the jacket. Pump the frozen crystalline titanium liquid into the chamber filter press, and stop feeding when the pressure in the filter press reaches 0.3MP. Open the compressed air valve and use compressed air to blow away the residual liquid in the ferrous chloride filter cake. The resulting filtrate is the clear titanium liquid. The test indicators are: TiO2: 201.74g / L, Fe 2+ :42.60 / L,Cl - : 312.30g / L, effective acid concentration: 262.82g / L, free acid concentration: 72.65 g / L, titanium ore acidification rate: 96.02%. The clear titanium solution is purple and has a stability of >500.

[0044] 600L of analytical acid (HCl: 200g / L) after the ferrous chloride filter cake is analyzed with hydrochloric acid is circulated and dissolved in a chamber filter press. The prepared ferrous solution is pumped to the intermediate storage tank of the ferrous chloride solution in the regeneration acid spray roasting process to prepare high-quality ferric oxide powder and regeneration acid.

[0045] The purified titanium dioxide solution used to prepare nano-titanium dioxide was fed into a single-effect vacuum distillation system. The mixture was concentrated by low-temperature boiling under vacuum conditions, reaching a concentration ratio of 70%. The concentrated titanium dioxide solution was pumped to a storage tank, where its indicators were measured (free acid concentration: 27.50 g / L, TiO2: 286.2 g / L, TFe: 59.84 g / L). The vapor and HCl produced by evaporation were condensed into a condenser to produce condensed acid (158.62 g / L) from the titanium dioxide solution.

[0046] In a 1m³ hydrolysis kettle, 700 liters of concentrated titanium solution was added and stirring was started at 30 rpm. Saturated steam was introduced for direct heating until the hydrolysis temperature dropped below 65°C. The hydrolysis was maintained at this temperature and monitored periodically until the generated nano-titanium dioxide precursor (TiO2·2H2O) reached the required hydrolysis rate (60%-70%). Hydrolysis was then terminated. The hydrogen chloride gas and water vapor produced during the hydrolysis process were pumped to a falling film absorption system for tail gas absorption treatment. The resulting clean condensed acid was pumped into the secondary wash acid storage tank.

[0047] Open the discharge valve of the hydrolysis pot, and pump the hydrolyzed hydrated titanium dioxide slurry into the tubular membrane filtration washing system for nanofiltration and washing. The washing liquid uses the acid after hydrochloric acid analysis or the condensed acid produced when the titanium liquid is concentrated. Both are pure acids, which can enhance the washing process and avoid the hydrolysis of impurities such as iron, and wash Fe 2+ 、Fe 3+ Mg 2+ , Ca 2+ and Al 3+ and other impurity ions.

[0048] The washed nano-titanium dioxide precursor slurry is neutralized with dilute ammonia water to a pH of 6-7, so that the adsorbed and entrained HCl is neutralized to ammonium chloride (NHCl). After centrifugal concentration and flash drying, the powder is then calcined in a tunnel kiln at a temperature below 600°C for 1-1.5 hours to complete dehydration and complete conversion to rutile crystal form [6]. The tunnel kiln is a push-plate kiln, and the nano-titanium dioxide precursor is placed in a corundum sagger. The NH3Cl entrained in the powder sublimates at a temperature greater than 337.8°C and is crystallized and recovered in a cooling cabinet attached to the push-plate kiln flue.

[0049] The hydrolysis slurry of the nano-titanium dioxide precursor is filtered through a membrane, and the titanium incomplete hydrolysis mother liquor and the acid washing liquid are pumped into the transfer tank of the acid hydrolysis liquid generated by the leaching slurry filtration, and the mixed liquid is subjected to the leaching liquid fine filtration.

[0050] The clean titanium solution used to produce rutile titanium dioxide is metered and pumped into a single-effect vacuum distillation system. The mixed solution is boiled and concentrated at low temperature under vacuum conditions, with a concentration ratio of 70%. The concentrated titanium solution is pumped into the concentrated titanium solution storage tank, and the concentrated titanium solution test indicators (free acid concentration: 72.50g / L, Ti 3+ The steam and HCl produced by evaporation are condensed into titanium liquid concentrated condensed acid (152.42 g / L) through a condensation device.

[0051] Add 60kg of 300-mesh mica powder and 150kg of 6M hydrochloric acid to 1M 3 The nucleus preparation tank is stirred for leaching and hydrolysis at a temperature of 25-40°C for 2 hours. The white acid-insoluble material (amorphous silica) is filtered to obtain a precipitate. This precipitate (dry basis) is added with an equal mass of sodium hydroxide and stirred with pure water to form a slurry with a solid content of 10%. This slurry serves as a heterogeneous nucleation agent in the hydrolysis step of the rutile titanium powder preparation system.

[0052] Open the discharge valve and liquid pump of the concentrated titanium liquid storage tank, and pump 1400L of concentrated titanium liquid into the 2M 3 In the hydrolysis pot.

[0053] Start the agitator at 30 rpm and introduce saturated steam for direct heating. Heat the concentrated titanium dioxide solution to 90°C. Quickly add 2 L of seed crystal slurry. Use steam to heat the hydrolysis solution until it boils and maintain this temperature for 30 minutes. Continue hydrolysis to produce a solid titanium dioxide product, hydrated titanium dioxide (TiO2·2H2O). Hydrolysis is complete when the hydrolysis rate reaches 99%. Add 100 g of lignocellulose to the hydrolysis pot and stir evenly. The hydrolyzed hydrated titanium dioxide slurry is naturally cooled to 60-70°C. Open the hydrolysis pot discharge valve and pump the hydrated titanium dioxide into the hydrated titanium dioxide storage tank using a transfer pump for subsequent washing. The hydrogen chloride gas and water vapor generated during the hydrolysis process are pumped to a falling film absorption system for off-gas absorption and treatment, generating a small amount of clean condensed acid.

[0054] While the hydrated titanium dioxide slurry storage tank is stirring, open the discharge valve and the diaphragm filter press feed valve. Pump the hydrated titanium dioxide slurry into the diaphragm filter press through the feed pipe. The filtrate, i.e., the hydrolysis mother liquor, is fed into the mother liquor concentration system. The filter cake undergoes primary and secondary washings in the diaphragm filter press. The washing acid is derived from the concentrated condensed acid of the titanium hydrolysis mother liquor and the concentrated condensed acid of the titanium liquid. The HCl content is ≥240g / L and does not contain impurities such as iron. After washing, the material is unloaded and the hydrated titanium dioxide filter cake is sent to the calcination process.

[0055] Open the hydrolysis mother liquor storage tank, pump the hydrolysis mother liquor into the hydrolysis mother liquor concentration reactor, start the steam, heat it to boiling using the jacket indirect heat exchange method, concentrate it according to a concentration ratio of 30%, condense and recover the hydrolysis mother liquor condensed acid, pump it to the secondary wash acid storage tank, and pump the concentrated mother liquor to the concentrated mother liquor storage tank of the spray roasting section.

[0056] The outlet valve of the concentrated mother liquor storage tank was opened, and the concentrated mother liquor was sprayed into the roasting furnace. There, it came into contact with hot air at a temperature of 750-850°C and reacted with O2 and H2O to decompose into a mixed gas of H2O and HCl and solid metal oxides. The absorption acid storage tank was opened, and the washing acid after washing the hydrated titanium dioxide filter cake was used as the absorption liquid for the falling film absorption system in the spray roasting section to produce regenerated acid. The regenerated acid was pumped into the regenerated acid storage tank for chlorination leaching, with a regenerated acid concentration of 350.40g / L.

[0057] The rotary kiln speed is adjusted to 0.3 rpm, and the exhaust fan at the kiln tail is turned on. When the kiln tail temperature reaches approximately 350-400°C, the hydrated titanium dioxide filter cake is fed via a screw conveyor and sent to the kiln tail for calcination. The material resides in the calcination rotary kiln for approximately 7-8 hours. The first temperature zone is 350-750°C, with a residence time of 2.8 hours, during which the hydrated titanium dioxide undergoes the removal of adsorbed water, crystallization water, deacidification, and desulfurization processes. The second temperature zone is 750-880°C, with a residence time of 2.2 hours, completing the rutile crystal transformation of the titanium dioxide. The third temperature zone is 880-930°C, with a residence time of 2.4 hours, completing the titanium dioxide particle growth process. The titanium dioxide powder, calcined at approximately 930°C, is discharged from the calcining rotary kiln head through the kiln's lower hood discharge device and then transferred to an air-cooled rotary kiln for cooling to 60°C. The particle size is 0.2-0.35μm, with a rutile content exceeding 99% and a titanium dioxide content of 99.87%. This is the primary rutile titanium dioxide powder and is conveyed by a belt conveyor to a post-calcination storage bin. The rotary kiln exhaust gas is spray-washed and heat-exchanged in a Venturi concentrator, followed by primary and secondary falling film absorption, and then defogged by an electrostatic demister.

[0058] The primary rutile titanium dioxide can be used directly or processed as needed:

[0059] The deagglomeration and dispersion production process for primary rutile titanium dioxide is as follows: primary titanium dioxide from the calcined storage bin is placed in the roller mill buffer hopper and first ground in the roller mill. It is then sent to the Raymond mill buffer hopper, fed by a feed screw to the Raymond mill for grinding and sorting in the Raymond mill's built-in classifier. Qualified powder is fed by the Raymond mill dust collector's lower discharge screw to the wetting tank feed screw. Deionized water and dispersant are added to the wetting tank for slurrying, and then pumped to the pre-sand mill storage tank. It is then pumped to the first-stage sand mill for sand grinding. After sand grinding, the feed transfer tank is stirred, and then pumped to the second-stage sand mill for sand grinding. The slurry is pumped to the pre-coating tank. The pH of the slurry is adjusted to 4, and the TiO2 content is 300-320g / L.

[0060] The deagglomerated and dispersed rutile titanium dioxide is subjected to continuous silica-alumina coating. The dispersed and deagglomerated titanium dioxide slurry is metered and pumped into a surface treatment tank (coating tank). The slurry is heated to 95°C, and sodium silicate solution (concentration: 400g / L) is continuously added. Dilute sulfuric acid is added once to adjust the pH to 9.3-10, matured, and then adjusted to 6.8-7.2 multiple times. Then, sodium aluminate solution (concentration: 200g / L) is continuously added to adjust the pH to 6.8-7.2. The slurry is matured and cooled to 70°C, and the pH is adjusted to 4.5-5.0. The coated slurry is then pumped to a box-type diaphragm filter press for filtration and washing.

[0061] The qualified filter cake is fed into the flash dryer feed hopper. Inside the dryer, it comes into direct contact with the high-temperature airflow generated by the hot air furnace, rapidly evaporating the moisture and drying the material. The dry powder, carried by the hot airflow, enters a high-temperature bag filter to recover the TiO2 and is then conveyed via a spiral conveyor to the pre-gas hopper. The dried material is then fed into a gas-flow mill, where an organic coating agent is added for the final deagglomeration and dispersion process of the titanium dioxide product.

Claims

1. A method for preparing nano titanium dioxide and rutile titanium dioxide by chlorination leaching of titanium ore, characterized in that: The steps include: (1) Grinding and microwave pre-activating the titanium ore raw material to obtain pre-activated titanium ore fine material; (2) adding mother liquor roasting absorption acid into the chlorination leaching kettle, adding the pre-activated titanium ore fine material of step (1) into the chlorination leaching kettle under stirring and introducing hydrogen chloride gas generated by the hydrochloric acid analysis system; utilizing the heat of dissolution of the hydrogen chloride gas to heat and perform acid hydrolysis to obtain a chlorinated slurry; adding iron powder and a deflocculating compound agent in the later stage of the acid hydrolysis to maintain the effective hydrochloric acid concentration in the kettle greater than 265 g / L, and recovering the acid hydrolysis tail gas generated during the acid hydrolysis process by the hydrochloric acid analysis system; (3) hot filtering the chlorinated slurry of step (2) to obtain leaching residue and leachate; acid leaching the leaching residue to prepare a porous silicon titanium material, and fine filtering the leachate through the porous silicon titanium material to obtain a fine filtered leachate; (4) freezing and crystallizing the fine filtered leachate from step (3), and then filtering by pressure to obtain a ferrous chloride filter cake and a titanium-clear solution; dissolving the ferrous chloride filter cake with hydrochloric acid generated by a hydrochloric acid analysis system, and then spray roasting to obtain ferric oxide, and recovering hydrogen chloride using the hydrochloric acid analysis system; (5) The titanium dioxide removal solution in step (4) is divided into two parts, one part is used to prepare nano-titanium dioxide, and the other part is used to prepare rutile titanium dioxide; (5.1) The steps for preparing nano-titanium dioxide are: a. Concentrating the clear titanium solution to obtain concentrated titanium solution and recovering the condensed acid; b. The concentrated titanium solution is hydrolyzed by self-crystal seeding to obtain nano-titanium dioxide precursor and recover the condensed acid; c. Filter the nano-titanium dioxide precursor with a membrane and wash it with the hydrochloric acid generated by the hydrochloric acid analysis system or the recovered condensed acid to obtain a clean filter material. The filtered hydrolysis mother liquor and washing liquid are returned to step (3) for fine filtration; d. Wash the filter material and neutralize it with dilute ammonia water, then centrifuge and concentrate it and flash dry it to obtain powder; e. calcining the powder to obtain nano titanium dioxide and recovering ammonium chloride; (5.2) The steps for preparing rutile titanium dioxide are: a. Concentrating the clear titanium solution to obtain concentrated titanium solution and recovering the condensed acid; b. adding heterogeneous crystal nuclei to concentrated titanium solution and performing hydrolysis under normal pressure to obtain hydrated titanium dioxide and recover condensed acid; c. Filtering the hydrated titanium dioxide and washing it with recovered condensed acid to obtain a hydrated titanium dioxide filter cake; spray-roasting the hydrolysis mother liquor and the washing liquid after filtration to obtain iron oxide powder and the mother liquor roasting absorption acid; d. The hydrated titanium dioxide filter cake is calcined to obtain rutile titanium dioxide powder.

2. The method according to claim 1, characterized in that In step (1), the particle size of the pre-activated titanium ore fine material is less than 38 μm.

3. The method according to claim 1, characterized in that In step (2), the acid hydrolysis temperature is 90° C. and the acid hydrolysis time is 1.5-2.0 h.

4. The method according to claim 1, wherein In step (2), at the end of acid hydrolysis, the Ti in the chlorinated slurry 3+ The concentration is 1.5~2g / L.

5. The method according to claim 1, wherein In step (5.1) a, the free hydrochloric acid concentration in the concentrated titanium solution is 25-30 g / L, and the titanium ion concentration is 300 g / L calculated as TiO2.

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