Method for preparing high-calcium-magnesium type titanium slag into fluidized chlorination raw material

Abstract

The application provides a method for preparing a boiling chlorination raw material from high calcium and magnesium type titanium slag, and relates to the technical field of metallurgy. Specifically, the method comprises the following steps: S1: performing first leaching on the high calcium and magnesium type titanium slag to obtain leaching residue; S2: performing high-temperature modification on the leaching residue and a magnesium agent to obtain magnesium modified residue; wherein the magnesium agent comprises at least one of magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium chloride or magnesium nitrate; and S3: performing second leaching on the magnesium modified residue under a high-pressure state, and then performing water washing to obtain the boiling chlorination raw material. The process method of the application is simple to operate and low in cost, can meet a wide range of raw materials, and can obtain high-quality boiling chlorination material with calcium oxide content ≤0.1 wt.%, sum of calcium oxide and magnesium oxide content ≤1.5 wt.% and particle size meeting the requirements, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and more specifically, to a method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag. Background Technology

[0002] In the titanium industry chain, titanium tetrachloride is an intermediate product for the preparation of sponge titanium and titanium dioxide produced by the chloride process. Due to its unique production process, the requirements for titanium-rich raw materials are extremely stringent, requiring a titanium grade greater than 85 wt.% and low impurity content (CaO < 0.15 wt.%, CaO + MgO < 1.5 wt.%). Using titanium slag as raw material to prepare titanium-rich materials for chlorination can effectively solve the problem of fine particle size, but the purity is difficult to meet.

[0003] Patent CN108358238A discloses a "modifier for producing rutile using titanium-containing blast furnace slag and a method for manufacturing artificial rutile using titanium-containing blast furnace slag." The method involves mixing titanium-containing blast furnace slag with rutile-type titanium dioxide, where the rutile-type titanium dioxide acts as a guide. Oxygen-containing gas is then introduced at a temperature of 1500℃~1700℃ for oxidation, converting low-valence titanium to tetravalent titanium. The mixture is then cooled and crystallized under the action of the aforementioned modifier, resulting in a concentrated rutile phase slag. This slag is then crushed, ground, and screened to obtain artificial rutile. However, this method still requires heating to maintain the furnace temperature during the oxygen introduction process, resulting in high energy consumption and making it unsuitable for industrial production.

[0004] Patent CN107758729B discloses a "high-calcium-magnesium-titanium slag modification process", which involves adding a certain amount of fluoride to a fluidized bed chlorination system to prevent the formation of calcium chloride and magnesium chloride, thus ensuring the smooth progress of the chlorination reaction. However, this method has certain operational risks, as the amount of fluoride added is difficult to control, and the content of calcium fluoride and magnesium fluoride in solid slag, furnace slag, and dust collector slag will increase, which will also increase the pressure on solid waste treatment.

[0005] Patent CN109399706A discloses "a method for upgrading UGS slag with high-calcium magnesium titanium slag", which involves alkaline leaching, oxidative roasting, reductive sodium roasting, pressurized acid leaching, and calcination of acid slag to upgrade high-calcium magnesium titanium slag into UGS slag. However, this method requires boiling and reflux in a 12-30 wt.% NaOH solution for 3-6 hours, which is time-consuming and requires high-quality equipment. Furthermore, high-temperature reductive sodium roasting is required in the later stage, which places high demands on equipment for industrial implementation.

[0006] Patent CN107399758A discloses "a method for preparing artificial rutile from high-titanium slag". The method involves crushing, alkali leaching to remove impurities, modification and roasting, acid removal to remove impurities, and calcination of high-titanium slag to prepare rutile products that meet the requirements of the chloride process. However, this method uses microwaves as a heat source, which is difficult to implement industrially. In addition, this method requires the titanium slag grade to be above 85% and the SiO2 content to be below 4%, which has high requirements for raw materials and is not suitable for high-calcium-magnesium titanium slag.

[0007] Patent CN111733331B discloses a "method for preparing upgraded titanium slag from hot slag exiting the furnace." This method involves using a high-pressure concentrated jet oxygen lance to inject molten titanium slag from the furnace, causing it to enter the slag bucket in small particle form. The hot slag is then subjected to oxidation and reduction treatment, transforming the crystal structure of traditional titanium slag by converting the insoluble black titanium stone solid solution into a more soluble ilmenite phase. After leaching with hydrochloric acid, a qualified fluidized bed chlorination feedstock can be prepared. However, this method still requires an oxidation-reduction process after the titanium slag cools, albeit at a lower temperature.

[0008] The patentee disclosed in patent CN113957271A "a method for reducing the calcium oxide content in titanium slag and titanium dioxide", which involves mixing and smelting ferroilite and a reducing agent to obtain molten titanium slag, then water quenching the quenched titanium slag, acid leaching the quenched titanium slag, and separating the solid and liquid to obtain titanium slag with a calcium oxide content ≤0.2wt.%. However, this method does not involve the removal of MgO.

[0009] This patent holder disclosed a method for preparing titanium-rich materials and titanium tetrachloride in patent CN113862494A. The method involves smelting high-calcium-magnesium-titanium concentrate and then crushing the molten titanium slag through water quenching. Rapid cooling alters the phase structure of the titanium slag, transforming the black titanium stone in the slag into the rutile phase, worsening the acid solubility of titanium, and converting impurities such as calcium and aluminum into the acid-soluble Ca3Al2O6. Further impurity removal is achieved through acid leaching, oxidation, and reduction roasting-acid leaching, yielding high-quality titanium-rich materials with CaO ≤ 0.15 wt.% and CaO + MgO ≤ 1.5 wt.%. The drawback of this method is its lengthy process; the water-quenched slag requires acid leaching to remove calcium, oxidation-reduction acid leaching to remove magnesium, and then calcination to obtain the titanium-rich material product.

[0010] In view of the above-mentioned research deficiencies, it is essential to develop a low-cost, short-process method for producing fluidized bed chlorination feedstock using high-calcium, magnesium, and titanium slag.

[0011] In view of this, the present invention is hereby proposed. Summary of the Invention

[0012] The purpose of this invention is to provide a method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag. To achieve the above-mentioned objective, the following technical solution is adopted: A method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag, comprising the following steps: S1: performing a first leaching of the high-calcium-magnesium titanium slag to obtain leaching residue; S2: subjecting the leaching residue and a magnesium agent to high-temperature modification to obtain magnesium-modified residue; wherein the magnesium agent includes at least one of magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium chloride, or magnesium nitrate; S3: performing a second leaching of the magnesium-modified residue under high pressure, followed by water washing to obtain the fluidized bed chlorination feedstock.

[0013] Preferably, in step S1: the high-calcium-magnesium titanium slag is a water-quenched slag, wherein the content of titanium dioxide is ≥70 wt.%, the content of calcium oxide is ≥0.3 wt.%, and the content of magnesium oxide is ≥3.0 wt.%.

[0014] Preferably, the particle size of the high-calcium-magnesium titanium slag is -20 to +160 mesh.

[0015] Preferably, in step S1: the leaching agent for the first leaching includes an aqueous solution of at least one of hydrochloric acid, nitric acid, acetic acid, sulfuric acid, and hydrofluoric acid;

[0016] More preferably, the concentration of acid in the aqueous solution is 10 wt.% to 30 wt.%.

[0017] Preferably, in step S1: during the first leaching, the mass ratio of the leaching agent to the high-calcium-magnesium titanium slag is (1-6):1.

[0018] Preferably, in step S1: the temperature of the first leaching is 20℃~105℃, and the leaching time is 0.5h~4h.

[0019] Preferably, in step S2: the magnesium agent is magnesium oxide and / or magnesium carbonate.

[0020] Preferably, the molar ratio of the magnesium agent added to the titanium in the leaching residue is 0.5 to 3.

[0021] Preferably, in step S2: the oxygen-deficient conditions are carried out in an inert gas atmosphere; or, the high-temperature modification is carried out in a reducing gas atmosphere.

[0022] Preferably, in step S2: the temperature of the high-temperature modification is 750℃~1000℃, and the time of the high-temperature modification is 1h~3h.

[0023] Preferably, in step S3: the leaching agent for the second leaching includes an aqueous solution of at least one of hydrochloric acid, nitric acid, acetic acid, sulfuric acid, and hydrofluoric acid;

[0024] More preferably, the concentration of acid in the aqueous solution is 10 wt.% to 30 wt.%.

[0025] Preferably, in step S3: during the second leaching, the mass ratio of the leaching agent to the magnesium-modified slag is (1-6):1.

[0026] Preferably, in step S3: the temperature of the second leaching is 120℃~170℃, the pressure of the second leaching is 0.2MPa~0.9MPa, and the time of the second leaching is 0.5h~6h.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: The process method of the present invention is simple to operate, and reduces the oxidation, reduction, and alkali roasting processes compared with the traditional method. For the first time, magnesium agent is used to remove impurities from high-calcium and magnesium water-quenched titanium slag after calcium removal. At high temperature, the magnesium agent reacts with MgTi2O5 to generate MgTiO3 compound, which is easily soluble in acid. After pressure acid leaching, a fluidized bed chlorinated feedstock with a calcium oxide content ≤0.1wt.%, a sum of calcium oxide and magnesium oxide content ≤1.5wt.%, and a particle size that meets the requirements can be obtained. This is easy to implement in the workshop and reduces production costs. At the same time, the process method of the present invention effectively broadens the range of applicable raw materials and is suitable for titanium slag containing higher calcium and magnesium impurities, especially for titanium resources in the Panxi region. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0029] A method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag includes the following steps: S1: performing a first leaching of the high-calcium-magnesium titanium slag to obtain leaching residue; S2: subjecting the leaching residue and a magnesium agent to high-temperature modification to obtain magnesium-modified residue; wherein the magnesium agent includes at least one of magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium chloride, or magnesium nitrate; S3: performing a second leaching of the magnesium-modified residue under high pressure, followed by water washing to obtain fluidized bed chlorination feedstock.

[0030] Based on product requirements, it is known that the content of calcium and magnesium impurities in fluidized bed chlorination raw materials (or other titanium-rich materials, synthetic rutile products) is relatively high. This invention proposes, for the first time, to remove impurities from the leaching residue after calcium removal through an unconventional method of introducing a magnesium agent. Under high-temperature, oxygen-deficient conditions, the magnesium agent reacts with MgTi2O5 to generate easily acid-soluble MgTiO3 compounds, effectively improving the acid solubility of the titanium slag. This allows impurity ions to be effectively and fully removed during the subsequent pressurized acid leaching process. Compared to existing patented technologies that use alkaline salts or alkalis (sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, etc.) to destroy the structure of black titanium stone, the existing technologies involve large amounts of alkaline substances. While subsequent acid leaching can effectively remove impurities from the titanium slag, it leads to severe product pulverization and introduces new impurity elements. The magnesium agent of this invention effectively avoids these drawbacks.

[0031] In one preferred embodiment, the high-calcium-magnesium titanium slag is a titanium dioxide-rich slag obtained by smelting high-calcium-magnesium titanium ore at a temperature of 1300℃~1600℃. In another preferred embodiment, the high-calcium-magnesium titanium ore includes iron- and titanium-containing concentrates from the Panxi region. In yet another preferred embodiment, the high-calcium-magnesium titanium ore includes at least one of titanium concentrate, reduced titanium concentrate, vanadium-titanium iron concentrate, and reduced vanadium-titanium iron concentrate.

[0032] In a more preferred embodiment, the high-calcium-magnesium titanium slag undergoes a pretreatment operation before the first leaching; the pretreatment includes: water quenching the high-calcium-magnesium titanium slag to obtain water-quenched slag.

[0033] The water quenching refers to the rapid cooling treatment of molten titanium slag after smelting using high-pressure water as a quenching agent. During water quenching, the temperature of the molten titanium slag drops rapidly and it breaks into irregularly shaped particles with controllable volume. When using this water-quenched slag, by utilizing the easy leaching properties of calcium, a mild atmospheric pressure acid leaching process can reduce the CaO content of the water-quenched slag to below 0.15 wt.%. Specifically, the main phases of the titanium slag are: black titanium stone, base stone, and silica glass, with calcium mainly present in the silica glass and magnesium mainly present in the black titanium stone. The molten titanium slag is cooled and broken by water quenching. The high-temperature molten titanium slag is rapidly cooled by a large amount of high-pressure water quenching liquid. Due to the combined effects of the high-pressure water quenching liquid impact and cooling internal stress, the high-temperature molten titanium slag will break into small particles of water-quenched slag. Simultaneously, rapid cooling causes changes in the phase composition of the water-quenched slag; some of the black titanium stone in the titanium slag transforms into the rutile phase, worsening the acid solubility of titanium, while impurities such as calcium and silicon transform into Ca3Si2O, which has good acid solubility. 10 Calcium impurities can be removed by leaching under normal pressure; however, magnesium mainly exists in the titanium slag main phase of black titanium stone or rutile black titanium stone phase, which has poor acid solubility and cannot be easily removed by acid leaching.

[0034] In a more preferred embodiment, a reducing agent is added during the smelting of the high-calcium-magnesium titanium ore; the reducing agent includes carbonaceous substances, specifically coal or coke; in a further preferred embodiment, the mass ratio of the high-calcium-magnesium titanium ore to the reducing agent is 1:(0.1-0.5).

[0035] In a preferred embodiment, the particle size of the high-calcium-magnesium titanium slag is -20 to +160 mesh. According to conventional understanding in the art, 160 mesh is considered fine and 20 mesh is considered coarse for the high-calcium-magnesium titanium slag; that is, titanium slag that can pass through a 20-mesh sieve but not a 160-mesh sieve meets the particle size requirements of this invention. It should be noted that when the high-calcium-magnesium titanium slag is obtained through water quenching, the slag particle size can be controlled by adjusting the water pressure, thereby improving production efficiency and reducing production costs.

[0036] In a preferred embodiment, the leaching agent for the first leaching in step S1 and the leaching agent for the second leaching in step S3 both have the same selection range, namely, an aqueous solution of at least one of hydrochloric acid, nitric acid, acetic acid, sulfuric acid and hydrofluoric acid; however, the first leaching and the second leaching can each be performed with different leaching agents.

[0037] In a more preferred embodiment, the concentration of acid in the aqueous solution includes, but is not limited to, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, and 30%.

[0038] In a preferred embodiment, in step S1, the mass ratio of the leaching agent to the high-calcium-magnesium titanium slag in the first leaching is, but is not limited to, 1:1, 2:1, 3:1, 4:1, 5:1, or 6:1.

[0039] In a preferred embodiment, in step S1: the temperature of the first leaching is including but not limited to 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, and 105℃; those skilled in the art should select a suitable leaching temperature based on the concentration of the selected leaching agent to ensure that the leaching agent (acid solution) does not suffer a large loss of liquid volume due to boiling; the leaching time includes but is not limited to 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, and 4h.

[0040] In a preferred embodiment, in step S2: the magnesium agent is magnesium oxide, magnesium carbonate, or a combination of the two; in this case, the addition of the magnesium agent will not introduce impurity components.

[0041] In a preferred embodiment, in step S2, the molar ratio of the amount of magnesium agent added to titanium in the leaching residue includes, but is not limited to, 0.5, 1, 1.5, 2, 2.5, and 3.

[0042] In a preferred embodiment, in step S2: the temperature of the high-temperature modification includes, but is not limited to, 750℃, 800℃, 850℃, 900℃, 950℃, and 1000℃, and the time of the high-temperature modification includes, but is not limited to, 1h, 1.5h, 2h, 2.5h, and 3h.

[0043] As an optional implementation, in step S2, the high-temperature modification is carried out in an inert gas atmosphere; while when this implementation is not adopted, the high-temperature modification will be carried out in a reducing gas atmosphere.

[0044] In a preferred embodiment, in step S3: during the second leaching, the mass ratio of the leaching agent to the magnesium-modified slag includes, but is not limited to, 1:1, 2:1, 3:1, 4:1, 5:1, and 6:1.

[0045] In a preferred embodiment, in step S3: the temperature of the second leaching includes, but is not limited to, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, and 170℃; the pressure of the second leaching includes, but is not limited to, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, and 0.9MPa. Those skilled in the art should select a suitable leaching temperature and leaching pressure based on the concentration of the leaching agent to ensure that the leaching agent (acid solution) does not suffer significant liquid volume loss due to boiling; the time of the second leaching includes, but is not limited to, 0.5h, 1h, 1.5h, 2h, 3h, 4h, 5h, and 6h.

[0046] Compared with patent CN108358238A, this invention eliminates the need for oxygen supplementation oxidation of molten titanium slag at high temperatures, and features a simpler process, lower equipment requirements, lower energy consumption, and easier industrialization. Compared with patent CN107758729B, the fluidized bed chlorination feedstock prepared by this invention fully meets the requirements before entering the chlorination furnace, ensuring a high safety factor for continuous production and generating less solid waste during the chlorination process. Compared with patent CN109399706A, this invention eliminates the steps of alkali leaching, oxidative roasting, reductive sodium roasting, and calcination, and eliminates the need for material reflux under high alkali concentrations, resulting in lower equipment requirements, a shorter process, and lower production costs. Compared with patent CN107399758A, this invention does not use microwaves as a heat source, making it more feasible. Furthermore, this invention is applicable to the content properties of Panzhihua titanium ore, has lower raw material requirements, a wider range of applications, and can be smelted using traditional industrial electric furnaces, further reducing equipment requirements. Compared to patent CN111733331B, this invention eliminates the oxidation process; two acid leaching steps are sufficient to remove impurities from the titanium slag, and oxygen injection is unnecessary when the molten titanium slag is tapped from the furnace, increasing production safety. Compared to patent CN113957271A, this invention utilizes a magnesium agent to modify the water-quenched slag during the reduction process, effectively reducing the magnesium oxide content and achieving better impurity removal. Compared to patent CN113862494A, this invention is simpler and has a shorter process. By using magnesium agent modification to replace the oxidation-reduction of titanium slag, the magnesium oxide content is reduced to within acceptable limits, resulting in low-impurity, high-quality titanium-rich material.

[0047] Example 1

[0048] 1. Take high-calcium and magnesium water-quenched slag (TiO2 content 78.11 wt.%, CaO content 0.318 wt.%, MgO content 3.65 wt.%) and leach it under normal pressure to remove calcium. The acid solution is 20 wt.% hydrochloric acid, the liquid-to-solid ratio is 6:1, the acid leaching temperature is 100℃, the acid leaching time is 0.5 h, and the leaching residue is dried at 100℃ for 1 h to obtain the leaching residue.

[0049] 2. The leaching residue and MgO were subjected to high-temperature modification under a reducing atmosphere. The addition amount was 0.5 times the molar ratio of titanium in the leaching residue. The modification temperature was 750℃ and the time was 3h to obtain magnesium-structured modified residue.

[0050] 3. The magnesium-modified slag was subjected to pressure acid leaching using 23 wt.% hydrochloric acid at a liquid-to-solid ratio of 6:1, at a temperature of 155℃, a pressure of 0.55 MPa, and a time of 2 hours. Afterward, it was washed with water and dried to obtain the fluidized bed chlorination feedstock. The feedstock contained 94.637 wt.% TiO2, 0.085 wt.% CaO, and 0.461 wt.% MgO.

[0051] Example 2

[0052] 1. Take high-calcium and magnesium water-quenched slag (TiO2 content 78.65wt.%, CaO content 0.309wt.%, MgO content 3.06wt.%) and leach calcium at normal pressure. The acid solution is 18wt.% hydrochloric acid, the liquid-to-solid ratio is 4:1, the acid leaching temperature is 80℃, the acid leaching time is 1h, and the leaching residue is dried at 90℃ for 2h to obtain the leaching residue.

[0053] 2. The leaching residue and MgCO3 were subjected to high-temperature modification under a reducing atmosphere. The addition amount was 3 times the molar ratio of titanium in the leaching residue. The modification temperature was 1000℃ and the time was 1h to obtain magnesium-structured modified residue.

[0054] 3. The magnesium-modified slag was subjected to pressure acid leaching using 21 wt.% hydrochloric acid at a liquid-to-solid ratio of 4:1, at a temperature of 135℃, a pressure of 0.34 MPa, and a time of 6 hours. Afterward, it was washed with water and dried to obtain the fluidized bed chlorination feedstock. The feedstock contained 95.127 wt.% TiO2, 0.062 wt.% CaO, and 0.350 wt.% MgO.

[0055] Example 3

[0056] 1. Take high-calcium and magnesium water-quenched slag (TiO2 content 78.47wt.%, CaO content 0.51wt.%, MgO content 3.5wt.%) and leach calcium at normal pressure. The acid solution is hydrochloric acid solution with an acid concentration of 10wt.% and a liquid-to-solid ratio of 1:1. The acid leaching temperature is 90℃ and the acid leaching time is 4h. Dry at 85℃ for 3h to obtain leaching residue.

[0057] 2. The leaching residue and MgO were subjected to high-temperature modification under a reducing atmosphere. The addition amount was 1 in molar ratio with titanium in the leaching residue. The modification temperature was 800℃ and the time was 2.5h to obtain magnesium-structured modified residue.

[0058] 3. The magnesium-modified slag was subjected to pressure acid leaching using hydrochloric acid solution with a concentration of 25 wt.%, a liquid-to-solid ratio of 3:1, a temperature of 140℃, a pressure of 0.36 MPa, and a time of 3 hours. Afterwards, it was washed with water and dried to obtain the fluidized bed chlorination feedstock. The feedstock contained 93.29 wt.% TiO2, 0.073 wt.% CaO, and 0.549 wt.% MgO.

[0059] Example 4

[0060] 1. Take high-calcium and magnesium water-quenched slag (TiO2 content 75.16wt.%, CaO content 0.62wt.%, MgO content 5.7wt.%) and leach calcium at normal pressure. The acid solution is hydrochloric acid solution with an acid concentration of 15wt.% and a liquid-to-solid ratio of 5:1. The acid leaching temperature is 95℃ and the acid leaching time is 2h. Dry at 80℃ for 3h to obtain leaching residue.

[0061] 2. The leaching residue and MgCO3 were subjected to high-temperature modification under a reducing atmosphere. The addition amount was 2 times the molar ratio of titanium in the leaching residue. The modification temperature was 900℃ and the time was 2h to obtain magnesium-structured modified residue.

[0062] 3. The magnesium-modified slag was subjected to pressure acid leaching using hydrochloric acid solution with a concentration of 20 wt.%, a liquid-to-solid ratio of 5:1, a temperature of 150℃, a pressure of 0.47 MPa, and a time of 2 hours. Afterwards, it was washed with water and dried to obtain the fluidized bed chlorination feedstock. The feedstock contained 94.2 wt.% TiO2, 0.066 wt.% CaO, and 0.964 wt.% MgO.

[0063] Example 5

[0064] 1. Take high-calcium and magnesium water-quenched slag (TiO2 content 75.32wt.%, CaO content 0.44wt.%, MgO content 5.52wt.%) and leach calcium at normal pressure. The acid solution is hydrochloric acid solution with an acid concentration of 16wt.% and a liquid-to-solid ratio of 2:1. The acid leaching temperature is 85℃ and the acid leaching time is 3h. Dry at 95℃ for 2.5h to obtain leaching residue.

[0065] 2. The leaching residue was modified with MgCO3 at high temperature under a reducing atmosphere. The addition amount was 2.5 times the molar ratio of titanium in the leaching residue. The modification temperature was 950℃ and the time was 1.5h to obtain magnesium structure modified residue.

[0066] 3. The magnesium-modified slag was subjected to pressure acid leaching using hydrochloric acid solution with a concentration of 22%, a liquid-to-solid ratio of 6:1, a temperature of 145℃, a pressure of 0.42 MPa, and a time of 4 hours. After washing with water and drying, the fluidized bed chlorination feedstock was obtained, containing 93.2 wt.% TiO2, 0.059 wt.% CaO, and 0.882 wt.% MgO.

[0067] Example 6

[0068] The process is basically the same as in Example 1, except that in step 2, a mixture of MgO and MgCO3 (mass ratio 1:1) is used to replace MgO in Example 1.

[0069] The content parameters of the boiling chlorinated feedstock obtained in step 3 are: TiO2 content 94.58 wt.%, CaO content 0.08 wt.%, and MgO content 0.91 wt.%.

[0070] Example 7

[0071] It is basically the same as Example 1, except that in step 2, MgSO4 is used instead of MgO in Example 1.

[0072] The content parameters of the boiling chlorinated feedstock obtained in step 3 are: TiO2 content 94.77 wt.%, CaO content 0.078 wt.%, and MgO content 0.95 wt.%.

[0073] Example 8

[0074] It is basically the same as Example 1, except that in step 2, MgCl2 is used instead of MgO in Example 1.

[0075] The content parameters of the boiling chlorinated feedstock obtained in step 3 are: TiO2 content 94.56 wt.%, CaO content 0.091 wt.%, and MgO content 0.98 wt.%.

[0076] Example 9

[0077] It is basically the same as Example 1, except that in step 2, Mg(NO3)2 is used instead of MgO in Example 1.

[0078] The content parameters of the boiling chlorinated feedstock obtained in step 3 are: TiO2 content 94.47 wt.%, CaO content 0.08 wt.%, and MgO content 1.09 wt.%.

[0079] Comparative Example

[0080] 1. Take high-calcium-magnesium water-quenched slag (TiO2 content 75.16wt.%, CaO content 0.62wt.%, MgO content 5.7wt.%, same as in Example 4) and leach calcium at normal pressure. The acid solution is 20wt.% hydrochloric acid, the liquid-to-solid ratio is 4:1, the acid leaching temperature is 95℃, the acid leaching time is 2h, and the leaching residue is dried at 90℃ for 3h to obtain the leaching residue.

[0081] 2. The leaching residue and additives were modified at high temperature under a reducing atmosphere. The types of additives used were MgCO3, Na2CO3, Na2CO3+NaOH (weight ratio 1:1) and no additives. When additives were used, the amount of additives added was 1 to the molar ratio of titanium in the leaching residue. The modification temperature was 950℃ and the modification time was 2h to obtain the structurally modified residue and blank experimental sample.

[0082] 3. The modified slags and blank experimental samples were subjected to pressurized acid leaching. The acid used was hydrochloric acid with a concentration of 20 wt.%, a liquid-to-solid ratio of 4:1, a temperature of 135℃, a pressure of 0.34 MPa, and a time of 4 hours. After washing with water and drying, the fluidized bed chlorination feedstock was obtained. The indicators are shown in Table 1 below.

[0083] Table 1

[0084]

[0085] Comparative data shows that high-calcium-magnesium water-quenched slag can remove calcium oxide by frequent pressure acid leaching, but for magnesium oxide, the leaching removal effect is not good without additives. Adding alkaline substances such as sodium carbonate or sodium hydroxide is not ideal. This is because the magnesium agent reacts with MgTi2O5 to generate MgTiO3 compounds that are easily soluble in acid, which effectively improves the acid solubility of titanium slag, so that impurity ions are effectively removed in the later pressure acid leaching process, and has obvious magnesium removal efficiency.

[0086] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag, characterized in that, Includes the following steps: S1: The high-calcium-magnesium titanium slag is subjected to a first leaching to obtain leaching residue; S2: The leaching residue and magnesium agent are subjected to high-temperature modification under oxygen-deficient conditions to obtain magnesium-modified residue; wherein, the magnesium agent includes at least one of magnesium oxide, magnesium carbonate, magnesium sulfate, magnesium chloride or magnesium nitrate; the molar ratio of the amount of magnesium agent added to titanium in the leaching residue is 0.5~3. S3: The magnesium-modified slag is subjected to a second leaching under high pressure, followed by water washing to obtain a boiling chlorination raw material. The pressure of the second leaching is 0.2 MPa to 0.9 MPa.

2. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S1: the high-calcium-magnesium titanium slag is a water-quenched slag, wherein the content of titanium dioxide is ≥70 wt.%, the content of calcium oxide is ≥0.3 wt.%, and the content of magnesium oxide is ≥3.0 wt.%.

3. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, The particle size of the high-calcium-magnesium titanium slag is -20 to +160 mesh.

4. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S1: the leaching agent for the first leaching includes an aqueous solution of at least one of hydrochloric acid, nitric acid, acetic acid, sulfuric acid, and hydrofluoric acid; The concentration of acid in the aqueous solution is 10 wt.% to 30 wt.%.

5. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S1: In the first leaching, the mass ratio of the leaching agent to the high-calcium-magnesium titanium slag is (1~6):

1.

6. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S1: the temperature of the first leaching is 20℃~105℃, and the leaching time is 0.5h~4h.

7. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S2: the magnesium agent is magnesium oxide and / or magnesium carbonate.

8. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S2: the temperature of the high-temperature modification is 750℃~1000℃, and the time of the high-temperature modification is 1h~3h; The high-temperature modification is carried out in an inert gas atmosphere.

9. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S3: the leaching agent for the second leaching includes an aqueous solution of at least one of hydrochloric acid, nitric acid, acetic acid, sulfuric acid, and hydrofluoric acid; The concentration of acid in the aqueous solution is 10 wt.% to 30 wt.%.

10. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S3: In the second leaching, the mass ratio of the leaching agent to the magnesium-modified slag is (1~6):

1.

11. The method for preparing fluidized bed chlorination feedstock from high-calcium-magnesium titanium slag according to claim 1, characterized in that, In step S3: the temperature of the second leaching is 120℃~170℃, and the time of the second leaching is 0.5h~6h.

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