Method for preparing titanium liquid by VTM ironmaking slag

Abstract

The application discloses a method for preparing titanium liquid by VTM ironmaking waste slag and hydrolysis pretreatment, and belongs to the technical field of resource utilization of VTM ironmaking waste slag. The method is targeted at the significant difference in the composition of titanium liquid prepared from waste slag (blast furnace slag and gas-based shaft furnace slag) from different sources, and the titanium liquid meeting the requirements of the hydrolysis process is obtained through targeted treatment. Through the combined process of "MVR concentration, crystallization, separation, purification and drying", the aluminum sulfate impurities in the titanium liquid are efficiently removed, and are converted into high-value aluminum sulfate hexadecahydrate products. The application effectively solves the problems of aluminum impurities in the titanium liquid interfering with hydrolysis, low TiO2 yield caused by improper concentration of trivalent titanium and poor quality of metatitanic acid, realizes accurate regulation and control of the composition of the titanium liquid and resource utilization of impurities, provides qualified raw materials for subsequent efficient hydrolysis for preparing high-quality titanium dioxide, and is stable in process, economical and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of VTM ironmaking waste slag resource utilization technology, specifically a method for pretreatment of VTM ironmaking waste slag to produce titanium liquid before hydrolysis. Background Technology

[0002] Titanium molten metal produced from VTM ironmaking waste contains a large amount of impurities such as aluminum sulfate and magnesium sulfate, and the trivalent titanium content differs significantly between blast furnace slag and gas-based vertical shaft furnace slag. If aluminum removal and control of the trivalent titanium concentration in the titanium molten metal before hydrolysis are not performed, the aluminum sulfate and ferric sulfate in the titanium molten metal will hydrolyze during hydrolysis, resulting in metatitanic acid produced that does not meet the quality requirements for pigment titanium dioxide. Titanium molten metal prepared from gas-based vertical shaft furnace slag has a high trivalent titanium content, but the trivalent titanium hydrolysis rate is very low. Without treatment, this will lead to a significant reduction in TiO2 yield and substantial waste. Summary of the Invention

[0003] To address the problems in the background art, the present invention provides a method for pretreatment before hydrolysis of titanium liquid produced from VTM ironmaking waste slag. For titanium liquid produced from blast furnace slag, aluminum powder reduction is used to control the concentration of trivalent titanium in the titanium liquid within an appropriate range, ensuring that divalent iron in the titanium liquid will not be oxidized to trivalent iron during the process before hydrolysis.

[0004] A combination of processes, including concentration, coarse crystallization, and purified crystallization, is used to remove aluminum sulfate from titanium solution and transform it into aluminum sulfate hexahydrate, a product with higher added value.

[0005] The dealuminated titanium solution is concentrated before hydrolysis to improve the hydrolysis yield. For the high concentration of trivalent titanium in the titanium solution prepared from gas-based vertical shaft furnace slag, oxygen or ozone is used to oxidize it to a specified concentration, ensuring a high TiO2 yield during subsequent titanium solution hydrolysis.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for pretreatment of titanium molten metal produced from VTM ironmaking waste slag before hydrolysis includes the following steps: Step 1: Titanium liquid reduction Selective processing is carried out based on the source and composition of the titanium solution: For titanium liquid produced from VTM blast furnace slag that does not contain trivalent titanium but contains iron ions, it is introduced into a reduction tank, aluminum powder is added to carry out a reduction reaction, and the concentration of trivalent titanium is generated and controlled. For titanium liquid containing trivalent titanium produced from VTM ironmaking gas-based vertical shaft furnace slag, it is directly sent to step two; Step 2: Dealuminization of titanium solution The titanium liquid processed in step one is concentrated, and then coarse crystallization and disc filtration are carried out in sequence to obtain dealuminized titanium liquid and coarse aluminum crystals. The dealuminized titanium solution is further concentrated. If the concentrations of TiO2 and trivalent titanium meet the requirements, it is sent to the outside; if the concentration of trivalent titanium exceeds the upper limit, it is sent to the titanium solution oxidation process in step three. The crude aluminum crystals were purified and dried to obtain aluminum sulfate product, which was then sent outside the region. Step 3: Titanium liquid oxidation The titanium liquid after step two is oxidized with oxygen or ozone to oxidize some of the trivalent titanium into TiOSO4, thus obtaining a titanium liquid that meets the requirements of the hydrolysis process.

[0007] Furthermore, in step one, the reduction reaction of adding aluminum powder reduces TiOSO4 to Ti2(SO4)3; after reduction, the concentration of trivalent titanium in the titanium liquid, calculated as TiO2, is controlled at 0.5~1.5 g / L.

[0008] Furthermore, in step two, the concentration method is MVR concentration, and the concentration of soluble titanium in the titanium liquid after the first concentration is controlled to be 90~150 g / L; the concentration of soluble titanium in the titanium liquid after the second concentration is controlled to be 190~210 g / L.

[0009] Furthermore, in step two, the aluminum sulfate content in the dealuminized titanium solution obtained through the disc filtration process is below 5%.

[0010] Furthermore, in step two, the coarse crystallization is concentrated by vacuum evaporation or by continuous freeze crystallization, with the temperature controlled at 20℃~30℃. At the same time, Al2(SO4)3·18H2O seed crystals are added to the coarse crystallization titanium liquid, with the seed crystal particle size controlled at 50~200 micrometers.

[0011] Furthermore, step two, purification and drying, includes the processes of crystal dissolution, purified crystallization, centrifugal washing, and vacuum drying.

[0012] Furthermore, the crystallization and dissolution process utilizes the condensate from the first concentration step and the dilute mother liquor from the centrifugal washing step; the water content after crystallization and dissolution is controlled at 55%~70%. Purification crystallization is carried out by vacuum evaporation crystallization, with the operating temperature controlled at 20℃~30℃. The evaporated process condensate is used as centrifugal washing water. Vacuum drying adopts disc vacuum drying, with the material drying temperature ranging from 40℃ to 70℃ and the vacuum degree maintained at -0.08 to -0.09 MPaG.

[0013] Furthermore, some crystals are separated from the purification and crystallization process and returned to the crude crystallization process for recycling as seed crystals.

[0014] Furthermore, in step three, the oxidation treatment controls the material temperature to not exceed 75℃; after oxidation, the concentration of trivalent titanium in the titanium liquid converted to TiO2 is 1~3 g / L, the F value is 1.75~2.18, and the TiO2 concentration is 190-210 g / L.

[0015] The beneficial effects of this invention are: 1) Effective control of titanium valence state to ensure hydrolysis efficiency and product quality: Addressing the significant differences in trivalent titanium content in titanium liquid from different sources (blast furnace slag / gas-based vertical shaft furnace slag), precise control methods of aluminum powder reduction and oxygen / ozone oxidation were employed. For blast furnace slag titanium liquid, the introduction of an appropriate amount of trivalent titanium through reduction effectively prevented the oxidation of divalent iron in subsequent processes, avoiding the harm to metatitanic acid quality caused by trivalent iron hydrolysis. For gas-based vertical shaft furnace slag titanium liquid, partial oxidation reduced excessively high concentrations of trivalent titanium, significantly improving the TiO2 yield in subsequent hydrolysis processes and preventing ferrous iron hydrolysis during water washing, laying a solid foundation for the production of high-quality pigment titanium dioxide.

[0016] 2) Efficient removal and resource utilization of aluminum sulfate impurities: Through a combination of "concentration-coarse crystallization-purification crystallization", the main impurity aluminum sulfate in the titanium solution is efficiently separated and converted into aluminum sulfate hexahydrate product with higher added value. This realizes the resource utilization of valuable components in the waste residue, reduces processing costs, and improves the overall economic efficiency of the process.

[0017] 3) Improved resource utilization efficiency and environmental friendliness: The method of this invention realizes high-value-added comprehensive utilization of VTM ironmaking waste slag, which not only improves the recovery rate of titanium elements, but also converts impurity aluminum sulfate into useful products, reduces the generation of solid waste, and conforms to the development concept of green circular economy. Attached Figure Description

[0018] The invention will now be further described with reference to the accompanying drawings.

[0019] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0021] A method for pretreatment of VTM ironmaking waste slag before hydrolysis for titanium liquid production, such as... Figure 1 As shown, it includes three steps: titanium liquid reduction, titanium liquid dealuminization, and titanium liquid oxidation. Specifically: Step 1: Titanium liquid reduction If the titanium liquid produced from VTM ironmaking waste slag (blast furnace slag) does not contain trivalent titanium but contains iron ions, then before dealuminization, the titanium liquid is introduced into a reduction tank and an appropriate amount of aluminum powder is added to control the trivalent titanium content in the titanium liquid within a specified range. The reaction that occurs during the preparation of trivalent titanium is as follows: 6TiOSO4+6H2SO4+2Al=Al2(SO4)3+3Ti2(SO4)3+6H2O If the titanium liquid produced from VTM ironmaking waste (gas-based vertical shaft furnace slag) contains a large amount of trivalent titanium, then the titanium liquid produced from VTM ironmaking waste from outside the boundary will be directly introduced into the MVR concentration system.

[0022] The titanium liquid prepared from blast furnace slag contains 8%~15% TiOSO4, 0.2%~1.0% FeSO4, 5%~15% Al2(SO4)3, 3%~8% MgSO4, less than 0.3% CaSO4, 2%~5% H2SO4, 50%~70% H2O, and about 1% of other components.

[0023] The titanium liquid prepared by the gas-based vertical furnace contains 8%~15% TiOSO4, 5%~10% Ti2(SO4)3, 0.2%~3.0% FeSO4, 5%~15% Al2(SO4)3, 3%~9% MgSO4, less than 0.3% CaSO4, 2%~5% H2SO4, 45%~70% H2O, and about 1% of other components.

[0024] After reduction of titanium liquid, the concentration of trivalent titanium (converted to TiO2) is controlled at 0.5~1.5g / L.

[0025] Step 2: Dealuminization of titanium solution The titanium liquid from outside the boundary or from step one is sequentially processed through MVR concentration, coarse crystallization, and disc filtration to obtain dealuminized titanium liquid. The dealuminized titanium liquid is further concentrated and then sent to the titanium liquid oxidation process (titanium liquid prepared from gas-based vertical furnace slag). After the concentrations of TiO2 and trivalent titanium in the titanium liquid are controlled to meet the requirements, it is sent out of the boundary.

[0026] After MVR concentration, the concentration of TiO2 (soluble titanium) is controlled at 90~150g / L.

[0027] The coarse crystallization is carried out by vacuum evaporation concentration or continuous freeze crystallization, with the temperature controlled at 20℃~30℃. At the same time, Al2(SO4)3·18H2O seed crystals are added to the coarse crystallization titanium liquid, and the seed crystal particle size is controlled at 50~200 micrometers.

[0028] The crude aluminum crystals (Al2(SO4)3·18H2O) obtained from the disc filter are then subjected to crystallization dissolution, purification crystallization, centrifugation washing, and vacuum drying to obtain the finished aluminum sulfate product (Al2(SO4)3·16H2O). The aluminum sulfate content in the titanium liquid obtained by disc filtration is controlled to be below 5%; The crystallization dissolution process utilizes process condensate from the MVR concentration step and dilute mother liquor from the centrifugal washing step. The water content after dissolution is controlled between 55% and 70%.

[0029] A portion of the crystals is separated from the purification and crystallization process and sent to the seed crystal preparation process. The prepared seed crystals are then added to the coarse crystallization process as crystallization centers to promote rapid crystal growth.

[0030] Purification crystallization was performed using vacuum evaporation crystallization, with the operating temperature controlled at 20℃~30℃. The evaporated condensate was used as centrifugal washing water.

[0031] Vacuum drying adopts disc vacuum drying, with the material drying temperature ranging from 40℃ to 70℃ and the vacuum degree maintained at -0.08 to -0.09 MPaG.

[0032] After dealumination, the titanium solution is concentrated using MVR (Medium-Vacuum Reduction) to maintain a soluble titanium concentration of approximately 190-210 g / L.

[0033] Step 3: Titanium liquid oxidation To improve the yield of TiO2 in subsequent hydrolysis and prevent the oxidation of ferrous iron in the titanium melt, the ferric titanium (from gas-based vertical shaft furnace slag) needs to be partially oxidized to TiOSO4 before being sent to an off-site hydrolysis process. Oxygen or ozone is used as the oxidation medium. The reaction is as follows: 2Ti2(SO4)3+O2+2H2O=4TiOSO4+2H2SO4 Or 2Ti₂(SO₄)₃ + O₃ + 2H₂O = 4TiOSO₄ + 2H₂SO₄ + 0.5O₂↑ The content of trivalent titanium (converted to TiO2) in the oxidized titanium liquid is controlled at 1~3 g / L, the F value (effective acid concentration / total TiO2 concentration) is controlled at 1.75~2.18, and the TiO2 concentration is controlled at around 190~210 g / L. The material temperature is controlled not to exceed 75℃ during the oxidation process.

[0034] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for pretreatment of VTM ironmaking waste slag before hydrolysis for titanium liquid production, characterized in that, Includes the following steps: Step 1: Titanium liquid reduction Selective processing is carried out based on the source and composition of the titanium solution: For titanium liquid produced from VTM blast furnace slag that does not contain trivalent titanium but contains iron ions, it is introduced into a reduction tank, aluminum powder is added to carry out a reduction reaction, and the concentration of trivalent titanium is generated and controlled. For titanium liquid containing trivalent titanium produced from VTM ironmaking gas-based vertical shaft furnace slag, it is directly sent to step two; Step 2: Dealuminization of titanium solution The titanium liquid processed in step one is concentrated, and then coarse crystallization and disc filtration are carried out in sequence to obtain dealuminized titanium liquid and coarse aluminum crystals. The dealuminized titanium solution is further concentrated. If the concentrations of TiO2 and trivalent titanium meet the requirements, it is sent to the outside; if the concentration of trivalent titanium exceeds the upper limit, it is sent to the titanium solution oxidation process in step three. The crude aluminum crystals were purified and dried to obtain aluminum sulfate product, which was then sent outside the region. Step 3: Titanium liquid oxidation The titanium liquid after step two is oxidized with oxygen or ozone to oxidize some of the trivalent titanium into TiOSO4, thus obtaining a titanium liquid that meets the requirements of the hydrolysis process.

2. The method according to claim 1, characterized in that, In step one, the addition of aluminum powder for reduction reaction reduces TiOSO4 to Ti2(SO4)3; after reduction, the concentration of trivalent titanium in the titanium liquid, calculated as TiO2, is controlled at 0.5~1.5 g / L.

3. The method according to claim 1, characterized in that, In step two, the concentration method is MVR concentration, and the concentration of soluble titanium in the titanium liquid after the first concentration is controlled to be 90~150 g / L; the concentration of soluble titanium in the titanium liquid after the second concentration is controlled to be 190~210 g / L.

4. The method according to claim 1, characterized in that, In step two, the aluminum sulfate content in the dealuminized titanium solution obtained through the disc filtration process is below 5%.

5. The method according to claim 1, characterized in that, In step two, the coarse crystallization is carried out by vacuum evaporation concentration or continuous freeze crystallization, with the temperature controlled at 20℃~30℃. At the same time, Al2(SO4)3·18H2O seed crystals are added to the coarse crystallization titanium liquid, with the seed crystal particle size controlled at 50~200 micrometers.

6. The method according to claim 1, characterized in that, Step two, purification and drying, includes the processes of crystal dissolution, purification crystallization, centrifugation and washing, and vacuum drying.

7. The method according to claim 6, characterized in that, The crystallization and dissolution process utilizes the condensate from the first concentration step and the dilute mother liquor from the centrifugal washing step; the water content after crystallization and dissolution is controlled at 55%~70%. Purification crystallization is carried out by vacuum evaporation crystallization, with the operating temperature controlled at 20℃~30℃. The evaporated process condensate is used as centrifugal washing water. Vacuum drying adopts disc vacuum drying, with the material drying temperature ranging from 40℃ to 70℃ and the vacuum degree maintained at -0.08 to -0.09 MPaG.

8. The method according to claim 6 or 7, characterized in that, Some crystals are separated from the purification and crystallization process and returned to the crude crystallization process for recycling as seed crystals.

9. The method according to claim 1, characterized in that, In step three, the oxidation treatment controls the material temperature to not exceed 75℃; after oxidation, the concentration of trivalent titanium in the titanium liquid converted to TiO2 is 1~3 g / L, the F value is 1.75~2.18, and the TiO2 concentration is 190-210 g / L.

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