Method for preparing artificial rutile by leaching titanium concentrate

Abstract

The invention relates to the field of chemical industry, and discloses a method for preparing artificial rutile by titanium concentrate leaching, which comprises the following steps: titanium concentrate and acid liquor are added into a reactor for leaching reaction, and the reaction process comprises a heating stage, a rapid reaction stage and a reaction endpoint control stage which are carried out in sequence; in the heating stage, heating is stopped after the reaction system reaches the preset temperature through heating; in the rapid reaction stage, the pressure of the reaction system is controlled to be within a preset pressure range; in the reaction endpoint control stage, the reaction is finished when the temperature and the pressure of the reaction system are reduced. According to the method, the leaching time can be effectively shortened and the energy consumption can be reduced on the basis of ensuring the product quality by finely regulating and controlling the leaching reaction process, so that the production efficiency is improved and the production cost is saved.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a method for preparing synthetic rutile by leaching titanium concentrate. Background Technology

[0002] Currently, the high-quality raw materials used in the production of titanium dioxide mainly come from two sources. One source is low-calcium magnesium high-titanium slag with a TiO2 grade of 90% or 92% obtained by smelting high-quality ilmenite sand with low calcium and magnesium content in an electric furnace. The other source is high-quality titanium-rich raw materials (natural rutile, synthetic rutile, and upgraded titanium slag) that meet the required standards.

[0003] The titanium concentrate produced in the Panzhihua-Xichang region is a typical ilmenite deposit, characterized by the symbiotic occurrence of multiple elements, low TiO2 grade, low Ti+Fe content, and high impurity content, particularly high MgO and CaO content. After electric furnace smelting, the acid-soluble titanium slag has a high CaO+MgO content, making it unsuitable for direct use in the fluidized bed chlorination process for producing titanium dioxide and titanium metal. The acid leaching process for preparing synthetic rutile is one of the effective and industrially viable methods for producing high-quality titanium raw materials from Panzhihua titanium concentrate. In this process, dilute hydrochloric acid reacts with impurities such as FeO, MgO, CaO, MnO, and Al2O3 in the titanium concentrate to form soluble salts that enter the liquid phase. TiO2 is then enriched in the solid phase to obtain high-quality synthetic rutile.

[0004] To ensure the effectiveness and efficiency of hydrochloric acid leaching for impurity removal, the leaching reaction is usually carried out in a closed reactor under certain pressure. However, this process is not easily visualized, and stopping the reaction before it is complete will severely impact the quality and value of the synthetic rutile product. Therefore, extending the reaction time is often used to maintain product quality. This not only wastes energy but also disrupts the production schedule, resulting in low equipment utilization, increased production costs, and reduced overall economic efficiency.

[0005] Therefore, existing technologies still need improvement. Summary of the Invention

[0006] The main objective of this invention is to provide a method for preparing synthetic rutile by leaching titanium concentrate, thereby solving the technical problems of low production efficiency and high production cost in existing methods for preparing synthetic rutile by acid leaching of titanium concentrate.

[0007] According to one aspect of the present invention, a method for preparing synthetic rutile by leaching titanium concentrate is provided, comprising: adding titanium concentrate and acid to a reactor for leaching reaction, the reaction process including a heating stage, a rapid reaction stage and a reaction endpoint control stage in sequence; in the heating stage, heating is stopped after the reaction system reaches a predetermined temperature; in the rapid reaction stage, the pressure of the reaction system is controlled within a predetermined pressure range; in the reaction endpoint control stage, the reaction is terminated when both the temperature and pressure of the reaction system decrease.

[0008] According to one embodiment of the present invention, during the heating stage, the predetermined temperature is 136~140°C.

[0009] According to one embodiment of the present invention, during the heating stage, the heating rate is 3~10℃ / min.

[0010] According to one embodiment of the present invention, during the heating stage, heating is performed by steam heating and / or electric heating.

[0011] According to one embodiment of the present invention, during the rapid response phase, the predetermined pressure range is 0.3~0.4 MPa.

[0012] According to one embodiment of the present invention, controlling the pressure of the reaction system within a predetermined pressure range includes: when the pressure of the reaction system is greater than 0.4 MPa, opening the pressure relief valve of the reactor to release pressure, so that the pressure of the reaction system drops to 0.35~0.4 MPa.

[0013] According to one embodiment of the present invention, controlling the pressure of the reaction system within a predetermined pressure range includes: when the temperature of the reaction system reaches its maximum value and the pressure of the reaction system is less than 0.3 MPa, heating is performed to increase the pressure of the reaction system to 0.3~0.35 MPa.

[0014] According to one embodiment of the present invention, in the reaction endpoint control stage, the reaction is terminated when the temperature of the reaction system decreases by a predetermined first decrease and the pressure of the reaction system decreases by a predetermined second decrease.

[0015] According to one embodiment of the present invention, in the reaction endpoint control stage, the first decrease is 0.1~0.3℃ / min, and the second decrease is 0.001~0.003MPa / min.

[0016] According to one embodiment of the present invention, the ratio of titanium concentrate to acid is 1 kg: (2~4) L, the mass concentration of acid is 15~26%, and the acid is hydrochloric acid melt.

[0017] In the technical solution of this invention, the entire leaching reaction process is divided into three stages for refined control: a heating stage, a rapid reaction stage, and a reaction endpoint control stage. In the heating stage, external heating is used to raise the system to a certain temperature, inducing a reaction between the titanium concentrate and the acid solution, and allowing the reaction to reach a certain rate before heating is stopped. In the rapid reaction stage, once the reaction reaches a certain rate, the exothermic reaction itself causes the system temperature and pressure to rise, optimizing the reaction kinetics and further increasing the reaction rate. Pressure is adjusted to improve reaction efficiency while ensuring safety. In the reaction endpoint control stage, the reaction endpoint is accurately determined based on temperature and pressure, and the reaction is terminated promptly. Through the control of these three stages, leaching time can be effectively shortened and energy consumption reduced while ensuring product quality, thereby improving production efficiency and saving production costs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for preparing synthetic rutile by leaching titanium concentrate according to an embodiment of the present invention is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0021] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0022] refer to Figure 1 This invention proposes a method for preparing synthetic rutile by leaching titanium concentrate, comprising: Titanium concentrate and acid are added to a reactor for leaching reaction. The reaction process includes a heating stage, a rapid reaction stage and a reaction endpoint control stage, which are carried out sequentially. During the heating stage, heating is stopped once the reaction system reaches the predetermined temperature. During the rapid reaction phase, the pressure of the reaction system is controlled within a predetermined pressure range; In the endpoint control phase of the reaction, the reaction ends when both the temperature and pressure of the reaction system decrease.

[0023] This invention, through in-depth analysis of the characteristics of titanium concentrate and the liquid-solid reaction mechanism of acid leaching, divides the entire leaching reaction process into three stages: the heating stage in the early stage of the reaction, the rapid reaction stage in the middle stage, and the endpoint control stage in the later stage. The main characteristics of these three stages are as follows: Heating stage: External heating is used to bring the system to a certain temperature, inducing the reaction between titanium concentrate and hydrochloric acid, and allowing the reaction to reach a certain rate before stopping the heating. If the temperature is too low, the reaction will be too slow, the leaching time will be prolonged, and the product quality and reactor efficiency will be significantly affected.

[0024] Rapid reaction stage: Once the reaction reaches a certain rate, the exothermic reaction itself leads to an increase in system temperature and pressure, optimizing reaction kinetics and further accelerating the reaction rate. This rapid reaction stage builds upon the heating stage, effectively controlling external heating and the self-heating of the reaction system to achieve a fast and efficient reaction. During this stage, pressure is controlled to improve reaction efficiency while ensuring safety. Poor control can lead to a rapid increase in reactor temperature and pressure, posing a risk of overheating, overpressure, and explosion. To prevent such explosions, forcefully depressurizing the reactor would cause a large amount of gas produced by the acid solution (such as HCl gas) to escape, reducing the effective acid content and severely impacting product quality.

[0025] Reaction endpoint control stage (product quality control stage): Accurately determine the reaction endpoint based on temperature and pressure and stop the reaction in a timely manner. If the reaction is stopped too early, the reaction will be incomplete, which will affect product quality. If the reaction is stopped too late, the leaching time will be prolonged, the reactor operating rate will decrease, and the production cost will be affected.

[0026] This invention effectively regulates the reaction system at each stage based on temperature and / or pressure changes. Through precise staged regulation, it saves on leaching efficiency, effectively shortens leaching time, and ensures the quality of synthetic rutile products.

[0027] In some embodiments, the ratio of titanium concentrate to acid is 1 kg:(2~4) L, the mass concentration of the acid is 15~26%, and the acid is a hydrochloric acid melt. A suitable acid concentration and solid-liquid ratio ensure effective leaching. It should be understood that in other embodiments, other acids such as sulfuric acid solution can also be selected as appropriate. The reactor can be a closed pressurized reactor equipped with measuring instruments such as thermometers and pressure gauges. Different specifications of closed pressurized reactors can be selected as needed.

[0028] During the heating stage, steam heating and / or electric heating can be used. Steam can be introduced into the reactor jacket, heat exchange channels, etc., for heating. The amount of steam used can be 5-7 kg. To better control the efficiency of the titanium concentrate leaching reaction, the predetermined temperature during the heating stage can be 136-140℃, and the heating rate can be 3-10℃ / min (e.g., 5-8℃ / min). Temperature is the primary control factor during the heating stage; external heating is stopped when the reaction system temperature reaches 136-140℃. Pressure is an auxiliary control factor, controlled at 0.15-0.25 MPa. In some existing technologies, the reaction is slowly heated at a lower temperature throughout until the predetermined time is reached (e.g., the steam inlet valve is opened to about 1 / 3, and heating is carried out at a temperature of about 125℃ for about 7 hours). Unlike existing technologies, this invention rapidly heats the product to a high temperature (136~140°C) during the heating stage (e.g., the steam inlet valve is fully open) to quickly initiate the reaction. Then, heating is stopped, and the reaction continues by utilizing its own exothermic reaction.

[0029] During the rapid reaction phase, the predetermined pressure range is 0.3~0.4 MPa. Pressure is the primary control factor during this phase, maintaining high reaction efficiency while ensuring the reactor's pressure-bearing capacity and safe, stable operation. In some embodiments, when the pressure of the reaction system exceeds 0.4 MPa, the reactor's pressure relief valve is opened for slight pressure relief, reducing the pressure to 0.35~0.4 MPa. Although pressure relief may cause HCl gas to escape and affect product quality, this invention involves only slight pressure relief, resulting in minimal HCl gas escape and minimal impact on product quality. This effectively shortens the leaching time and saves production costs while minimizing impact on product quality, achieving a balance between product quality and production efficiency. In some embodiments, during the later stages of the rapid reaction phase, the system temperature rises rapidly to its maximum value (which can be considered as the system temperature reaching its maximum if it stops rising within a predetermined time (e.g., 3 minutes)). When the system temperature reaches its maximum value and the pressure is less than 0.3 MPa, external heating can be activated to raise the system pressure to 0.3~0.35 MPa. During the rapid reaction phase, the reaction system temperature is a secondary control factor.

[0030] In the reaction endpoint control stage, temperature and pressure are jointly controlled. After the titanium concentrate undergoes a rapid reaction period, the reaction system reaches steady-state equilibrium, with both temperature and pressure maintained at high levels. As the reaction proceeds, impurities in the titanium concentrate decrease, the reaction rate slows down, heat release decreases, and the reaction approaches its endpoint. When the heat released by the system is less than the heat dissipated by the reactor, the system temperature gradually decreases, followed by a decrease in both temperature and pressure. Therefore, when the temperature of the reaction system decreases by a predetermined first decrease and the pressure of the reaction system decreases by a predetermined second decrease, the reaction is considered to have reached its endpoint and can be terminated. In some embodiments, the first decrease can be 0.1~0.3℃ / min, and the second decrease can be 0.001~0.003MPa / min. Stopping the reaction may include: depressurizing and cooling the reactor, removing the liquid-solid mixture, and filtering and washing it to obtain the synthetic rutile product.

[0031] This invention achieves precise, staged control of the acid leaching reaction process of titanium concentrate by combining temperature and pressure. The method is simple and straightforward, significantly improving reactor operating rates and controlling product quality. This invention is applicable not only to the production of high-quality synthetic rutile from vanadium-titanium magnetite in the Panzhihua-Xichang region, but also to the production of synthetic rutile from other types of titanium concentrate.

[0032] The following description is based on specific embodiments and comparative examples.

[0033] Example 1 Using a volume of 20m³ 3 The reactor is equipped with a steel-lined ceramic reactor, a mechanical stirring system, and a steam heating system for pressurized hydrochloric acid leaching of Panzhihua-Xichang titanium concentrate to produce synthetic rutile. The leaching reaction is a batch operation, with a batch input of 4.5–5.6 tons of titanium concentrate, a dilute hydrochloric acid concentration of 15%–26%, and an addition volume of 12–18 mg / L. 3 6 kg of saturated steam is used as external heating. The specific process includes the following steps: 1. Add titanium concentrate and dilute hydrochloric acid to the reactor, start stirring, and introduce a large amount of steam for rapid heating. When the temperature of the reaction system rises to 138°C, close the steam valve and the pressure inside the reactor rises to 0.26 MPa.

[0034] 2. As the titanium concentrate reacts rapidly with hydrochloric acid, the system temperature gradually increases. The initial reaction rate is relatively fast, the temperature rises rapidly, and the system pressure also increases accordingly, reaching a maximum pressure of 0.376 MPa and a temperature of 161.8℃.

[0035] 3. Keep the stirring in the reactor stable. After 100 minutes, the reactor temperature will show a decreasing trend (the decrease will be 0.1~0.3℃ / min), while the pressure will remain basically unchanged. After 20 minutes, the reactor pressure will show a decreasing trend, and after 15 minutes, the decreasing trend will gradually increase, reaching a decrease of 0.001~0.003MPa / min. The titanium concentrate leaching reaction is complete.

[0036] 4. Depressurize and cool the reactor, release the liquid-solid mixture, filter and wash to obtain the synthetic rutile product.

[0037] Example 2 Using a volume of 20m³ 3 The reactor is equipped with a steel-lined ceramic reactor, a mechanical stirring system, and a steam heating system for pressurized hydrochloric acid leaching of Panzhihua-Xichang titanium concentrate to produce synthetic rutile. The leaching reaction is a batch operation, with a batch input of 4.5–5.6 tons of titanium concentrate, a dilute hydrochloric acid concentration of 15%–26%, and an addition volume of 12–18 mg / L. 3 6 kg of saturated steam is used as external heating. The specific process includes the following steps: 1. Add titanium concentrate and dilute hydrochloric acid to the reactor, start stirring, and introduce a large amount of steam for rapid heating. When the temperature of the reaction system rises to 140°C, close the steam valve and the pressure inside the reactor rises to 0.285 MPa.

[0038] 2. As the titanium concentrate reacts rapidly with hydrochloric acid, the system temperature gradually increases. The initial reaction rate is relatively fast, the temperature rises rapidly, and the system pressure also increases accordingly, reaching a maximum pressure of 0.397 MPa and a temperature of 165.8℃.

[0039] 3. Keep the stirring in the reactor stable. After 94 minutes, the reactor temperature will show a decreasing trend (the decrease will be 0.1~0.3℃ / min), while the pressure will remain basically unchanged. After 23 minutes, the reactor pressure will show a decreasing trend, and after 17 minutes, the decreasing trend will gradually increase, with the decrease reaching 0.001~0.003MPa / min. The titanium concentrate leaching reaction is complete.

[0040] 4. Depressurize and cool the reactor, release the liquid-solid mixture, filter and wash to obtain the synthetic rutile product.

[0041] Comparative Example 1 Using a volume of 20m³ 3 The reactor is equipped with a steel-lined ceramic reactor, a mechanical stirring system, and a steam heating system for pressurized hydrochloric acid leaching of Panzhihua-Xichang titanium concentrate to produce synthetic rutile. The leaching reaction is a batch operation, with a batch input of 4.5–5.6 tons of titanium concentrate, a dilute hydrochloric acid concentration of 15%–26%, and an addition volume of 12–18 mg / L. 36 kg of saturated steam is used as external heating. The specific process includes the following steps: 1. Add titanium concentrate and dilute hydrochloric acid to the reactor, start stirring, and introduce a large amount of steam for rapid heating. When the temperature of the reaction system rises to 141°C, close the steam valve and the pressure inside the reactor rises to 0.295 MPa.

[0042] 2. As the titanium concentrate reacts rapidly with hydrochloric acid, the system temperature gradually increases. The reaction rate is relatively fast in the early stage, and the temperature rises rapidly, so the system pressure also increases. After 30 minutes, the pressure in the reactor reaches 0.4 MPa, triggering an overpressure alarm. The pressure regulating valve opens to release pressure and discharge a small amount of gas. The temperature of the reaction system reaches 166.5℃.

[0043] 3. Keep the stirring in the reactor stable. The reactor will trigger multiple overpressure alarms and require frequent depressurization. The temperature will fluctuate between 155.1 and 166.5℃ (the temperature will drop rapidly after depressurization and then gradually rise again after stabilization). After 55 minutes, the reactor pressure will show a decreasing trend, and after 35 minutes, the decreasing trend will gradually increase, with a drop of 0.001 to 0.003 MPa / min.

[0044] 4. Depressurize and cool the reactor, release the liquid-solid mixture, filter and wash to obtain the synthetic rutile product.

[0045] Comparative Example 2 Using a volume of 20m³ 3 The reactor is equipped with a steel-lined ceramic reactor, a mechanical stirring system, and a steam heating system for pressurized hydrochloric acid leaching of Panzhihua-Xichang titanium concentrate to produce synthetic rutile. The leaching reaction is a batch operation, with a batch input of 4.5–5.6 tons of titanium concentrate, a dilute hydrochloric acid concentration of 15%–26%, and an addition volume of 12–18 mg / L. 3 6 kg of saturated steam is used as external heating. The specific process includes the following steps: 1. Add titanium concentrate and dilute hydrochloric acid to the reactor, start stirring, and introduce a large amount of steam for rapid heating. When the temperature of the reaction system rises to 130°C, close the steam valve and the pressure inside the reactor rises to 0.21 MPa.

[0046] 2. As the titanium concentrate reacted with hydrochloric acid, the system temperature gradually increased, and the system pressure also increased accordingly, reaching a maximum pressure of 0.377 MPa and a temperature of 165.2℃. The system heating rate was relatively slow; the time to reach the maximum temperature of 165℃ was extended from 30 minutes in Example 1 to 75 minutes, indicating that the temperature control in the first stage was too low, resulting in insufficient induction of the reaction.

[0047] 3. Keep the stirring in the reactor stable. After 104 minutes, the temperature in the reactor begins to decrease, while the pressure remains relatively constant. After 33 minutes, the pressure in the reactor begins to decrease, and after 12 minutes, the decreasing trend gradually increases, indicating that the titanium concentrate leaching reaction is complete.

[0048] 4. Depressurize and cool the reactor, release the liquid-solid mixture, filter and wash to obtain the synthetic rutile product.

[0049] The titanium concentrate used in Examples 1-2 and Comparative Examples 1-2 had the same composition, and the main components of the titanium concentrate are shown in Table 1. The leaching time and the main components of the prepared synthetic rutile in Examples 1-2 and Comparative Examples 1-2 are also shown in Table 1. Table 1 also shows the main components of synthetic rutile obtained by leaching titanium concentrate of the same composition with hydrochloric acid using conventional methods, wherein the conventional method includes heating at 125±5℃ for 7 hours throughout the process.

[0050] Table 1. Main chemical components of titanium concentrate, leaching time, and main chemical components of synthetic rutile.

[0051] As shown in Table 1, excluding sampling errors, the rutile grades obtained in Examples 1 and 2 of this invention are basically consistent with those obtained by conventional methods. The leaching effects of impurities FeO, MgO, CaO, MnO2, Al2O3, and Fe2O3 are also basically consistent. The leaching time was reduced from the original 420 min to about 240 min, significantly reducing the leaching time. Comparative Examples 1 and 2 verify that improper operation will affect the quality of synthetic rutile products, and the leaching time will also be affected to a certain extent, verifying the rationality of the method control of this invention. In Comparative Example 1, there were multiple overpressure alarms in the reactor and pressure relief of the regulating valve. The operation was frequent and the workload was large. In addition, the pressure relief caused HCl to escape with the gas, increasing the tail gas treatment load and reducing the concentration of hydrochloric acid in the leaching, which affected the quality of synthetic rutile products. In Comparative Example 2, the temperature control in the first stage was too low, resulting in insufficient induction of the reaction and a prolonged leaching time.

[0052] In summary, addressing the challenges of controlling the production of synthetic rutile from Panzhihua-Xichang titanium concentrate using hydrochloric acid pressure leaching, this invention, through in-depth analysis of the titanium concentrate material characteristics and the liquid-solid reaction mechanism of hydrochloric acid leaching, masteres the reaction process and proposes a reasonable control method. The leaching process is divided into three stages, with different control factors applied to each stage to achieve accurate control. This method not only effectively solves the problems of over-temperature and over-pressure during production but also significantly reduces leaching time, improves the operating rate of the pressure leaching reactor, and ensures product quality. This method is simple, reliable, easy to implement, and its effectiveness has been verified through production. The method can be implemented on existing equipment without additional investment, operates stably, and is easily industrialized.

[0053] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing synthetic rutile by leaching titanium concentrate, characterized in that, include: Titanium concentrate and acid are added to a reactor for leaching reaction. The reaction process includes a heating stage, a rapid reaction stage and a reaction endpoint control stage, which are carried out sequentially. During the heating stage, heating is stopped once the reaction system reaches a predetermined temperature. During the rapid reaction phase, the pressure of the reaction system is controlled within a predetermined pressure range. In the reaction endpoint control phase, the reaction ends when both the temperature and pressure of the reaction system decrease.

2. The method according to claim 1, characterized in that, During the heating stage, the predetermined temperature is 136~140℃.

3. The method according to claim 1, characterized in that, During the heating stage, the heating rate is 3~10℃ / min.

4. The method according to claim 1, characterized in that, During the heating stage, heating is performed using steam heating and / or electric heating.

5. The method according to claim 1, characterized in that, During the rapid response phase, the predetermined pressure range is 0.3~0.4 MPa.

6. The method according to claim 5, characterized in that, Controlling the pressure of the reaction system within a predetermined pressure range includes: when the pressure of the reaction system is greater than 0.4 MPa, opening the pressure relief valve of the reactor to release pressure, so that the pressure of the reaction system drops to 0.35~0.4 MPa.

7. The method according to claim 5, characterized in that, Controlling the pressure of the reaction system within a predetermined pressure range includes: when the temperature of the reaction system reaches its maximum value and the pressure of the reaction system is less than 0.3 MPa, heating is performed to increase the pressure of the reaction system to 0.3~0.35 MPa.

8. The method according to claim 1, characterized in that, In the reaction endpoint control phase, the reaction ends when the temperature of the reaction system decreases by a predetermined first decrease and the pressure of the reaction system decreases by a predetermined second decrease.

9. The method according to claim 8, characterized in that, The first decrease is 0.1~0.3℃ / min, and the second decrease is 0.001~0.003MPa / min.

10. The method according to claim 1, characterized in that, The ratio of titanium concentrate to acid solution is 1 kg:(2~4) L, the mass concentration of acid solution is 15~26%, and the acid solution is hydrochloric acid melt.

Images