Gradient leaching method for calcified clinker

Abstract

The invention relates to the technical field of hydrometallurgy, in particular to a calcified clinker gradient leaching method. A calcified clinker gradient leaching method comprises the following steps that first gradient leaching is conducted, specifically, a first mother solution and calcified roasting clinker are mixed according to the liquid-solid ratio of (1.5-2.5) L: 1 kg, leaching is conducted under the condition that the pH ranges from 3.5 to 7.0, and first gradient acid leaching liquid and first gradient acid leaching residues are obtained; and second-stage leaching: mixing the first-stage acid leaching residues with a second mother solution according to a liquid-solid ratio of (0.5-0.7) L: 1kg, and leaching under the condition that the pH is less than or equal to 1.5 to obtain second-stage acid leaching liquid and second-stage acid leaching residues. According to the method, efficient vanadium extraction is achieved through the two-stage differential leaching process, the limitation of traditional single-pH leaching is broken through, efficient cooperation of high concentration, low residue and low impurity is achieved, and the industrial problem that the concentration and the residue content are mutually restricted in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a step-by-step leaching method for calcified clinker. Background Technology

[0002] Vanadium-grade solution is an important intermediate product in the production of vanadium oxide. Its quality is mainly reflected in the vanadium concentration and impurity content. Low vanadium concentration and high impurity content affect the quality of precipitated ammonium polyvanadate, which in turn affects the quality of vanadium oxide products, impacting production stability and system yield. Currently, the vanadium concentration in vanadium-grade solution fluctuates significantly, ranging from 15 to 28 g / L, with an average of about 22 g / L. Therefore, measures must be taken to suppress this fluctuation, which increases costs and reduces production efficiency.

[0003] To address the common technical challenges in the vanadium industry caused by traditional sodium vanadium extraction processes, such as high environmental protection difficulties, high investment, high vanadium oxide production costs, and low resource utilization, the invention patent application with authorization announcement number CN106987716B provides a method for improving the leaching rate of vanadium slag calcification roasting clinker. This method uses a sulfuric acid intermittent leaching process to achieve the goal of increasing the vanadium leaching rate. Although this continuous acid leaching method improves production efficiency by connecting multiple tanks in series, the use of a uniform low pH value (2.5~3.2) and a fixed liquid-to-solid ratio (1:1.5~4) throughout the process makes it impossible to simultaneously meet the dual requirements of high-concentration qualified solution and low residue content during vanadium leaching. Increasing the concentration of the leaching solution requires reducing the liquid-to-solid ratio, but this will exacerbate the vanadium residue (0.8~2.5%). On the other hand, reducing the residue content requires increasing the amount of acid used, which not only causes a large amount of impurity ions (such as Fe, Mn, Si, P, Pb, etc.) to dissolve (with a concentration of 1.2~1.8 g / L), but also results in acid consumption of up to 7~8 tons per ton of V2O5, which limits both economic efficiency and product quality.

[0004] The invention patent application with publication number CN105219976A provides a method for improving the leaching rate of vanadium slag calcined clinker. This method only uses a single pH condition (usually strong acid) for leaching, resulting in the vanadium content in the residue generally being >1.5% and the total leaching rate being only 95%~97%.

[0005] Furthermore, in both methods mentioned above, relying solely on pH control fails to address the differentiated solubility characteristics of vanadium species, thus limiting further improvements in vanadium recovery. Therefore, existing technologies still require improvement. Summary of the Invention

[0006] In view of this, in order to address the problems of high production cost and low efficiency of vanadium qualified solution with high vanadium concentration and low impurity content, this application proposes a step-by-step leaching method for calcified clinker, which can at least solve the technical problem that the existing vanadium leaching process cannot simultaneously meet the dual requirements of high concentration qualified solution and low residue content.

[0007] The present invention proposes a step-by-step leaching method for calcified clinker, comprising the following steps: First-stage leaching: The first mother liquor and calcined clinker are leached at a liquid-to-solid ratio of 1.5~2.5L:1kg under conditions of pH 3.5~7.0 to obtain the first-stage acid leaching solution and the first-stage acid leaching residue. The key to this stage is to achieve selective leaching of vanadium within a weakly acidic to neutral range through precise pH control, while effectively inhibiting the leaching of impurity elements such as iron, manganese, silicon, phosphorus, and lead.

[0008] Second-stage leaching: The first-stage acid leaching residue and the second mother liquor are mixed at a liquid-to-solid ratio of 0.5~0.7L:1kg, and leached under conditions of pH≤1.5 to obtain the second-stage acid leaching solution and the second-stage acid leaching residue. The high-acidity environment used in this stage can effectively destroy the insoluble calcium vanadate (Ca3(VO4)2) crystal structure in the first-stage acid leaching residue, and fully dissociate the residual vanadium through proton attack and coordination.

[0009] In some embodiments, the first mother liquor and / or the second mother liquor are water or a second-stage acid leaching solution obtained by second-stage leaching.

[0010] In some embodiments, the pH of the first and / or second leaching stages is adjusted by sulfuric acid, with a sulfuric acid concentration of 30%–98%. Preferably, in the first leaching stage, a sulfuric acid concentration of 30%–50% is used for adjustment. This concentration range allows for precise control of the weakly acidic to neutral environment to achieve selective vanadium leaching, while avoiding excessive acidity that would lead to the dissolution of large amounts of impurities such as iron, manganese, silicon, phosphorus, and lead. In the second leaching stage, a concentrated sulfuric acid concentration of 70%–98% is preferred for adjustment. The strong protonating ability of high-concentration sulfuric acid thoroughly destroys the crystal structure of calcium vanadate, while reducing the amount of liquid added to maintain a low liquid-to-solid ratio of 0.5–0.7 L:1 kg, thereby efficiently recovering residual vanadium and reducing the cost of subsequent vanadium solution precipitation.

[0011] In some embodiments, during the first-stage leaching process, the reaction temperature is 45~70°C and the leaching time is 60~90 min.

[0012] In some embodiments, during the second-stage leaching process, the reaction temperature is 40~60°C and the leaching time is 30~60 min.

[0013] In some embodiments, the liquid-to-solid ratio of the first mother liquor from the first stage leaching to the calcified roasted clinker is 2.0~2.3L:1kg. For example, at 18m... 3With the mother liquor volume remaining constant, the amount of calcined clinker should be controlled at over 8000 kg, not exceeding the total capacity of the leaching tank, ensuring no overflow. This ratio optimizes the mass transfer efficiency and reaction environment of the leaching system. It provides sufficient liquid medium to promote the efficient dissolution of vanadium from the calcined clinker while avoiding increased costs associated with subsequent vanadium solution precipitation processes.

[0014] In some embodiments, the liquid-to-solid ratio of the first-stage acid leaching residue to the second mother liquor in the second-stage leaching is 0.5~0.6L:1kg. For example, in a 9m... 3 With the mother liquor volume remaining constant, the first-stage acid leaching residue should be controlled at over 16,000 kg, not exceeding the total capacity of the leaching tank, ensuring no overflow. This ratio effectively improves the secondary leaching efficiency of vanadium and optimizes process economy, ensuring full vanadium recovery and efficient utilization of the leaching agent, achieving dual optimization of resource recovery and production costs.

[0015] In some embodiments, the first stage of leaching is carried out under continuous stirring conditions.

[0016] In some embodiments, the vanadium concentration in the first-stage acid leaching solution is 30-50 g / L, and the vanadium content in the first-stage acid leaching residue is 1.5-2.5%; the vanadium concentration in the second-stage acid leaching solution is 0.5-10 g / L; and the vanadium content in the second-stage acid leaching residue is 0.5-1.0%.

[0017] The beneficial effects of this invention are as follows: This application achieves efficient vanadium extraction through a two-stage differentiated leaching process. The first stage preferentially dissolves easily leached vanadium in a weakly acidic to neutral environment (pH 3.5~7.0), obtaining a high-concentration vanadium solution (30~50 g / L) while suppressing the co-dissolution of impurities such as iron, manganese, silicon, phosphorus, and lead, significantly reducing the subsequent purification load. The second stage, under strongly acidic conditions (pH≤1.5), specifically dissociates sparingly soluble calcium vanadate, increasing the residual vanadium leaching rate by more than 30% through proton-induced crystal structure destruction, ultimately reducing the total vanadium content in the slag to 0.5~1.0%. Compared to the traditional single-stage leaching process, this reduces vanadium loss by 40%~60%, achieving maximum recovery of vanadium resources and economic optimization of the leaching process. This process breaks through the limitations of traditional single pH leaching, increasing vanadium recovery rate to over 99%, reducing acid consumption by 25%, and reducing the impurity content of the first-stage acid leaching solution by 50%. It achieves high efficiency synergy of high concentration, low residue, and low impurities, solving the industry problem of mutual constraint between concentration and residue content in existing technologies. 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 embodiments can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart of a step-by-step leaching method for calcified clinker provided in one embodiment of the present invention; Figure 2 This is a flow diagram of a cascade leaching method for calcified clinker provided in one embodiment of the present invention. 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] This invention addresses the technical problem of existing vanadium leaching processes failing to simultaneously achieve both high-concentration qualified solutions and low residue content. The applicant has found that during stepwise leaching at pH 1.5–3.5, the resulting high-concentration vanadium solution is prone to low-acidity vanadium precipitation, while the low-concentration vanadium solution is prone to hydrolysis and vanadium precipitation. Based on this, the present invention proposes a stepwise leaching method for calcified clinker, achieving efficient vanadium extraction through a two-stage differentiated leaching process. This method is suitable for extracting vanadium from vanadium-titanium magnetite roasted clinker. The leaching method is as follows: Figure 1 As shown, it includes the following steps: First-stage leaching: The first mother liquor and calcined clinker are leached at a liquid-to-solid ratio of 1.5~2.5L:1kg under pH 3.5~7.0 conditions to obtain a first-stage acid leaching solution with a vanadium concentration of 30~50g / L and a first-stage acid leaching residue with a vanadium content (mass percentage) of 1.5~2.5%. The key to this stage is to achieve selective leaching of vanadium in a weakly acidic to neutral range through precise pH control, while effectively inhibiting the leaching of impurities such as iron, manganese, silicon, phosphorus, and lead.

[0023] Second-stage leaching: The first-stage acid leaching residue and the second mother liquor are mixed at a liquid-to-solid ratio of 0.5~0.7L:1kg, and leached under pH≤1.5 conditions to obtain a second-stage acid leaching solution with a vanadium concentration of 0.5~10g / L and a second-stage acid leaching residue with a vanadium content (mass percentage) of 0.5~1.0%. The high-acidity environment used in this stage can effectively destroy the insoluble calcium vanadate (Ca3(VO4)2) crystal structure in the first-stage acid leaching residue, and fully dissociate the residual vanadium through proton attack and coordination.

[0024] This invention proposes a stepped leaching method for calcified clinker. The first-stage leaching preferentially dissolves easily leached vanadium in a weakly acidic to neutral environment (pH 3.5~7.0), obtaining a high-concentration vanadium solution (30~50 g / L) while suppressing the co-dissolution of impurities such as iron, manganese, silicon, phosphorus, and lead, significantly reducing the subsequent purification load. The second-stage leaching, under strongly acidic conditions (pH≤1.5), specifically dissociates insoluble calcium vanadate, increasing the residual vanadium leaching rate by more than 30% through proton-induced crystal structure disruption. Ultimately, the total vanadium content in the slag is reduced to 0.5~1.0%, reducing vanadium loss by 40%~60% compared to traditional single-stage leaching processes, achieving maximum vanadium resource recovery and economic optimization of the leaching process.

[0025] In some embodiments, the first mother liquor is either clean water or a second-stage acid leaching solution obtained from the second-stage leaching. Using clean water ensures higher vanadium purity in the first-stage leaching solution, reduces impurity accumulation during circulation, and is suitable for scenarios requiring high vanadium product purity. Using the second-stage acid leaching solution as the first mother liquor fully utilizes its residual acidity and low vanadium concentration (0.5~10 g / L), reducing fresh acid consumption by 20%~30% and increasing the total vanadium recovery rate by 5%~8% through staged countercurrent circulation, while simultaneously reducing wastewater discharge, achieving dual optimization of resources and costs.

[0026] In some embodiments, the second mother liquor is water or a second-stage acid leaching solution obtained from the second-stage leaching. If water is used, complete decomposition of sparingly soluble calcium vanadate can be achieved under the high-acid (pH ≤ 1.5) conditions of the second stage, avoiding interference from impurity circulation and ensuring that the vanadium content in the final leaching residue remains consistently below 1.0%. However, when the second-stage acid leaching solution is recycled as the mother liquor, its residual free acid (H... + A concentration of 0.1~0.3mol / L can reduce the amount of fresh acid used by 30%~40%, and at the same time, the total water consumption of the system can be reduced by more than 15% through closed-loop circulation. While ensuring the vanadium leaching rate (>99%), it significantly reduces the cost of waste acid treatment, which meets the requirements of green hydrometallurgical process.

[0027] In some embodiments, the pH of the first and / or second leaching stages is adjusted by sulfuric acid, with a sulfuric acid concentration (mass percentage concentration) of 30%–98%. Preferably, in the first leaching stage, a sulfuric acid concentration of 30%–50% is used for adjustment. This concentration range allows for precise control of the weakly acidic to neutral environment to achieve selective vanadium leaching, while avoiding excessive acidity that would lead to the dissolution of large amounts of impurities such as iron, manganese, silicon, phosphorus, and lead. In the second leaching stage, a concentrated sulfuric acid concentration of 70%–98% is preferred for adjustment. The strong protonating ability of high-concentration sulfuric acid thoroughly destroys the crystal structure of calcium vanadate, while reducing the amount of liquid added to maintain a low liquid-to-solid ratio of 0.5–0.7:1. This efficiently recovers residual vanadium and reduces the cost of subsequent vanadium solution precipitation (in the vanadium solution precipitation process, the lower the vanadium solution concentration, the lower the precipitation efficiency and the higher the cost).

[0028] In some embodiments, during the first-stage leaching process, the reaction temperature is 45-70°C, and the leaching time is 60-90 minutes. The reaction temperature is determined by the exothermic reaction between the calcined roasted clinker and sulfuric acid, requiring no additional heating. The larger the amount of clinker, the higher the exothermic temperature, with the reaction temperature remaining approximately 45-70°C. If the first-stage leaching temperature is too low (e.g., below 40°C), insufficient thermodynamic conditions will occur; if the temperature is too high (above 70°C), vanadium in the leached liquid will precipitate. Furthermore, because the vanadium content of the calcined roasted clinker in the first-stage leaching is relatively high (approximately 6-9%), and the amount of clinker is large (e.g., above 8000 kg), the leaching time is relatively long, 60-90 minutes. The aforementioned reaction temperature range and leaching time range effectively balance leaching efficiency and energy consumption costs, helping to ensure leaching effectiveness while also considering the economic efficiency and operability of the process.

[0029] In some embodiments, during the second-stage leaching process, the reaction temperature is 40-60°C, and the leaching time is 30-60 minutes. The reaction temperature is determined by the spontaneous exothermic reaction between the first-stage acid leaching residue and sulfuric acid, requiring no additional heating. The larger the first-stage acid leaching residue, the higher the exothermic temperature, with a reaction temperature of approximately 40-60°C. If the second-stage leaching temperature is too low (e.g., below 40°C), insufficient thermodynamic conditions will occur; if the temperature is too high (above 70°C), vanadium precipitation will occur in the leached liquid. Furthermore, since the vanadium content of the first-stage acid leaching residue is 1.5-2.5%, the amount of second-stage acid leaching residue obtained during the second-stage leaching process is achieved by combining the first-stage acid leaching residue from two tanks and adding it to the second mother liquor for the second-stage leaching. The leaching time is relatively short, 30-60 minutes. The above-mentioned reaction temperature range and leaching time range effectively enhance the deep extraction and enrichment of vanadium, achieving a balance between process efficiency and product quality.

[0030] In some embodiments, the liquid-to-solid ratio of the first mother liquor from the first stage leaching to the calcified roasted clinker is 2.0~2.3L:1kg. For example, at 18m... 3 With the mother liquor volume remaining constant, the amount of calcified roasted clinker should be controlled at over 8000 kg, not exceeding the total capacity of the leaching tank, ensuring no overflow. This ratio optimizes the mass transfer efficiency and reaction environment of the leaching system, providing sufficient liquid medium to promote the efficient dissolution of vanadium from the calcified clinker while avoiding increased energy consumption in subsequent vanadium solution precipitation processes.

[0031] In some embodiments, the liquid-to-solid ratio of the first-stage acid leaching residue to the second mother liquor in the second-stage leaching is 0.5~0.6L:1kg. For example, in a 9m... 3 With the mother liquor volume remaining constant, the first-stage acid leaching residue should be controlled at over 16,000 kg, not exceeding the total capacity of the leaching tank, ensuring no overflow. This ratio effectively improves the secondary leaching efficiency of vanadium and optimizes process economy, ensuring full vanadium recovery and efficient utilization of the leaching agent, achieving dual optimization of resource recovery and production costs.

[0032] In some embodiments, the first-stage leaching is carried out under continuous stirring conditions, with the laboratory rotation speed controlled at 100-300 rpm and the actual rotation speed controlled at 80-100 rpm. The fluid state is vortex-shaped, which can significantly enhance mass transfer efficiency and optimize leaching kinetics. It can effectively prevent the sedimentation or agglomeration of calcified clinker particles, ensure sufficient contact between the solid and liquid phases, and increase the vanadium leaching rate. At the same time, the uniform mixing environment can avoid local pH fluctuations and reduce the selective dissolution of impurities such as iron, manganese, silicon, phosphorus, and lead caused by uneven acidity. This shortens the leaching time and ensures that the vanadium concentration of the first-stage acid leaching solution reaches a stable high purity of 30-50 g / L.

[0033] The present invention relates to the modification of on-site equipment, and the method flow diagram involving the equipment is shown in the figure. Figure 2 The following description, in conjunction with specific embodiments, further illustrates the detailed implementation of the present invention, but does not limit the invention to the scope of these embodiments.

[0034] Example 1 First-stage leaching: 8200 kg of calcified roasted clinker (TV content of 7.98%) was added to 18 m³ of the first mother liquor (clean water) and mixed in a 30 m³ leaching tank. 40% sulfuric acid was added uniformly over 10 min, initially adjusting the pH to 5.0. Stirring was started (85 rpm), and sulfuric acid was dynamically replenished via online pH monitoring to stabilize the pH at 5.0 ± 0.2. The reaction temperature was controlled at 60 ± 5℃. After leaching for 70 min, the slurry was filtered and washed in a buffer tank to obtain a first-stage acid leaching solution with a vanadium concentration of 37.34 g / L (Fe < 0.03 g / L, P < 0.035 g / L, Pb < 0.005 g / L) and a first-stage acid leaching residue with a vanadium content of 1.95%.

[0035] Second-stage leaching: 16,400 kg of the first-stage acid leaching residue (generally, two tanks of first-stage acid leaching residue are combined as the vanadium raw material for the second-stage leaching) is added to a 9 m³ second mother liquor (clean water) and mixed in a 30 m³ leaching tank. The pH is rapidly adjusted to 1.0 within 10 minutes using 98% sulfuric acid, and the mixture is stirred (at 85 rpm) for 50 minutes until the pH stabilizes at 1.2 ± 0.1. The reaction temperature is 45 ± 5℃. After filtration, a second-stage acid leaching solution with a vanadium concentration of 3.13 g / L and a second-stage acid leaching residue with a vanadium content of 0.79% are obtained, with a total vanadium leaching rate of 99.90%.

[0036] Example 2 8000 kg of calcified roasted clinker (TV content of 8.68%) was added to 18 m³ of the first mother liquor (the circulating liquid of the second-stage acid leaching solution, containing 8 g / L of vanadium) and mixed in a 30 m³ leaching tank. 50% sulfuric acid was added uniformly over 10 min, initially adjusting the pH to 6.0. After stirring (stirring speed 85 rpm), the pH was dynamically adjusted to 4.5 ± 0.2. The reaction temperature was 65 ± 5℃, and after leaching for 80 min, the solution was filtered and washed in a buffer tank to obtain a first-stage acid leaching solution with a vanadium concentration of 41.69 g / L (Fe < 0.08 g / L, P < 0.025 g / L, Pb < 0.003 g / L) and a first-stage acid leaching residue with a vanadium content of 1.55%.

[0037] Second-stage leaching: 16,000 kg of the first-stage acid leaching residue was added to a 9 m³ second mother liquor (clean water) and mixed in a 30 m³ leaching tank. The pH was rapidly adjusted to 0.8 using 98% sulfuric acid within 10 min, and the mixture was stirred (at 85 rpm) for 40 min until the pH stabilized at 1.0 ± 0.1. The reaction temperature was 50 ± 5 °C. After filtration, a second-stage acid leaching solution with a vanadium concentration of 7.68 g / L and a second-stage acid leaching residue with a vanadium content of 0.73% were obtained, resulting in a total vanadium leaching rate of 99.92%.

[0038] Example 3 First-stage leaching: 8500 kg of calcified roasted clinker (TV content of 9.98%) was added to 18 m³ of the first mother liquor (clean water) and mixed in a 30 m³ leaching tank. 40% sulfuric acid was added in stages: the initial pH was adjusted to 5.5, and the pH was dynamically adjusted to 6.0 ± 0.1 after starting variable frequency stirring (stirring speed 80~100 rpm). The reaction temperature was 50 ± 5℃, and after leaching for 90 min, a first-stage acid leaching solution with a vanadium concentration of 48.89 g / L (Fe < 0.05 g / L, P < 0.020 g / L, Pb < 0.001 g / L) and a first-stage acid leaching residue with a vanadium content of 2.32% were obtained.

[0039] Second-stage leaching: 17,000 kg of first-stage acid leaching residue was added to a 9 m³ second mother liquor (tailwater from the first-stage acid leaching solution, containing 1.2 g / L vanadium) and mixed in a 30 m³ leaching tank. The pH was adjusted to 0.5 using 70% sulfuric acid within 10 min, and stirring was intensified (stirring speed 85 rpm) for 60 min until the pH stabilized at 0.6 ± 0.1. The reaction temperature was 55 ± 5 °C. The final product was a second-stage acid leaching solution with a vanadium concentration of 1.15 g / L (circulated back to the first stage) and second-stage acid leaching residue with a vanadium content of 0.56%, achieving a total vanadium leaching rate of 99.94%.

[0040] Please refer to Table 1 for specific values.

[0041] Table 1:

[0042] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for cascade leaching of calcified clinker, characterized in that, Includes the following steps: First-stage leaching: The first mother liquor and calcined clinker are leached at a liquid-to-solid ratio of 1.5~2.5L:1kg under pH 3.5~7.0 conditions to obtain the first-stage acid leaching solution and the first-stage acid leaching residue; Second-stage leaching: The first-stage acid leaching residue and the second mother liquor are mixed at a liquid-to-solid ratio of 0.5~0.7L:1kg, and leached under pH≤1.5 conditions to obtain the second-stage acid leaching solution and the second-stage acid leaching residue.

2. The method for graded leaching of calcified clinker according to claim 1, characterized in that, The first mother liquor is either water or the second-stage acid leaching solution obtained from the second-stage leaching.

3. The method for graded leaching of calcified clinker according to claim 1, characterized in that, The second mother liquor is either water or the second-stage acid leaching solution obtained from the second-stage leaching.

4. The method for graded leaching of calcified clinker according to claim 1, characterized in that, The pH of the first-stage leaching and / or the second-stage leaching is adjusted by sulfuric acid, the concentration of which is 30% to 98%.

5. The method for graded leaching of calcified clinker according to claim 1, characterized in that, During the first stage of leaching, the reaction temperature is 45~70℃ and the leaching time is 60~90min.

6. The method for graded leaching of calcified clinker according to claim 1, characterized in that, In the second-stage leaching process, the reaction temperature is 40~60℃ and the leaching time is 30~60min.

7. The method for graded leaching of calcified clinker according to claim 1, characterized in that, The liquid-to-solid ratio of the first mother liquor leached from the first stage to the calcified roasted clinker is 2.0~2.3L:1kg.

8. The method for graded leaching of calcified clinker according to claim 1, characterized in that, The liquid-to-solid ratio of the first-stage acid leaching residue to the second mother liquor in the second-stage leaching is 0.5L~0.6:1kg.

9. The method for graded leaching of calcified clinker according to claim 1, characterized in that, The first stage of leaching is carried out under continuous stirring conditions.

10. The method for graded leaching of calcified clinker according to any one of claims 1 to 9, characterized in that, The vanadium concentration in the first-stage acid leaching solution is 30~50 g / L, and the vanadium content in the first-stage acid leaching residue is 1.5~2.5%; the vanadium concentration in the second-stage acid leaching solution is 0.5~10 g / L; and the vanadium content in the second-stage acid leaching residue is 0.5~1.0%.

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