A method for solidifying calcium-magnesium impurities in titanium metallurgical molten salt slag by using a solidifying agent

Abstract

The present application belongs to the technical field of titanium metallurgy solid waste utilization, and particularly relates to a method for solidifying calcium-magnesium impurities in titanium metallurgy molten salt slag by using a solidifying agent. The present application takes titanium metallurgy molten salt chlorination waste salt slag as raw material, and uses high-temperature phase conversion method of sodium sulfate or sodium silicate to promote liquid-solid phase transition of calcium-magnesium impurities in the waste salt. The high melting point and high density characteristics of calcium-magnesium impurities are used to carry out precipitation, clarification and separation with low melting point NaCl melt, so as to realize solid-liquid separation of calcium-magnesium impurities and NaCl melt. Specifically, calcium-magnesium impurities react with the solidifying agent to generate calcium-magnesium impurities with high melting point and high density. These calcium-magnesium impurity phases undergo nucleation, growth and precipitation processes, and finally realize the separation of calcium-magnesium impurities and NaCl molten salt, so as to obtain recyclable NaCl molten salt. The calcium-magnesium impurity tailings obtained after separation are treated by water dissolution-hydrolysis, the obtained NaCl solution enters the chlor-alkali process, and the calcium-magnesium impurities are used as roadbed materials.

Description

Technical Field

[0001] This invention belongs to the field of titanium metallurgical solid waste utilization technology, specifically relating to a method for solidifying calcium and magnesium impurities in titanium metallurgical molten salt slag using a solidifying agent. Background Technology

[0002] Currently, most sponge titanium and chloride-process titanium dioxide production enterprises use domestically sourced high-calcium, magnesium, and titanium resources as raw materials, producing TiCl4 via molten salt chlorination. Molten salt chlorination has relatively low requirements for furnace charge and is well-suited to the characteristics of my country's high-calcium, magnesium, and titanium resources. However, this method has a significant drawback: it generates a large amount of molten salt chlorination waste slag. With current technology, approximately 11.7 kt of waste salt is emitted for every 10 kt of titanium tetrachloride produced.

[0003] During molten salt chlorination, calcium and magnesium impurities in the raw materials generate substances such as calcium chloride and magnesium chloride. These impurities accumulate in the brine, not only deteriorating the physicochemical properties of the molten salt but also severely disrupting the chlorination reaction conditions within the furnace, thus significantly impacting the production efficiency of molten salt chlorination. The composition of molten salt chlorination waste slag is extremely complex, with NaCl as the main molten salt phase, along with various chlorides, unreacted oxides, and coke. Chlorides such as CaCl2 and MgCl2 are mixed with NaCl, making recycling and treatment extremely difficult. Directly dumping or landfilling this waste slag would cause serious pollution to groundwater and soil, among other ecological environments.

[0004] Currently, the main methods for treating molten salt chlorination waste salt residue are deep burial and lime neutralization followed by stockpiling. However, these methods cannot fundamentally solve the environmental pollution problem. Although water-soluble treatment can selectively recover certain substances from the filtrate, it also has many problems, such as large amounts of wastewater generated after treatment, difficulty in removing impurities, cumbersome and complex process flow, and a lack of effective treatment methods for the resulting filter residue.

[0005] Therefore, there is an urgent need to develop a method that can effectively solidify calcium and magnesium impurities in titanium metallurgical molten salt slag, so as to realize the resource utilization of calcium and magnesium impurities in titanium metallurgical molten salt slag, fundamentally solve the environmental pollution problem caused by waste salt slag, and improve the comprehensive utilization rate of resources.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for solidifying calcium and magnesium impurities in titanium metallurgical molten salt slag using a solidifying agent. This method employs a high-temperature phase transformation method to solidify calcium and magnesium impurities in titanium metallurgical molten salt slag, effectively avoiding problems such as the generation of large amounts of wastewater after impurity removal, environmental pollution from the process, and low resource utilization. This method can achieve the overall recycling of molten salt chlorination waste slag at high temperatures.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for curing calcium and magnesium impurities in titanium metallurgical molten salt slag using a curing agent, the specific steps of which are as follows:

[0010] Step 1: After the waste salt slag from the molten salt chlorination furnace is discharged, it is kept at 420-700℃ and subjected to the first solid-liquid separation to obtain the first filter residue and the first filtrate; the first filter residue is Ti residue and carbon powder, and the first filtrate is a mixed melt including NaCl, MgCl2, CaCl2, FeCl2, FeCl3, MnCl2, AlCl3, and TiCl4;

[0011] Step 2: The first filter residue is returned to the molten salt chlorination furnace to continue the reaction, and the first filtrate is sent to a high-temperature reaction furnace preheated to 420-700℃;

[0012] Step 3: First, add a specific amount of curing agent to the high-temperature reactor, then raise the temperature of the high-temperature reactor to 600-830℃ at a rate of 5-25℃ / min and hold for 0.1-2 hours to obtain solution A; during the heating process, compressed air at a pressure of 0.01MPa-1.5MPa needs to be introduced into the first filtrate to allow volatile components such as manganese chloride, ferrous chloride, aluminum chloride, silicon tetrachloride, and titanium tetrachloride in the first filtrate to fully volatilize; the curing agent is sodium sulfate or sodium silicate;

[0013] Step 4: Heat the solution A to 835-1100℃ at a rate of 5-25℃ / min and hold for 0.2-4 hours to obtain a solid-liquid mixture B. During the holding process, the curing agent reacts fully with calcium chloride and magnesium chloride in solution A to generate high-melting-point calcium sulfate and magnesium sulfate, or calcium silicate and magnesium silicate. After the calcium sulfate and magnesium sulfate, or calcium silicate and magnesium silicate crystals have grown sufficiently, they are fully separated from the NaCl melt and form a precipitate.

[0014] Step 5: After the solid-liquid mixture B undergoes a second solid-liquid separation, a second filtrate and a second filter residue are obtained; the second filtrate is NaCl melt, and the second filter residue is sodium chloride salt residue containing calcium sulfate and magnesium sulfate; or sodium chloride salt residue containing calcium silicate and magnesium silicate;

[0015] Step 6: The second filtrate is sent to a molten salt chlorination furnace for further reaction; at the same time, the second filter residue is cooled (slowly cooled to 98°C or below), and then subjected to water dissolution-hydrolysis-static settling-clarification treatment before a third solid-liquid separation to obtain a salt solution and a third filter residue, thereby completing the solidification of calcium and magnesium impurities in titanium metallurgical molten salt slag; the salt solution is NaCl solution, and the third filter residue is calcium sulfate and magnesium sulfate precipitate; or calcium silicate and magnesium silicate precipitate, and the third filter residue is used as a roadbed paving material.

[0016] Specifically, in step 1, the first solid-liquid separation method is one of pressure filtration, vacuum filtration or centrifugal filtration, and the medium for the first solid-liquid separation is a porous high-temperature ceramic with a mesh density of 10ppi-600ppi.

[0017] Specifically, in step 3, the specific calculation process for the specific amount of curing agent is as follows: first, sample and analyze the salt solution in the molten salt chlorination furnace (or analyze a sample from the previous batch of salt slag), and then, based on the Ca content in the sample... 2+ Mg 2+ Given the ion mass percentages X (%) and Y (%), calculate the amount of curing agent W added in the high-temperature conversion process. The specific calculation formula is as follows:

[0018]

[0019] Wherein, 1.05 is the excess coefficient of curing agent; 1000 is the calculation base for the mass of salt slag to be converted, which is 1000 kg; β is the molar mass of curing agent, in g / mol; 40 is the molar mass of calcium ions, in g / mol; 24.3 is the molar mass of magnesium ions, in g / mol; X is the mass percentage of calcium ions in the salt slag to be converted; Y is the mass percentage of magnesium ions in the salt slag to be converted; and M is the mass of salt slag to be converted, in kg.

[0020] Specifically, in step 5, the second solid-liquid separation method is one of pressure filtration, vacuum filtration or centrifugal filtration, and the medium for the second solid-liquid separation is a porous high-temperature ceramic with a mesh density of 10ppi-600ppi.

[0021] Specifically, in step 6, a plate and frame filter press is used for the third solid-liquid separation.

[0022] In addition, the main chemical reactions involved in this invention are as follows:

[0023] CaCl₂ + Na₂SO₄ = 2NaCl + CaSO₄

[0024] MgCl₂ + Na₂SO₄ = 2NaCl + MgSO₄

[0025] CaCl₂ + Na₂SiO₃ = 2NaCl + CaSiO₃

[0026] MgCl₂ + Na₂SiO₃ = 2NaCl + MgSiO₃

[0027]

[0028] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0029] This invention uses titanium metallurgical molten salt chlorination waste salt slag as raw material and employs a high-temperature phase transformation method using sodium sulfate or sodium silicate to induce a liquid-solid phase transition in the waste salt. Taking advantage of the high melting point and high density of the calcium and magnesium impurities, they are precipitated, clarified, and separated from the low-melting-point NaCl melt, achieving solid-liquid separation of the calcium and magnesium impurities from the NaCl melt.

[0030] Specifically, this invention involves reacting calcium and magnesium impurities with a curing agent to generate high-melting-point, high-density calcium and magnesium impurities. These calcium and magnesium impurity phases undergo nucleation, growth, and precipitation processes to ultimately separate the calcium and magnesium impurities from the NaCl molten salt, obtaining recyclable NaCl molten salt. This molten salt can be recycled into the molten salt chlorination process. The calcium and magnesium impurity tailings obtained after separation are treated with water dissolution and hydrolysis. The resulting water-soluble NaCl solution can be used in the chlor-alkali process, while the calcium and magnesium impurities are used as roadbed materials.

[0031] In summary, this invention achieves the resource utilization of calcium and magnesium impurities in titanium metallurgical molten salt slag, completely solving the serious pollution problem of waste salt slag to groundwater and soil. The high-temperature conversion treatment of molten salt chlorination waste slag using an electrothermal metallurgical method, followed by water-soluble-hydrolysis treatment of the conversion tailings, results in high production efficiency. This method not only achieves the resource utilization and harmless treatment of molten salt chlorination waste slag but also significantly reduces the costs of continuously replenishing new salt and disposing of waste salt in the molten salt chlorination process, demonstrating good economic benefits. Attached Figure Description

[0032] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0033] 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, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a process flow diagram of the method for curing calcium and magnesium impurities in titanium metallurgical molten salt slag using a curing agent according to the present invention.

[0035] Figure 2 This is a schematic diagram of the curing process of the method of curing calcium and magnesium impurities in titanium metallurgical molten salt slag using a curing agent according to the present invention. Detailed Implementation

[0036] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0037] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] See Figure 1 and 2 As shown in the figure, this embodiment provides a method for solidifying calcium and magnesium impurities in titanium metallurgical molten salt slag using sodium sulfate. The specific steps are as follows:

[0040] Step 1: After the waste salt slag from the molten salt chlorination furnace is discharged, it is kept at 420℃. At the same time, pressure filtration is used to perform the first solid-liquid separation on a 10ppi porous high-temperature ceramic to obtain unreacted Ti residue and carbon powder, which are returned to the molten salt chlorination furnace. The first filtrate is then transported to a high-temperature reactor preheated to 420℃.

[0041] Step 2: Add sodium sulfate to the high-temperature reactor. The amount added depends on the Ca content in the sample. 2+ Mg 2+ The ion mass percentages X (%) and Y (%), and the amount of anhydrous sodium sulfate added W are:

[0042]

[0043] Wherein, 1.05 is the excess coefficient of sodium sulfate; 1000 is the base for calculating the mass of the salt residue to be converted, which is 1000 kg; 142 is the molar mass of sodium sulfate, in g / mol; 40 is the molar mass of calcium ions, in g / mol; 24.3 is the molar mass of magnesium ions, in g / mol; X is the mass percentage of calcium ions in the salt residue to be converted; Y is the mass percentage of magnesium ions in the salt residue to be converted; and M is the mass of the salt residue to be converted, in kg.

[0044] The first filtrate was heated to 830℃ and held for 0.1h. Compressed air was introduced into the brine during the heating process to allow volatile components such as manganese chloride, ferrous chloride, aluminum chloride, silicon tetrachloride, and titanium tetrachloride in the brine to fully volatilize, and then solution A was obtained.

[0045] Step 3: Continue heating solution A to 835℃ and keep it at that temperature for 4 hours. Allow sodium sulfate to react fully with calcium chloride and magnesium chloride to generate high-melting-point calcium sulfate and magnesium sulfate, and allow the crystals of calcium sulfate and magnesium sulfate to grow fully, so that they can be fully separated from the sodium chloride solution and form a precipitate, thus obtaining a solid-liquid mixture B.

[0046] Step 4: The solid-liquid mixture B is subjected to a second solid-liquid separation by pressure filtration on a 10ppi porous high-temperature ceramic to obtain molten salt mainly composed of NaCl and a second filter residue. The molten salt is then recycled into the molten salt chlorination process.

[0047] Step 5: First, let the second filter residue cool slowly to below 98°C. Then, after water dissolution-hydrolysis-static-clarification treatment, it is separated into solid and liquid for the third time through a plate and frame filter press to obtain a filtration aqueous solution and a third filter residue. The filtration aqueous solution is mainly NaCl solution. After deep purification, the NaCl solution is sent to the chlor-alkali process as a solution salt. The third filter residue is calcium sulfate and magnesium sulfate precipitate, which can be used as roadbed paving material.

[0048] After deep purification, the NaCl solution is sent to the chlor-alkali process as a saline solution. The main reaction is as follows:

[0049]

[0050] In Example 1, by testing, the NaCl recovery rate in the solidified titanium metallurgical molten salt slag using this method reached 81%.

[0051] Example 2

[0052] See Figure 1 and 2 As shown in the figure, this embodiment provides a method for solidifying calcium and magnesium impurities in titanium metallurgical molten salt slag using sodium sulfate. The specific steps are as follows:

[0053] Step 1: After the waste salt slag from the molten salt chlorination furnace is discharged, it is kept at 700℃. At the same time, the first solid-liquid separation is carried out by vacuum filtration under 600ppi porous high-temperature ceramic. The unreacted Ti residue and carbon powder are returned to the molten salt chlorination furnace. The first filtrate is then transported to a high-temperature reactor preheated to 700℃.

[0054] Step 2: Add sodium sulfate to the high-temperature reactor. The amount added depends on the Ca content in the sample. 2+ Mg 2+ The ion mass percentages X (%) and Y (%), and the amount of anhydrous sodium sulfate added W are:

[0055]

[0056] Wherein, 1.05 is the excess coefficient of sodium sulfate; 1000 is the base for calculating the mass of the salt residue to be converted, which is 1000 kg; 142 is the molar mass of sodium sulfate, in g / mol; 40 is the molar mass of calcium ions, in g / mol; 24.3 is the molar mass of magnesium ions, in g / mol; X is the mass percentage of calcium ions in the salt residue to be converted; Y is the mass percentage of magnesium ions in the salt residue to be converted; and M is the mass of the salt residue to be converted, in kg.

[0057] The first filtrate was heated to 600℃ and kept at that temperature for 2 hours. During the heating process, compressed air was introduced into the brine to allow the volatile components such as manganese chloride, ferrous chloride, aluminum chloride, silicon tetrachloride, and titanium tetrachloride in the brine to fully volatilize, and then solution A was obtained.

[0058] Step 3: Continue heating solution A to 1100℃ and keep it at that temperature for 0.2h. Allow sodium sulfate to react fully with calcium chloride and magnesium chloride to generate high-melting-point calcium sulfate and magnesium sulfate, and allow the crystals of calcium sulfate and magnesium sulfate to grow fully, so that they can be fully separated from the sodium chloride solution and form a precipitate, thus obtaining a solid-liquid mixture B.

[0059] Step 4: The solid-liquid mixture B is subjected to a second solid-liquid separation by vacuum filtration on a 600ppi porous high-temperature ceramic to obtain the filtrate, which is molten salt mainly composed of NaCl and the second filter residue. At the same time, the molten salt is recycled into the molten salt chlorination process.

[0060] Step 5: First, let the second filter residue cool slowly to below 98°C. Then, after water dissolution-hydrolysis-static-clarification treatment, it is separated into solid and liquid for the third time through a plate and frame filter press to obtain a filtration aqueous solution and a third filter residue. The filtration aqueous solution is mainly NaCl solution. After deep purification, the NaCl solution is sent to the chlor-alkali process as a solution salt. The third filter residue is calcium sulfate and magnesium sulfate precipitate, which can be used as roadbed paving material.

[0061] After deep purification, the NaCl solution is sent to the chlor-alkali process as a saline solution. The main reaction is as follows:

[0062]

[0063] In Example 2, by testing, the recovery rate of NaCl in the solidified titanium metallurgical molten salt slag reached 86.7% using this method to solidify calcium and magnesium impurities.

[0064] Example 3

[0065] See Figure 1 and 2 As shown in the figure, this embodiment provides a method for solidifying calcium and magnesium impurities in titanium metallurgical molten salt slag using sodium sulfate. The specific steps are as follows:

[0066] Step 1: After the waste salt slag from the molten salt chlorination furnace is discharged, it is kept at 550℃. At the same time, the first solid-liquid separation is carried out by centrifugal filtration on a 300ppi porous high-temperature ceramic. The unreacted Ti residue and carbon powder are returned to the molten salt chlorination furnace, and the first filtrate is transported to a high-temperature reactor preheated to 550℃.

[0067] Step 2: Add sodium sulfate to the high-temperature reactor. The amount added depends on the Ca content in the sample. 2+ Mg 2+ The ion mass percentages X (%) and Y (%), and the amount of anhydrous sodium sulfate added W are:

[0068]

[0069] Wherein, 1.05 is the excess coefficient of sodium sulfate; 1000 is the base for calculating the mass of the salt residue to be converted, which is 1000 kg; 142 is the molar mass of sodium sulfate, in g / mol; 40 is the molar mass of calcium ions, in g / mol; 24.3 is the molar mass of magnesium ions, in g / mol; X is the mass percentage of calcium ions in the salt residue to be converted; Y is the mass percentage of magnesium ions in the salt residue to be converted; and M is the mass of the salt residue to be converted, in kg.

[0070] The first filtrate was heated to 710℃ and kept at that temperature for 1 hour. During the heating process, compressed air was introduced into the brine to allow the volatile components such as manganese chloride, ferrous chloride, aluminum chloride, silicon tetrachloride, and titanium tetrachloride in the brine to fully volatilize, and then solution A was obtained.

[0071] Step 3: Continue heating solution A to 950℃ and keep it at that temperature for 2 hours. Allow sodium sulfate to react fully with calcium chloride and magnesium chloride to generate high-melting-point calcium sulfate and magnesium sulfate, and allow the calcium sulfate and magnesium sulfate crystals to grow fully, so that they can be fully separated from the sodium chloride solution and form a precipitate, thus obtaining a solid-liquid mixture B.

[0072] Step 4: The solid-liquid mixture B is centrifuged and filtered in a 300ppi porous high-temperature ceramic to obtain molten salt mainly composed of NaCl and a second filter residue. The molten salt is then recycled into the molten salt chlorination process.

[0073] Step 5: First, let the second filter residue cool slowly to below 98°C. Then, after water dissolution-hydrolysis-static-clarification treatment, it is separated into solid and liquid for the third time through a plate and frame filter press to obtain a filtration aqueous solution and a third filter residue. The filtration aqueous solution is mainly NaCl solution. After deep purification, the NaCl solution is sent to the chlor-alkali process as a solution salt. The third filter residue is calcium sulfate and magnesium sulfate precipitate, which can be used as roadbed paving material.

[0074] After deep purification, the NaCl solution is sent to the chlor-alkali process as a saline solution. The main reaction is as follows:

[0075]

[0076] In Example 3, the detection showed that the NaCl recovery rate in the solidified titanium metallurgical molten salt slag using this method reached 84.9% for calcium and magnesium impurities.

[0077] Example 4

[0078] See Figure 1 and 2 As shown in the figure, this embodiment provides a method for solidifying calcium and magnesium impurities in titanium metallurgical molten salt slag using sodium silicate. The specific steps are as follows:

[0079] Step 1: After the waste salt slag from the molten salt chlorination furnace is discharged, it is kept at 700℃. At the same time, the first solid-liquid separation is carried out by vacuum filtration under 600ppi porous high-temperature ceramic. The unreacted Ti residue and carbon powder are returned to the molten salt chlorination furnace. The first filtrate is then transported to a high-temperature reactor preheated to 700℃.

[0080] Step 2: Add sodium silicate to the high-temperature reactor. The amount added depends on the Ca content in the sample. 2+ Mg 2+ The ion mass percentages X (%) and Y (%), and the amount of sodium silicate added W are:

[0081]

[0082] Wherein, 1.05 is the excess coefficient of sodium silicate; 1000 is the base for calculating the mass of the salt residue to be converted, which is 1000 kg; 122 is the molar mass of sodium silicate, in g / mol; 40 is the molar mass of calcium ions, in g / mol; 24.3 is the molar mass of magnesium ions, in g / mol; X is the mass percentage of calcium ions in the salt residue to be converted; Y is the mass percentage of magnesium ions in the salt residue to be converted; and M is the mass of the salt residue to be converted, in kg.

[0083] The first filtrate was heated to 830℃ and kept at that temperature for 0.3h. During the heating process, compressed air was introduced into the brine to allow the volatile components such as manganese chloride, ferrous chloride, aluminum chloride, silicon tetrachloride, and titanium tetrachloride in the brine to fully volatilize, and then solution A was obtained.

[0084] Step 3: Continue heating solution A to 1000℃ and keep it at that temperature for 0.2h. Allow sodium silicate to react fully with calcium chloride and magnesium chloride to generate high-melting-point calcium silicate and magnesium silicate, and allow the crystals of calcium silicate and magnesium silicate to grow fully, so that they can be fully separated from the sodium chloride solution and form a precipitate, thus obtaining a solid-liquid mixture B.

[0085] Step 4: The solid-liquid mixture B is subjected to a second solid-liquid separation by vacuum filtration on a 600ppi porous high-temperature ceramic to obtain the filtrate, which is molten salt mainly composed of NaCl and the second filter residue. At the same time, the molten salt is recycled into the molten salt chlorination process.

[0086] Step 5: First, the second filter residue is slowly cooled to below 98°C. Then, after water dissolution-hydrolysis-static settling-clarification treatment, it is subjected to a third solid-liquid separation through a plate and frame filter press to obtain a filtration aqueous solution and a third filter residue. The filtration aqueous solution is mainly NaCl solution. After deep purification, the NaCl solution is sent to the chlor-alkali process as a solution salt. The third filter residue is calcium silicate and magnesium silicate precipitate, which can be used as roadbed paving material.

[0087] After deep purification, the NaCl solution is sent to the chlor-alkali process as a saline solution. The main reaction is as follows:

[0088]

[0089] In Example 4, by testing, the recovery rate of NaCl in the solidified titanium metallurgical molten salt slag reached 82.5% using this method to solidify calcium and magnesium impurities.

[0090] In summary, the method of solidifying calcium and magnesium impurities in titanium metallurgical molten salt slag using sodium sulfate or sodium silicate can achieve a NaCl recovery rate of over 80% in the waste salt slag. The resulting calcium and magnesium waste slag can be used as roadbed paving material, improving resource utilization and reducing environmental pollution.

[0091] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0092] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for solidifying calcium and magnesium impurities of a titanium metallurgical molten salt slag with a solidifying agent, characterized in that, The specific steps are as follows: Step 1, after the waste salt slag of the molten salt chlorination furnace is discharged, it is kept at 420-700℃ and subjected to first solid-liquid separation to obtain first filter residue and first filter liquor; the first solid-liquid separation is one of pressurized filtration, vacuum filtration or centrifugal separation, and the medium of the first solid-liquid separation is porous high-temperature ceramic with mesh density of 10-600 ppi; Step 2, the first filter residue is returned to the molten salt chlorination furnace for continuous reaction, and the first filter liquor is sent to a preheated high-temperature reaction furnace; Step 3, a specific amount of solidifying agent is added to the high-temperature reaction furnace, and then the high-temperature reaction furnace is heated to 600-830℃ and kept for 0.1-2h to obtain solution A; compressed air is also introduced into the first filter liquor during the heating process; the solidifying agent is sodium sulfate or sodium silicate; The specific amount of solidifying agent is calculated as follows: first, sample and analyze the salt solution in the molten salt chlorination furnace, then calculate the addition amount W of the solidifying agent in the high-temperature conversion process according to the mass percentage X and Y of Ca 2+ , Mg 2+ ions in the sample, and the calculation formula is as follows: Formula 1 wherein 1.05 is the excess coefficient of the solidifying agent; 1000 is the mass calculation basis of the salt slag to be converted, which is 1000 kg; β is the molar mass of the solidifying agent, unit: g / mol; 40 is the molar mass of calcium ions, unit: g / mol; 24.3 is the molar mass of magnesium ions, unit: g / mol; X is the mass percentage content of calcium ions in the salt slag to be converted; Y is the mass percentage content of magnesium ions in the salt slag to be converted; M is the mass of the salt slag to be converted, unit: kg; Step 4, the solution A is heated to 835-1100℃ and kept for 0.2-4h to obtain solid-liquid mixture B; Step 5, after the solid-liquid mixture B is subjected to second solid-liquid separation, second filter liquor and second filter residue are obtained; Step 6, the second filter liquor is sent to the molten salt chlorination furnace for continuous reaction; at the same time, the second filter residue is cooled, and then subjected to water-soluble-hydrolysis-resting-clearing treatment and then third solid-liquid separation to obtain salt solution and third filter residue, so as to complete the solidification of calcium and magnesium impurities in the titanium metallurgical molten salt slag.

2. The method for solidifying calcium and magnesium impurities of titanium metallurgical molten salt slag by using solidifying agent according to claim 1, characterized in that, In step 2, the preheating temperature of the high-temperature reaction furnace is 420-700℃.

3. The method for solidifying the calcium and magnesium impurities of the titanium metallurgical molten salt slag by using a solidifying agent according to claim 1, characterized in that, In step 3, the heating rate of the first filter liquor is 5-25℃ / min.

4. The method for solidifying the calcium and magnesium impurities of the titanium metallurgical molten salt slag by using a solidifying agent according to claim 1, characterized in that, In step 3, the pressure of the compressed air is 0.01-1.5 MPa.

5. The method for solidifying the calcium and magnesium impurities of the titanium metallurgical molten salt slag by using a solidifying agent according to claim 1, characterized in that, In step 4, the heating rate of the solution A is 5-25℃ / min.

6. The method for solidifying the calcium and magnesium impurities of the titanium metallurgical molten salt slag by using a solidifying agent according to claim 1, characterized in that, In step 5, the second solid-liquid separation is one of pressurized filtration, vacuum filtration or centrifugal separation, and the medium of the second solid-liquid separation is porous high-temperature ceramic with mesh density of 10-600 ppi.

7. The method for solidifying the calcium and magnesium impurities of the titanium metallurgical molten salt slag by using a solidifying agent according to claim 1, characterized in that, In step 6, the third solid-liquid separation is carried out by using a plate and frame filter press.

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