A molten salt chlorination solid waste treatment method

Abstract

The present application relates to molten salt chlorination solid waste treatment technical field, specifically to a kind of molten salt chlorination solid waste treatment method, comprising the following steps: S1, the chlorination waste molten salt in molten salt furnace is discharged into intermediate tank under 700-800 ℃, and is carried out heat preservation treatment under the condition of micro-vacuum and into compressed air, until the chlorine ion content in tail gas is lower than preset value, it is first impurity removal;S2, then the waste molten salt after processing is high-temperature centrifugal separation, the waste molten salt obtained is further cooled and washed with saturated sodium chloride solution, to obtain sodium chloride crystal and metal chlorination liquid, it is second impurity removal;S3, finally, waste molten salt waste heat is used to dry and crush sodium chloride crystal and return molten salt furnace for use, and metal chlorination liquid needs to be neutralized, it is third impurity removal.The molten salt chlorination solid waste treatment method, by the unique process steps and equipment combination, realizes the efficient treatment and resource reutilization of waste molten salt, and remarkable technical effect is obtained.

Description

Technical Field

[0001] This invention relates to the field of molten salt chlorination solid waste treatment technology, and more specifically, to a method for treating molten salt chlorination solid waste. Background Technology

[0002] With the rapid development of industrialization, molten salt chlorination technology, as an important chemical production process, is widely used in the production of products such as titanium dioxide, sponge titanium, and titanium tetrachloride. However, this production process generates a large amount of waste molten salt, which contains unreacted raw materials, byproducts, and impurities. The treatment and utilization of this waste molten salt has always been a pressing issue for the industry.

[0003] Traditional methods for treating molten salt waste often suffer from low efficiency, significant resource waste, and substantial environmental pollution. For example, direct discharge or simple landfilling can cause severe environmental damage, while simple recycling cannot effectively remove harmful substances, leading to decreased product quality and increased environmental pollution risks. Therefore, developing an efficient and environmentally friendly method for treating molten salt chlorination solid waste is of paramount importance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for treating molten salt chlorination solid waste, addressing the problems of low treatment efficiency, severe resource waste, and significant environmental pollution often found in traditional molten salt treatment methods described in the background. For example, direct discharge or simple landfilling can cause serious environmental damage, while simple recycling cannot effectively remove harmful substances, leading to decreased product quality and increased environmental pollution risks.

[0005] To achieve the above objectives, the present invention provides a method for treating molten salt chlorination solid waste, comprising the following steps: S1. The chlorinated waste molten salt in the molten salt furnace is discharged into the intermediate tank at 700-800℃ and kept warm under micro-vacuum and compressed air conditions until the chloride ion content in the tail gas is lower than the preset value, which is the first impurity removal. S2. Next, the treated waste molten salt is centrifuged at high temperature. The obtained waste molten salt is further cooled and washed with saturated sodium chloride solution to obtain sodium chloride crystals and metal chloride liquid, which is the secondary impurity removal. S3. Finally, the residual heat of the waste molten salt is used to dry and crush the sodium chloride crystals before returning them to the molten salt furnace for use. The metal chloride liquid needs to be neutralized, which is a three-stage impurity removal process.

[0006] As a preferred embodiment of the present invention, in step S1, the process of maintaining a micro-vacuum state in the intermediate tank and introducing compressed air is achieved by controlling the negative pressure of the exhaust gas system, so as to keep the waste molten salt in a flowing state for heat preservation treatment, thereby effectively removing C, FeCl3, AlCl3 and a small amount of chlorine gas discharged with the waste molten salt.

[0007] As a preferred embodiment of the present invention, the heat preservation process involves simultaneously introducing compressed air to burn the unreacted petroleum coke while maintaining a negative pressure of 0.05-0.1 kPa and keeping the temperature between 700-800°C to prevent the molten salt from solidifying.

[0008] As a preferred embodiment of the present invention, in step S1, the preset value is that the chloride ion content in the tail gas is less than 1%, which is used to determine whether the first impurity removal is completed, ensuring that there are no boilable chloride residues in the waste molten salt, and the time range is 30±5 minutes.

[0009] As a preferred embodiment of the present invention, in step S2, the high-temperature centrifugal separation step utilizes the high fluidity of the melt to separate the unreacted titanium slag from the waste molten salt. The titanium ore is mainly composed of rutile, and after cooling, crushing and regranulation, it is sent to the fluidized bed furnace for use.

[0010] As a preferred embodiment of the present invention, in step S2, in the step of washing the waste molten salt with a saturated sodium chloride solution, other metal chlorides in the waste molten salt are dissolved in the solution by controlling the washing pressure, thereby obtaining pure sodium chloride crystals, and the sodium chloride crystals are dried using the residual heat of the waste molten salt and returned to the molten salt furnace for use.

[0011] In a preferred embodiment of the present invention, in step S2, the washing pressure is 0.1-0.3 MPa. After washing, the waste molten salt is crushed by water pressure, and white insoluble matter is visible in the mixture. The white insoluble matter and the filtrate are separated to obtain sodium chloride crystals and a metal chloride solution containing NaCl, FeCl2, CaCl2, MgCl2, and KCl.

[0012] As a preferred embodiment of the present invention, the metallic chloride solution generated after one washing with saturated sodium chloride needs to be neutralized to remove other metal ions and form a saturated sodium chloride solution for reuse, in order to prevent chloride ions from having a common ion effect and resulting in poor washing effect.

[0013] As a preferred embodiment of the present invention, in step S3, in the step of neutralizing the metal chloride solution, an appropriate neutralizing agent is added to precipitate the metal ions in the filtrate, and then the filtrate is separated and sent to the next washing section to realize the recycling of washing water and reduce water waste.

[0014] As a preferred embodiment of the present invention, a molten salt chlorination solid waste treatment system is included. The molten salt chlorination solid waste treatment system includes an intermediate tank, a centrifuge, a first slag box, a second slag box, washing equipment, and drying equipment. The centrifuge is a high-temperature centrifuge with a rotation speed of 2000 r / min, used to perform high-temperature centrifugal separation of the treated waste molten salt. The slag box is used to cool the centrifuged titanium slag. The fluidized bed furnace is used for fluidized bed chlorination of the crushed and regranulated material. The first slag box is used to store the titanium slag that has not fully reacted after high-temperature centrifugation, and the second slag box is used to store the waste molten salt after high-temperature centrifugal separation.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This method for treating molten salt chlorination solid waste achieves efficient treatment and resource reuse of waste molten salt through unique process steps and equipment combinations, resulting in significant technical benefits.

[0016] First, this method effectively removes harmful substances such as C, FeCl3, AlCl3, and a small amount of chlorine gas discharged with the waste molten salt through micro-vacuum insulation in the intermediate tank, thereby improving the purity of the waste molten salt. Simultaneously, the introduction of compressed air to burn unreacted petroleum coke further enhances processing efficiency. This step not only ensures the quality of the waste molten salt but also lays a solid foundation for subsequent processing and utilization.

[0017] Secondly, this method employs high-temperature centrifugal separation technology to effectively separate unreacted titanium slag from the molten salt waste. This step not only purifies the molten salt waste but also recovers valuable titanium slag resources, improving resource utilization. Simultaneously, washing the molten salt waste with a saturated sodium chloride solution further removes other metal chlorides, yielding pure sodium chloride crystals. This step not only improves product purity but also provides high-quality raw materials for subsequent applications.

[0018] Finally, this method utilizes the residual heat of the molten salt to dry and crush the sodium chloride crystals, which are then returned to the molten salt furnace for reuse, achieving efficient energy utilization and waste reduction. Simultaneously, the metal chloride solution is neutralized, removing harmful metal ions and creating a recyclable saturated sodium chloride solution, thus reducing the risk of environmental pollution. Attached Figure Description

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

[0020] The meanings of the labels in the diagram are as follows: 1. Intermediate tank; 2. Molten salt furnace; 3. Fluidized bed furnace; 4. Centrifuge; 5. First slag box; 6. Second slag box; 7. Washing equipment; 8. Drying equipment. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a method for treating solid waste from molten salt chlorination, such as... Figure 1 As shown, it includes the following steps: S1. The chlorinated waste molten salt in the molten salt furnace 2 is discharged into the intermediate tank 1 at 700-800℃ and kept warm under micro-vacuum and compressed air conditions until the chloride ion content in the tail gas is lower than the preset value, which is the first impurity removal. S2. Next, the treated waste molten salt is centrifuged at high temperature. The obtained waste molten salt is further cooled and washed with saturated sodium chloride solution to obtain sodium chloride crystals and metal chloride liquid, which is the secondary impurity removal. S3. Finally, the residual heat of the waste molten salt is used to dry and crush the sodium chloride crystals and return them to the molten salt furnace 2 for use. The metal chloride liquid needs to be neutralized, which is a three-stage impurity removal process.

[0023] The primary impurity removal step mainly involves treating the chlorinated waste molten salt in molten salt furnace 2 at a high temperature of 700-800℃. The waste molten salt is discharged into intermediate tank 1. Intermediate tank 1 is maintained under a slight vacuum and compressed air is introduced to allow the waste molten salt to undergo heat treatment while in a flowing state. During this process, C (carbon), FeCl3 (ferric chloride), AlCl3 (aluminum chloride), and a small amount of chlorine gas discharged with the waste molten salt are effectively removed. This process continues until the chloride ion content in the exhaust gas is below a preset value (e.g., 1%), marking the completion of one impurity removal cycle. This process ensures that no boilable chloride residues remain in the waste molten salt, and typically takes 30 ± 5 minutes.

[0024] After initial impurity removal, the waste molten salt undergoes high-temperature centrifugation. This step utilizes the high fluidity of the molten material to separate unreacted titanium slag from the waste molten salt. The waste molten salt is then further cooled and washed with a saturated sodium chloride solution. By controlling the washing pressure (e.g., 0.1-0.3 MPa), other metal chlorides in the waste molten salt are dissolved in the solution, resulting in pure sodium chloride crystals. Simultaneously, this step also generates a metal chloride solution containing NaCl (sodium chloride), FeCl2 (ferrous chloride), CaCl2 (calcium chloride), MgCl2 (magnesium chloride), and KCl (potassium chloride).

[0025] The process involves three stages of impurity removal and subsequent treatment. The sodium chloride crystals obtained after the second impurity removal stage are dried and crushed using the residual heat of the molten salt, and then returned to molten salt furnace 2 for reuse. This not only reduces waste volume but also improves energy utilization efficiency. Simultaneously, the metallic chloride solution produced during the second impurity removal stage requires neutralization to remove harmful metal ions. This step typically involves adding an appropriate neutralizing agent to precipitate the metal ions from the filtrate, which is then separated and sent to the next washing stage. This allows for the recycling of washing water, significantly reducing water waste. After neutralization, a recyclable saturated sodium chloride solution is formed and reused in the molten salt washing process.

[0026] In this embodiment, in step S1, the process of maintaining a micro-vacuum state in the intermediate tank 1 and introducing compressed air is achieved by controlling the negative pressure of the exhaust gas system to keep the waste molten salt in a flowing state for heat preservation treatment, thereby effectively removing C, FeCl3, AlCl3 and a small amount of chlorine gas discharged with the waste molten salt.

[0027] Specifically, the heat preservation process involves introducing compressed air to burn the unreacted petroleum coke while maintaining a negative pressure of 0.05-0.1 kPa and keeping the temperature between 700-800°C to prevent the molten salt from solidifying.

[0028] Furthermore, in step S1, the preset value is that the chloride ion content in the exhaust gas is less than 1%, which is used to determine whether the first impurity removal is completed, ensuring that there are no boilable chloride residues in the waste molten salt, with a time range of 30±5 minutes.

[0029] Furthermore, in step S2, during the high-temperature centrifugal separation step, the unreacted titanium slag is separated from the waste molten salt by utilizing the high fluidity of the melt. The main component of this titanium ore is rutile, which is then cooled, crushed, and re-granulated before being fed into the fluidized bed furnace 3 for use.

[0030] Furthermore, in step S2, during the washing of the waste molten salt with a saturated sodium chloride solution, the washing pressure is controlled to dissolve other metal chlorides in the waste molten salt into the solution, thereby obtaining pure sodium chloride crystals. These sodium chloride crystals are then dried using the residual heat of the waste molten salt and returned to the molten salt furnace 2 for use.

[0031] Furthermore, in step S2, the washing pressure is 0.1-0.3 MPa. After washing, the waste molten salt is broken up by water pressure, and white insoluble matter is visible in the mixture. The white insoluble matter and filtrate are separated to obtain sodium chloride crystals and a metal chloride solution containing NaCl, FeCl2, CaCl2, MgCl2, and KCl.

[0032] Furthermore, the metallic chloride solution produced after one washing with saturated sodium chloride needs to be neutralized to remove other metal ions and form a saturated sodium chloride solution for reuse, in order to prevent chloride ions from having a common ion effect and resulting in poor washing effect.

[0033] Furthermore, in step S3, where the metal chlorination solution needs to be neutralized, an appropriate neutralizing agent is added to precipitate the metal ions in the filtrate, and then the filtrate is separated and sent to the next washing section, thereby realizing the recycling of washing water and reducing water waste.

[0034] Furthermore, the system includes a molten salt chlorination solid waste treatment system, which comprises an intermediate tank 1, a centrifuge 4, a first slag box 5, a second slag box 6, a washing device 7, and a drying device 8. The centrifuge 4 is a high-temperature centrifuge with a rotation speed of 2000 r / min, used to centrifuge the treated waste molten salt at high temperature. The slag box 5 is used to cool the centrifuged titanium slag. The fluidized bed furnace 3 is used for fluidized bed chlorination of the crushed and regranulated material. The first slag box 5 is used to store the titanium slag that has not fully reacted after high-temperature centrifugation, and the second slag box 6 is used to store the waste molten salt after high-temperature centrifugation.

[0035] Intermediate tank 1 is the starting point of the system, used to receive chlorinated waste molten salt discharged from molten salt furnace 2. It can maintain a micro-vacuum state at a high temperature of 700-800℃ and introduce compressed air for heat preservation. During this process, harmful substances such as C, FeCl3, AlCl3, and a small amount of chlorine gas in the waste molten salt are effectively removed.

[0036] The high-temperature centrifuge 4 is one of the core pieces of equipment in the system, capable of centrifugally separating waste molten salt under high-temperature conditions. This centrifuge operates at a speed of 2000 r / min and utilizes the high fluidity of the molten material to effectively separate unreacted titanium slag from the waste molten salt. The separated titanium slag and waste molten salt will then enter different processing pathways.

[0037] The first slag box 5 is used to store titanium slag that has not fully reacted after high-temperature centrifugation. This titanium slag can be further processed or recycled after cooling. The second slag box 6 is used to store waste molten salt after high-temperature centrifugation. This waste molten salt will be sent to washing equipment 7 for washing treatment after further cooling.

[0038] Washing equipment 7 is a key piece of equipment used for washing waste molten salt. It uses a saturated sodium chloride solution to wash the waste molten salt to remove impurities such as other metal chlorides. By controlling parameters such as washing pressure, pure sodium chloride crystals and a solution containing various metal chlorides can be obtained.

[0039] Drying equipment 8 utilizes the residual heat of molten salt to dry and crush sodium chloride crystals. The dried sodium chloride crystals can be returned to molten salt furnace 2 for reuse, thus realizing resource recycling.

[0040] Finally, it should be noted that the electronic components in the washing equipment 7, drying equipment 8, etc. in this embodiment are all general standard parts or parts known to those skilled in the art. Their structure and principle can be known to those skilled in the art through technical manuals or conventional experimental methods. In the idle part of this device, all the above-mentioned electrical components are connected by wires. The specific connection method should refer to the working order between each electrical component in the above working principle to complete the electrical connection. All of these are technologies known in the art.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating molten salt chlorination solid waste, characterized in that: Specifically, the steps include the following: S1. The chlorinated waste molten salt in the molten salt furnace (2) is discharged into the intermediate tank (1) at 700-800℃ and kept warm under micro-vacuum and compressed air conditions until the chloride ion content in the tail gas is lower than the preset value, which is the first impurity removal. S2. Next, the treated waste molten salt is centrifuged at high temperature. The obtained waste molten salt is further cooled and washed with saturated sodium chloride solution to obtain sodium chloride crystals and metal chloride liquid, which is the secondary impurity removal. S3. Finally, the residual heat of the waste molten salt is used to dry and crush the sodium chloride crystals and return them to the molten salt furnace (2) for use. The metal chloride liquid needs to be neutralized, which is a three-stage impurity removal process. In step S2, the step of washing the waste molten salt with saturated sodium chloride solution is to dissolve other metal chlorides in the waste molten salt into the solution by controlling the washing pressure, thereby obtaining pure sodium chloride crystals. The sodium chloride crystals are then dried using the residual heat of the waste molten salt and returned to the molten salt furnace (2) for use. In step S2, the washing pressure is 0.1-0.3 MPa. After washing, the waste molten salt is crushed by water pressure. White insoluble matter can be seen in the mixture. The white insoluble matter and the filtrate are separated to obtain sodium chloride crystals and a metal chloride solution containing NaCl, FeCl2, CaCl2, MgCl2 and KCl. The metallic chloride solution produced after a single washing with saturated sodium chloride needs to be neutralized. In step S3, where the metal chloride solution needs to be neutralized, an appropriate neutralizing agent is added to precipitate the metal ions in the filtrate, and then the filtrate is separated and enters the next washing section.

2. The method for treating molten salt chlorination solid waste according to claim 1, characterized in that: In step S1, the process of maintaining a micro-vacuum state in the intermediate tank (1) and introducing compressed air is achieved by controlling the negative pressure of the exhaust gas system.

3. The method for treating molten salt chlorination solid waste according to claim 2, characterized in that: The heat preservation process involves simultaneously introducing compressed air to burn the unreacted petroleum coke while maintaining a negative pressure of 0.05-0.1 kPa and keeping the temperature between 700-800°C to prevent the molten salt from solidifying.

4. The method for treating molten salt chlorination solid waste according to claim 1, characterized in that: In step S1, the preset value is that the chloride ion content in the exhaust gas is less than 1%.

5. The method for treating molten salt chlorination solid waste according to claim 1, characterized in that: In step S2, during the high-temperature centrifugal separation step, the unreacted titanium slag is separated from the waste molten salt by utilizing the high fluidity of the molten material.

6. The method for treating molten salt chlorination solid waste according to any one of claims 1-5, characterized in that: The system includes a molten salt chlorination solid waste treatment system, which includes an intermediate tank (1), a centrifuge (4), a first slag box (5), a second slag box (6), a washing device (7), and a drying device (8).

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