Method for recovering fused salt chlorination slag by utilizing high-temperature solid-gas separation
The low-boiling point chloride and sodium chloride in molten salt chloride slag was recovered through high-temperature solid-gas separation and ore phase conversion methods, which solved the problem of molten salt chloride slag treatment, achieved the recovery of manganese ferroalloy and rare earth resources, and achieved environmental protection and economical results.
Patent Information
- Application Number
- CN202510611667.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-13
- Publication Date
- 2025-08-08
AI Technical Summary
The molten salt chlorinated slag produced during the preparation of TiCl4 by molten salt chlorination method is difficult to deal with economically and efficiently, resulting in environmental problems such as land salinization and groundwater pollution.
The high-temperature solid-gas separation method is adopted, and the low-boiling chloride is volatile and condensed and recovered through insulation treatment. Carbonate, bicarbonate or silicate is added as additives for mineral conversion, volatile gas-phase sodium chloride is recovered, and ferromanganese alloy and reducing slag are obtained through melt reduction.
It realizes clean and efficient recycling of molten salt chlorinated slag, recovers low-boiling point chloride and sodium chloride, prepares iron-manganese alloys and rare earth-enriched raw materials, avoids secondary pollution, and has significant economic benefits.
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Figure CN120442937A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of solid waste recycling and utilization, and relates to a method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation, and specifically relates to a method for solidifying CaCl2, MgCl2, etc. from molten salt chloride slag produced by a molten salt chlorination process, and recovering NaCl and ferromanganese alloy. Background Art
[0002] Titanium, a metallic element with high strength and corrosion resistance, is commonly used in aerospace, navigation, medical devices, and chemical equipment. Titanium also has good biocompatibility, making it widely used in human implants and orthopedic surgery. Titanium dioxide, a compound with high whiteness and excellent optical properties, is considered the best white coating worldwide and is widely used in paints, coatings, plastics, paper, and other products to provide whiteness and hiding power. Titanium dioxide is also used as a photocatalyst, promoting chemical reactions under light. It is also used in the manufacture of solar cells, medical materials, and food additives.
[0003] Currently, titanium materials are primarily produced using the sulfuric acid and chloride methods. However, the sulfuric acid method can only produce sulfuric acid titanium dioxide, and the whiteness and hiding power of this titanium dioxide are inferior to those of the chloride method. The chloride method, on the other hand, can be used to produce titanium sponge and chloride titanium dioxide, both of which offer superior product quality to the sulfuric acid method.
[0004] TiCl4 is an important intermediate product in the preparation process of titanium sponge and titanium dioxide by the chloride process. The current methods for preparing TiCl4 mainly include boiling chlorination method and molten salt chlorination method. The boiling chlorination method has the advantages of fast chlorination rate and simple chlorination process, and is widely used abroad. However, it has strict requirements on raw materials. It is necessary to use high-quality titanium-rich materials with low calcium and magnesium content, and the particle size of the raw materials entering the furnace should be strictly controlled to ensure the smooth fluidization of the chlorination process of the titanium-containing raw materials. In the molten salt chlorination process, the chlorination reaction of the titanium-containing raw materials is carried out in the chloride molten salt. The production process is safer, and the molten salt has the function of purifying TiCl4, and the obtained TiCl4 product is of high quality. More importantly, the molten salt chlorination method has lower requirements on raw materials, and the requirements for the particle size and calcium and magnesium impurity content of the titanium-containing raw materials are lower than those of the boiling chlorination method.
[0005] However, the process of preparing TiCl4 by the molten salt chlorination method requires the continuous discharge of molten salt chloride slag with deteriorated physical and chemical properties, and the addition of new salt to reduce the temperature of the molten salt system, while ensuring the stable operation of the molten salt chlorination furnace. In the production practice process, 240 kg of molten salt chloride slag needs to be discharged for every ton of TiCl4 produced, which is a large amount of discharge. In addition, the molten salt chloride slag contains a large amount of soluble chloride salts. Direct stacking will cause a series of environmental problems such as land salinization and groundwater pollution. At present, direct stacking method and water dissolution method are used to treat molten salt chloride slag at home and abroad, but the existing treatment methods can only achieve the stabilization of molten salt chloride slag, or partially recover components such as sodium chloride and petroleum coke in the molten salt chloride slag. Its treatment process is long, the process is complex, and the discharge of chlorine-containing wastewater is large. It is difficult to economically and efficiently recover the various valuable components in the molten salt chloride slag, and it has not fundamentally solved the problem of treatment and recovery of molten salt chloride slag. Summary of the Invention
[0006] The purpose of the present invention is to provide a method for recovering molten salt chloride slag by high-temperature solid-gas separation, so as to solve the problem that "molten salt chloride slag contains a large amount of soluble chloride salts, and direct stacking will cause a series of environmental problems such as land salinization and groundwater pollution."
[0007] In order to achieve the above object, the present invention provides a method for recovering molten salt chloride slag by high-temperature solid-gas separation, comprising the following steps:
[0008] (1) The molten salt chloride slag discharged from the furnace is subjected to heat preservation treatment to volatilize low-boiling point chlorides from the high-boiling point phase, and the obtained low-boiling point chlorides are condensed and recovered in steps;
[0009] (2) adding one or more of carbonate, bicarbonate, and silicate to the high-boiling-point phase obtained in step (1) to carry out mineral phase conversion, recovering volatilized gaseous sodium chloride during the mineral phase conversion stage, and returning the obtained sodium chloride to the molten salt chlorination furnace;
[0010] (3) The phase transformation residue obtained in step (2) is subjected to melt reduction to obtain a ferromanganese alloy and a reduction slag, and the reduction slag is used as a raw material for rare earth recovery.
[0011] In step (1), the holding temperature is 400-600°C, at which low-boiling point chlorides including AlCl3, TiCl4, SiCl4, FeCl3, etc. will be converted into gaseous state and separated from high-boiling point substances; preferably 600°C.
[0012] In step (2), the carbonate includes but is not limited to sodium carbonate and potassium carbonate; the bicarbonate includes but is not limited to sodium bicarbonate and potassium bicarbonate; the silicate includes but is not limited to sodium silicate and potassium silicate; wherein the molar amount of carbonate, bicarbonate and silicate is 0 to 2 times, preferably 1.1 to 1.2 times, the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and the like in the molten salt chloride slag.
[0013] In step (2), the reaction temperature of the mineral phase conversion is 900-1200° C., and the reaction time is 30-60 min.
[0014] In step (2), the gas phase formed during the mineral phase conversion process is sodium chloride; at the same time, chloride salts such as calcium chloride, magnesium chloride, manganese chloride, and ferrous chloride react with additives (carbonates and / or silicates) to form a high-boiling point solid phase, which is then separated from the gas phase sodium chloride.
[0015] The reaction temperature and time of the molten salt chloride slag and additives (carbonates and / or silicates) depend on the reaction rate of the chloride salts (CaCl2, MgCl2, MnCl2, FeCl2) in the molten salt chloride slag with the additives. The higher the phase inversion temperature and the longer the phase inversion time, the more sodium chloride condenses from the gas phase and the higher the purity of the sodium chloride.
[0016] In step (2), gaseous sodium chloride is condensed and precipitated in a condensation recovery device to obtain sodium chloride powder.
[0017] In step (3), the phase transformation residue is melt-reduced at a temperature of 1400-1600° C. for 60-180 minutes using a reducing agent selected from the group consisting of coke, metallurgical coke, and petroleum coke. During the melt reduction process, the manganese and iron loading phases are readily reduced to metallic manganese and metallic iron entering the metallographic phase and separating from the slag phase. After melt reduction, a ferromanganese alloy and reduced slag are obtained.
[0018] Advantages and effects of the present invention:
[0019] The present invention discloses a method for recovering molten salt chloride slag using high-temperature solid-gas separation. This method can address the problem of the molten salt chloride slag produced during the molten salt chlorination process for preparing TiCl4, which is difficult to efficiently and economically process and therefore requires long-term storage. The method can comprehensively recover low-boiling point chlorides and sodium chloride from the molten salt chloride slag to prepare iron-manganese alloys and rare earth enrichment raw materials, thereby achieving the recycling of the molten salt chloride slag.
[0020] The method of the present invention avoids the complex leaching-impurity removal-filtration process of the aqueous solution method. Low-boiling-point chlorides in the molten salt chlorination slag are volatilized while maintaining heat. A phase-transformation additive is added at high temperature to achieve solid-gas separation. Gaseous NaCl is collected by a gas-phase condensation recovery device and, after condensation and crystallization, returned to the molten salt chlorination furnace for recycling. The phase-transformation residue is then efficiently separated into ferromanganese alloy and rare earth element-rich reduced slag through melt reduction, which can be used as a raw material for rare earth extraction.
[0021] The method of the present invention has a simple process and does not generate secondary pollution. It can cleanly and efficiently treat molten salt chlorination slag, and the recovered by-products can bring considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is a process flow chart for recovering molten salt chloride slag using high-temperature solid-gas separation in the present invention. DETAILED DESCRIPTION
[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0024] The present invention is further described below with reference to specific embodiments and accompanying drawings:
[0025] Example 1
[0026] Such as process flow Figure 1 As shown, the molten salt chloride slag (NaCl 37.46wt%, CaCl211.39wt%, MgCl217.07wt%, MnCl29.39wt%, FeCl25.53wt%, Sc220ppm) is kept warm for volatilization at a temperature of 600°C to remove low-boiling point chlorides, and the obtained low-boiling point chlorides are recovered by step-by-step condensation.
[0027] The additive Na2SiO3 was added to the treated molten salt chloride slag, with the dosage controlled to be 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, and ferrous chloride in the slag. The temperature was then raised to 1100°C and maintained for 60 minutes. During this time, a condensation recovery device was used to recover the vaporous sodium chloride, achieving phase conversion separation from the solid residue. The resulting sodium chloride had a purity of 99.24%, with calcium and magnesium impurity contents less than 0.5%, and a recovery rate of 93.64%, meeting the recycling requirements of the molten salt chlorination furnace.
[0028] The main phases in the phase transformation residue are magnesium orthosilicate, calcium metasilicate, manganese silicate, and iron silicate. Coke is added for smelting reduction at 1500°C for 60 minutes. After slag-metal separation, a ferromanganese alloy is obtained, with metallic manganese accounting for 66.72% and metallic iron 33.28%. The Sc content in the reduced slag is enriched to 520 ppm, demonstrating significant economic recovery value.
[0029] Example 2
[0030] Such as process flow Figure 1As shown, the molten salt chloride slag (NaCl 46.24wt%, CaCl2 12.63wt%, MgCl2 19.71wt%, MnCl2 11.32wt%, FeCl2 5.99wt%, Sc2 20ppm) is kept warm for volatilization at a temperature of 400°C to remove low-boiling point chlorides, and the obtained low-boiling point chlorides are recovered by step-by-step condensation.
[0031] The additive Na2CO3 was added to the treated molten salt chloride slag, with the dosage controlled to be 1.1 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, and ferrous chloride in the slag. The temperature was then raised to 1200°C and held for 180 minutes. During this time, a condensation recovery device was used to recover the vaporous sodium chloride, achieving phase conversion separation from the solid residue. The resulting sodium chloride had a purity of 99.43%, with calcium and magnesium impurity contents less than 0.5%, and a recovery rate of 99.27%, meeting the recycling requirements of the molten salt chlorination furnace.
[0032] The main phases in the phase transformation residue are calcium manganate, magnesium oxide, and spinel. Graphite powder is added for melt reduction at 1550°C for 120 minutes. After slag-metal separation, a ferromanganese alloy is obtained, with metallic manganese accounting for 65.17% and metallic iron content at 34.83%. The Sc content in the reduced slag is enriched to 830 ppm, demonstrating significant economic recovery value.
[0033] Example 3
[0034] Such as process flow Figure 1 As shown, molten salt chloride slag (NaCl 33.09wt%, CaCl2 10.77wt%, MgCl2 15.79wt%, MnCl2 8.11wt%, FeCl2 5.98wt%, Sc 200ppm) is kept warm for volatilization at a temperature of 500°C to remove low-boiling point chlorides, and the obtained low-boiling point chlorides are recovered by step-wise condensation.
[0035] The additive Na2SiO3 was added to the treated molten salt chloride slag, with the dosage controlled to be 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, and ferrous chloride in the slag. The temperature was then raised to 1100°C and maintained for 60 minutes. During this time, a condensation recovery device was used to recover the vaporous sodium chloride, achieving phase conversion separation from the solid residue. The resulting sodium chloride had a purity of 99.17%, with calcium and magnesium impurity contents less than 0.5%, and a recovery rate of 93.59%, meeting the recycling requirements of the molten salt chlorination furnace.
[0036] The main phases in the phase transformation residue are magnesium orthosilicate, calcium metasilicate, manganese silicate, and iron silicate. Graphite powder is added for melt reduction at 1600°C for 100 minutes. After slag-metal separation, a ferromanganese alloy is obtained, with metallic manganese accounting for 63.21% and metallic iron 36.79%. The Sc content in the reduced slag is enriched to 550 ppm, demonstrating significant economic recovery value.
[0037] Example 4
[0038] Such as process flow Figure 1 As shown, the molten salt chloride slag (NaCl 46.24wt%, CaCl2 12.63wt%, MgCl2 19.71wt%, MnCl2 11.32wt%, FeCl2 5.99wt%, Sc2 20ppm) is kept warm for volatilization at a temperature of 400°C to remove low-boiling point chlorides, and the obtained low-boiling point chlorides are recovered by step-by-step condensation.
[0039] The composite additives Na2CO3 and Na2SiO3 (sodium carbonate to sodium silicate at a molar ratio of 1:1) were added to the treated molten salt chloride slag, with the additive dosage controlled to 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, and ferrous chloride in the molten salt chloride slag. The temperature was then raised to 1200°C and held for 180 minutes. During this time, a condensation recovery device was used to recover the vaporous sodium chloride, achieving phase conversion separation from the solid residue. The resulting sodium chloride had a purity of 99.67%, with calcium and magnesium contents less than 0.2%, and a recovery rate of 99.49%, meeting the requirements for recycling in molten salt chlorination furnaces.
[0040] The main phases in the phase transformation residue are calcium manganate, magnesium metasilicate, calcium metasilicate, and iron silicate. Graphite powder is added for melt reduction at 1600°C for 120 minutes. After slag-metal separation, a ferromanganese alloy is obtained, with metallic manganese accounting for 67.31% and metallic iron 32.69%. The Sc content in the reduced slag is enriched to 660 ppm, demonstrating significant economic recovery value.
[0041] Comparative Example 1
[0042] Molten salt chloride slag (NaCl 46.24wt%, CaCl2 12.63wt%, MgCl2 19.71wt%, MnCl2 11.32wt%, FeCl2 5.99wt%, Sc 220ppm) is kept warm at 400°C for volatilization to remove low-boiling point chlorides, which are then recovered by step-wise condensation.
[0043] The treated molten salt chloride slag is directly heated to 1200℃ without adding additives and kept warm for 180 minutes. During this period, the gas phase is recovered by a condensation recovery device. The sodium chloride content of the powder obtained by gas phase condensation is 76.40%, and the magnesium chloride content is 11.32%. The quality of the gas phase product is difficult to meet the requirements of the molten salt chlorination furnace recycling. In addition, there is still a large amount of soluble chloride salt in the phase conversion product, which makes it difficult to adopt the process flow. Figure 1 Recycle iron and manganese elements in a way.
[0044] Comparative Example 2
[0045] Molten salt chloride slag (NaCl 33.09wt%, CaCl2 10.77wt%, MgCl2 15.79wt%, MnCl2 8.11wt%, FeCl2 5.98wt%, Sc 200ppm) was kept warm at 500°C for volatilization to remove low-boiling point chlorides, which were then recovered by step-wise condensation.
[0046] Add the additive Na2SiO3 to the treated molten salt chloride slag, control the amount of the additive to 0.5 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride and ferrous chloride in the molten salt chloride slag, and heat it to 1200°C and keep it warm for 60 minutes. During this period, a condensation recovery device is used to recover gaseous sodium chloride to achieve phase conversion separation of gaseous sodium chloride and solid residue. The purity of the obtained sodium chloride is 87.10%, and the magnesium chloride content is 8.39%. The content of calcium and magnesium impurities in the gaseous product is relatively high, which makes it difficult to meet the requirements of the recycling of the molten salt chlorination furnace. Moreover, when the amount of additive is small, there is still a large amount of soluble chloride salt in the residue, which makes it difficult to adopt the process flow. Figure 1 Recycle iron and manganese elements in a way.
[0047] Comparative Example 3
[0048] Molten salt chloride slag (NaCl 46.24wt%, CaCl2 12.63wt%, MgCl2 19.71wt%, MnCl2 11.32wt%, FeCl2 5.99wt%, Sc 220ppm) is kept warm at 400°C for volatilization to remove low-boiling point chlorides, which are then recovered by step-wise condensation.
[0049] The additive Na2SiO3 was added to the treated molten salt chloride slag, with the dosage controlled to be 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, and ferrous chloride in the slag. The temperature was then raised to 800°C and held for 60 minutes. The resulting sodium chloride recovery rate was only 9.94%. Due to the low phase inversion temperature, only a small amount of sodium chloride melted and volatilized, leaving a large amount of sodium chloride in the phase inversion residue. Furthermore, this residual sodium chloride made it difficult to recover the ferromanganese alloy from the phase inversion residue using a melt reduction method.
[0050] The above is only a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiment. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered as the scope of protection of the present invention.
Claims
1. A method for recovering molten salt chloride slag by high-temperature solid-gas separation, characterized in that: The following steps are involved: (1) The molten salt chloride slag discharged from the furnace is subjected to heat preservation treatment to volatilize low-boiling point chlorides from the high-boiling point phase, and the obtained low-boiling point chlorides are condensed and recovered in steps; (2) adding one or more of carbonate, bicarbonate, and silicate to the high-boiling-point phase obtained in step (1) to carry out mineral phase conversion, recovering volatilized gaseous sodium chloride during the mineral phase conversion stage, and returning the obtained sodium chloride to the molten salt chlorination furnace; (3) The phase transformation residue obtained in step (2) is subjected to melt reduction to obtain a ferromanganese alloy and a reduction slag, and the reduction slag is used as a raw material for rare earth recovery.
2. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 1, characterized in that: In step (1), the holding temperature is 400-600° C. At this temperature, low-boiling-point chlorides including AlCl 3 , TiCl 4 , SiCl 4 , and FeCl 3 will be converted into gaseous state and separated from high-boiling-point substances.
3. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 2, characterized in that: In step (1), the holding temperature is 600°C.
4. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 1, characterized in that: In step (2), the carbonate includes but is not limited to sodium carbonate and potassium carbonate; the bicarbonate includes but is not limited to sodium bicarbonate and potassium bicarbonate; the silicate includes but is not limited to sodium silicate and potassium silicate.
5. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 4, characterized in that: The molar amount of carbonate, bicarbonate and silicate is 0 to 2 times, preferably 1.1 to 1.2 times, the total molar amount of calcium chloride, magnesium chloride, manganese chloride and ferrous chloride in the molten salt chloride slag.
6. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 1, characterized in that: In step (2), the reaction temperature of the mineral phase conversion is 900-1200° C., and the reaction time is 30-60 min.
7. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 1, characterized in that: In step (2), gaseous sodium chloride is condensed and precipitated in a condensation recovery device to obtain sodium chloride powder.
8. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 1, characterized in that: In step (3), the phase transformation residue is melt-reduced at a temperature of 1400 to 1600° C. for a reduction time of 60 to 180 min.
9. The method for recovering molten salt chloride slag by utilizing high-temperature solid-gas separation according to claim 8, characterized in that: The reducing agent used in the molten reduction of the phase conversion residue includes one or more of coke, metallurgical coke, and petroleum coke.