Method for resource utilization of fused salt chlorination slag through thermometallurgy

Abstract

The invention discloses a method for resource utilization of fused salt chlorination slag in pyrometallurgy, and belongs to the technical field of titanium metallurgy solid waste recycling, and the method comprises the following steps: (1) after the fused salt chlorination slag is discharged from a furnace, adding an additive, and carrying out heat preservation and layering in a reactor to obtain upper-layer purified fused sodium chloride and lower-layer phase conversion slag; (2) discharging the purified molten sodium chloride on the upper layer, cooling, and circularly feeding into a molten salt chlorination furnace; (3) smelting and reducing the lower-layer phase conversion slag to obtain manganese-iron alloy and reducing slag; and (4) the reducing slag is subjected to leaching, enrichment, oxalic acid precipitation and roasting treatment, and a rare earth enriched product is obtained. According to the method, a pyrometallurgy mode is adopted, valuable metal elements in the fused salt chlorination slag are comprehensively recycled, compared with a traditional hydrometallurgy process, the technological process is simple, no waste water is generated, the economic value of products is high, and the problem that a large amount of fused salt chlorination slag is piled up and pollutes the environment can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium metallurgical solid waste recycling and relates to a method for resource utilization of molten salt chloride slag by pyrometallurgy, and specifically relates to a method for recovering valuable elements (sodium, manganese, iron, rare earth) in molten salt chloride slag. Background Art

[0002] Titanium is considered the world's third most abundant metal after iron and aluminum. Its light weight, high mechanical strength, excellent heat resistance, and stable chemical properties make it an irreplaceable metal. It can also form alloys with various metals for use as structural and functional materials. It is widely used in aviation, aerospace, missiles, ships, chemical and food equipment, and medical devices. In particular, it has become an irreplaceable metal in the aerospace sector.

[0003] Titanium dioxide, commonly known as titanium dioxide, is a key chemical raw material. Recognized worldwide as the best white coating for its high whiteness, non-toxicity, and optimal opacity, it is considered one of the world's three major inorganic chemical products, along with synthetic ammonia and phosphoric acid. It is widely used in the construction, chemical, decoration, and cosmetics industries. Titanium dioxide produced using the chloride method is superior to its sulfuric acid counterpart in terms of whiteness, yellowing resistance, and dispersibility. To fully utilize titanium dioxide's excellent properties and expand the production of high-end titanium products in my country, the chloride method should be vigorously developed.

[0004] In the chloride process for producing high-end titanium products, TiCl₄, as a key intermediate raw material, plays a crucial role in the production process. Currently, there are two methods for producing TiCl₄: molten salt chlorination and boiling chlorination. The boiling chlorination method offers advantages such as rapid chlorination rates and ease of equipment scalability, making it widely used internationally. However, it has stringent raw material requirements, requiring high-quality titanium-rich materials with a CaO+MgO ratio of less than 1.5%, and a particle size range of 96-140 μm to ensure a controlled fluidized state during the boiling chlorination process. The molten salt chlorination method, on the other hand, involves adding titanium-rich materials and petroleum coke in a specific ratio to a molten salt chlorination furnace. Chlorine gas is injected at a constant rate from the bottom of the furnace. Compared to the boiling chlorination method, the molten salt chlorination method has advantages in that it requires lower charge size requirements, eliminating the need for pelletizing. It also has less stringent charge chemical composition requirements and can process titanium-containing materials with high calcium and magnesium content. The TiCl₄ intermediate product obtained by the molten salt chlorination method is of higher purity and superior quality to the boiling chlorination method. However, the disadvantage of the molten salt chlorination method is that in order to ensure the normal operation of the molten salt chlorination furnace, 300 to 400 kg of molten salt chlorination slag needs to be discharged for every ton of TiCl4 produced, which is a huge emission.

[0005] Most of the molten salt chloride slag is soluble chloride, which is a kind of hazardous waste that is difficult to treat and recycle. At present, the main methods for treating molten salt chloride slag at home and abroad are stacking method and direct water dissolution method. Molten salt chloride slag belongs to Class II general industrial solid waste. When it is treated by stacking method, it is necessary to stack Class II anti-seepage reinforced slag yard, which has high investment cost, and the accumulation of molten salt chloride slag is large and occupies land. The direct water dissolution method currently used is to directly dissolve the discharged molten salt chloride slag in water, directly stack the leached residue, and use the hydrometallurgical method to remove the impurity ions in the solution step by step to obtain sodium chloride solution, which is returned to the molten salt chlorination furnace for recycling after evaporation and crystallization. However, the composition of molten salt chloride slag is complex and there are many types of impurities. When it is treated by direct water dissolution method, the impurity removal process is long, the removal of impurity ions is difficult, and the economic benefit is low. It can be seen that it is difficult to comprehensively recover the valuable elements in molten salt chloride slag by the current stacking method and direct water dissolution method. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for pyrometallurgical resource utilization of molten salt chloride slag with good economic benefits and high production efficiency, while realizing the recycling of sodium chloride in the molten salt chloride slag.

[0007] A method for utilizing molten salt chloride slag as a resource by pyrometallurgy of the present invention comprises the following steps:

[0008] (1) Additives are added to the molten salt chloride slag after it is discharged from the furnace, and the molten salt chloride slag is kept warm and separated into layers in the reactor to obtain the purified molten sodium chloride layer on the upper layer and the phase conversion slag on the lower layer;

[0009] (2) The molten sodium chloride after purification in the upper layer is discharged and circulated into the molten salt chlorination furnace after cooling;

[0010] (3) The lower phase transformation slag is melt-reduced to obtain ferromanganese alloy and reduction slag;

[0011] (4) The reduced slag is subjected to leaching-enrichment-oxalic acid precipitation-roasting treatment to obtain a rare earth enriched product.

[0012] In a preferred embodiment, in step (1), the additive is one or more of silicates, carbonates, and bicarbonates; silicates include sodium silicate and potassium silicate, carbonates include sodium carbonate and potassium carbonate, and bicarbonates include sodium bicarbonate and potassium bicarbonate.

[0013] In a more preferred embodiment, the molar amount of the additive is 1 to 2 times, preferably 1 to 1.5 times, the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride, ferric chloride, and rare earth chloride in the molten salt chloride slag. Under the action of the additive, metal chlorides such as CaCl2, MgCl2, MnCl2, FeCl2, FeCl3, and ScCl3 undergo mineral phase transformation to form silicates, carbonates, or metal oxides, while NaCl remains in the form of a chloride salt.

[0014] In a preferred embodiment, in step (1), the molten salt chloride slag is heated and separated into layers in a reaction tank after adding the additive, and the heating temperature is 810-900° C. for 1-3 hours. The heating temperature should be higher than the melting point of sodium chloride and lower than the boiling point of sodium chloride to ensure the formation of molten sodium chloride while reducing the volatilization of molten sodium chloride. The density of molten sodium chloride is lower than that of the phase transformation slag, and the slag is separated into layers after sufficient heating time, with the upper layer being molten sodium chloride and the lower layer being the phase transformation slag.

[0015] A more preferred solution is to keep the temperature at 850°C for 3 hours.

[0016] In a preferred embodiment, in the melt reduction process of the phase transformation residue in step (3), the reducing agent used is a carbon-based reducing agent, including one or more of graphite powder, coke powder, coal powder, and metallurgical coke, the melt reduction temperature is 1400-1600°C, and the reduction time is 60-180 minutes. During the melt reduction of the phase transformation residue at high temperature, the iron and manganese compounds are easily reduced by the reducing agent to metallic iron and metallic manganese, entering the metallographic phase, while the silicate compounds or oxides of calcium, magnesium, and rare earth elements are difficult to reduce and enter the slag phase. After melt separation, an iron-manganese alloy and reduced slag are obtained.

[0017] In a preferred embodiment, in step (4), the leaching agent used includes but is not limited to hydrochloric acid and sulfuric acid, the acid concentration is 10% to 50%, and the liquid-to-solid ratio is 1 to 5.

[0018] In a preferred embodiment, in step (4), the residual calcium and magnesium compounds after leaching can be used in the building materials industry.

[0019] In a preferred embodiment, in step (4), the rare earth ion enrichment method includes but is not limited to the known solution extraction method, liquid membrane extraction method, and resin ion exchange method.

[0020] In a preferred embodiment, in step (4), the precipitant used for rare earth ion precipitation includes but is not limited to oxalic acid.

[0021] The mechanism and effects involved in the present invention are:

[0022] The valuable metal elements in the molten salt chloride slag are mainly metal chlorides, including NaCl, CaCl2, MgCl2, MnCl2, FeCl2, FeCl3, ScCl3, etc. The present invention uses silicate and / or carbonate additives that react with metal chlorides to form corresponding metal silicates, metal carbonates or metal oxides and sodium chloride. Sodium chloride has good fluidity and lower density in the molten state. It can be separated from the phase transformation residue by layers during the heat preservation stage. After salt removal treatment, the sodium chloride can be separated and recovered. After layer separation, the phase transformation residue can be dechlorinated and desodiumized, achieving reduction and stabilization of the phase transformation residue.

[0023] After phase transformation and separation, the main phases in the phase transformation residue are metal silicates, metal carbonates, and metal oxides. During the molten reduction process, iron oxides and manganese oxides are more easily reduced by the reducing agent and enter the metallographic phase, while calcium, magnesium, and rare earth oxides are difficult to reduce and enter the slag phase. During the molten reduction process, the metal melt has a higher density and separates from the slag phase, resulting in a ferromanganese alloy and reduced slag.

[0024] After phase conversion separation pre-enrichment and smelting reduction treatment for secondary enrichment, the rare earth content in the reduced slag is significantly increased by 3 to 5 times compared to molten salt chloride slag. During the acid leaching process, all rare earth elements are dissolved into the leachate, and the rare earth content in the solution is further enriched by ion exchange or solvent extraction. Finally, oxalic acid is used as a precipitant to selectively precipitate the rare earth ions in the solution. After calcination, the initial rare earth oxides are obtained.

[0025] After treatment with the present invention, sodium chloride, the main component of the molten salt chlorination slag, is fully recovered and returned to the molten salt chlorination furnace for recycling. Ferromanganese is converted into ferromanganese alloy during the molten reduction process. Rare earth elements are enriched through phase transformation and molten reduction, followed by acid leaching, enrichment, precipitation, and roasting to produce a rare earth-enriched product. The residual calcium and magnesium compounds can be used in the building materials industry. The valuable elements in the molten salt chlorination slag are fully separated and recovered, and the treatment process produces no wastewater. The product has significant economic value and broad economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a process flow chart of a method for recovering valuable components from molten salt chlorination slag;

[0027] Figure 2 This is a physical picture of the phase transformation separation of molten salt chloride slag. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0029] The present invention is further described below with reference to specific embodiments and accompanying drawings:

[0030] Example 1

[0031] Such as process flow Figure 1As shown, sodium carbonate additive was added to the molten salt chloride slag (NaCl 37.46wt%, CaCl211.39wt%, MgCl217.07wt%, MnCl29.39wt%, FeCl25.53wt%, Sc 220ppm) discharged from the furnace. The amount of the additive was controlled to be 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and ferric chloride in the molten salt chloride slag. The phase inversion temperature was 850℃ and the temperature was kept for 3 hours. The molten sodium chloride and the phase inversion residue were separated by layers, as shown in FIG. Figure 2 shown.

[0032] The molten sodium chloride obtained by layered separation has a purity of 99.99%, a calcium content of 2.95 ppm, and a magnesium content of 0.16 ppm, and can be returned to the molten salt chlorination furnace for recycling.

[0033] The main phases in the phase transformation residue are calcium manganate, calcium carbonate, magnesium manganese spinel, etc. Coke is added for melt reduction at a reduction temperature of 1450°C and a reduction time of 60 minutes. After slag and gold separation, manganese-iron alloy is obtained, in which metallic manganese accounts for 66.72% and metallic iron content is 33.28%.

[0034] The reduction slag was leached with sulfuric acid, the concentration of sulfuric acid was 15%, the liquid-solid ratio was 3, the leaching temperature was 50℃, and the Sc 3+ The leaching rate is 98.56%. P507 is used as the extractant. After two-stage extraction, a scandium-rich solution is obtained. After sodium oxalate precipitation, it is roasted at 850℃ for 3h to obtain a rare earth enriched product with a Sc2O3 content of 99.32%.

[0035] Example 2

[0036] Such as process flow Figure 1 As shown, the additive sodium carbonate is added to the molten salt chloride slag (NaCl 46.24wt%, CaCl212.63wt%, MgCl219.71wt%, MnCl211.32wt%, FeCl25.99wt%, Sc 220ppm) discharged from the furnace, and the amount of the additive is controlled to be 1.1 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and ferric chloride in the molten salt chloride slag. The phase inversion temperature is 900°C, and the temperature is kept for 3 hours. The molten sodium chloride and the phase inversion residue are separated by layers.

[0037] The molten sodium chloride obtained by layered separation has a purity of 99.99%, a calcium content of 1.68 ppm, and a magnesium content of 0.15 ppm, and can be returned to the molten salt chlorination furnace for recycling.

[0038] The main phases in the phase transformation residue are calcium manganate, magnesium manganese spinel, magnesium oxide, manganese dioxide, etc. Coke is added for melt reduction at a reduction temperature of 1500°C and a reduction time of 120 minutes. After slag and gold separation, manganese-iron alloy is obtained, in which metallic manganese accounts for 65.17% and metallic iron content is 34.83%.

[0039] The reduced slag was leached with hydrochloric acid, the concentration of hydrochloric acid was 20%, the liquid-solid ratio was 3, the leaching temperature was 65℃, and the Sc 3+ The leaching rate is 99.27%. Cyanex925 is used as the extractant. After two-stage extraction, a scandium-rich solution is obtained. After sodium oxalate precipitation, it is roasted at 850℃ for 3h to obtain a rare earth-enriched product with a Sc2O3 content of 99.91%.

[0040] Example 3

[0041] Such as process flow Figure 1 As shown, the additive sodium carbonate is added to the molten salt chloride slag (NaCl 33.09wt%, CaCl210.77wt%, MgCl215.79wt%, MnCl28.11wt%, FeCl25.98wt%, Sc 200ppm) discharged from the furnace, and the amount of the additive is controlled to be 1.5 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and ferric chloride in the molten salt chloride slag. The phase inversion temperature is 900°C, and the temperature is kept for 3 hours. The molten sodium chloride and the phase inversion residue are separated by layers.

[0042] The molten sodium chloride obtained by layered separation has a purity of 99.99%, a calcium content of 0.21 ppm, and a magnesium content of 0.03 ppm, and can be returned to the molten salt chlorination furnace for recycling.

[0043] The main phases in the phase transformation residue are sodium manganate, calcium manganate, magnesium manganese spinel, etc. Graphite powder is added for melt reduction at a reduction temperature of 1600°C for 100 minutes. After slag and gold separation, a manganese-iron alloy is obtained, in which metallic manganese accounts for 63.21% and metallic iron content is 36.79%.

[0044] The reduced slag was leached with hydrochloric acid, the concentration of hydrochloric acid was 30%, the liquid-solid ratio was 3, the leaching temperature was 40℃, and the Sc 3+ The leaching rate is 95.98%. P204 is used as the extractant. After two-stage extraction, a scandium-rich solution is obtained. After sodium oxalate precipitation, it is roasted at 850℃ for 3h to obtain a rare earth-enriched product with a Sc2O3 content of 98.47%.

[0045] Example 4

[0046] Such as process flow Figure 1As shown, sodium silicate additive is added to the molten salt chloride slag (NaCl 46.24wt%, CaCl212.63wt%, MgCl219.71wt%, MnCl211.32wt%, FeCl25.99wt%, Sc 220ppm) discharged from the furnace, and the amount of the additive is controlled to be 1.1 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and ferric chloride in the molten salt chloride slag. The phase inversion temperature is 900°C, and the temperature is kept for 3 hours. The molten sodium chloride and the phase inversion residue are separated by layers.

[0047] The molten sodium chloride obtained by layered separation has a purity of 99.99%, a calcium content of 1.13 ppm, and a magnesium content of 0.12 ppm, and can be returned to the molten salt chlorination furnace for recycling.

[0048] The main phases in the phase transformation residue are calcium silicate, manganese silicate, magnesium silicate, iron silicate, etc. Coke is added for melt reduction at a reduction temperature of 1600°C and a reduction time of 120 minutes. After slag and gold separation, a manganese-iron alloy is obtained, in which metallic manganese accounts for 63.9% and metallic iron content is 36.1%.

[0049] The reduced slag was leached with hydrochloric acid, the concentration of hydrochloric acid was 20%, the liquid-solid ratio was 3, the leaching temperature was 60℃, and the Sc 3+ The leaching rate is 99.11%. Cyanex925 is used as the extractant. After two-stage extraction, a scandium-rich solution is obtained. After sodium oxalate precipitation, it is roasted at 850℃ for 3h to obtain a rare earth-enriched product with a Sc2O3 content of 99.62%.

[0050] Example 5

[0051] Such as process flow Figure 1 As shown, sodium carbonate and sodium silicate additives (the molar ratio of sodium carbonate to sodium silicate is 1:1) are added to the molten salt chloride slag (NaCl 46.24wt%, CaCl212.63wt%, MgCl219.71wt%, MnCl211.32wt%, FeCl25.99wt%, Sc 220ppm) discharged from the furnace, and the amount of the additives is controlled to be 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and ferric chloride in the molten salt chloride slag. The phase inversion temperature is 900°C, and the temperature is kept for 3 hours. The molten sodium chloride and the phase inversion residue are separated by layers.

[0052] The molten sodium chloride obtained by layered separation has a purity of 99.99%, a calcium content of 0.82 ppm, and a magnesium content of 0.08 ppm, and can be returned to the molten salt chlorination furnace for recycling.

[0053] The main phases in the phase transformation residue are manganese silicate, magnesium calcium silicate, calcium manganate, magnesium manganese spinel, magnesium oxide, manganese dioxide, etc. Coke is added for melt reduction at a reduction temperature of 1600°C and a reduction time of 180 minutes. After slag and gold separation, manganese-iron alloy is obtained, in which metallic manganese accounts for 62.78% and metallic iron content is 37.22%.

[0054] The reduction slag is leached with sulfuric acid, the sulfuric acid concentration is 20%, the liquid-solid ratio is 3, the leaching temperature is 70℃, and the Sc 3+ The leaching rate is 97.17%. P204 is used as the extractant. After two-stage extraction, a scandium-rich solution is obtained. After sodium oxalate precipitation, it is roasted at 850℃ for 3h to obtain a rare earth enriched product with a Sc2O3 content of 99.79%.

[0055] Comparative Example 1

[0056] The molten salt chloride slag (NaCl 46.24wt%, CaCl2 12.63wt%, MgCl2 19.71wt%, MnCl2 11.32wt%, FeCl2 5.99wt%, Sc 220ppm) was directly kept at 900℃ for 3h, and the molten salt and unreacted oxides were separated by layers.

[0057] Without additives, the molten salt contains a variety of metal chlorides, with calcium chloride and magnesium chloride contents exceeding 10% by weight, making it difficult to return to the molten salt chlorination furnace for recycling. Unreacted oxidants primarily consist of silicon dioxide, aluminum oxide, and titanium dioxide, making subsequent molten reduction to recover iron-manganese alloys and rare earth oxides difficult.

[0058] Comparative Example 2

[0059] The additive sodium carbonate is added to the molten salt chloride slag (NaCl 46.24wt%, CaCl212.63wt%, MgCl219.71wt%, MnCl211.32wt%, FeCl25.99wt%, Sc 220ppm) discharged from the furnace, and the amount of the additive is controlled to be 0.5 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and ferric chloride in the molten salt chloride slag. The phase inversion temperature is 900℃, and the temperature is kept for 3h. The molten sodium chloride and the phase inversion residue are separated by layers.

[0060] Due to insufficient additives, it is difficult to completely solidify metal chlorides such as calcium chloride, magnesium chloride, manganese chloride, and ferric chloride in the molten salt chloride slag. The purity of sodium chloride in the molten salt obtained by layered separation is 85.17%, and the impurity components mainly include calcium chloride, magnesium chloride, manganese chloride, ferrous chloride, etc. The content of calcium and magnesium impurity elements is higher than the requirements of the molten salt chlorination furnace for new molten salt, making it difficult to return them to the molten salt chlorination furnace for recycling. However, the iron, manganese, and rare earth elements in the phase transformation residue are not effectively enriched, and the recovery value is low. It is difficult to economically recover iron-manganese alloys and rare earth oxides using the molten reduction-extraction method.

[0061] Comparative Example 3

[0062] The additive sodium carbonate is added to the molten salt chloride slag (NaCl 46.24wt%, CaCl212.63wt%, MgCl219.71wt%, MnCl211.32wt%, FeCl25.99wt%, Sc 220ppm) discharged from the furnace. The additive dosage is controlled to be 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride and ferric chloride in the molten salt chloride slag. The phase inversion temperature is 600℃ and the temperature is kept for 3 hours. Because the phase inversion temperature is too low and does not reach the melting temperature of the molten salt, it is difficult to achieve layered separation of the chloride salt and the phase inversion residue. After cooling, the chloride salt condenses and crystallizes in the phase inversion residue, making it difficult to separate. Due to the high sodium chloride content, it is difficult to recover the manganese iron alloy and rare earth oxides in the phase inversion residue by melt reduction-extraction.

[0063] Comparative Example 4

[0064] Sodium carbonate was added to the molten salt chloride slag (NaCl 46.24 wt%, CaCl2 12.63 wt%, MgCl2 19.71 wt%, MnCl2 11.32 wt%, FeCl2 5.99 wt%, Sc 220 ppm). The additive dosage was controlled to be 1.2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride, and ferric chloride in the molten salt chloride slag. The phase inversion temperature was set at 1000°C and the temperature was maintained for 3 hours. The molten sodium chloride and the phase inversion residue were separated by layers.

[0065] The molten sodium chloride has a purity of 99.99%, a calcium content of 1.19 ppm, and a magnesium content of 0.76 ppm. It can be recycled back into the molten salt chlorination furnace. However, due to the high phase inversion temperature, a large amount of molten sodium chloride volatilizes, resulting in a recovery rate of less than 50%, with a large amount of sodium chloride entering the gas phase. This fails to achieve efficient separation and recovery of sodium chloride from the molten salt chlorination slag.

[0066] 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 resource utilization of molten salt chloride slag by pyrometallurgy, characterized in that: The following steps are involved: (1) Additives are added to the molten salt chloride slag after it is discharged from the furnace, and the molten salt chloride slag is kept warm and separated into layers in the reactor to obtain the purified molten sodium chloride layer on the upper layer and the phase conversion slag on the lower layer; (2) The molten sodium chloride after purification in the upper layer is discharged and circulated into the molten salt chlorination furnace after cooling; (3) The lower phase transformation slag is melt-reduced to obtain ferromanganese alloy and reduction slag; (4) The reduced slag is subjected to leaching-enrichment-oxalic acid precipitation-roasting treatment to obtain a rare earth enriched product.

2. The method for recycling molten salt chloride slag by pyrometallurgy according to claim 1, characterized in that: In the step (1), the additive is one or more of silicates, carbonates, and bicarbonates; silicates include sodium silicate and potassium silicate, carbonates include sodium carbonate and potassium carbonate, and bicarbonates include sodium bicarbonate and potassium bicarbonate.

3. The method for recycling molten salt chloride slag by pyrometallurgy according to claim 1, characterized in that: The molar amount of the additive is 1 to 2 times the total molar amount of calcium chloride, magnesium chloride, manganese chloride, ferrous chloride, ferric chloride and rare earth chloride in the molten salt chloride slag.

4. The method for recycling molten salt chloride slag by pyrometallurgy according to claim 1, characterized in that: In the step (1), the molten salt chloride slag is added with additives and then kept warm in a reaction tank and separated into layers. The holding temperature is 810-900° C. and the holding time is 1-3 hours.

5. The method for utilizing molten salt chloride slag as a resource by pyrometallurgy according to claim 4, characterized in that: The holding temperature is 850℃ and the holding time is 3h.

6. The method for utilizing molten salt chloride slag as a resource by pyrometallurgy according to claim 1, characterized in that: In the step (3), the reducing agent used in the phase transformation residue melting reduction process is a carbon-based reducing agent, including one or more of graphite powder, coke powder, coal powder, and metallurgical coke. The melting reduction temperature is 1400-1600°C and the reduction time is 60-180 minutes.

7. The method for utilizing molten salt chloride slag as a resource by pyrometallurgy according to claim 1, characterized in that: In the step (4), the leaching agent used includes but is not limited to hydrochloric acid and sulfuric acid, the acid concentration is 10% to 50%, and the liquid-to-solid ratio is 1 to 5.

8. The method for utilizing molten salt chloride slag as a resource by pyrometallurgy according to claim 1, characterized in that: In the step (4), the residual calcium and magnesium compounds after leaching can be used in the building materials industry.

9. The method for utilizing molten salt chloride slag as a resource by pyrometallurgy according to claim 1, characterized in that: In the step (4), the rare earth ion enrichment method includes but is not limited to the known solution extraction method, liquid membrane extraction method, and resin ion exchange method.

10. The method for utilizing molten salt chloride slag as a resource by pyrometallurgy according to claim 1, characterized in that: In the step (4), the precipitant used for rare earth ion precipitation includes but is not limited to oxalic acid.

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