A method for separating and enriching rare earth elements in fly ash

Abstract

This invention relates to the field of coal-based solid waste utilization, specifically to a method for separating and enriching rare earth elements in fly ash, comprising the following steps: (1) uniformly mixing fly ash with lime slurry and then heat-treating it to obtain a pretreated product; (2) crushing the pretreated product and uniformly mixing it with chloride salts to obtain a mixture; (3) heat-treating the mixture to volatilize and generate gaseous rare earth chlorides; and (4) condensing and separating the gaseous rare earth chlorides to obtain rare earth chlorides. The pretreatment in this invention can dissociate rare earth elements from aluminosilicates in fly ash, allowing the rare earth elements to be fully exposed, which is beneficial for subsequent chlorination reactions of rare earth elements and increases the content of rare earth elements in the product. The pretreated product is mixed with chloride salts and heat-treated to generate gaseous rare earth chlorides, which are then condensed to produce rare earth chlorides. The entire process is simple, generates no waste liquid, and effectively collects rare earth elements, showing good application prospects and value.

Description

Technical Field

[0001] This invention relates to the field of coal-based solid waste utilization technology, specifically to a method for separating and enriching rare earth elements in fly ash. Background Technology

[0002] Fly ash has been widely used as a building material raw material. However, in addition to its rich silicon and aluminum content, fly ash also contains a certain amount of high-value rare earth elements, which have not been well utilized. Developing the separation and enrichment of key rare earth elements, coupled with the existing coal-fired power industry, to form secondary mineral resources enriched in rare earths, and promoting the high-value utilization of fly ash can provide a realistic and reliable way to diversify the supply of rare earth resources in my country.

[0003] Patents CN108220630B and CN108913906B disclose methods for extracting rare earth elements. However, these methods employ large amounts of acidic or alkaline agents and involve processes such as dissolution, filtration, elution, and pH adjustment. The entire process is complex and generates significant waste liquid, causing substantial environmental pollution. Therefore, we propose a method for the separation and enrichment of rare earth elements in fly ash. Summary of the Invention

[0004] (I) In view of the shortcomings of the prior art, the present invention provides a method for separating and enriching rare earth elements in fly ash, which overcomes the problems of complex rare earth element extraction process and large amount of waste liquid generated in the prior art. The whole process is simple, no waste liquid is generated, and rare earth elements can be effectively separated and enriched, which has good application prospects and application value.

[0005] (II) To achieve the above objectives, the present invention provides the following technical solution: a method for separating and enriching rare earth elements in fly ash, comprising the following steps:

[0006] (1) The fly ash and lime slurry are mixed evenly and then heat-treated to obtain the pretreated product;

[0007] (2) The pretreated product was crushed and mixed uniformly with chloride salt to obtain a mixture;

[0008] (3) The mixture is heat-treated, and the rare earth elements in it undergo chlorination reaction, volatilizing to form gaseous rare earth chlorides;

[0009] (4) The gaseous rare earth chlorides are condensed and separated to obtain rare earth chlorides.

[0010] Preferably, in step (1), the mass ratio of fly ash to lime slurry is 1:(0.05-2).

[0011] Preferably, in step (1), the heat treatment temperature is 300-700℃ and the heat treatment time is 0.3-3h.

[0012] Preferably, in step (2), the chloride salt is any one or a combination of potassium chloride, sodium chloride, and ammonium chloride.

[0013] Preferably, in step (2), the mass ratio of the pretreatment product to the chloride salt is 1:(0.1-3).

[0014] Preferably, in step (3), the chlorination reaction temperature is 800-1600℃ and the chlorination reaction time is 0.5-10h.

[0015] (III) This invention provides a method for separating and enriching rare earth elements in fly ash, which has the following beneficial effects:

[0016] This invention pre-treats fly ash and lime slurry by mixing them, which can dissociate rare earth elements from aluminosilicates in fly ash, allowing the rare earth elements to be fully exposed. This is beneficial for the subsequent chlorination reaction of rare earth elements and can increase the content of rare earth elements in the product.

[0017] The pretreated product is then mixed with chloride salt and heat-treated to generate gaseous rare earth chlorides, which are then condensed to produce rare earth chlorides. The entire process is simple, generates no waste liquid, and can effectively separate and enrich rare earth elements, showing good application prospects and value. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for separating and enriching rare earth elements in fly ash according to the present invention.

[0019] Figure 2 This is a SEM image of rare earth chlorides in Example 1 of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Example 1

[0022] A method for separating and enriching rare earth elements in fly ash involves first uniformly mixing fly ash and lime slurry (calculated as CaO) at a mass ratio of 1:1, and then treating the mixture at 500℃ for 2 hours to obtain a pretreated product. The pretreated product is then crushed using a pulverizer and mixed with sodium chloride at a mass ratio of 1:2. The mixture is then chlorinated at 1200℃ for 5 hours, during which the rare earth elements undergo a chlorination reaction, volatilizing into gaseous rare earth chlorides. These gaseous rare earth chlorides are then obtained after condensation and separation.

[0023] Table 1. Composition and content (%) of fly ash

[0024]

[0025] Table 2. Rare earth element content in fly ash (μg / g)

[0026]

[0027] Example 2

[0028] A method for separating and enriching rare earth elements in fly ash involves first uniformly mixing fly ash and lime slurry (calculated as CaO) at a mass ratio of 1:0.1, and then treating the mixture at 350℃ for 0.5 h to obtain a pretreated product. The pretreated product is then crushed using a pulverizer and mixed with sodium chloride at a mass ratio of 1:0.1. The mixture is then chlorinated at 800℃ for 1 h, during which the rare earth elements undergo a chlorination reaction, volatilizing into gaseous rare earth chlorides. After condensation and separation, the rare earth chlorides are obtained.

[0029] In this embodiment, the fly ash and lime slurry used are the same as in Example 1.

[0030] Example 3

[0031] A method for separating and enriching rare earth elements in fly ash involves first uniformly mixing fly ash and lime slurry (calculated as CaO) at a mass ratio of 1:2, and then treating the mixture at 650℃ for 2.8 hours to obtain a pretreated product. The pretreated product is then crushed using a pulverizer and mixed with sodium chloride at a mass ratio of 1:3. The mixture is then chlorinated at 1600℃ for 8 hours, during which the rare earth elements undergo a chlorination reaction, volatilizing into gaseous rare earth chlorides. These gaseous rare earth chlorides are then obtained after condensation and separation.

[0032] In this embodiment, the fly ash and lime slurry used are the same as in Example 1.

[0033] Example 4

[0034] A method for separating and enriching rare earth elements in fly ash involves first uniformly mixing fly ash and lime slurry (calculated as CaO) at a mass ratio of 1:1, and then treating the mixture at 500℃ for 2 hours to obtain a pretreated product. The pretreated product is then crushed using a pulverizer and mixed with potassium chloride at a mass ratio of 1:2. The mixture is then chlorinated at 1200℃ for 5 hours, during which the rare earth elements undergo a chlorination reaction, volatilizing into gaseous rare earth chlorides. These gaseous rare earth chlorides are then obtained after condensation and separation.

[0035] In this embodiment, the fly ash and lime slurry used are the same as in Example 1.

[0036] Example 5

[0037] A method for separating and enriching rare earth elements in fly ash involves first uniformly mixing fly ash and lime slurry (calculated as CaO) at a mass ratio of 1:1, and then treating the mixture at 500℃ for 2 hours to obtain a pretreated product. The pretreated product is then crushed using a pulverizer and mixed with ammonium chloride at a mass ratio of 1:2. The mixture is then chlorinated at 1200℃ for 5 hours, during which the rare earth elements undergo a chlorination reaction, volatilizing into gaseous rare earth chlorides. These gaseous rare earth chlorides are then obtained after condensation and separation.

[0038] In this embodiment, the fly ash and lime slurry used are the same as in Example 1.

[0039] Comparative Example 1

[0040] A method for separating and enriching rare earth elements in fly ash involves mixing fly ash and sodium chloride at a mass ratio of 1:2, then chlorinating the mixture at 1200℃ for 5 hours. During this process, the rare earth elements undergo a chlorination reaction, volatilizing into gaseous rare earth chlorides. After condensation and separation, the rare earth chlorides are obtained.

[0041] Rare earth chloride detection

[0042] 1. The rare earth element content of the rare earth chlorides in Examples 1-5 was detected. The specific results are shown in the table below.

[0043] Table 3. Rare earth element content (μg / g) in rare earth chlorides

[0044]

[0045]

[0046] The embodiments disclosed herein are preferred embodiments, but are not limited thereto. Those skilled in the art can readily grasp the spirit of the present invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for separating and enriching rare earth elements in fly ash, characterized in that, Includes the following steps: (1) The fly ash and lime slurry are mixed evenly and then heat-treated to obtain the pretreated product; (2) The pretreated product is crushed and mixed evenly with chloride salt to obtain a mixture; (3) The mixture is heat-treated, and the rare earth elements in it undergo chlorination reaction, volatilizing to form gaseous rare earth chlorides; (4) The gaseous rare earth chlorides are condensed and separated to obtain rare earth chlorides; In step (1), the mass ratio of fly ash to lime slurry is 1:(0.05-2).

2. The method for separating and enriching rare earth elements in fly ash as described in claim 1, characterized in that, In step (1), the heat treatment temperature is 300-700℃ and the heat treatment time is 0.3-3h.

3. The method for separating and enriching rare earth elements in fly ash as described in claim 1, characterized in that, In step (2), the chloride salt is any one or a combination of potassium chloride, sodium chloride, and ammonium chloride.

4. The method for separating and enriching rare earth elements in fly ash as described in claim 1, characterized in that, In step (2), the mass ratio of the pretreated product to the chloride salt is 1:(0.1-3).

5. The method for separating and enriching rare earth elements in fly ash as described in claim 1, characterized in that, In step (3), the chlorination reaction temperature is 800-1600℃ and the chlorination reaction time is 0.5-10h.

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