Method for reducing sodium content of calcium arsenate in causticization process

Abstract

The invention discloses a method for reducing sodium content of calcium arsenate in a causticization process, and belongs to the technical field of dressing and smelting solid waste treatment. The method comprises the following steps: injecting arsenic-containing smelting waste liquid and an oxidant into a micro-channel reactor, and filtering after reaction to respectively obtain sodium antimonate precipitate and filtrate A; heating the filtrate A, and adding lime milk to carry out causticization arsenic precipitation operation; after causticization arsenic precipitation operation is finished, heat preservation thickening operation is performed in a thickener, an underflow product and an overflow product are obtained, the underflow product is filtered, calcium arsenate filter residues and filtrate B are obtained, and the filtrate B serves as liquid caustic soda and returns to the system for reuse; hot water and the calcium arsenate filter residues are placed in a stirring barrel to be stirred, filtering is conducted after stirring is finished, calcium arsenate and filtrate C are obtained, and the filtrate C is returned to causticization arsenic precipitation operation. On the basis of different material properties, dissolution and crystallization behaviors of the materials are regulated and controlled through combination of multiple methods, the sodium content of calcium arsenate in the causticizing arsenic precipitation process is effectively reduced, and the method has the advantages of being simple in process, environmentally friendly and low in sodium content of calcium arsenate slag.

Description

Technical Field

[0001] The present invention belongs to the technical field of beneficiation and smelting solid waste treatment, and particularly relates to a method for reducing sodium content in calcium arsenate during the causticization process. Background Art

[0002] Currently, the causticization method is a commonly used method for treating arsenic-containing smelting waste liquid. The principle of this method is that calcium hydroxide, the main component in lime milk, reacts with soluble arsenic to form insoluble calcium arsenate precipitate, and caustic soda sodium hydroxide is simultaneously generated. The generated sodium hydroxide is recycled.

[0003] However, since arsenic and antimony have very similar properties, antimony often exists in arsenic-containing waste liquid. Coupled with the lime milk added during causticization, the material composition in the causticization arsenic precipitation system is extremely complex, such as sodium antimonate, sodium antimonite, sodium arsenate, disodium hydrogen arsenate, calcium arsenate, and calcium hydroxide. The equilibrium of dissolution and crystallization of the above single components is closely related to the system pH and temperature. When other components exist in the system, the supersaturation of each single material gradually increases, and the causticization arsenic precipitation efficiency of the entire system and the quality of calcium arsenate slag will be significantly affected, and many sodium salts are also lost in the calcium arsenate slag in the form of precipitation. Moreover, both arsenic and antimony are variable valence elements, commonly having +3 and +5 valence states. Arsenic and antimony cycle from the beneficiation concentrate to the smelting process, which makes the system composition more complex. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for reducing sodium content in calcium arsenate during the causticization process based on the characteristics of different components during the causticization arsenic precipitation process, aiming at the problem of sodium content in calcium arsenate during the causticization arsenic precipitation of existing arsenic-containing smelting waste liquid.

[0005] To achieve the above purpose, the following technical solutions are adopted:

[0006] A method for reducing sodium content in calcium arsenate during the causticization process, the specific steps are as follows:

[0007] S1. Inject the arsenic-containing smelting waste liquid and an oxidant into a microchannel reactor. After the reaction ends, filter to obtain sodium antimonate precipitate and filtrate A respectively;

[0008] S2. Heat up filtrate A, and then add lime milk to filtrate A for causticization arsenic precipitation operation;

[0009] S3. After the causticization arsenic precipitation operation, perform heat preservation thickening operation in a thickener to obtain underflow product and overflow product. Filter the underflow product to obtain calcium arsenate filter residue and filtrate B, and filtrate B is returned to the system for recycling as liquid caustic soda;

[0010] S4. Place hot water and calcium arsenate filter residue in a stirring tank for stirring. After stirring ends, filter to obtain high-quality calcium arsenate and filtrate C, and filtrate C is returned to the causticization arsenic precipitation operation.

[0011] Further, in S1, the pH value of the arsenic-containing smelting waste liquid is 10 - 12.5, the volume ratio of the arsenic-containing smelting waste liquid to the oxidant is 300:1 - 500:1, the reaction temperature in the microchannel reactor is 5 - 35°C, the flow rate of the arsenic-containing smelting waste liquid and the oxidant through the microchannel reactor is 15 - 30 L / min, and the structure of the microchannel reactor is a flow focusing structure or a T-shaped structure.

[0012] In S1, the oxidant is one of liquid oxygen, liquid ozone, and hydrogen peroxide.

[0013] In S2, the temperature of the filtrate A after heating is 80 - 95°C, the pH value of the causticization arsenic precipitation operation is 10 - 12.5, and the molar ratio of arsenic to calcium is 1:0.5 - 1:0.8.

[0014] In S3, the heat preservation thickening operation time is 30 - 60 min, and the temperature is 81 - 86°C.

[0015] In S4, the hot water temperature > 90°C, the rotation speed of the stirring tank is 550 - 600 r / min, the mass concentration of the material is 50 - 65%, and steam needs to be sprayed on the filter cake during filtration, and the steam temperature is 92 - 95°C.

[0016] The calcium arsenate obtained in S4 contains less than 0.8 wt% of sodium.

[0017] This method utilizes the characteristics that pentavalent antimony salts are insoluble in water and pentavalent arsenic salts are soluble in water. The arsenic-containing waste liquid reacts with the oxidant, oxidizing trivalent antimony in the arsenic-containing waste liquid to pentavalent antimony, realizing the separation of sodium antimonate precipitation from the arsenic-containing waste liquid, recovering sodium before causticization arsenic precipitation, and greatly reducing the sodium content in calcium arsenate; by utilizing the advantage of fast mass transfer of the microchannel reactor, the conversion efficiency of sodium antimonate salt is improved, and it has the advantage of low energy consumption; since the solubility of Na3AsO4 is much lower than that of Na2HAsO4, this method controls the pH and temperature of causticization arsenic precipitation, and then controls the arsenic-containing sodium salt to exist in the form of Na2HAsO4 with better water solubility, effectively reducing the sodium content in calcium arsenate slag; by regulating the ion type, ionic strength, and temperature of the insoluble sodium salt, reducing its supersaturation, and destroying the formation of sodium salt crystals, the sodium salt content in calcium arsenate is further reduced, and the efficient reuse of the lye is realized.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) In the present invention, the arsenic-containing waste liquid and the oxidant are subjected to an oxidation operation in a microchannel reactor. The high mass transfer efficiency of the microchannel reactor not only effectively improves the valence conversion of antimony but also greatly promotes the pre-removal of sodium antimonate salt, having the advantages of high efficiency and low energy consumption;

[0020] (2) The present invention further reduces the sodium content in calcium arsenate by regulating the generation of products during the causticization arsenic removal process in multiple dimensions. After the causticization arsenic precipitation operation, by regulating the environment of the generated calcium arsenate slag, the supersaturation of the insoluble sodium salt system is selectively destroyed, the sodium content in calcium arsenate is reduced, and the reuse of the lye is realized, which has the advantages of good product quality and high resource utilization rate.

[0021] (3) The present invention uses different methods to remove sodium from arsenic-containing materials at different stages from multiple dimensions. It can not only selectively remove sodium salts from calcium arsenate slag, but also has the advantage of complete sodium removal. The overall process equipment configuration is simple and suitable for large-scale popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flowchart of a method for reducing the sodium content in calcium arsenate during the causticization process provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present invention will be further described below in conjunction with the drawings. It should be noted that this embodiment is based on the present technical solution, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to this embodiment.

[0024] Example 1

[0025] The material in this example is arsenic-containing waste liquid from a smelter in Fujian. The arsenic and antimony contents are 64.45 g / L and 21.7 g / L respectively. The method proposed by the present invention is used to treat this material as follows:

[0026] S1. Inject the arsenic-containing smelting waste liquid and the oxidant into the microchannel reactor. The structure of the microchannel reactor is a T-shaped structure. The pH of the material is 11.5. The volume ratio of the arsenic-containing waste liquid to the oxidant (liquid ozone) is 400:1. The reaction temperature is 5 °C. The flow rates of the arsenic-containing waste liquid and the oxidant through the microchannel reactor are 30 L / min. After the reaction, filtration is carried out to obtain sodium antimonate precipitate and filtrate A respectively.

[0027] S2. Heat filtrate A to 90 °C. The pH for causticization arsenic precipitation is 11.5, and the ratio of arsenic to calcium is 1:0.6. Then, add lime milk to filtrate A for causticization arsenic precipitation operation.

[0028] S3. After the causticization arsenic precipitation operation, carry out heat preservation thickening operation in the thickener. The heat preservation time is 45 min, and the heat preservation temperature is 84 °C. Obtain the underflow product and the overflow product. The underflow product is filtered to obtain calcium arsenate filter residue and filtrate B. Filtrate B is returned to the system for reuse as lye.

[0029] S4. Place hot water and calcium arsenate residue in a stirring tank for stirring. The temperature of the hot water is 91°C, the rotation speed of the stirring tank is 550 r / min, the mass concentration of the material is 60%, and after stirring, filtration is carried out (steam is sprayed during filtration, and the steam temperature is 92°C) to obtain high-quality calcium arsenate and filtrate C. Filtrate C is returned to the causticization and arsenic precipitation operation.

[0030] Example 2

[0031] The material in this example is arsenic-containing waste liquid from a smelter in Xinjiang. The arsenic and antimony contents are 70.68 g / L and 25.9 g / L respectively. The following treatment is carried out on this material by using the method proposed by the present invention:

[0032] S1. Inject arsenic-containing smelting waste liquid and an oxidant into a microchannel reactor. The pH of the material is 12.5. The structure of the microchannel reactor is a T-shaped structure. The volume ratio of the arsenic-containing waste liquid to the oxidant (liquid oxygen) is 500:1. The reaction temperature is 10°C. The flow rates of the arsenic-containing waste liquid and the oxidant through the microchannel reactor are 25 L / min. After the reaction, filtration is carried out to obtain sodium antimonate precipitate and filtrate A respectively;

[0033] S2. Heat filtrate A to 80°C. The pH for causticization and arsenic precipitation is 12.5, and the ratio of arsenic to calcium is 1:0.8. Then, add lime milk to filtrate A for the causticization and arsenic precipitation operation;

[0034] S3. After the causticization and arsenic precipitation operation, carry out heat preservation and thickening operation in a thickener. The heat preservation time is 30 min, and the heat preservation temperature is 86°C to obtain an underflow product and an overflow product. The underflow product is filtered to obtain calcium arsenate filter residue and filtrate B. Filtrate B is returned to the system for reuse as liquid caustic soda;

[0035] S4. Place hot water and calcium arsenate residue in a stirring tank for stirring. The temperature of the hot water is 93°C, the rotation speed of the stirring tank is 550 r / min, the mass concentration of the material is 65%, and after stirring, filtration is carried out (steam is sprayed during filtration, and the steam temperature is 94°C) to obtain high-quality calcium arsenate and filtrate C. Filtrate C is returned to the causticization and arsenic precipitation operation.

[0036] Example 3

[0037] The material in this example is arsenic-containing waste liquid from a smelter in Fujian. The arsenic and antimony contents are 53.61 g / L and 13.6 g / L respectively. The following treatment is carried out on this material by using the method proposed by the present invention:

[0038] S1. Inject the arsenic-containing smelting waste liquid and the oxidant into a microchannel reactor. The structure of the microchannel reactor is a flow focusing structure. The pH of the material is 10. The volume ratio of the arsenic-containing waste liquid to the oxidant (hydrogen peroxide) is 300:1. The reaction temperature is 35 °C. The flow rates of the arsenic-containing waste liquid and the oxidant through the microchannel reactor are 15 L / min. After the reaction, filter to obtain sodium antimonate precipitate and filtrate A respectively;

[0039] S2. Heat filtrate A to 95 °C. The pH for causticizing and arsenic precipitation is 12. The ratio of arsenic to calcium is 1:0.5. Then add lime milk to filtrate A for causticizing and arsenic precipitation operation;

[0040] S3. After the causticizing and arsenic precipitation operation, conduct heat preservation and thickening operation in a thickener. The heat preservation time is 60 min. The heat preservation temperature is 81 °C. Obtain underflow product and overflow product. Filter the underflow product to get calcium arsenate filter residue and filtrate B. Filtrate B is returned to the system as liquid caustic soda for reuse;

[0041] S4. Place hot water and calcium arsenate slag in a stirring tank for stirring. The temperature of the hot water is 95 °C. The rotation speed of the stirring tank is 600 r / min. The mass concentration of the material is 50%. After stirring, filter (spray steam during filtration, and the steam temperature is 95 °C) to obtain high-quality calcium arsenate and filtrate C. Filtrate C is returned to the causticizing and arsenic precipitation operation.

[0042] Comparative Example 1

[0043] It has the same raw material properties as Example 1. During the causticizing process, the temperature is 90 °C, the pH is 11.5, and the ratio of arsenic to calcium is 1:0.6. Then carry out the causticizing operation. The difference is that after the causticizing operation, directly filter to obtain calcium arsenate slag.

[0044] Comparative Example 2

[0045] It has the same raw material properties as Example 2. During the causticizing process, the temperature is 80 °C, the pH is 12.5, and the ratio of arsenic to calcium is 1:0.8. Then carry out the causticizing operation. The difference is that after the causticizing operation, directly filter to obtain calcium arsenate slag.

[0046] Comparative Example 3

[0047] It has the same raw material properties as Example 3. During the causticizing process, the temperature is 95 °C, the pH is 12, and the ratio of arsenic to calcium is 1:0.5. Then carry out the causticizing operation. The difference is that after the causticizing operation, directly filter to obtain calcium arsenate slag.

[0048] The results comparison of different examples is shown in Table 1.

[0049] Table 1 Results Comparison of Different Examples

[0050]

[0051]

[0052] As can be seen from Table 1, compared with the caustic arsenic precipitation process of conventional operations, after different arsenic-containing waste liquids adopt the process proposed by the present invention, the sodium content in the calcium arsenate slag decreases significantly, indicating that the process proposed by the present invention effectively reduces the sodium salt in calcium arsenate.

[0053] For those skilled in the art, various corresponding changes and deformations can be given according to the above technical solutions and concepts, and all these changes and deformations should be included within the protection scope of the claims of the present invention.

Claims

1. A method for reducing the sodium content of calcium arsenate in a causticizing process, characterized in that: The specific steps are as follows: S1. Injecting arsenic-containing smelting waste liquid and an oxidant into a microchannel reactor, filtering after the reaction is completed to obtain sodium antimonate precipitate and filtrate A; S2. The filtrate A is heated and lime milk is added for causticizing arsenic precipitation; S3. After the causticizing arsenic precipitation operation is completed, the thickener is kept warm and thickened to obtain an underflow product and an overflow product; the underflow product is filtered to obtain a calcium arsenate residue and a filtrate B, and the filtrate B is returned to the system as a liquid caustic soda for reuse; S4. The hot water and the calcium arsenate filter residue are placed in a stirring barrel and stirred, and the calcium arsenate and filtrate C are obtained by filtration, and the filtrate C is returned to the causticizing arsenic precipitation operation.

2. The method according to claim 1, characterized in that: In S1, the pH value of the arsenic-containing smelting waste liquid is 10-12.5, the volume ratio of the arsenic-containing smelting waste liquid to the oxidant is 300:1-500:1, the reaction temperature in the microchannel reactor is 5-35°C, the flow rate of the arsenic-containing smelting waste liquid and the oxidant through the microchannel reactor is 15-30 L / min, and the structure of the microchannel reactor is a flow focusing structure or a T-type structure.

3. The method according to claim 1, characterized in that: In S1, the oxidant is one of liquid oxygen, liquid ozone and hydrogen peroxide.

4. The method according to claim 1, characterized in that: In S2, the temperature of the filtrate A after heating is 80-95°C, the pH value of the causticizing arsenic precipitation operation is 10-12.5, and the molar ratio of arsenic to calcium is 1:0.5-1:0.

8.

5. The method according to claim 1, characterized in that: In S3, the insulation and thickening operation time is 30-60 min, and the temperature is 81-86℃.

6. The method according to claim 1, characterized in that: In S4, the hot water temperature is greater than 90°C, the rotation speed of the stirring barrel is 550-600 r / min, the mass concentration of the material is 50-65%, and the filter cake needs to be sprayed with steam during filtration, and the steam temperature is 92-95°C.

7. The method according to claim 1, characterized in that: The calcium arsenate obtained in S4 contains less than 0.8wt% sodium.

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