Process for treating and recovering calcium fluoride from rare earth ore processing wastewater

Abstract

The application discloses a process for treating rare earth ore processing wastewater and recovering calcium fluoride, and comprises the following steps: S1, obtaining spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater respectively and filtering; S2, adding calcium washing wastewater and / or ammonia evaporation wastewater to the filtered spray tower wastewater and stirring, and making the PH value of the solution 8-10, and then performing solid-liquid separation; S3, adding calcium washing wastewater and / or ammonia evaporation wastewater to the solution obtained in the step S2 again and stirring, so that the PH value of the mixed solution is between 5-7, and then performing solid-liquid separation; S4, adding ammonia-containing wastewater to the solution obtained in the step S3 and stirring, so that the PH value is between 3-5, and then performing solid-liquid separation; and S5, flocculating and clarifying the solution obtained in the step S4. The application can treat four kinds of wastewater, i.e., spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater in a precipitation process, and subsequent supernatant treatment of the calcium fluoride is simpler.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth ore processing, and particularly relates to a process for treating rare earth ore processing wastewater and recovering calcium fluoride. BACKGROUND

[0002] In the production and processing of rare earth ore, various kinds of wastewater will be produced, including spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater in the precipitation process. The spray tower wastewater comes from the chemical workshop and contains sodium hypochlorite, sodium hydroxide and fluorine source. The calcium washing wastewater contains a large amount of calcium ions (foreign rare earth ore contains a large amount of calcium elements). The ammonia evaporation wastewater contains ammonium ions and calcium ions. The ammonia-containing wastewater contains a large amount of ammonium chloride. At present, there are various treatment methods for these wastewaters.

[0003] In the related art, the publication number CN108298714A discloses a method for removing fluorine from wastewater in fluorocarbon cerium rare earth ore smelting and separation. The wastewater containing high-concentration calcium salt in the chlorination system is used as a defluorination agent to remove fluorine from high-fluorine wastewater. The wastewater containing high-concentration calcium salt in the chlorination system is reused to avoid the separate discharge of the two kinds of wastewater, thereby reducing the wastewater treatment cost. However, the wastewater treatment of the above technical solution only involves two kinds of wastewater, the types of treated wastewater are few, and the subsequent treatment of the supernatant of calcium fluoride is still relatively complicated. SUMMARY

[0004] The present application provides a process for treating rare earth ore processing wastewater and recovering calcium fluoride, which can treat four kinds of wastewater, including spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater in the precipitation process. The subsequent treatment of the supernatant of calcium fluoride is simpler.

[0005] The present application is implemented by the following technical solutions:

[0006] A process for treating rare earth ore processing wastewater and recovering calcium fluoride, comprising the following steps:

[0007] S1, obtaining spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater respectively and filtering;

[0008] S2, adding calcium washing wastewater and / or ammonia evaporation wastewater to the filtered spray tower wastewater and stirring, and making the solution PH 8-10, and solid-liquid separation;

[0009] S3, adding calcium washing wastewater and / or ammonia evaporation wastewater to the solution obtained in step S2 and stirring to make the PH value of the mixed solution between 5-7, and solid-liquid separation;

[0010] S4, adding ammonia-containing wastewater to the solution obtained in step S3 and stirring to make the PH value between 3-5, and solid-liquid separation;

[0011] S5, flocculating and clarifying the solution obtained in step S4;

[0012] The solid obtained in steps S2, S3 and S4 is calcium fluoride.

[0013] Further, the volume ratio of the ammonia-containing wastewater to the spray tower wastewater is 1:1-11.

[0014] Further, the volume ratio of the sum of the calcium washing wastewater and the ammonia evaporation wastewater to the spray tower wastewater is 1:1.5-3.

[0015] Further, in step S2, the value of the adjusted pH is 9.

[0016] Further, in step S3, the value of the adjusted pH is 6.

[0017] Further, in step S5, the value of the adjusted pH is 3.5-4.

[0018] Further, step S2 is performed in a first-stage reaction tank, step S3 is performed in a second-stage reaction tank, and step S4 is performed in a third-stage reaction tank.

[0019] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0020] In the process for treating and recovering calcium fluoride from rare earth ore processing wastewater according to the present application, the spray tower wastewater, the calcium washing wastewater with sodium hypochlorite and / or the ammonia evaporation wastewater are mixed twice in sequence to generate the required calcium fluoride solid. When a small amount of ammonium ions is present, the ammonium ions also react with the hypochlorite ions to reduce the oxidation of the wastewater, remove ammonia nitrogen, generate hydrochloric acid to gradually reduce the pH of the solution, and better obtain crystalline calcium fluoride. Then, the ammonia-containing wastewater is added to the solution, a large amount of ammonium ions also reacts with the remaining hypochlorite ions to completely remove the oxidation of the wastewater, remove ammonia nitrogen, and generate hydrochloric acid to gradually reduce the pH of the solution, so that the additional amount of hydrochloric acid used to adjust the pH is reduced, and the processing cost is reduced. The present application can treat four kinds of wastewater, i.e., the spray tower wastewater, the calcium washing wastewater, the ammonia evaporation wastewater and the ammonia-containing wastewater in the precipitation process, and can remove the ammonia nitrogen and oxidation from the wastewater. The subsequent treatment of the supernatant of the calcium fluoride is simpler. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0022] Figure 1 The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings: DETAILED DESCRIPTION

[0023] As described in the background, in the production and processing of rare earth ore, various kinds of wastewater will be produced, including spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater in the precipitation process. The spray tower wastewater comes from the chemical workshop, and contains sodium hypochlorite, sodium hydroxide and fluorine source. The calcium washing wastewater contains a large amount of calcium ions (foreign rare earth ore contains a large amount of calcium elements). The ammonia evaporation wastewater contains ammonium ions and calcium ions. The ammonia-containing wastewater contains a large amount of ammonium chloride. At present, there are various ways to treat these wastewaters. In the related art, CN108298714A discloses a method for removing fluorine from wastewater in fluorocarbon cerium rare earth ore smelting and separation. It uses wastewater containing high-concentration calcium salt in the chlorination system as a defluorination agent to remove fluorine from high-fluorine wastewater, and the wastewater containing high-concentration calcium salt in the chlorination system is reused to avoid the separate discharge of the two kinds of wastewater, thereby reducing the wastewater treatment cost. However, the wastewater treatment of the above technical solution only involves two kinds of wastewater, and the types of treated wastewater are few, and the subsequent treatment of the supernatant of calcium fluoride is still cumbersome.

[0024] Therefore, the inventors have created a process for treating rare earth ore processing wastewater and recovering calcium fluoride to solve the above technical problems.

[0025] In order to make the purpose, technical scheme and advantages of the present application clearer, further detailed description of the present application will be given below in combination with examples and drawings. The schematic embodiments of the present application and their descriptions are only used to explain the present application, and do not limit the present application.

[0026] Embodiment

[0027] A process for treating rare earth ore processing wastewater and recovering calcium fluoride, comprising the following steps:

[0028] S1, respectively obtaining spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater and filtering. Here, the spray tower wastewater contains 5-15 g / L of sodium hypochlorite and 2-9 g / L of fluorine. The calcium washing wastewater contains 5-40 g / L of calcium ions. The ammonia evaporation wastewater contains 20-80 g / L of calcium ions and 1-8 g / L of ammonium ions. The ammonia-containing wastewater contains 100-200 g / L of ammonia.

[0029] S2, adding calcium washing wastewater and / or ammonia evaporation wastewater to the filtered spray tower wastewater and stirring, and making the solution PH 8-10, and solid-liquid separation. For example, the volume ratio of the sum of calcium washing wastewater and ammonia evaporation wastewater to spray tower wastewater is 1:1.5-3. For example, the actual calcium content in the wastewater is added to finally reach PH 8-10 as the signal to terminate the addition. Preferably, the PH value of the solution is adjusted to 9 for better effect. Additional hydrochloric acid can be used to adjust the PH.

[0030] S3, adding calcium washing wastewater and / or ammonia distillation wastewater to the solution obtained in step S2 again and stirring to make the PH value of the mixed solution between 5 and 7, and solid-liquid separation. Preferably, the PH value of the solution is adjusted to 6.

[0031] S4, adding ammonia-containing wastewater to the solution obtained in step S3 and stirring to make the PH value between 3 and 5, and solid-liquid separation. For example, the volume ratio of ammonia-containing wastewater to spray tower wastewater can be 1:1-11. Preferably, the PH value of the solution is adjusted to between 3.5 and 4.

[0032] S5, flocculating and clarifying the solution obtained in step S4. For example, a flocculating agent can be added to the solution, and the final PH is between 8 and 10 to facilitate subsequent deep fluorine removal.

[0033] In the process, the solids obtained in steps S2, S3 and S4 are calcium fluoride. For example, after filtering to obtain calcium fluoride, washing, suction filtration and drying can be performed again to obtain crystalline calcium fluoride with higher purity. For example, step S2 is performed in a first-stage reaction tank, step S3 is performed in a second-stage reaction tank, and step S4 is performed in a third-stage reaction tank.

[0034] In the process for treating rare earth ore processing wastewater and recovering calcium fluoride, by mixing the spray tower wastewater with sodium hypochlorite calcium washing wastewater and / or ammonia distillation wastewater twice in succession, the required calcium fluoride solid can be generated, a small amount of ammonium ions, and the ammonium ions also react with the hypochlorite to reduce the oxidation of the wastewater, remove ammonia and nitrogen, and generate hydrochloric acid to gradually reduce the PH of the solution to better obtain crystalline calcium fluoride. After that, ammonia-containing wastewater is added to the solution, a large amount of ammonium ions also reacts with the remaining hypochlorite to completely remove the oxidation of the wastewater, remove ammonia and nitrogen, and generate hydrochloric acid to gradually reduce the PH of the solution, so that the additional amount of hydrochloric acid used to adjust the PH is reduced, and the processing cost is reduced. The present application can treat four kinds of wastewater, i.e. spray tower wastewater, calcium washing wastewater, ammonia distillation wastewater and ammonia-containing wastewater in the precipitation process, and can remove ammonia and nitrogen and oxidation from the wastewater. The subsequent treatment of the supernatant of calcium fluoride is simpler.

[0035] The present application will be described below by specific examples.

[0036] Example 1

[0037] A process for treating rare earth ore processing wastewater and recovering calcium fluoride, comprising the following steps:

[0038] S1, obtaining spray tower wastewater, calcium washing wastewater, ammonia distillation wastewater and ammonia-containing wastewater respectively and filtering;

[0039] S2, adding calcium washing wastewater and stirring in the filtered spray tower wastewater, and making the solution PH 9, solid-liquid separation;

[0040] S3, adding ammonia distillation wastewater again to the solution obtained in step S2 and stirring, so that the PH value of the mixed solution is 6, solid-liquid separation;

[0041] S4, adding ammonia-containing wastewater to the solution obtained in step S3 and stirring, so that the PH value is 4, solid-liquid separation;

[0042] S5, flocculating and clarifying the solution obtained in step S4, then washing, suction filtering and drying the solid obtained in the above steps to obtain crystalline calcium fluoride.

[0043] The obtained calcium fluoride product and the supernatant of the final calcium fluoride are analyzed and detected, and the specific contents are shown in Table 1:

[0044] Table 1

[0045]

[0046] Example Two

[0047] A process for processing rare earth ore wastewater and recovering calcium fluoride, comprising the following steps:

[0048] S1, obtaining spray tower wastewater, calcium washing wastewater, ammonia distillation wastewater and ammonia-containing wastewater respectively and filtering;

[0049] S2, adding calcium washing wastewater and ammonia distillation wastewater to the filtered spray tower wastewater and stirring, and making the solution PH 8.6, solid-liquid separation;

[0050] S3, adding calcium washing wastewater and ammonia distillation wastewater again to the solution obtained in step S2 and stirring, so that the PH value of the mixed solution is 6.3, solid-liquid separation;

[0051] S4, adding ammonia-containing wastewater to the solution obtained in step S3 and stirring, so that the PH value is 4.2, solid-liquid separation;

[0052] S5, flocculating and clarifying the solution obtained in step S4, then washing, suction filtering and drying the solid obtained in the above steps to obtain crystalline calcium fluoride.

[0053] The obtained calcium fluoride product and the supernatant of the final calcium fluoride are analyzed and detected, and the specific contents are shown in Table 2:

[0054] Table 2

[0055]

[0056] Example Three

[0057] A process for treating and recovering calcium fluoride from rare earth ore processing wastewater, comprising the following steps:

[0058] S1, respectively, obtain spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater and filter;

[0059] S2, add ammonia evaporation wastewater to the filtered spray tower wastewater and stir, and make the solution PH 9.7, solid-liquid separation;

[0060] S3, add calcium washing wastewater to the solution obtained in step S2 and stir to make the PH value of the mixed solution 5.5, solid-liquid separation;

[0061] S4, add ammonia-containing wastewater to the solution obtained in step S3 and stir to make the PH value 3.6, solid-liquid separation;

[0062] S5, the solution obtained in step S4 is flocculated and clarified, and then the solid obtained in the above steps is washed, suction filtered and dried to obtain crystalline calcium fluoride.

[0063] The obtained calcium fluoride product and the supernatant of the final calcium fluoride are analyzed and detected, as shown in Table 2:

[0064] Table 2

[0065]

[0066] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A process for the treatment and recovery of calcium fluoride from rare earth ore processing wastewater, characterized by, The method comprises the following steps: S1, respectively obtaining spray tower wastewater, calcium washing wastewater, ammonia evaporation wastewater and ammonia-containing wastewater and filtering; S2, adding calcium washing wastewater and / or ammonia evaporation wastewater to the filtered spray tower wastewater and stirring, and adjusting the PH value of the solution to 8-10, and then solid-liquid separation; S3, adding calcium washing wastewater and / or ammonia evaporation wastewater to the solution obtained in step S2 and stirring, so that the PH value of the mixed solution is between 5-7, and then solid-liquid separation; S4, adding ammonia-containing wastewater to the solution obtained in step S3 and stirring, so that the PH value is between 3-5, and then solid-liquid separation; S5, flocculating and clarifying the solution obtained in step S4; The solid obtained in steps S2, S3 and S4 is calcium fluoride. The spray tower wastewater contains sodium hypochlorite, sodium hydroxide and fluorine source; the calcium washing wastewater contains calcium ions; the ammonia evaporation wastewater contains ammonium ions and calcium ions; and the ammonia-containing wastewater contains ammonium chloride. The volume ratio of the ammonia-containing wastewater to the spray tower wastewater is 1:1-11.

2. The process for treating and recovering calcium fluoride from rare earth ore processing wastewater as claimed in claim 1, wherein, The volume ratio of the sum of the calcium washing wastewater and the ammonia evaporation wastewater to the spray tower wastewater is 1:1.5-3.

3. The process for treating and recovering calcium fluoride from rare earth ore processing wastewater as claimed in claim 2, wherein, In step S2, the adjusted PH value is 9.

4. The process for treatment and recovery of calcium fluoride from rare earth ore processing wastewater as claimed in any one of claims 1 to 3, wherein, In step S3, the adjusted PH value is 6.

5. The process for treatment and recovery of calcium fluoride from rare earth ore processing wastewater as claimed in any one of claims 4, wherein In step 4, the adjusted PH value is 3.5-4.

6. The process for treatment and recovery of calcium fluoride from rare earth ore processing wastewater as claimed in any one of claims 5, wherein The step S2 is carried out in a first-stage reaction tank, the step S3 is carried out in a second-stage reaction tank, and the step S4 is carried out in a third-stage reaction tank.

7. The process for treating and recovering calcium fluoride from rare earth ore processing wastewater as claimed in any one of claims 1 to 3, wherein ​

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