Method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid

Abstract

The invention relates to a waste circuit board resourceful treatment technology, in particular to a method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid, which comprises the following steps: (1) carrying out primary evaporative crystallization on the absorption liquid, and separating after the bromine content reaches a first target value to obtain sodium fluoride, primary crystallization mother liquor and condensed water, (2) dissolving sodium bromide in the primary crystallization mother liquor for phase equilibrium blending; (3) carrying out secondary evaporative crystallization on the blended liquid, and separating after the bromine content reaches a second target value to obtain sodium chloride, secondary crystallization mother liquor and condensed water; and (4) carrying out tertiary evaporative crystallization on the secondary crystallization mother liquor, and separating to obtain sodium bromide, tertiary crystallization mother liquor and condensed water. According to the method, high-value sodium fluoride, sodium chloride and sodium bromide can be separated and recycled from the waste circuit board smelting flue gas absorption liquid, condensate water is recycled, no waste liquid is discharged, and good economic and environment-friendly benefits are achieved.

Description

Technical Field

[0001] The invention relates to a waste circuit board resource processing technology, and in particular to a method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting fume absorption liquid. Background Art

[0002] With the continuous development of economy and technology, the amount of waste electrical and electronic products is increasing day by day, and the dismantling of waste electrical and electronic products produces a large number of waste circuit boards. These waste circuit boards contain heavy metals and toxic chemicals, so they are toxic and belong to hazardous wastes, which have great potential environmental hazards. However, at the same time, waste circuit boards are also rich in precious substances such as copper, tin, gold, silver, bromine, and fluorine. They are a kind of valuable urban mineral resources with high recycling value. Therefore, the treatment of waste circuit boards is very necessary.

[0003] At present, the industry mainly uses pyrometallurgical process to treat waste circuit boards to recover high-value metals such as copper in waste circuit boards. The flue gas in the pyrometallurgical process is generally treated by the process route of waste heat recovery-bag dust collection-alkali absorption tower deacidification-activated carbon adsorption tower dioxin removal and emptying. In addition, because the waste circuit boards also contain brominated flame retardants and fluorine-containing and chlorine-containing plastic components, etc., the waste circuit board smelting flue gas contains HF, HBr, HCl, etc., so the absorption liquid produced by the alkali absorption tower is a salt-containing waste liquid mainly composed of sodium fluoride, sodium chloride, sodium bromide, etc. The salt content in the absorption liquid of the waste circuit board smelting flue gas is high and further desalination treatment is required. The industry mainly uses direct evaporation desalination to treat it, but the evaporated salt obtained is a mixed salt composed of sodium fluoride, sodium chloride, sodium bromide, etc., which is difficult to reuse. Sodium fluoride, sodium bromide and sodium chloride are all important basic chemical raw materials, especially sodium fluoride and sodium bromide, which have high added value. The mixed salt obtained by the existing treatment method needs to be further purified if it is to be used, and the process flow is long and the cost is high. Although Chinese patent CN108164071A discloses a method for recovering bromine salt from waste circuit board smelting flue gas absorption liquid, the method involves defluorination, evaporation and other processes, and the fluorine content of the recovered bromine salt is less than 0.1%. In addition, the fluorine in the flue gas absorption liquid is first removed by precipitation method, and then the bromine salt is recovered by evaporation method. This defluorination process not only forms fluorine sludge, but also fails to achieve fluorine recovery.

[0004] In summary, the existing treatment methods cannot achieve the recovery of sodium fluoride in the waste circuit board smelting flue gas absorption liquid, nor can they directly achieve the separation and recovery of fluorine, bromine and other components during the evaporation of the flue gas absorption liquid. Therefore, it is necessary to develop a process for directly recovering sodium fluoride, sodium bromide and sodium chloride from the waste circuit board smelting flue gas absorption liquid to improve its economic and environmental benefits. Summary of the invention

[0005] The object of the present invention is to provide a method for treating waste circuit board smelting fume absorption liquid to separate and recover sodium fluoride, sodium chloride and sodium bromide therefrom.

[0006] To solve the above problems, the present invention provides a method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid, comprising the following steps:

[0007] (1) performing a first evaporation crystallization on the flue gas absorption liquid, and separating the solution when the bromine content in the solution reaches a first target value to obtain sodium fluoride, a primary crystallization mother liquor and condensed water;

[0008] (2) dissolving sodium bromide in the primary crystallization mother liquor to carry out phase equilibrium preparation so that the bromide ion concentration in the prepared solution is 150 to 250 g / L;

[0009] (3) subjecting the prepared solution to a second evaporation crystallization, and when the bromine content in the solution reaches a second target value, separation is performed to obtain sodium chloride, a secondary crystallization mother liquor, and condensed water;

[0010] (4) subjecting the secondary crystallization mother liquor to a third evaporation crystallization to obtain sodium bromide, a tertiary crystallization mother liquor and condensed water.

[0011] The phase equilibrium adjustment in step (2) of the present application is very important for achieving effective separation and recovery of sodium fluoride, sodium chloride and sodium bromide. By controlling the appropriate concentration of bromide ions, the chlorine content in the solution is reduced when the solution reaches an equilibrium state during subsequent evaporation, thereby greatly reducing the chlorine content in the sodium bromide crystalline salt in step (4), thereby ensuring a high purity of the sodium bromide crystalline salt.

[0012] As a preferred embodiment, the fluorine ion concentration in the smelting flue gas absorption liquid in step (1) is 1-15 g / L, the chloride ion concentration is 1-120 g / L, and the bromide ion concentration is 1-80 g / L.

[0013] As a preferred embodiment, in step (1), the first target value of the bromine content in the solution is 80 to 120 g / L.

[0014] As a preferred embodiment, the sodium bromide used for dissolving in step (2) is the sodium bromide obtained by three evaporation crystallizations in step (4).

[0015] As a preferred embodiment, in step (3), the second target value of the bromine content in the solution is 520-580 g / L.

[0016] Furthermore, in step (3), the second target value of the bromine content is 530-550 g / L.

[0017] As a preferred embodiment, the evaporation method is single-effect evaporation, multiple-effect evaporation or heat pump evaporation.

[0018] As a preferred embodiment, the tertiary crystallization mother liquor in step (4) is mixed with the flue gas absorption liquid and then returned to step (1) for cyclic evaporation and crystallization.

[0019] The method provided by the present invention can separate and recover sodium fluoride, sodium chloride and sodium bromide from waste circuit board smelting flue gas absorption liquid; the purity of the recovered sodium fluoride is greater than 98%, the purity of sodium chloride is greater than 95%, and the purity of sodium bromide is more than 90%; at the same time, the condensed water generated by the method of the present invention can be recycled, the crystallization mother liquor is subjected to cyclic evaporation, no waste liquid is discharged, zero discharge of flue gas absorption liquid is achieved, and the environmental benefit is high; from the perspective of the overall process, the method of the present invention also has the advantages of simple operation, low cost, easy industrialization and green process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention.

[0021] Figure 1 This is a flow chart of a method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid in this embodiment. DETAILED DESCRIPTION

[0022] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product instructions are used.

[0023] In the description of the present invention, unless otherwise specified, the terms "upper" and "lower" and the like indicate positions or state relationships based on the positions or state relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In the following examples, the instruments and equipment used without indicating the manufacturer are all conventional products that can be purchased through regular channels. The methods described are conventional methods unless otherwise specified, and the raw materials described can be obtained from public commercial channels unless otherwise specified.

[0025] Example 1

[0026] This embodiment provides a method for recovering sodium fluoride, sodium chloride and sodium bromide from waste circuit board smelting fume absorption liquid, and the processing method comprises the following steps:

[0027] (1) The flue gas absorption liquid enters the evaporation system for the first evaporation crystallization. When the bromine content in the solution reaches the first target value of 80 g / L, the crystal slurry is centrifuged to obtain sodium fluoride and a primary crystallization mother liquor. The purity of sodium fluoride is 98.8%;

[0028] (2) dissolving a certain amount of sodium bromide in the primary crystallization mother liquor to prepare a balanced solution, wherein the bromide ion concentration in the prepared solution is 150 g / L;

[0029] (3) The prepared solution is subjected to a second evaporation crystallization. When the bromine content in the solution reaches the second target value of 530 g / L, the slurry is centrifuged to separate sodium chloride and secondary crystallization mother liquor. The purity of the sodium chloride is 96.3%;

[0030] (4) The secondary crystallization mother liquor enters the third evaporation crystallization. After the solid content of the crystal slurry reaches 60%, sodium bromide and the third crystallization mother liquor are obtained by centrifugation. The purity of sodium bromide is 91.9%. The third crystallization mother liquor is mixed with the flue gas absorption liquid and returned to the evaporation system for cyclic evaporation.

[0031] Example 2

[0032] This embodiment provides a method for recovering sodium fluoride, sodium chloride and sodium bromide from waste circuit board smelting fume absorption liquid, and the processing method comprises the following steps:

[0033] (1) The flue gas absorption liquid enters the evaporation system for the first evaporation crystallization. When the bromine content in the solution reaches the first target value of 116.5 g / L, the crystal slurry is centrifuged to separate sodium fluoride and a primary crystallization mother liquor. The purity of sodium fluoride is 98.3%;

[0034] (2) dissolving a certain amount of sodium bromide in the primary crystallization mother liquor to prepare a balanced solution, wherein the bromide ion concentration in the prepared solution is 195 g / L;

[0035] (3) The prepared solution is subjected to a second evaporation crystallization. When the bromine content in the solution reaches the second target value of 550 g / L, the slurry is centrifuged to separate sodium chloride and secondary crystallization mother liquor. The purity of the sodium chloride is 95.4%.

[0036] (4) The secondary crystallization mother liquor enters the third evaporation crystallization. After the solid content of the crystal slurry reaches 60%, sodium bromide and the third crystallization mother liquor are obtained by centrifugation. The purity of sodium bromide is 93.8%. The third crystallization mother liquor is mixed with the flue gas absorption liquid and returned to the evaporation system for cyclic evaporation.

[0037] Example 3

[0038] This embodiment provides a method for recovering sodium fluoride, sodium chloride and sodium bromide from waste circuit board smelting fume absorption liquid, and the processing method comprises the following steps:

[0039] (1) The flue gas absorption liquid enters the evaporation system for the first evaporation crystallization. When the bromine content in the solution reaches the first target value of 120 g / L, the crystal slurry is centrifuged to separate sodium fluoride and a primary crystallization mother liquor. The purity of sodium fluoride is 98.1%;

[0040] (2) dissolving a certain amount of sodium bromide in the primary crystallization mother liquor to prepare a balanced solution, wherein the bromide ion concentration in the prepared solution is 250 g / L;

[0041] (3) The prepared solution is subjected to a second evaporation crystallization. When the bromine content in the solution reaches the second target value of 520 g / L, the slurry is centrifuged to separate sodium chloride and secondary crystallization mother liquor. The purity of the sodium chloride is 95.1%;

[0042] (4) The secondary crystallization mother liquor enters the third evaporation crystallization. After the solid content of the crystal slurry reaches 60%, sodium bromide and the third crystallization mother liquor are obtained by centrifugation. The purity of sodium bromide is 91.3%. The third crystallization mother liquor is mixed with the flue gas absorption liquid and returned to the evaporation system for cyclic evaporation.

[0043] Example 4

[0044] This embodiment provides a method for recovering sodium fluoride, sodium chloride and sodium bromide from waste circuit board smelting fume absorption liquid, and the processing method comprises the following steps:

[0045] (1) The flue gas absorption liquid enters the evaporation system for the first evaporation crystallization. When the bromine content in the solution reaches the first target value of 113 g / L, the crystal slurry is centrifuged to separate sodium fluoride and a primary crystallization mother liquor. The purity of sodium fluoride is 98.5%;

[0046] (2) dissolving a certain amount of sodium bromide in the primary crystallization mother liquor to prepare a balanced solution, wherein the bromide ion concentration in the prepared solution is 200 g / L;

[0047] (3) The prepared solution is subjected to a second evaporation crystallization. When the bromine content in the solution reaches the second target value of 580 g / L, the slurry is centrifuged to separate sodium chloride and secondary crystallization mother liquor. The purity of sodium chloride is 93.3%;

[0048] (4) The secondary crystallization mother liquor enters the third evaporation crystallization. After the solid content of the crystal slurry reaches 60%, sodium bromide and the third crystallization mother liquor are obtained by centrifugation. The purity of sodium bromide is 95.4%. The third crystallization mother liquor is mixed with the flue gas absorption liquid and returned to the evaporation system for cyclic evaporation.

[0049] The embodiment of the present invention utilizes the difference in solubility of sodium fluoride, sodium chloride and sodium bromide, and sequentially separates and recovers sodium fluoride, sodium chloride and sodium bromide through a three-stage evaporation process, so as to achieve separation and recovery of sodium fluoride, sodium chloride and sodium bromide in waste circuit board smelting flue gas absorption liquid. The embodiment of the present invention has the advantages of simple operation, low cost, etc., is easy to realize industrialization, and the recovered sodium fluoride, sodium chloride and sodium bromide have high purity.

[0050] The above is only an embodiment of the present invention, and the common sense such as the known specific structure, characteristics and reactant ratio in the scheme is not described too much here. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, some deformations and improvements can also be made, such as simply adjusting the selection of parameters within or near the specified parameter range, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods in the specification and other records can be used to explain the content of the claims.

Claims

1. A method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid, characterized in that The steps include: (1) performing a first evaporation crystallization on the waste circuit board smelting fume absorption liquid, and separating it when the bromine content in the solution reaches a first target value to obtain sodium fluoride, a primary crystallization mother liquor and condensed water; (2) dissolving sodium bromide in the primary crystallization mother liquor to carry out phase equilibrium preparation so that the bromide ion concentration in the prepared solution is 150 to 250 g / L; (3) subjecting the prepared solution to a second evaporation crystallization, and when the bromine content in the solution reaches a second target value, separation is performed to obtain sodium chloride, a secondary crystallization mother liquor, and condensed water; (4) subjecting the secondary crystallization mother liquor to a third evaporation crystallization to separate and obtain sodium bromide, the tertiary crystallization mother liquor and condensed water.

2. The method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting fume absorption liquid according to claim 1, characterized in that: The fluorine ion concentration in the smelting fume absorption liquid in step (1) is 1-15 g / L, the chloride ion concentration is 1-120 g / L, and the bromide ion concentration is 1-80 g / L.

3. The method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting fume absorption liquid according to claim 1, characterized in that: In the step (1), the first target value of the bromine content is 80 to 120 g / L.

4. The method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid according to claim 1, characterized in that: The sodium bromide used for dissolving in step (2) is the sodium bromide obtained by three evaporation crystallizations in step (4).

5. The method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid according to claim 1, characterized in that: In the step (3), the second target value of the bromine content is 520-580 g / L.

6. The method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid according to claim 1, characterized in that: The evaporation method is single-effect evaporation, multiple-effect evaporation or heat pump evaporation.

7. The method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid according to claim 5, characterized in that: In the step (3), the second target value of the bromine content is 530-550 g / L.

8. The method for recovering sodium fluoride, sodium chloride and sodium bromide from smelting flue gas absorption liquid according to claim 1, characterized in that: In the step (4), the tertiary crystallization mother liquor is mixed with the waste circuit board smelting flue gas and then returned to the step (1) for cyclic evaporation and crystallization.

Images