阅读说明：本技术 一种含硫废盐及其溶液的处理方法 (Treatment method of sulfur-containing waste salt and solution thereof ) 是由 张洋 范兵强 张贺东 申长帅 郑诗礼 于 2020-12-09 设计创作，主要内容包括：本发明提供了一种含硫废盐及其溶液的处理方法,所述处理方法包括以下步骤：(1)制备含硫废盐的饱和溶液；(2)混合含硫废盐与步骤(1)所得饱和溶液,进行高温盐析,固液分离后得到盐析母液与硫酸钠；(3)将步骤(2)所得盐析母液进行降温结晶,固液分离后得到硫酸铵母液与混盐；所述混盐回用于步骤(2)；(4)将步骤(3)所得硫酸铵母液进行蒸发浓缩,固液分离后得到蒸发母液与硫酸铵；所述蒸发母液回用于步骤(3)。所述处理方法既适用于含硫废盐,又适用于含硫废盐的溶液,实现了硫酸钠和硫酸铵的高效分离,同时简化了操作流程,降低了生产成本且无三废产生。(The invention provides a method for treating sulfur-containing waste salt and a solution thereof, which comprises the following steps: (1) preparing a saturated solution of sulfur-containing waste salt; (2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate; (3) cooling and crystallizing the salting-out mother liquor obtained in the step (2), and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; recycling the mixed salt in the step (2); (4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3), and carrying out solid-liquid separation to obtain the evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3). The treatment method is suitable for the sulfur-containing waste salt and the solution of the sulfur-containing waste salt, realizes the high-efficiency separation of the sodium sulfate and the ammonium sulfate, simplifies the operation process, reduces the production cost and does not generate three wastes.)

1. A method for treating sulfur-containing waste salt and a solution thereof is characterized by comprising the following steps:

(1) preparing a saturated solution of sulfur-containing waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2), and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; recycling the mixed salt in the step (2);

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3), and carrying out solid-liquid separation to obtain the evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3).

2. The process of claim 1, wherein the waste sulfur-containing salts comprise sodium sulfate and ammonium sulfate.

3. The treatment method according to claim 2, wherein the saturated solution of the sulfur-containing waste salt in the step (1) is prepared by mixing the sulfur-containing waste salt with water to prepare a saturated solution of the sulfur-containing waste salt.

4. The treatment method according to claim 2, wherein the saturated solution of the sulfur-containing waste salt in the step (1) is prepared by mixing a sulfur-containing waste salt with a solution of the sulfur-containing waste salt to prepare a saturated solution of the sulfur-containing waste salt.

5. The treatment method according to claim 2, wherein the saturated solution of the sulfur-containing waste salt in the step (1) is prepared by heating, evaporating and concentrating a solution of the sulfur-containing waste salt to prepare a saturated solution of the sulfur-containing waste salt.

6. The method according to any one of claims 1 to 5, wherein the temperature of the high-temperature salting-out in the step (2) is 60 to 100 ℃, and more preferably 80 to 90 ℃;

preferably, the high-temperature salting-out time in the step (2) is 0.5-3h, and more preferably 1-2 h.

7. The process according to any one of claims 1 to 6, wherein the temperature of the temperature-reducing crystallization in step (3) is 0 to 40 ℃, more preferably 20 to 30 ℃.

8. The preparation method according to any one of claims 1 to 7, wherein the mixed salt in the step (3) is reused in the step (2), and when the mixed salt is mixed with the saturated solution obtained in the step (1), the addition amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, and specifically the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content in the saturated solution is less than or equal to 75 g/L.

9. The method according to any one of claims 1 to 8, wherein the temperature of the evaporative concentration in step (4) is 70 to 100 ℃.

10. The method of any one of claims 1 to 9, comprising the steps of:

(1) mixing sulfur-containing waste salt with water to prepare a saturated solution of the sulfur-containing waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 60-100 ℃ for 0.5-3h, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 0-40 ℃, and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content is less than or equal to 75 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 70-100 ℃, and carrying out solid-liquid separation to obtain evaporated mother liquor and ammonium sulfate; recycling the evaporation mother liquor to the step (3);

or the preparation method comprises the following steps:

(1) mixing sulfur-containing waste salt with a solution of sulfur-containing waste salt to prepare a saturated solution of sulfur-containing waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 60-100 ℃ for 0.5-3h, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 0-40 ℃, and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content is less than or equal to 75 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 70-100 ℃, and carrying out solid-liquid separation to obtain evaporated mother liquor and ammonium sulfate; recycling the evaporation mother liquor to the step (3);

or the preparation method comprises the following steps:

(1) heating, evaporating and concentrating the solution containing the sulfur waste salt to prepare a saturated solution containing the sulfur waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 60-100 ℃ for 0.5-3h, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 0-40 ℃, and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content is less than or equal to 75 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 70-100 ℃, and carrying out solid-liquid separation to obtain evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3).

Technical Field

The invention belongs to the technical field of three-waste treatment, relates to a treatment method of industrial waste salt, and particularly relates to a treatment method of sulfur-containing waste salt and a solution thereof.

Background

In many industrial productions, such as a petroleum refining catalytic process, a sodium bicarbonate desulfurization and regeneration process, a vanadium precipitation process, an H acid production process and an alkali preparation process using sodium sulfate as a raw material, a large amount of byproduct wastewater is generated. The byproduct wastewater mainly comprises sodium sulfate and ammonium sulfate, and some wastewater also contains a small amount of heavy metals, if the byproduct wastewater is directly discharged into the environment, the byproduct wastewater not only pollutes water and soil, but also seriously harms aquatic organisms, and even enters the human body through a food chain, so that the risk of diseases of the human body is greatly increased. However, no efficient treatment method for the byproduct wastewater exists at present. Although some enterprises treat wastewater by adding sodium hydroxide into wastewater containing sodium sulfate and ammonium sulfate and deaminating the wastewater at a high temperature to obtain sodium sulfate wastewater and ammonia water, the wastewater is not applied in a large scale due to high cost, strict operation process and the like. Many enterprises can only concentrate and crystallize wastewater into mixed salt containing sodium sulfate and ammonium sulfate, and the mixed salt is stored in a storage yard as industrial waste, so that a large amount of land space is occupied, and resources are wasted.

CN111547918A discloses a sodium sulfate and ammonium sulfate wastewater resourceful treatment method, which comprises the following steps: (1) feeding raw water containing sodium sulfate and ammonium sulfate into an evaporator for evaporation concentration treatment, so that the ammonium sulfate in the raw water is unsaturated and the sodium sulfate is supersaturated, and performing solid-liquid separation on a concentrated solution to obtain sodium sulfate; (2) sending the centrifugal mother liquor into a freezing and crystallizing system for freezing treatment to ensure that sodium sulfate and ammonium sulfate are in a co-saturated state; carrying out solid-liquid separation on the crystal slurry to obtain mixed salt; (3) sending the frozen mother liquor into an evaporator for evaporation concentration treatment to ensure that ammonium sulfate is in a supersaturated state, and separating solid from liquid of a concentrated solution to obtain ammonium sulfate crystal salt; (4) and mixing the residual concentrated solution and the centrifugal mother solution, and then sending the mixture into a cooling crystallization system. However, the method is only suitable for wastewater with the ammonium sulfate content far lower than that of sodium sulfate, and is not suitable for wastewater with the ammonium sulfate content higher than that of sodium sulfate and mixed salt consisting of ammonium sulfate and sodium sulfate, and the limitation is large.

CN 107188199A discloses a process and equipment for recovering ammonium sulfate and sodium sulfate from waste water, which comprises evaporating and concentrating waste water containing sodium sulfate and ammonium sulfate at 95-103 deg.C to separate out sodium sulfate, continuing to evaporate after liquid-solid separation, and then cooling to 40 deg.C to separate out ammonium sulfate. According to a water-salt system phase diagram of the sodium sulfate and the ammonium sulfate, a large amount of sodium sulfate is brought out when the ammonium sulfate is separated out by cooling, so that the purity of the ammonium sulfate product is low, and the complete separation of the sodium sulfate and the ammonium sulfate is not realized.

CN 109110783A discloses a separation method of a mixed salt of sodium sulfate and ammonium sulfate and a treatment method of precipitated vanadium waste, wherein the method comprises the steps of dissolving the mixed salt in water, cooling to 50-55 ℃ after evaporation and concentration to separate out sodium sulfate, then continuing cooling to 10-15 ℃, and cooling to 40-45 ℃ after evaporation and concentration of filtrate to obtain ammonium sulfate. According to the water-salt system phase diagram of the sodium sulfate and the ammonium sulfate, double salt appears in the three cooling processes, so that the purity of the sodium sulfate and the ammonium sulfate is lower, the energy consumption is high in the repeated cooling and heating processes, and the operation cost is greatly increased.

Therefore, how to provide a treatment method which is suitable for sulfur-containing waste salt and solution of the sulfur-containing waste salt, realizes the high-efficiency separation of sodium sulfate and ammonium sulfate, simplifies the operation flow, reduces the production cost, does not generate three wastes, and becomes a problem to be solved by technical personnel in the field at present.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a treatment method of sulfur-containing waste salt and a solution thereof, wherein the treatment method is suitable for the sulfur-containing waste salt and the solution of the sulfur-containing waste salt, realizes the efficient separation of sodium sulfate and ammonium sulfate, simplifies the operation process, reduces the production cost and does not generate three wastes.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for treating sulfur-containing waste salt and a solution thereof, which comprises the following steps:

(1) preparing a saturated solution of sulfur-containing waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2), and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; recycling the mixed salt in the step (2);

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3), and carrying out solid-liquid separation to obtain the evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3).

In the invention, the raw material for preparation in the step (1) can be sulfur-containing waste salt or a solution of sulfur-containing waste salt, thereby providing a method for simultaneously treating sulfur-containing waste solid and waste liquid; in addition, the saturated solution can be a solution in which sodium sulfate in the sulfur-containing waste salt is saturated, a solution in which ammonium sulfate is saturated, or a solution in which mixed salt of the two is saturated in any proportion; the sulfur-containing waste salt in the step (2) is only used in the primary treatment process, and the mixed salt obtained in the step (3) and the saturated solution obtained in the step (1) are mixed after the subsequent treatment cycle is established, so that the efficient separation of sodium sulfate and ammonium sulfate in the mixed salt is ensured; and (3) adding no other components into the salting-out mother liquor in the primary treatment process, and adding the evaporation mother liquor obtained in the step (4) after the subsequent treatment cycle is established, so that the content of sodium sulfate in the evaporation mother liquor is further reduced, and the purity of an ammonium sulfate product is further improved.

According to the invention, the treatment method realizes the high-efficiency separation of sodium sulfate and ammonium sulfate by changing a system and external conditions and adopting the modes of dissolution, high-temperature salting-out, cooling crystallization and evaporative concentration according to the change rule of a phase diagram of a sulfur-containing waste brine salt system at different temperatures; the whole process flow is simple, the efficiency is high, the cost is low, and the industrial process is easy to realize; the obtained product has high purity, the nitrogen content of the ammonium sulfate product is more than 20.5 percent, the requirement of qualified products in GB 535-2014 is met, the purity of the sodium sulfate is more than 98 percent, and the requirement of first-class industrial anhydrous sodium sulfate in GB/T6009-2014 is met; in addition, the treatment method has clean process and no discharge of waste water, waste gas and waste residues.

Preferably, the waste sulfur-containing salts include sodium sulfate and ammonium sulfate.

In the present invention, the mass fractions of the sodium sulfate and the ammonium sulfate are independently 1 to 99 wt%, and may be, for example, 1 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or 99 wt%, but are not limited to the recited values, and other values not recited in the range of the values are also applicable.

The treatment method provided by the invention can be used for treating the sulfur-containing waste salt with the sodium sulfate content higher than that of the ammonium sulfate and can also be used for treating the sulfur-containing waste salt with the sodium sulfate content lower than that of the ammonium sulfate, and has good separation effect and good universality.

Preferably, the saturated solution of the sulfur-containing waste salt in the step (1) is prepared by mixing the sulfur-containing waste salt with water to prepare a saturated solution of the sulfur-containing waste salt.

Preferably, the method for preparing the saturated solution of the sulfur-containing waste salt in the step (1) is to mix the sulfur-containing waste salt with the solution of the sulfur-containing waste salt to prepare the saturated solution of the sulfur-containing waste salt.

Preferably, the method for preparing the saturated solution of the sulfur-containing waste salt in the step (1) is to heat, evaporate and concentrate the solution of the sulfur-containing waste salt to prepare the saturated solution of the sulfur-containing waste salt.

In the invention, the three preparation methods in the step (1) belong to the same technical scheme, the saturated solution of the sulfur-containing waste salt is prepared by adopting the sulfur-containing waste salt and/or the solution of the sulfur-containing waste salt, the three conditions that only the sulfur-containing waste salt exists, only the solution of the sulfur-containing waste salt exists and the solution of the sulfur-containing waste salt exists are covered, and the operation flexibility and the universality are good.

Preferably, the high temperature salting-out temperature in step (2) is 60 to 100 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable, and more preferably 80 to 90 ℃.

In the invention, the high-temperature salting-out temperature in the step (2) affects the purity of the ammonium sulfate product, and when the high-temperature salting-out temperature is lower than 60 ℃, sodium sulfate crystals cannot be fully precipitated, so that the sodium sulfate content in the salting-out mother liquor is higher, and the purity of the ammonium sulfate product is reduced.

Preferably, the high temperature salting-out time in step (2) is 0.5-3h, such as 0.5h, 1h, 1.5h, 2h, 2.5h or 3h, but not limited to the recited values, and other values in the range are also applicable, and more preferably 1-2 h.

Preferably, the temperature of the temperature-reduced crystallization in step (3) is 0 to 40 ℃, and for example, it may be 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃ or 40 ℃, but it is not limited to the recited values, and other values not recited in the range of the values are also applicable, and more preferably 20 to 30 ℃.

In the invention, the temperature of the cooling crystallization in the step (3) affects the purity of the ammonium sulfate product, and when the temperature of the cooling crystallization is higher than 40 ℃, sodium sulfate in the salting-out mother liquor cannot be sufficiently separated out, so that the purity of the ammonium sulfate product is reduced.

Preferably, the mixed salt in the step (3) is reused in the step (2) and mixed with the saturated solution obtained in the step (1), the added amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content in the saturated solution is less than or equal to 75g/L, for example, the nitrogen content in the saturated solution can be 85g/L, 90g/L, 95g/L, 100g/L, 105g/L or 110g/L, and the sodium content in the saturated solution can be 50g/L, 55g/L, 60g/L, 65g/L, 70g/L or 75g/L, but not limited to the recited values, and other unrecited values in the recited values are also applicable.

In the invention, the nitrogen or sodium content in the solution directly influences the purity of the ammonium sulfate product, and when the nitrogen content in the solution is less than 85g/L or the sodium content in the solution is more than 75g/L, the nitrogen content of the ammonium sulfate product is less than 20.5 percent, and the requirement of qualified products in GB-535 1995 cannot be met.

Preferably, the temperature of the evaporative concentration in step (4) is 70-100 ℃, for example 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

In the invention, the evaporation concentration temperature in the step (4) affects the evaporation concentration time, and when the evaporation concentration temperature is lower than 70 ℃, the evaporation concentration of the ammonium sulfate mother liquor is slowly carried out, so that the time cost is increased.

In the present invention, the solid-liquid separation in step (2), step (3) and step (4) independently comprises filtration.

As a preferred technical scheme of the invention, the preparation method comprises the following steps:

(1) mixing sulfur-containing waste salt with water to prepare a saturated solution of the sulfur-containing waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 60-100 ℃ for 0.5-3h, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 0-40 ℃, and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content is less than or equal to 75 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 70-100 ℃, and carrying out solid-liquid separation to obtain evaporated mother liquor and ammonium sulfate; recycling the evaporation mother liquor to the step (3);

or the preparation method comprises the following steps:

(1) mixing sulfur-containing waste salt with a solution of sulfur-containing waste salt to prepare a saturated solution of sulfur-containing waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 60-100 ℃ for 0.5-3h, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 0-40 ℃, and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content is less than or equal to 75 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 70-100 ℃, and carrying out solid-liquid separation to obtain evaporated mother liquor and ammonium sulfate; recycling the evaporation mother liquor to the step (3);

or the preparation method comprises the following steps:

(1) heating, evaporating and concentrating the solution containing the sulfur waste salt to prepare a saturated solution containing the sulfur waste salt;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 60-100 ℃ for 0.5-3h, and carrying out solid-liquid separation to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 0-40 ℃, and carrying out solid-liquid separation to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content and/or the sodium content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is more than or equal to 85g/L or the sodium content is less than or equal to 75 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 70-100 ℃, and carrying out solid-liquid separation to obtain evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3).

Compared with the prior art, the invention has the beneficial effects that:

(1) the treatment method provided by the invention is suitable for the sulfur-containing waste salt and the solution of the sulfur-containing waste salt, has the advantages of simple process, high efficiency and low cost, and is easy to realize the industrial process;

(2) the product obtained by the treatment method provided by the invention has high purity, the nitrogen content of the ammonium sulfate product is more than 20.5%, the requirement of qualified products in GB 535-1995 is met, the purity of the sodium sulfate is more than 98%, and the requirement of first-class industrial anhydrous sodium sulfate in GB/T6009-2014 is met;

(3) the treatment method provided by the invention has the advantages of clean process and no discharge of waste water, waste gas and waste residues.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments.

Example 1

The embodiment provides a method for treating sulfur-containing waste salt, which comprises the following steps:

(1) mixing sulfur-containing waste salt with water to prepare a saturated solution of the sulfur-containing waste salt; the mass fractions of sodium sulfate and ammonium sulfate in the sulfur-containing waste salt are both 50 wt%;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out for 1.5h at 85 ℃, and filtering to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 25 ℃, and filtering to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is 90 +/-5 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 85 ℃, and filtering to obtain evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3).

In the embodiment, the nitrogen content of the obtained ammonium sulfate product is 21.06 percent, and the requirement of qualified products in GB 535-1995 is met; the purity of the obtained sodium sulfate is 98.3 percent, and the requirements of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 are met.

Example 2

The embodiment provides a method for treating a solution containing sulfur waste salt, which comprises the following steps:

(1) heating, evaporating and concentrating the solution of the sulfur-containing waste salt at 95 ℃ to prepare a saturated solution of the sulfur-containing waste salt; the mass fraction of sodium sulfate in the solution containing the sulfur waste salt is 50 wt%, and the mass fraction of ammonium sulfate is 10 wt%;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 80 ℃ for 2h, and filtering to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 20 ℃, and filtering to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the sodium content in the saturated solution, specifically, the mixed salt is added until the sodium content in the saturated solution is 70 +/-5 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 70 ℃, and filtering to obtain the evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3).

In the embodiment, the nitrogen content of the obtained ammonium sulfate product is 20.6 percent, and the requirement of qualified products in GB 535-1995 is met; the purity of the obtained sodium sulfate is 98.6 percent, and the requirements of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 are met.

Example 3

The embodiment provides a method for treating sulfur-containing waste salt and a solution thereof, which comprises the following steps:

(1) mixing sulfur-containing waste salt with a solution of sulfur-containing waste salt to prepare a saturated solution of sulfur-containing waste salt; the mass fraction of sodium sulfate in the sulfur-containing waste salt is 25 wt%, and the mass fraction of ammonium sulfate is 75 wt%; the mass fraction of sodium sulfate in the solution containing the sulfur waste salt is 15 wt%, and the mass fraction of ammonium sulfate is 10 wt%;

(2) mixing sulfur-containing waste salt with the saturated solution obtained in the step (1), carrying out high-temperature salting-out at 60 ℃ for 3h, and filtering to obtain salting-out mother liquor and sodium sulfate;

(3) cooling and crystallizing the salting-out mother liquor obtained in the step (2) at 0 ℃, and filtering to obtain ammonium sulfate mother liquor and mixed salt; the mixed salt is reused in the step (2), and the adding amount of the mixed salt is based on the nitrogen content in the saturated solution, specifically, the mixed salt is added until the nitrogen content in the saturated solution is 90 +/-5 g/L;

(4) evaporating and concentrating the ammonium sulfate mother liquor obtained in the step (3) at 100 ℃, and filtering to obtain evaporated mother liquor and ammonium sulfate; and (4) recycling the evaporation mother liquor in the step (3).

In the embodiment, the nitrogen content of the obtained ammonium sulfate product is 20.7 percent, and the requirement of qualified products in GB 535-1995 is met; the purity of the obtained sodium sulfate is 98.8 percent, and the requirements of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 are met.

Example 4

This example provides a method for treating sulfur-containing waste salt, which is the same as example 1 except that the mixed salt is added to the saturated solution in step (2) until the nitrogen content is 75 ± 5g/L, and therefore, the following description is omitted.

In the embodiment, the nitrogen content of the obtained ammonium sulfate product is 20.2 percent, and the requirement of qualified products in GB 535-1995 is not met; the purity of the obtained sodium sulfate is 98.1 percent, and the requirements of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 are met.

Example 5

This example provides a method for treating a sulfur-containing waste salt solution, which is the same as example 2 except that the mixed salt is added to the saturated solution in step (2) until the sodium content is 85 ± 5g/L, and therefore, the following description is omitted here.

In the embodiment, the nitrogen content of the obtained ammonium sulfate product is 19.6 percent, and the requirement of qualified products in GB 535-1995 is not met; the purity of the obtained sodium sulfate is 98.3 percent, and the requirements of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 are met.

Example 6

This example provides a method for treating sulfur-containing waste salt, which is the same as example 1 except that the temperature for high-temperature salting out in step (2) is reduced to 58 ℃, and therefore, the details are not repeated herein.

In the embodiment, the nitrogen content of the obtained ammonium sulfate product is 20.1 percent, and the requirement of qualified products in GB 535-1995 is not met; the purity of the obtained sodium sulfate is 98.2 percent, and the requirements of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 are met.

Example 7

This embodiment provides a method for treating sulfur-containing waste salt, which is the same as embodiment 1 except that the temperature of the temperature reduction crystallization in step (3) is increased to 42 ℃, and therefore, the details are not repeated herein.

In the embodiment, the nitrogen content of the obtained ammonium sulfate product is 19.8 percent, and the requirement of qualified products in GB 535-1995 is not met; the purity of the obtained sodium sulfate is 98.1 percent, and the requirements of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 are met.

Comparative example 1

The comparative example provides a treatment method of a sulfur-containing waste salt solution, which adopts a sodium sulfate and ammonium sulfate wastewater resource treatment method disclosed in CN111547918A, and specifically comprises the following steps:

(1) feeding raw water containing sodium sulfate and ammonium sulfate into an evaporator for evaporation concentration treatment, so that the ammonium sulfate in the raw water is unsaturated and the sodium sulfate is supersaturated, and performing solid-liquid separation on a concentrated solution to obtain sodium sulfate;

(2) sending the centrifugal mother liquor after solid-liquid separation into a freezing and crystallizing system for freezing treatment, so that sodium sulfate and ammonium sulfate in the centrifugal mother liquor are in a co-saturated state; carrying out solid-liquid separation on the crystal slurry to obtain mixed salt consisting of sodium sulfate-ammonium sulfate double salt and part of ammonium sulfate;

(3) sending the frozen mother liquor into an evaporator for evaporation concentration treatment to ensure that ammonium sulfate in the concentrated solution is in a supersaturated state, and separating solid from liquid of the concentrated solution to obtain ammonium sulfate crystal salt;

(4) and mixing the residual concentrated solution and the centrifugal mother solution, and then sending the mixture into a cooling crystallization system for freezing treatment.

The comparative example is only suitable for the solution with the ammonium sulfate content far lower than that of the sodium sulfate, and is not suitable for the solution with the ammonium sulfate content higher than that of the sodium sulfate and the mixed salt consisting of the ammonium sulfate and the sodium sulfate, so that the limitation is large.

Therefore, the treatment method provided by the invention is suitable for the sulfur-containing waste salt and the solution of the sulfur-containing waste salt, has the advantages of simple process, high efficiency and low cost, and is easy to realize the industrial process; the product obtained by the treatment method has high purity, the nitrogen content of the ammonium sulfate product is more than 20.5 percent, the requirement of qualified products in GB 535-2014 is met, the purity of the sodium sulfate is more than 98 percent, and the requirement of first-class products of industrial anhydrous sodium sulfate in GB/T6009-2014 is met; in addition, the whole treatment process is clean, and no wastewater, waste gas and waste residue are discharged.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.