阅读说明：本技术 一种以制盐废液生产食用盐的方法 (Method for producing edible salt by using salt production waste liquid ) 是由 左敏 杨进兵 于 2021-06-30 设计创作，主要内容包括：本发明公开一种以制盐废液生产食用盐的方法,包括以下步骤：向饱和精制盐水中加入甲醇,使氯化钠晶体在搅拌的条件下析出,经过滤后得到氯化钠粗品；将氯化钠粗品采用甲醇-氯化钠混合溶液洗涤,经脱除溶剂后得到氯化钠湿品；将氯化钠湿品进行干燥,得到氯化钠成品。本发明通过向饱和精制盐水中加入甲醇,能够降低氯化钠的溶解度,使氯化钠能够在室温下析出,无需加热,便于降低能耗；通过将氯化钠粗品采用甲醇-氯化钠混合溶液洗涤,能够在除杂的同时优化氯化钠晶体的球形度,提高防结块效果。(The invention discloses a method for producing edible salt by using salt production waste liquid, which comprises the following steps: adding methanol into saturated refined brine to separate out sodium chloride crystals under the condition of stirring, and filtering to obtain a crude product of sodium chloride; washing the crude sodium chloride product by using a methanol-sodium chloride mixed solution, and removing a solvent to obtain a wet sodium chloride product; and drying the wet sodium chloride product to obtain a finished sodium chloride product. According to the invention, the methanol is added into the saturated refined brine, so that the solubility of sodium chloride can be reduced, the sodium chloride can be separated out at room temperature, heating is not needed, and the energy consumption is reduced conveniently; the sodium chloride crude product is washed by a methanol-sodium chloride mixed solution, so that the sphericity of the sodium chloride crystal can be optimized while impurities are removed, and the anti-caking effect is improved.)

1. A method for producing edible salt by using salt-making waste liquid is characterized by comprising the following steps:

adding methanol into saturated refined brine to separate out sodium chloride crystals under the condition of stirring, and filtering to obtain a crude product of sodium chloride;

washing the sodium chloride crude product by using a methanol-sodium chloride mixed solution, and removing a solvent to obtain a sodium chloride wet product;

and drying the wet sodium chloride product to obtain a finished sodium chloride product.

2. The method for producing edible salt from the salt manufacturing waste liquid according to claim 1, wherein the mass ratio of the saturated refined brine to the methanol is 1: (0.01-10).

3. The method for producing edible salt from the salt manufacturing waste liquid according to claim 2, wherein the mass ratio of the saturated refined brine to the methanol is 1 (1.5-3).

4. The method for producing edible salt from the salt manufacturing waste liquid according to claim 1, wherein the stirring speed is 300-500 rpm, and the stirring time is 10-30 min.

5. The method for producing edible salt from the salt manufacturing waste liquid according to claim 1, wherein the mass fraction of the sodium chloride is 10 to 20% and the mass fraction of the methanol is 10 to 30% in the methanol-sodium chloride mixed solution.

6. The method for producing edible salt from the salt manufacturing waste liquid according to claim 5, wherein the mass ratio of the crude sodium chloride to the methanol-sodium chloride mixed solution is 1: (1-3).

7. The method for producing edible salt from the salt manufacturing waste liquid as claimed in claim 1, further comprising the steps of removing impurities from the salt manufacturing waste liquid and evaporating and concentrating the salt manufacturing waste liquid to obtain saturated refined brine.

8. The method for producing edible salt from the salt production waste liquid according to claim 1, wherein the impurity removal of the salt production waste liquid is one or two of membrane separation impurity removal and chemical precipitation impurity removal.

9. The method for producing edible salt from the salt production waste liquid as claimed in claim 1, wherein the content of sodium chloride in the refined brine obtained by removing impurities from the salt production waste liquid is 150-260 g/L, SO₄ ^2-The content is less than 1g/L, Ca²⁺The content is less than 0.5g/L, Mg²⁺The content is less than 1 g/L.

10. The method for producing edible salt from the salt manufacturing waste liquid according to claim 1, wherein the particle size of the sodium chloride finished product is 1-2 mm, and the content of the sodium chloride finished product is more than 90%.

Technical Field

The invention relates to the technical field of edible salt, in particular to a method for producing edible salt by using salt production waste liquid.

Background

The mother liquor after the salt is prepared from seawater, also called salt preparation waste liquor, contains a large amount of salt, can cause environmental pollution by direct discharge, and is not beneficial to improving the utilization rate of sodium chloride. The concentration is usually raised to around 30 Be' by repeated exposure to sunlight. The salt prepared by the method has low quality and serious resource waste.

Chinese patent CN100484883 discloses a process for producing refined salt from salt production waste liquid, which comprises the steps of semi-permeable filtration, evaporation thickening, cooling crystallization, collection crystallization, washing dehydration, drying and packaging. The method reduces the labor intensity of workers and improves the preparation efficiency of the salt slurry. However, the solubility of sodium chloride changes little with temperature, the capacity of sodium chloride crystal precipitation is limited in the cooling crystallization process, most of sodium chloride is still in secondary waste liquid, and the yield of sodium chloride in the obtained refined salt is low.

Disclosure of Invention

In view of the above, there is a need to provide a method for producing edible salt from a salt production waste liquid, so as to solve the technical problem of low yield of sodium chloride in refined salt produced from the salt production waste liquid in the prior art.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for producing edible salt by using salt-making waste liquid comprises the following steps:

adding methanol into saturated refined brine to separate out sodium chloride crystals under the condition of stirring, and filtering to obtain a crude product of sodium chloride;

washing the crude sodium chloride product by using a methanol-sodium chloride mixed solution, and removing a solvent to obtain a wet sodium chloride product;

and drying the wet sodium chloride product to obtain a finished sodium chloride product.

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

according to the invention, the methanol is added into the saturated refined brine, so that the solubility of sodium chloride can be reduced, the sodium chloride can be separated out at room temperature, heating is not needed, and the energy consumption is reduced conveniently; the sodium chloride crude product is washed by a methanol-sodium chloride mixed solution, so that the sphericity of the sodium chloride crystal can be optimized while impurities are removed, and the anti-caking effect is improved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a method for producing edible salt by using salt production waste liquid, which comprises the following steps:

(1) removing impurities from salt-making waste liquid: carrying out impurity removal treatment on the salt making waste liquid to obtain refined salt water; the invention is not limited to the way of removing impurities, and the skilled person can select the way according to the actual situation. For example, membrane separation, chemical precipitation and impurity removal can be performed. The content of sodium chloride in the refined brine is 150-260 g/L, SO₄ ^2-The content is less than 1g/L, Ca²⁺The content is less than 0.5g/L, Mg²⁺The content is less than 1 g/L.

(2) And (3) evaporation and concentration: evaporating and concentrating the refined brine to obtain saturated refined brine. The process of evaporation and concentration is not limited by the present invention, and those skilled in the art can select the process according to actual situations.

(3) And (3) crystallization and filtration: and adding methanol into the saturated refined brine to separate out sodium chloride crystals under the condition of stirring, and filtering to obtain a crude sodium chloride product. In the process, the mass ratio of the saturated refined brine to the methanol is 1: (0.01-10), preferably 1 (1.5-3). Within the proportion range, the using amount of the methanol can be reduced on the premise of ensuring the precipitation amount of the sodium chloride in the saturated refined brine. In the invention, the sphericity of the sodium chloride crystal can be improved and the particle size can be controlled by stirring. In some embodiments of the present invention, the stirring speed is 300 to 500rpm, and the stirring time is 10 to 30 min.

(4) Washing and desolventizing: and washing the crude sodium chloride product by using a methanol-sodium chloride mixed solution, and removing the solvent to obtain a wet sodium chloride product. In the process, in the methanol-sodium chloride mixed solution, the mass fraction of sodium chloride is 10-20%, and the mass fraction of methanol is 10-30%; the mass ratio of the crude sodium chloride to the methanol-sodium chloride mixed solution is 1: (1-3). Within the mass range, the obtained sodium chloride has good sphericity and high purity, and is not easy to agglomerate. In some embodiments of the invention, the washing process is performed in a salt scrubber.

(5) And (3) drying: and drying the wet sodium chloride product to obtain a finished sodium chloride product. In the process, the particle size of the obtained sodium chloride finished product is 1-2 mm and accounts for more than 90%.

According to the invention, the methanol is added into the saturated refined brine, so that the solubility of sodium chloride is favorably reduced, the sodium chloride can be separated out at room temperature, heating is not needed, and the energy consumption is conveniently reduced; the sodium chloride crude product is washed by a methanol-sodium chloride mixed solution, so that the sphericity of a sodium chloride crystal can be optimized while impurities are removed; meanwhile, the sphericity of the obtained sodium chloride can be controlled by controlling the mass ratio of the saturated refined brine to the methanol and the composition and the addition amount of the methanol-sodium chloride mixed solution, and the anti-caking edible salt with good sphericity is finally obtained.

In the invention, the filtrate obtained in the crystallization and filtration process can be separated into methanol and recycled.

In the following embodiments and comparative examples of the present invention, the saturated refined brine is obtained by removing impurities from the salt production waste liquid by chemical precipitation and evaporating and concentrating; saturated refined brine, SO₄ ^2-The content is 1.36g/L, Ca²⁺The content is 0.33g/L, Mg²⁺The content was 1.22 g/L.

Example 1

(1) Adding 200g of methanol into 100g of saturated refined brine to separate out sodium chloride crystals under the condition of stirring, and filtering to obtain 24.36g of crude sodium chloride; wherein the stirring speed is 400rpm, and the stirring time is 20 min.

(2) Washing the crude sodium chloride product by using 25g of methanol-sodium chloride mixed solution, and removing the solvent to obtain a wet sodium chloride product; in the methanol-sodium chloride mixed solution, the mass fraction of sodium chloride is 10%, and the mass fraction of methanol is 30%.

(3) The wet sodium chloride product was dried to yield 22.25g of finished sodium chloride (sodium chloride content 99.8%).

Example 2

(1) Adding 300g of methanol into 100g of saturated refined brine to separate out sodium chloride crystals under the condition of stirring, and filtering to obtain 25.12g of crude sodium chloride; wherein the stirring speed is 300rpm, and the stirring time is 10 min.

(2) Washing the crude sodium chloride product by adopting 50g of methanol-sodium chloride mixed solution, and removing the solvent to obtain a wet sodium chloride product; in the methanol-sodium chloride mixed solution, the mass fraction of sodium chloride is 15%, and the mass fraction of methanol is 23%.

(3) The wet sodium chloride product was dried to yield 22.98g of finished sodium chloride (sodium chloride content 99.7%).

Example 3

(1) Adding 150g of methanol into 100g of saturated refined brine to separate out sodium chloride crystals under the condition of stirring, and filtering to obtain 22.74g of crude sodium chloride; wherein the stirring speed is 500rpm, and the stirring time is 30 min.

(2) Washing the crude sodium chloride product by using 60g of methanol-sodium chloride mixed solution, and removing the solvent to obtain a wet sodium chloride product; in the methanol-sodium chloride mixed solution, the mass fraction of sodium chloride is 20%, and the mass fraction of methanol is 10%.

(3) The wet sodium chloride product was dried to obtain 20.62g of finished sodium chloride product (sodium chloride content 99.8%).

Comparative example 1

The only difference compared to example 1 is that in comparative example 1 the crude sodium chloride is washed with a saturated sodium chloride solution.

Comparative example 1 yielded 22.74g of finished sodium chloride (sodium chloride content 99.7%).

Comparative example 2

Compared with example 1, the difference is only that in comparative example 2, 30% methanol solution is used for washing the crude sodium chloride.

Comparative example 2 yielded 23.02g of finished sodium chloride (sodium chloride content 99.4%).

Test group

The sodium chloride finished products obtained in the above examples 1-3 and comparative examples 1-2, the sodium chloride crude product obtained in example 1, and commercially available refined salt were subjected to anti-caking performance tests, and the results are shown in tables 1-2.

And (3) anti-caking test: 1000g of each of the finished sodium chloride products obtained in examples 1 to 3 and comparative examples 1 to 2, the crude sodium chloride product obtained in example 1 and commercially available refined salt was weighed, and the weighed sodium chloride products were respectively put into plastic bags, air was removed, the plastic bags were sealed, and the plastic bags were pressed with a 20kg weight for 3 months.

To describe the degree of caking of the salt, 5 grades were assigned, see table 1.

TABLE 1

Degree of caking	Description of phenomena
		Does not agglomerate	The sample is in loose form
First stage	With a small number of pieces loose by touch
		Second stage	Has partial block-shaped objects, and can be naturally dropped and dispersed at the height of 1m
Three-stage	With parts of block-shaped bodies which can be rolled open by hand
		Four stages	Most of the wood hammer blocks and can be easily knocked off by the wood hammer
Five stages	Completely caked and difficult to knock with a wooden hammer

TABLE 2

	Caking grade
		Commercially available refined salt	First stage
Crude sodium chloride in example 1	Four stages
		Example 1	Does not agglomerate
Example 2	Does not agglomerate
		Example 3	Does not agglomerate
Comparative example 1	Three-stage
		Comparative example 2	Second stage

As can be seen from Table 2, the sodium chloride finished products obtained in the embodiments 1-3 of the invention have good anti-caking performance. The sodium chloride finished product obtained in the comparative example 1 has poor anti-caking effect because the form of sodium chloride is changed in the washing process of a saturated sodium chloride solution, which is not beneficial to improving the anti-caking effect; the sodium chloride finished product obtained in the comparative example 2 has poor anti-caking effect because methanol alone has poor washing effect and part of impurities remain, thereby causing easy caking; the anti-caking effect of the crude sodium chloride obtained in example 1 was poor because the crude sodium chloride had high impurity content and poor sphericity, making it more prone to caking.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.