CN112679021B - Salt-making method by using seawater - Google Patents
Salt-making method by using seawater Download PDFInfo
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- CN112679021B CN112679021B CN202011561318.9A CN202011561318A CN112679021B CN 112679021 B CN112679021 B CN 112679021B CN 202011561318 A CN202011561318 A CN 202011561318A CN 112679021 B CN112679021 B CN 112679021B
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
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Abstract
The invention relates to a method for preparing salt from seawater, which comprises the steps of filtering seawater, adding sodium carbonate and a purifying agent under the heating condition, enabling the purifying agent to act in the seawater to generate a polymer, absorbing nonionic soluble impurities in the seawater by the polymer to form a flocculating substance, filtering under the condition of carbon dioxide, adding a settling agent into filtrate for heating, introducing neutral gas, filtering, reducing impurities, facilitating subsequent sodium chloride crystallization and seawater desalination, concentrating the seawater through a reverse osmosis membrane to obtain concentrated brine and fresh water, finally adding hydrochloric acid into the concentrated brine for acidification, heating and refluxing, and then rapidly cooling to separate out sodium chloride, thereby obtaining salt with less impurities and high purity, and no need of refining the salt in the follow-up process. The salt-making process of the invention has simple operation and low cost, and can desalinate the sea water while making salt, thereby improving the utilization rate of the sea water, and the whole process has no pollution, and the sediment and the waste water generated in the salt-making process can be further utilized.
Description
Technical Field
The invention relates to the field of salt preparation by seawater, in particular to a salt preparation method by seawater.
Background
The sea salt production of human beings has been a long history for thousands of years, the most widely salt production method is the traditional sun-drying method, and in the long-term sea salt production practice, various effective methods, such as hot-pressing salt production technology, vacuum salt production technology, reverse osmosis method, ion exchange membrane electrodialysis method for concentrating sea water salt production technology and the like, are also developed. The electrodialysis method can remove most of salt in the seawater, has no phase change in the desalting process, and has wide application in the fields of seawater desalination and salt preparation. The reverse osmosis process can isolate all the impurities mixed into water, such as bacteria, viruses, heavy metals, micromolecular organic matters, etc., and the quality of the effluent reaches the physicochemical index and the sanitary standard of drinking, so that the water is considered as the high-quality drinking water commonly accepted at present. However, reverse osmosis has high requirement on the quality of the inflowing water, common seawater, especially surface seawater, cannot be directly subjected to reverse osmosis treatment, and high energy consumption is a great difficulty in restricting the application of the reverse osmosis technology.
Currently, the existing single technologies of sea water cooling, sea water desalination, industrial salt production, sea water chemical extraction and the like are quite mature, and a plurality of individual project examples are provided. But the energy consumption of the individual projects is high, the production cost is high, and the discharged byproducts have more impurity components and cause adverse effects on the environment. In addition, the modern seawater is seriously polluted, the impurities in the seawater are numerous, the impurities are difficult to directly remove by the existing seawater salt making technology, and the salt making efficiency and the salt production quality are low.
Disclosure of Invention
Aiming at the problems, the invention provides a method for preparing salt from seawater.
The method is realized according to the following steps:
s1, introducing seawater into a filter tank for filtering;
s2, heating the filtered seawater to 30-40 ℃, sequentially adding sodium carbonate and a purifying agent for continuous heating, separating out flocculate, introducing carbon dioxide, filtering to obtain filtrate, adding a settling agent into the filtrate under the condition of heating and stirring, heating to 70-85 ℃, preserving heat for 30-60 min, introducing neutral gas, filtering to obtain filtrate, and then passing through a reverse osmosis membrane to obtain concentrated brine and fresh water;
s3, adding hydrochloric acid with the volume concentration of 70-80% into the concentrated brine, adjusting the pH to 2-3, heating and refluxing, rapidly cooling, precipitating crystals, and carrying out vacuum filtration to obtain salt.
Further, the filter tank sequentially comprises a first layer, a second layer and a third layer from bottom to top, wherein the first layer is cobblestone, the second layer is ceramsite with the particle size of 2.0-3.0 mm, and the third layer is mesoporous activated carbon with the pore diameter of 10-40 nm.
Further, a water outlet is arranged above the third layer in the filter tank, and a filter screen is arranged at the water outlet.
In the step S2, the purifying agent is silicic acid, sodium hydroxymethyl cellulose and lignin according to the proportion of 5-7: 1:3 by mass ratio.
Further, in the step S2, the mass ratio of the seawater, the sodium carbonate and the purifying agent is 20-30: 1:2.
in the step S2, the sedimentation agent is obtained by mixing sodium carbonate and absolute ethyl alcohol according to the mass ratio of 0.6-1:1.
In step S2, the mass ratio of the filtrate to the sedimentation agent is 6-10:1.
Further, in the step S2, the concentration of the concentrated brine is 26-28 DEG Be ˊ 。
In step S3, the temperature is quickly reduced to be between 80 and 100 ℃ after the reflux reaction is carried out for 20 to 60 minutes, and the temperature is quickly reduced to be between 0 and 10 ℃.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention relates to a method for preparing salt from seawater, which comprises the steps of filtering seawater, adding sodium carbonate and a purifying agent under the heating condition, enabling the purifying agent to act in the seawater to generate a polymer, absorbing nonionic soluble impurities in the seawater by the polymer to form a flocculating substance, filtering under the condition of carbon dioxide, adding a settling agent into filtrate for heating, introducing neutral gas, filtering, reducing impurities, facilitating subsequent sodium chloride crystallization and seawater desalination, concentrating the seawater through a reverse osmosis membrane to obtain concentrated brine and fresh water, finally adding hydrochloric acid into the concentrated brine for acidification, heating and refluxing, and then rapidly cooling to separate out sodium chloride, thereby obtaining salt with less impurities and high purity, and no need of refining the salt in the follow-up process. The salt-making process of the invention has simple operation and low cost, and can desalinate the sea water while making salt, thereby improving the utilization rate of the sea water, and the whole process has no pollution, and the sediment and the waste water generated in the salt-making process can be further utilized.
(2) According to the method, seawater is introduced into a filtering tank to remove insoluble substances under the multiple actions of cobblestones, ceramsite and active carbon, impurities are reduced, nonionic soluble impurities are removed through purification of a purifying agent prepared from silicic acid, sodium hydroxymethyl cellulose and lignin, ionic soluble impurities are removed through a settling agent prepared from sodium carbonate and absolute ethyl alcohol, and finally fresh water and brine with higher concentration can be directly obtained through reverse osmosis membrane concentration.
Detailed Description
In order to better understand the technical content of the present invention, the following provides specific examples to further illustrate the present invention.
Example 1
A method for preparing salt from seawater, comprising the following steps:
s1, introducing seawater into a filter tank for filtering, wherein the filter tank sequentially comprises a first layer, a second layer and a third layer from bottom to top, the first layer is cobblestone, the second layer is ceramsite with the particle size of 2.0-3.0 mm, the third layer is mesoporous activated carbon with the pore diameter of 10-40 nm, a water outlet is arranged above the third layer, and a filter screen is arranged at the water outlet;
s2, heating the filtered seawater to 38 ℃, sequentially adding sodium carbonate and a purifying agent for continuous heating, wherein the mass ratio of the seawater to the sodium carbonate to the purifying agent is 26:1:2, after precipitating the flocculating matter, introducing carbon dioxide, filtering to obtain filtrate, adding a sedimentation agent into the filtrate under the condition of heating and stirring, wherein the mass ratio of the filtrate to the sedimentation agent is 8:1, heating to 85 ℃, preserving heat for 30min, introducing nitrogen gas, filtering to obtain filtrate, and passing the filtrate through a composite reverse osmosis membrane to obtain the product with the concentration of 26-28 DEG Be ˊ Is characterized by comprising concentrated brine and fresh water; wherein, the purifying agent is silicic acid, sodium hydroxymethyl cellulose and lignin according to the proportion of 6:1:3, mixing the materials according to the mass ratio; the sedimentation agent is obtained by mixing sodium carbonate and absolute ethyl alcohol according to the mass ratio of 0.8:1;
s3, adding hydrochloric acid with the volume concentration of 76% into the concentrated brine, adjusting the pH to 2, heating to 95 ℃ for reflux reaction for 30min, rapidly cooling to 5 ℃, precipitating crystals, and carrying out vacuum filtration to obtain salt.
Example 2
A method for preparing salt from seawater, comprising the following steps:
s1, introducing seawater into a filter tank for filtering, paving quartz sand with the particle size of 2.0-3.0 mm in the filter tank, arranging a water outlet above a quartz sand layer, and arranging a filter screen at the water outlet;
s2, heating the filtered seawater to 30 ℃, sequentially adding sodium carbonate and a purifying agent for continuous heating, wherein the mass ratio of the seawater to the sodium carbonate to the purifying agent is 30:1:2, after precipitating the flocculating matter, introducing carbon dioxide, filtering to obtain filtrate, introducing carbon dioxide, adding a settling agent into the filtrate under the condition of heating and stirring, wherein the mass ratio of the filtrate to the settling agent is 10:1, and addingHeat-preserving for 40min at 80 ℃, introducing oxygen gas, filtering to obtain filtrate, and passing the filtrate through a composite reverse osmosis membrane to obtain the product with the concentration of 26-28 DEG Be ˊ Is characterized by comprising concentrated brine and fresh water; wherein, the purifying agent is silicic acid, sodium hydroxymethyl cellulose and lignin according to the proportion of 5:1:3, mixing the materials according to the mass ratio; the sedimentation agent is obtained by mixing sodium carbonate and absolute ethyl alcohol according to the mass ratio of 0.6:1;
s3, adding hydrochloric acid with the volume concentration of 76% into the concentrated brine, adjusting the pH to 2, heating to 100 ℃ for reflux reaction for 20min, rapidly cooling to 10 ℃, precipitating crystals, and carrying out vacuum filtration to obtain salt.
Example 3
Example 3 differs from example 1 in that:
in the step S2, the mass ratio of the seawater to the sodium carbonate to the purifying agent is 18:1:2.
example 4
Example 4 differs from example 1 in that:
in the step S2, the mass ratio of the filtrate to the sedimentation agent is 5:1.
Example 5
Example 5 differs from example 1 in that:
in the step S2, the purifying agent is prepared by mixing ferric polysilicate and zinc polysilicate according to the mass ratio of 1:1.
Example 6
Example 6 differs from example 1 in that:
in the step S2, the sedimentation agent is obtained by mixing lime milk and sodium carbonate according to the mass ratio of 2:1.
Comparative example 1
A conventional salt making method from seawater, comprising the following steps:
s1, filtering and decoloring seawater;
s2, heating seawater, and evaporating and crystallizing to obtain crude salt;
s3, dissolving the crude salt in a barium chloride solution, filtering after precipitating and precipitating, adding sodium hydroxide, filtering after precipitating and precipitating, adding sodium carbonate into the filtrate, filtering after precipitating and precipitating, adding hydrochloric acid with the volume concentration of 76% into the filtrate, adjusting the pH value to 5, heating, evaporating, crystallizing, and carrying out vacuum suction filtration to obtain the salt.
Comparative example 2
Comparative example 2 differs from example 1 in that:
step S2, heating the filtered seawater to 38 ℃, adding sodium carbonate for heating, wherein the mass ratio of the seawater to the sodium carbonate is 23:1, introducing carbon dioxide after precipitation, filtering to obtain filtrate, adding a sedimentation agent into the filtrate under the condition of heating and stirring, keeping the temperature for 30min after heating to 85 ℃, introducing nitrogen, filtering to obtain filtrate, and passing the filtrate through a reverse osmosis membrane to obtain concentrated brine and fresh water with the concentration of 26-28 DEG Be'; wherein the sedimentation agent is obtained by mixing sodium carbonate and absolute ethyl alcohol according to the mass ratio of 0.6:1.
Comparative example 3
Comparative example 3 differs from example 1 in that:
step S2, heating the filtered seawater to 38 ℃, sequentially adding sodium carbonate and a purifying agent for continuous heating, wherein the mass ratio of the seawater to the sodium carbonate to the purifying agent is 26:1:2, filtering to obtain filtrate, adding a settling agent into the filtrate under the condition of heating and stirring, wherein the mass ratio of the filtrate to the settling agent is 8:1, heating to 85 ℃, preserving heat for 30min, introducing nitrogen, filtering to obtain filtrate, and then passing through a reverse osmosis membrane to obtain concentrated brine and fresh water with the concentration of 26-28 DEG Be'; wherein, the purifying agent is silicic acid, sodium hydroxymethyl cellulose and lignin according to the proportion of 6:1:3, mixing the materials according to the mass ratio; the sedimentation agent is obtained by mixing sodium carbonate and absolute ethyl alcohol according to the mass ratio of 0.8:1.
Comparative example 4
Comparative example 4 differs from example 1 in that:
step S2, heating the filtered seawater to 38 ℃, sequentially adding sodium carbonate and a purifying agent for continuous heating, separating out flocculating substances, introducing carbon dioxide, and filtering to obtain filtrate, wherein the mass ratio of the seawater to the sodium carbonate is 26:1:2，The filtrate is subjected to a composite reverse osmosis membrane to obtain concentrated brine and fresh water with the concentration of 26-28 DEG Be'; wherein, the purifying agent is silicic acid, sodium hydroxymethyl cellulose and lignin according to the proportion of 6:1:3 by mass ratio.
Comparative example 5
Comparative example 5 differs from example 1 in that:
and S3, adding hydrochloric acid with the volume concentration of 76% into the concentrated brine, adjusting the pH to 2, heating to 95 ℃ for reflux reaction for 6 hours, separating out crystals, and carrying out vacuum filtration to obtain salt.
Test examples
The prepared salts of the examples and the comparative examples are detected, the physical and chemical indexes of the industrial salt are shown in table 1, and the detection results are shown in table 2;
TABLE 1 Industrial salt physical and chemical indicators
Moisture determination: reference is made to GB/T13025.3-2012 "determination of moisture by general test method for salt manufacturing industry";
water insolubles assay: reference is made to GBT13025.4-2012 "determination of water insoluble by general test methods for salt manufacturing industry";
measurement of total amount of calcium and magnesium ions: reference is made to GB/T13025.6-2012 "determination of calcium and magnesium by general test method for salt manufacturing industry";
and (3) measuring the sulfate radical content: reference is made to GB/T13025.8-2012 "determination of sulfate by general test method for salt manufacturing industry";
sodium chloride content determination: reference is made to GB T5462-2015 Industrial salt.
TABLE 2 detection results
The experimental data show that the salt prepared by the salt preparation process has high quality, high sodium chloride content, low water insoluble matter content, low total calcium and magnesium ions content and low sulfate radical content. Wherein, example 1 is the best scheme of the salt making process of the invention; the filtering tank of the embodiment 2 is only provided with a layer of quartz sand, the filtering effect is poor, and the moisture and water insoluble matters in the salt are more than those of the embodiment 1; in the embodiment 3, the use amount of sodium carbonate and the purifying agent is more, the effect of the purifying agent and the seawater is incomplete, and impurities are increased due to difficulty in removing during filtering; in the embodiment 4, the amount of the sedimentation agent is large, the sedimentation effect is supersaturated, and the content of ionic impurities is increased due to the fact that the rest sedimentation agent is dissolved in brine; example 5 does not use the purifying agent of the invention, has poor purifying effect, low sodium chloride content in salt and more impurities than example 1; the settling agent of example 6 did not use absolute ethanol and had poor settling.
The salt prepared by the conventional salt preparation method in comparative example 1 has low sodium chloride content and various impurities and needs further refining; in the comparative example 2, the salt obtained by treating the seawater without the purifying agent has lower sodium chloride content, and the unpurified brine is directly used for preparing the salt, so that the impurity in the salt is more; comparative example 3, without carbon dioxide, has incomplete filtration of the floc, and contains a large amount of water-insoluble impurities; the salt obtained in comparative example 4 without adding the sedimentation agent has low sodium chloride content and more impurities; comparative example 5 did not cool after heating and refluxing, and was long-lasting, and the sodium chloride content of the prepared salt was low, more water content, and more impurities.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (6)
1. The salt making process with sea water includes the following steps:
s1, introducing seawater into a filter tank for filtering; the filter tank sequentially comprises a first layer, a second layer and a third layer from bottom to top, wherein the first layer is cobblestone, the second layer is haydite with the particle size of 2.0-3.0 mm, and the third layer is mesoporous activated carbon with the pore diameter of 10-40 nm;
s2, heating the filtered seawater to 30-40 ℃, sequentially adding sodium carbonate and a purifying agent for continuous heating, separating out flocculate, introducing carbon dioxide, filtering to obtain filtrate, adding a settling agent into the filtrate under the condition of heating and stirring, heating to 70-85 ℃, preserving heat for 30-60 min, introducing neutral gas, filtering to obtain filtrate, and then passing through a reverse osmosis membrane to obtain concentrated brine and fresh water; the purifying agent is silicic acid, sodium hydroxymethyl cellulose and lignin according to the proportion of 5-7: 1:3, mixing the materials according to the mass ratio; the sedimentation agent is obtained by mixing sodium carbonate and absolute ethyl alcohol according to the mass ratio of 0.6-1:1;
s3, adding hydrochloric acid with the volume concentration of 70-80% into the concentrated brine, adjusting the pH to 2-3, heating and refluxing, rapidly cooling, precipitating crystals, and carrying out vacuum filtration to obtain salt.
2. The method for preparing salt from seawater according to claim 1, wherein in the step S2, the mass ratio of seawater, sodium carbonate and purifying agent is 20-30: 1:2.
3. the method for preparing salt from seawater according to claim 1, wherein in the step S2, the mass ratio of the filtrate to the sedimentation agent is 6-10:1.
4. The method for producing salt from seawater according to claim 1, wherein in step S2, the neutral gas is one of hydrogen, nitrogen and oxygen.
5. The method for preparing salt from seawater according to claim 1, wherein in step S2, the concentration of the concentrated brine is 26-28 ° Be ˊ 。
6. The method for preparing salt from seawater according to claim 1, wherein in the step S3, the temperature is rapidly reduced to 0-10 ℃ after the reflux reaction is performed for 20-60 min after heating to 80-100 ℃ after heating and refluxing.
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| CN113979451A (en) * | 2021-11-05 | 2022-01-28 | 山东岱岳制盐有限公司 | Preparation method of ecological well mineral salt |
| CN114314612A (en) * | 2021-12-16 | 2022-04-12 | 唐山市银海食盐有限公司 | Production process for regulating and controlling sea salt crystal morphology |
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