CN111087006B - Novel preparation process for co-production of refined liquid salt and anhydrous sodium sulfate for alkali preparation - Google Patents
Novel preparation process for co-production of refined liquid salt and anhydrous sodium sulfate for alkali preparation Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
- C01D3/08—Preparation by working up natural or industrial salt mixtures or siliceous minerals
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/14—Purification
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/06—Preparation of sulfates by double decomposition
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/06—Preparation of sulfates by double decomposition
- C01D5/10—Preparation of sulfates by double decomposition with sulfates of magnesium, calcium, strontium, or barium
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/16—Purification
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Abstract
The invention relates to the technical field of liquid salt, and particularly discloses a novel preparation process for co-producing refined liquid salt and anhydrous sodium sulfate for preparing alkali. The invention firstly collects the original bittern, firstly carries out microfiltration on the original bittern, then separates the filtered bittern by a nanofiltration membrane to obtain high-nitrate water and low-nitrate water, and adds caustic soda (NaOH) and sodium carbonate (Na) into the low-nitrate water 2 CO 3 ) Reacting, filtering out calcium and magnesium mud by an ultrafiltration membrane after the reaction, collecting refined salt water, adding lime into high-nitrate water to perform a first-stage reaction, introducing flue gas after the first-stage reaction to perform a second-stage reaction, and putting the second-stage reaction into an MVR evaporator to prepare refined salt and anhydrous nitrate. The invention adopts simpler process flow to complete the combination of brine, and simultaneously can ensure excellent impurity removal effect, thereby greatly saving cost.
Description
Technical Field
The invention relates to the technical field of liquid salt, in particular to a novel preparation process of refined liquid salt for alkali preparation.
Background
At present, salt consumption in many developed countries in the world is provided in liquid form, and according to statistics, the proportion of liquid salt in the total amount of industrial salt is 63%, 72% and 60% in the United states, france and Britain respectively, while the liquid salt is almost used in chemical salt, and the proportion of liquid salt in the United states reaches 97%. The development and utilization of liquid salt in China are still at a low level, and only account for less than 20% of industrial salt in China, so that the gap between the liquid salt and developed countries is large.
In 2018, the raw salt for caustic soda mainly comprises solid salt, accounting for 72.4%, and the doped or full-halogen accounting for 27.6% (19.1% doped and 8.5% full-halogen), which indicates that the full-halogen caustic soda is gradually replacing the solid salt to become the trend of the future brine development.
According to research reports, the membrane method brine refining accounts for 94.7%, the membrane method denitration accounts for 68.4%, the chemical method denitration (such as barium method) accounts for 10%, and the double-membrane method liquid salt refining technology is gradually popularized and applied in the brine refining process in the caustic soda industry. With the increasing demand of two alkalis for liquid salt, more and more manufacturers begin to produce and sell refined liquid salt for alkali production in the salt production industry, and the brine preparation process is different due to different requirements on brine indexes and different requirements of the two alkalis and the salt production industry. In the salt-making industry, the general brine purification process for preparing liquid salt adopts a lime flue gas method or a two-alkali method to remove calcium and magnesium, and other impurities such as: sodium sulfate and calcium sulfate are separated by adopting the processes of salt and nitrate co-production, salt and calcium co-production and the like in the salt production process. Because the salt water contains sulfate radical impurities, meanwhile, because the refined brine for salt production normally adopts a gap method, a flocculant is added for solid-liquid separation by a gravity settling method, part of the refined brine for salt production adopts sand filtration or tubular filter filtration, and part of supernatant is directly used, so that the supernatant is directly sold to alkali production enterprises and is not practical or has no market demand, the requirement of the salt water for ion membrane alkali production is met, and a new salt water process (such as the original process shown in the attached figure 2) must be searched.
The brine for preparing alkali in the existing salt factory is used for reference of the brine process in the alkali-making industry, calcium and magnesium are removed by adopting a two-alkali continuous method, refined brine is diluted by adding water until the brine is unsaturated or nearly saturated and enters a nanofiltration and denitrification system, and the refined brine prepared by the two-membrane method is sold to the two-alkali industry. Although the process can meet the alkali making requirement, the process is long, and the high-nitrate salt water obtained by nanofiltration needs to adopt a freezing and hot melting evaporation process, so that the process route is complex, the nitrate making energy consumption is high, and the investment is large. (the process shown in figure 3)
For example, in the cn201110397331.X original halogen denitration production process and production equipment thereof, calcium ions and/or magnesium ions are removed from the original halogen, and then the sulfate ion removal operation is performed on the original halogen from which the calcium ions and/or magnesium ions are removed by using a nanofiltration membrane denitration device.
The raw brine nanofiltration is different from the refined brine nanofiltration or the dilute brine nanofiltration, the components of the brine are different, and the table 1 mainly shows that the raw brine and the refined brine are mainly about 100g/L lower than the dilute brine, the dilute brine is secondarily refined, the content of impurity ions is much lower than that of the raw brine and the refined brine, and therefore, the phenomena of scaling and blockage of the nanofiltration membrane by other impurity ions do not exist during the nanofiltration of the dilute brine. Compared with refined brine, the sodium chloride content of the original brine is the same or similar, but the impurity ion content is greatly different, one is purified, the impurity ions are few, the original brine is not purified and only except SS, algae and fungi, and the impurity ions in the original brine are removed by nanofiltration without changing the ions. In the process of trapping secondary or multivalent ions in the ions, the concentration is increased, and Ca is generated along with the continuous increase of high-concentration water 2 SO 4 ，SrSiO 3 、CaSiO 3 And (3) precipitating to block the membrane pores of the nanofiltration membrane, so that the sulfate radicals are removed by nanofiltration after other impurities except the sulfate radicals are removed without directly adopting original halogen nanofiltration under normal conditions.
The existing impurity removal process basically adopts a caustic soda method or a lime flue gas method, in order to thoroughly remove impurities, the excessive alkali amount of two alkalis needs to be kept, the pH value of refined brine after impurity removal is between 10 and 12, a nanofiltration membrane can only operate under a neutral or weakly acidic condition, and if the nanofiltration membrane operates under an alkaline condition, calcium carbonate and magnesium hydroxide are produced and precipitated along with the increase of the concentration of calcium, magnesium and the like in the concentration process, so that the membrane is scaled; meanwhile, the membrane material is decomposed under alkaline conditions due to the characteristics of the membrane material, and the service life of the membrane is shortened. Therefore, the pH value is generally adjusted to 6-8 by continuously adding hydrochloric acid into the alkaline refined brine, and the pH value is normally controlled to 6.5, so that the phenomenon that the content of calcium carbonate is too high, precipitates and scales are generated to block membrane pores, and the efficiency is reduced is avoided. (see the process shown in the attached figure 3) in detail), so the process route for preparing the refined salt by adopting the traditional method for the brine is complex and the cost is high.
If the original halogen is directly subjected to nanofiltration treatment, the steps of an active carbon tower, security filtration, acid and alkali adjustment and the like are lacked, the impurity removal effect is slightly inferior to that of the original process, especially in SiO 2 、Sr 2+ The treatment results on impurities are particularly obvious, and the expected effect is difficult to achieve.
Aiming at the problems, the invention provides a method for completing the combined preparation of the brine by adopting a simpler process flow, in the process, the brine is not required to be purified and then subjected to nanofiltration, and is directly subjected to nanofiltration, so that the impurity removal effect is ensured, and meanwhile, the cost is greatly saved.
Disclosure of Invention
Aiming at the problems related in the background technology, the invention provides a novel brine process suitable for brine, and the process is simple, convenient to operate, low in production cost and high in product quality.
In order to achieve the technical effects, the invention adopts the following specific technical scheme:
the invention provides a new process for preparing refined salt, anhydrous sodium sulfate and refined salt water from brine.
(1) Collecting raw brine, and carrying out microfiltration on the brine; the purpose of microfiltration is to remove insoluble substances such as fungi, algae, silt and the like in the brine;
preferably, the material of the microfiltration membrane is one or more of ceramic, polypropylene, polycarbonate, polyvinyl chloride, polysulfone, polyvinylidene fluoride or polytetrafluoroethylene.
Preferably, the microfiltration membrane has a filtration precision of 50 to 100nm. Ensuring that the SS of solid insoluble substances in the brine after microfiltration is less than or equal to 0.5mg/L.
The raw brine is mainly prepared from underground salt mine resources by water solution mining, and the pH value is in a range of 6-8.
(2) Separating the microfiltration brine obtained in the step (1) by using a nanofiltration membrane to obtain high-nitrate water and low-nitrate water;
the nanofiltration membrane is used for separating to obtain low-nitrate water (low sulfate radical content) and high-nitrate water (high sulfate radical content), and the low-nitrate water and the high-nitrate water are used for the requirements of different subsequent products.
Preferably, the nanofiltration membrane used is a DT nanofiltration membrane or a DH nanofiltration membrane which is resistant to Ca in high-salt brine 2+ Has a retention rate of 60-70% and Mg 2+ The retention rate of (B) is 70-80%, SO 4 2+ The rejection rate of the sodium chloride is 95-99%, the rejection rate of the sodium chloride is-5- (-10)%, the operation pressure is 2.5-3.2MPa, and the recovery rate is 40-60%.
Wherein the content of calcium, magnesium, silicon and strontium is 0.01-1.0g/L, divalent ions or macromolecules can be intercepted in the nanofiltration membrane separation process, the divalent ions or macromolecules are intercepted in high-nitrate water, and low-nitrate water is obtained to obtain correspondingly pure brine.
(3) Adding caustic soda (NaOH) and soda ash (Na) into low-nitrate water 2 CO 3 ) Reacting, filtering out calcium-magnesium-removed mud by an ultrafiltration membrane after the reaction, and collecting refined salt water;
the reaction is as follows:
MgSO 4 +2NaOH→Mg(OH) 2 ↓+Na 2 SO 4
CaSO 4 +Na 2 CO 3 →Ca CO 3 ↓+Na 2 SO 4
preferably, the addition amount of NaOH is calculated by the content of magnesium ions, and the overbase amount is controlled to be 0.1-0.3g/L.
Na 2 CO 3 The addition amount of the sodium hydroxide is calculated by calcium ion content, and the excessive alkali amount is controlled to be 0.1-0.4g/L.
In the reaction process, after calcium, magnesium, silicon, strontium and the like are intercepted by a nanofiltration membrane, the content of impurity ions in the solution passing through is low and is close to or meets the requirement of saline water for chlor-alkali, and after the reaction of two alkalis, the impurities are further removed, so that the requirements of qualified products are completely met. Meanwhile, the content is low, the consumption of the two alkalis is relatively low, and the auxiliary material cost is saved.
(4) Adding lime into the high-nitrate water to perform a first-stage reaction;
first levelThe reaction is as follows: ca (OH) 2 +MgSO 4 →Mg(OH) 2 ↓+CaSO 4
Ca(OH) 2 +Na 2 SO 4 →2NaOH+CaSO 4
H 2 SiO 3 ←→HSiO 3 -←→SiO 3 2-
Ca(OH) 2 +H 2 SiO 3 →CaSiO 3 ↓+2H 2 O
SrCl 2 +Ca(OH) 2 →Sr(OH) 2 ﹒8H 2 O↓+CaCl 2
The addition amount of lime is related to the content of sulfate ions in the solution and the content of trace magnesium, strontium and silicon, for example, when the content of sulfate ions in the brine is 8-12g/L and the content of magnesium, strontium and silicon is 5-30mg/L, the addition amount of lime is 1.2-1.6g/L, and the dosage is increased along with the increase of the content of impurity ions.
In the first-stage reaction, the removal rate of impurities of magnesium and silicon is 85-95% and the removal rate of strontium is 30-40% by the controlled addition of lime.
(5) And (3) secondary reaction: after the first-stage reaction, the clear halogen is transferred into a second-stage reaction barrel to be introduced into flue gas for second-stage reaction
The secondary reaction is as follows: naOH + CO 2 →Na 2 CO 3
CaSO 4 +Na 2 CO 3 →CaCO 3 ↓+Na 2 SO 4
SrSO 4 +Na 2 CO 3 →Sr CO 3 ↓+Na 2 SO 4
Sr(OH) 2 +SO 2 ＝SrSO 3 ↓+H 2 O
Sr(OH) 2 +CO 2 ＝SrCO 3 ↓+H 2 O
The content of each component of the flue gas is controlled to be CO 2 Volume concentration of 20% and SO 2 The volume concentration is 2 percent, and the rest is nitrogen, oxygen and water vapor. The end point is controlled according to the pH value after the second-stage reaction is finished, when the pH value of the brine reaches 8.6-9.2, the introduction of the flue gas is stopped, andafter stirring was continued for 0.5h, the reaction was allowed to complete.
In conventional flue gas treatment, there is generally no or very little SO 2 Gas, whereas the present invention has found that a certain volume concentration of SO is defined in the flue gas 2 And increasing conventional CO 2 Volume ratio of Sr 2+ The impurity removal rate is 75-85%, and the effect is remarkable.
The invention can also mix refined brine after high-nitre water purification with clarified liquid of low-nitre water to meet the requirements of products with different qualities.
Through the first-stage reaction and the second-stage reaction, impurities in the salt are well removed, the quality of the final salt reaches the research of the original process, and the final salt is difficult to achieve by the traditional process in the aspects of economy, simple operation and the like.
And (5) after the second-stage reaction, putting the mixture into an MVR system to prepare salt, and respectively collecting the salt and the anhydrous sodium nitrate to obtain solid salt and anhydrous sodium nitrate.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention directly nanofilters the original bittern, simplifies the functions of acid and alkali adjustment before and after nanofiltration, active carbon filtration and security filtration, and because the pH value in the original bittern is stable, neutral and influenced by salt content, the concentrated water after filtration adopts a lime flue gas process, thereby not only achieving the purpose of removing impurities and saving the consumption of soda ash, but also limiting the content and pH value of the lime flue gas to ensure that SiO can be removed 2 、Sr 2+ The impurities are removed together, and the medicament and the equipment for removing the trace elements are saved. Meanwhile, because the original halogen is not added with acid or alkali and belongs to a neutral raw material, the acid or alkali does not need to be regulated in the nanofiltration process, and the procedure of regulating the acid or alkali by refined halogen or light salt water is saved. And the problems that pH fluctuation is caused by adjusting acid and alkali, the membrane material is easy to oxidize and decompose under the condition of unstable acid and alkali content and the like are avoided, and the service life of the membrane is prolonged.
(2) The high-nitrate water after nanofiltration saves the purification cost and directly purifies the original brine as SO 4 2- When the content is 8-12g/L, the traditional lime flue gas brine purification method is more economical than a two-alkali method, but after the flue gas is completely introduced, part of soda ash needs to be supplemented to reach the standard; and after passing, sulfuric acid in high-nitrate waterThe root content is high, lime flue gas is used for reaction, soda ash is basically not needed to be added, and the purification cost is saved. By optimizing the process, the silicon and strontium elements in the brine can be removed in the purification process, the original two-alkali process is difficult to achieve, and meanwhile, the process is energy-saving, consumption-reducing, low in operation cost and good in product quality.
(3) The invention directly nano-filters the brine, and greatly saves the cost while ensuring the same impurity removal effect by controlling the addition of lime and the content of each component of flue gas. Compared with freezing and hot melting evaporation, the hot method for extracting the sodium sulfate (MVR) is more energy-saving, short in process flow and more stable in operation.
Drawings
FIG. 1 is a flow chart of a new salt production process of the present invention.
FIG. 2 is a flow chart of a salt-making raw process.
FIG. 3 is a diagram of the original process of refined brine for alkali production.
Detailed Description
The invention will now be described in further detail with reference to fig. 1, in which fig. 3 is a simplified flow diagram:
example 1
(1) Adopting brine, and carrying out microfiltration on the brine, wherein the microfiltration aims to remove insoluble substances such as fungi, algae, silt and the like in the brine to obtain microfiltration pretreated brine, and SS (solid insoluble substance) in the microfiltration brine is less than or equal to 0.5mg/L; through detection, the microfiltered brine comprises the following components: naCl 300g/L, SO 4 2- 10 g/L、Ca 2+ 0.8g/L、Mg 2+ 0.015g/L、SiO 2 10mg/L、Sr 2+ 20mg/L, pH 6.8.
(2) The microfiltration pretreated brine enters a nanofiltration membrane for separation, and the nanofiltration membrane intercepts divalent Ca 2+ 、Mg 2+ 、SO 4 2- 、SiO 2 And Sr 2+ And other macromolecules, and Na + 、Cl - Most of the nano-filtration membranes can pass through the nano-filtration membranes, and the operating pressure is 2.5MPa; separating to obtain high-nitrate water and low-nitrate water;
(3) Adding caustic soda (NaOH) and soda ash (Na) into low-nitrate water 2 CO 3 ) The reaction is carried out, the addition amount of NaOH is magnesiumThe ion content is calculated, the excessive alkali content is controlled to be 0.1g/L, na 2 CO 3 The adding amount of the sodium hydroxide is calculated by the content of calcium ions, the alkali passing amount is controlled to be 0.2g/L, calcium and magnesium are removed through ultrafiltration membrane filtration after reaction, and refined salt water is prepared;
(4) Adding lime into high-nitrate water to perform a primary reaction, wherein the addition amount of the lime is related to the content of sulfate ions in the solution and is also related to the content of trace magnesium, strontium and silicon, the content of sulfate ions in the brine is 22g/L, the content of magnesium, strontium and silicon is 20-40 mg/L, the addition amount of the lime is 1.5-4.0 g/L, and the primary reaction is performed, wherein the removal rate of magnesium and silicon impurities is 88% and the removal rate of strontium is 35%; after the first-stage reaction, the clear halogen is transferred into a second-stage reaction barrel to be introduced into flue gas (the content of each component in the flue gas is controlled to be CO) 2 Volume concentration of 20% SO 2 The volume concentration is 2 percent, and the rest is nitrogen, oxygen and water vapor), performing secondary reaction, stopping introducing lime flue gas when the pH value of the brine reaches 8.8 to precipitate calcium ions in the brine, wherein the removal rate of strontium is 85 percent; clarifying and filtering the reacted brine to prepare refined brine.
(5) Putting filtered refined brine (mainly containing sodium ions, chloride ions and sulfate ions) into a mechanical thermal compression (MVR) evaporative crystallization technology to prepare solid salt (NaCl), heating clear liquid by a multi-stage preheater, then sequentially entering an autoclave, a flash tank and a salt making evaporator tank, heating obtained mother liquor by the preheater, then entering a nitrate making evaporator tank, fully crystallizing the mother liquor, transferring the mother liquor to the salt making evaporator tank by an energy-saving device for recrystallization, and discharging salt slurry from the autoclave and the salt making evaporator tank to enter a centrifuge for dehydration; and similarly, discharging the saltpeter from the saltpeter making tank, dewatering in a centrifugal machine, drying, and conveying to a saltpeter packaging machine through a belt conveying device for packaging and warehousing. And co-producing to obtain refined salt and anhydrous sodium sulfate.
Wherein the temperature of the autoclave is 128 ℃, the pressure is 1.80bar (a), and the autoclave is an evaporative crystallization salt production tank of an MVR system.
The temperature of the flash tank is 103 ℃, the pressure is 3bar (a), the function of reducing temperature and pressure is achieved,
the salt-making evaporating pot is an evaporative crystallization salt-producing pot for salt and nitrate co-production, the temperature is 50 ℃, the pressure is 0.06bar (a),
the nitrate preparing evaporator is an evaporative crystallization nitrate producing tank for salt and nitrate co-production, the temperature is 105 ℃, and the pressure is 0.80bar (a);
the salt slurry discharged from the MVR salt making tank and the salt making tank is dehydrated and dried by a centrifuge to obtain salt products,
the quality of the salt product is detected.
Table 1 chlor-alkali and salt industry brine for nanofiltration having different compositions
Table 2 example 1 main components of high and low saltwater after nanofiltration
Table 3 salt product prepared in example 1
Table 4 the measurement results of the refined brine of example 1 are:
comparative example 1
Comparative example 1 compared to example 1, the differences are: the flue gas is desulfurized and does not contain SO 2 The content of each component in the flue gas is controlled to be CO 2 The volume concentration is 20 percent, and the rest is nitrogen, oxygen and water vapor. The rest of the operation was the same as in example 1.
In this comparative example, the salt slurry discharged from the autoclave and the salt making evaporator was passed through a centrifugeSr in salt product obtained after dehydration and drying 2+ The content of (B) is 65mg/100g.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified. The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all modifications of the above embodiments made according to the technical spirit of the present invention are included in the scope of the present invention.
Claims (5)
1. A new preparation process for co-producing refined salt and anhydrous sodium nitrate by refined liquid salt for alkali preparation is characterized in that: the preparation method comprises the following specific steps:
(1) Collecting raw brine, and carrying out microfiltration on the brine; the filtration precision of the microfiltration membrane is 50-100nm, and the brine after microfiltration comprises the following components: naCl 295-305 g/L, SO 4 2- 8-12 g/L、Ca 2+ 0.6-0.8 g/L、Mg 2+ 0.01-0.15g/L、SiO 2 5-10 mg/L、Sr 2+ 2-25 mg/L, pH 6-8, and the solid insoluble substances in the microfiltered brine reach SS less than or equal to 0.5mg/L; the NaCl content in the brine after microfiltration is 295-305 g/L;
(2) Separating the microfiltration brine obtained in the step (1) by using a nanofiltration membrane to obtain high-nitrate water and low-nitrate water; nanofiltration membrane on Ca in high-salinity brine 2+ 、Mg 2+ 、SO 4 2+ The retention rate of the composite is 60-70%, 70-80% and 95-99% in sequence;
(3) Adding caustic soda and soda ash into the low-nitrate water for reaction, filtering out calcium-magnesium-removed mud through an ultrafiltration membrane after the reaction, and collecting refined brine;
(4) Adding lime into the high-nitrate water to perform a primary reaction, and introducing flue gas into the clear brine after the primary reaction to perform a secondary reaction; controlling the content of each component of the flue gas to be CO 2 Volume concentration of 20% and SO 2 The volume concentration is 2 percent, and the rest is nitrogen, oxygen and water vapor; after the secondary reaction is finished, controlling the end point according to the pH value, stopping introducing the flue gas when the pH value of the brine reaches 8.6 to 9.2, and continuously stirring for 0.5 to 1h to ensure that the reaction is complete;
(5) Putting the mixture into an MVR evaporator after the second-stage reaction to prepare solid salt, and collecting anhydrous sodium nitrate in clear liquid.
2. The novel process for producing refined liquid salt for producing alkali as well as refined salt and anhydrous sodium sulfate according to claim 1, wherein the process comprises the steps of: the microfiltration membrane adopted in the step (1) is made of one or more of ceramic, polypropylene, polycarbonate, polyvinyl chloride, polysulfone, polyvinylidene fluoride or polytetrafluoroethylene.
3. The novel process for producing refined liquid salt for producing alkali as well as refined salt and anhydrous sodium sulfate according to claim 1, wherein the process comprises the steps of: and (3) the nanofiltration membrane in the step (2) is a DT nanofiltration membrane or a DH nanofiltration membrane.
4. The novel process for producing refined liquid salt for producing alkali as well as refined salt and anhydrous sodium sulfate according to claim 1, wherein the process comprises the steps of: the rejection rate of the nanofiltration membrane to sodium chloride is (-10) - (-5)%, the operating pressure is 2.5-3.2MPa, and the recovery rate is 40-60%.
5. The novel process for producing refined liquid salt for producing alkali as well as refined salt and anhydrous sodium sulfate according to claim 1, wherein the process comprises the steps of: the addition amount of NaOH in the step (3) is calculated by the content of magnesium ions, and the alkali excess amount is controlled to be 0.1-0.3g/L; na (Na) 2 CO 3 The addition amount of the sodium hydroxide is calculated by the content of calcium ions, and the excess alkali amount is controlled to be 0.1-0.4g/L.
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| CN112456517A (en) * | 2020-12-08 | 2021-03-09 | 天津渤化永利化工股份有限公司 | Method for treating sulfate radical in salt washing brine of combined-alkali system by using nanofiltration membrane technology |
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| CN104909390A (en) * | 2015-05-25 | 2015-09-16 | 江苏久吾高科技股份有限公司 | Membrane-method coupling lime flue gas brine purification process |
| CN107572554A (en) * | 2017-09-26 | 2018-01-12 | 中盐金坛盐化有限责任公司 | A kind of clean energy-saving type produces salt producing craft |
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| CN104909390A (en) * | 2015-05-25 | 2015-09-16 | 江苏久吾高科技股份有限公司 | Membrane-method coupling lime flue gas brine purification process |
| CN107572554A (en) * | 2017-09-26 | 2018-01-12 | 中盐金坛盐化有限责任公司 | A kind of clean energy-saving type produces salt producing craft |
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Application publication date: 20200501 Assignee: Nanjing Tongchang New Material Research Institute Co.,Ltd. Assignor: CHINASALT JINTAN Co.,Ltd. Contract record no.: X2023320000012 Denomination of invention: A new preparation process of refined liquid salt for alkali production combined with refined salt and anhydrous nitrate Granted publication date: 20221115 License type: Common License Record date: 20230106 |