CN111518525A - Method and system for preparing binary molten salt - Google Patents
Method and system for preparing binary molten salt Download PDFInfo
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Abstract
A method for preparing binary molten salt comprises a first step S1 of mixing potassium hydroxide and sodium hydroxide solution to obtain a first mixed solution; a second step S2 of adding a nitric acid solution into the first mixed solution until the pH value is 6.5-7 to obtain a second mixed solution; a third step S3 of evaporating and concentrating the second mixed solution to obtain a third mixed solution; and a fourth step S4, spraying slurry and granulating the third mixed solution to obtain binary molten salt. The invention improves the mixing effect of the binary molten salt, and ensures uniform granulation; the reaction is controllable, the energy consumption and the time consumption of evaporation concentration are reduced, and the production efficiency is improved; evaporation concentration is linked with guniting granulation, redundant nitric acid is directly removed, and the purity of the binary molten salt is increased; can be continuously and stably produced.
Description
Technical Field
The invention relates to the field of molten salt production, in particular to a production technology for preparing binary molten salt.
Background
In the nitrate binary molten salt, the melting point of the binary molten salt is 220 ℃ and the working temperature can reach 560 ℃ after the potassium nitrate and the sodium nitrate are mixed according to the mass component ratio of 40% to 60%, which is incomparable with the traditional heat transfer media such as hydrocarbon, heat-conducting oil and the like, and the binary molten salt has a certain application basis in CSP power stations and has the characteristics of low cost, long service life and good heat exchange performance.
In the prior art, 40% of molten salt-grade potassium nitrate and molten salt-grade sodium nitrate are added: 60 wt% of the binary molten salt is prepared by mixing, wherein a large amount of single salt analysis and detection and calculation processes are required in the process of preparing the molten salt grade potassium nitrate and the molten salt grade sodium nitrate, and the process is complicated; in addition, a large amount of material resources and manpower are wasted in the molten salt mixing process, material waste and pollution are easily caused, and the obtained binary molten salt system is not uniform.
Therefore, a method for preparing the nitrate binary molten salt is needed, which simplifies the operation, improves the preparation efficiency, and improves the product performance, so as to provide the binary molten salt with excellent quality and stable performance.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for preparing a binary molten salt, comprising, in a first step S1, mixing potassium hydroxide and sodium hydroxide solution to obtain a first mixed solution; a second step S2 of adding a nitric acid solution into the first mixed solution until the pH value is 6.5-7 to obtain a second mixed solution; a third step S3 of evaporating and concentrating the second mixed solution to obtain a third mixed solution; and a fourth step S4, spraying slurry and granulating the third mixed solution to obtain binary molten salt.
According to one embodiment of the invention, the concentration of the potassium hydroxide and sodium hydroxide solution is 30-33% by mass.
According to one embodiment of the invention, the nitric acid solution is a dilute nitric acid solution with a mass percentage concentration of 45%.
According to one embodiment of the present invention, the third mixed solution has a mass percentage concentration of 66 to 69%.
According to one embodiment of the invention, the evaporative concentration operation employs four-effect falling film evaporation.
According to one embodiment of the invention, the drying temperature of the spray granulation is 250-300 ℃.
According to one embodiment of the invention, the drying temperature of the guniting granulation is 265 ℃.
According to an embodiment of the present invention, in the first step S1, a potassium hydroxide solution with a mass percentage concentration of 32% and a sodium hydroxide solution with a mass percentage concentration of 32% are mixed in a volume ratio of 0.81:1, and are uniformly stirred to obtain a first mixed solution; in the second step S2, adding a dilute nitric acid solution with a mass percentage concentration of 45% to the first mixed solution, and neutralizing the mixture according to a volume ratio of 0.98:1 until the pH value is 6.5-7 to obtain a second mixed solution; in the third step S3, evaporating and concentrating the second mixed solution to obtain a third mixed solution with the mass percentage concentration of 66-69%; in the fourth step S4, the granulated binary molten salt is prepared by spraying and granulating the third mixed solution at a granulation drying temperature of 265 ℃, wherein the ratio of potassium nitrate to sodium nitrate is 40%: 60% w.
According to another aspect of the invention, a system for preparing binary molten salt is provided, which comprises a first device 1, a second device and a third device, wherein the first device is used for uniformly mixing potassium hydroxide and sodium hydroxide solution to obtain a first mixed solution; a second device 2, configured to add a nitric acid solution to the first mixed solution until the pH value is 6.5 to 7, so as to obtain a second mixed solution; a third device 3, configured to evaporate and concentrate the second mixed solution to obtain a third mixed solution; and the fourth device 4 is used for spraying and granulating the fourth mixed solution to obtain the binary molten salt.
According to another aspect of the invention, a binary molten salt is provided, which is prepared by the method of any one of the above.
According to the invention, the sodium hydroxide and the potassium hydroxide are mixed in a solution form, so that the sodium and the potassium are uniformly mixed, the mixing effect of the binary molten salt is improved, and the granulation is uniform; the micro-excess of nitric acid and the coexistence of potassium and sodium ions prevent hydroxide from being brought into the product to influence the product quality; the sight glass is prevented from being damaged by hydroxyl; the setting of each concentration enables the reaction to be controllable, reduces the energy consumption and time consumption of evaporation concentration and improves the production efficiency; evaporation concentration is linked with guniting granulation, redundant nitric acid is directly removed, and the purity of the binary molten salt is increased. The method is easy to control and can be used for continuous and stable production.
Drawings
FIG. 1 is a schematic diagram of a procedure for preparing a binary molten salt;
FIG. 2 is a schematic diagram of a system for making a binary molten salt; and
FIG. 3 is a flow chart for preparing a binary molten salt.
Detailed Description
In the following detailed description of the preferred embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific features of the invention, such that the advantages and features of the invention may be more readily understood and appreciated. The following description is an embodiment of the claimed invention, and other embodiments related to the claims not specifically described also fall within the scope of the claims.
Fig. 1 shows a schematic diagram of a procedure for preparing a binary molten salt.
As shown in fig. 1, a method for preparing a binary molten salt includes, in a first step S1, mixing a potassium hydroxide solution and a sodium hydroxide solution to obtain a first mixed solution; a second step S2 of adding a nitric acid solution into the first mixed solution until the pH value is 6.5-7 to obtain a second mixed solution; a third step S3 of evaporating and concentrating the second mixed solution to obtain a third mixed solution; and a fourth step S4, spraying slurry and granulating the third mixed solution to obtain binary molten salt.
The potassium hydroxide solution and the sodium hydroxide solution can be produced by an electrolytic method, wherein the mass percentage concentration of chloride ions is less than 0.005%.
In the invention, the sodium hydroxide and the potassium hydroxide are mixed in a solution form, so that sodium ions and potassium ions are uniformly mixed in the same solution system. The equipment for uniformly mixing the potassium hydroxide solution and the sodium hydroxide solution can adopt a reaction kettle, in particular a reaction kettle with a stirring function. Moreover, the proportion of the sodium hydroxide and the potassium hydroxide can be flexibly adjusted according to the requirement of the binary molten salt. For example, after the concentrations of the potassium hydroxide solution and the sodium hydroxide solution are determined, the flow rates of the two solutions into the reaction kettle are respectively controlled, so that the ratio of the two solutions can be controlled.
In the first mixed solution, the ratio of sodium hydroxide to potassium hydroxide can be controlled, and when nitric acid is added for neutralization, the adding amount of the nitric acid can be set according to the molar ratio of the sum of potassium ions and sodium ions to the nitric acid of 1: 1. The second mixed solution mainly contains potassium nitrate, sodium nitrate and a trace amount of nitric acid.
However, in the present invention, the amount of nitric acid needs to be slightly excessive, that is, the pH of the second mixed solution is within a range of 6.5 to 7. The nitric acid is excessive in a small amount, so that on one hand, hydroxide radicals of potassium hydroxide and sodium hydroxide are fully reacted, and the influence on the product quality caused by the fact that the hydroxide radicals enter the final binary molten salt product is prevented; the hydroxyl is prevented from reacting with the sight glass (the main component of silicate) of the evaporation equipment to cause damage to the sight glass; and (3) carrying out an evaporation concentration process on the second mixed solution, wherein the evaporation temperature is preferably 120-130 ℃. However, in the present invention, the use of a small excess of nitric acid results in a pH of the second mixture of 6.5 to 7, thereby reducing the presence of hydroxyl radicals in the final product. The evaporation temperature in the present invention can be suitably relaxed relative to the prior art, and is preferably 120 ℃ to 130 ℃.
In the third mixed solution, the mass percent of potassium nitrate and sodium nitrate is improved, and the third mixed solution can be used as slurry for spraying granulation. Wherein, potassium nitrate and sodium nitrate remain the misce bene state throughout, mix for the potassium nitrate and the sodium nitrate that generate the monomer of fused salt level separately, reduced extra energy consumption, the effect of mixing is that the monomer mixes hardly to reach moreover, has promoted the mixed effect.
The spray granulation refers to a process of spraying moisture (a general term for a liquid capable of being vaporized) in slurry (a mixture, a solution and a solute) into equipment, vaporizing and separating the moisture in the slurry by using a heating and pressure-pumping method, and then forming the remained solid which is not vaporized (under a certain condition) into granules, namely spray granulation.
In the present invention, it is preferable to use a spray granulation method, and the evaporable substance in the solution is further removed by heat treatment in the granulation process.
In the invention, two steps of evaporation concentration and slurry spraying granulation are adopted, so that the excessive trace nitric acid in the solution is completely consumed, and the quality of the final binary molten salt is purer.
According to one embodiment of the invention, the concentration of the potassium hydroxide and sodium hydroxide solution is 30-33% by mass.
At present, the mass percentage of the common products for producing sodium hydroxide and potassium hydroxide by an electrolytic method can reach about 30 percent, namely, the raw materials of the invention have wide sources and good sources.
In the invention, sodium hydroxide, potassium hydroxide and nitric acid are adopted for neutralization reaction, and the mass percentage concentration of the potassium hydroxide solution and the sodium hydroxide solution is preferably adopted to be 30-33%, so that the neutralization reaction can be controlled, and the influence of violent reaction on equipment is avoided. For example, when the concentration is too high, the acid-base neutralization is exothermic, the reaction is severe, and the equipment is impacted. On the other hand, when the concentration is too low, the amount of water is large, which increases the energy consumption and time required for evaporation in the subsequent step.
Therefore, the concentration of the potassium hydroxide solution and the sodium hydroxide solution is preferably 30-33% by mass, so that the reaction is easy to control; so that the subsequent evaporation is energy-saving and efficient; the raw materials are easy to obtain, and the cost is reduced.
According to one embodiment of the invention, the nitric acid solution is a dilute nitric acid solution with a mass percentage concentration of 45%.
According to the invention, the concentration of the nitric acid enables the reaction to be controllable, the burden of a subsequent evaporation process is reduced, and meanwhile, the concentration meets the requirement of the degree of reflection. For example: when the concentration is too low, a large amount of nitric acid solution is introduced to sufficiently neutralize hydroxide, which increases energy consumption and time for the evaporation process. When the concentration is too high, the nitric acid is evaporated, the reaction is violent, and the risk of uncontrollable reaction and the like is caused.
According to one embodiment of the present invention, the third mixed solution has a mass percentage concentration of 66 to 69%.
During evaporation and concentration, the concentration of the third mixed solution reaches 66-69%, and the requirement of spraying granulation can be met.
According to one embodiment of the invention, the evaporative concentration operation employs four-effect falling film evaporation.
The multiple-effect falling film evaporator is characterized in that feed liquid is added from an upper pipe box of a heating chamber of the falling film evaporator, is uniformly distributed into each heat exchange pipe through a liquid distribution and film forming device, and flows from top to bottom in a uniform film shape under the action of gravity, vacuum induction and airflow. In the flowing process, the feed liquid is heated and vaporized by the shell pass heating medium, the generated steam and the liquid phase enter a separation chamber of the evaporator together, the gas and the liquid are fully separated, the steam enters the next-effect evaporator as the heating medium, thus realizing multi-effect operation, and the liquid phase is discharged from the separation chamber.
The four-effect falling film evaporation device is adopted, steam heating is uniform, the feed liquid is liquid film evaporation, the heat transfer efficiency is high, the heating time is short, the evaporation process is carried out under the action of vacuum, the purity of the material is ensured, and the evaporation temperature is reduced.
According to one embodiment of the invention, the drying temperature of the spray granulation is 250-300 ℃.
In the invention, the potassium nitrate and the sodium nitrate are uniformly mixed before granulation and are in the third mixed solution system, so the tolerance to high temperature is higher than that of potassium nitrate monomer, and the drying temperature can be properly controlled for quick slurry spraying granulation. The drying temperature is preferably 250-300 ℃.
Preferably, the drying temperature of the spray granulation is 265 ℃.
According to an embodiment of the present invention, in the first step S1, a potassium hydroxide solution with a mass percentage concentration of 32% and a sodium hydroxide solution with a mass percentage concentration of 32% are mixed in a volume ratio of 0.81:1, and are uniformly stirred to obtain a first mixed solution; in the second step S2, adding a dilute nitric acid solution with a mass percentage concentration of 45% to the first mixed solution, and neutralizing the mixture according to a volume ratio of 0.98:1 until the pH value is 6.5-7 to obtain a second mixed solution; in the third step S3, evaporating and concentrating the second mixed solution to obtain a third mixed solution with the mass percentage concentration of 66-69%; in the fourth step S4, the granulated binary molten salt is prepared by spraying and granulating the third mixed solution at a granulation drying temperature of 265 ℃, wherein the ratio of potassium nitrate to sodium nitrate is 40%: 60% w.
In the present invention, the ratio of potassium nitrate to sodium nitrate in the target product may be first set, for example: the ratio of potassium nitrate to sodium nitrate is 40%: 60% w.
The molar ratio of potassium to sodium is obtained from the above ratio, and the raw materials may be prepared in accordance with the molar ratio. For example: selecting a sodium hydroxide solution and a potassium hydroxide solution with the mass percentage concentration of 32%, and limiting the molar ratio of potassium ions to sodium ions by a specific volume ratio of 0.81:1, wherein 0.81:1 is obtained by conversion according to the molar ratio of potassium to sodium in a target product.
However, the concentration of 32% and the concentration of 45% are selected for the nitric acid in the invention, so as to ensure the controllability of the reaction and reduce the influence of the heat release of the neutralization reaction on equipment and neutralization; meanwhile, the energy consumption and time of the evaporation and concentration process are reduced.
According to the invention, as the evaporation concentration process is adopted to connect the spraying granulation, the evaporation concentration process can be properly reduced only when the concentration of the third mixed solution reaches 66-69%, and the burden of the evaporation process is avoided when the evaporation concentration requirement is high.
Fig. 2 shows a schematic diagram of a system for preparing binary molten salt.
As shown in fig. 2, according to another aspect of the present invention, there is provided a system for preparing binary molten salt, comprising a first apparatus 1 for mixing potassium hydroxide and sodium hydroxide solution to obtain a first mixed solution; a second device 2, configured to add a nitric acid solution to the first mixed solution until the pH value is 6.5 to 7, so as to obtain a second mixed solution; a third device 3, configured to evaporate and concentrate the second mixed solution to obtain a third mixed solution; and the fourth device 4 is used for spraying and granulating the fourth mixed solution to obtain the binary molten salt.
The first device 1 can use pipelines to separately transport the potassium hydroxide solution and the sodium hydroxide solution to a mixing container, for example, a first pipeline transports the potassium hydroxide solution, and a second pipeline transports the sodium hydroxide solution to a stirring kettle, a reaction kettle, etc. In the second apparatus 2, the nitric acid solution may be transferred to the mixing vessel by a pipe, for example, a third pipe may transfer the nitric acid solution to a stirring tank, a reaction tank, or the like. Since the concentration of each solution is known, the ratio can be controlled by only controlling the flow in each pipeline.
The third device 3 can adopt any existing or future-invented evaporation concentration equipment, and the invention preferably adopts a multi-effect falling film evaporation device.
The fourth device 4 may be any existing or future-invented slurry-spraying granulation equipment, and the invention is not limited thereto.
According to another aspect of the invention, a binary molten salt is provided, which is prepared by the method of any one of the above.
According to the invention, the sodium hydroxide and the potassium hydroxide are mixed in a solution form, so that the sodium and the potassium are uniformly mixed, the mixing effect of the binary molten salt is improved, and the granulation is uniform; the micro-excess of nitric acid and the coexistence of potassium and sodium ions prevent hydroxide from being brought into the product to influence the product quality; the sight glass is prevented from being damaged by hydroxyl; the setting of each concentration enables the reaction to be controllable, reduces the energy consumption and time consumption of evaporation concentration and improves the production efficiency; evaporation concentration is linked with guniting granulation, redundant nitric acid is directly removed, and the purity of the binary molten salt is increased.
Example one
FIG. 3 shows a flow chart for preparing binary molten salt, wherein a potassium hydroxide solution with a mass percentage concentration of 32.09% and a sodium hydroxide solution with a mass percentage concentration of 32.1% are mixed according to a ratio of 0.81:1, and are uniformly stirred to obtain a binary alkali mixed solution (a first mixed solution); neutralizing the binary alkali mixed solution (first mixed solution) with a dilute nitric acid solution with the mass percent concentration of 45% according to the square ratio of 0.98:1 to form a second mixed solution with the pH value of 6.5-7 and the mass percent concentration of 32.1%; evaporating and concentrating the second mixed solution to obtain a third mixed solution with the mass percent concentration of 67%; the third mixed solution is subjected to spray granulation at the granulation drying temperature of 265 ℃ to prepare a final product, and the final product can be directly used as potassium nitrate of the photo-thermal power generation heat storage medium in the molten salt market: sodium nitrate (40%: 60% wt) granular binary molten salt.
Through detection, the potassium nitrate prepared by the method in the embodiment: in the granular binary molten salt of sodium nitrate (40%: 60% wt), the dry basis mass fraction is: 39.83 percent of potassium nitrate by mass; the mass fraction of sodium nitrate is 59.73%; the water mass fraction is 0.004%; the mass fraction of the water-insoluble substances is 0.005%; chloride (as Cl)–Calculated) the mass fraction is 0.004 percent; sulfate (in SO)4 2-Calculated) the mass fraction is 0.004 percent; carbonate (with CO)3 2-Calculated) the mass fraction is 0.009%; nitrite (in NO)2 –Calculated) mass fraction of 0.005%; hydroxide (with OH)–Calculated) the mass fraction is 0.001 percent; ammonium salt (as NH)4 +Calculated) the mass fraction is 0.001 percent; ca2+The mass fraction is 0.004%; mg (magnesium)2+0.003% by mass of Fe3+The mass fraction was 0.0005%. Meets the standard of binary molten salt which can be used in the molten salt market.
Example two
According to the flow chart shown in fig. 3, a potassium hydroxide solution with a mass percentage concentration of 31.8% and a sodium hydroxide solution with a mass percentage concentration of 32.5% are mixed according to a formula ratio of 0.83:1, and are uniformly stirred to obtain a dibasic alkali mixed solution (a first mixed solution); neutralizing the binary alkali mixed solution (first mixed solution) with a dilute nitric acid solution with the mass percentage concentration of 45.17% according to the square ratio of 0.98:1 to form a second mixed solution with the pH value of 6.5-7 and the mass percentage concentration of 32.1%; evaporating and concentrating the second mixed solution to obtain a third mixed solution with the mass percent concentration of 67%; the third mixed solution is subjected to guniting granulation at the granulation drying temperature of 270 ℃ to prepare a final product, and the final product can be directly used as potassium nitrate of the photo-thermal power generation heat storage medium in the molten salt market: sodium nitrate (40%: 60% wt) granular binary molten salt.
Through detection, the potassium nitrate prepared by the method in the embodiment: in the granular binary molten salt of sodium nitrate (40%: 60% wt), the dry basis mass fraction is: 39.84 percent of potassium nitrate by mass; the mass fraction of sodium nitrate is 59.81 percent; the mass fraction of water is 0.003 percent; the mass fraction of water-insoluble substances is 0.008 percent; chloride (as Cl)–Calculated) the mass fraction is 0.007%; sulfate (in SO)4 2-Calculated) the mass fraction is 0.005 percent; carbonate (with CO)3 2-Calculated) the mass fraction is 0.004 percent; nitrite (in NO)2 –Calculated) 0.007% of mass fraction; hydroxide (with OH)–Calculated) the mass fraction is 0.001 percent; ammonium salt (as NH)4 +Calculated) the mass fraction is 0.001 percent; ca2+The mass fraction is 0.004%; mg (magnesium)2+0.001% by mass of Fe3+The mass fraction is 0.0004%. Meets the standard of binary molten salt which can be used in the molten salt market.
EXAMPLE III
According to the flow chart shown in fig. 3, a potassium hydroxide solution with a mass percentage concentration of 32.1% and a sodium hydroxide solution with a mass percentage concentration of 32.7% are mixed according to a formula ratio of 0.80:1, and are uniformly stirred to obtain a binary alkali mixed solution (a first mixed solution); neutralizing the binary alkali mixed solution (first mixed solution) with a dilute nitric acid solution with the mass percentage concentration of 44.9% according to the square ratio of 0.98:1 to form a second mixed solution with the pH value of 6.5-7 and the mass percentage concentration of 32.1%; evaporating and concentrating the second mixed solution to obtain a third mixed solution with the mass percent concentration of 67%; the third mixed solution is subjected to guniting granulation at the granulation drying temperature of 270 ℃ to prepare a final product, and the final product can be directly used as potassium nitrate of the photo-thermal power generation heat storage medium in the molten salt market: sodium nitrate (40%: 60% wt) granular binary molten salt.
Through detection, the potassium nitrate prepared by the method in the embodiment: in the granular binary molten salt of sodium nitrate (40%: 60% wt), the dry basis mass fraction is: 39.78 percent of potassium nitrate by mass; the mass fraction of sodium nitrate is 59.74 percent; the mass fraction of water is 0.002%; the mass fraction of the water-insoluble substances is 0.005%; chloride (as Cl)–Calculated) the mass fraction is 0.004 percent; sulfate (in SO)4 2-Calculated) the mass fraction is 0.004 percent; carbonate (with CO)3 2-Calculated) the mass fraction is 0.005 percent; nitrite (in NO)2 –Calculated) the mass fraction is 0.006%; hydroxide (with OH)–Calculated) the mass fraction is 0.001 percent; ammonium salt (as NH)4 +Calculated) the mass fraction is 0.001 percent; ca2+The mass fraction is 0.004%; mg2+0.001% by mass of Fe3+The mass fraction was 0.0005%. Meets the standard of binary molten salt which can be used in the molten salt market.
The invention combines a neutralization method to directly prepare potassium nitrate: granular binary molten salt of sodium nitrate (40%: 60% wt) and providing a series of treatment steps on the neutralization product binary salt, enabling the direct production of potassium nitrate: the granular binary molten salt of sodium nitrate (40%: 60% wt) has very good industrial value. The process method disclosed by the invention is simple and efficient in operation process, very easy to control all steps and parameters, capable of realizing automatic production by adopting all machinery and equipment, strong in safety, suitable for continuous, stable and rapid production of binary molten salt, higher in economic benefit and beneficial to large-scale popularization. And finally, the binary molten salt product completely meets all indexes of the photo-thermal power generation heat storage medium.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.
Claims (10)
1. A method for preparing binary molten salt comprises the following steps,
a first step (S1) of uniformly mixing potassium hydroxide and sodium hydroxide solutions to obtain a first mixed solution;
a second step (S2) of adding a nitric acid solution into the first mixed solution until the pH value is 6.5-7 to obtain a second mixed solution;
a third step (S3) of evaporating and concentrating the second mixed solution to obtain a third mixed solution;
and a fourth step (S4) of spraying and granulating the third mixed solution to obtain binary molten salt.
2. The method according to claim 1, wherein the concentration of the potassium hydroxide and sodium hydroxide solution is 30-33% by mass.
3. The method of claim 1, wherein the nitric acid solution is a dilute nitric acid solution having a concentration of 45% by mass.
4. The method according to claim 1, wherein the third mixed solution has a mass percentage concentration of 66-69%.
5. The method according to claim 1, wherein the evaporative concentration operation employs a four-effect falling film evaporation.
6. The method according to claim 1, wherein the drying temperature of the spray granulation is 250-300 ℃.
7. The method of claim 1, wherein the drying temperature of the guniting granulation is 265 ℃.
8. The method according to claim 1, wherein in the first step (S1), a 32% by mass concentration potassium hydroxide solution and a 32% by mass concentration sodium hydroxide solution are mixed in a volume ratio of 0.81:1, and the mixture is stirred uniformly to obtain a first mixed solution;
in the second step (S2), adding a dilute nitric acid solution with a mass percentage concentration of 45% to the first mixed solution in a volume ratio of 0.98:1 for neutralization until the pH value is 6.5-7, so as to obtain a second mixed solution;
in the third step (S3), evaporating and concentrating the second mixed solution to obtain a third mixed solution with the mass percent concentration of 66-69%;
in the fourth step (S4), the granulated binary molten salt is prepared by spraying and granulating the third mixed solution at a granulation drying temperature of 265 ℃, wherein the ratio of potassium nitrate to sodium nitrate is 40%: 60% w.
9. A system for preparing binary molten salt comprises,
the first device (1) is used for uniformly mixing potassium hydroxide and sodium hydroxide solution to obtain a first mixed solution;
a second device (2) for adding a nitric acid solution into the first mixed solution until the pH value is 6.5-7 to obtain a second mixed solution;
a third device (3) for evaporating and concentrating the second mixed solution to obtain a third mixed solution;
and the fourth device (4) is used for spraying and granulating the fourth mixed solution to obtain the binary molten salt.
10. A binary molten salt prepared by the method of any one of claims 1 to 8.
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| CN106219578A (en) * | 2016-07-22 | 2016-12-14 | 中国科学院青海盐湖研究所 | A kind of preparation method of water solublity potassium salt |
| CN106698483A (en) * | 2017-01-19 | 2017-05-24 | 青海盐湖工业股份有限公司 | Method for producing molten salt-grade sodium nitrate |
| CN107128953A (en) * | 2017-06-19 | 2017-09-05 | 青海盐湖工业股份有限公司 | A kind of method for producing fused salt level potassium nitrate |
| CN108584991A (en) * | 2018-05-04 | 2018-09-28 | 中国成达工程有限公司 | A kind of low chlorine photo-thermal fused salt production technology and process units |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106219578A (en) * | 2016-07-22 | 2016-12-14 | 中国科学院青海盐湖研究所 | A kind of preparation method of water solublity potassium salt |
| CN106698483A (en) * | 2017-01-19 | 2017-05-24 | 青海盐湖工业股份有限公司 | Method for producing molten salt-grade sodium nitrate |
| CN107128953A (en) * | 2017-06-19 | 2017-09-05 | 青海盐湖工业股份有限公司 | A kind of method for producing fused salt level potassium nitrate |
| CN108584991A (en) * | 2018-05-04 | 2018-09-28 | 中国成达工程有限公司 | A kind of low chlorine photo-thermal fused salt production technology and process units |
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