CN106517097B - Molten salt deoxidation method and deoxidized molten salt - Google Patents
Molten salt deoxidation method and deoxidized molten salt Download PDFInfo
- Publication number
- CN106517097B CN106517097B CN201510570785.0A CN201510570785A CN106517097B CN 106517097 B CN106517097 B CN 106517097B CN 201510570785 A CN201510570785 A CN 201510570785A CN 106517097 B CN106517097 B CN 106517097B
- Authority
- CN
- China
- Prior art keywords
- molten salt
- fluoride
- carbon
- chloride
- time
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
The invention discloses a molten salt deoxidation method and a deoxidized molten salt. Which comprises the following steps: introducing carbon into the molten salt, heating to melt the molten salt for the first time under a vacuum condition, preserving heat for the first time, cooling for the first time, heating to melt the molten salt for the second time, preserving heat for the second time, and cooling for the second time; the fused salt is fluoride fused salt and/or chloride fused salt. The deoxidation process has high deoxidation efficiency, is safe, reliable, controllable, simple and easy to operate, removes products reduced by carbon in a gas form without accumulation, removes nitrate radical, sulfate radical, free oxygen and oxygen free radical in the molten salt, and is beneficial to industrial production; if HF-H is present later2When molten salt is treated, the anhydrous steam expansion molten salt is violently boiled, and the phenomenon of pipeline blockage and molten salt loss caused by boiling are caused.
Description
Technical Field
The invention particularly relates to a deoxidation method of chloride molten salt and/or fluoride molten salt and deoxidized molten salt.
Background
The molten salt refers to a molten mass formed after the salt is melted or a solid formed after the molten mass is cooled. In general, in a high temperature state, a molten salt is called a melt, and in a low temperature solidification state, it is called a solid solution.
During the preparation of uranium-bearing fluoride fused salts, several impurities are self-carried by the raw material, such as sulfur (mostly in SO)4 2-Form), nitrate radical, oxygen radical, etc., and due to partial fluoride, the molten salt has hygroscopic propertiesAnd the water content can be up to 0.4%. The uranium and zirconium fluoride fused salt also contains ZrO2Or ZrOF2，UF4Then contains a small amount of water, about 1% hexavalent U (which may be in the molecular form UO)2F2) And trace amount of UO2The oxygen in the molten salt feed is present mainly in the form of O2-、OH-、MOny-And the like. At high temperature, if free oxygen and oxygen free radicals, oxygen-containing acid radicals, sulfur ions and the like in the molten salt exceed limit values, the molten salt not only has quite strong corrosivity on a container, but also can cause precipitation of component elements of the molten salt, so that the removal of the oxygen element in the molten salt below the limit value is a precondition and a basis for application of the molten salt.
At present, HF-H is mainly adopted in the deoxidation method of fluoride fused salt2The principle of the bubbling method is as follows:
the oxygen removed by the reaction is removed in the form of water vapor, however, the density of the water vapor is 0.6kg/m at 100 ℃3That is, 0.6g of water will produce 1L of gas volume, the volume expansion is about 1600 times, therefore, it can be known that, at 500 ℃ or even higher temperature, the volume expansion after water vaporization will be measured by thousands of times, even if the water generated by the reaction of HF and oxygen is very little, the phenomenon of violent boiling of fused salt will also be caused, so that the fused salt is carried to the top of the container and the gas outlet end along with the gas, the fused salt is condensed because the temperature of the gas outlet end is low, and then the gas outlet pipeline is blocked, even because the gas outlet pipeline is blocked, the pressure in the high-temperature kettle rises suddenly, when the gas pressure is greater than the gas inlet pressure, the fluoride fused salt is refluxed to the vent pipe, and the vent pipe. This is HF-H2The biggest defect of the bubbling deoxidation process. Furthermore, HF-H2The bubbling deoxidation purification method cannot remove oxygen in nitrate radical or phosphate radical, so that the total oxygen cannot be reduced continuously and reaches a limit value. For uranium-containing fluoride fused salts, inBlast-in H2In the process, the existence of nitrate radical will result in UO2Precipitate, as shown in equation (3), and thus nitrate needs to be removed.
Not only O is present in the fluoride fused salt2-、OH-、MOny-Etc. since the fluoride raw material is heated to be molten, a large amount of oxygen radicals and free oxygen are generated in the melt, no matter H is adopted2Or HF will produce a larger amount of H2O, which is the main factor for vigorous fluoride boiling. In addition, if HF-H is used2Bubbling method for removing oxygen from molten salt system because HF has strong corrosivity and toxicity and H2Is flammable and explosive, and the process control is more strict when the method is adopted (such as HF/H)2The technical process and the reaction end point monitoring aspect), difficult tail gas sampling (HF-containing gas needs to be condensed by a cold trap, the cold trap needs to be specially customized), strict requirements on the gas tightness of a system (for example, the pressure drop on a 0.5H pressure sensor is less than 1%), and the tail gas emission needs to HF and H2By special treatment, e.g. HF requiring absorption in lye, H2Requiring a backfire engine, etc. The problems in the aspects mentioned above increase HF-H2The application difficulty of the bubbling method is not easy for industrial production.
In the 2010 molten salt engineering data report of the national laboratory of Edward, the molten salt deoxidation method of the fluorine salt and the chlorine salt is summarized as follows: 1. vacuum drying (10)-3mmHg) removing free water; 2. isobaric chemical drying method; 3. bubbling HF/H into molten salts2(ii) a 4. Ammonium hydrogen fluoride (NH)4F ∙ HF) treatment with NH4The HF decomposed by F ∙ HF reacts with the oxide to remove oxygen, but the process residue causes more corrosion; 5. adding chemically active component (such as alkali metal, Be or Zr) which can Be used as reducing agent to remove oxidant (such as HF, water, nitrate radical and sulfate radical); 6. slagging and filtering; 7. dry argon carrier method; 8. bubbling dry HCl and Cl2(ii) a 9. Bubbling into CCl4(ii) a 10. Addition of NH4Cl or NH4Cl∙HCl, and the like.
In the prior art, deoxidation is also carried out in molten salt systems by electrochemical methods, for example, in patent CN102586809A, a carbonaceous additive is disclosed for improving TiO2Method for cathodic deoxidation process using TiO2Making composite cathode with C, graphite rod as anode, and adding CaCl2Electrochemical deoxidation of a molten salt electrolyte system. The essence of electrochemical deoxidation is that positive and negative electrodes are adopted, and O is enabled at the anode2-Generation of O2The oxygen in the molten salt is removed, but the yield and the efficiency are low, and the oxygen removal is difficult to carry out after reaching a certain degree, because the probability of the oxide to be free to the electrode is lower and lower.
As described above, there are many methods for removing impurities such as water, oxides, oxo acid salts, and hydroxides in the molten salt as described above, but none of these methods relates to a method for directly using carbon as a reducing agent for molten salt deoxidation. Therefore, for the deoxidation process of a molten salt system, the development of a deoxidation method which has high deoxidation efficiency, safety, reliability, simplicity, easy operation, no steam expansion and severe boiling of molten salt to cause the phenomenon that the molten salt blocks a pipeline and is beneficial to industrial production is an urgent problem to be solved.
Disclosure of Invention
The technical problem solved by the invention is to overcome the defect that in the prior art, HF-H is adopted in a molten salt system2During the bubbling method, the process control is strict, potential safety hazards exist, the phenomenon that fused salt blocks a pipeline and is lost due to severe boiling of water vapor expanded fused salt is easy to cause, and the defects that the fused salt is not beneficial to industrial production are overcome, and the fused salt deoxidation method and the deoxidized fused salt are provided. In the deoxidation process, carbon is directly used as a reducing agent for the molten salt, high deoxidation efficiency is ensured, safety, reliability, controllability, simplicity and easy operation are realized, products reduced by the carbon are removed in a gas form without accumulation, nitrate radicals, sulfate radicals, free oxygen and oxygen free radicals in the molten salt are removed, and industrial production is facilitated; if HF-H is present later2When molten salt is treated, the anhydrous steam expansion molten salt is violently boiled, and the phenomenon of pipeline blockage and molten salt loss caused by boiling are caused. Only need to be added in the subsequent process of the deoxidation treatment of the inventionRemoving carbon. If the molten salt is treated by hydrogen at the later stage, the hydrogen can react with carbon at the temperature of 500 ℃ above and below the molten salt melt to generate methane, and the carbon is removed.
Through a great deal of experimental research, the inventor of the invention finds that the molten salt contains a great deal of free oxygen (or oxygen dissolved in the molten salt), oxygen free radicals (oxygen bonds can be partially broken to form oxygen free radicals at high temperature), a small amount of nitrate radicals, sulfate radicals and the like, and the existence of the oxygen greatly increases HF-H2The generation of water in the bubbling process further increases the instability of the bubbling process. The invention directly applies carbon as a reducing agent to the molten salt deoxidation process, and aims to remove the oxygen and avoid HF-H2This occurs during the bubbling process. In addition, the process of heating-cooling-heat preservation-reheating is a special process screened by treating molten salt deoxidation, and aims to melt the molten salt by heating for the first time, reduce the solubility of generated gas in the molten salt along with the reduction of the temperature in the heat preservation stage, so that the gas escapes from the melt by cooling for the later time, reduce the temperature to a low-temperature region, such as the solidification of the molten salt melt to room temperature, and the carbon further performs redox reaction with molecules which can react at low temperature in the process to generate gas, and the gas generated before escapes when the temperature is raised to be molten, and the temperature is lowered to repeat the separation and escape of the dissolved gas before the temperature is lowered, so that the oxygen existing in the molten salt is removed. The method can also repeatedly carry out the operations of heating, heat preservation and cooling to fully remove the dissolved oxygen in the molten salt.
The carbon has reducibility, the nitrate, the sulfate and the oxygen free radical in the molten salt system are removed by the reaction of the carbon, the nitrate, the sulfate, the oxygen free radical and the free oxygen, and partial reaction formula is as follows:
the invention solves the technical problems through the following technical scheme.
The invention provides a molten salt deoxidation method, which comprises the following steps: introducing carbon into the molten salt, heating to melt the molten salt for the first time under a vacuum condition, preserving heat for the first time, cooling for the first time, heating to melt the molten salt for the second time, preserving heat for the second time, and cooling for the second time; wherein the molten salt is fluoride molten salt and/or chloride molten salt.
In the invention, a vacuum system is adopted in the deoxidation method, which not only can realize the removal of gas-phase oxides generated by carbon reduction, but also can be convenient for the removal of impurities in the raw materials due to the high-temperature decomposition of the impurities into gas-phase substances.
In the present invention, the fluoride molten salt is a fluoride molten salt conventional in the chemical field, and is preferably selected from lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), rubidium fluoride (RbF), cesium fluoride (CsF), and ferrous fluoride (FeF)2) Iron fluoride (FeF)3) Nickel fluoride (NiF)2) Aluminum fluoride (AlF)3) Yttrium Fluoride (YF)3) Zirconium fluoride (ZrF)4) Chromium fluoride (CrF)2) Chromium trifluoride (CrF)3) Cerium fluoride (CeF)3) Hafnium fluoride (HfF)4) Tin fluoride (SnF)2) Lead fluoride (PbF)2) Plutonium fluoride (PuF)3) Zinc fluoride (ZnF)2) Beryllium fluoride (BeF)2) Magnesium fluoride (MgF)2) Calcium fluoride (CaF)2) Barium fluoride (BaF)2) Thorium fluoride (ThF)4) Uranium tetrafluoride (UF)4) And uranium trifluoride (UF)3) More preferably selected from lithium fluoride (LiF), beryllium fluoride (BeF)2) Zirconium fluoride (ZrF)4) Sodium fluoride (NaF), potassium fluoride (KF), thorium fluoride (ThF)4) And uranium tetrafluoride (UF)4) One or more of (a).
In the present invention, the chloride molten salt is a chloride molten salt that is conventional in the chemical field, and is preferably selected from lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), rubidium chloride (RbCl), cesium chloride (CsCl), and ferrous chloride (FeCl)2) FeCl, ferric chloride (FeCl)3) Nickel chloride (NiCl)2) Aluminum chloride (AlCl)3) Chlorination ofYttrium (YCl)3) Chromium trichloride (CrCl)3) Cerium chloride (CeCl)3) Zinc chloride (ZnCl)2) Magnesium chloride (MgCl)2) Calcium chloride (CaCl)2) And barium chloride (BaCl)2) More preferably selected from potassium chloride (KCl), lithium chloride (LiCl), sodium chloride (NaCl), cerium chloride (CeCl)3) Neodymium chloride (NdCl)3) Magnesium chloride (MgCl)2) Zirconium chloride (ZrCl)4) Nickel chloride (NiCl)2) And ferrous chloride (FeCl)2) One or more of (a).
In the present invention, the pressure of the vacuum condition is conventional in the art, and is generally less than normal pressure (760mmHg), preferably 1X 10-3～1×10-12mmHg, more preferably 1X 10-3～1×10-6mmHg。
In the present invention, the holding temperature directly determines the ease of the carbon deoxidation reaction. The temperature of the first heat preservation or the temperature of the second heat preservation is set according to the melting points of different molten salts. If the temperature of the heat preservation is too high, the volatilization loss of the molten salt is easily caused. The temperature of the first heat preservation or the temperature of the second heat preservation is generally the melting point of the molten salt to 1000 ℃, preferably 430 to 700 ℃. The temperature of the first heat preservation or the temperature of the second heat preservation is preferably 10 to 100 ℃ higher than the melting point of the molten salt, and more preferably 40 to 50 ℃ higher than the melting point of the molten salt.
In the present invention, in order to ensure that the generated gas phase easily escapes from the molten salt, the longer the first heat-retaining time or the second heat-retaining time is, the better, in consideration of the costs such as time and labor, the time is preferably 0.5 to 12 hours, and more preferably 1 to 8 hours, respectively.
In the invention, the particle size of the carbon can directly influence the suspension property, the dispersibility and the uniformity of the carbon in a molten salt system. The particle size of the carbon is preferably 5nm to 5mm, more preferably 0.5 μm to 2000 μm, and most preferably 6.5 μm to 149 μm.
In the present invention, the amount of carbon is preferably 0.005 to 1%, more preferably 0.1 to 0.3%, in terms of mass% relative to the molten salt.
In the present invention, preferably, stirring is performed in the deoxidation method. The agitation will enhance the deoxidation efficiency of the molten salt system. The stirring is high temperature vacuum stirring, according to common general knowledge in the art.
In the present invention, the manner of introducing carbon into the molten salt is preferably any one of the following two methods: the method I comprises the following steps: mixing molten salt and carbon; method II: and during the first heat preservation, putting the molten salt into a carbon crucible.
In method I, the carbon is a carbon conventional in the chemical art, preferably a carbon powder and/or a carbon block. The carbon powder or the carbon block is a commercial product. The carbon powder is preferably graphite powder produced by Fangda carbon New materials science and technology Co. The mesh number of the carbon powder is preferably 100-2000 meshes.
In method II, the carbon crucible is generally a crucible in which the constituent element is carbon, but the carbon is not limited to a crystal form of carbon, and the content of the carbon is more than 99%, and is preferably selected from a graphite crucible, a carbon-carbon composite crucible, or a carbon fiber crucible. The graphite crucible is preferably made of high-purity graphite. According to common knowledge in the art, the high purity graphite refers to graphite having a carbon content of > 99.99%.
In the method II, under a high-temperature vacuum environment, the tiny carbon elements in the carbon crucible are evenly distributed in the molten salt while dissociating and entering the molten salt. In the method II, the introduced carbon element can be in an atomic scale to hundred nanometers and is generally below 500 nm.
When carbon is introduced by the method II, the first heat preservation time is preferably 0.5 to 10 hours, and more preferably 1 to 8 hours. If the heat preservation time is too long, the carbon content in the molten salt system is too high, and the later carbon removal time is easy to be too long; if the heat preservation time is too short, the content of carbon element in the molten salt system is too low, which is not beneficial to the removal of oxygen in the molten salt system.
In the method II, under the condition of the existence of the carbon crucible, when the oxygen element at the contact interface of the molten salt system and the carbon crucible is removed in the form of bubbles, the bubbles play a role in stirring the molten salt in the process of rising from the side wall or the bottom of the carbon crucible, so that the homogenization of the system is realized, and the carbon can be uniformly distributed in the molten salt.
When carbon is introduced by the method II, after the first cooling, the material after the first cooling is preferably moved to a crucible resistant to corrosion by fluoride molten salt and/or chloride molten salt, and then heated for the second time. The crucible resistant to molten fluoride salt and/or molten chloride salt corrosion is preferably a nickel crucible, a tungsten crucible, or a molybdenum crucible.
In the present invention, the molten salt is in a solid form after the first cooling or after the second cooling. The temperature after the first cooling or after the second cooling is preferably 15 to 150 ℃, more preferably 15 to 25 ℃.
In the invention, the rate of the first temperature rise, the rate of the first temperature drop, the rate of the second temperature rise or the rate of the second temperature drop are conventional in the field, and are preferably controlled within the range of 5-15 ℃/min respectively.
In the invention, preferably, the operations of heating, heat preservation and cooling can be repeatedly carried out to fully remove the dissolved oxygen in the molten salt. Wherein the specific operating conditions of the temperature rise, the heat preservation or the temperature reduction are all as described above.
In the invention, preferably, the deoxidized molten salt prepared by the deoxidation method is introduced with hydrogen to remove carbon introduced in the deoxidation method in a molten state; preferably, the deoxidized molten salt prepared by the deoxidation method is completely replaced by introducing inert gas after introducing mixed gas of hydrogen fluoride and hydrogen to completely react with residual oxygen and carbon in the system in a molten state.
Wherein, in the mixed gas, the volume ratio of hydrogen fluoride to hydrogen is more preferably 1: 10-3: 10. preferably, the molten salt in a molten state is obtained at a temperature rise rate of 5-10 ℃/min. The gas flow rate of the mixed gas is more preferably 110 to 550mL/min, and most preferably 110 to 330 mL/min. The reaction time is more preferably 3 to 48 hours. The time for introducing the inert gas is more preferably 8 to 24 hours. The inert gas is the conventional inert gas in the chemical field, and is generally helium, neon or argon. Preferably, the molten salt completely replaced is cooled to 10-25 ℃.
According to the common knowledge in the field, at the melting temperature of the molten salt of 550 ℃, hydrogen can react with carbon in the system to generate methane, and the carbon is removed.
The invention also provides a molten salt prepared by the deoxidation method. According to the common knowledge in the field, the molten salt is a molten body formed after the salt is melted or a solid formed after the molten body is cooled.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
in the deoxidation process, carbon is directly used as a reducing agent for the molten salt, high deoxidation efficiency is ensured, safety, reliability, controllability, simplicity and easy operation are realized, products reduced by the carbon are removed in a gas form without accumulation, nitrate radicals, sulfate radicals and oxygen radicals in the molten salt are removed, and industrial production is facilitated; if HF-H is present later2When molten salt is treated, the anhydrous steam expansion molten salt is violently boiled, and the phenomenon of pipeline blockage and molten salt loss caused by boiling are caused. In addition, the addition of carbon can increase the conductivity and the thermal conductivity of the molten salt, and the molten salt system becomes a reduction system due to the carbon, so that the corrosivity of the molten salt on metal pipelines or vessels can be reduced.
The method can repeatedly carry out the operations of heating, heat preservation and cooling to fully remove the dissolved oxygen in the molten salt. The invention can also introduce hydrogen into the deoxidized fused salt prepared by the deoxidation method to remove carbon introduced in the deoxidation method in a molten state. The invention can also introduce the mixed gas of hydrogen fluoride and hydrogen into the deoxidized fused salt prepared by the deoxidation method to remove the residual oxygen and the introduced carbon in the system in a molten state.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
In the following examples, the detection apparatus and the detection method for each data are as follows:
ion chromatograph, thermo electric company (formerly dean), model: ICS-2100; the test standard refers to the determination ion chromatography of GBT 31197-2014 inorganic chemical product impurity anions.
Oxy-nitrogen hydrogen analyzer, LECO, model number: TCH-600; test standard reference: measuring the oxygen content of GB/T11261-2006 steel; pulse heating inert gas melting-infrared absorption method.
The particle size of the carbon element introduced through the graphite crucible in the embodiment 1 and the embodiment 2 can be in an atomic scale to a hundred nanometer scale, and is generally below 500 nm; the amount of the carbon element is controlled by the time of the first heat preservation, and is about 0.1-0.3%, and the percentage is relative to the mass percentage of the molten salt.
Example 1
520g of LiF and 470g of BeF were taken2Mixing, placing in a graphite crucible (made of high purity graphite), and vacuum-treating at 2.1 × 10-3mmHg), heating up to 650 ℃ (higher than the melting point of molten salt by 191 ℃) at the speed of 5 ℃/min for the first time until the materials are completely melted, keeping the temperature for 1h for the first time, cooling down to 15 ℃ at the speed of 15 ℃/min for the first time, placing the materials in a nickel crucible, heating up to 650 ℃ at the speed of 10 ℃/min for the second time under the vacuum environment to completely melt the FLiBe, keeping the temperature for 2h for the second time, and cooling down to 15 ℃ at the speed of 15 ℃/min for the second time.
Placing the cooled FLiBe molten salt in HF-H2A bubbling system, heating to 600 ℃ at the heating rate of 10 ℃/min, and bubbling HF/H after the FLiBe molten salt is melted2(HF and H)2The volume ratio is 1: 10) introducing mixed gas with the gas flow of 220mL/min for 3H, and introducing HF and H in an Ar pair system2Replacing for 8h, and cooling to 25 ℃.
The FLiBe molten salt without carbon treatment is pure white blocky crystal, and the FLiBe molten salt after carbon treatment is light grayBulk crystals, further HF-H2The treated FLiBe showed a translucent colorless glass, thus demonstrating that carbon had reacted with H2And (4) removing the reaction.
Example 2
520g of LiF and 470g of BeF were taken2Mixing, placing in graphite crucible, and vacuum sealing (5.6 × 10)- 4mmHg), heating up to 700 ℃ at a speed of 15 ℃/min for the first time until the FLiBe is completely melted, keeping the temperature for 8h for the first time, cooling down to 20 ℃ at a speed of 5 ℃/min for the first time, placing the FLiBe in a tungsten crucible, heating up to 700 ℃ at a speed of 15 ℃/min for the second time under a vacuum environment to completely melt the FLiBe, keeping the temperature for 8h for the second time, and cooling down to 20 ℃ at a speed of 5 ℃/min for the second time.
Example 3
Taking 222g of KCl and 252g of FeCl2Mixing with 1g high purity carbon powder (particle size 1200 mesh, available from Sida carbon New materials science and technology Co., Ltd.), placing in a molybdenum crucible, and vacuum-processing to obtain a mixture (3.9 × 10)-5mmHg), heating up to 500 ℃ at a speed of 15 ℃/min for the first time until the materials are completely melted, keeping the temperature for 4h for the first time, cooling down to 25 ℃ at a speed of 10 ℃/min for the first time, heating up to 500 ℃ at a speed of 5 ℃/min for the second time to completely melt the ClKFe, keeping the temperature for 4h for the second time, cooling down to 25 ℃ at a speed of 5 ℃/min for the second time, heating up to 500 ℃ at a speed of 15 ℃/min for the third time to completely melt the ClKFe, keeping the temperature for 4h for the third time, and cooling down to 25 ℃ at a speed of 15 ℃/min for the third time.
Example 4
520g of LiF and 470g of BeF were taken2Mixing, placing in a carbon-carbon composite crucible, and vacuum-drying (1 × 10)-3mmHg), heating up to 559 ℃ at the speed of 5 ℃/min for the first time until the materials are completely melted, keeping the temperature for 10h for the first time, cooling down to 100 ℃ at the speed of 5 ℃/min for the first time, placing the materials in a tungsten crucible, heating up to 469 ℃ at the speed of 15 ℃/min for the second time under the vacuum environment to be completely melted, keeping the temperature for 12h for the second time, and cooling down to 150 ℃ at the speed of 5 ℃/min for the second time.
Placing the cooled molten salt in HF-H2Bubbling system at 5 deg.CHeating to 560 deg.C at a/min heating rate, and blowing HF/H after molten salt is molten2(HF and H)2The volume ratio is 3: 10) the gas flow rate of the mixed gas is 110mL/min, the mixed gas is introduced for 48H, and then helium is introduced to carry out gas permeation on HF and H in the system2Replacing for 24h, and cooling to 10 ℃.
The molten salt without carbon treatment is pure white block-shaped body, the molten salt after carbon treatment is light gray block-shaped body, and then HF-H treatment is carried out2The treated molten salt was a translucent colorless glass body, from which it was confirmed that carbon had been reacted with H2And (4) removing the reaction.
Example 5
This example was carried out with stirring in the deoxygenation process. 260g of LiF and 580g of KF are uniformly mixed, placed in a carbon fiber crucible and put in a vacuum environment (1X 10)-6mmHg), the first heating to 542 ℃ at the speed of 5 ℃/min until the materials are completely melted, keeping the temperature for 0.5h, cooling to 50 ℃ at the speed of 5 ℃/min, placing the materials in a tungsten crucible, heating to 552 ℃ at the speed of 15 ℃/min in the second time under a vacuum environment to be completely melted, keeping the temperature for 10h for the second time, and cooling to 25 ℃ at the speed of 5 ℃/min in the second time.
Placing the cooled molten salt in HF-H2A bubbling system, heating to 560 ℃ at the heating rate of 8 ℃/min, and blowing HF/H after the molten salt is molten2(HF and H)2The volume ratio is 2: 10) introducing mixed gas with the gas flow of 550mL/min for 24H, and introducing argon for HF and H in the system2The replacement is carried out for 8 hours, and the temperature is reduced to 15 ℃.
The molten salt without carbon treatment is pure white block-shaped body, the molten salt after carbon treatment is light gray block-shaped body, and then HF-H treatment is carried out2The treated molten salt appeared as a white block, thus demonstrating that carbon had been associated with H2And (4) removing the reaction.
Example 6
252.3g of KF and 526g of ZrF are taken4Mixing with 0.039g high purity carbon powder (particle size 5mm), placing in a molybdenum crucible, and vacuum-processing (1 × 10)-3mmHg), heating to 430 ℃ at a speed of 15 ℃/min for the first time until the materials are completely melted, keeping the temperature for 0.5h for the first time, and cooling at a speed of 10 ℃/min for the first timeCooling to 80 deg.C, heating to 430 deg.C at rate of 5 deg.C/min for the second time to completely melt, maintaining for 10 hr, and cooling to 80 deg.C at rate of 5 deg.C/min for the second time.
And (3) placing the cooled molten salt in a hydrogen bubbling system, heating to 430 ℃ at a heating rate of 8 ℃/min, blowing hydrogen after the molten salt is molten, wherein the gas flow is 550mL/min, introducing mixed gas for 24h, introducing argon to replace the hydrogen in the system for 8h, and cooling to 15 ℃.
The molten salt without carbon treatment is a pure white block, the molten salt after carbon treatment is a light gray block, and the molten salt after hydrogen treatment is a white block, thereby proving that carbon is removed by reaction with hydrogen.
Example 7
451.4g of KCl and 491.4g of FeCl are taken2Mixing with 9.42g high-purity carbon powder (particle size 5nm), placing in a molybdenum crucible, and vacuum-processing (1 × 10)-12mmHg), the temperature is increased to 455 ℃ at the rate of 15 ℃/min for the first time until the materials are completely melted, after the temperature is maintained for 6h for the first time, the temperature is increased to 455 ℃ at the rate of 10 ℃/min for the first time, the materials are completely melted, after the temperature is maintained for 10h for the second time, the materials are cooled to 25 ℃ at the rate of 5 ℃/min for the second time.
Example 8
129.5g of KCl and 750.7g of ZrCl are taken4Mixing with 0.88g high purity carbon powder (particle size 0.5 μm), placing in molybdenum crucible, and vacuum-processing (1 × 10)-5mmHg), the temperature is increased to 325 ℃ at the speed of 15 ℃/min for the first time until the materials are completely melted, after the temperature is maintained for 6h for the first time, the temperature is increased to 325 ℃ at the speed of 10 ℃/min for the first time, the materials are completely melted, after the temperature is maintained for 10h for the second time, the materials are cooled to 25 ℃ at the speed of 5 ℃/min for the second time.
Example 9
129.5g of KCl and 750.7g of ZrCl are taken4Mixing with 2.64g high purity carbon powder (particle size 2000 μm), placing in molybdenum crucible, and vacuum sealing (1 × 10)-4mmHg), the temperature is increased to 325 ℃ at the speed of 15 ℃/min for the first time until the material is completely melted, and after the first heat preservation for 6 hours, the temperature is changed for the first time at the speed of 10 ℃After the temperature is cooled to 25 ℃ in min, the temperature is raised to 325 ℃ at the speed of 5 ℃/min for the second time to be completely melted, the temperature is kept for 10 hours for the second time, and then the temperature is cooled to 25 ℃ at the speed of 5 ℃/min for the second time.
Example 10
The particle size of the high purity carbon powder of this example was 2000 mesh, which was purchased from Sida carbon New materials science and technology Co., Ltd, and the remaining operating conditions were the same as those of example 3.
Example 11
The grain size of the high-purity carbon powder of the embodiment is 100 meshes, and the high-purity carbon powder is purchased from Sida carbon New materials science and technology Co., Ltd, and the rest of the operation conditions are the same as those of the embodiment 3.
Effect example 1
The products prepared in examples 1-3 were subjected to relevant tests, and the data are shown in tables 1 and 2. Wherein, Table 1 shows the oxygen analysis before and after the carbon treatment of the molten salt in examples 1 to 3 and HF-H in example 12Oxygen analysis of the molten salt after the bubbling treatment is shown in Table 2, which is the ion chromatography analysis before and after the carbon treatment of the molten salt in examples 1 to 3.
The data of the products obtained in examples 4 to 11 are comparable to those of examples 1 to 3.
TABLE 1
| Detecting items | Example 1 | Example 2 | Example 3 |
| Oxygen analysis/ppm before carbon treatment | 1978 | 2861 | 1520 |
| Oxygen analysis/ppm after carbon treatment | 548 | 653 | 428 |
| HF-H2Oxygen analysis/ppm after treatment | 386 | ---- | ----- |
TABLE 2
Claims (23)
1. A molten salt deoxidation method, characterised in that it comprises the steps of: introducing carbon into the molten salt, heating to melt the molten salt for the first time under a vacuum condition, preserving heat for the first time, cooling for the first time, heating to melt the molten salt for the second time, preserving heat for the second time, and cooling for the second time; wherein the molten salt is fluoride molten salt and/or chloride molten salt;
the temperature of the first heat preservation or the temperature of the second heat preservation is respectively the melting point of the molten salt to 1000 ℃;
the first heat preservation time or the second heat preservation time is 0.5-12 hours respectively.
2. The deoxidation method of claim 1 wherein the fluoride molten salt is selected from one or more of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, ferrous fluoride, ferric fluoride, nickel fluoride, aluminum fluoride, yttrium fluoride, zirconium fluoride, chromium fluoride, cerium fluoride, hafnium fluoride, tin fluoride, lead fluoride, zinc fluoride, beryllium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, thorium fluoride, uranium tetrafluoride, and uranium trifluoride;
and/or the chloride fused salt is selected from one or more of lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, ferrous chloride, ferric chloride, nickel chloride, aluminum chloride, yttrium chloride, chromium trichloride, cerium chloride, zinc chloride, magnesium chloride, calcium chloride and barium chloride.
3. The deoxidation method of claim 2 wherein the fluoride molten salt is selected from one or more of lithium fluoride, beryllium fluoride, zirconium fluoride, sodium fluoride, potassium fluoride, thorium fluoride and uranium tetrafluoride;
and/or the chloride molten salt is selected from one or more of potassium chloride, lithium chloride, sodium chloride, magnesium chloride, nickel chloride and ferrous chloride.
4. The deoxidation method of claim 1, wherein said vacuum conditions are at a pressure of 1 x 10-3~1×10- 12mmHg；
And/or the temperature of the first heat preservation or the temperature of the second heat preservation is 430-700 ℃ respectively;
and/or the temperature of the first heat preservation or the temperature of the second heat preservation is respectively 10-100 ℃ higher than the melting point of the molten salt;
and/or the first heat preservation time or the second heat preservation time is 1-8 hours respectively.
5. The deoxidation method of claim 4, wherein said vacuum conditions are at a pressure of 1 x 10-3~1×10- 6mmHg；
And/or the temperature of the first heat preservation or the temperature of the second heat preservation is 40-50 ℃ higher than the melting point of the molten salt respectively.
6. The deoxidation method of claim 1, wherein the carbon has a particle size of 5nm to 5 mm;
and/or the amount of the carbon is 0.005-1%, and the percentage is relative to the mass percentage of the molten salt;
and/or stirring is performed in the deoxygenation method.
7. The deoxidation method of claim 6, wherein the carbon has a particle size of 0.5 μm to 2000 μm;
and/or the amount of the carbon is 0.1-0.3%, and the percentages are mass percentages relative to the molten salt.
8. The deoxidation method of claim 7, wherein the carbon has a particle size of 6.5 μm to 149 μm.
9. The deoxidation method of claim 1 wherein the carbon is introduced into the molten salt by either of two methods: the method I comprises the following steps: mixing molten salt and carbon; method II: and during the first heat preservation, putting the molten salt into a carbon crucible.
10. The deoxygenation method of claim 9, wherein in method I, the carbon is carbon powder and/or carbon block;
and/or, in method II, the carbon crucible is selected from a graphite crucible, a carbon-carbon composite crucible, or a carbon fiber crucible;
when carbon is introduced by adopting the method II, the first heat preservation time is 0.5-10 hours;
when carbon is introduced by the method II, after the first cooling, the material after the first cooling is moved to a crucible which is resistant to corrosion of fluoride molten salt and/or chloride molten salt, and then the temperature is raised for the second time.
11. The deoxidation method of claim 10, wherein the mesh number of the carbon powder is 100-2000 mesh;
and/or the graphite crucible is made of high-purity graphite;
and/or when carbon is introduced by adopting the method II, the first heat preservation time is 1-8 hours;
and/or the crucible which is resistant to corrosion of the fluoride molten salt and/or the chloride molten salt is a nickel crucible, a tungsten crucible or a molybdenum crucible.
12. The deoxidation method of claim 1, wherein the temperature after the first cooling or after the second cooling is 15 to 150 ℃ respectively;
and/or the rate of the first temperature rise, the rate of the first temperature drop, the rate of the second temperature rise or the rate of the second temperature drop are respectively controlled within the range of 5-15 ℃/min;
and/or repeatedly carrying out the operations of heating, heat preservation and cooling to fully remove the dissolved oxygen in the molten salt.
13. The deoxidation method of claim 12, wherein the temperature after the first cooling or after the second cooling is 15 to 25 ℃ each.
14. The deoxidation method according to claim 12 or 13, wherein the deoxidized molten salt produced by the deoxidation method is subjected to hydrogen gas introduction in a molten state to remove carbon introduced in the deoxidation method.
15. The deoxidation method according to claim 14, wherein the molten salt after deoxidation prepared by the deoxidation method is introduced, in a molten state, after a mixed gas of hydrogen fluoride and hydrogen gas completely reacts with the residual oxygen and carbon in the system, the mixed gas is completely replaced by introducing an inert gas.
16. The deoxidation method of claim 15, wherein the volume ratio of hydrogen fluoride to hydrogen in the mixed gas is 1: 10-3: 10.
17. the deoxidation method of claim 15, wherein the molten salt is obtained in a molten state by a ramp rate of 5 to 10 ℃/min.
18. The deoxidation method of claim 15, wherein the mixed gas has a gas flow rate of 110 to 550 mL/min.
19. The deoxidation method of claim 18, wherein the mixed gas has a gas flow rate of 110 to 330 mL/min.
20. The deoxygenation method of claim 15, wherein the reaction time is 3 to 48 hours.
21. The deoxidation method of claim 15, wherein the inert gas is passed for a period of 8 to 24 hours.
22. The deoxidation method of claim 15, wherein the fully displaced molten salt is cooled to 10-25 ℃.
23. A molten salt produced by the deoxidation method of any one of claims 1 to 22.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510570785.0A CN106517097B (en) | 2015-09-09 | 2015-09-09 | Molten salt deoxidation method and deoxidized molten salt |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510570785.0A CN106517097B (en) | 2015-09-09 | 2015-09-09 | Molten salt deoxidation method and deoxidized molten salt |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN106517097A CN106517097A (en) | 2017-03-22 |
| CN106517097B true CN106517097B (en) | 2020-02-18 |
Family
ID=58345539
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510570785.0A Active CN106517097B (en) | 2015-09-09 | 2015-09-09 | Molten salt deoxidation method and deoxidized molten salt |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN106517097B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106477618B (en) * | 2015-08-27 | 2019-07-09 | 中国科学院上海应用物理研究所 | A kind of fused salt solid solution and preparation method thereof and preparation facilities |
| CN107274944A (en) * | 2017-06-29 | 2017-10-20 | 中国科学院上海有机化学研究所 | A kind of two-part FLiNaK fused salts depth method of deoxidation |
| CN107473201A (en) * | 2017-08-22 | 2017-12-15 | 邹远升 | A kind of anti-corrosion fused salt material and its preparation method and application |
| CN108584985B (en) * | 2018-05-15 | 2019-12-13 | 新疆盐湖制盐有限责任公司 | Vacuum deoxidation device and method for salt production system |
| CN109207128A (en) * | 2018-09-11 | 2019-01-15 | 中国科学院上海应用物理研究所 | A kind of preparation method and applications of high-purity molten chloride |
| CN109097001B (en) * | 2018-09-25 | 2021-03-19 | 中国科学院上海应用物理研究所 | Preparation method of multi-component chloride eutectic molten salt |
| CN109781587A (en) * | 2019-01-04 | 2019-05-21 | 江苏理工学院 | A kind of aluminium/aluminium alloy drop surface scale minimizing technology |
| CN110203886B (en) * | 2019-06-20 | 2020-10-23 | 中国科学院上海应用物理研究所 | Fused salt deoxidation method using nitrogen trifluoride as fluorinating agent |
| JP2023501357A (en) | 2019-11-08 | 2023-01-18 | アビリーン クリスチャン ユニバーシティ | Identification and quantification of components in high melting point liquids |
| CN111304674A (en) * | 2020-03-25 | 2020-06-19 | 哈尔滨工程大学 | Preparation of UO2Method (2) |
| CN112891973B (en) * | 2021-01-15 | 2022-09-13 | 中国科学院上海应用物理研究所 | Method for reducing oxygen content in halide molten salt |
| CN113072096B (en) * | 2021-03-18 | 2023-02-10 | 刘明钢 | Preparation method of thorium-based molten salt reactor oxygen-free zirconium tetrafluoride applied to nuclear fission energy |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1952190A (en) * | 2005-10-21 | 2007-04-25 | 钟群标 | Process for smelting aluminium by carbon reduction method via adding sodium chloride-alumina molten salt |
| CN102409363A (en) * | 2011-11-24 | 2012-04-11 | 中国船舶重工集团公司第七二五研究所 | Method for preparing titanium with fused salt electrolysis process |
| CN103572318A (en) * | 2013-09-16 | 2014-02-12 | 中国科学院上海应用物理研究所 | Deoxidized anode, fluoride fused salt electrolysis deoxidizing device and electrolytic method |
| CN203440069U (en) * | 2013-04-25 | 2014-02-19 | 中国科学院上海有机化学研究所 | Fusion furnace for preparing fused salt |
| CN104096847A (en) * | 2013-04-03 | 2014-10-15 | 北京有色金属研究总院 | Preparing method of low-oxygen large-dimension high-purity hafnium powder |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1559682A4 (en) * | 2003-04-21 | 2007-01-03 | Sumitomo Titanium Corp | Method of purifying metal salt, method of deacidifying titanium material and method of producing the same |
-
2015
- 2015-09-09 CN CN201510570785.0A patent/CN106517097B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1952190A (en) * | 2005-10-21 | 2007-04-25 | 钟群标 | Process for smelting aluminium by carbon reduction method via adding sodium chloride-alumina molten salt |
| CN102409363A (en) * | 2011-11-24 | 2012-04-11 | 中国船舶重工集团公司第七二五研究所 | Method for preparing titanium with fused salt electrolysis process |
| CN104096847A (en) * | 2013-04-03 | 2014-10-15 | 北京有色金属研究总院 | Preparing method of low-oxygen large-dimension high-purity hafnium powder |
| CN203440069U (en) * | 2013-04-25 | 2014-02-19 | 中国科学院上海有机化学研究所 | Fusion furnace for preparing fused salt |
| CN103572318A (en) * | 2013-09-16 | 2014-02-12 | 中国科学院上海应用物理研究所 | Deoxidized anode, fluoride fused salt electrolysis deoxidizing device and electrolytic method |
Non-Patent Citations (3)
| Title |
|---|
| "Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride";George Zheng Chen et al;《Nature》;20000921;第407卷;第361-364页 * |
| "FLiNaK熔盐的制备";宗国强等;《核技术》;20140515;第37卷(第5期);第1-6页 * |
| "熔盐电脱氧工艺条件的研究";彭曼华等;《河北联合大学学报》;20120615;第34卷(第1期);第6-9页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN106517097A (en) | 2017-03-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106517097B (en) | Molten salt deoxidation method and deoxidized molten salt | |
| Zong et al. | Preparation of high-purity molten FLiNaK salt by the hydrofluorination process | |
| JPH02111893A (en) | Method for reducing a zirconium chloride, a hafnium chloride or a titanium chloride into a metal product | |
| CN113667841B (en) | Method for extracting rare earth and recovering fluorine resource from bastnaesite | |
| JP2018108923A (en) | Hydrogen-containing rare earth fluoride, production method thereof and use thereof | |
| CN110203886B (en) | Fused salt deoxidation method using nitrogen trifluoride as fluorinating agent | |
| CN103572318A (en) | Deoxidized anode, fluoride fused salt electrolysis deoxidizing device and electrolytic method | |
| Zaikov et al. | High-temperature electrochemistry of calcium | |
| CN106811609B (en) | A kind of method of bastnasite production rare earth fluoride | |
| US3154379A (en) | Plutonium separation from uranium and lanthanides by precipitation from molten chloride solutions | |
| JP2000284090A (en) | Method for reprocessing spent nuclear fuel | |
| US2668750A (en) | Purification of by-product halide salts | |
| Xie et al. | Study on the mechanism of deoxidization and purification for Li2BeF4 molten salt via graphite nanoparticles | |
| CN112981461B (en) | High-purity metal beryllium and preparation process thereof | |
| Zhang et al. | Application of liquid Ga-Pb cathode for selective separation of samarium fission products from molten alkali metal chlorides | |
| CN109023430A (en) | Electrorefining Ti electrolyte prepares TiCl3Method and recovery method | |
| Shchetinskiy et al. | Interaction of Neodymium Containing Chloride Melts with Oxygen Species | |
| CN104109757B (en) | A kind of technique recycling calciothermic reduction fused salt used | |
| CN102515214A (en) | Method for reducing magnesium oxide impurity in solid magnesium chloride | |
| US3804939A (en) | Method of precipitating americium oxide from a mixture of americium and plutonium metals in a fused salt bath containing puo2 | |
| CN106590547B (en) | A kind of inhibition fused salt and its preparation process containing chromium | |
| Jain et al. | Electroextraction of boron from boron carbide scrap | |
| Wang | Scandium and Its Materials Applications | |
| RU2777321C1 (en) | Method for producing anhydrous plutonium trifluoride | |
| Pylypenko et al. | Processing substandard materials of magnesium-thermal zirconium production |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20190508 Address after: Room J1800, Building 1288 Yecheng Road, Jiading District, Shanghai 201800 Applicant after: Shanghai Lianhe Rihuan Energy Technology Co., Ltd. Address before: 201800 Baojia Highway 2019, Jiading District, Shanghai Applicant before: Shanghai Inst. of Applied Physics Chinese Academy of Sciences |
|
| TA01 | Transfer of patent application right | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |