CN107385474B - A kind of chlorination calcium molten salt electrolysis calcium electrolyte and the electrolytic method using the electrolyte - Google Patents

Abstract

The invention discloses an electrolyte for producing calcium by electrolysis of calcium chloride molten salt and an electrolysis method using the electrolyte. The mole percentage composition of the electrolyte of the invention is: CaCl ₂ is 5% to 20%, LiCl is 10% to 20% KF , KF is 10% to 20%, CaF ₂ is 5% to 10%, and the balance is KCl. The initial crystallization temperature of the electrolyte and the density of the electrolyte using the above component formula can be significantly lower, and can be controlled to be less than the density of molten calcium. When the above electrolytic electrolyte is used for production, the molten metal calcium obtained by electrolysis can be deposited on the bottom layer of the electrolyte. on the surface of the carbon cathode. The electrolytic production of molten salt calcium based on this electrolyte can completely change the existing production mode of calcium electrolysis. The obtained metallic calcium is collected at the bottom of the electrolytic tank and can be extracted very conveniently without further treatment, thus realizing large-scale calcium electrolysis. Scale, continuous and energy-saving production.

Description

An electrolyte for producing calcium by calcium chloride molten salt electrolysis and electrolysis using the electrolyte method

technical field

The invention belongs to the technical field of electrolysis, and in particular relates to an electrolyte for producing calcium by electrolysis of calcium chloride molten salt and an electrolysis method using the electrolyte.

Background technique

The main means of industrial production of metallic high-purity calcium is calcium chloride molten salt electrolysis, and the methods used include contact cathode method and liquid cathode method. The traditional contact cathode method was first proposed by W. Rathenau in 1904, and the electrolyte used was a mixture of CaCl ₂ and CaF ₂ . The density of this molten mixture is much greater than that of molten salt calcium, so the electrolytic cell is designed so that the cathode is close to the upper part of the cell and the anode is at the lower part of the cell. It is less dense than molten calcium chloride and floats on the surface of the electrolyte, condensing on the cathode when in contact with the steel cathode. The cathode can only be in contact with the surface of the melt and cannot be placed in the electrolyte, so that a layer of cold electrolyte can be artificially poured on the surface of the calcium rod to separate the calcium from the air and avoid the oxidative combustion of the calcium. As the electrolysis progresses, the cathode continues to rise accordingly, and the calcium forms a carrot-shaped stick at the bottom of the cathode. As electrolysis begins, the electrolyte below the cathode boils, producing calcium beads that condense as soon as they touch the cold surface of the cathode and stick to the anode. As the cathode is lifted, new calcium beads are regenerated below the cathode.

This method is the most direct method for producing high-purity calcium metal, but considering the reason of the electrolyte system used, the produced calcium metal floats on the upper part of the electrolyte. If no special treatment is carried out, the molten active calcium metal will quickly It will be oxidized, and even if the corresponding technology is adopted, the inherent defect of this method cannot be solved, that is, the problem that the produced metallic calcium floats on the electrolyte, thus causing the traditional contact cathode method to produce calcium with large raw material consumption and low output. , low current efficiency (serious secondary oxidation of calcium), high labor and cost, and a series of problems, and even gradually face to be replaced by liquid cathode electrolysis.

Therefore, in order to solve the problems faced by the traditional contact method in the production of metallic calcium, it is first necessary to design an electrolyte system that can complete calcium electrolysis with a density lower than that of molten metallic calcium, and then design the structure of the electrolytic cell to adapt to the accumulation of metallic calcium. The new phenomenon of the bottom layer of the electrolyte in the tank realizes the efficient and large-scale continuous production of calcium metal electrolysis.

Contents of the invention

The object of the present invention is to overcome the deficiencies in the prior art and provide a kind of calcium chloride molten salt electrolytic calcium production electrolyte, this electrolyte not only has a low primary crystal temperature, but also has a density less than that of molten calcium, and utilizes this electrolyte to electrolyze and generate metallic calcium. The molten metal calcium can be deposited on the surface of the carbon cathode at the bottom of the electrolyte, which can completely change the existing production mode of calcium electrolysis. The obtained metal calcium is collected at the bottom of the electrolytic cell and can be extracted very conveniently without further treatment, thus Realize large-scale, continuous and energy-saving production of calcium electrolysis.

In order to solve the problems of the technologies described above, the molar percentage of the electrolyte for calcium chloride molten salt electrolysis provided by the present invention consists of: _CaCl2 is 5% to 20%, LiCl is 10% to 20%, and KF is 10% to 20%. CaF ₂ is 5% to 10%, and the balance is KCl.

Preferably, the mole percentage composition of the electrolyte is: _CaCl2 is 10%-15%, LiCl is 14%-16%, KF is 14%-16%, _CaF2 is 6%-8%, and the balance is KCl.

Preferably, the mole percentage composition of the electrolyte is: _CaCl2 is 12%, LiCl is 15%, KF is 15%, _CaF2 is 7%, and the balance is KCl.

Further, the electrolysis temperature of the electrolyte is 550°C to 700°C.

Further, the primary crystal temperature of the electrolyte is 530°C-680°C.

Further, the density of the electrolyte is 1.38-1.58 g/cm ³ .

The electrolysis method using the above-mentioned calcium chloride molten salt electrolyte is implemented by a set of calcium chloride molten salt electrolytic calcium production device, which includes an electrolytic cell with a heating device, a gas collector connected to the electrolytic cell and a lower The material system, the cathode arranged at the bottom of the electrolytic cell, and several groups of anodes located above the cathode and corresponding to the cathode, include the following steps:

(1) Mix specific amounts of CaCl ₂ , LiCl, KF, CaF ₂ , and KCl, and use a heating device to keep the resulting mixture in a molten state;

(2) Heating the melt in step (1) to 550° C. to 700° C. for electrolysis.

Preferably, CaCl ₂ is supplemented quantitatively through the gas collection and feeding system during the electrolysis process.

Preferably, the moisture content of the supplemented CaCl ₂ is <0.01%.

Preferably, the anode current density during electrolysis is 1.5-3.5 A/cm ² .

Further, the working current range of the electrolyzer is 50-200kA.

Compared with the prior art, the present invention has the advantages of:

(1) The primary crystal temperature and density of the electrolyte of the present invention are greatly reduced, the density is between 1.38-1.58g/cm ³ , the primary crystal temperature is between 530°C and 680°C, and the conductivity is 2.5-4.5S.cm ^-1 , Therefore, it can work at a lower temperature, and more importantly, the produced metallic calcium can gather at the bottom of the electrolyte due to the difference in density, thereby essentially changing the process and production process of the current contact electrolytic calcium, fundamentally avoiding excessive Calcium produced in the traditional electrolysis process has a major disadvantage of secondary oxidation due to floating on the upper surface of the electrolyte. High-purity metal calcium can be directly electrolyzed.

(2) The present invention can realize large-scale clean production of calcium electrolysis. Since the metal calcium obtained by electrolysis in the present invention gathers at the bottom of the tank, it can be precipitated in a vacuum very conveniently, so the electrolysis process is a continuous and efficient process, and since the single tank is more than 50kA, it can be expanded or expanded according to the actual situation. The series expansion of multiple tanks will make large-scale industrialization very easy.

(3) The electrolysis device used in the present invention can realize rapid and efficient maintenance of the electrolysis cell. Since the anodes in the electrolysis device are independent, their operation and management can be very conveniently learned from the current very mature and efficient management mode of aluminum electrolytic cells. The maintenance and management of anodes and the precipitation of calcium have become very efficient. Consumption, so the electrolyzer can run stably for a long time.

To sum up, the present invention is an electrolyte system and electrolysis method that can realize direct large-scale, continuous and efficient production of metallic calcium by contact method, and can provide guarantee for large-scale and low-cost production of industrial high-purity calcium.

Description of drawings

Fig. 1 is the structure diagram of calcium chloride molten salt electrolysis calcium production device among the present invention.

Detailed ways

Example 1

The mole percentage composition of the electrolyte in this embodiment is: 12% CaCl ₂ , 15% LiCl, 15% KF, 7% CaF ₂ , 51% KCl.

The performance of the electrolyte described in this example was measured, and the results are: the density of the electrolyte in this example is 1.48g/cm ³ , the primary crystal temperature is 600°C, and the conductivity is 3.25S.cm ^-1 .

Example 2

The mole percentage composition of the electrolyte in this embodiment is: 10% CaCl ₂ , 10% LiCl, 20% KF, 6% CaF ₂ , 54% KCl.

The performance of the electrolyte described in this example was measured, and the results are: the density of the electrolyte in this example is 1.43g/cm ³ , the primary crystal temperature is 594°C, and the conductivity is 3.43S.cm ^-1 .

Example 3

The mole percentage composition of the electrolyte in this embodiment is: 15% CaCl ₂ , 20% LiCl, 12% KF, 8% CaF ₂ , 45% KCl.

The performance of the electrolyte described in this example was measured, and the results are: the density of the electrolyte in this example is 1.54g/cm ³ , the primary crystal temperature is 608°C, and the conductivity is 3.12S.cm ^-1 .

Example 4

The mole percentage composition of the electrolyte in this embodiment is: 20% CaCl ₂ , 15% LiCl, 12% KF, 8% CaF ₂ , 45% KCl.

The performance of the electrolyte described in this example was measured, and the results are: the density of the electrolyte in this example is 1.58g/cm ³ , the primary crystal temperature is 615°C, and the conductivity is 3.09S.cm ^-1 .

Example 5

The mole percentage composition of the electrolyte in this embodiment is: 6% CaCl ₂ , 12% LiCl, 20% KF, 6% CaF ₂ , 56% KCl.

The performance of the electrolyte described in this example was measured, and the results are: the density of the electrolyte in this example is 1.38g/cm ³ , the primary crystal temperature is 538°C, and the conductivity is 3.63S.cm ^-1 .

Calcium chloride molten salt electrolytic calcium production device used among the present invention is as shown in Figure 1, and this device comprises the electrolyzer 1 of band heater, is connected with the gas collection and blanking system 2, graphite electrode above electrolyzer 1.

The working area of the electrolytic cell 1 is a rectangular area with a length of 18000 mm and a width of 3000 mm. The electrolytic cell 1 is composed of an outer shell 3 and an insulating layer 4 arranged in the shell 3 .

Graphite electrodes are arranged in pairs in the electrolytic cell 1. The graphite electrodes are unipolar electrodes. The thickness of the electrodes is 200-300mm, the length is 2000-4000mm, and the width is 300-500mm. Several groups of cathodes 6 are arranged side by side in the electrolytic cell 1 At the bottom, the anode 5 is located above the cathode 6 and arranged corresponding to the cathode 6 , the top of the anode 5 is connected with an anode guide rod 7 , and the bottom of the cathode 6 is inserted with a cathode steel rod 8 .

The electrolysis method using electrolyte in the present embodiment 1 is:

(1) Mix the above-mentioned amounts of CaCl ₂ , LiCl, KF, CaF ₂ , and KCl, and use a heating device to keep the resulting mixture in a molten state;

( ₂ ) The melt in step (1) is heated up to 610°C for electrolysis. During the electrolysis process, CaCl is quantitatively replenished through the gas collection and feeding system. At the same time, the anode gas chlorine gas produced is collected. During the electrolysis process, the anode current density is 2.5A/cm ² , the working current of the electrolyzer is 150kA.

The electrolysis method using electrolyte in this embodiment 2 is:

(1) Mix the above-mentioned amounts of CaCl ₂ , LiCl, KF, CaF ₂ , and KCl, and use a heating device to keep the resulting mixture in a molten state;

(2) The melt in step (1) is heated up to 604°C for electrolysis. During the electrolysis process, CaCl is quantitatively supplemented by the gas collection and feeding system ₂ and the anode gas chlorine gas produced is collected at the same time. During the electrolysis process, the anode current density is 1.6A/cm ² , the working current of the electrolyzer is 120kA.

The electrolysis method using electrolyte in present embodiment 3 is:

(1) Mix the above-mentioned amounts of CaCl ₂ , LiCl, KF, CaF ₂ , and KCl, and use a heating device to keep the resulting mixture in a molten state;

(2) The melt in step (1) is heated up to 615°C for electrolysis. During the electrolysis process, CaCl is quantitatively supplemented by the gas collection and feeding system ₂ and the anode gas chlorine gas produced is collected simultaneously. During the electrolysis process, the anode current density is 1.65A/cm ² , the working current of the electrolyzer is 200kA.

The electrolysis method using electrolyte in this embodiment 4 is:

(1) Mix the above-mentioned amounts of CaCl ₂ , LiCl, KF, CaF ₂ , and KCl, and use a heating device to keep the resulting mixture in a molten state;

( ₂ ) The melt in step (1) is heated up to 620°C for electrolysis. During the electrolysis process, CaCl is quantitatively supplemented by the gas collection and feeding system. At the same time, the anode gas chlorine gas produced is collected. During the electrolysis process, the anode current density is 1.75A/cm ² , the working current of the electrolyzer is 250kA.

The electrolysis method using electrolyte in this embodiment 5 is:

(1) Mix the above-mentioned amounts of CaCl ₂ , LiCl, KF, CaF ₂ , and KCl, and use a heating device to keep the resulting mixture in a molten state;

(2) The melt in the step (1) is heated up to 548°C for electrolysis. During the electrolysis process, CaCl is quantitatively supplemented by the gas collection and feeding system ₂ and the anode gas chlorine gas produced is collected at the same time. During the electrolysis process, the anode current density is 1.5A/cm ² , the working current of the electrolyzer is 120kA.

The above-mentioned embodiments have described the specific content of the present invention in detail, and those skilled in the art should understand that any form of improvement and changes in details made on the basis of the present invention belong to the content claimed by the present invention .

Claims (10)

1. a kind of calcium chloride electrolyzing fused salt solution matter, it is characterised in that the molar percentage group of the electrolyte becomes：CaCl₂For 5%~20%, LiCl are that 10%~20%, KF is 10%~20%, CaF₂It is 5%~10%, surplus KCl.

2. calcium chloride electrolyzing fused salt solution matter according to claim 1, it is characterised in that：The Mole percent of the electrolyte Become than group：CaCl₂For 10%~15%, LiCl be 14%~16%, KF it is 14%~16%, CaF₂It is 6%~8%, surplus For KCl.

3. calcium chloride electrolyzing fused salt solution matter according to claim 2, it is characterised in that：The Mole percent of the electrolyte Become than group：CaCl₂For 12%, LiCl 15%, KF 15%, CaF₂It is 7%, surplus KCl.

4. calcium chloride electrolyzing fused salt solution matter according to claim 1, it is characterised in that：The electrolysis temperature of the electrolyte Degree is 550 DEG C~700 DEG C.

5. calcium chloride electrolyzing fused salt solution matter according to claim 1, it is characterised in that：The primary crystal temperature of the electrolyte Degree is 530 DEG C~680 DEG C.

6. calcium chloride electrolyzing fused salt solution matter according to claim 1, it is characterised in that：The density of the electrolyte is 1.38~1.58g/cm³。

7. using the electrolytic method of claim 1-6 any one of them calcium chloride electrolyzing fused salt solution matter, pass through a set of chlorine Change calcium molten salt electrolysis calcium device to implement, which is characterized in that include the following steps：

(1) by the CaCl of specific quantity₂、LiCl、KF、CaF₂, KCl mixed, using chlorination calcium molten salt electrolysis calcium device will To mixture be maintained at molten state；

(2) melt in step (1) 550 DEG C~700 DEG C are warming up to be electrolysed.

8. the electrolytic method of the calcium chloride electrolyzing fused salt solution matter according to right 7, it is characterised in that：Calcium chloride fused salt electricity The gas collection and blanking system, setting that solution calcium device includes the electrolytic cell with heating device, is connected to above electrolytic cell are being electrolysed The cathode of trench bottom and the several groups anode being correspondingly arranged above cathode and with cathode.

9. the electrolytic method of calcium chloride electrolyzing fused salt solution matter according to claim 8, it is characterised in that：It had been electrolysed CaCl is quantitatively supplemented by gas collection and blanking system in journey₂。

10. the electrolytic method of the calcium chloride electrolyzing fused salt solution matter according to right 7, it is characterised in that：In electrolytic process Anodic current density is 1.5~3.5A/cm²。