China Nuclear North Nuclear Fuel Components Company
1 Introduction
Molten salt electrolysis method Metal calcium production process was born in the early 20th century, and it has been nearly one hundred years history. With the establishment of China's nuclear industry, from the late 1950s to the early 1960s, our company introduced the former Soviet Union molten salt electrolysis method of metal calcium production process, established China's first metal calcium production enterprises. Initially, metal calcium products were used only in the military industry's military products field. The production scale was small and the annual output did not exceed 500 tons. In the early 1980s, metal calcium products began to enter the international and domestic civilian market, and the output reached 1,000 tons. In the 1990s, with the continuous expansion of the application of metal calcium products, the company carried out the first expansion and expansion of the metallurgical calcium production line of molten salt electrolysis, and the output reached 2,000 tons. In the late 1990s, the second and third molten salt electrolysis methods were used to expand and expand the metal calcium production line, and the output reached 5,000 tons. In the 21st century, the company also carried out the fourth expansion and expansion of the molten calcium electrolytic production line, with a production volume of 7,000 tons, and it has become the largest producer of metal calcium in Asia and the world.
Molten salt electrolysis method of metal calcium production process, after a century of continuous technological renovation, has become the world's most advanced production technology, its product quality represents the international level.
Reviewing the history of metal calcium production, there are two types of metal calcium production processes that can produce production scale, molten salt electrolysis production process and aluminothermic reduction production process. The molten salt electrolysis method is mainly used in Russia and China, and the aluminothermic reduction method is mainly used in France, the United States, and Canada. Since the 1990s, the aluminothermic reduction process has gradually withdrawn from the field of metal calcium production, while the molten salt electrolysis process has become the mainstream of the world's metal calcium production.
2 Introduction of Metal Calcium Process by Molten Salt Electrolysis
After the purchased lime (calcium oxide) is digested, it becomes an aqueous calcium hydroxide solution. The calcium hydroxide aqueous solution reacts with the chlorine gas generated in the electrolytic cell in the absorption tower to generate an aqueous calcium chloride solution which is neutralized, purified and filtered to become a calcium chloride net mother liquor. After the calcium chloride net mother liquor is dried and dehydrated, it becomes an intermediate product of anhydrous particulate calcium chloride. Granular calcium chloride products are added to the electrolytic cell. Under the action of direct current, the cathodic product is metallic calcium and the anode product is chlorine gas. After the metal calcium is vacuum distilled, it becomes a metal calcium ingot, and the chlorine gas is transported to the absorption station. After the metal calcium ingots are machined, they become calcium, calcium and calcium products.
2.1 Absorption and purification process
The main work of absorption and purification process is: in the Ryukyu Tower, lime milk (calcium hydroxide solution) is used to absorb the chlorine produced by the electrolytic cell to produce a calcium chloride crude mother liquor. After the crude mother liquor is neutralized, filtered and slag removed, it becomes a calcium chloride net mother liquor for drying use.
2.2 Drying process
The main work of the drying process is to dry and dehydrate the calcium chloride net mother liquor to produce anhydrous calcium chloride, which is used for Power Supply solution.
2.3 Electrolysis process
The main work of the electrolysis process is as follows: Under the action of direct current, calcium chloride is melted and electrolyzed, the anode produces chlorine, and the cathode produces calcium. The calcium produced by the cathode and the electrolytic copper form a copper-calcium-rich alloy for distillation. The chlorine gas generated from the anode is sent to the Ryukyu Tower.
2.4 Distillation process
The main work of the distillation process is to separate the calcium and copper in the copper-calcium-rich alloy under vacuum and high temperature to obtain a high-purity metal calcium ingot.
2.5 Calcium Products Processing
The main work of calcium products processing is: using the method of mechanical processing, the metal calcium ingots are processed into calcium products such as calcium blocks, calcium chips, and calcium grains.
3 molten salt electrolysis method of calcium metal process characteristics
3.1 Process Design System and Integrity
Molten salt electrolysis method of metal calcium production process, from raw material input to finished product processing, process design with system and integrity, always keep the material circulation of chemical and metallurgical two systems, namely chlorine calcium chloride recycling system and electrolytic copper copper calcium alloy (rich) copper-calcium alloy (lean) circulation system. The first cycle recovers chlorine, which not only solves the environmental pollution caused by chlorine in the electrolysis process, but also converts the recovered chlorine gas into the main raw material for electrolysis production. The second cycle is to ensure that the consumption of electrolytic copper is only a mechanical loss during the production process, that is, the consumption of one ton of metal calcium electrolytic copper is very small, and it does not need to invest a lot of electrolytic copper funds.
3.2 Advancement of product quality
Molten salt electrolytic metal calcium production process, the quality of its metal calcium products, with the world advanced level. This is because at the beginning of the production of calcium metal by molten salt electrolysis, it was used for nuclear industry military products. Process design requires that the final product must meet the needs of the nuclear industry's military products. Therefore, the production process determines the product quality, which is unmatched by other production processes. "Calcium ingots and their products" GB/T 4864-1995 National standards have been compiled and revised by the molten salt electrolysis method for producing calcium metal, and it also reflects the molten salt electrolysis method for the production of metallic calcium, which represents the product quality. Domestic advanced level. Metal calcium products won the National Quality Silver Award twice in 1982 and 1988, and won the Beijing First Expo Gold Medal in 1989.
3.3 The advanced nature of the production process
Molten salt electrolysis method of metal calcium production process, after more than 40 years of production and operation, during the process, has carried out several technological transformations of the process and process equipment, such as: distillation tank technical transformation, absorption of the Ryukyu Tower process technology transformation, dry chlorine Technical transformation of calcium boiling granulation process, technological transformation of drying heating system, technological transformation of electrolytic rectifier unit, technical transformation of graphite anode assembly of electrolytic cell, and so on. Through technological transformation, the level of production technology has been greatly improved. Therefore, it has become the most advanced production technology in the world.
3.3 Economic Cost of Production Cost
As the molten salt electrolytic method has the world's most advanced production technology, the production cost has been kept at the international and domestic advanced level. In particular, after metal calcium enters the civilian market, the company continuously injects funds, carries out technological upgrading and transformation, upgrades the level of technology and equipment, increases production efficiency, reduces consumption, and reduces production costs. It occupies international and domestic markets with high-quality products and reasonable prices. Metal calcium market.
4 Advantages of Molten Salt Electrolysis Method for Calcium Metal Production Process
4.1 Process maturity and stability
The molten salt electrolysis production process has undergone 100 years of continuous technological transformation and has formed its own unique, mature and stable production process. Its various economic and technological and raw material consumption indicators have created the best level in history, further reducing production costs and significantly increasing economic benefits.
4.1.1 Absorption purification process
In 1978, technological transformation of the absorption process was carried out. The chlorine recovery rate reached 99.0%, an increase of 4%. Due to the simplification of process operations, the labor intensity of employees is reduced.
4.1.2 Drying process
In 1987, technical transformation of the drying process was carried out. Increase production capacity by 20%. In 1996, the technological transformation of dry heat source technology was carried out, and the utilization rate of heat energy was increased by 30%. It is the heating equipment with the highest thermal efficiency in China. At the same time, due to the higher degree of automation of the above two technological transformations, the labor intensity of employees has been greatly reduced.
4.1.3 Electrolysis process
The single cell production and current efficiency of the electrolytic cell are important parameters for measuring the electrolytic process level. After several decades of process tests and adjustment of process parameters, a reasonable control of the electrolyte composition and electrolyte temperature, especially in current density control, has led to a breakthrough in single cell production from 9.0 tons/month to 10.5 tons/month. The current efficiency reaches 78%, an increase of 8%.
4.1.4 Distillation process
From 1968 to 1970, technological transformation of distillation tank equipment was carried out, with a unit production increase of 45%, a reduction in the consumption of distillation cans of 30%, and a 20% reduction in electricity consumption.
4.2 Wide range of product applications
Molten salt electrolysis method of calcium metal products, calcium content can reach 99.9%, if the process is adjusted, the calcium content can reach 99.99%. In addition to iron and steel metallurgy, battery manufacturing industry, nuclear industry, rare earth metal smelting, rare metal smelting, pharmaceutical and other industries, the demand for high-purity metal calcium products is increasing. Therefore, the molten salt electrolysis method of calcium metal products has a very wide application field.
4.2 Significant economies of scale
The molten salt electrolysis method produces 7,000 tons of calcium per year, ranking first in the world. At present, the annual production volume is more than 5,000 tons. No matter the scale of production or the per capita output value is world-class. With the continuous expansion of the application of metal calcium, the demand for its products is also growing, the molten salt electrolysis method of metal calcium shows more advantages.
5 molten salt electrolysis method of calcium metal production process and product outlook
5.1 Prospects of Production Process
Molten salt electrolysis method of metal calcium production process, after a century of actual production test and continuous technological innovation and transformation, has become the world's most advanced metal calcium production process. Since electrolysis and distillation require a large amount of electrical energy, it is a high-energy-consuming enterprise.
As the molten salt electrolysis method of the metal calcium production process, improving the electrolysis and distillation process and reducing the power consumption is the focus of development and research. At present, we have done a lot of basic work in electrolytic and distillation process improvements, and we have also achieved some results. After the implementation of electrolysis and distillation process technology improvements, it will greatly reduce the energy consumption of metal calcium production, production costs will be significantly reduced, and play a key role in improving economic efficiency.
5.2 Product Outlook
With the continuous expansion of the application of metal calcium products, the continuous increase in market demand, users of the continuous improvement of the quality of metal calcium products, molten salt electrolysis method of calcium metal products will have a big development. We also have a long-term plan to build a production scale with an annual output of 10,000 tons of metal calcium, and the output of metal calcium additive products will reach 5,000 tons. At the same time, the energy consumption per ton of calcium is reduced by 20% through technological transformation.
Dongguan XINYUDA Technology Co., Ltd. , https://www.gdxige.com