In the past, for the electrolytic aluminum production process, if there was no cryolite, the electrolytic cell could not enter normal operation, including the process of charging, roasting and starting the electrolytic cell. Nowadays, the R&D team based on Jin Jiang Group's aluminum industry technical expert Wang Jianjun, under the circular economy concept of clean production and green development, has the courage to innovate and change the tradition. After more than ten years of research and efforts, it is the first in China. The use of electrolytic aluminum by-products - electrolyte instead of cryolite to start the roasting of the electrolysis series, and achieved significant economic and social benefits, achieved the recycling of resources, developed a circular economy, and promoted the green development of the aluminum industry.
Courage to challenge
Usually, in the electrolytic aluminum production industry, the electrolysis cell must be calcined and started to be transferred to normal production. Starting an electrolysis cell requires about 50 tons of cryolite to be melted and melted into a liquid electrolyte to meet the production process. Demand. However, in the process of electrolytic aluminum production, a large amount of electrolyte is also produced, and the main component of these electrolytes is cryolite. In general, the electrolytic aluminum plant takes out these electrolytes and stacks them in the electrolysis workshop for a long time. Into industrial waste, this not only causes a lot of valuable resources to waste, but also forms serious environmental pollution. On the one hand, the calcination start of the aluminum electrolysis cell requires a large amount of cryolite, and on the other hand, a large amount of electrolyte is produced in the process of electrolytic aluminum production. In recent years, with the large-scale growth of electrolytic aluminum production capacity, the accumulation of electrolytes is increasing, and the demand for cryolite is increasing. How to use electrolyte to replace cryolite, so that it can be obtained in the start of electrolysis cell roasting Recycling is of great significance.
In 2003, Wang Jianjun, who was still working at Shannanshan Aluminum Co., saw more and more electrolytes in the workshop. He thought that if these electrolytes could be effectively used instead of cryolite, it would save one for the company. It is not a small expense, but more importantly, it can solve the problem of electrolyte pollution. Therefore, the big question mark was buried in the heart of Wang Jianjun.
In the following years, Wang Jianjun began to study this problem that others felt impossible to solve. In 2003 and 2004, laboratory analysis and field test of the physical properties of the blended materials in electrolytic production were successively carried out. In 2005, it began to control the consumption of cryolite in normal production, increase the amount of electrolyte in the late stage of startup, and increase the amount of electrolyte in the startup period. In 2006, industrial experiments and applications of electrolyte powder and electrolytic block furnace were carried out on more than 50 tanks in the 200,000-ton electrolytic aluminum series of Nanshan Aluminum Industry Donghai Phase III. In June 2007, an all-electrolyte powder furnace and roasting industrialization experiment was carried out on the Nanshan Phase II 300kA electrolyzer. In 2008, the industrial application of electrolyte powder instead of cryolite was carried out in Nanshan Phase II.
After passing the electrolyte powder and electrolyte to replace the cryolite test and the pilot application, Kung Fu pays off. In 2008, it finally achieved the initial success of the electrolysis cell roasting to replace the cryolite, and passed the identification of relevant scientific and technological achievements in Shandong Province. Up to 2010, Jinning Aluminum-Magnesium New Materials Co., Ltd. in Zhongning County carried out the large-scale application of resource-saving roasting, and solved the problem of large-scale application of electrolyte instead of cryolite from the perspective of the whole roasting start-up technology, and realized the comprehensive utilization of resources.
Innovative ideas, changing traditions
In the aluminum electrolytic roasting start-up process, the traditional roasting start-up technology in the whole process uses cryolite in the process of furnace charging, roasting, and post-launch management, so that the cryolite-based material is melted to form a liquid electrolyte, and this tradition is accompanied by aluminum in China. The growth of industry has been more than 50 years old. Even in some textbooks in China, this has always been the case, so people have always believed that electrolytes can not be done instead of cryolite.
Although the content of cryolite in the electrolyte component is more than 80%, in the early stage, the electrolyte powder is directly used for baking, and the electrolyte powder is easy to be plated and difficult to dissolve. The use of electrolyte roasting to start the electrolysis cell and incorporate the electrolyte into the circulatory system of the electrolytic aluminum production process was considered a joke in the industry at that time. Solving the knot problem is the key to the replacement of cryolite in the early stage of electrolyte. In order to solve this problem, Wang Jianjun led the team members to carry out several experiments, and conducted in-depth research on the nature of the electrolyte and the mechanism of the start of the roasting of the electrolyzer, by changing the electrolyte acid. Alkaline to optimize electrolyte properties. After the adjustment of the composition, the problem of agglomeration during the melting process was finally solved, which made it completely suitable for the start of the roasting of the electrolytic cell, and the corresponding roasting start-up scheme was compiled, which changed the roasting start-up process that has been used for more than 50 years in China.
Under the above-mentioned changes in the innovative ideas of alkali treatment, Wang Jianjun also produces electrolytes of different particle sizes through crushing, sieving, etc., and mixing them according to a certain ratio, so that they are respectively applicable to the requirements of various parts of the electrolytic cell, that is, the center. The fine-grained parts, the block-shaped and large-sized particles on the side, the powder for heat preservation, etc., simultaneously solve the problem of heat preservation and oxidation prevention of the electrolyte during the start-up process of the electrolyte, and the 400kA series aluminum electrolysis cell in Jinning Aluminum-Magnesium New Material Co., Ltd. On the scale application, the technology completely replaced the cryolite technology in the domestic electrolytic cell roasting process.
With the success of the complete replacement of cryolite by the electrolyte during the roasting process of Jining aluminum-magnesium electrolysis cell, it has aroused the attention of the peers, and began to learn to use the whole electrolyte for roasting start. Now the domestic electrolytic aluminum plant roasting adopts ice crystal. The stone has been rarely heard.
Turn waste into treasure, save more than one billion yuan for the industry
As we all know, at present, the two swords placed on the head of electrolytic aluminum enterprises are cost reduction and efficiency improvement, and Wang Jianjun’s breakthrough in the research on the consumption of cryolite and the comprehensive utilization of electrolytes not only solves the problem of mass production of “waste”. - The problem of electrolyte storage, but also greatly reduces the production costs of enterprises, turning waste into treasure, and killing two birds with one stone.
In the specific practice of using the electrolyte to replace the cryolite roasting start-up technology in the 400kA aluminum electrolysis series production line of Inner Mongolia Jinlian Aluminum Co., Ltd., the conclusion is drawn that the resource-saving coke roasting start-up technology is compared with the traditional roasting start-up process. The company achieved the result of saving 55 tons/cylinder of cryolite. From October 2013 to June 2015, it carried out large-scale industrial application of electrolyte instead of cryolite roasting. This technology has successfully started the electrolysis capacity of 600,000 tons for the company in the past three years. It saved a lot of materials and energy, created direct economic benefits of more than 90 million yuan, and achieved remarkable economic and social benefits, and promoted the development of circular economy.
Professor Gui Xiaobing of Guiyang Aluminium and Magnesium Design and Research Institute predicted that the replacement of cryolite by the electrolyte in the resource-saving roasting start-up technology can save the annual cost of China's electrolytic aluminum industry by more than 1 billion yuan, and the market prospect is broad and the social benefits are remarkable.
Wang Jianjun said that for a roasting start of a 200,000-ton 300kA tank electrolysis series, the amount of cryolite is usually about 40 tons per tank. If all the electrolytes are substituted for cryolite, the cost per tank is 160,000 yuan (according to cryolite and electrolyte difference 4000). Yuan meter). If the capacity of 2000 tons of electrolytic aluminum is converted according to the 300kA electrolytic cell, the annual saving cost is 760 million yuan.
On the other hand, social benefits are the most important. Domestic cryolite raw materials are mainly produced by fluorite, which causes the consumption of fluorite ore, a non-renewable strategic resource, and causes serious pollution of fluorine-containing wastewater or waste gas.
More importantly, as an electrolyte of by-products of electrolysis, if the measures are not taken into account in the production process, it may result in industrial wastes due to a large amount of accumulation, which not only causes a lot of valuable resources to be wasted, but also forms serious environmental pollution.
In addition, it also indirectly consumes industrial waste carbon residue in the production process of electrolytic aluminum. Carbon residue is a by-product of electrolytic aluminum production process, and the fluoride-containing salt is as high as 60% or more. After the successful development of this technology, the industrial waste carbon residue is from the previous People are interested in transforming into a camphor, using carbon residue flotation electrolytes to further realize the recycling and utilization of resources and promote environmental protection.
Therefore, whether it is economic benefit or social benefit, "electrolyte" replaces "cryolite" roasting start technology and truly leads China's electrolytic aluminum industry roasting start technology into a new era.