WHAT IS ELECTROLYTIC ALUMINIUM? When it comes to "electrolytic aluminium" , there are probably quite a few people who know it today; but what is electrolytic aluminium? I'm afraid the average consumer doesn't know much, and even fewer can say it.

Aluminum is a metal. Aluminum is widely used in electric power, transportation, construction, packaging, national defense, aerospace and people's life because of its light weight, good electrical conductivity, excellent processing performance and special oxidation resistance, from home construction to high speed rail and airplanes to food, cars and consumer electronics, some estimates put the use of aluminum in about 112 industries. What we call aluminum here is also called primary aluminum, which is pure aluminum. As the primary production of aluminum has always been based on molten salt electrolysis, it is usually called "electrolytic aluminum" .

ELECTROLYTIC ALUMINIUM -- a young metal. The earliest discovery and grasp of copper smelting technology, about 3000 ~ 4000 years ago, and human ironmaking history of more than 3000 years, as early as the Han dynasty ironmaking technology in China has been greatly developed. However, human aluminum smelting technology was only born more than 130 years ago. "because copper has a lower melting point than iron, people first learned to make copper and then iron, " said academician Yin Ruiyu, a well-known metallurgical scientist and expert on iron and steel metallurgy. "To make iron requires opening molecular bonds, while to make aluminum by reduction requires opening ionic bonds by Electrolysis, so people did not master the technology of making aluminum until they had a direct current. "

In 1886, a young American named Charles M. Hall invented a process for smelting aluminum called "the electrolysis of aluminum oxide in fluoride molten salts. ". But when he arrived at the United States Patent and Trademark Office to file his patent application, he learned that a Frenchman, PaulL.T.Héroult, had filed an application with the United States Patent and Trademark Office, again, to get aluminum, you put together roughly the same elements, almost exactly the same as Houle's invention. Meanwhile, Elot had filed for a patent in Europe a few months earlier. The two have since entered a long running patent battle that is said to have lasted 15 years.

After lengthy negotiations between Houle and Elot, the United States Patent and Trademark Office ruled in Houle's favor because elot did not submit the "original report" required. As a result of this ruling, Houle and Erut became the inventors of the same patent in America and Europe, which later became known as the "Houle-erut Aluminium electrolysis process" . However, Houle's relationship with Erut goes far beyond that. With the technical support of Houle and Erut, the two men founded aluminum metallurgical companies, respectively, today the world's leading aluminum companies are Alcoa (formerly Alcoa) and Pechiney (formerly SEMF) . Houle and Erut were destined for aluminum. They were born in the same year (1863) , died in the same year (1914) and filed the same patent in the same year (1886) . Even in an era marked by soaring wealth and massive accumulation, Houle's story became an American legend, winning the biggest fortune in American patent history. HOULE's stake in Alcoa at the time of his death in 1914 was worth nearly $30m.

The proud son of the new China. The First Electrolytic Aluminum Plant (Fushun Aluminum Plant) was built and put into operation in 1954. Until the 1980s, as an industrial industry or a product, the production process and industrial characteristics of electrolytic aluminum were little known to the public. With the development of electrolytic aluminum technology and the expansion of the production scale of electrolytic aluminum, together with the reputation of electrolytic aluminum "electric tiger" , in particular, since 2005, whether it is the "steel, cement, electrolytic aluminum, automobile, real estate" five major industries, or "steel, cement, electrolytic aluminum" three major industries Macroeconomic regulation and control policy, and "two high capital" of the restricted industries, electrolytic aluminum are on the list, the public has gradually known and recognized the electrolytic aluminum. It should be said that the formulation of "three major industries" or "five major industries" is a real "lift" for the electrolytic aluminum industry, as the national production capacity of one million tons of electrolytic aluminum in that year alone was less than 100 billion yuan in total output value, the total assets of ten billion yuan are not related to any big industry. Compared with several other industries, in 2005 China produced 350 million tons of crude steel and 1.07 billion tons of cement, but only 7.79 million tons of electrolytic aluminum. In any case, electrolytic aluminium, though small, is well known. But at the same time, "high energy consumption, high pollution" has also become a lingering electrolytic aluminum label.

After the founding of the PRC and even the early reform and opening up, China's electrolytic aluminum has always been a shortage of products, is classified as strategic materials, long-term dependence on imports. China's early electrolytic aluminum plant and the alumina plant with electrolytic aluminum has its own designation, such as the Fushun aluminum plant named 301 plant, Guizhou aluminum plant named 302 plant. From this similar to the confidentiality of military enterprises, enough to see the strategic position it was in. In April 1983, when the China National Nonferrous Metals Industry Corporation was established, the policy of "giving priority to the development of aluminum" was put forward and determined.

To thrive, as if never before. In the past 40 years of reform and opening up, especially since the end of last century, China's electrolytic aluminum industry has developed rapidly. After 2003, with the introduction of the National Macroeconomic Regulation and control policy, the electrolytic aluminum industry was not only not contained, but also explosive growth. In 1998, China's electrolytic aluminum production capacity is only 2.56 million tons per year, the output is 2.43 million tons per year. A little-known "big" industry, since then has constantly set new historical records: Power Generation Enterprises, coal enterprises began to invest in electrolytic aluminum, textile industry, breeding industry have also rushed to invest in the feast of electrolytic aluminum, there are private enterprises, state-owned enterprises and large state-owned enterprises. Some of the privately owned enterprises involved in aluminum have been among the richest in China, many of them have become the richest in a province, and many are on the rich list. People do not understand, what is the magic of electrolytic aluminum, can continue to attract a large number of inter-bank investment, set off a round of investment boom? In the 20 years from 1998 to 2018, China's electrolytic aluminum production capacity and output have exceeded 43.97 million tons and 36.48 million tons respectively. The output of aluminum has increased nearly 20-fold, accounting for 56.7 percent of the total world output, ranking first in the world for 17 consecutive years.

The rapid growth of aluminum in China's Non-ferrous metal family has rewritten the ranking of "copper, aluminum, lead, zinc... " to "aluminum, copper, lead, zinc... " and the success of electrolytic aluminum "hit back" to become the leader of the non-ferrous industry, the second largest metal materials. Today, no one questions the title of "big business" of electrolytic aluminium. With the continuous development of the electrolytic aluminum industry, in addition to its associated industries such as mining, alumina, aluminum processing, carbon and power generation, its scale and volume have reached a considerable degree, in fact, electrolytic aluminum has become an important basic raw material industry in our country, and its influence on our national economic construction can not be ignored.

So, since the new century, in the country repeatedly, under the strict restrictions of various decrees, what is the truth that led to the crazy development of electrolytic aluminum?

Is Electrolytic aluminum a high energy-consuming industry? There is no doubt about this, at present, each ton of electrolytic aluminum production consumes about 13000kWh ~ 14000kWh of electricity, plus the main raw materials and production process energy to produce a ton of electrolytic aluminum to consume 6 ~ 8 tons of standard coal. Up to now, however, electrolysis is still the only method for the industrial production of primary aluminum in the world. International giants such as Alcoa began to explore alternatives to electrolytic aluminium smelting in the 1960s, with no success so far.

There are several reasons for the rapid development of electrolytic aluminum: first, because electrolytic aluminum is an energy-consuming link in the whole aluminum industry chain, in the process of the follow-up application of aluminum products, it not only plays an irreplaceable role in other materials, but also shows its remarkable energy-saving effect in many fields, such as electric power, aerospace, transportation and so on. Second, because the aluminum is easy to oxidize to form a strong protective film, which will not be corroded in the process of using, the loss of oxidation of aluminum products is very little, and it is easy to be recovered. With a recovery rate of more than 95 per cent, aluminium can be recycled back and forth, earning it a reputation as a "storage product" and an "energy bank" . The regeneration and recovery of aluminum will greatly reduce its energy consumption in the future recycling. Third, the technical level of aluminum production in China is world-class, and its energy consumption is up to or has been lower than that of most developed countries, that is to say, the energy consumption of aluminum production in domestic aluminum enterprises is even lower than that of aluminum plants in the United States.

Although the energy consumption of electrolytic aluminium accounts for more than 7.9% of the total electricity consumption in China, the energy consumption of the whole electrolytic aluminium industry is even less than one-tenth of that of the domestic cars with hundreds of millions of units at present. Is electrolytic aluminum a highly polluting industry? To be precise, this statement is inaccurate and unfair. Fluoride, the main pollutant emitted during the production of electrolytic aluminum, is also the raw material needed for the production of electrolytic aluminum, the fluoride emitted in the form of flue gas has a natural affinity with the other main raw material of aluminum oxide produced by electrolytic aluminum. The reaction efficiency is over 99% . The "dry cleaning" system developed on this principle is widely used by aluminum plants all over the world. Excluding management factors, electrolytic aluminum pollution as early as the early 1980s, has not been a technical problem. What's more, the design of the production system of the modern electrolytic aluminum plant has already integrated the flue gas processing system and the raw material supply system as a whole, running continuously 365 days a year, without interruption.

There are strict environmental protection measures for a small amount of solid pollutants produced in the overhaul of electrolyzer. In recent years, the state of electrolytic aluminum environmental protection governance put forward more stringent standards and requirements. On the one hand, the limits on SO2 and other emissions from the flue gas of electrolytic aluminum have been increased; on the other hand, the new Environmental Protection Law of 2016 classifies most of the solid wastes discharged from the electrolytic process as hazardous pollutants. After a long period of Technology Accumulation and R & D and application in recent years, the corresponding treatment technologies have started to move towards industrialization, especially the technologies of electrolytic aluminum flue gas desulfurization and the treatment and comprehensive utilization of electrolytic aluminum overhaul waste residue have gradually matured, and used in industrial production. At present, the research and development of the recycling technology of electrolytic aluminum solid waste has also made positive progress.

Discover the truth -- how cool is electrolytic aluminum? Since the reform and opening up, China's economy is in the historical millennium of the development period, to the production of primary aluminum provides a broad space for development. However, what many people do not know is that the hard work and unremitting exploration of several generations of scientists and technicians in China's electrolytic aluminum industry have yielded fruitful results and amazing scientific and technological achievements, is China's electrolytic aluminum industry leading position behind the world behind the real internal reasons. Especially in the field of large-scale electrolytic aluminum technology, from scratch, from digestion and absorption to independent innovation, from the theoretical field to experimental development, and then to large-scale application and promotion, the design and production technology of aluminum electrolysis is improving day by day, formed their own design and technical system. Today, in the global area where there is an increase in electrolytic aluminum, there is China's figure. The electrolytic aluminum industry has become one of China's rare advantage industries in the world's manufacturing industry and even in the industrial sector. Under the guidance of the "Belt and Road" initiative, walk out into the world with your head held high.

The 40 years of scientific and technological innovation of Aluminum electrolysis in China is the 40 years of miracle jointly created by several generations of scientific and technological workers. Looking back over the course of 40 years, I can clearly see the magnificent paintings of scientific and technological innovation, in the past, the predecessors' deafening orders to tackle key problems and the earnest teachings when solving difficult problems still reverberate in mind... the introduction of "day light" technology speaking of electrolytic aluminum plant, old Comrades in the industry describe it like this: When you walk into an electrolysis workshop less than 10 meters away, you can not see people; when an electrolysis worker comes out of an electrolysis workshop, just like a coal miner, you can see a pair of eyes on the whole face. The Working Environment is harsh and unimaginable, this is also the first electrolytic aluminum production site to leave the impression. Before the 1970s, the self-baking anode electrolyzer technology imported from the former Soviet Union was the main technology in China's aluminum smelters, and the single series scale was not more than 10,000 tons per year. Aluminum plants with an annual output of more than 30,000 tons are national backbone enterprises. In the early 1980s, with the reform and opening up of the spring breeze, the national economy has ushered in a epoch-making changes in all fronts, China's industrial fields such as spring march, flowers blooming. Proceeding from the strategy of promoting the development of the national economy, the state has decided to introduce technology from developed countries to build a number of major engineering projects. The most typical is the construction of the first phase of the Baosteel project in Shanghai, which was conceived in 1977 and was inaugurated on the first day after the end of the Third Plenary Session of the 11th CPC Central Committee in December 1978. The State Council of the CPC Central Committee decided to set up a modern iron and steel joint enterpriseThis is also the first large-scale construction project voted by the National People's Congress in history. Probably many people know that the construction of Baosteel laid a foundation for the rapid development of China's iron and steel industry and its attainment of the world advanced level.

Why Choose "Day Light" technology? As in the case of the steel industry, the first year of reform and opening up was marked by the active advice and support of the older generation of aluminum industry experts, including Cheng Zonghao and Yao Shihuan, as well as the efforts and support of the former Ministry of Metallurgy, a number of large-scale aluminum plant construction has been included in the national plan, but the use of electrolyzer technology has become a difficult problem for decision-makers. At the end of the 1970s, the international aluminum companies such as Alcoa and Alfa have successfully developed large-scale pre-baked cell technology over 160kA ~ 180KA, and the aluminum electrolysis technology has begun to take large-scale and pre-baked as the leading development trend. Based on the technological development of electrolytic aluminium at that time, the group divided the world's advanced electrolytic cell types into three models and compared them, as recalled by Yao Shihuan and other predecessors:

The first type is the North American type electrolyzer. At that time, Alcoa was the world's largest multinational aluminum company, and Alcoa and Alcan used 150kA ~ 220kA pre-baked anode reduction cells ("pre-baked cells") in aluminum plants in Canada and Brazil, the advantages of the tank type are that alumina is added in the middle, the tightness is good, and more than 98% of the harmful flue gas can meet the requirement of environmental protection after being recovered. But this trough is a high efficiency, high trough voltage line, tons of aluminum power consumption is also relatively high, suitable for North America rich in hydropower and low electricity prices.

The second type is the European type electrolyzer. Is a French aluminum company (Pechiney) on behalf of the high price of electricity for the development of areas and a low power consumption of the trough. AS ITS 180KA pre-baked cell technology (AP18) is still at the experimental stage (only four cells have just been put into operation, although preparations for the f-series began in mid-1977) and as the most advanced 180kA technology just developed by Alfa, it's not likely to be transferred. Pechiney recommended to the Chinese side that the pre-bake tank with the maximum current of only 135 Ka was already in mature use at that time. With the addition of aluminum oxide on the side, 30% of the harmful gas was emitted in no organized way. This type of tank seriously polluted the environment, in some areas, sunroof washing has to be used for treatment, which is very expensive, and it is obvious that this technology is not suitable for our national conditions. The third type is the Japanese type. In the 1960s and 1970s, the aluminum industry in Japan developed rapidly, and Japanese companies introduced various trough types from the United States, France and Switzerland. After digestion and improvement, combining the advantages of environmental protection in the United States and low energy consumption in France, three companies have developed a low power consumption and airtight pre-baked cell with a capacity of 160kA ~ 170kA. Several Japanese aluminum companies, led by Japan Light Metal Corporation, began to recommend their large-scale pre-bake cell technology to China in 1976. And because of the friendly environment between China and Japan at that time, the adoption of Japanese technology could be supported by long-term loans from the Japanese government.

Since then, the former Ministry of Metallurgy sent a delegation headed by Wang Zhe, a member of the party group, and Cheng Zonghao, a secretary-general, to visit 10 electrolytic aluminum plants, carbon plants and aluminum processing plants among the 13 aluminum plants of six major aluminum companies in Japan. Finally, according to the investigation proposal, we decided to adopt Japan Light Metal Co. , Ltd. . 160kA large-scale intermediate feeding, closed pre-bake tank technology. February 21,1978, the original National Development and Reform Commission approved the Guizhou Aluminum Plant 80,000 tons of aluminum electrolysis project (referred to as your aluminum second electrolysis or your first 80,000 tons of aluminum) , January 7,1979, guizhou aluminum works has signed an 80,000-ton/year contract with Japan Light Metals Corp. for the construction and introduction of an aluminum electrolytic plant. A complete set of imported technology and equipment is based on the four newly tested electrolytic cells of the Japanese Light Metals Company at that time, the first 160KA intermediate prebaked cell series with low power consumption and good tightness was built in Guizhou Aluminum Plant —— Foshan No. 2 electrolytic aluminum plant of Guizhou Aluminum Plant. Guiyang Aluminum and Magnesium Design Institute (Guiyang Institute) was responsible for the design of the imported project, china No. 7 Metallurgical Construction Company is responsible for the construction and installation of 208 electrolytic cells with an annual capacity of 80,000 tons. December 18,1981, this was the largest domestic single-series capacity, the most advanced equipment of the formal commissioning of the aluminum electrolysis project. How to evaluate "Solar Light" technology? The introduction and construction of "Riqing" 160kA electrolytic series was the first large-scale pre-baked cell series in China at that time. In order to let you see clearly, its design features and main parameters are described as follows:

1 design current intensity 160 Ka, cell working voltage 4.05 V, current efficiency 87.5% , DC current consumption 13600 kwh/tAl, anode effect times 1 time/cell day; DC power consumption of more than 15000kWh/tAl, is a lot more advanced. The design mode of the two-terminal power-in was not the most advanced at that time, but the influence of magnetic field was taken into account, and the reasonable compensation of the slot bottom was carried out. 3 middle feeding method, two-point feeding, feeding container capacity 15kg, feeding 20 minutes once, every hour feeding volume 90kg, using pneumatic feeding device (clay trough control) , each trough with a dedicated fan at the end; The control system adopts effect control mode to control the concentration of alumina, and the design of the structure and quantity of the feeder is the biggest short board of the Japanese technology.

4 anode size 1400660540, anode group number 24, anode current density 0.72 a/cm2; anode selection proved to be reasonable, the later development of our country was basically improved on this basis; 5 anode lifting mechanism adopted four-point lifting, the utility model is a worm-turbine type mechanism with stable and reliable operation. 6 processing surface: Large Surface 525, small surface 595, anode seam 250. This is also one of the performance of backward design, is due to the European technology by the edge processing (feeding) of the impact of the processing area is larger. There are 208160ka electrolytic cells installed in the electrolytic workshop, which are located in four factory buildings, divided into 8 zones, each zone has 26 cells. The workshop adopts two-storey structure, operating platform is + 2.4 m, all steel structure workshop. The span of the two buildings is 20.5 m, the distance between the two buildings is 25 m, the distance between the electrolyzers is 6.575 M, which is decided by the operation requirement of the electrolyzers and the design of the bus configuration 5 T aluminum outlet package is transferred from overhead crane to short head of electrolyzer to complete aluminum outlet operation.

The technology of SCR rectification and dry flue gas cleaning of Fuji Company of Japan is adopted. The rectifier and flue gas purification systems are located at the two ends of the electrolytic shop, which is different from the configuration we have today. The advantage of this configuration is that the distance between the electrolyzer row and row can be smaller, each two plants (two rows of tanks) corresponding to a set of purification system. Because the length of the factory building is short, the distance of the flue gas pipeline is also short. This plan configuration was reasonable at that time, and this model was replicated in the design of the third electrolytic cell and Qinghai aluminum plant. With the increase of the scale of the series, our later designs were all based on the layout of the purification system between the electrolytic plants.

9 ALUMINA MATERIALS ARE TRANSPORTED IN TWO FORMS: FRESH ALUMINA FROM ALUMINA PLANT is fed into 8000t Bin (round steel bin) , and is fed into 400t daily bin by pneumatic conveyor (hock) and bucket elevator 85% fresh alumina is added to the purification system to absorb fluoride from flue gas, and the recovered fluoride alumina is fed into the 300 T fluorine-containing cell by hoists and hoists, the automatic-controlled electric trolley regularly delivers the loaded aluminum fluoride to each electrolyzer with a capacity of 5T tank wall for use in each electrolyzer; another 15% of the fresh aluminum oxide is fed into the electrolyzer through the overhead crane, as an anode heat preservation coating.

10 workshop equipped with 8 FRANCE ECL production of multi-functional operation unit, to complete the electrolytic cell out of aluminum, pole changing and lifting bus line and other major operations. Today's large-scale slot technology has changed a lot, the main core technology has changed, but in a lot of engineering details, the expert or can see the "day light" technology traces. I don't think I'll ever feel like I'm on the brink. There's something wrong with The Sun Light Technology! A lot of people still remember it. The development of things often goes beyond people's expectations. Because of the technology itself and the construction quality, operation level, management factors and other reasons, in the initial period of production as long as three or four years, there are various problems in the production and operation of the imported "solar light" electrolyzer, such as high temperature of the ELECTROLYZER, bad formation of the side of the furnace, too long extension leg, more precipitation at the bottom of the electrolyzer, frequent problems, low efficiency and high energy consumption. Especially prominent is the electrolytic cell early damage is serious, most of the cell life less than 1000 days (designed cell life 1500 days) .

As a major project introduced by the state, major problems will inevitably cause a great reaction, and even arouse the attention of state leaders. As the largest aluminum factory in the country, the industry benchmark, but also a famous brand in Guizhou enterprises, national leaders will visit Guizhou Aluminum Inspection, today you know Guizhou Moutai, do not know the 1980s, Guizhou aluminum than Moutai higher attention. Therefore, the project put into operation after the emergence of the problem, all aspects of the pressure is great. Han Peichuan, the first director transferred from the Guiyang Institute, was removed from his post amid intense tensions over design, construction and construction. So what is causing these problems?

On the one hand, of course, it is actively negotiating with the Japanese side, believing that the other side's technology is not mature (according to veteran comrades, the technology "Riqing" sells to China is indeed the latest, but there are only four industrial test pits) , from the legal point of view of the performance of the contract requires the other party to bear responsibility. Japan also feels aggrieved, although very active cooperation, but the Chinese side on its technology doubt or not recognized that the Chinese construction quality, production management problems. In fact, during the construction and commissioning of the project, there were incidents that caused conflicts between personnel from both sides because of lax supervision of the project: a Chinese personnel did not work according to the rules, which caused the Japanese personnel to be dissatisfied and started beating the Chinese personnel, because this matter also caused a diplomatic dispute, these have become other people's "evidence" . There were also a number of conflicts that were treated by many as anecdotes. In the early days of the reform and opening up, people today have a hard time imagining such things. As a result, the two sides launched a long-drawn-out research, analysis, verification, negotiations... . On the other hand, based on the domestic environment at that time, these issues attracted the attention of industry leaders and experts, and also stimulated the enthusiasm of universities, major design institutes and research institutes throughout the country, however, various views and opinions are not all the same, and certainly not all of them seem correct today. In retrospect, because of the impact of the "Cultural Revolution" in 10 years, the domestic technology base was relatively weak at that time, this discussion and research itself is very meaningful.

It's a big deal. In fact, the introduction of the second series of your aluminum electrolysis, aluminum industry and the whole society's high attention. During a long period from the early 1980s to the 1990s, it represented the highest level of China's electrolytic aluminum industry, and was also a model for many domestic electrolytic aluminum enterprises to learn and follow. In spite of all these problems, the majority of scientific and technological workers in the aluminum industry maintain a modest and Seek truth from facts attitude towards it, and learn and understand a lot of new technological concepts and technological achievements in modern aluminum electrolysis. The important decision to adopt the technology imported from Japan to build the second electrolytic series of your aluminum has kept the pace of rapid development of China's electrolytic aluminum industry in step with the reform and opening up, and opened the prelude to the development of China's modern large-scale aluminum electrolytic technology, it had a far-reaching influence on the development of China's electrolytic aluminum industry in the following 40 years. Today, the decision is very wise. While we are proud of today's development of Aluminium electrolysis, we should thank the old generation of aluminium industry scientists for their foresight and historic contribution to the industry.

Source: Non-ferrous metal, by Liang Xuemin