Low carbon aluminum industry: the requirements of the new era

The transition to a low-carbon economy is the only way for China. China's aluminum industry is a major carbon dioxide emitter, accounting for about one-third of the world's total emissions in 2008, which has become the focus of attention. China's aluminum industry must meet the challenges of a low-carbon era and be brave enough to shoulder the responsibility of a low-carbon economy.

At the “Copenhagen Climate Summit” held in late 2009, low carbon and emission reduction became the focus of global attention. Low carbon, one of the hottest words in 2009, attracts the attention of people from all walks of life in the world and will gradually enter every corner of our economy and life.

In 2007, Chinese President Hu Jintao clearly stated that China should "develop a low-carbon economy." On September 22, 2009, President Hu Jintao reiterated at the UN Climate Change Summit in New York that China will further integrate climate change into its economic and social development plans. Premier Wen Jiabao of the State Council publicly promised to the world that by 2020, China's domestic GDP per unit of CO ₂ emissions will fall by 40% to 45% compared with 2005, and will be included as a binding indicator in the medium and long-term planning of national economic and social development. .

The transition to a low-carbon economy is the only way for China. This is not only to deal with climate change, but also the requirements of China's new development model. According to the International Energy Agency's forecast, China's energy-related CO ₂ emissions (carbon equivalent) will rise to 11.615 billion tons in 2030, an increase of 91.3% over 2007, equivalent to 16.0% of global CO ₂ emissions since 1890. It also accounted for 48.6% of the global carbon emissions (11.4 billion tons of carbon equivalent) during the period from 2007 to 2030. If we follow this line, not only will China not be sustainable, but it will seriously threaten the development and survival of the entire human race.

I. The aluminum industry welcomes the era of low carbon economy

Generally speaking, the basic characteristics of a low-carbon economy are: low energy consumption, low emissions, low pollution;

In the source composition, the proportion of new energy and renewable energy and nuclear energy is increasing.

(1) China's aluminum industry has a long way to go to achieve a low carbon economy

The level of technology and equipment for the production of primary aluminum and alumina in China is not lower than the international level, especially the primary aluminum extraction industry. In 2008, China's average electricity consumption was 14,300 kWh/ton of aluminum, and foreign countries were 15,396 kWh/ton of aluminum. China's average electricity consumption is 7.2% lower than that of foreign countries. Because China's self-baked anode electrolyzers are almost completely eliminated, the carbon dioxide emissions are not higher than abroad. But China's alumina extraction of energy consumption is much higher than abroad, China in 2008 to produce 1 ton of alumina average energy consumption of 800 kilograms of standard coal, while abroad but 500 kg of standard coal, 37.5% lower than the Chinese. The raw materials for bauxite used for foreign countries are all boehmite, and all of them are pure Bayer. More than 90% of the alumina in China is extracted from diaspore, and is extracted by pure Bayer.

Even though Pingguo Aluminum produces alumina in the Bayer process, the raw material is still diaspore. The average energy consumption and carbon dioxide emissions of the Chinese and foreign aluminum electrolysis industry in 2008 are listed in Table 1.

Table 1 Average energy consumption and carbon dioxide emissions of the Chinese and foreign aluminum electrolysis industry in 2008*

Remarks: * The information in this form is provided by Mr. Yao Shihuan.

In summary, although China's direct extraction of 1 ton of primary aluminum carbon dioxide emissions is only 10.3% higher than foreign countries, but the total amount of emissions is more than any other country in the world. In 2008, the global primary aluminum output was 42,540 kilotons, of which China's output was 13,180 kilotons, and its carbon dioxide emissions were about 70,777 kilotons, accounting for 49.5% of the total foreign emissions of 142,983 kilotons, accounting for almost half; accounting for 213,760 global emissions. 33.2% of kilotons. This is a number that cannot be ignored and should be taken seriously.

If the carbon dioxide emissions from indirect primary aluminum production are also included, it is a much bigger and more terrible figure. According to calculations, if the combined electricity consumption of producing 1 ton of primary aluminum is calculated at 15,000 kWh, the carbon dioxide emissions from thermal power plants are about 13 tons. If aluminum is produced by thermal power generation, the indirect carbon dioxide emissions of 1 ton of primary aluminum produced by China and foreign countries are almost the same. However, among the energy structures of primary aluminum produced abroad, hydropower and nuclear power account for a large proportion, such as Russia, Canada, the United States, Brazil, Venezuela and other countries, hydropower accounts for a large proportion. Nuclear power has a large share of the energy structure of the Western European aluminum industry. In China, in the energy structure of the primary aluminum industry, thermal power accounts for a large proportion and nuclear power is zero. Because China's existing nuclear power plants are in the coastal areas. The proportion of hydropower is also quite small. Therefore, China's direct and indirect carbon dioxide emissions from the production of 1 ton of primary aluminum are at least 22% greater than the foreign average.

(2) Achieving the goal of reducing emissions by 40%: the years are long and the road is hard

The carbon dioxide emitted by the aluminum industry is derived from the consumption of carbon and carbonaceous materials in the production process. In the next 10 years, it is very difficult to reach the goal of “the CO2 emissions per unit of GDP by 2020 will be 40% to 45% lower than in 2005” proposed by Premier Wen Jiabao. For example, in 2009, the average consumption of carbon anodes was about 435 kg/ton of aluminum. To reduce carbon dioxide emissions by 40%, the consumption of anode carbon blocks could not exceed 261 kg/ton of aluminum. Obviously, it can't be done under the existing technical conditions. Even in the laboratory, commercial production is difficult to achieve for almost a foreseeable period of time. From 1880 DC power consumption of 40,000 kWh / ton of aluminum to today's 13,000 kWh / ton of aluminum, it took more than 120 years, after five or six generations of tireless exploration and a large number of experiments. Today, the realization of the low-carbon aluminum industry will also be a long and arduous journey that will require several generations of efforts. Develop non-consumable anodes and wettable cathodes, reduce DC power consumption to 10,000 kWh/ton of aluminum or lower, or simply bid farewell to electrolysis. At that time, we can say that the green low-carbon aluminum era is coming to earth.

(3) Chinalco stands at the forefront of developing low carbon aluminum industry

Chinalco, the backbone of China's aluminum industry, is at the forefront of developing a low-carbon aluminum industry. In the creation of an international multi-metal mining company in the process, Aluminum Corporation of China in a comprehensive scientific development as a guide, always put energy saving as the company's policy to make some important leading indicators of energy consumption and production processes leading international level, some Has been ranked among the world's first. For example, the project “Development and Application of New Linear Feeder in Electrolytic Flue Gas Purification” and “Energy Saving Technology Research of Carbon Anode Baking Furnace Combustion Control System” developed by Qinghai Branch have achieved the expected results and reduced Energy consumption, reduced pollution, and obvious economic and social benefits; Jiaozuo Wanfang Aluminum Co., Ltd. successfully applied a ship-shaped anode to reduce anode unit consumption by 13 kg/ton of aluminum, and integrated AC power consumption decreased by 189 kWh/ton of aluminum and carbon dioxide. The emission is reduced by 331 kg / ton of aluminum; and so on.

Chinalco plans to phase out high-cost and backward aluminum production capacity of 200 kilotons/year and 1,000 kilotons/year of alumina capacity in the next three years. About 6.7% of production capacity will be closed before the end of 2011 and will be converted to existing ones. The 1,000 kiloton/year backward, high-cost alumina capacity has become a chemical grade alumina.

Adjusting product structure and industrial structure, and developing low-carbon products with high added value and low energy consumption are another measures taken by Chinalco to develop low-carbon aluminum industry. Continue to develop high value-added and high-tech aluminum, copper materials, to meet the needs of the development of military defense, has been fully affirmed the relevant state departments. China's aluminum industry's 200-tonne/year recycled aluminum project, which is built at a high starting point, can save 2.8 billion kilowatt-hours of electricity compared to the same-scale primary aluminum plant, and CO2 emissions can be reduced by about 102 kilotons per year. The first phase of the project was commissioned in 2008.

Chinalco Nanhai Aluminum Alloy Co., Ltd., invested and built by Chinalco, uses about 80% of scrap aluminum to produce extruded round ingots, which realizes the recycling of aluminum and has remarkable energy saving and emission reduction effects. It is a veritable low-carbon economy project. In terms of primary aluminum, Chinalco has gradually formed a cast aluminum alloy base represented by Baotou Aluminum and Shandong Branch, a rolling flat ingot production base represented by Guizhou Branch and Qinghai Branch, and Liancheng Aluminum Company. The casting and rolling strip production base represented by Qinghai Branch, etc., directly uses the original aluminum production and processing ingots and strips, eliminating the remelting of the processing plant, eliminating the remelting energy consumption and reducing the metal burning loss. Eliminate carbon dioxide emissions, reduce diesel energy consumption by 54 kilotons per year, reduce metal loss by about 11 kilotons, and reduce carbon dioxide emissions by about 73 kilotons.

Second, the low carbon road of the aluminum processing industry

The carbon dioxide directly discharged from aluminum processed materials and foundry products in the whole production process is only about 12% of the direct discharge of carbon dioxide from the original aluminum. The main processes of discharge are: aluminum ingot remelting, waste aluminum re-enrichment, and ingot homogenization. Preheating before hot working and various heat treatments. The most two emissions are the first two processes. Except for a few companies, the fuel used for remelting and re-aluminizing aluminum waste in China is mainly diesel and natural gas , and there is very little electric energy and other fuels. According to the author's investigation and calculation, the smelting aluminum (remelting ingot) emits about 90.3 kg/ton of carbon dioxide; the molten aluminum emits slightly more carbon dioxide. The reason for this is that the fuel consumed by melting the waste aluminum itself is slightly higher. Second, because the scrap aluminum is contaminated with oil and other dirt, it also consumes more fuel, so the carbon dioxide emitted is about 93.5 kg / ton of aluminum. Homogenization treatment, preheating, annealing, solid solution treatment, etc., if heated and insulated with fossil fuels, carbon dioxide will inevitably be emitted. All aluminum must be heat treated one or several times during the production process. As far as the whole country is concerned, the carbon dioxide emitted from the aluminum processing process (excluding smelting and casting) is about 1 kg/ton of aluminum; the castings and die-casting parts are less heat-treated, and the carbon dioxide emissions are calculated as 65 kg/ton of aluminum.

(1) Processing of aluminum and production of carbon dioxide from castings

In 2009, China produced and processed 12,350 kilotons of aluminum, and produced 4,540 kilotons of castings and die-casting parts; the processing volume of processed materials was about 18,450 kilotons, and the amount of castings and castings was about 5,800 kilotons. The comprehensive yield of processed materials is calculated at 70%, and the comprehensive yield of die-casting parts and castings is calculated at 78%. Their carbon dioxide emissions are shown in Table 2. Due to limited space, no carbon dioxide emissions were calculated for each aluminum and each heat treatment.

Table 2 Carbon dioxide emissions from China's aluminum processing industry and foundry industry in 2009

Remarks: 1 Calculated by 105.3% of production;

2 calculated by 103.5% of production;

(2) The development of low carbon aluminum processing industry and aluminum foundry industry

According to the data listed in Table 2, the total amount of carbon dioxide emitted by China's aluminum processing industry and aluminum foundry industry in 2009 was 4093.3 thousand tons, of which smelting accounted for 54% and heat treatment process accounted for 46%. In the production process, heat treatment of aluminum and foundry products is indispensable and must be carried out in processing plants and foundries. Only a small number of individual processes can be carried out in specialized heat treatment plants. Therefore, the energy saving and emission reduction of heat treatment is to improve the heat efficiency, improve the heat treatment process, shorten the heat time and adopt advanced heat treatment equipment.

The smelting and casting process has the most energy saving potential. This is not only because of the large amount of carbon dioxide it emits, but also because it can achieve huge energy saving and emission reduction effects by adjusting the production structure of ingots or cast products. For example, ingots and/or cast strips can be produced in an aluminum electrolysis plant, or ingots and/or cast strips produced from primary aluminum can be purchased from an aluminum electrolysis plant; die castings can be produced from primary aluminum and/or ) Castings can also be made from primary aluminum production poles. In 2009, ingots, die-casting parts, castings, cast strips, continuous casting strips, and wire rods produced directly from primary aluminum in China were less than 12%, and some industrialized countries have reached more than 65%. If China's ratio can reach 60%, according to the remelted aluminum ingots in 2009, it can reduce the carbon dioxide emissions by 1,325 kilotons. Why not?

The construction of a low-carbon aluminum industry is not simply about reducing carbon dioxide emissions, but also simultaneously reducing all emissions of environmentally unfriendly substances. Zero discharge of water should be done to minimize the emission of nitrogen oxides; no flux and chlorine should be used in the purification process of aluminum melt; solid waste should not be discharged or discharged as much as possible; comprehensive utilization and harmless use of waste deal with.

Third, the conclusion

Climate change is the most uncertain and greatest challenge facing the development of all mankind. Its scale is large, its scope is wide, and its influence is deep. At present, responding to global climate change has become the consensus of world leaders. The transition to a low-carbon economy is the only way for China's aluminum industry and a requirement for China's new development model. Since the new century, China's aluminum industry has entered a period of rapid development, and its development model is extensive. The aluminum industry is one of the industries with large energy consumption and one of the industries with more carbon dioxide emissions. The aluminum industry should fully implement the scientific development concept, do a good job of structural adjustment, rationally use resources, actively eliminate outdated equipment, and adopt energy-saving and less clean cleaning processes. The alumina and primary aluminum industries still have about 10% of the total production capacity, and the aluminum processing industry accounts for a larger proportion of backward production capacity, about 25%. For example, the energy-efficient melting furnace still accounts for a considerable share. The two-roll mill has not been extinct, the speed of most two-roll continuous casting mills needs to be improved, the supply structure of the ingots needs to be transformed, and so on.

The aluminum industry must actively respond to the challenges of the low-carbon era, take the responsibility of developing a low-carbon economy, and develop a roadmap for improving the development of low-carbon aluminum industry and aluminum enterprises.

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