Copper is the earliest metal used by humans. As early as in prehistoric times, people began to exploit open-pit copper mines and used weapons to make weapons, tools and other utensils. The use of copper had a profound impact on the progress of early human civilization. Copper is a metal found in the earth's crust and ocean. The content of copper in the earth's crust is about 0.01%. In individual copper deposits, the copper content can reach 3-5%. Most of the copper in nature exists as a compound, copper mineral. Copper minerals and other minerals are aggregated into copper ore, and the copper ore mined is mined to become a copper concentrate with a high copper content.
First, performance
Copper has good physical and chemical properties such as electrical conductivity, thermal conductivity, corrosion resistance and ductility. Conductive and thermal conductivity are second only to silver. Pure copper can be drawn into very thin copper wire to make a very thin copper foil. The fresh section of pure copper is rose red, but after the surface forms a copper oxide film, the appearance is purple-red, so it is often called copper.
In addition to pure copper, copper can be alloyed with tin, zinc, nickel, etc. to form alloys with different characteristics, namely bronze, brass and white copper. When adding zinc to pure copper (99.99%), it is called brass. For example, ordinary brass tubes containing 80% copper and 20% zinc are used in condensers and automobile radiators of power plants; nickel is called white copper. The rest are called bronze. Except for zinc and nickel, all copper alloys added with other metal elements are called bronze. What elements are called are called elements. The most important bronzes are tin-phosphor bronze and beryllium bronze. For example, tin bronze has a long history of application in China, and it is used to cast bells, tripods, musical instruments and ceremonies. Tin bronze can also be used as bearings, bushings and wear parts.
Different from the conductivity of pure copper, the strength and rust resistance of copper can be greatly improved by means of alloying. These alloys are wear resistant, have good casting properties, and some have good mechanical properties and corrosion resistance.
Second, use
Since copper has the above excellent properties, it has a wide range of uses in the industry. Including electrical industry, machinery manufacturing, transportation, construction and so on. At present, copper is mainly used in the field of electrical and electronic industries to manufacture wires, communication cables and other finished products such as electric motors, generator rotors, electronic instruments, meters, etc., which accounts for about half of the total industrial demand. Copper and copper alloys play an important role in computer chips, integrated circuits, transistors, printed circuit boards and other equipment. For example, the transistor leads are made of a highly conductive, highly thermally conductive chromium-zirconium-copper alloy. Recently, IBM, an internationally renowned computer company, has used copper instead of aluminum in silicon chips, marking the latest breakthrough in the application of semiconductor technology to the oldest metal.
In the mid-1980s, the electrical industry accounted for the largest proportion of refined copper consumption in the United States, Japan, and Western European countries, and China was no exception. After entering the 1990s, foreign copper in the construction industry has grown tremendously, becoming the bulk of foreign consumption of copper. According to a report published by the Copper Development Association (CDA) in New York: In 1997, the construction industry was still a copper product of the United States. In the largest end-use market, the construction industry often uses the corrosion resistance of copper for the manufacture of water pipes, roofs and other water supply and drainage facilities. In addition, it is used for building decoration due to its aesthetic appearance. Copper for construction industry accounts for US copper products. The first place in total consumption.
According to the internal statistics of China Nonferrous Metals Group, the consumption of copper in China constitutes 77.7% of the electricity industry (including wire and cable) in 1997, becoming the largest market for copper.
The details are as follows: Unit: %
|
industry
|
Mid 80s
|
1997
|
|
United States, Japan, Western Europe
|
China
|
United States
|
China
|
|
Electrical industry
|
47.8
|
55.2
|
24.8
|
77.7
|
|
Machinery manufacturing
|
19.5
|
23.8
|
11.5
|
5.3
|
|
Construction industry
|
15.8
|
3.3
|
41.8
|
6.9
|
|
Transportation industry
|
8.8
|
3.3
|
12.8
|
4.4
|
|
other
|
8.1
|
14.4
|
9.1
|
5.7
|
|
total
|
100
|
100
|
100
|
100
|
Source: Futures Trading Dictionary * Copper Development Association (CDA)
Note: The 1997 China copper consumption structure data is derived from Simon Hunt's "1990-1997 China Copper Consumption Survey Report". In order to avoid double counting, China's wire and cable were included in the electrical industry in 1997, and previously calculated in In the mechanical manufacturing industry.
With the rapid development of science and technology, the application of copper is expanding, and copper has begun to play a role in medicine, biology, superconductivity and the environment. For example, when the polyurethane plastic foam contains copper or copper oxide, it can greatly reduce the deadly toxic gas released by the plastic when burning - hydrogen cyanide (HCN). A large number of research data prove that the bactericidal effect of copper can effectively reduce the spread of pneumonia bacteria, inhibit the growth of bacteria, and keep drinking water clean and hygienic. Therefore, the future development prospects of domestic construction copper pipes will be very broad.
Third, copper reserves:
The world's copper resources are relatively abundant. According to the statistics of the US Bureau of Mines in 1995, the world's copper metal reserves are 310 million tons, and the reserve base is 590 million tons. The countries with the largest copper reserves are Chile and the United States, accounting for 23.7% and 15.3% of the world's reserves respectively, followed by Poland. %, 6% in Zambia, 5% in Russia, 5% in Zaire, 4% in Peru, 4% in Canada, and 4% in Australia.
The industrial types of the world copper mines are classified into porphyry type, sand shale type, copper-nickel sulfide type, pyrite type, copper-uranium-gold type, natural copper type, vein type, carbonate type, skarn. There are nine types in total. The most important are the first four categories, accounting for 96% of the world's total copper reserves, of which porphyry and sand shale types each account for 55% and 29%. There are about 60 giant copper mines with a world copper reserve of more than 5 million tons, 38 porphyry mines, and 15 sandstone mines accounting for 88% of the giant copper mines.
There are few copper concentrate resources available for exploitation in China. At present, the major copper mines are Jiangxi Dexing Copper Mine, Tibet Yulong Copper Mine, Yulong Copper Mine and the newly discovered Xinjiang Ashele Copper Mine.
Fourth, copper smelting process
The copper ore mined from the copper ore is ore-selected to become a copper concentrate with a higher copper grade or copper ore. The copper concentrate needs to be refined and refined to become a refined copper and copper product.
At present, there are two main methods of smelting copper in the world: fire smelting and wet smelting (SX-EX)
1. Fire method:
Cathodic copper, also known as electrolytic copper, is produced by melt smelting and electrolytic fine smelting, and is generally suitable for high-grade copper sulfide ore.
In addition to copper concentrate, scrap copper is one of the main raw materials for refined copper, including old scrap copper and new scrap copper. Old scrap copper comes from old equipment and old machines, abandoned buildings and underground pipelines; new scrap copper comes from processing The copper scraps discarded by the factory (the output ratio of copper is about 50%), the supply of scrap copper is generally stable, and the scrap copper can be divided into: bare copper: grade is above 90%; yellow copper (wire): Copper material (old motor, circuit board); copper produced from scrap copper and other similar materials, also known as recycled copper.
2. Wet method:
A boat is suitable for low-grade copper oxide, and the produced refined copper is called electrowinning copper.
The wet smelting process is:
3. Characteristics of both fire and wet processes
Comparing the two copper production processes of fire method and wet method, it has the following characteristics:
(1) The latter's smelting equipment is simpler, but the impurity content is higher, which is a useful supplement to the former.
(2) The latter has limitations and is subject to the grade and type of ore.
(3) The cost of the former is about 70-80 cents/lb (about 1540-1760 USD/ton), and the latter is only 30-40 cents/lb (about 660-880 USD/ton).
It can be seen that the wet smelting technology has considerable advantages, but its scope of application has limitations. Not all smelting of copper mines can be used. However, through technological improvements, more and more countries in the past few years, including the United States, Chile, Canada, Australia, Mexico and Peru, have applied this process to more copper ore smelting. The improvement of wet smelting technology and the promotion of its application have reduced the production cost of copper, increased the production capacity of copper mines, increased the supply of social resources in the short term, and caused a relative surplus of total social supply, which has a pulling effect on prices. In 1997, the price of copper fell from the high of $2,600/ton in 1996 to around $1,600/ton in November 1998. This has a direct relationship with the large-scale low-cost copper listing due to the significant increase in the proportion of wet smelting processes.
At present, the average production cost of copper is 1400-1600 US dollars / ton (64-73 cents / lb), the price decline is a reasonable return to the value of value, with the increasing proportion of smelting process, the price trend of copper will Will be affected more and more profoundly. According to reports, the current minimum cost of wet copper smelting is only 20 cents / lb (450 US dollars / ton), the highest 77 cents / lb ($ 1697.5 / ton), an average of less than 50 cents / lb (1100 USD/ton). It should be noted that the average production cost of wet copper smelting in 1995 was only 39 cents/lb. Recently, the average production cost of wet copper smelting has increased, mainly because the wet copper smelting process has been extended to the treatment of copper vulcanization. The sake of minerals. The wet copper smelting process is more suitable for the treatment of copper oxidized minerals and lean ore. When dealing with sulfide minerals and rich ore, or when the mine is located in a cold area, the wet copper smelting process is used, and the production cost is also high. 50 cents/lb or more.
China began researching copper extraction technology from low-grade copper mines in the 1970s. In 1983, it established the first wet-smelting copper plant with an annual output of 120 tons. Recently, due to the introduction of foreign excellent copper extractants, plus local With the development of the copper industry, dozens of small wet smelters have been built, ranging in size from a few hundred to 2,000 tons, but the annual output of copper is only 15,000 tons, which is equivalent to the annual production of 1 million tons of refined copper in China. It is far from enough. At present, the production cost of copper in China is about 18,500 yuan, far higher than the world average of 1,477 US dollars (67 US cents). During the "95" period, the State Planning Commission and China Nonferrous Metals Industry Corporation listed the wet smelting project as a key research project, and built several demonstration plants in Dexing Copper Mine, Yulong Copper Mine and Daye Copper Mountain Copper Mine. After several years of hard work, it is estimated that by the end of this century, China's wet technology will have a great development, and the annual production capacity is estimated to reach 50,000 tons or more.
According to statistics, in 1980, the production of refined copper in wet copper smelting accounted for 2.5% of the world's refined copper production. In 1994, the proportion increased to 10%, and in 1997 it was estimated to increase to 18%. It is expected that the proportion of copper produced in the final wet process will increase to 25. -35% between.
