Copper is the earliest metal used by humans. As early as prehistoric times, people began to mine open-pit copper mines and use the obtained copper to make weapons, implements 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 oceans. The content of copper in the earth's crust is about 0.01%, and in individual copper deposits, the content of copper can reach 3-5%. Most of the copper in nature exists in the form of compounds, namely copper minerals. Copper minerals are aggregated with other minerals to form copper ore, and the mined copper ore is processed into a copper concentrate with higher copper content.

1. Performance

Copper has good physical and chemical properties such as electrical conductivity, thermal conductivity, corrosion resistance and ductility. The electrical conductivity and thermal conductivity are second only to silver, and pure copper can be drawn into very thin copper wires to make very thin copper foils. The fresh section of pure copper is rose red, but after the copper oxide film is formed on the surface, the appearance is purple, so it is often called red copper.

Copper In addition to pure copper, copper can be combined with tin, zinc, nickel and other metals to form alloys with different characteristics, namely bronze, brass and cupronickel. If zinc is added to pure copper (99.99%), it is called brass. For example, ordinary brass tubes containing 80% copper and 20% zinc are used in condensers of power plants and automobile radiators; adding nickel is called white copper , the rest are called bronze. Except for zinc and nickel, all copper alloys with other metal elements are called bronze. What element is added is called what element. The most important bronzes are tin phosphor bronze and beryllium bronze. For example, tin bronze has a very long history of application in my country, and is used to cast bells, tripods, musical instruments and sacrificial vessels. Tin bronze can also be used as bearings, bushings and wear parts, etc.

The electrical conductivity of pure copper is different, and the strength and corrosion resistance of copper can be greatly improved by alloying. Some of these alloys are wear-resistant and have good casting properties, and some have better mechanical properties and corrosion resistance.

2. Purpose

Because copper has the above-mentioned excellent properties, it has a wide range of uses in industry. Including electrical industry, machinery manufacturing, transportation, construction and so on. At present, copper is mainly used in the manufacture of wires, communication cables and other finished products such as electric motors, generator rotors and electronic instruments and meters in this field of the electrical and electronic industry, which accounts for about half of the total industrial demand. Copper and copper alloys occupy an important position in computer chips, integrated circuits, transistors, printed circuit boards and other equipment and devices. For example, the transistor leads use a chromium-zirconium-copper alloy with high electrical conductivity and high thermal conductivity. Recently, the internationally renowned computer company IBM has adopted copper to replace aluminum in silicon chips, which marks the latest breakthrough in the application of the oldest metal in human beings in semiconductor technology.

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, the use of copper for pipelines in the construction industry in foreign countries increased greatly and became the largest foreign copper consumption. According to a report published by the Copper Development Association (CDA) in New York, in 1997, the construction industry was still the largest copper product in the United States. The largest end-use market, the construction industry often uses copper's corrosion resistance for the manufacture of water pipes, roofs and other water supply and drainage facilities. In addition, it is also used for building decoration because of its beautiful appearance. The copper used in the construction industry accounts for the largest copper product in the United States number one in total consumption.

According to the internal statistics of China Nonferrous Metals Group, in 1997, the electrical industry (including wires and cables) accounted for 77.7% of my country's copper consumption, becoming the largest market for copper

The details are as follows: Unit: %

 

Industry Mid 1980s 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 15.8 3.3 41.8 6.9
Transportation 8.8 3.3 12.8 4.4
Others 8.1 14.4 9.1 5.7
Total 100 100 100 100

Data source: "Dictionary of Futures Trading" *Copper Development Association (CDA)
Note: The data of China's copper consumption structure in 1997 comes from Simon Hunt's "1990-1997 China Copper Consumption Survey Report". In order to avoid double counting, China's wire and cable in 1997 was included in the electrical industry, while the in the machinery manufacturing industry.

With the advancement of science and technology, the application range of copper is expanding, and copper has begun to play a role in medicine, biology, superconductivity and the environment. For example, when polyurethane plastic foam contains copper or copper oxide, it can greatly reduce the lethal toxic gas released when the plastic burns - hydrogen cyanide (HCN). A large number of research materials have proved 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 development prospects of copper pipes in the domestic construction industry will be very broad in the future.

3. Copper reserves:

The world's copper resources are relatively rich. 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 reserve base respectively, followed by Poland15 %, Zambia 6%, Russia 5%, Zaire 5%, Peru 4%, Canada 4%, Australia 4%.

The industrial types of copper deposits in the world are divided into porphyry type, sand shale type, copper-nickel sulfide type, pyrite type, copper-uranium-gold type, natural copper type, etc., vein type, carbonatite type, skarn type There are nine types. The most important are the first four categories, which account for 96% of the world's total copper reserves, of which porphyry and sand shale mines account for 55% and 29% respectively. There are about 60 giant copper mines with copper reserves of more than 5 million tons in the world, 38 porphyry mines and 15 sand shale mines, which together account for 88% of the giant copper mines.

There are very few copper concentrate resources available for mining 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, the smelting process of copper

The copper ore mined from copper mines is processed into copper concentrates or copper ore sands with high copper content.

At present, there are two main ways of smelting copper in the world: pyrometallurgy and hydrometallurgy (SX-EX).

  1. Fire method:

Cathode copper is produced by melting smelting and electrolytic refining, that is, electrolytic copper, which is generally suitable for high-grade copper sulfide ore.

In addition to copper concentrate, copper scrap is one of the main raw materials for refining copper, including old copper scrap and new scrap copper. Old scrap copper comes from old equipment and machines, abandoned buildings and underground pipes; new scrap copper comes from processing The copper scraps discarded by the factory (the output ratio of copper materials is about 50%), the general supply of scrap copper is relatively stable, and the scrap copper can be divided into: bare copper: the grade is above 90%; yellow copper (wire): containing Copper material (old motors, circuit boards); copper produced from scrap copper and other similar materials, also known as recycled copper.

  2. Wet method:

One boat is suitable for low-grade copper oxide, and the refined copper produced is called electro-deposited copper.

3. Characteristics of both fire and wet processes

Comparing the two copper production processes of fire method and wet method, they have the following characteristics:

(1) The smelting equipment of the latter is simpler, but the impurity content is higher, which is a beneficial 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 / pound (about 1540-1760 US dollars / ton), and the latter is only 30-40 cents / pound (about 660-880 US dollars / ton).

It can be seen that the hydrometallurgical technology has considerable advantages, but its scope of application is limited, and not all copper ore smelting can use this process. However, through technological improvements, more and more countries, including the United States, Chile, Canada, Australia, Mexico and Peru, have applied this process to more copper smelting in recent years. The improvement of hydrometallurgy technology and the promotion of its application have reduced the production cost of copper, improved the capacity of copper mines, and increased the supply of social resources in the short term, resulting in a relative surplus of the total social supply, which has a pulling effect on prices. The copper futures price in 1997 dropped from a high of US$2,600/ton in 1996 to around US$1,600/ton in November 1998, which is directly related to the large increase in the proportion of hydrometallurgical smelting technology, which led to the listing of a large number of low-cost copper.

At present, since the average production cost of copper is 1400-1600 US dollars / ton (64-73 cents / pound), the decline in futures price is a reasonable return of price to value. With the continuous increase of its proportion in the smelting process, the price trend of copper will be will be more and more profoundly affected. According to reports, the current minimum cost of copper hydrometallurgy is only 20 cents/lb ($450/ton), the highest is 77 cents/lb ($1,697.5/ton), and the average is less than 50 cents/lb ($1,100/ton). USD/ton). It should be pointed out that in 1995, the average production cost of copper hydrometallurgy was only 39 cents/lb. The average production cost of copper hydrometallurgy has increased recently, mainly due to the extension of the copper hydrometallurgical process to the sulfide treatment of copper. for the sake of minerals. The hydrometallurgical copper smelting process is more suitable for the treatment of copper oxide minerals and poor ores, but when dealing with sulfide minerals and richer ores, or when the mine is located in a cold area, the hydrometallurgical copper smelting process is used, and its production cost is also relatively high. 50 cents/lb or more.

China has been researching copper extraction technology from low-grade copper mines since the 1970s. In 1983, the first hydrometallurgical copper smelting plant was established, with an annual output of 120 tons. With the development of the copper industry, dozens of small hydrometallurgical smelters have been built, ranging in scale from several hundred to 2,000 tons, but the annual output of copper is only 15,000 tons, which is similar to the scale of my country's annual output of 1 million tons of refined copper. It is far from enough. At present, the production cost of copper in my country is about 18,500 yuan, which is much higher than the world average of 1,477 US dollars (67 cents). During the "95" period, the State Planning Commission and China Nonferrous Metals Industry Corporation listed the hydrometallurgical smelting project as a key research project, and built several demonstration factories in Dexing Copper Mine, Yulong Copper Mine, Daye Tonglushan Copper Mine, etc. After several years of hard work, it is estimated that by the end of this century, my country's wet process technology will have great development, and the annual production capacity is estimated to reach more than 50,000 tons.

According to statistics, in 1980, the refined copper output of hydrometallurgy accounted for 2.5% of the world's refined copper output. In 1994, the proportion increased to 10%, and in 1997 it was estimated to increase to 18%. It is expected that the final proportion of wet copper production will increase to 25%. -35%.