Basic knowledge of copper
Copper is the earliest metal used by humans. As early as prehistoric times, people began to mine open-pit copper mines and use the copper they obtained to make weapons, tools and other utensils. The use of copper has a profound impact on the progress of early human civilization. Copper is a metal that exists in the earth's crust and the ocean. The content of copper in the earth's crust is about 0.01%, and in some copper deposits, the content of copper can reach 3-5%. Most of the copper in nature exists as compounds, namely copper minerals. Copper minerals aggregate with other minerals to form copper ore. The mined copper ore becomes copper concentrate with a high copper grade after beneficiation.
1. Properties
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. Pure copper can be drawn into very fine copper wires and made into very thin copper foil. The fresh cross section of pure copper is rose red, but after the copper oxide film is formed on the surface, the appearance is purple-red, so it is often called red 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 white copper.
Adding zinc to pure copper (99.99%) is called brass. For example, ordinary brass tubes with 80% copper and 20% zinc are used in condensers of power plants and car radiators; adding nickel is called white copper, and the rest are called bronze. Except for zinc and nickel, all copper alloys with other metal elements are called bronze. They are called what elements are added. 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 utensils. Tin bronze can also be used as bearings, bushings and wear-resistant parts.
Different from the conductivity of pure copper, with the help of alloying, the strength and corrosion resistance of copper can be greatly improved. Some of these alloys are wear-resistant and have good casting properties, while others have good mechanical properties and corrosion resistance.
2. Uses
Due to the above-mentioned excellent properties, copper has a wide range of uses in industry. Including electrical industry, machinery manufacturing, transportation, construction and other aspects. 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 motors, generator rotors and electronic instruments and meters, etc. This part of the consumption 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, transistor leads use highly conductive and highly thermally conductive chromium-zirconium copper alloys. Recently, IBM, an internationally renowned computer company, has adopted copper to replace aluminum in silicon chips, which marks the latest breakthrough in the application of mankind's oldest metal 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.
Since the 1990s, the use of copper for pipes in the construction industry has increased dramatically, becoming the largest copper consumer abroad. According to a report published by the Copper Development Association (CDA) in New York: In 1997, the construction industry was still the largest end-use market for copper products in the United States. The construction industry often uses copper's corrosion resistance to manufacture water pipes, roofs and other water supply and drainage facilities. In addition, it is also used in building decoration due to its beautiful appearance. The use of copper in the construction industry accounts for the first place in the total consumption of copper products in the United States. According to internal statistics from 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. With the rapid development of science and technology, the application scope 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 deadly toxic gas released when this plastic burns - hydrogen cyanide (HCN). A large amount of research data proves that the bactericidal effect of copper can effectively reduce the spread of pneumonia bacteria, inhibit bacterial growth, and keep drinking water clean and hygienic. Therefore, the future development prospects of copper pipes in the domestic construction industry will be very broad.
3. Copper reserves:
The world's copper resources are relatively rich. According to statistics from the U.S. 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 Poland 15%, Zambia 6%, Russia 5%, Zaire 5%, Peru 4%, Canada 4%, and Australia 4%.
The industrial types of copper mines in the world are divided into nine categories: porphyry type, sandstone shale type, copper-nickel sulfide type, pyrite type, copper-uranium-gold type, natural copper type, vein type, carbonate type, and skarn type. The first four categories are the most important, accounting for 96% of the world's total copper reserves, of which porphyry and sandstone 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, of which porphyry mines account for 38 and sandstone shale mines account for 15, accounting for 88% of the giant copper mines in total. There are very few copper concentrate resources available for mining in China. At present, the major copper mines are Dexing Copper Mine in Jiangxi, Yulong Copper Mine in Tibet, Yulong Copper Mine and the recently discovered Ashele Copper Mine in Xinjiang. 4. Copper smelting process The copper ore mined from the copper mine becomes copper concentrate or copper ore sand with a higher copper grade after beneficiation. The copper concentrate needs to be smelted and extracted before it can become refined copper and copper products. At present, there are two main ways to smelt copper in the world: pyrometallurgy and hydrometallurgy (SX-EX) 1. Fire method:
Cathode copper, also known as electrolytic copper, is produced through smelting and electrolytic refining, which is generally suitable for high-grade copper sulfide ores.
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 pipes; new scrap copper comes from copper scraps discarded by processing plants (the output ratio of copper materials is about 50%). Generally, the supply of scrap copper is relatively stable. Scrap copper can be divided into: bare scrap copper: grade above 90%; yellow scrap copper (wire): copper-containing materials (old motors, circuit boards);
Copper produced from scrap copper and other similar materials is also called recycled copper.
2. Wet method:
A ship is suitable for low-grade copper oxide, and the refined copper produced is called electrolytic copper.
The wet smelting process is:
3. Characteristics of the two processes of pyrometallurgy and hydrometallurgy
Comparing the two copper production processes of pyrometallurgy and hydrometallurgy, there are 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), while the cost of the latter is only 30-40 cents/pound (about 660-880 US dollars/ton).
It can be seen that hydrometallurgy technology has considerable advantages, but its scope of application is limited. Not all copper mines can be smelted with 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 mines in recent years. The improvement of hydrometallurgy 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, caused a relative surplus of total social supply, and had a pulling effect on prices. In 1997, the futures price of copper fell from the high of 2,600 US dollars per ton in 1996 to about 1,600 US dollars per ton in November 1998. This is directly related to the fact that the proportion of hydrometallurgical process has greatly increased, resulting in a large amount of low-cost copper being put on the market. At present, since the average production cost of copper is between 1,400 and 1,600 US dollars per ton (64-73 cents per pound), the decline in futures prices is a reasonable return of prices to value. As its proportion in the smelting process continues to increase, the price trend of copper will be more and more profoundly affected. According to reports, the current minimum cost of hydrometallurgical copper smelting is only 20 cents per pound (equivalent to 450 US dollars per ton), the highest is 77 cents per pound (equivalent to 1,697.5 US dollars per ton), and the average is about less than 50 cents per pound (equivalent to 1,100 US dollars per ton). It should be pointed out that in 1995, the average production cost of wet copper smelting was only 39 cents per pound. 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 sulfide minerals. The wet copper smelting process is more suitable for treating copper oxide minerals and poor ores, while when treating sulfide minerals and richer ores, or when the mine is located in a cold area, the production cost of wet copper smelting technology is also higher, mostly above 50 cents per pound. China began to study the technology of extracting copper from low-grade copper ores in the 1970s. In 1983, the first wet copper smelting plant was established, with an annual output of 120 tons. Recently, due to the introduction of excellent foreign copper extractors and the development of the local copper industry, dozens of small wet smelters have been built, ranging from a few hundred to 2,000 tons, but the annual output of copper is only 15,000 tons, which is far from enough compared with the annual output of 1 million tons of refined copper in my country. At present, the production cost of copper in my country is about 18,500 yuan, far 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 project as a key research project, and built several demonstration factories in Dexing Copper Mine, Yulong Copper Mine, Daye Tonglushan Copper Mine and other places. After several years of hard work, it is estimated that my country's hydrometallurgical technology will have a significant development by the end of this century, and the annual production capacity is estimated to reach more than 50,000 tons. According to statistics, the output of refined copper from hydrometallurgical copper smelting accounted for 2.5% of the world's refined copper output in 1980, and the proportion increased to 10% in 1994 and 18% in 1997. It is expected that the proportion of hydrometallurgical copper production will eventually increase to between 25-35%.
