There are generally two types of copper smelting methods in the world.

　　Currently, there are two main methods for copper smelting in the world: pyrometallurgy and hydrometallurgy (SX-EX).

　　I. Pyrometallurgy

　　Cathode copper, also known as electrolytic copper, is produced through smelting and electrolytic refining, generally suitable for high-grade copper sulfide ores.

　　In addition to copper concentrate, scrap copper, as one of the main raw materials for refined copper, includes old scrap copper and new scrap copper. Old scrap copper comes from old equipment and machinery, abandoned buildings and underground pipelines; new scrap copper comes from copper chips discarded by processing plants (the output ratio of copper materials is around 50%). Generally, the supply of scrap copper is relatively stable. Scrap copper can be classified into: bare miscellaneous copper with a grade of over 90%; yellow miscellaneous copper (electric wires) containing copper materials (old motors, circuit boards); copper produced from scrap copper and other similar materials is also called recycled copper.

　　II. Hydrometallurgy

　　Generally suitable for low-grade copper oxide, the refined copper produced is called electrowon copper.

　　III. Characteristics of Pyrometallurgy and Hydrometallurgy

　　Comparing the two copper production processes, pyrometallurgy and hydrometallurgy, they have the following characteristics:

　　1. The latter's smelting equipment is simpler, but the impurity content is higher, making it a beneficial supplement to the former.

　　2. The latter has limitations, constrained by the ore grade and type.

　　3. The cost of the former is approximately 70-80 cents per pound (about 1540-1760 USD per ton), while the latter is only 30-40 cents per pound (about 660-880 USD per ton).

　　It can be seen that hydrometallurgy has considerable advantages, but its scope of application is limited, and not all copper ores can be smelted using 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 operations in recent years. The improvement of hydrometallurgy technology and the promotion of its application have reduced copper production costs, increased copper mine capacity, and in the short term, increased social resource supply, leading to a relative oversupply in the total social supply, which has a pulling effect on prices. The futures price of copper fell from a high of 2600 USD per ton in 1996 to around 1600 USD per ton in November 1998, which is directly related to the significant increase in the proportion of hydrometallurgy, leading to a large amount of low-cost copper entering the market.

　　Currently, as the average production cost of copper is 1400-1600 USD per ton (64-73 cents per pound), the fall in futures prices is a reasonable return of price to value. With the continuous increase in its proportion in smelting processes, the trend of copper prices will be affected more profoundly. According to reports, the current lowest cost for hydrometallurgical copper production is only 20 cents per pound (equivalent to 450 USD per ton), with a maximum of 77 cents per pound (equivalent to 1697.5 USD per ton), averaging below 50 cents per pound (equivalent to 1100 USD per ton). It should be noted that in 1995, the average production cost of hydrometallurgical copper was only 39 cents per pound. Recently, the average production cost of hydrometallurgical copper has increased, mainly due to the extension of hydrometallurgy to treat copper sulfide minerals. Hydrometallurgy is more suitable for treating copper oxide minerals and lean ores. However, when treating sulfide minerals and richer ores, or when the mine is located in a cold region, using hydrometallurgy results in higher production costs, often exceeding 50 cents per pound.

　　China began researching copper extraction technology from low-grade copper ores in the 1970s. In 1983, the first hydrometallurgical copper plant was established, with an annual output of 120 tons. Recently, due to the introduction of excellent foreign copper extractants and the development of local copper industries, dozens of small-scale hydrometallurgical plants have been built, with capacities ranging from several hundred to 2000 tons, but the annual copper output is only 15,000 tons, which is far from enough compared to China's annual refined copper output of 1 million tons. Currently, China's copper production cost is approximately 18,500 yuan, which is significantly higher than the world average of 1477 USD (67 cents). During the 9th Five-Year Plan period, the State Planning Commission and China Nonferrous Metals Industry Corporation listed hydrometallurgy projects as key research initiatives. Several demonstration plants were built in places like Dexing Copper Mine, Yulong Copper Mine, and Daye Tonglushan Copper Mine. After several years of effort, it is estimated that by the end of this century, China's hydrometallurgical technology will see significant development, and the annual capacity is estimated to reach over 50,000 tons by then.

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

　　Unit: 10,000 tons

　　1980 1994 1997 1998

　　Proportion of hydrometallurgical copper production 2.5% 10% 18% 20%~25%

　　Hydrometallurgical copper output 24 108 172.3 225