Smelting process
Pyrometallurgical copper smelting
Cathode copper, also known as electrolytic copper, is produced through smelting and electrolytic refining, which is generally suitable for high-grade copper sulfide ores. Pyrometallurgy generally involves first increasing the copper content of the original ore with a few percent or thousandths of copper to 20%-30% through beneficiation, and then smelting the molten matte (matte) in a closed blast furnace, reverberatory furnace, electric furnace or flash furnace as copper concentrate. The molten matte (matte) produced is then sent to a converter for blowing into crude copper, and then oxidized and refined in another reverberatory furnace to remove impurities, or cast into anode plates for electrolysis to obtain electrolytic copper with a grade of up to 99.9%. The process is short and adaptable, and the copper recovery rate can reach 95%. However, because the sulfur in the ore is discharged as sulfur dioxide waste gas in the two stages of matte making and blowing, it is not easy to recover and is easy to cause pollution. In the 1990s, molten pool smelting such as the silver method and the Noranda method and Japan's Mitsubishi method appeared, and pyrometallurgy gradually developed towards continuous and automated.
Smelting copper from copper ore: Taking chalcopyrite as an example, first, the concentrate sand, flux (limestone, sand, etc.) and fuel (coke, charcoal or anthracite) are mixed and put into a "closed" blast furnace for smelting at about 1000°C. As a result, part of the sulfur in the ore becomes SO₂ (used to make sulfuric acid), and most of the impurities such as arsenic and antimony become volatile substances such as As₂O₃ and Sb₂O₃ and are removed: 2CuFeS₂+O₂=Cu₂S+2FeS+SO₂↑. Part of the iron sulfide is converted into oxide: 2FeS+3O₂=2FeO+2SO₂↑. Cu2S and the remaining FeS etc. melt together to form "matte" (mainly formed by the mutual dissolution of Cu2S and FeS, with a copper content between 20% and 50% and a sulfur content between 23% and 27%), and FeO and SiO2 form slag: FeO+SiO2=FeSiO2. The slag floats on the molten matte and is easy to separate, thereby removing some impurities. The matte is then moved into a converter, and after adding flux (quartz sand), air is blown in for blowing (1100-1300°C). Since iron has a greater affinity for oxygen than copper, and copper has a greater affinity for sulfur than iron, the FeS in the matte is first converted into FeO, combined with the flux to form slag, and then Cu2S is converted into Cu2O, which reacts with Cu2S to form crude copper (containing about 98.5% copper). 2Cu₂S+3O₂=2Cu₂O+2SO₂↑, 2Cu₂O+Cu₂S=6Cu+SO₂↑, then move the crude copper into the reverberatory furnace, add flux (quartz sand), and let in air to oxidize the impurities in the crude copper, which will be removed by forming slag with the flux. After the impurities are removed to a certain extent, heavy oil is sprayed in, and the reducing gases such as carbon monoxide produced by the combustion of heavy oil reduce cuprous oxide to copper at high temperature. The refined copper obtained contains about 99.7% copper.
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.
Wet copper smelting
A ship is suitable for low-grade copper oxide, and the refined copper produced is called electrolytic copper. Modern wet smelting includes sulfuric acid roasting-leaching-electrolytic, leaching-extraction-electrolytic, bacterial leaching and other methods, which are suitable for heap leaching, tank leaching or on-site leaching of low-grade complex ores, copper oxide ores, and copper-containing waste ores. Wet smelting technology is being gradually promoted, and it is expected to reach 20% of the total output by the end of this century. The introduction of wet smelting has greatly reduced the smelting cost of copper.
Domestic status
The copper smelting industry is a basic industry in the national economy. In particular, my country is in the stage of industrialization, and the demand for copper has maintained a high growth rate. The status of the copper smelting industry in the national economy will continue to improve.
World distribution
The world's copper ore resources are relatively rich. Copper is not difficult to extract from its ore, but the exploitable deposits are relatively scarce. Some, such as the copper mine in Falun, Sweden, have been a source of great wealth since the 13th century. One way to extract this metal is to bake the sulfide ore and then separate the copper sulfate formed by it with water. After flowing over the surface of the iron filings, the copper will precipitate, and the thin layer formed is easy to separate. The world's proven copper is about 350 million to 570 million tons, of which porphyry copper mines account for about 76% of the total. From the perspective of regional distribution, there are five regions with the richest copper reserves in the world:
Africa: Luilu (Kolwezi) in the Congo, Shituru, Luanshya and Baliba in Zambia, Mufulira, Nchanga TLP, Nkana (Rokana).
Asia: China Silver (Jinchuan)/Gansu, Shandong/Yanggu Xiangguang Copper Daye, Guixi, Huludao, Jinchang, Shanghai, Tianjin, Yunnan, India Parla Copper (Dahei), Tuticorin, Japan Besshi/Ehime (Toyo Smelter), Kosaka (Akita) Naoshima (Kagawa), Onahama (Fukushima), Saga Seki (Oita), Tamano (Okayama), Kazakhstan Balkashmis, Zhezkazgan Smelter, South Korea Onsan Smelter I, Onsan Smelter II, Philippines Isabel/Wright (Philippine Smelting and Refining Association), Uzbekistan Almalyk Smelter.
