Copper smelting
Copper smelting
The copper ore mined from the copper mine becomes copper concentrate or copper ore sand with a high copper content after beneficiation. The copper concentrate needs to be smelted and extracted before it can become refined copper and copper products.
A. Electrolytic copper and refined copper
The copper used in industry includes electrolytic copper (containing 99.9% to 99.95% copper) and refined copper (containing 99.0% to 99.7% copper). The former is used in the electrical industry to make special alloys, metal wires and wires. The latter is used to make other alloys, copper pipes, copper plates, shafts, etc.
B. Copper smelting process
The development of copper metallurgical technology has gone through a long process, but copper smelting is still mainly based on pyrometallurgy, and its output accounts for about 85% of the world's copper output. Modern hydrometallurgical technology is gradually being promoted, and the introduction of hydrometallurgy has greatly reduced the smelting cost of copper.
Let's take a closer look at the two copper smelting methods of pyrometallurgy and hydrometallurgy (SX-EX).
a. 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 ore dressing, and then using it as copper concentrate for matte smelting in a closed blast furnace, reverberatory furnace, electric furnace or flash furnace. The resulting matte (matte) 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%. This process is short and adaptable, and the copper recovery rate can reach 95%, but 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 prone to pollution. In recent years, pyrometallurgy has gradually developed towards continuous and automated smelting, such as the silver method, the Noranda method, and the Mitsubishi method in Japan.
In addition to copper concentrate, scrap copper is also the main raw material 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 (wires); copper-containing materials (old motors, circuit boards); copper produced from scrap copper and other similar materials, also known as recycled copper.
b. Wet copper smelting:
A ship is suitable for low-grade copper oxide, and the refined copper produced is 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 in-situ 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.
The process flow chart is as follows: Among them, copper extraction (the process of copper entering the organic layer from the water layer) and back extraction (the process of copper entering the water layer from the organic layer) are important technological means of modern hydrometallurgy.
The two processes of pyrometallurgy and hydrometallurgy 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 higher than that of the latter.
It can be seen that hydrometallurgy technology has considerable advantages, but its scope of application is limited. Not all copper mines can be smelted using this process. However, through technological improvements, in recent years, more and more countries, including the United States, Chile, Canada, Australia, Mexico and Peru, have applied this process to more copper mines. 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.
