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Copper smelting is the process of separating copper metal from the rock in which it is naturally embedded by melting it. This is accomplished through a series of several processing steps. The term copper smelting may refer to this melting step in particular or it may refer somewhat less formally to the entire process overall.
In nature, copper, as well as many other metals, can be found embedded in rock. Such a combination of metal and rock is known as ore. For copper to be put to practical use, it must be separated from the rock and other metals and refined to acceptable purity. Each copper smelting operation has its own unique process, however many share similar basic steps.
A typical process might begin with grinding of the ore into a powder. This powder is processed with chemicals and air to separate out some of the unwanted material and concentrate the copper. Unwanted material from this step is referred to as the tailings. The tailings are typically disposed of in a tailings pond.
Concentrated material from this step is then dried and fed into a high temperature smelting furnace. As the concentrate is heated, different materials in it separate into layers. A layer of melted material containing copper, known as the matte layer, sinks to the bottom. Waste solids, called slag, float to the top. Slag and sulfur dioxide gases are removed and either discarded or sold while the matte layer moves on to the next step.
Matte is then poured into a converter where it reacts with air, lime, and silica to separate the copper from iron slag. The resulting copper from this step is known as blister copper. Blister copper undergoes further firing and purification to remove any remaining impurities.
One of the main side effects of the copper smelting process is the production of waste. Refining copper results in three and a half times as much waste as the amount of copper produced. This waste is not only in the form of solids that must be disposed of or recycled, but also sulfur dioxide gas. Sulfur dioxide is a significant air pollutant, particularly notable as a precursor to the production of acid rain. Some countries require remediation steps in copper smelting and other industrial operations to mitigate the negative environmental impact of the process.
Early copper smelting is thought to have originated in Western Asia sometime between 4000 and 4300 BC. Many historians believe ancient potters were likely first to discover this process. Their open-hearth firing furnaces would have been able to achieve the necessary high temperature. Simple campfires would not have burned hot enough to melt copper.
The majority of copper reserves are largely concentrated in a few regions including parts of the United States and Canada, Zambia, and the Andes Mountains. Modern copper smelting operations, however, are located around the world on all continents except Antarctica. While Antarctica is also a source of copper ore deposits, a long-term moratorium on mining in Antarctica was established in 1991 to preserve the area.