How to melt copper
The most common melting methods are as follows:
– Blower furnace:
Although the widespread use of the flotation method for the preparation of high-grade ore has reduced the use of the blast furnace, but still a number of factories, especially in Japan and Africa, use it. A blast furnace is a device that works continuously and in which the cold charge descends from a vertical oven, simultaneously with the rise of hot gases (the result of the burning of coke and sulfides in the charge with air blown from near the bottom of the furnace). The result of this process is very effective drying, heating and melting of the charge, simultaneously with its descent for formations and slag in the bottom of the furnace.
Melting of copper sulphide materials in the blast furnace by lumps of metallurgical coke (which is obtained from the destruction of bituminous coal) and its amount reaches 5-10% charge. Coke is needed as a part of the fuel and on the other hand it creates the ability to penetrate and hold the charge. The rest of the materials that make up the load should also be lumpy so that the hot gases can rise through the spaces in the load. Therefore, copper-containing materials must be composed of large pieces of ore or high-grade ore that has been fused.
The products of the blast furnace are slag and molten matte, which are periodically removed after collection. The heat required for melting is produced by the combustion of coke and sulfur. In order to provide additional heat for the process, liquid (diesel) or gas (natural gas) fuels can be injected into the furnace through the bees.
– Flame furnace:
A flame furnace is actually a furnace in which the solid charge consists of graded ore, calcine (settled material) and lubricants along with copper-containing slag returned from the furnace and dust, up to 1200 or 1250 degrees Celsius by hot combustion gases that circulate throughout the bath. They are moving, see the heat. This furnace includes an oven lined with refractory materials (usually magnesite or chrome-magnesite) and its roof is fixed arched (silica) or suspended (magnesite). The flame furnace is heated by burning coal powder, oil fuel or natural gas at one end and produces hot gases that move throughout the furnace and melt the charge.
The products of the flame furnace are the molten slag that is separated and the molten matte that is sent to the converter to be oxidized and converted into hollow copper or blister. The slag mats are collected in the furnace and removed from it separately.
The flame furnace has two main problems: one is that it consumes considerable energy compared to other melting units (in the form of hydrocarbon fuels) and the other is that it produces a large volume of combustion gases that contain little SO2. It is difficult to effectively separate SO2 from gases with such a small concentration, and therefore flame furnaces cause problems in the field of air pollution. For this reason, in the future, the flame process will gradually be replaced by other melting methods, such as radiation, electric or continuous melting methods. Another possible suggestion is the direct hydrometallurgical recovery of copper from high-grade sulphide minerals, but this method is still in the research stages and the establishment of scouting units.
– Electric oven:
Melting in an electric furnace is similar to melting in a flame furnace, with the difference that no external fuel is used. The heat required for melting is caused by the resistance of the slag against the high amp current passing between the heavy carbon electrodes embedded in the slag. Using an electric furnace is economical, because the amount of heat released by gases, especially 2SO, is relatively small. However, electric energy is expensive and the use of electric furnace is limited only to areas where electricity is abundant and relatively cheap.
The electric furnace has the advantages of temperature control and regulation, and because it does not have combustion products, the oxidation conditions can be controlled well. These two factors cause excellent control of slag properties, such as menite concentration and viscosity, and as a result, the loss of copper in the slags of the melting stage is reduced.
– Radiation furnace:
All blast, flame and electric furnaces consume a significant amount of hydrocarbon fuel or electric energy for melting, while considerable energy can be obtained from the oxidation of their sulfide charge. In other words, melting in radiation furnaces causes considerable use of sulfide combustion energy by oxidizing part of the sulfide charge and using the released heat to melt the charge and slag.
The main advantages of radiation furnace processes are: little need for hydrocarbon fuel and easy removal of SO2 from the exhaust gases of these furnaces. The only drawback of this furnace is the relatively high loss of copper in the slag and dust coming out of the chimney, but most of this copper is recovered.
