Weak magnetic minerals can be converted into ferromagnetic minerals by roasting, which is customarily called magnetization roasting. However, due to the different types of calcined minerals, the chemical reactions occurring during calcination are also different, so the principle of calcination is also different. According to the roasting principle, it can be divided into reduction calcination, neutral calcination and oxidative roasting.
(1) reducing the calcined product is suitable for roasting and hematite limonite, this calcination is carried out in a reducing atmosphere, the reducing agent used has carbon (C), carbon monoxide (CO) and hydrogen (H2). The calcination temperature of hematite is 550-600 °C, and hematite is reduced to magnetite.
In the heating process, limonite first removes the water of crystallization and turns into hematite without water.
(2) Neutral roasting This roasting is suitable for siderite. When roasting, it is heated to 300-400 ° C without air or a small amount of air.
(3) Oxidative roasting Oxidation roasting is suitable for pyrite. Calcined into pyrrhotite in a short time in an oxidizing atmosphere (or a large amount of air)
The calcination time is extended and the pyrrhot iron reaction becomes magnetite.
This method is commonly used in the separation of the metal concentrate with pyrite roasting from rare metals.
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