Roasting process of weakly magnetic iron ore

　　Weakly magnetic mineral can be changed into strong magnetic mineral through the way of roasting, which is habitually called Magnetic Roasting. But because the kinds of roasting mineral are different and chemical reactions produced in roasting are different, so roasting principle is slao different. It can de divided into rduction roasting, neutral roasting and oxidizing roasting according to roasting principle.

　　1. Reduction Roasting
　　 Reduction Roasting is situable for hematite and limonite. This roasting is done in the reductive situation. Commonly used reducing agents have carbon (C), Carbon Monoxide (CO) and hydrogen (H2). Roasting temperature of hematite is 550----600 centigrade, and hematite is reduced into magnetite, the reaction is as follows:
　　 3Fe2O3+C → 2Fe3O4+CO↑ (about 570℃)
　　 3Fe2O3+CO → 2FO +CO2↑ (about 570℃)
　　 3Fe2O3+H2→ 2F3O4+H2O↑ (about 570℃)
　　 Limonite hematite eliminates crystal water at first, then changes into hematite without water during the heating process and react according to the above reaction.

　　 2. Neutral roasting
　　 This roasting is situable for siderite, heat it to 300----400 centigrade when roasting under the circumstance of without pumping air or pumping a little air, siderite reacts according to the following reaction:
　　 Without pumping air: 3FeCO₃→ Fe₃O₄+2CO₂↑+CO↑(300—400℃)
　　 Pumping a little air: 2FeCO₃+1/2O₂→ Fe₂O₃+CO₂↑(300—400℃)
　　 3Fe₂O₃+CO →2Fe₃O₄+CO₂↑ (300—400℃)

　　 3. Oxidizing roasting
　　 Oxidizing roasting is situable for pyrite, which is roasted in a short time in the oaxidizing atmosphere (or pumping a lot of air) and oxidized into pyrrhotite. The reaction is as follows:
　　 7FeS₂+6O₂→ Fe₇S₈+6SO₂↑
　　 Prolong the roasting time, pyrrhotite is chaneged into magnetite according to the following reaction.
　　 3Fe₇S₈+38O₂→7Fe₃O₄+24SO₂↑
　　 This method is usually used to magnetic separate pyrite from rare metal concentrate ore by the means of roasting.