Reaction behavior and non-isothermal kinetics of suspension magnetization roasting of limonite and siderite

In order to develop limonite and decrease CO2 emissions, siderite is proposed as a clean reductant for suspension magnetization roasting (SMR) of limonite. An iron concentrate (iron grade: 65.92wt%, iron recovery: 98.54wt%) was obtained by magnetic separation under the optimum SMR conditions: siderite dosage 40wt%, roasting temperature 700 degrees C, roasting time 10 min. According to the magnetic analysis, SMR achieved the conversion of weak magnetic minerals to strong magnetic minerals, thus enabling the recovery of iron via magnetic separation. Based on the phase transformation analysis, during the SMR process, limonite was first dehydrated and converted to hematite, and then siderite decomposed to generate magnetite and CO, where CO reduced the freshly formed hematite to magnetite. The microstructure evolution analysis indicated that the magnetite particles were loose and porous with a destroyed structure, making them easier to be ground. The non-isothermal kinetic results show that the main reaction between limonite and siderite conformed to the two-dimension diffusion mechanism, suggesting that the diffusion of CO controlled the reaction. These results encourage the application of siderite as a reductant in SMR.

Automated summary

In order to develop limonite and reduce CO2 emissions, siderite is proposed as a clean reductant for suspension magnetization roasting (SMR) of limonite. The study successfully achieved the conversion of weak magnetic minerals to strong magnetic minerals through SMR, enabling the recovery of iron via magnetic separation. The use of siderite as a reductant in SMR has great potential and is encouraged.