Effect of Heating Rate on Pyrolysis Behavior and Kinetic Characteristics of Siderite

Yuexin Han,Xiaolong Zhang,Yongsheng Sun,Yanjun Li

doi:10.3390/min7110211

Abstract

The pyrolysis characteristics of siderite at different heating rates under the neutral atmosphere were investigated using various tools, including comprehensive thermal analyzer, tube furnace, X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrometry (EDS) and vibrating specimen magnetometer (VSM) measurements. The reaction of siderite pyrolysis followed the one-step reaction under the neutral atmosphere: FeCO3 → Fe3O4 + CO2 + CO. As the increasing of heating rate, the start and end pyrolysis temperatures and temperate where maximum weight loss rate occurred increased, while the total mass loss were essentially the same. Increasing heating rate within a certain range was in favor of shortening the time of each reaction stage, and the maximum conversion rate could be reached with a short time. The most probable mechanism function for non-isothermal pyrolysis of siderite at different heating rates was A1/2 reaction model (nucleation and growth reaction). With increasing heating rate, the corresponding activation energies and the pre-exponential factors increased, from 446.13 to 505.19 kJ∙mol−1, and from 6.67 × 10−18 to 2.40 × 10−21, respectively. All siderite was transformed into magnetite with a porous structure after pyrolysis, and some micro-cracks were formed into the particles. The magnetization intensity and specific susceptibility increased significantly, which created favorable conditions for the further effective concentration of iron ore.

Highlights

China is rich in siderite resources, which are difficult to exploit by traditional beneficiation methods
Magnetization roasting followed by magnetic separation was the most effective technology for the exploitation and utilization of siderite resources [1,2,3,4]
The pyrolysis behavior and kinetic characteristics are important to better understand and further improve the magnetization roasting for siderite

Summary

Introduction

China is rich in siderite resources, which are difficult to exploit by traditional beneficiation methods. The development of efficient utilization technology for siderite can increase the reserves of available iron ore, improve the tight situation of iron ore supply, and ensure the iron ore security of. Magnetization roasting followed by magnetic separation was the most effective technology for the exploitation and utilization of siderite resources [1,2,3,4]. The pyrolysis behavior and kinetic characteristics are important to better understand and further improve the magnetization roasting for siderite. Many studies have focused on the pyrolysis mechanism, including the conversion process, pyrolysis product characteristics and pyrolysis kinetics in the process of siderite magnetization roasting The siderite could be transformed to a highly magnetic mineral phase, while the magnetism of gangue minerals was barely changed, benefiting magnetic separation of the iron minerals and gangue minerals effectively [5,6,7,8,9].

Methods

Results

Conclusion