Fine Coal Magnetic Desulfurization Mechanism Based On Synergy Of Microwave Energy And Medium

As extensive development of the mechanized mining and the rising productivity of fine coal, fine coal desulphurization is research hotspots in coal processing. Wet separation is hardly used as the fact that 2/3 of China’s coal reserves are deposited in western water-deficient areas, while efficient dry coal beneficiation for-0.5mm fine coal remains to be developed. Fine coal magnetic desulfurization technology based on synergy of microwave energy and medium was developed. Combining static magnetic field simulation with advanced testing method, the strengthening and reaction mechanism of pyrite, organic sulfur and harmful elements in high-sulphur coal were analyzed. The action mechanism that medium acted on the fine coal desulphurization was analyzed considering enhanced microwave absorption and magnetism of pyrite. The mechanism of medium enhanced absorption, secondary gradient effect, magnetic strengthen and surface oxidation were discussed.The distribution characteristics and wave absorbing properties of electromagnetic characteristic parameters in microwave energy response of fine coal were discussed. All the imaginary parts of complex dielectric constant for fine coal are small and microwave reinforcement falls within natural resonance loss mechanism. Reflection coefficient combined with electromagnetic parameters and microwave frequencies, was used to characterize the microwave absorption ability of fine coal.The relation between different microwave frequencies and microwave reflection loss.The effective medium theory equation of electromagnetic parameters for fine coal and neural network prediction model were developed. Microwave treatment response was analyzed and characterized for 12 harmful trace elements in fine coal. The sulfur groups(C-S) in-CH2-SH, O=S=O and C=S respond obviously. Neural network prediction models for electromagnetic parameters of real and imaginary part of complex dielectric constant and complex permeability were developed.This article investigated the surface oxidation magnetic strengthening and weakening mechanism of pyrite in the coal preliminarily. The results showed an inverse correlation between magnetic susceptibility increasing ratio and magnetic susceptibility while there was a positive correlation between the microwave time and pyrite content. The discipline of phase transition caused by chemical environment change was investigated based on mossbauer effect. Pyrite decreased and converted into pyrrhotite and troilite while the pyrite converted into pyrrhotite and marcasite.The model of the media Strengthen microwave absorption, according to the comprehensive analysis of reflection coefficient and discipline of microwave energy absorption enhancement mechanism of the medium to the fine coal, the physical model and discipline of microwave absorption enhancement mechanism of medium to the fine coal was put forward. The magnetic media increased the dynamic dielectric polarization relaxation and energy loss of magnetization relaxation, and the energy was transmitted from magnetic media to fine coal by conduction and radiation. The addition of magnetic media increased the microwave absorption and coal absorption bandwidth and improved the adaptability of coal to microwave pretreatment. The media is conducive to absorption peak of coal moving to the low frequency region.This paper interprets secondary gradient strengthening and medium synergy which was generated by chain groups. The magnetization saturation of magnetic particles is comparatively low. Its internal magnetic field intensity could appear constant value and is far below background field. The vector direction of magnetic field intensity is consistent with background field in the contact interface of magnetite, pyrite and pyrrhotite particles. The magnetization intensity of internal particles and the contact interface is negatively correlated with the value of adjacent relative permeability. Due to magnetic particles, the internal field intensity of particles is below background field. Magnetic flux density and magnetic field intensity of the particle is stronger than the value of background magnetic field and magnetic field in the contact interface. The magnetic field in the magnetic particles is negatively correlated with distance from the boundary of the magnetic particles. The magnetic field near particles is correlated with distance from the boundary of the magnetic particles. The interaction of particle chain could strengthen magnetic field intensity of the adjacent magnetic particles.A new method of fine coal desulfurization was put forward, enhancing magnetic separation with microwave and medium. The sulfur content of clean coal of Lu’an and Weinan coal were 2.15% and 2.92%, the yield were 92.10% and 91.97%, respectively by using rare earth magnetic roller type magnetic separator. The best medium content on RE magnetic drum/roller magnetic separator was 5% and 2%, the best size is 0.074-0.125 mm. Nitrogen atmosphere delayed optimal sulfur content of clean coal. The best sulfur content of concentrated product was improved with varying degrees.