Research On High Gradient Permanent Magnetic Separating Desulphurization Of Micro-fine Coal By Dry Method Before Combustion

The thesis studies on the high gradient permanent magnetic separating desulphurization of micro-fine coal with dry method before combustion which can realize the online desulphurization of micro-fine coal furnace of fuel electric plant and top-blown converter of steel work. The research is as follows:On the research of fractal distribution of fine granularity, the sum of all granularities of sulfur content and ash content of fine coal agree with the fractal distribution according to the similarity generalization of material. Through the linear fit with origin 7.5, the correlation coefficient of fractal distribution model of sulfur content and ash content of fine coal is upward 0.93, which provides the theory law for the selection of proper granularity level to remove sulfur and reduce dust.The experiments on the magnetism of coal from He-bi, Luo-yang, Yan-kuang and Yi-luo show that the relative magnetic susceptibility are not constant and are greater influenced by intensity, granularity and ash content, which is caused by the different contained materials testified by the X-ray diffraction analysis.The experiment on the magnetic system of iron pyrites of Yi-ma coal series shows that the granularity is the main reason to influence the relative magnetic susceptibility of iron pyrites. In a certain range, with the decrease of granularity the relative magnetic susceptibility increases straightly to reach the maximum when the granularity is 325-500 meshes. The X-ray diffraction analysis testifies that the iron pyrite of 325-500 meshes granularity level contains the ferromagnetic materials such as Fe3O4. The orthogonal experiments of iron pyrite magnetism show that the granularity of iron pyrite and the addition of magnet powder influence the relative magnetic susceptibility of iron pyrites greatly.With the Euler-Lagrange method, the dynamical model of capturing magnetic particle in the high gradient magnetic field is established and simplified approximately as: u p≈kuf+upM. According to the calculated particle trace, the particle dynamics shows that the magnetic effort and the fluid effort are the main efforts to capture the magnetic particle in the high gradient magnetic field. Stronger is the particle magnetism, higher is the magnetic field and more powerful is the magnetism of magnetic medium, which is favorable to the capture of the particle.The encased extruded magnetic separator of the round sorting field is developed and the assemblage technology and clamping fixture of high gradient permanent magnetic system are made to protect the magnetic body and guarantee the assemblage quality during the assemblage course of magnetic system. The permanent magnetic separator is assembled well whose intensity of magnetic field reaches 1.14T.Through the parameter optimization of magnetic path with the software of Megnet 6.22, the extruded magnetic system can reach the best when the pole shoe thickness of soft iron reached 20 percents of the thickness of main magnetic body. To reduce the leakage and improve the usage of magnetic energy of permanent-magnet, the pole shoe of soft iron can insert into the separation field whose length should be controlled within 0.5mm. The simulation results of magnetic field distribution of radial magnetizing encased permanent magnet show that the inhomogeneity of magnetic field is decided by the shape of magnet, which provide the new method to the design of abnormity permanent magnetic path.The experiment system of high gradient permanent magnetic separator of micro–fine coal with dry method is built. The separation result shows that the coal granularity, the air speed and the filling ratio of magnetic medium influence the separation effectiveness greatly. When the air speed is 2.5m/s, the handling capacity is 6-8g/min, the filling ratio of magnetic medium is 7.5% and the magnetic field intensity is 1.14T, the micro-fine coal of 100~200 meshes can attain 66.06% productivity of float coal, 59.8% desulphurization ratio and67.59% reducing dust ratio after double separation. Test results show that permanent magnet HGMS desulfurization is entirely feasible.