Experimental Study On High-gradient Magnetic Separation For Desulfurization Before Combustion In Coal Magnetized In An Acidic Condition

The SO2 generated from coal-pyrite when coal is used for combustion is the main cause for serious pollution to the environment. What’s more, the high sulfur coal accounting for about 1/3 of the total reserves in China has increased the pollution degree. Therefore, coal desulfurization is of great significance. The author studied on Chongqing coal, Gansu coal and Luoyang coal by dry high gradient magnetic separation for desulfurization before combustion. Through inventing a new type of high gradient magnetic separator and realizing the improvement of the magnetization of pyrite in an acidic condition, we can improve the coal desulfurization effect.In terms of general magnetic separator, gradient of the magnetic field is low and magnetic matrices is easy to jam. The new type of high gradient magnetic separator can solve the problems. Rectangular magnets-conical magnetic medium system is designed in it., and cone angle is 60°, pole distance is 0.005m; A rotating disc structure is applied,so it can help the magnetic medium to enter and go out of magnetic field, which benefits separation; In order to avoid damage to the magnets, rectangular magnets will squeeze each other when the polarity is the same, while they will separate from each other when the polarity is different during the assembly of magnetic system.Without adding any iron ions, just adjusting the pH value of the slurry and controlling the reaction temperature in an acidic condition, the author realized the improvement of the magnetization of pyrite. In the experiment, the author investigated the effects of H2SO4 dosage, temperature, air velocity, FeCl3 dosage and FeCl2 dosage on the removal rate of coal, and identified the values of the parameters of the optimum conditions.Then, by the new type of high gradient magnetic separator, the author studied on Chongqing coal, Gansu coal and Luoyang coal. In the optimum conditions of the magnetic separator, the author studied on the desulfurization rate of different coal particle sizes, analyzed the relationship between desulfurization rate and particle size,and identified the value of the optimum particle size.When the optimum particle size is-0.074 mm, the desulfurization rate of Chongqing coal, Gansu coal and Luoyang coal increased by 22.77%,16.93%、19.99%, respectively.Through contrast and analysis of XRD images of pyrite before and after the process of magnetization, we can know that the new type of high gradient magnetic separator is feasible in magnetic separation. In addition, through PFC2 Dsoftware, the author studied on the change of the system parameters, recorded magnetic separation process vividly and revealed the mechanism of magnetic separation at particle level. At last, on the basis of the technology, the author put forward the possibility of the application of dry magnetic separation of pulverized coal in thermal power plant.