| Among the popular heavy medium separation equipments, the three-product heavy medium cyclone has been applied widely due to its superior sorting accuracy and less difficulty to control. The separation density of the first paragraph of three-product heavy medium cyclone has been controlled well relatively, and the ash of clean coal is controlled precisely, but Sec density control has a larger problem, on the one hand, the adjustment range of Sec density is small, merely achieve by adjusting the insertion depth of the overflow tube or replacing Sec underflow orifice offline. The more difficulty is that the middle ash can not be controlled to the most cost-effective level in the fluctuations of coal quality, so the coal preparation plant may loss or not meet customer’s demand. Therefore, for the three-product heavy medium cyclone, how to achieve the Sec controllable density online, and to achieve the efficient control of the quality of the coal, is an important research topic which is needed to address urgently.Literature about magnetic cyclone suggests that:the external magnetic field can affect the product quality of the magnetic minerals, the product quality affected by the magnetic field has flexible turning point. This paper proposes that two stage cyclone of three-product heavy medium cyclone is applied with magnetic field, by exploring the external magnetic field form, structure, position, the strength of the magnetic field and other parameters in order to get new ideas to adjust density separation on-line. Electromagnetic simulation and relevant literature review shows that ANSYS finite element analysis software can better describe the force and magnetic field distribution of the heavy medium (magnet powder) in the heavy medium cyclone in an external magnetic field, also can analyze the inner rule and essence of the heavy medium cyclone density control applied magnetic field from the perspective of mechanism analysis conveniently. Based on this, the paper adopts the magnetic field simulation, the measurement of magnetic field strength and the constructing of the separation experiment system and the physical simulation, explore the control mechanism and the realization way of the hydro cyclone density applied by the external magnetic field, on the basis of this, put forward the industrial amplification principle, design the prototype of the online control, develop the corresponding on-line measurement and control system, in order to provide useful reference to on-line control of Sec density regulation of three-product heavy medium cyclone.The analysis of heavy medium cyclone density field and force field shows that the distribution changes of magnet powder (magnetic field) near the enveloping surface decide the changes of heavy medium separation density. The magnetic system of the magnetic cyclone in the literature are analyzed, the J.SVOBODA type magnetic system is suitable for this study. On this basis,design the cyclone and the coil and build heavy medium cyclone separation experiment system with external magnetic field. Initially determine the extent of coil current and location of the coil, lay the foundation for the cyclone separation experiments.According to the empirical formula and validation experiments, do the overflow media yield experiments without coal in the magnetic field,determine different separation effect and its current range when the coil is located in the cone and cylinder:when the coil is located in the cylinder, the weak current can improve the yield of the overflow media;the coil is located in the cone, the strong current can reduce overflow medium yield.On the basis of the above experiment, do slime sorting experiment in heavy medium cyclone separation experiment system with external magnetic field. Found that, the coil position in cone and strong current can reduce the separation density to0, all of the raw coal to enter the underflow; the coil position in the cylinder and weak current can increase in the density of separation, the maximum appears in the coil position18and1.5A, the clean coal ash increases to16.8%from9.8%. That an external magnetic field can adjust the separation density provides the basis for industrial experiment of heavy medium cyclone follow-up.Use ANSYS software to analyze the magnetic field, discover the existence of the surface of zero radial force, the magnetic between the two zero-radial point to the wall, others point to the axis. The main part impacts on the density of the enveloping surface composed of two zero radial force surface space. Analyze the separation effect of coil position:coil position in the cone, heavy particles of raw coal, waste tailings with the outer swirl quickly into the underflow, the clean coal ash and yield rapid decline with the increase of the current; The coil in the cylinder and a conical upper part of the points selected light particles of raw coal, clean coal quickly with the rising swirl into the overflow, can greatly improve the clean coal ash and yield. The analysis suggests that reduces the coil axial thickness can fine-tune the separation density, it has been verified by thin coil experiment.Designe and develope a complete set of Sec separation density control system.As a reference to the magnetic force of the thin coil, designe the amplification coil for the industrial experiment,the structural parameters:inner diameter of800mm, outer diameter of1000mm, the axial thickness of200mm, nominal diameter2.5mm copper enameled wire. Analysis of the material of the cyclone,simulation results show that the iron shell will shield the magnetic field resulting in external magnetic field failures, so Sec cyclone of industrial-type experiment needs to use smaller material relative permeability of the metal aluminum, aluminum alloy or stainless steel.Calculate the magnetic field of the amplified coil to investigate whether comply with safety standards, find that more than the export limits, propose protection method. Develop separation density online regulation system of the second paragraph in3-product heavy medium cyclone based on s7-200PLC; build the hardware and software platform. Using MODBUS RTU protocol to control communication between PLC and HSPY Programmable DC power, achieve the purpose of control of the coil parameters. Using OPC achieve human-computer interaction for PLC and configuration, and design the human-machine interface based on WinCC V7.0software, the analysis of stability of signal transmission supports the system running normally. |
PDF Full Text Request