| The clean production of coal has become the significant focus of people’s attention all over the world,since China has been the largest country in coal production and consumption. The main purpose of cleaning coal is to improve coal quality. In coal preparation process,it needs to remove the non-combustible materials and the composition which is enviromentally harmful. It is also reduce the cost of transporting and handling of ash. Therefore,there is great significance for improving the environment in cleaning coal.Recently, Dense Medium Cyclone(DMC) is a rotating media sorting equipment which has a simple structure without moving parts of modern coal preparation industry to use, and also has high separation efficiency. It is mainly using centrifugal field for strengthening separation process. In the past,many scholars studied the separation performance of the dense medium cyclone by the means of experiment. However, in actual pocess, dense medium cyclone needs larger volume, resulting in high costs for test. So many scholars studied the separation performance of dense medium cyclone using microscopic mathematical simulation methods now. In this paper, it is used to computational fluid dynamics(CFD) methods to simulate and analyse flow field of for different geometries and different angles in dense medium cyclone.Simulation steps: Firstly,it uses Reynolds stress model(RSM) and Fluid Volume Model(VOF) to describe the free surface anisotropy of turbulence and liquid two-phase at a certain concentration and air mixture feed,and obtain the initial position and distribution of initial velocity of the air-core; Secondly,for magnetite particles of different sizes, the model has become the Mixture multiphase flow model from the VOF multiphase model. At the same time, it uses to viscosity correction model to predict the viscosity distribution of different magnetite particles,and obtain densities distribution, velocity distribution of particles of different size; Finally, is tracks the flow feature of coal particles by the Lagrangian particle tracking(LPT), and describs the performance of heavy medium cyclone with a distribution curve, split media separation performance ratio and so on.As a result,the DMC with an involute inlet has a better separation performance than that with a tangential inlet, since an involute inlet can weaken the effect of the short circuiting flow. The contracting inlet, i.e. the small inlet diameterinner inlet size can lead to a low Ep, particularly for fine particles. However, the medium feed rate is quite low with a smaller inlet size, since it causes more energy consumption. The DMC with a slope at the inlet has a higher medium feed rate and Ep for fine particles than that without one. A long body length can increase the medium feed rate, meanwhile presents a good separation performance, particularly for fine and heavy particles. A poor performance especially for fine particles is found in the DMC with relative larger vortex finder and spigot sizes. However, longer length of the cylindrical part can weaken the effect. The gas-liquid-solid multiphase flow of 1000 mm diameter of a factory of Dense medium cyclone(DMC) were simulated by changing the installation angle(-60 °~ 90 °). The results show that different installation angles can affect the separation performance of Dense medium cyclone. With the installation angles from-60° to 90°, operating pressure significantly reduces, and density deviation and overflow split ratio significantly increase at the same time. The DMC separation efficiency achieve peak with the installation angle of about 10 °, which the flow field is very stable. |
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