The Study Of Polyethylene Particle Movement Behavior In Fluidized Bed

In this paper, according to the technical characteristics and current process methods of polythylene’s chlorinated and chlorosulfonated, it studied the movement behavior of polyethylene particles in the gas-solid fluidized bed reactor. Combined with polyethylene particle which has characteristics of small density, easy to take static with friction and small coherency, big expansion ratio, high viscoelasticity in fluidized bed reactor, design the fluidized bed reactor which is suitable for polyethylene’s chlorinated with gas-solid two phase method. Then it studied the polyethylene particles movement characteristics respectively in fluidized bed for the two kinds of distribution plate and the anti-static devices’ inhibiting effect of particle’s adhesion on the wall. By using the fluid mechanics simulation software FLUENT,based on the Eulerian-Eulerian multiphase models and PC-SIMPLE algorithm,establish a two-dimensional mathematical model of mass, momentum and energy transfer coupling, then simulate and analysis the polyethylene particles movement behavior in fluidized bed and the effect of different distribution plate cone angle within the fluidized bed properties. The works are as following:(1) According to the characteristics of polyethylene particles, design and manufacture design the gas-solid fluidized bed reactor which is suitable for polyethylene’s chlorinated. The main dimension is 0.9m of height and 0.12 m of diameter with a expanding section which is 0.28 m of diameter.The cyclone’s diameter is 0.09m;(2) Studied the electrification by friction in fluidized bed and designed several methods to reduce static from static generation and set the static guiding device;(3) The experiment studied the change of pressure drop, the behavior of bubbles movement, the radial and axial distribution of solid concentration and fluid velocity in fluidized bed of different gas distribution plate.(4) Simulated and analyzed the pressure drop,bubbles movement,distribution of solid concentration and fluid velocity, the trajectory of particle in fluidized bed with the fluid mechanics simulation software FLUENT;(5) Simulated the change of the gas-solid two phase flow characteristics with the change of distribution plate cone angle and compared with the experimental results and proved the model’s accuracy.The experiment and simulation results show that: Compared with Geldart B type particle,polyethylene has big expansion ratio and its gas-solid two-phase boundary is obvious in the fluidized bed; set the internal conductive device and moisturize the air can significantly reduce electrostatic accumulation in the bed;the distribution plate pressure drop increases with increasing of superficial gas velocity, decreased with increasing of the bed height; the concentration of particles show high on both sides and low of center in bed, high at the bottom and low on the top; the velocity show high in the center and at the bottom,and show low on both sides and the top; the gas-solid two phase exist circular motion from center to side in the fluidized bed; the conical distribution plate has higher bubble’s broken and coalescence frequency and smaller bubble’s size; the best angle of conical distribution plate range between40°~60°.The experimental results has an important guiding significance on the study of the light specific gravity particles as polyethylene, and also provides a theoretical basis for the dry process of polyethylene chlorinated.