Research advances of electrostatics in pneumatic conveying granules systems
In past decades,the electrostatics of granules and granular flows has obtained more and more attention due to many industrial problems and development of new technologies.The collisions between granule-granule and granule-wall generate electrostatics.The occurrence of electrostatic can be affected by a variety of factors.As the contact between the granular and the wall,the accumulation of electrostatic charge on their surfaces can reach to an equilibrium state.The present work reviewed electrostatic generation and electrostatic equilibrium in pneumatic conveying granules systems.Two main contact charging ways between granule and wall(collision electrification and friction electrification),granular flow pattern and dynamic analysis were analyzed emphatically.The factors affecting the charging process of granules were discussed,including external conditions(temperature,relative humidity),granules geometry conditions(size,shape,contact area,roughness)and stress conditions.Besides,the numerical calculations of electrostatics in pneumatic conveying granules systems were introduced briefly.Finally,in order to clarify the mechanism of electrostatics in the pneumatic conveying granules systems,the physical mechanism of electrostatics in single granules was analyzed.This review revealed that the working mechanism of electron transfer due to collision or friction remains was not fully understood.These issues is expected to be resolved gradually in the future.
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