A Relationship between Electrostatic Charge and Solids Concentration in Pneumatic Conveying Systems

摘要

Nonrestrictive, electrostatic methods have been used for measuring concentration and velocity of pneumatically conveyed solids. The passive measurement is based on the phenomena that, during pneumatic transportation the solids particles can become naturally charged. These charges can be measured and, under certain conditions, used as an indication of the solids concentration. This method was observed experimentally and reported in the 1970's [1], however, theoretical analysis of the relationship between the solids concentration and the resultant charge has hardly been attempted.This paper derives a basic theoretical relationship between solids concentration and charges carried by flowing solids particles after making certain assumptions. Equations showing the relationship are presented. The flow noise, which generates stochastic signals on the electrodes, is expressed mathematically and related to the charge level. This theory will provide the basis for further analysis of the signal characteristics of pneumatically conveyed solids flow which eventually can be tested experimentally. The relationship between flow noise power spectrum and the cross correlation function is also expressed.