On-Line Simultaneous Measurement of Powder Flow Rate and Electric Charge of Particles in Gas-Solids Pipe Flow

Effect of air velocity on accuracy of measurement

Abstract

On-line measurement in gas-solids pipe flow was studied both theoretically and experimentally. The measurement is based on the amount of impact charge per unit time, namely, the current generated when particles are flowing through a pipe. In the new system, two detecting pipes made of different materials are installed in series, and the solution of the system-equations for the two generated currents brings about both the powder flow rate and the electric charge of particles simultaneously. The method is successfully applied in eliminating the initial charge effect which has often been pointed out. A characteristic value of electrification (particle charge per unit mass where effective contact-potential difference becomes zero) is an important factor in the computer treatment of the currents. The air velocity dependence of the characteristic value was experimentally clarified and the accuracy of the measurement was also evaluated. It was found that the accuracy became higher with increasing difference in the characteristic values between the two detecting pipes.