Continuous measurement of charge distribution in a single-jet fluidized bed using an electrostatic sensor array

In a gas-solid fluidized bed, repeated interaction and friction between particles and between particles and gas generate electrostatic charge, which affects the flow behavior of particles and the safe operation of the fluidized bed. Therefore, the measurement of charge distribution in a fluidized bed is important. However, there is limited research on the related techniques, especially measurement of electrostatic charge around bubbles in a fluidized bed. In this paper a continuous and non-intrusive measurement technique using a two-dimensional electrostatic sensor array is adopted. The sensor array consists of 4×8 electrodes. In addition, a pseudo two-dimensional fluidized bed is established and a single-jet nozzle is installed at the bottom of the bed for generating stable bubbles. The electrostatic sensor array measures the charge distribution of the fluidized bed using a charge reconstruction algorithm when the jet gas velocity ranges from 6.1 m/s to 10.5 m/s. Meanwhile, a high speed camera is used to acquire the images for the distribution of bubbles in the fluidized bed in order to verify the charge reconstruction method. The correlation coefficient between the shapes of the bubble measured from the electrostatic sensor array and from the high speed camera is about 0.8. Moreover, the amount of charge in the fluidized bed increases with jet gas velocity. The charge of the bubble reaches -20 nC with jet gas velocity of 10.5 m/s. The experimental results show that the electrostatic sensor array can be used to measure the charge distribution in the fluidized bed.