B.Eng. Polymer of Chemical Engineering, Tianjin University, 2000
Electrostatic character & attrition of granular flow in pneumatic conveying system.
The induced current measurement was arranged on inclined pipe to test electrostatic current on the pipe wall, which was generated by the frictional contacts between the solid particles and pipe wall, during the pneumatic conveying process. With proper pipe connections, current induced on the surface of the pipe wall can be measured as a function of time. The details of the measurement methods have been described previously by Yao et al. (2004) and the measurement section is enlarged in figure 1, where the test section is divided into two parts and the experiment data can be obtained from top pipe and bottom pipe respectively in order to demonstrate if the electrostatic charge distribute on the pipe wall uniformly or not.
Figure 1 Induced current measurement section
Figure 2 Wall charge from integration of induced current
In order to verify whether electrostatic charge distributes on the pipe wall evenly or not, the induced current was measured on the top of pipe and bottom of pipe respectively, and then induced currents were integrated with time to obtain the charge on pipe wall (Yao et al. 2004) as shown in figure 2. It is observed that wall charge: at the top of pipe is greater than that at the bottom of pipe, which may be the explanation of the ring structure and demonstrate that charge distributed unevenly on the pipe wall. Therefore, according to the theory of the switch capacitor configuration, electrostatic charge would bring the influence to the ECT measurement.
Yao, J., Zhang, Y., Wang, C.-H., Matsusaka, S. and Masuda. H. Electrostatics of the granular flow in a pneumatic conveying system, Industrial and Engineering Chemistry Research, 43(22), 7181–7199, 2004.
Yao, J., Zhang, Y., Wang, C.-H. and Liang, Y.C. On the Electrostatic Equilibrium og Granular Flow in Pneumatic Conveying Systems, AIChE Journal, 52 (11), 3775-3793, 2006.
Zhang, Y., Wang, C.-H., Particle Attrition due to Rotary Valve Feeder in a Pneumatic Conveying System: Electrostatics and Mechanical Characteristics, Canadian Journal of Chemical Engineering, 84, 663-679, 2006.
Lim, E. W. C., Y. Zhang and C. H. Wang. Effects of an Electrostatic Field in Pneumatic Conveying of Granular Materials through Inclined and Vertical Pipes. Chemical Engineering Science, 61, 7889-7908, 2006.
Y. Zhang, W.C. Lim, and C.H. Wang, “Pneumatic Transport of Granular Materials in an Inclined Conveying Pipe: Comparison of CFD-DEM, ECT and PIV Results”, Ind. Eng. Chem. Res., 46, 6066-6083, 2007.
Y. Zhang, Y.C. Liang and C. H. Wang, “Hazard of Electrostatic Generation in Pneumatic Conveying System: Electrostatic Effects on the Accuracy of Electrical Capacitance Tomography Measurements and Generation of Spark”, Measurement Science and Technology, 19, 015502, 2008.
Yao, J., Zhang, Y., Wang, C.-H. Matsusaka, S. and Masuda, H. Electrostatics of the granular flow in a pneumatic conveying system, AIChE Annual Meeting 2004, Austin, Texas, United States, 7-12 November 2004.
Zhang, Y., Yao. J., Wang, C.-H. Electrical Capacitance Tomography Measurements on Inclined Conveying Pipes, 4th World Congress on Industrial Process Tomography, Aizu, Japan, September 2005.
Yao, J., Zhang, Y., Wang, C.-H. and Liang, Y.C. On the Electrostatic Field within Space of Pipe Induced by Granular Flow in a Pneumatic Conveying System, AIChE Annual meeting, Cincinnati, Ohio, USA, November 2005.