Charge measurement of dust particles in motion

Air-Solids Flow Measurement Using Electrostatic Techniques

“…If we assume the net charge is proportional to the solids velocity over the range investigated, as it was suggested by Gajewski [17] for PVC dust over the velocity range below 20m/s, equation 1.20 becomes where  max is the signal frequency up limit, M  is the solids mass flow rate. Hence the root mean square value of signal can be used to directly measure solids mass flow rate if the effect of velocity has been compensated.…”

“…The AC or noise measurement method, also known as "dynamic" method [15] takes the AC signal component to indicate flow concentration. Coulthard applied this technique to coal flow measurement in the Methil power station in Scotland [16], and Gajewski has employed it to measure dust in motion [17]. Gajewski further studied the measuring mechanism by combining the electrostatic field theory with electrical circuit analysis for a lined circular pipe wall sensor [18].…”

“…The amount of net charge carried by particles is actually affected by velocity. Gajewski [17] has studied the this effect on the 'charging tendency' of PVC dust, and Masuda conducted the tests on several different materials and found that the electrostatic meter's output was proportional to V  [14], where  varied from 1.4-1.9. The effect of velocity on the net charge has also been confirmed from many tests on pulverized coal [33].…”

Aerosol Measurement by Induced Currents

“…This idea is in itself not strictly new: the fact that charges on particles can induce currents in ring-shaped sensing electrodes has been recognized earlier; however, this idea was first only applied to the measurement of the number of charges on single coarse particles (Gajewski and Szaynok 1981), and later to the measurement of the flow speed of a discontinuous dust-laden flow (Gajewski 1983). Induced currents were used to measure the number of charges on single particles in the size range of 4-20 μm (Vercoulen 1995); for smaller single particles, the method was not sensitive enough.…”

Chargeability measurements of selected pharmaceutical dry powders to assess their electrostatic charge control capabilities

“…The sample inlet port was located at the top of the pipe, 1.041 m from the end. This is another feature that differentiates this design from the Gajewski and Szaynok 16 design, in which the sample powder was placed at the end of the pipe and then conveyed pneumatically through the sensor ring without emphasizing powder-surface interaction. Five identical stainless steel pipes were obtained from the same production batch to ensure the same internal surface roughness and composition.…”