Particle Size of Pneumatically Conveyed Powders Measured Using Impact Duration

Abstract

CSIRO Minerals has developed a technique for measuring particle size in pneumatically conveyed powders [1] by measurement of the acoustic waves produced by particle impacts upon a specially designed transducer. Previous work has focused on using the peak acoustic wave amplitude to determine particle size. This produces a spectrum that is hard to determine the particle size from, as the peak amplitude is a non‐linear function of particle diameter, and is strongly affected by angle of incidence and velocity of the impacting particle. In this paper impact duration measurements are used to overcome these difficulties while retaining the advantages of being able to measure in high solids loadings of up to at least 0.5 kg/m3 of powder. In laboratory tests the impact size monitor's (ISM) results have been correlated with optical diffraction measurements of the mean (by number) powder size with a correlation coefficient of 0.985 and a relative error of 5.5 %. The ISM operated successfully in the laboratory at a loading of 0.5 kg/m3 of powder and measured particles down to 50 microns in size.

Investigations into the sensing mechanism of acoustic emission sensors for particle size measurement in a particular case: normal incidence

“…By substituting equations (4) and (10) into equation (9), the relationship between the AE energy, impact velocity and radius of the particle can be described as…”

“…However, this method requires a complicated measuring system, which makes it impractical to be applied in power plants. Coghill [10] achieved size measurement of particles in a pneumatic pipeline using the duration of the AE signal, however, the low temporal resolution of this technique limits the measurement accuracy for on-line particle sizing.…”

Online Measurement of the Size Distribution of Pneumatically Conveyed Particles Through Acoustic Emission Detection and Triboelectric Sensing

“…d 3 . Coghill [13] designed a portable impact size monitor to intermittently measure the particle size of pneumatically conveyed particles. In their work a built-in AE sensor masked by a metal cap with a 2 mm diameter hole was temporally inserted to the flow line.…”

Vibration sensor for particle concentration measurement in pneumatic pipeline flows

“…A number of sensor designs have recently been proposed which are based on measuring the vibrations caused by impact of particles either with a bend in the pipeline wall [30] or with an obstacle introduced into the pipeline flow [23,24]. Impact sensors are often used in geophysical applications for measurement of particle motion near the ground.…”

“…For instance, Rickenmann and McArdell [31] used a piezoelectric impact sensor to measure bedload sediment transport rate in a stream, and Schaer and Islar [32] used an impact sensor to measure the effective size, density and velocity of snow particle clusters in avalanches. Coghill [23,24] designed an impact sensor for measurement of pneumatic particle transport. In this approach, particles collide with a rigid sensor arm that is held in the flow field, and the duration and amplitude of the acoustic pulse propagated on the sensor arm is measured.…”