Abstract
Particle sizing methods have gained considerable attention in the past few decades, but there is still a big challenge in high concentration situations (i.e., volume fraction>10%). However, the ultrasonic spectroscopy technique is a common tool for the noninvasive determination of essential parameters for high concentration systems by analyzing ultrasonic spectra with inversion algorithms, including the particle size distribution (PSD), volume fraction of each phase, and physicochemical properties. For the ultrasonic measurements, proper acquisition and analysis of ultrasonic spectra are becoming significant in order to understand the relationship between the unknown parameters and the ultrasonic spectra. In the work, an experimental setup was provided to synchronously acquire ultrasonic reflection and transmission signals. A series of experiments were performed on silicon-water solutions at volume fractions 8%, 10%, and 12% to obtain the ultrasonic attenuation spectra and ultrasonic phase velocity spectra based on different measurement methods, i.e., the pulse-echo method, reference reflection method, and through-transmission method, respectively. Based on the Epstein-Carhart-Allegra-Hawley (ECAH) forward model, genetic algorithm (GA) and optimum regularization technique (ORT) algorithms were implemented to determine PSD with the measured spectra; the obtained PSD was then compared with the optical microscope method. It revealed that the spectra obtained by different measurement methods showed individual features while the obtained PSD was consistent and the volume median diameters were within a deviation of 10% with GA and ORT algorithms. The differences and characteristics of these three measurement methods for signal acquisition and interpretation were discussed and presented to provide an evaluation and recommendation for ultrasonic particle sizing.
Highlights
With the rapid development of the industrial processes for chemical, material, and pharmaceutical productions and food processing, particle sizing technology has obtained considerable concerns and investigations [1, 2]
The corresponding volume median diameters (Dv50) and distribution width of the sample are shown in Table 2; it can be seen that the results obtained by the pulse-echo method are much closer to the reference reflection method than the throughtransmission method, and their volume median diameters have a relative deviation less than 2%, while the throughtransmission method deviates from the other two methods, yielding an error still less than 15%
To obtain the particle size distribution, the pulse-echo method, reference reflection method, and through-transmission method were employed to extract the ultrasonic attenuation and phase velocity spectra combined with the inversion algorithms genetic algorithm (GA) and optimum regularization technique (ORT)
Summary
With the rapid development of the industrial processes for chemical, material, and pharmaceutical productions and food processing, particle sizing technology has obtained considerable concerns and investigations [1, 2]. The most widely employed measurement techniques for particle size distribution (PSD) are based on static or dynamic light scattering and image analysis [5] Compared with these competitive approaches, the method of ultrasonic spectroscopy possesses the remarkable advantages in the highly concentrated suspension and even in the optical opaque medium, due to the strong penetrability of ultrasonic wave propagating through the medium [6,7,8,9]. Starting from analyzing ultrasonic attenuation and phase velocity spectra and comparing the inversed particle size and distribution, a comprehensive measurement method and a carefully designed experimental setup were proposed to provide a noninvasive way in synchronously acquiring these two kinds of ultrasound signals in the present work, which can effectively suppress the interference of different ultrasonic analysis methods in synchronous measurement. Characteristics of the above various measurement methods were discussed so as to facilitate a suitable understanding on the information content exploitation for characterizing particle size distribution in suspensions using ultrasonic spectra
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