5.3.3 Parametric spectrum analysis of backscattered ultrasound signals for the characterization of particles in suspensions

20. GMA/ITG-Fachtagung Sensoren und Messsysteme 2019
2019-06-25 - 2019-06-26
Nürnberg, Germany
5.3 Akustische Messverfahren
M. Vogt, M. Deilmann - KROHNE Messtechnik GmbH, Duisburg (Deutschland)
436 - 443


Suspensions, i.e. heterogeneous mixtures of solid particles in liquids, play an important role in various industries and applications. Especially in-line methods for analyzing the concentration and the size of the solid particles in a given suspensions are of large interest in chemistry and process industry, for example for monitoring and control of sedimentation processes in wastewater treatment plants. Further examples include the analysis of drilling mud, paints, and others. Ultrasound-based methods are a powerful tool for this task, because the ultrasound waves are scattered at the solid particles inside the liquid phase and, different from optical techniques, also allow for measurements with opaque media. In the case of a particles size much smaller than the ultrasound wavelength, as is given in many practical applications, Rayleigh backscattering occurs. Accordingly, the intensity of the scattered ultrasound waves is proportional to the fourth power of the frequency, i.e. the scattering phenomenon is largely frequency-dependent. This can advantageously be utilized for characterizing suspensions by a spectral analysis of the backscattered waves (echo measurement) or of the transmitted waves (transmission measurement). The goal of the work presented here was to develop a robust method for characterizing the concentration and the size of the particles by employing a parametric approach. This is achieved by fitting an analytical model to the spectra of acquired echo signals and by deriving quantitative parameters thereof. The proposed concept has been tested and validated by means of experimental echo measurements with ultrasound in the 2 MHz range.