Sensitivity of particle sizing by ultrasonic attenuation spectroscopy to material properties (original) (raw)
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Effects of Material Viscosity on Particle Sizing by Ultrasonic Attenuation Spectroscopy
Procedia Engineering, 2015
Ultrasonic spectroscopy is becoming a promising particle measurement technique for the characterization of emulsions and suspensions over a wide range of particle size and concentration especially in the petrochemical, pharmaceutical, adhesives, food and other industries. Compared with other competitive methods like laser diffraction, dynamic light scattering and image analysis, the approach of ultrasonic attenuation spectroscopy possesses significant superiority in the highly-concentrated particulate twophase flow measurement even in the optical opaque medium, due to the high penetrability of ultrasonic waves through medium, as well as in situ non-invasive measurement and low cost but endurable apparatus. Typically, the overall process by which the particle size distribution of a suspension is measured using ultrasonic attenuation spectroscopy can be divided into two parts: the measurement of frequency-dependent ultrasonic attenuation in two-phase system, and the inversion calculation based on the prediction of mathematical model. The modeling process relies on the fundamental relationship between attenuation spectrum and physical properties, where viscosity could be a critical and complex property because its quantity can influence the ultrasonic attenuation seriously and ultimately the inversion calculation of the resultant particle size distribution. In this paper, a variable viscosity experimental system has been established through changing the concentration of aqueous glycerol solutions or the temperature of glycerol solutions. For the sample of micron-sized glass beads, a series of experiments have been carried out to obtain the attenuation spectrum, which were predicted and interpreted using the ECAH (Epstein, Carhart, Allegra and Hawley) model simultaneously. Hence, the particle size distribution of the glass beads can be retrieved through the inversion calculation.
Dependence of ultrasonic attenuation on the material properties
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2000
Ultrasonic spectroscopy is a promising measurement technique for the characterisation of emulsions and suspensions over a wide range of particle size and concentration. It appears highly suitable for on-line applications, in particular for dense nano-sized particle systems, where the system stability may be very sensitive to changes in the concentration. In the case of colloidal dispersions the particle sizes are usually smaller than the sound wavelength. Then dissipative processes rather than scattering govern the acoustic behaviour of such systems. The dissipative processes, however, are affected by several material properties, whose significance for the overall acoustic behaviour depends on the type of the material system, e.g. thermal properties are important in the case of emulsions and non-watery suspensions but not for watery suspensions. Often the information on these parameters is incomplete and not sufficiently accurate. In this paper the stability of ultrasonic particle size measurement against incorrect values of the relevant material properties is investigated. This was done firstly by analytical consideration. From this, the degree of influence of the respective material properties on the analysis of spectrometric measurements was derived for oil-water-emulsions, watery and non-watery suspensions. It could be shown that the single properties affect the analysis very differently. In a second step, the conclusions obtained analytically could be confirmed by analysing experimental attenuation spectra with slightly changed material property data. The paper is intended to give users of ultrasonic spectroscopy a practical guide for deciding which material properties have to be obtained with high accuracy and which can be estimated. : S 0 9 2 7 -7 7 5 7 ( 0 0 ) 0 0 5 7 1 -9
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999
The particle size distribution of particles in liquid-based suspensions and emulsions is an important parameter in a wide variety of industrial applications. Many particle-sizing methods require the transmission of light through a sample of the system, and therefore these particulate systems must be severely diluted. Many systems are unstable on dilution and therefore have to be measured at high volume concentration. Sound waves interact with both the suspending medium and the dispersed phase and are able to propagate through concentrated systems. The development of new ultrasonic transducer technology together with advances in digital signal processing has opened the way for a powerful new analysis termed acoustic attenuation spectroscopy. The technique consists of propagating ultrasonic waves of a range of frequencies through the particulate system and accurately measuring the attenuation at each frequency. This attenuation spectrum can be converted to a particle size distribution and a measure of the concentration of the dispersed phase. It offers the particle technologist the means to monitor and control particle formation and reduction processes.
Effects of impurities on particle sizing by acoustic attenuation spectroscopy
Powder Technology, 2010
It is important to have correct information regarding particle size in order to interpret, control, and optimize many industrial processes. Prior to the recent advent of acoustic attenuation spectroscopy, it was difficult to study particle size distribution online and under real process conditions in processes involving concentrated dispersions (suspensions or emulsions). The technique still needs improvement because it is less known how and under which conditions to employ the technique when dispersions involve impurities that could be soluble, insoluble, in the form of additives, and so on. This lack of understanding has almost halted the advancement in applications of the technique to various processes that essentially involve dispersions with impurities. This study investigates aqueous suspensions of CaCO 3 at different concentrations (i.e., 5%, 10% and 20% mass/mass) with added impurities of MgCO 3 (insoluble impurity), NaNO 3 (soluble impurity) and sodium polyacrylate (soluble additive) at varying proportions (5%, 10%, 20% and 30% of the weight of CaCO 3). The study characterizes and compares dispersion with and without impurity in order to demonstrate the possible ways in which addition of an impurity change the original acoustic attenuation spectrum of a dispersion. The study brings the conditions in which acoustic attenuation spectroscopy is capable of explaining that addition of an impurity will not change original particle size of the disperse medium.
2010
The inherent ability of ultrasonic wave to propagate in dense and opaque suspensions makes it a desirable method for online measurement of particle size distribution in industrial operations. The ability of ultrasonic attenuation spectroscopy to determine particle size distribution has been extended to dense suspensions of particles lying predominantly in the intermediate wave propagation regime at the measurement frequencies. This was achieved by accounting for the effect of detector size and shift in the frequency spectrum under dense conditions in the theoretical model and deconvolution algorithm, respectively. The proposed modifications enable the application of this technique in various industrial processes requiring in situ and real-time measurement of particle size distribution such as crystallization, mineral processing and food processing. V
Characterization of solid liquid suspensions utilizing ultrasonic measurements
Proceedings of the 20th IEEE Instrumentation Technology Conference (Cat. No.03CH37412), 2003
Rapid, on-line determination of particle size and concentration is required for the efficient process measurement and control of many processes in government and industrial applications such as waste remediation for the Department of Energy sites and process control for chemical and pharmaceutical manufacturing. However, existing methods based on ultrasonic attenuation can become inaccurate for highly concentrated suspensions due to careful transducer alignment and the complicated mathematics required to describe multiple scattering, which controls the attenuation. Two measurements that help to overcome these difficulties are the ultrasonic backscattering and diffuse field. Backscattering is attractive because the single scattering theories typically used to describe backscattering are mathematically simpler than attenuation theories and lend themselves to more stable inversion processes. Also, the measurements of backscattering and diffuse fields do not require long travel distances and can be made with a single transducer thus eliminating alignment problems. We will present ultrasonic measurements on solid liquid suspensions designed to elucidate the particle size and concentration at high concentrations.
Characterization of Solid Liquid Suspensions Utilizing Non-Invasive Ultrasonic Measurements
2004
Rapid, on-line determination of particle size and concentration is required for the efficient process measurement and control of many processes in government and industrial applications such as waste remediation for the Department of Energy sites and process control for chemical and pharmaceutical manufacturing. However, existing methods based on ultrasonic attenuation can become inaccurate for highly concentrated suspensions due to careful transducer alignment and the complicated mathematics required to describe multiple scattering, which controls the attenuation. Two measurements that help to overcome these difficulties are the ultrasonic backscattering and diffuse field. Backscattering is attractive because the single scattering theories typically used to describe backscattering are mathematically simpler than attenuation theories and lend themselves to more stable inversion processes. Also, the measurements of backscattering and diffuse fields do not require long travel distances and can be made with a single transducer thus eliminating alignment problems. We will present ultrasonic measurements on solid liquid suspensions designed to elucidate the particle size and concentration at high concentrations.
KONA Powder and Particle Journal, 2017
Size characterization of nanoparticles has gained wide concerns in the past decades, but it remains a challenge for measurement in suspensions up to now. The extremely small scales of particle size result in great difficulty for traditional static light scattering method and optical imaging. In addition to the electron microscopy techniques, the dynamic light scattering (DLS) method is another widely used technique for laboratory analysis of samples. Moreover, the ultrasonic attenuation spectroscopy (UAS) technique is also being developed rapidly to provide an alternative method for nanoparticle sizing. This paper focuses on the latest development in the above two technologies for nanoparticle size characterization. As for the former, advances about the image-based DLS technology in recent years are reviewed, including three different kinds of data processing methods and corresponding measuring experiments using standard polystyrene particles. Methodology principles, models and experimental setup were also reviewed for the latter UAS technology. Samples of the same nanoscale silver particles were tested by the above two methods, as well as by transmission electron microscopy. A sample of Antimony Tin Oxide (ATO) nanoparticles has also been adopted for measurements and comparisons. Relatively consistent results can be found by comparing the particle sizes or distributions with various methods. The dramatically reduced measurement time in image-based DLS indicates the potential for real-time and in-situ nanoparticle sizing. UAS also provides a suitable way for nanoparticle size characterization at high concentrations.