Ultrasonic Techniques for Measurement of Coal Slurry Viscosity

摘要

This paper presents a technical evaluation of ultrasonic methods when they are applied to the measurement of slurry viscosity. The four ultrasonic techniques examined were measurement of attenuation, acoustic impedance, relaxation, and acoustic streaming and cavitation. Acoustic impedance measurements are more sensitive to slurry viscosity than to any other fluid parameter. The three other techniques measure acoustic attenuation, but in different frequency ranges. The direct attenuation measurement technique suffers from the difficulty of extracting the viscous contribution from other effects, especially the thermal effect. The relaxation method requires an operating frequency near 10 to the 9th power Hz, which is difficult to achieve at present. Finally, the streaming and cavitation method has not been carefully examined because the technique is based on nonlinear acoustic effects which are not well understood. Results from this study indicate that it is feasible to develop an on-line ultrasonic viscometer based on the measurement of either acoustic impedance or acoustic streaming and cavitation. The paper describes the design and performance of an ultrasonic shear-wave wedge for acoustic impedance measurement. The wedge consists of two interfaces; one in contact with air and the other with slurry. Thus, the wedge is self-calibrating and capable of correcting any error that is due to temperature change. 20 refs., 2 figs., 2 tabs. (ERA citation 14:014199)