Gas Bubble Effects and Elimination in Ultrasonic Measurement of Particle Concentrations in Solid-Liquid Mixing Processes

In this paper, the online measurement of particle concentrations in suspensions containing gas bubbles is studied using the ultrasonic spectra and the synergy interval partial least squares regression (Si-PLS) model in the solid-liquid mixing processes. At first, a comparison is made among the ultrasonic signals obtained from suspensions and pure water with and without gas bubbles and the gas bubble effects of high agitation speeds on ultrasonic measurement are evaluated. A moving average and standard deviation method is developed to deal with the real-time ultrasonic signals, aiming to decrease the fluctuations and noises of signals and improve the stability of signals. Then, based on the optimal spectral subintervals selected with the Si-PLS model, the prediction model for the particle concentrations is built, which considers the gas bubble effects as an interferent. The optimal model, of which the root-mean-square error of the prediction subset is 0.38 wt%, is successfully applied to measure the concentration of TiO2 suspensions in the range of 0-15.79 wt% when the agitation speed is less than 1200 r/min. The online measurement results suggest that the proposed method has the potential to be a useful tool for eliminating gas bubble effects and measuring particle concentrations in the solid-liquid mixing processes.