In-line mixing states monitoring of suspensions using ultrasonic reflection technique

•An ultrasonic technique is proposed for in-line monitoring of the suspensions mixing states.•The effects of impeller diameter and agitation speed on the mixing process are studied.•The minimum mixing time and the optimal agitation speed are acquired.•The homogeneity of suspensions is expressed quantitatively. Based on the measurement of echo signal changes caused by different concentration distributions in the mixing process, a simple ultrasonic reflection technique is proposed for in-line monitoring of the mixing states of suspensions in an agitated tank in this study. The relation between the echo signals and the concentration of suspensions is studied, and the mixing process of suspensions is tracked by in-line measurement of ultrasonic echo signals using two ultrasonic sensors. Through the analysis of echo signals over time, the mixing states of suspensions are obtained, and the homogeneity of suspensions is quantified. With the proposed technique, the effects of impeller diameter and agitation speed on the mixing process are studied, and the optimal agitation speed and the minimum mixing time to achieve the maximum homogeneity are acquired under different operating conditions and design parameters. The proposed technique is stable and feasible and shows great potential for in-line monitoring of mixing states of suspensions.