Freezing front velocity estimation using image processing techniques

Freeze concentration is a promising water purification technology due to its low energy consumption when compared with traditional procedures such as evaporation. Crystal growth velocity is an important parameter for the design and control of this process. If crystal growth surpasses certain speed, known as limit velocity, the separation process will not be successful. In this work two different motion detection image analysis strategies were used as non invasive techniques to follow the crystal growth velocity in a unidirectional crystallizer. The first technique is based on matching primitives detected on the image and the second one on optical flow algorithms. A mid-level processing algorithm has been used to identify the freezing front position. It segments the images using thresholding limits based on CIELAB color space parameters L*,a*,b*. Both methods were successfully used to estimate limit ice front velocity. Furthermore, the effect of initial solid concentration on limit ice front velocity has been modelled by an equation of the form Vl=K1C0 -k2. © 2019 Elsevier Ltd.