Extraction of characteristic parameters of coal slime flocs and its dynamic change

Abstract

A fully-automated image processing script based on clarity value of floc was developed to solve the existing problems of fuzzy coal slime flocs difficulties in accurate identification.In the procedure, out-of-focus flocs were automatically removed to attain more precise floc characteristic parameters.The resulting measured and the characteristic parameters were compared to floc measured through compare with manual processing method using image processing software and conventional threshold segmentation method, the automated method was able to accurately measure the floc characteristic parameters quickly by correctly sizing in-focus flocs and removing out-of-focus flocs.The dynamic changes of characteristic parameters of slime floc were studied at different stirring speeds and different dosage of flocculants by applying the fully-automated image processing script during flocculation process.The results showed that, the process of slime water could be divided into three stages:rapid growth stage, crushing stage and equilibrium stage, and the larger the stirring speed, the shorter the floc growth stage and the smaller the mean value of floc equivalent diameter;The two-dimensional fractal dimension was found ranging from (2.17±0.03) to (1.89±0.01), corresponding to flocs that were either relatively compact or loosely structured, at high(217 r/min) and low (152 r/min) stirring speed respectively with the flocculants dosage of 3 mg/L;The equivalent diameter of coal slime floc reached the maximum at the flocculants dosage of 4 mg/L, and the two-dimensional fractal dimension was found increasing from (1.81+0.01) to (2.01+0.03) with the increasing dosage of flocculants at the 152 r/min stirring speed.

Keywords

• coal slime
• flocculation
• fractal dimension