The effects of water quality on the filtration performance of coal flotation product

• The slurry pH and concentrations of salts and flocculant impact flowrate. • The cake moisture is mainly affected by flocculant and salt concentration. • Changes in filtration performance is governed by the cake pore structure. • Pore structure changes alter cake resistance and water adsorption area. Low-quality water is frequently used in coal preparation plants to conserve freshwater resources and lower operational costs. In the present work, a series of laboratory filtration experiments and subsequent μ CT imaging of the filter cakes were conducted to link the effect of water quality on filtration performance and cake structure. Filtration experiments were carried out with three selected variables, including the slurry pH, salt concentration, which are the most important parameters of water quality, and the flocculant dosage. Filtration flowrate and cake moisture, the two most critical parameters, while examining filtration performance, were evaluated based on the filtration results. The slurry pH, salt concentration, and flocculant dosage were all found to significantly impact the flowrate, while the cake moisture was mainly affected by flocculant and salt concentration. These observed interactions were correlated with the results from filter cake µ CT imaging. An increase in either salt concentration or the flocculant dosage was observed, which can cause a change in the pore structure of the cake, altering porosity, pore size, and specific surface area within the cake. Such changes in the pore structure resulted in changes in the specific cake resistance and the available water adsorption area, ultimately leading to changes in flowrate and moisture retention.