Influence of sulfonated acetone–formaldehyde condensation used as dispersant on low rank coal–water slurry

Highlights: ► We synthesize a series of SAF which are applied as dispersants in coal–water slurry. ► SAF have a better effect comparing with naphthalene sulfonate formaldehyde condensation. ► Appropriate molecular weight and sulfonic group content will increase the performance of slurry. ► The effect is attributed to the steric hindrance and electrostatic repulsion. - Abstract: A water-soluble aliphatic polymer, sulfonated acetone–formaldehyde (SAF) condensation, was developed by sulfonation and polycondensation reaction. To determine the optimum molecular structure of SAF dispersant for preparing the minimum viscosity of highly concentrated low-rank coal–water slurry (CWS), various SAF with different sulfonic group content and different molecular weight were prepared by controlling the quantity of sulfonating agent and the mass concentration of reaction solution. The CWS followed three-parameter Herschel–Bulkley model and behaved as a non-Newtonian fluid in the presence of SAF. Compared with naphthalene sulfonate formaldehyde condensation, SAF had a better effect in reducing the viscosity, especially for the SAF with molecular weight of 31,800–36,800 and the sulfonic group content of 3.53–3.64 mmol/g. The effectiveness of viscosity reduction for CWS had been attributed primarily to the diminution of the coal particle–particle interaction because of steric hindrance and electrostatic repulsion, which were offered by adsorbed SAF. The effect was further proved by zeta potential measurements of coal and rheological investigation of slurry in the presence of SAF.