Effect of addition of surface active agent on the viscosity of a high concentration slurry of a low-rank British coal in water

Coal-water mixtures (CWM) are concentrated suspensions of coal particles in water. The rheological properties of CWM depend on a number of factors suc h as the type of coal, the solid content and its size distribution, the tem perature, the pH and the presence of electrolytes and chemical additives. T he slurry viscosity was influenced significantly by initial surfactant load ing, the particle size distribution and the ash content of the feeds. CWS o f up to 60% prepared from Bickershaw coal samples with low ash contents (4. 0% and 6.86%) could be produced at acceptable viscosities in the presence o f a non-ionic surfactant, Triton X-405. To produce pumpable slurries with m ore than 60% solid, it will be necessary first to achieve a significant lev el of demineralisation, and to use high levels of reagent addition. The vis cosities of the slurries with low ash content were significantly reduced by the surfactant addition which also altered the rheological characters of t hese slurries from non-Newtonian towards Newtonian fluids. However, sample containing very fine particles with a high ash content (24.5%) showed non-N ewtonian behaviour even in the presence of reagent. (C) 2000 Published by E lsevier Science B.V. All rights reserved.