Influence of sewage sludge on the slurryability of coal–water slurry

In this study, the maximum solids loading, stability and rheological properties of coal–sludge slurries were investigated and compared with those of coal–water slurries. The maximum solids content of coal–sludge slurry was much lower than that of coal–water slurry because of the ∼82% water in sewage sludge. NaOH addition as a pre-treatment of sewage sludge improved the maximum solids content to 61% and 60% for dispersants A1 and A2, respectively, for a sludge–coal mass ratio of 22.1:100. Compared to coal–water slurries, the stability of coal–sludge slurries was better, with no solid deposition after 96 h. Coal particles and sewage sludge formed a stable medium and settlement of large coal particles was prevented. All the coal–sludge slurries exhibited pseudo-plastic behavior; this type of fluid is shear-thinning and is easy to transport.