Coal water slurry using dispersant synthesized from cashew nut shell liquid (CNSL)

•Cardanol-formaldehyde sulfonate as dispersant was synthesized from cardanol.•There is no effect of using dispersant in CWS on the combustion behavior.•The properties are defined in the specification as compared to sodium lignosulfonate.•Natural based dispersant would be an optional choice for CWS application.

The present work reports the preparation of coal–water slurry (CWS) containing cardanol–formaldehyde sulfonate (CFS) which was synthesized by sulfomethylation reaction of cardanol. It is found that the surface tension of CFS decreases with increasing concentration, indicating its good surface activity. Further, CWS (at 50 wt.% coal) containing CFS in the concentration range of 1.0–1.8 wt.% exhibits a marked decrease of viscosity which is similar to that of CWS containing sodium lignosulfonate (SL). In addition, the stability of CWS containing CFS of 1.0 wt.% gives below 50% of penetration ratio for a period of as long as 1 month whereas less than 30% for CWS without dispersant. As a result, it demonstrates that CWS containing CFS of 1.0 wt.% exhibits the properties within the specification similar to that of SL.