Effects of Modified Sodium Lignosulfonate on Rheological Properties of Coal-Water Slurry with Low-Rank Coal

Coal-water slurry (CWS) is a new type of oil-replaceable liquid fuel with low pollution. The cost of CWS preparation will be greatly reduced if low-rank coal is used as the preparation material. In this work, chemical modification was used to prepare the modified sodium lignosulfonate (SL-M) hyper-dispersant, having larger molecular weight and more sulfonic groups than sodium lignosulfonate (SL), which was widely used for preparation of CWS from low-rank Shenhua coal due to its rich source and lower price. Effects of preparation conditions and molecular structure of SL-M on rheological properties of CWS were studied by using Haak rheometer. Results showed that the CWS transfered from viscous fluid to swelling fluid when the coal particle size decreased. The consistency coefficient of CWS decreased with the increase of additive dosage. The rheological properties of CWS became much better with the addition of the stabilizer, sodium carboxymethyl cellulose (CMC), compared with that of CWS without CMC. The prepared CWS changed from yield viscous fluid into yield swelling fluid with the increase of the molecular weight of SL-M. The rheological index was lower than 1 when the sulfonic group content was low, then it was increased with the increase of the sulfonic group content.