Performance and mechanism of polyacrylamide stabilizers in coal water slurry

The stability of coal water slurry (CWS) is a significant factor affecting its storage and transportation. However, the understanding of the mechanism of high-molecular-weight polymer used as stabilizers in CWS is still limited. We experimentally studied the rheological behaviors and stability performance of coal water slurry prepared with anionic (APAM), cationic (CPAM) and nonionic (NPAM) polyacrylamide. Apparent viscosity and rheology were measured using a viscometer. The rod penetration method incorporating with the oscillation method was applied to evaluate the stability performance of CWS. The zeta potential measurement and interaction energy calculations were also conducted. The results showed that the apparent viscosity of CWS increased with the addition of all the three PAMs. CWS by adding either APAM or CPAM behaved as a pseudoplastic fluid while the CWS with the addition of NPAM behaved as a dilatant fluid. The CWS with 0.1 wt% (on the dry coal basis) APAM exhibited the best stability performance. The settling rate for this slurry was the lowest (6.67%), and the zeta potential was the highest (-22.33 mV). The CWS by adding APAM had the highest total interaction energy between coal particles among four samples. The mechanism that controls the stability of CWS may be relevant to the increased electrostatic repulsive energy between coal particles by adding APAM, which depends on the surface potential of coal particles.