Influence and mechanism of alkali-modified sludge on coal water slurry properties

Municipal sludge (MS) is used to prepare coal water slurry (CWS). This practice is beneficial for resource utilization and reduces treatment costs and environmental pollution. In this study, alkali-modified municipal sludge (AMS) was prepared with Ca(OH)₂ as modifier and mixed with coal to produce AMS-CWS. The effect and mechanism of MS and AMS on slurry ability, stability, and combustion characteristics of the CWS were explored. The results of the pulping experiments showed that the slurry concentration of the AMS-CWS was approximately 10% greater than that of MS-CWS. The water separation rates of MS-CWS and AMS-CWS were 5% and 5.26%, respectively, which were 13.62% and 13.36% less than that of CWS (18.62%). The zeta potential experiments verified these results. Combustion performance research shows that both MS and AMS have positive effects on combustion performance. The results of the contact angle experiments showed that the hydrophobicity of AMS was enhanced, which was beneficial for improving the pulping capacity of MS-CWS.