Study on the slurry ability of low-rank coal blended with alkali-modified sludge

In this study, alkali-modified municipal sludge (AS) was mixed with low-rank coal to prepare AS-coal water slurry (ASCWS). The influence of AS on the slurrying performance of coal water slurry (CWS) was investigated, and the slurrying mechanism of municipal sludge-CWS (SCWS) was elucidated. Research on the alkali modification of municipal sludge showed that the effectiveness of the modifiers was in the order Ca(OH)(2) > NaOH > KOH > K2CO3. Considering the apparent viscosity of the slurry as the evaluation criterion, the optimal alkali modification scheme was determined through the response surface optimization test, and 19.99 % Ca(OH)(2) was suitable to modify the sludge for 14.61 h Compared with the unmodified sludge, the content of oxygen-containing functional groups on the surface of AS was reduced, and the flocculent structure was disrupted, which helped improve the slurry formation performance of the SCWS. Blending the sludge with the CWS enhanced the stability of the slurry, and the water separation rates for the SCWS and ASCWS decreased from 18.62 % to 5.00 % and 5.26 %, respectively. The mechanism study showed that the zeta potential values of SCWS and ASCWS decreased from -10.67 mV to -32.23 mV and -39.22 mV, respectively. The increased electronegativity of the slurry owing to the addition of sludge facilitated particle dispersion and enhanced slurry stability. The adsorption patterns of sodium poly[(naphthaleneformaldehyde)sulfonate] (MF) on coal, sludge, and modified sludge were consistent with the Langmuir adsorption model. The pseudo-second-order kinetic model accurately described the adsorption process of MF on coal, sludge, and modified sludge.