Mechanism and Performance of Composite Phase Change
Materials from the Direct Hydrolysis Residue of Municipal Sludge Loaded
with Sodium Acetate Trihydrate
The direct hydrolysis
of municipal sludge for the production of
oil and gas has become a key research focus, despite the application
of hydrolysis residues presenting a challenge. In this study, municipal
sludge was directly hydrolyzed in a high-pressure reaction kettle
and the hydrolysis residue byproduct was used as a carrier to prepare
a composite phase change heat storage material (CPCM), utilizing vacuum
impregnation for sodium acetate trihydrate (SAT) loading. The results
of Brunauer–Emmett–Teller (BET) and particle size analyses
showed that the residue obtained by the hydrolysis of sludge and sawdust
with a dry basis ratio of 4:1 had a higher pore volume and a uniform
particle size. The adsorption capacity of the hydrolysis residue to
SAT reached 600 wt %; the phase change temperature of the CPCM was
56.9 °C, and its latent heat reached 217.9 kJ/kg. The CPCM remained
stable during 150 cycles of the melting–solidification process
in a water bath and maintained excellent phase change characteristics.
The hydrolysis residue can effectively improve the undercooling and
phase separation of SAT without other additives.