Partial oxidation of municipal sludge in supercritical water

For harmless disposal and resource utilization, the partial oxidation characteristic of municipal sludge in supercritical water was studied in a batch reactor. The results show that with an increase of oxidant coefficient by 0.2, the mole fraction of H₂ decreases by 3.1%-6.1%; increasing the temperature by 20 K, the mole fraction of H₂ increases by 2.0% or extending the reaction time by 10 min and the mole fraction of H₂ increases by 1.5%-1.7%, which gets its maximum when the reaction time is 30 min. The reaction temperature and time are significant for the removal rate of COD. Furthermore, the addition of activated carbon as the catalyst can cause an increase in the mole fraction of H₂ by 14.5%-16.1%. A global power-law rate expression was regressed from the experimental data at 25 MPa. When mass fraction 1% activated carbon was used as the catalyst, the resulting pre-exponential factor was 6 347.7, the activation energy was 105.698 kJ/mol, and the reaction order for oily sludge (based on COD) was 2.023. When no catalyst was applied, the three values were 4 403.3, 113.054 kJ/mol and 2.023, respectively. Consequently, the activated carbon can promote the water-gas shift reaction and increase the mole fractions of H₂, but is insignificant for the removal rate of COD.