Effects of Hydrothermally Pretreated Sewage Sludge on the Stability and Dispersibilty of Slurry Fuel Using Pulverized Coal

Abstract

Some research has been carried out on the disposal of sewage sludge by gasification technology. Most of it was based on separate grinding and drying processes for pretreatment, since raw-sewage sludge contains considerable amounts of water and has extremely broad particle size distribution. In the present study, sewage sludge was hydrothermally pretreated—rather than being energy-intensively dried and ground—for CSWS (coal–sludge–water slurry) preparation, which was assessed for suitability as a fluid fuel. Its apparent viscosity and solid concentration were compared with those of CWS (coal–water slurry). Sewage sludge enhanced coal slurry rheological properties, such as stability and dispersibility. The viscosity and solid content of CSWS remained constant in CSWS samples after 72 h stability testing, whereas those of CWS respectively decreased by ca. 1000 cP and 3.3%. Furthermore, there were no differences in particle size distribution and FT-IR spectra of the CSWSs between its top and bottom layers aft...