Abstract
To determine the optimum combination of operating parameters for direct thermochemical liquefaction of sewage sludge, dewatered materials (raw mixed sludges) were treated over a temperature range of 150–300°C, a holding time of 0–180 min and a catalyst (sodium carbonate) loading of 0–5 wt% using a batch reactor. By variance analysis, the lower limit of reaction temperature for the production of heavy oils was found to be 250°C. At that temperature, however, organic concentrations in the aqueous phase were still high. From the viewpoint of oil production and wastewater treatment, the optimum combination of operating parameters was a reaction temperature of 275–300°C, a holding time of 60 min and operation without catalyst.
