Optimization of parameters affecting the hydrothermal carbonization of wastewater treatment plant sewage sludge

The optimization of hydrothermal carbonization for sewage sludge (SS) was conducted in this study. The impact of three independent variables, namely biomass:water ratio (B/W) (10-30%), retention time (15-45 min), and temperature (150-250 degrees C), on hydrochar (HC) yield, higher heating value (HHV), and energy yield of SS was explored. Characterizations of SS and HCs were obtained by ultimate and proximate analysis, FTIR, SEM, and bomb calorimetry. Using Box-Behnken Design as a standard response surface methodology technique, a quadratic model was suggested to correlate the independent parameters for the effect of parameters on HC yield, HHV, and energy yield and also was used for finding the maximal thesis effective parameters at the optimal process condition. In the research, B/W, retention time, and temperature, respectively, were determined to be optimum for HC energy yield at 8.9 wt.%, 33.4 min, and 205.7 degrees C. The highest possible energy output was 82.5%.