Pyrolysis and Co-Combustion of Semi-Dry Sewage Sludge and Bituminous Coal: Kinetics and Combustion Characteristics

To reduce the energy consumption and cost of the drying of sewage sludge (SS) and to ensure stability during combustion, the pyrolysis and co-combustion characteristics of semi-dry SS after the dehydration of flocculant and bituminous coal (BC) were studied in this work. The results show that the decrease in moisture content accelerates the release of volatile substances, and the increase in heating rate can also enhance the release of water and volatile matters. Furthermore, in the co-combustion of semi-dry SS and BC, the increase in mixing ratio (from 0% to 60%) of semi-dry SS caused the ignition and burnout temperature to decrease from 481 °C to 214 °C and from 702 °C to 627 °C, respectively. During co-combustion, the infrared spectra showed that the temperature range of 300–700 °C was the main gas precipitation area, and the main gaseous products were CO2, NOx, SO2, and volatile organic pollutants (VOCs).