Pyrolysis, combustion and gasification characteristics of miscanthus and sewage sludge

Highlights: • Pyrolysis, combustion and gasification characteristics of miscanthus and sewage sludge. • We evaluate the temperature range for different process. • Product gas compositions during gasification at different temperature ranges. • Appropriate temperature range assessed for gasification with efficient carbon conversion. • Kinetic constant estimation using Friedman and Coats and Redfern method. - Abstract: The energetic conversion of biomass into syngas is considered as reliable energy source. In this context, biomass (miscanthus) and sewage sludge have been investigated. A simultaneous thermal analyzer and mass spectrometer was used for the characterization of samples and identified the volatiles evolved during the heating of the sample up to 1100 °C under combustion and gasification conditions. The TG and DTA results were discussed in argon, oxygen, steam and steam blended gas atmospheres. Different stages of pyrolysis, combustion and gasification of the samples have been examined. It was shown that the combustion and gasification of char were occurred in two different temperature zones. The DTA–MS profile of the sample gives information on combustion and gasification process of the samples (ignition, peak combustion and burnout temperatures) and gases released (H₂, O₂, CO and CO₂). The results showed that the different processes were mainly dependent on temperature. The evolution of the gas species was consistent with the weight loss of the samples during pyrolysis, combustion and gasification process. The effect of the ambiences during pyrolysis, combustion and gasification of the samples were reported. The appropriate temperature range to the sludge and miscanthus gasification was evaluated. The kinetic parameters of the biomass and sewage sludge were estimated for TGA using two models based on first-order reactions with distributed activation energies. The presence of ash in the biomass char was more influential during the gasification process