Influence of temperature in the thermo-chemical decomposition of below-stoichiometric RDF char - a macro TGA study

Due to the energy crisis that some countries are facing nowadays, the gasification process appears to be a good alternative to produce some energy from solid materials. Increasingly, gasification involves using wastes as a solid fuel, making the process green and reusing some materials that otherwise could end up in a landfill. However, the process of finding the best gasification parameters of a sample can be very expensive and time-consuming. In this sense, a refuse-derived fuel (RDF) char produced from an original RDF under 30 min at 400 °C was tested on a small-scale reactor using macro thermogravimetric analysis (TGA), as presented in this paper. The goal was to study and evaluate the devolatilization and residual carbon rate of the sample under several conditions and, at the same time, quantify and analyze the released gas. In the first round of tests, 5, 10, and 20 g of samples were tested at 750 °C with an excess of air coefficient (λ) = 0 and 0.2. It was possible to conclude that the lower the mass, the higher the devolatilization rate. The λ only had an influence on the devolatilization rate with a 20 g sample. Regarding the gas, CO, CO2, and H2 had no variation in the sample mass in contrast to CH4, which increased with the increase in the sample mass. The second round of tests was performed with samples of 10 g of mass at temperatures of 700, 800, and 900 °C and λ values of 0.15, 0.2, and 0.25. The tests indicated that the temperature influenced the devolatilization rate but not the residual carbon combustion rate. Regarding the gas composition, CH4, CO2, and CO followed the same trend, decreasing the concentration with the increase in temperature; in contrast, H2 increased in concentration with an increase in temperature. The heating value of the gas followed the same behavior as CH4. This work was co-financed by Compete 2020, Portugal 2020, and the European Union through the European Regional Development Fund—FEDER within the scope of the project AmbWTE: Biomass & Waste to Energy System project, project scope: POCI-01-0247-FEDER-039838. This work was supported by FCT within the Projects Scope, UIDB/04077/2020 (METRICS Center).