Prediction of Chemical Composition of Gas Combustion Products from Thermal Waste Conversion

Abstract

The current global energy crisis is driving the need to search for alternative raw materials and fuels that will be able to ensure the continuity of strategic industries, such as the steel industry. A chance to reduce the consumption of traditional fuels (e.g., natural gas) is to utilise the potential of gases from the thermal conversion of waste, and, in particular, pyrolysis gas. Unfortunately, despite its high calorific value, this gas is not always suitable for direct, energy-related use. The limitation is the type of waste subjected to pyrolysis, particularly plastics, rubber and textiles. Due to the above, this article proposes the co-combustion of pyrolysis gas in a ratio of 1:10 with natural gas in a pusher reheating furnace employed to heat the charge before forming. The chemical composition of flue gases generated during the combustion of natural gas alone and co-combustion with pyrolysis gas from various wastes was modelled, namely, two types of refuse-derived fuel (RDF) waste, a mixture of pine chips with polypropylene and a mixture of alder chips with polypropylene. The calculations were performed using Ansys Chemkin-Pro software (ver. 2021 R1). The performed computer simulations showed that the addition of pyrolysis gas for most of the analysed variants did not significantly affect the chemical composition of the flue gases. For the gases from the pyrolysis of biomass waste with the addition of polypropylene (PP), higher concentrations of CO and H2 and unburned hydrocarbons were observed than for the other mixtures. The reason for the observed differences was explained by conducting a formation path analysis and a sensitivity analysis for the selected combustion products.