Torrefaction of a solid recovered fuel (SRF) to improve the fuel properties for gasification processes

Highlights: •The torrefaction of a waste-derived fuel for gasification purposes was performed. •Gasification of two torrefied samples with different gasification agents and bed materials was studied. •Gasification parameters and energy efficiency of the process are evaluated. •Torrefied samples released lower levels of tar and HCl in the syngas than the parent fuel. •Cost evaluation advised the use of torrefaction only for some gasification conditions. -- Abstract: This work studies the torrefaction of a solid recovered fuel (SRF) and its effect on the fuel properties for gasification. The SRF (namely FL) was torrefied at two temperatures (290 °C and 320 °C) in a pilot auger reactor (capacity of up to 100 kg/h) and evaluated as a gasification feedstock. This evaluation included the characterization of the obtained torrefied materials (FL290 and FL320) and several gasification tests in a bench-scale fluidized bed reactor. These tests were performed with different gasification agents (air and oxygen/steam) and bed materials (sand, dolomite and olivine) at similar experimental conditions (T = 850 °C and ER ∼ 0.3). The evaluation of the gasification performance was presented in terms of product yields and gas composition together with the release of contaminants. Tar species (polycyclic aromatic hydrocarbons) and minor contaminants (H₂S, HCl, HCN and NH₃) were analysed by gas chromatography and ion-selective potentiometry, respectively. Additionally, the calculation of the process efficiency (gasification and its combination with torrefaction) based on the energy content of the producer gas and a preliminary cost analysis that evaluate the main benefits and drawbacks of the torrefaction process are included. The results indicated that the torrefaction process improved the SRF gasification parameters (lower tar, higher H₂/CO ratio, carbon conversion, etc.) and strongly affected the presence of HCl in the producer gas. However, the preliminary cost analysis advised the combination of both technologies only under certain gasification conditions.