Torrefaction is a promising biomass upgrading method, offering advantages in logistics and handling. Gasification is an attractive thermochemical conversion technology due to its flexibility in the product gas end-use. The aim of this paper is to investigate the impact of torrefaction on the gasification performance of a softwood (spruce) and a hardwood (ash). Spruce and ash were torrefied at 260 and 280 °C, and at 250 and 265 °C, respectively, and pelletized. All feedstocks were gasified at 850 °C and atmospheric pressure under oxygen-steam circulating fluidized bed gasification conditions, with magnesite as bed material and with an equivalence ratio (ER) of 0.3 and a steam-to-biomass mass ratio (SBR) of 1.0. Only the torrefied feedstocks were gasified varying ER and SBR values. The results show that torrefaction affected the gasification performance of both feedstocks leading to decreasing the cold gas and carbon conversion efficiencies. For spruce, torrefaction did not affect the permanent gas composition but led to a decrease of the total tar content for both spruce 260 and spruce 280. For ash, torrefaction resulted in decreasing the CH₄ volume fraction, and increasing the H₂ volume fraction and the total tar content for both torrefaction temperatures. Varying the ER and SBR affected only the Class 3 tars of ash 250. Conclusively, torrefaction of spruce and ash did not offer substantial benefits on the gasification performance under the investigated conditions. It is suggested that research of torrefied wood gasification includes feedstock's chemical analysis and characterization of products obtained under fast devolatilization conditions.

Torrefaction is a promising biomass upgrading technology as it makes biomass more coal alike and offers benefits in logistics and handling operations. Gasification is an attractive thermochemical conversion technology due to its flexibility in the product gas end-uses. Therefore, it is valuable to investigate whether additional benefits are foreseen when torrefaction is coupled with gasification. Therefore, two commercial torrefied wood fuels and their parent materials are gasified at 800–850 °C under atmospheric steam-oxygen circulating fluidized bed gasification conditions and magnesite as bed material. The torrefied feedstocks consisted of wood residues torrefied by Topell at 250 °C (Topell black), and mixed wood and wood residues torrefied by Torrcoal at 300 °C (Torrcoal black). The gasification results show that torrefaction resulted in an increased gas quality, as it yielded higher H₂ and CO contents, a decrease of the CO₂ content, increased gas yield and a significant decrease of the total tar content for both feedstocks. For the Torrcoal samples, torrefaction resulted in a decrease in the carbon conversion efficiency (CCE). In addition, the cold gas efficiency (CGE) remained approximately the same due to the increase in the H₂ and CO contents. The Topell samples showed an increase in the CCE and CGE upon torrefaction, but this could be attributed to a significant grinding in the screw feeder. It is generally concluded that both torrefied fuels may offer benefits as a feedstock for steam-oxygen blown circulating fluidized bed gasification, in particular in terms of gas quality and yield.

There are various attempts to industrialize the supercritical water gasification (SCWG) of wet biomass process, however, there are still process challenges to overcome. Such challenges include slurry pumpability, energy efficiency, low conversion, char and tar formation, and clogging problems due to salt precipitation. Fortunately, some of the aforementioned challenges can be eliminated by having long residence times, high heating rates and utilization of fluidized bed reactors. This study presents the first results and experiences obtained from the TU Delft/Gensos semi-pilot scale setup which has a capacity of 50 kg/h and incorporates a fluidized bed reactor. A dry starch concentration of 4.4 wt % was used as feedstock. Reactor temperatures of 500 °C, 550 °C and 600 °C, and the mass flow rates of 24.5 kg/h and 35 kg/h were tested. The results indicate that the heating profile in the heat exchanger and the residence time at higher temperatures (>500 °C) play a significant role in the conversion efficiencies. No clogging problem was observed, however small quantities of char (2.3 wt % at highest) and oil production (10.4 wt % at highest) were observed. The highest carbon gasification efficiency was 73.9% and this was obtained at a reactor temperature of 600 °C and at a feed flow rate of 24.5 kg/h.