Title : Advancing waste-to-fuel technologies: Integrated research on DFB gasification, fischer-tropsch synthesis and process monitoring
Abstract:
The production of advanced biofuels and green chemicals via advanced dual fluidized bed (a DFB) gasification combined with Fischer–Tropsch (FT) synthesis represents a promising pathway to defossilize hard-to-abate sectors such as aviation or heavy transport. These technologies enable the conversion of low-quality waste material into high-value products. At the “Syngas Platform Vienna” a plethora of feedstocks (e.g. wood chips, sewage sludge, plastic waste fractions) are converted to sustainable fuels and chemicals in a fully integrated demonstration-scale process chain. It consists of a 1 MW a DFB gasifier, coarse and fine gas cleaning units and a 250 kW FT pilot plant capable of producing 1-barrel synthetic crude per day. An industrial Cobalt-based catalyst is used for the production of higher-molecular-weight hydrocarbons such as diesel and wax fractions in a slurry bubble column reactor (SBCR).
Recent research at the “Syngas Platform Vienna” aims to optimise Fischer–Tropsch (FT) synthesis processes based on non-fossil feedstocks. This work focuses on three key aspects to enhance the performance and robustness of this waste-to-fuel conversion pathway:
- Heat transfer in the reactor
- Influence of feedstocks and impurities
- KPI estimation for advanced process control
The first point involves investigating the hydrodynamic behaviour within SBCR reactors, as this has a strong impact on mass and heat transfer within the reactor. To this end, a cold flow reactor model was developed and the impact of different gas distributors was assessed to identify suitable ones.
Regarding the second point, fuel-derived impurities can significantly affect the utilisation of synthesis gas in downstream conversion processes. In particular, sulphur-containing compounds are known to poison the catalysts used in FT synthesis, leading to reduced activity and stability. Consequently, the presence of such contaminants requires careful monitoring and efficient gas cleaning strategies. In addition to catalyst deactivation, experimental observations have shown that impurities in the synthesis gas can also influence the product distribution, resulting in noticeable changes in the composition of the produced hydrocarbons.
Thirdly, for industrial applications of this technology, possibilities to assess the performance of the plant in real time are necessary and were developed. Online process monitoring of the FT synthesis is essential to control the desired product composition since the typical FT syncrude consists of long-chain hydrocarbons (waxes) as well as middle distillate used as a drop-in fuel and naphtha. However, offline analysis of liquid products via conventional Gas Chromatography is slow and requires staff effort. Evaluation of the gas compositions at the inlet and outlet of the FT reactor as well as the liquid levels in the downstream condensers are most promising to estimate the product composition and were evaluated in experimental campaigns.
