Feedstocks have been selected (wood, wheat straw, and lignin, Work-package - WP3) and were characterized in detail. Atmospheric thermogravimetric analyses at different heating rates were conducted using the selected feedstocks and model components for the full evaluation of thermal decomposition kinetics. The kinetic parameters were successfully determined using appropriate models. The most suitable molten salt for liquefaction of biomass at low temperatures was selected, based on literature data and experiments performed in the consortium. Liquefaction of pinewood and Kraft lignin in a molten salt medium was investigated and > 90% recovery was obtained for lignin, thus fulfilling an important WP3 objective. Molecular transformations during lignin liquefaction in molten salts were determined. Molten salts viscosity measurements were initiated to assess the pumpability of the salt-lignin slurries into the subsequent hydro-pyrolysis unit.
Exploratory small scale (mg) hydro-pyrolysis experiments (WP4) on the conversion of the liquefied biomass sources (wood, straw and lignin) were successfully conducted. The (hydro-) pyrolysis of lignin in molten salts at somewhat larger scale was studied in 2 different experimental setups: a gram-scale reactor for quick experimentation at atmospheric pressure to study the effect of catalysis on the molten salt pyrolysis process and a larger-scale pressured autoclave reactor able to be used in combination with hydrogen. The 1st experimental results showed that particularly lignin has the potential to be used as a suitable feed for the concept. Salt regeneration and recycling studies have been performed. Spent molten salt samples with different feedstock residues were prepared for analyses. A number of salt recycling options have been explored and the best one (dissolution/filtration/drying) has been selected.
Hydrodeoxygenation studies (WP5) were performed on the liquids obtained from wood pyrolysis in molten salts which were shown to consist mainly of furfural, acetic acid and sugar derivatives. A 3-step sequence involving ketonization, aldol condensation and hydrodeoxygenation was tested and shown to lead to hydrocarbons within the middle distillate range in an overall carbon yield of 21%. Samples of oils produced from the pyrolysis of lignin in molten salts were successfully hydrotreated in batch and continuous set-ups. High carbon yields were obtained (up to 90%), and the products were shown to be hydrocarbons of which the majority was in the middle distillate range.
The integrated unit (WP6) to proof the concept at labscale was designed, built, commissioned and tested for extended times on stream. For lignin, an overall carbon yield of 78% was obtained at runtimes exceeding 80 h, clearly indicating the potential for further scale-up.
Detailed mass and energy balances for the different units (liquefaction, hydropyrolysis, HDO) for lignin as the feed were prepared in Aspen Plus (WP2) with input from other WPs. A detailed process design was developed and used for a techno-economic analysis as well as studies on the integration of the ABC-Salt process in a pulp mill. The optimized model predicts that the manufacturing costs of the middle distillates from lignin are about 1.8 €/kg. The LCA reveals that the GWP could be reduced below the REDII 65% limit and a 82% reduction was calculated using the optimized process design in combination with pulp mill integration.
The socio-economic acceptance of waste agricultural residue conversions to biofuels using thermochemical processes has been finalized and quantified to identify major drivers and barriers for the introduction of biofuels.
