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Advanced Biomass Catalytic Conversion to Middle Distillates in Molten Salts

Periodic Reporting for period 3 - ABC-SALT (Advanced Biomass Catalytic Conversion to Middle Distillates in Molten Salts)

Período documentado: 2020-10-01 hasta 2022-09-30

The introduction of sustainable biofuels for the transportation sector is a major ambition of the EU to reduce CO2 emissions. The ABC-Salt (Advanced Biomass Catalytic Conversion to Middle Distillates in Molten Salts) project aims to provide an innovative cost-effective technical solution for the production of sustainable biofuels in the middle distillate range. Lignocellulosic waste streams (including forestry residues, straw and lignins from the paper and pulp industries) will be converted through an advanced thermochemical conversion process involving biomass liquefaction, catalytic hydro-pyrolysis of the biomass in a molten salt environment, followed by the catalytic hydro-deoxygenation of the vapour phase. An overall yield of 35 %, with more than 2/3 in the middle distillate range is targeted for (all based on dry biomass input). The groundbreaking step beyond the state of the art is the use of molten salts to solubilize and hydro-pyrolyse the lignocellulosic waste streams. With this approach, higher middle distillates yields are anticipated compared to existing processes. ABC-Salt aims to provide the proof of concept for this advanced technology at a TRL of 4 by operating an integrated lab scale reactor over extended runtimes at a minimum scale of 100 g/h input. In addition, the techno-economic viability of the technology (substrates availability and supply chain, future end-users and economic sustainability of the process) will be assessed. Moreover, studies in the social domain will be conducted including investigations of the possible barriers for social acceptance of sustainable biofuels in general and the middle distillates derived from the ABC-SALT process in particular.
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.
ABC‐Salt is an ambitious and challenging project and comprises an innovative route to sustainable middle distillates from biomass. Biomass derived fuels have been obtained using the concept from several lignocellulosic waste streams including lignin-rich ones. The use of such waste streams, which are abundantly available at low prices, will help to overcome any feedstock limitations while keeping short supply chains.
The groundbreaking step beyond the state of the art is the use of a biomass source in combination with molten salts, which leads to higher hydrocarbon yields than existing processes, while combining all beneficial aspects of existing technologies. The integrated concept has been demonstrated successfully at lab scale in a dedicated bench scale unit which will be the prototype for a future fuel production system in an industrial environment, moving the technology to higher TRL (> 4).
The project will create and expand the knowledge on fundamental aspects of biomass conversion to transportation fuels. Biomass is known to behave intrinsically different than fossil resources, which are at the moment the feeds for transportation fuels. It will allow Europe to produce cost‐effective biofuels and will provide new dynamics in biofuel production technology with higher efficiency levels and lower production costs than current 2G biofuels have been demonstrated. Besides economic benefits, environmental and social benefits are foreseen. These include the use of biomass waste streams, which perfectly fits in the circularity principle and job creation by further development of the technology.
The scientific knowledge generated by ABC-Salt will allow key stakeholders in the biofuels arena (policy makers, regulatory authorities, industry, interest groups representing civil society) to frame strategic choices concerning future energy technologies and to integrate them in the current and future energy systems.
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A5 ABC-Salt leaflet