• Energy Research

Abstract Fischer-Tropsch based fuels from renewable electricity and carbon dioxide provide one possibility to defossilise the transport sector, especially where long distances and high loads require fuels with high energy density. In this work, a stationary Power-to-Liquid (PtL) process model is set up in Aspen Plus®. The process involves CO2 absorption, water electrolysis, CO2 activation by reverse water-gas shift reaction (rWGS), an oxyfuel burner, Fischer-Tropsch synthesis, product separation and hydrocracking. The influence of the rWGS operating conditions (pressure and temperature) on the overall process performance in terms of PtL-efficiency and hydrogen/carbon efficiency is investigated. The operating conditions are varied between 550 and 950 °C and 1–25 bar. The temperature and pressure dependent methane formation in the rWGS is found to have major influence on the efficiencies. For the base case, a maximum Power-to-Liquid efficiency of ηPtL = 38.7 % is obtained at 5 bar and 825 °C, while a maximum hydrogen efficiency of ηH = 28 % results at 1 bar and 725 °C. The carbon efficiency is found to be constant (ηC = 88 %). Sensitivity studies show that the optimum operating conditions are not affected significantly by variation of the investigated process variables.

Abstract To achieve the emission mitigation and decarbonization goals, future aviation requires alternative sustainable fuels. Synthetic paraffinic kerosene, generated by Fischer-Tropsch synthesis, is certified as a drop-in jet fuel up to 50%. Potential fuel production routes are via conversion of biomass (Biomass-to-Liquid, BtL), the combination of renewable power and biomass (Power-and-Biomass-to-Liquid, PBtL) and the conversion of carbon dioxide with hydrogen from renewable power (Power-to-Liquid, PtL). In order to compare the three different production routes, an Aspen Plus ® model is designed for each production path and techno-economically assessed for an assumed capacity of 11 Mg h −1 fuel production (equals 90 Gg·a −1 plant capacity). Even though the BtL route allows the lowest net production costs, it has some drawbacks compared to PBtL and PtL. Especially the low H to C ratio of biomass leads to limited fuel yields in the BtL process. These yields can be increased by a factor of about 3 when conducting the PBtL process with the same biomass input instead of BtL. The highest X-to-Liquid efficiency based on power input and energy in feedstock is found for PBtL (51.4%) followed by PtL (50.6%) and BtL (36.3%). For BtL 73% of the introduced carbon is lost as CO 2 . The total investment costs are highest for BtL, followed by PBtL and PtL. The net production costs are in the reverse order. The cost analysis reveals total PBtL investment costs of 742 M€ and net production costs of around 3 €·kg −1 with an electricity price of 105 €·MWh −1 . The costs for electrolyzer and gasifier represent the largest shares of the total capital costs. As the net production costs are dominated for the electricity costs, low electricity prices and high capacities are advantageous for PBtL, while high electricity and low biomass costs favor BtL concept.

European Union (EU) energy markets are changing rapidly. After the recent turmoil, a new wave of EU legislation is once again reshaping the way energy should be used in the EU, emphasizing not only the increasing importance of using renewable and local energy sources but also highlighting the importance of energy efficiency and decarbonization of high to abate sectors (including aviation and marine fuels). Heating and cooling account for about half of the total gross final energy consumption in the EU. This article explores the novel concept of using waste heat from the flexible Fischer–Tropsch (FT) process (FLEXCHX) in the existing district heating network, resulting in tri-generation: FT C5+ liquids, heat, and electricity. FLEXCHX provides operation flexibility and combines advanced biomass gasification, catalytic liquefaction, electrolysis, and waste heat recovery, allowing use of biomass residues in a more sustainable way. Our results, based on the Kaunas district heating (DH) system, show that this process could be integrated into the existing district heating network in Northern Europe and successfully compete with existing heat-only boilers and CHPs using biomass or municipal waste, resulting in more efficient use of biomass and savings accumulated up to EUR 200 million over the study period in the analysis (2020–2050), supplying up to 30% of the heat in the Kaunas DH system. Enriching the FT process with hydrogen (using electrolysis) could result in additional FLEXCHX utilization benefits by creating demand for cheap excess electricity that might otherwise be curtailed.

Biofuels for future sustainable aviation are far from sufficiently available and affordable. The techno-economic and environmental assessment can show the bottlenecks and opportunities towards large scale deployment and cost reduction opportunities. The assessment methodology was standardized and automated in a software-tool TEPET to allow transparent support for investment decision and policy-making. The methodology is explained with case study examples. E.g., it is shown how standardized techno-economic and environmental assessment can help to identify optimal plant locations or to roughly estimate biofuels potential across Europe. Proceedings of the 31st European Biomass Conference and Exhibition, 5-8 June 2023, Bologna, Italy, pp. 1137-1144