• Energy Research

Particulate-containing gas derived from fluidized-bed biomass gasification can be efficiently purified from tars and ammonia by using a nickel monolith catalyst. Catalyst deactivation by H2S and carbon deposition can be avoided at 20 bar pressure by using temperatures over 900°C. Catalyst deactivation was not observed in a long-term test that lasted 500 h. According to a techno-economical evaluation catalytic hot gas cleaning is economically equal to ammonia removal by SCR in an 60 MWe IGCC plant.

Steam-oxygen gasification in a Circulating Fluidized-bed (CFB) reactor was developed for producing transportation fuels from different wood residues. This article presents the results of a two week test campaign, in which crushed forest residues and industrial bark mixture were used as the feedstocks. The aim of the work was to carry out extended time testing of the developed gasification and hot gas cleaning process and to determine the fate of different gas contaminants and trace components of wood. In the test runs, wood fuels were gasified in the CFB reactor at a 0.2-0.25. MPa pressure using a mixture of steam and oxygen as the gasification agent. A mixture of sand and dolomite was used as the bed material in order to maintain stable fluidization and to catalyse in-situ tar decomposition before hot filtration. Raw gas was filtered at ca. 550. °C and the filtered gas was then led into a two-stage catalytic tar reformer. The gasifier performance and the concentrations of different gas contaminants were determined at four different operating variable set points during a total of 215. h of operation. The results for carbon conversion efficiency, raw gas composition and the fate of fuel nitrogen, chlorine and trace metals are presented in this paper. The concentrations of gas contaminants were determined after the ceramic filter unit and after the catalytic reformer. The conversion efficiencies for hydrocarbon gases, tars and ammonia in the reformer are also presented. The test run was carried out as a continuous operation without any interruptions or operational problems.

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.

Behaviour of tars in high temperature filtration was studied at atmospheric pressure in steam and air/steam gasification conditions. Wood pellets and bark pellets were used as feedstock and silica sand and dolomite (Myanit B) as bed materials. Experiments were carried out in a bench-scale bubbling fluidised-bed gasifier coupled with a hot gas filter unit. Interestingly, it was found that filter could act, in a sense, as a prereformer when it was operated at 800 °C. The total amount of tars in the gas was reduced on the filter in all tests regardless of the used feedstock, bed material or gasifying agent. Highest reduction, in the order of 50 wt% of total tars, was obtained in steam gasification tests when dolomite was used as bed material. It was concluded that the changes in tars are derived from thermal tar reactions due to long residence time at high temperature on the filter but also from catalytic reactions induced by the presence of unreacted biomass char and carry-over dolomite on the filter surface. Tar reduction on the high temperature filter could be beneficial for downstream units and improve their operability, especially the reformer where the lower tar level could reduce coking tendency on the catalyst

The conversion of agricultural waste materials such as bark or straw into 2nd generation biofuels constitutes an auspicious way to meet part of the future fuel demand in a sustainable way. The number of possible production routes is diverse, and the techno-economic analyses of these routes have been conducted in very different ways. The route involving gasification, gas purification, and a subsequent Fischer-Tropsch synthesis enables the production of hydrocarbons that achieve current fuel standards after upgrading in the existing refinery infrastructure. To evaluate a promising biomass-to-liquid process, a methodology is presented that incorporates economic constraints into the process design, allowing identification of a regionally optimal process design. The production costs of the new concepts are estimated by setting up a detailed flowsheet simulation in AspenPlus® based on experimental data from the successful demonstration runs of the EU-Project COMSYN. In addition, an existing techno-economic evaluation methodology incorporated into the in-house software tool TEPET (Techno-Economic Process Evaluation Tool) has been extended to evaluate the processes’ performance in different European regions and to include transportation and refining costs. The approach enables the identification of regional sweet spots shown on a map for Central-Europe, indicating production costs and favorable process design for each region. Furthermore, the results of an automated mapping for the optimal process design depending on the heat and electricity market are presented. The performed analyses show that the techno-economic evaluation tends to expand the technology in regions with low feedstock costs, while the optimal process design is defined by the regional heat and electricity market. In this work, net production costs of less than 1.12 €2019/lbiofuel were determined for regions in Hungary, Poland and Slovakia.

The share of bioenergy, including waste pulping liquors and wood fuels, in the consumption of primary energy is about 15 % in Finland, i.e. the highest in the OECD countries. There is a considerable additional use potential in cooking liquors, wood residues and agricultural crops. Compared to fossil fuels, the extent of utilization is determined primarily by the production cost of biomass, as well as by advanced conversion technology. Forest residues will be the most attractive and economical resource compared to agrobiomass, as Scandinavia's geographical position is northern and hence the harvest levels are rather low. To decrease CO2 emissions various measures will be needed: energy saving, replacing fossil fuel fired condensed power plants by CHP (combined heat and power), nuclear energy, natural gas, renewable wind and biomass, as well as reforestation as carbon sink. In CHP applications, the driving force for R & D is a higher electricity yield with a constant heat load. For biomass, the most attractive new alternatives are IGCC in a large scale and bio-oil fuelled diesel plants in a small scale parallel to today's commercial fluid-bed combustion technology. In the cogeneration and biomass scenario by VTT with carbon sinks, the CO2 emissions in Finland could, in the long term, be decreased at moderate costs by 20-40 % of the present level, and the power production could be increased by 50 % with one additional nuclear reactor. VTT's present research activities cover mainly development of IGCC and diesel power plants for various forms of biomass.

Dry-bed adsorptive desulfurization of biomass-based syngas with low to medium sulfur content using ZnO was investigated as an alternative to the conventional wet scrubbing processes. The technical feasibility of ZnO-based desulfurization was studied in laboratory-scale H2S breakthrough experiments. The experiments were set up to utilize realistic H2S concentrations from gasification and therefore long breakthrough times. Experiments were performed in a steam-rich model biosyngas in varying conditions. The long-term breakthrough experiments showed apparent ZnO utilization rates between 10 and 50% in the tested conditions, indicating intraparticle mass-transfer resistances partly due to space velocity and particle size constraints as well as the most likely product-layer resistances as evidenced by the large spent adsorbent surface area decrease. An empirical deactivation model to estimate full breakthrough curves was fitted to the laboratory-scale experimental data. Breakthrough experiment in tar-rich syngas was also performed with the conclusion that ZnO performance is not significantly affected by hydrocarbons despite carbon deposition on the particle surfaces.