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.

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Pressurized circulating fluidized‐bed gasification by steam‐oxygen has been developed at VTT for syngas applications. In this process, wood feedstocks are first converted into raw gasification gas, which is then filtered at about 600°C before catalytic reforming of tars and hydrocarbon gases. This article presents results of the gasification and gas filtration tests carried out with wood pellets, crushed pellets, bark, and crushed forest residues. The effects of operating pressure, bed material used, and other main operating variables were examined. Dolomite, magnesium oxide, and sand were used as bed materials. Gasification pressure was in the range 0.25–0.6 MPa and operating temperature 860–930°C. In best operating conditions, over 98% carbon conversion was achieved with very smooth long‐term operation. The feedstock particle size, operation pressure, and the presence of calcium‐based bed material had strong effects on tar formation and filter operability. © 2014 American Institute of Chemical Engineers Environ Prog, 33: 681–687, 2014

A flexible combined heat, power and fuel production concept, FlexCHX, is being developed for managing the seasonal mismatch between solar energy supply and the demand for heat and power characteristic of Northern and Central Europe. The process produces an intermediate energy carrier (Fischer-Tropsch hydrocarbon product), which can be refined to transportation fuels using existing refineries. The FlexCHX process can be integrated into various combined heat and power production systems, both industrial CHPs and communal district heating units. In the summer season, renewable fuels are produced from biomass and hydrogen; the hydrogen is produced from water via electrolysis that is driven by low-cost excess electricity from the grid. In the dark winter season, the plant is operated only with biomass in order to maximize the production of the much-needed heat, electricity and FT hydrocarbons. Most of the invested plant components are in full use throughout the year with only the electrolysis unit being operated seasonally. The catalytic reformer plays a key role in this process by converting tars and light hydrocarbon gases into synthesis gas and by bringing the main gas constituents towards equilibrium. Developmental precious metal catalysts were used, and an optimal reformer concept was established and tested at pilot scale. Reforming results obtained at pilot gasification tests with commercial nickel catalysts and with the developed precious metal catalysts are presented.

Electrochemical hydrogen permeation experiments were performed on polycrystalline nickel and nickel-base alloys in order to study the factors affecting the entry and transport of hydrogen in such materials. The diffusivity of hydrogen is found to be dependent upon alloy composition, prior cold work, and the concentration of hydrogen absorbed into the solid. The addition of P, S, and As compounds to the electrolyte promotes hydrogen absorption as expected. Within the limits of the experimental approach pursued in this study, thermal treatment intended to induce grain boundary solute segregation did not appear to affect hydrogen permeation characteristics. On the other hand, nickel-base glassy alloys, which are considered to be bulk analogs of segregated grain boundaries in nickel, are found to absorb considerable amounts of hydrogen. The Jatter suggests that segregated impurities may induce intergranular cracking by promoting hydrogen absorption at grain boundaries and in their vicinity.