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Tar decomposition by novel catalytic hot gas cleaning methods (NOVACAT)

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In some European countries (e.g. Denmark, Italy, Germany, Austria) the conditions for commercialisation of small-scale gasification-engine power plants are rather favourable at present. This is due to higher price paid in these countries for biomass-based electricity (much higher than in Finland or Sweden). When electricity production costs In Finland are compared with the present electricity prices, small-scale electricity production is not competitive with the prices paid for power producers when selling electricity to the grid. Thus, this kind of system can be competitive on the Finnish market only in three cases: - If the produced electricity can be consumed without selling to the grid. - If the biomass-based power production is subsidised by an investment support. - If feedstocks with a negative or zero price become available. With the subsidies available in Finland at the moment it can be estimated that the NOVEL CHP process payback time in the studied Finnish case lays in the range 10 - 13 years depending on electricity and district heat prices. This time can be considered acceptable in this kind of investments in Finland. The situation improves considerably if REF fuels having negative price are used. The payback time cuts to around 5 years in the studied case. In the studied Italian cases, characterised by high price of electricity, the pay-back times are markedly lower than in Finland, 3 - 6 years, even with standard biomass prices in Italy. Use of catalytic filter unit instead of gas reformer and filter cuts also the costs and the pay-back time decreases. This analysis indicates clearly the economical benefits that can be gained by simplifying the process and justifies further development of this concept. The technical and economical datas of the NOVEL gasifier are a promising base for promoting the plant. The interesting aspects are the reduced size of the plant, the continuous operational system and the capability of gasifying various types of biomass, without endangering the performance of the gas engine. With these characteristics the diffusion of the technology can be successful, especially under the current Italian market conditions. The implementation of the wood-based gasification technology seems to be promising in Umbria and do not seem to pose particularly exigent environmental problems, providing that the legislation framework evolves in a way that promoters are encouraged. From a technical viewpoint further efforts would be needed in order to assess viable applications for the excess heat that is produced in a gasification plant. The recovery of high entropy energy within a CHP concept would represent an added value to the work and make the plant profitability even higher. Although CHP is almost an unknown practise in Umbria and no heat districts actually exist, the scope for excess heat end user applications can be devised including: cooling districts for civil uses, pre-heating of biomass feedstocks, greenhouse farming, industrial applications (e.g. for woodworks).
Nickel monolith catalyst has been exposed to real gas at optimal operation conditions. These conditions ensure soot-free operation of the system. Catalyst activity during 2300 operation was monitored. Catalyst activity at the end of the test was high and it is expected that the catalyst can be applied in economically feasible way in gasification processes. End users of the results are other partners of the consortium and companies and research groups developing catalytic gas cleaning for gasification processes. The information created is public, some parts of the reactor design are proprietary. It will be published in international journals and conferences when available. It can be used as a basis for design and in economical evaluation of gasification processes having a catalytic gas cleaning system.
A novel catalytic candle filter for the integrated high temperature removal of tars and particles from the biomass gasification gas has been developed. The catalytic candle filters are alfa-alumina ceramic filters containing a suitable nickel/magnesium oxide tar cracking catalyst in their pores. This not only avoids mass transfer limitations occurring in packed beds of such catalysts, but also yields a reduced investment cost for the cleanup step. Optimal preparation procedure (co-precipitation through urea method), Ni/MgO-ratio, catalyst loading, and surface area of the support have been determined. In addition optimal operation conditions have been investigated by variation of temperature, gas velocity, H(2)S-content and tar content. At 900°C, a gas velocity of 2.5cm/s, a H(2)S-content of 100ppm, a tar content up to 5g/Nm{3}, tar conversions of 99.98% can be reached with a catalytic filter containg 1 wt% Ni + 0.5 wt% MgO and a alumina support specific surface area of 2.35m{2}/g. End users of these results are other partners of the consortium and companies developing catalytic gas cleaning for gasification processes. Some parts of the information will be published in international journals and conferences if considered appropriate. Results can be used as a basis for design and scale-up of catalytic gas cleaning processes.

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