The EU Biofficiency project (2016-2019): executive summary

The EU funded project Biofficiency developed some tests on pre-treated fuels and a blueprint for the modern biomass cogeneration plants. We summarize the key conclusions which relate to fuel ash.

  • Additives and materials
    • Deposits tests in PF boilers to reduce deposition showed that the additive amount has a greater important than the type of additive. In particular, within the 4 MW CFB tests, elemental S was found to be the most cost-effective additive (with respect to kaolin). 200 kW tests showed that in PF beech wood combustion with 1% kaolin decreased PM1 emissions by 33%; by 75% with 2.4% kaolin.
    • 800 MWth CHP Avendore U2 and Studstrup U3 tests showed that coal fly ash addition decreased the submicron aerosol particles, but kept the K-Ca-S sintered downstream deposits (sootblowing was maintained). SH Cl corrosion on TP347H/HFG, SUPER 304H, Esshete 1250 was mitigated with 2,5% coal fly ash addition, but corrosion by sulphidation was observed.
    • With lab tests to test high steam temperature, at 650°C, only the austenitic SS TP310HCbN survived to heavy KCl corrosion.
  • Pre-treatments
    • Torrefaction increased the ash content without causing compositional changes, but if followed by a washing step it decreased alkali and Cl content, consequently increasing ash melting temperatures.
    • Steam explosion did not induce significant ash compositional changes, a slightly decreased ash melting temperature was found.
    • Hydrothermal carbonization decreased alkali and Cl content, yielded high Si-ashes and higher melting temperatures.
    • Detailed fuel and ash data are now publicly available and those could be used in our numerical modelling.
  • State of the art PF power plant design expected at 2.7 k€/kWel: 300 MWth, 560°C steam temperature and 92-94% efficiency, fuelled by wood pellets, dry de-ashing with ash recirculation, additivation with coal fly ash for SH and Denox SCR reactor protection including ash utilization oriented plant operation.

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