Occurrence, composition and dew point of tars produced during gasification of fuel cane bagasse in a downdraft gasifier

Gasification of pelletised fuel cane bagasse a waste residue from an energy crop known as fuel cane was investigated to evaluate the potential of fuelling solid oxide fuel cells (SOFCs) with the raw fuel gas produced. Tars produced during gasification of the bagasse in a 50 kWe air-blown downdraft autothermal gasifier were collected, quantified and characterised and the tar dew point evaluated. The concentration of tar collected was 376 ± 27 mg m−3 of dry syngas (at 273 K, 101 kPa), emphasising the efficiency of the tar cracking reactions in the oxidation zone of the gasifier. However, although tar production was low, the typical mixture of tar compounds produced exhibited a high tar dew point of 90 ± 5 °C and was dominated by Class 2 and 5 tars which condense readily even at low concentrations. Additionally Class 1 tars had a mass fraction of 8% of the total tar produced. Therefore the calculated tar dew point underestimates the actual tar dew point and a high potential for fouling of SOFC anodes exists. Consequently primary or secondary gas cleaning treatment measures targeting the production or occurrence of Class 1, 2 and 5 tars will be essential for long term operation of SOFC power generating systems fuelled by raw fuel gas from fuel cane bagasse.

► Quantity and distribution of tars produced during gasification are evaluated.
► The quantity of tar produced was low (376 mg N m−3 dry syngas).
► Dominant tars were Classes 2 and 5 which condense readily even at low concentrations.
► Class 1 tars only constituted 8% of total.