Ash formation during pilot-scale trials of pressurized entrained-flow gasification of woody biomass

• Deposits, ash samples and residues from pressurised entrained-flow gasification (PEFG) of stem wood, bark and rejected pulpwood have been characterised with SEM-EDS during trials in an O2-blown pilot-scale reactor. Global thermochemical equilibrium calculations based on the conditions inside the hot reactor were carried out to investigate the phase distribution of potassium as both a function of temperature and Si reactivity. Substantial deposit formations on the reactor probe were only evident in the trials with the woody fuels containing a higher ash content; i.e., experiments with pulpwood and bark. Of these, the deposits formed during gasification of the pulpwood fuel, likely to have been relatively highly contaminated, showed more hard and sintered material. The deposits/slag formed contained typical sand particles (e.g. quartz and feldspars) embedded in a silicate rich melt. The melt in the slag is dominated by silicon 40-55 mol%, aluminium ~15 mol% and calcium 10-20 mol%, with a further ~10 mol% consisting of alkali metals sodium and potassium. The preliminary results suggest that fuel contaminants (e.g., quartz and feldspars) may play a significant role in the slag formation process in entrained flow gasification of woody biomass fuels and that a significant share of the potassium is leaving the hot reactor as gaseous alkali species.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

Energy Engineering

Energiteknik

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