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Title:
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Primary measures to reduce tar formation in fluidised-bed biomass gasifiers: Final report SDE project P1999-012
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Author(s):
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Kiel, J.H.A.; Paasen, S.V.B. van; Neeft, J.P.A.; Devi, L.; Ptasinski, K.J.; Janssen, F.J.J.G.; Meijer, R.; Berends, R.H.; Temmink, H.M.G.; Brem, G.; Padban, N.; Bramer, E.A.
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Published by:
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Publication date:
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ECN
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1-3-2004
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ECN report number:
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Document type:
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ECN-C--04-014
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ECN publication
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Number of pages:
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Full text:
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108
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Download PDF
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Abstract:
The main objective of the work described in this report has been toadvance the knowledge base on tar formation in air-blown, atmospheric-pressure
fluidised-bed gasification of woody biomass, in particular with respect
to:
·the effect of various fuel properties and gasifier operating conditions,
·the underlying mechanisms, and
·the impact of the resulting tar concentration and composition on the
performance of downstream processes.
With respect to the latter, water solubility and condensation behaviour,
expressed in terms of the tar dewpoint, were identified as the most
important tar properties. The work was focussed mainly on bubbling-fluidised-bed
(BFB) gasification, but circulating-fluidised-bed (CFB) gasification
was addressed as well. Furthermore, much attention was given to the
definition, measurement and classification of tar. In this respect,
tar was defined as "all organic compounds with a molecular weight larger
than benzene (excluding soot and char)". Measurement of individual tar
compounds was conducted using either the Solid Phase Adsorption method
or the Guideline method.
In an extensive experimental programme, the impact on tar formation
of three fuel properties (ash content, moisture content and lignocellulose
composition) and three operating conditions (gasification temperature,
gas residence time and bed material/additives) was determined in lab-scale
bubbling-fluidised-bed gasifiers. The results were found to be representative
for circulating-fluidised-bed (CFB)-gasification as well, provided that
differences in gasification temperature and gas residence time (distribution)
are taken into account. The report contains data to account for these
differences. In addition to the experimental work, attempts were made
to model tar formation.
Subsequently, the advanced knowledge base was applied to assess the
practical and economic feasibility of identified, most promising primary
measures.
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