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Title:
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Ash behaviour in entrained-flow gasification: preliminary studies
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Author(s):
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Published by:
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Publication date:
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ECN
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1-4-1999
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ECN report number:
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Document type:
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ECN-C--99-037
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ECN publication
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Number of pages:
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Full text:
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53
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Download PDF
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Abstract:
To support and ensure a successful introduction of entrained-flowgasification based technologies in general, and a successful operation of the
world's first fully Integrated Gasification Combined Cycle (IGCC)
demonstration plant in Buggenum, Netherlands (Demkolec plant, 253 MWe), in
particular, ECN was asked to initiate laboratory-scale research on specific
problem areas. In a prior feasibility study, important (mostly ash-related)
possible problem areas were identified and it was concluded that
laboratory-scale experimental studies into these problem areas would largely
benefit from an adequate simulation of the actual conditions encountered by
the fuel particles in a full-scale process. In particular, it was considered
essential to closely mimic the extreme initial conditions, viz. heating rates
equal to or even in excess of 10"5-10"6 "oC/s and initial gas temperatures in
excess of 2000C, since the initial stage is the precursor stage for all
downstream processes such as char gasification, slagging and fouling. A new
experimental concept was proposed to meet these conditions, comprising a
laboratory-scale pressurised entrained-flow reactor with an integrated staged
flat flame gas burner. In subsequent studies, this new concept was elaborated
resulting in the design and construction of the so-called Pressurised
Entrained-Flow Gasification simulator (PEFG- simulator). During these studies
it became clear, however, that the realisation of such a PEFG-simulator is
not a simple, straightforward effort and that the operation may be complex
and time-consuming. Furthermore, as it is with every first-of-a-kind
facility, it was expected that many 'growing pains' would have to be overcome
during the commissioning phase. Therefore, it was decided to reconstruct the
existing atmospheric-pressure staged flat flame gas burner facility at ECN,
which was applied extensively in coal combustion studies, to enable a series
of atmospheric-pressure preliminary studies in support of the PEFG-simulator
design, construction and commissioning. Several of these preliminary studies
are described in this report. Firstly, new improved measurement techniques
for the determination of axial temperature and gas concentration profiles had
to be developed and tested. Secondly, extensive experimental efforts were
devoted to finding proper operating conditions for the multi-stage flat flame
gas burner. And finally, a series of preliminary ash formation and ash
deposition experiments was conducted to elucidate the possibilities of the
new laboratory-scale entrained-flow gasification simulation concept with
respect to improving the understanding of slagging-phenomena in
entrained-flow gasifiers. In general, it can be concluded that the design and
commissioning of the Pressurised Entrained-Flow Gasification simulator
(PEFG-simulator) have benefied considerably from the atmospheric-pressure
preliminary studies. Methods were developed for the determination of axial
gas composition and temperature profiles, which can be applied in the
PEFG-simulator with only minor adaptations. In addition, information was
obtained on the stable operating windows of the staged gas burner for the
specific gas mixtures, required to achieve an accurate simulation of
entrained-flow gasification conditions, which forms a valuable starting point
for the determination of these windows at elevated pressure. Furthermore, the
preliminary studies led to several changes in the design of the PEFG-
simulator. The preliminary ash formation and ash deposition experiments in
itself revealed valuable information with respect to slagging-related ash
behaviour in (oxygen-blown) entrained-flow gasification processes. For
excluded pyrite minerals, preliminary mechanistic models could be derived
describing and explaining the pyrite transformations both before and after
deposition. The studies on the fate of two other minerals, viz. calcite and
quartz, and of mineral enriched Goettelborrn coal were more phenomenological
in nature. A more detailed interpretation of the experimental results and
additional experiments are required to develop similar mechanistic models for
these other minerals and to develop models for the (slagging) behaviour of
mineral mixtures. This will be the subject of future work, in which also the
Pressurised Entrained-Flow Gasification simulator will play an important
role. 16 refs.
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