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Ash behaviour in entrained-flow gasification: preliminary studies
Gepubliceerd door: Publicatie datum:
ECN 1-4-1999
ECN publicatienummer: Publicatie type:
ECN-C--99-037 ECN rapport
Aantal pagina's: Volledige tekst:
53  Niet beschikbaar.

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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