Agglomeration behaviour of high ash Indian coals in fluidized bed gasification pilot plant
Although gasification of high ash Indian coals is gaining importance, the resultant uncertainties associated with agglomerate formation are still unresolved. To address this, a suitable pilot scale Fluidized Bed Gasifier was utilized in this study. Stabilized operating conditions in terms of coal fe...
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Veröffentlicht in: | Applied thermal engineering 2015-07, Vol.86, p.222-228 |
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Sprache: | eng |
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Zusammenfassung: | Although gasification of high ash Indian coals is gaining importance, the resultant uncertainties associated with agglomerate formation are still unresolved. To address this, a suitable pilot scale Fluidized Bed Gasifier was utilized in this study. Stabilized operating conditions in terms of coal feed rate, air feed rate, bed temperature, etc., already identified for maximum possible carbon conversion, were maintained in all experiments and the steam flow rate was only varied. Though the ash fusion temperature of the coals were above 1200 °C, agglomerate was formed during gasification at 950 °C with ‘steam to coal ratio’ less than 0.15 (kg/kg). On increasing this ratio above 0.2 local heat-concentration and agglomeration could be avoided with certainty. Chemical composition alone was not sufficient to explain the relative strength of ash-agglomerates. Compositional variation and state of iron within the matrix were assessed through SEM-EDX and electron paramagnetic resonance (EPR) study, respectively. The probing also required the ash-loading and iron-loading factors to be freshly defined in the context of gasification. Localized heat, large compositional variation, presence of iron in Fe2+ state, ash-loading/iron-loading factors influenced intensity of agglomerate formation. Finally, low temperature agglomerate formation was explained by SiO2–Al2O3–FeO phase diagram.
•Pilot plant studies on agglomerate formation during high ash coal gasification.•AFT, chemical analysis of coal ash could not give proper indication.•Ash-/iron-loading factors, compositional variation, Fe2+ leads to agglomeration.•Steam to coal ratio was controlled judiciously to avoid agglomeration.•Cause for agglomeration investigated in depth and remedial adjustment was focused. |
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ISSN: | 1359-4311 |
DOI: | 10.1016/j.applthermaleng.2015.04.046 |