engleski

Modelling of Coal Early Devolatilisation in a Turbulent Jet Flame

A numerical study has been undertaken which simulate an experiment where a solid fuel particle-laden round turbulent air jet emerges into a hot environment. The experiment gives particular emphasis to the devolatilisation phenomenon. Appropriate buoyancy parameters were incorporated in an existing parent code. The k-ε turbulence model in standard form gave less than good predictions of the physical behaviour of the basic flow. Improved predictions were obtained after modifying the values of the turbulence model constants (Cµ and Cε2). Predictions of flame stability and NOx emission behaviour were obtained for nine pulverised coals. They were: Gedling, Thoresby, South Brandon and Asfordby – UK ; Pittsburgh No. 8 – USA ; Koonfonteine – South Africa ; La Jagua – Colombia ; Hunter Valley – Australia ; and Kaltim Prima – Indonesia. Global kinetic parameters were established for their devolatilisation rates. The NOx emission levels proved to be mainly dependent on the amount of nitrogen released from the fuel ; showing that the bulk of the NOx formation from the fuel nitrogen occurs in a process that mainly follows coal devolatilisation.

Coal, Devolatilisation, Burnout, Modelling, NOx

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