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A conversion-class model for describing fuel conversion in large-scale fluidized bed units

Louise Lundberg (Institutionen för energi och miljö, Energiteknik) ; Robert Johansson (Institutionen för energi och miljö, Energiteknik) ; David Pallares (Institutionen för energi och miljö, Energiteknik) ; Henrik Thunman (Institutionen för energi och miljö, Energiteknik)
Fuel (0016-2361). Vol. 197 (2017), p. 42-50.
[Artikel, refereegranskad vetenskaplig]

Solid fuel conversion in fluidized beds is often modelled with the use of population balances, where the fuel conversion process is divided into a number of classes based on for example fuel particle size. The present work investigates and evaluates different methods for the discretisation of the fuel conversion process into classes, as well as the number of classes necessary to yield a satisfactory accuracy. A discretisation method, which defines classes based on the conversion degree (rather than size or density) and that is valid for all conversion regimes, is proposed. The results show that application of the proposed class division method for modelling biomass gasification in a fluidized bed gives an accuracy that is up to ten times higher than that given by a distribution with equally large classes. For all three conversion processes of biomass gasification (drying, pyrolysis, and char gasification), discretisation into 6 classes is sufficient to yield errors of around 1%, when compared to the continuous conversion curves given as input to the conversion class discretisation model (generated by a particle model in the present work). In line with this, when the conversion class model is used in a semi-empirical 1D model of indirect biomass gasification, the resulting char conversion in the gasifier does not change significantly when more than 3–6 char conversion classes are used.

Nyckelord: combustion, fluidized bed, fuel classes, fuel conversion, gasification, population balance



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Denna post skapades 2017-03-05.
CPL Pubid: 248422

 

Institutioner (Chalmers)

Institutionen för energi och miljö, Energiteknik

Ämnesområden

Energi
Hållbar utveckling
Termisk energiteknik

Chalmers infrastruktur