Modelling of dynamics of combustion of biomass in fluidized beds

Jaakko Saastamoinen

Research output: Contribution to journalArticleScientificpeer-review


New process concepts in energy production and biofuels, which are much more reactive than coal, call for better controllability of the combustion in circulating fluidized bed boilers. Simplified analysis describing the dynamics of combustion in fluidized bed and circulating fluidized bed boilers is presented. Simple formulas for the estimation of the responses of the burning rate and fuel inventory to changes in fuel feeding are presented. Different changes in the fuel feed, such as an impulse, step change, linear in crease and cyclic variation are considered. The dynamics of the burning with a change in the feed rate depends on the fuel reactivity and particle size. The response of a fuel mixture with a wide particle size distribution can be found by summing up the effect of different fuel components and size fractions. Methods to extract reaction parameters form dynamic tests in laboratory scale reactors are discussed. The residence time of fuel particles in the bed and the resulting char inventory in the bed de crease with increasing fuel reactivity and differences between coal and bio mass is studied. The char inventory affects the stability of combustion. The effect of char inventory and oscillations in the fuel feed on the oscillation of the flue gas oxygen concentration is studied by model calculation. A trend found by earlier measurements is explained by the model.
Original languageEnglish
Pages (from-to)107-126
JournalThermal Science
Issue number2
Publication statusPublished - 2004
MoE publication typeA1 Journal article-refereed


  • fluidized beds


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