Dynamics of combustion of solid fuel particles in a fluidized bed under pressure

The existing difference in the models used to describe the burning rate of solid fuel particles, and, accordingly, the difference in the constants appearing in them, determines the relevance of the formulation of the relation between the constants known from the literature and the parameters that must be set in programs for CFD modeling of heat and power processes. This, in particular, relates to modeling the combustion of solid fuels in the well-known program ANSYS FLUENT. The paper outlines a possible approach to solving this problem. Bibl. 5, Fig. 3.

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Modelling of dynamics of combustion of biomass in fluidized beds

Thermal Science ◽

10.2298/tsci0402107s ◽

2004 ◽

Vol 8 (2) ◽

pp. 107-126 ◽

Cited By ~ 8

Author(s):

Jaakko Saastamoinen

Keyword(s):

Particle Size ◽

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Fuel Mixture ◽

Linear Increase ◽

Fuel Feed ◽

New Process ◽

Fuel Particles ◽

The Stability ◽

Fluidized Bed Boilers

New process concepts in energy production and biofuel, 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 increase 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 decrease with increasing fuel reactivity and differences between coal and biomass 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.

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Applicability of Scaling Approach for Analysis of Pyrolysis and Gasification of Porous Structures Composed of Solid Fuel Particles

ISRN Mechanical Engineering ◽

10.5402/2012/207464 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10

Author(s):

Aliaksandr Alevanau ◽

Pawel Donaj ◽

Weihong Yang ◽

Wlodzimierz Blasiak

Keyword(s):

Experimental Research ◽

Solid Fuel ◽

The Self ◽

Porous Structures ◽

The Best Approximation ◽

Self Organized ◽

Volumetric Models ◽

Fuel Particles ◽

Kinetics Of ◽

Reactive Properties

Experimental research on the pyrolysis and gasification of randomly packed straw pellets was conducted with an emphasis on the reactive properties of the shrinking porous structure of the pellets. The apparent kinetics of such pyrolysis was approximated by the random pore, grain, and volumetric models. The best approximation results were obtained with the grain and random pore models. The self-organized oscillations of the pellet conversion rate during pyrolysis were observed. Two complementary explanations of the phenomenon are proposed.

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