Packed Bed Combustion
Dr. W. Hallett
Packed bed combustion, also called mass burning, is the burning of
solid fuels
on a grate, with air supplied from below. It is used industrially for
burning wood
and biomass in the pulp and paper industry, for trash incineration, and
for small
community district heating systems in remote regions. On a small scale,
this is the
sort of combustion that occurs in wood and coal stoves.
In spite of the industrial importance of this mode of combustion, there is little up-to-date information on it, and few recent attempts to model it. Many of the models available in the literature have been simplified by omitting important details of the process. In addition to this, there is no recent experimental data for testing models (our first efforts at numerical modelling had to be tested with data from 1935!). Our research is therefore aimed at the development of complete numerical models of this process and their verification through carefully controlled experiments.
Solid
fuel combustion takes place in two stages. When the fuel is first
heated, it breaks
down chemically, a process called pyrolysis, producing combustible
gases (volatiles) which
then burn in the gas phase. The residue from this process, called char,
is mostly solid
carbon and ash, which then burns in the solid phase. The first stage in
this research was to
develop a complete numerical model of char combustion processes in the
fuel bed, which
was subsequently verified in a comprehensive series of experiments
using coke as the fuel.
An important and novel component of this work has been the development
of a reasonably
detailed model for ash behaviour. We have now added a simple model for
pyrolysis to the
numerical model and tested it with experiments on wood. Current
objectives are the
development of more complete models for pyrolysis and for single
particle behaviour as
well as further investigation of ash behaviour.
For further details, go to the appropriate link.
Experiments and Lab Facilities
Numerical modelling Publications
Girgis, E., Hallett, W.L.H. Wood Combustion in an Overfeed Packed
Bed, Energy & Fuels 24, 1584-1591, 2010.
Cooper, J., Hallett, W.L.H., A numerical model for packed bed combustion of char particles, Chemical Engineering Science 55, 4451-4460 (2000)
Hallett, W.L.H., Packed bed combustion: An overview, plenary
lecture, Combustion Institute Canadian Section Spring Meeting 2005 (to
view the slides, follow this link)
Hallett, W.L.H., Yang, Y., Particle Size Effects in Packed Bed
Combustion - II, Combustion Inst. Canadian Sect. Spring Meeting 2010,
pp. 105-110.
Green, B., Hallett, W.L.H., Particle Size Effects in Packed Bed
Combustion, Combustion Inst. Canadian Sect. Spring Meeting 2009, pp.
277-282.
Tuck, A.R.C., Hallett, W.L.H., A Particle-Resolved Model for Packed
Bed Combustion of Solid Fuels, Combustion Inst. Canadian Sect. Spring
Meeting 2007, Session I, Paper 1, pp. 1-6.
Tuck, A.R.C., Hallett, W.L.H., Modelling
of particle pyrolysis in a packed bed combustor, Combustion Inst.
Canadian Sect. Spring Meeting 2005, pp. 250-253.
Girgis, E., Hallett, W.L.H. Packed bed combustion of wood, Combustion Inst. Canadian Sect. Spring Meeting 2003, pp. 42.1 - 42.6.
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Last updated 13 August 2010