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 Students
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)
Ryan, J.S., Hallett, W.L.H., Packed bed combustion of char particles: Experiments and an ash model, Chemical Engineering Science, 57, 3873-3882 (2002)
Cooper, J., Hallett, W.L.H., A
numerical model for packed bed combustion of char particles, Chemical
Engineering
Science 55, 4451-4460 (2000)
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.
Ryan, J.S., Hallett, W.L.H., Packed bed char combustion: model verification and extension, Combustion Inst. Canadian Sect. Spring Meeting 2000, pp. 45-1 - 45-6
Ryan, J., Hallett, W.L.H., Di Iorio, J.M., Experiments on solid fuel combustion in an overfeed bed, Combustion Inst. Canadian Sect. Spring Meeting 1999, pp. 99-21-1 - 6.
Ryan, J., Hallett, W.L.H., A model for ash behaviour in fuel bed combustion, Combustion Inst. Canadian Sect. Spring Meeting 1999, pp. 99-22-1 - 6.
Ryan, J., Hallett, W.L.H., Experiments on char combustion in a packed bed, Combustion Inst. Canadian Sect. Spring Meeting 1998, pp. 3-15 - 3-19.
Cooper, J., Hallett, W.L.H., A numerical model for packed bed overfeed char combustion, Combustion Inst. Canadian Sect. Spring Meeting 1996, pp. 6-1 - 6-5.
Arden Tuck (MASc, Chemical Engineering, in progress) - detailed modelling of particle processes
Elisabeth Girgis (MASc, Chemical Engineering, in progress) - devolatilization/wood combustion - experiments and model
Jennifer Ryan (MASc, Chemical Engineering, 2000 - presently with CANMET, NRCan) - development of instrumentation, experiments on coke, ash model development
Joanna Di Iorio (fourth year thesis, Chemical Engineering, Winter 1999) - first experiments on wood combustion
Judy Cooper (MASc, Chemical Engineering, 1996 - presently with AEA Technology Engineering Software Ltd., Waterloo) - development of model for char combustion
Laura Gibbs (MASc, Chemical Engineering, 1989 - presently with Environment Canada) - earlier work on modelling of coal devolatilization
Funding
Natural Sciences and Engineering Research Council, Canada (operating grant, equipment grant)
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Last updated 30 May 2005