• Output from the EDF Coal Characterisation Workshop

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A workshop was held at EDF R&D recently entitled “Combustion characterisation techniques for pulverised coal/ Needs for modelling and validation of coal combustion in PC boilers.”  The workshop was part of the EDF-IFRF Work-out program “Methodology for the characterization of pulverized coals: the need, the experimental conditions to obtain reliable data” – which started this year and will continue during 2010, with both experimental and model validation activities.

The aim of this particular encounter between some 25 representatives from academia and industry across Europe was to define the information needed for comprehensive modelling of coal combustion and the techniques and methods to obtain such information.

IFRF and EDF research groups introduced the meeting and addressed the main objectives in two presentations: “Needs for modelling and validation of coal combustion in boilers (IFRF), and “Code-Saturne®: The 3D modelisation of the coal combustion/oxy-combustion/co combustion in Boilers” (EDF).

The common approach is based on CFD using numerical solutions of multidimensional, differential equations for conservation of mass, energy, and momentum, and coupling other submodels within this framework to account for gaseous species mixing and chemical reactions, solid fuel particle devolatilization and char oxidation, and radiant energy transport.  Since a comprehensive model must balance submodel sophistication with computational practicality, much of the research in this field is aimed at both improved solution techniques, and new or more “efficient” submodels able to provide practical engineering solutions.

In the presentations the solid fuel properties to be considered as inputs in coal combustion comprehensive modeling were considered (immediate and ultimate analysis, particle size distribution, density, shape factor, ash composition, etc.), and approaches and correlations to be used in sub-models were reviewed (devolatilisation and volatile composition, homogeneous combustion chemistry, char burnout sub-model, etc.)

On the experimental side, the IFRF team presented an overview on solid fuel characterisation methods and related modelling issues, and then the discussion was focussed on the most common methodology for getting high temperature, high heating rate information on coal combustion: Isothermal Plug Flow Reactors/Drop tubes.  For the latter, examples of methodologies, uncertainties evaluation, and brand new data were shown by IFRF and University of Haute Alsace researchers.  Particular attention was devoted to the assessment of experimental uncertainties, coupling experimental characterization of devices with CFD modeling of their performances as well.

Finally the status of the IFRF Solid Fuel Database was reported, including examples on kinetics assessment on devolatilisation and char oxidation by analysis of raw data produced by drop tube devices.

The presentations and a wrap up report will be published shortly in the Conferences, Workshops and TOTeMs section of the IFRF website.  Watch MNM for details.

A benchmarking programme for drop tubes/entrained flow reactors will be activated for defining qualification procedures for such devices.  A comparison among different devices is also planned in the EFRI programme.

Member Organisations who want to share their DT/EFR data for developing common procedures for qualification and kinetic data abstraction should contact Leo Tognotti through the SFDB Forum on the IFRF website.