Title:
Precipitation of Coarse Fly Ash Particles in Wood Chip Boilers - A Comparison of Experimental and Numerical Investigation
Author(s):
Lamprecht, M., Hofmeister, G., Heschl, C.
Document(s):
Paper
Slide presentation
Abstract:
Primary measures for dust emission reduction of biomass boilers require a detailed knowledge about the particle sources and the particle depositions. Especially in case of coarse fly ash particles (>PM2.5) the flow design should ensure a complete separation of the particles inside the boiler. Computational Fluid Dynamics (CFD) enables a closer analysis of the momentum exchange between the flue gas and the particles and therefore CFD is widely used for the preliminary design process. However the reliable application assumes that the release and the properties of the particles are well known. Hence a test run with a small-scale wood chip burner (50kWth) has been taken to determine the boundary condition and to validate the numerical calculation. Measurement of mass (air input, fuel input, dust emission) and heat fluxes (thermal output) as well as composition of gaseous emissions enabled mass and energy balancing. After the test run of 39.15 hours, boiler ashes and deposition formation were collected and analysed. Based on a stationary combustion calculation using the “Eddy-Dissipation-Model” with a global methane 3-step mechanism, particle trajectories were calculated by the Euler-Lagrange approach using the “Discrete Phase Model” in ANSYS® FluentTM . Numerical calculation of precipitated coarse fly ash particles showed a good accuracy in comparison to the experimental data, with an overall deviation of -6.94 wt.-% (numerical underpredicted) fora steady flow field and -6.28 wt.-% using a stochastic tracking approach.
Keywords:
biomass, ashes, particle emission, CFD, Euler-Lagrange
Topic:
Industry Sessions
Subtopic:
Power & Heat processes and systems
Event:
23rd European Biomass Conference and Exhibition
Session:
IBO.8.5
Pages:
1693 - 1702
ISBN:
978-88-89407-516
Paper DOI:
10.5071/23rdEUBCE2015-IBO.8.5
Price:
FREE
