Sep 1, 2011

EDEM Gives Boost to Green Technology

Particles in an annular fluidized bed, shown at the moment of fluidization. EDEM is a key tool in understanding chaotic systems and allows the interactions of particles of different sizes and morphologies to be studied in great detail

Rowan Braham, David Fletcher, and Andrew Harris, at the University of Sydney Laboratory for Sustainable Technology, have been applying EDEM® bulk particle engineering simulation technology to virtually test the performance of prototypes for a solar-powered air cleaner.

In an excellent example of green chemistry, their prototypes focus the sun’s ultraviolet light on particles of silica gel that have been coated with a thin-film of a titanium dioxide-based chemical catalyst. The catalyst is photo-activated when the appropriate wavelength of light shines on it, creating positive and negative charges on the surface of the particles. These charges are then available to initiate various chemical reactions.

When contaminated air is directed upwards through the unit--creating a fluidized bed photo reactor—contaminants that contact the photocatalytic particles are absorbed onto the particle surfaces. The contaminants react with the positive and negative charges and are chemically broken down. The result is purified air.

The unit efficiency relies on good exposure of the particles to the light source and good interaction of particles with the incoming air. To model and optimize the movements of particles within the unit, the researchers have deployed EDEM bulk particle engineering simulation software. By including the EDEM–CFD coupling, they are also able to simulate the flow of gas upwards thru the bed of particles. The resulting visualization and analysis of particle movement within the reactor unit show how well particles are circulated for even exposure to the light source and the incoming contaminants. With this model in place, the researchers can investigate the effects of varying operating parameters such as gas flow rate, particle size, and particle load.

In an additional step, a custom program, developed at the University of Sydney, uses the EDEM-CFD data to analyze how well light entering the reactor interacts with the particles.

"Using EDEM means we are able to study the behavior of the photoreactor at a level of detail which is not available through other modelling methods,” explained Rowan Braham. “Fluidized beds are chaotic, dynamic systems, and being able to analyze the forces acting on each individual particle is crucial for correctly predicting their behavior - especially once we start looking at more complicated gas flow regimes and particle configurations, where older modelling methods often break down."

Braham recently won First Prize for his research at the NSW / ACT Postgraduate Student Energy Awards, a highly competitive competition held annually by the Australian Institute of Energy.

The next step? Braham plans to use the results from EDEM simulations, in conjunction with information gained from laboratory scale photo reactors, to assess the highest performing designs-- one of which is a unique “swirling” fluidized bed-- for feasibility in industrial and commercial applications.

About the Laboratory for Sustainable Technology:
The University of Sydney Laboratory for Sustainable Technology, within the School of Chemical and Biomolecular Engineering, conducts multidisciplinary research to develop sustainable products and processes which maximize resource and energy efficiency and minimize environmental impact.