Gas dispersion and immobile gas volume in solid and porous particle biofilter materials at low air flow velocities

• Gas-phase dispersion in granular biofilter materials with awide range of particle sizes was investigated using atmosphericair and nitrogen as tracer gases. Two types ofmaterials were used: (1) light extended clay aggregates(LECA), consisting of highly porous particles, and (2)gravel, consisting of solid particles. LECA is a commercialmaterial that is used for insulation, as a soil conditioner,and as a carrier material in biofilters for air cleaning. Thesetwo materials were selected to have approximately thesame particle shape. Column gas transport experimentswere conducted for both materials using different meanparticle diameters, different particle size ranges, and differentgas flow velocities. Measured breakthrough curveswere modeled using the advection-dispersion equationmodified for mass transfer between mobile and immobilegas phases. The results showed that gas dispersivity increasedwith increasing mean particle diameter for LECAbut was independent of mean particle diameter for gravel.Gas dispersivity also increased with increasing particlesize range for both media. Dispersivities in LECA weregenerally higher than for gravel. The mobile gas contentin both materials increased with increasing gas flow velocitybut it did not show any strong dependency onmean particle diameter or particle size range. The relativefraction of mobile gas compared with total porosity washighest for gravel and lowest for LECA likely because of itshigh internal porosity.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik -- Annan naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering -- Other Environmental Engineering (hsv//eng)

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