Biofilter Media Gas Pressure Loss as Related to Media Particle Size and Particle Shape

Pressure loss ($\mathrm{\Delta }P$) is a key parameter for estimating biofilter energy consumption. Accurate predictions of $\mathrm{\Delta }P$ as a function of air velocity ($V$) are, therefore, essential to assess energy consumption and minimize operation costs. This paper investigates the combined impact of medium particle size and shape on the $V\text{-}\mathrm{\Delta }P$ relationship. The $V\text{-}\mathrm{\Delta }P$ measurements were performed using three commercially available materials with different particle shapes: crushed granite (very angular particles), gravel (particles of intermediate roundness), and lightweight clay aggregrate (almost spherical particles). A total of 21 different particle-size fractions, with particle sizes ranging from 2 to 14 mm, were considered for each material. As expected, $\mathrm{\Delta }P$ decreased with increasing particle size in agreement with earlier findings. The value of $\mathrm{\Delta }P$, however, also showed a tendency to decrease with increasing particle roundness especially for fractions containing smaller particles. A new model concept for estimating $V\text{-}\mathrm{\Delta }P$ across different particle-size fractions and shapes was proposed. This model yielded improved prediction accuracy in comparison with existing prediction approaches.