|STAR relies on the principles of smouldering combustion of liquid fluids impregnated in porous media. Schematic from Siremlab.|
The model is two dimensional (subsurface slices, vertical and horizontal) and combines a simulator of airflow through the soil with calculations of the propagation of the smouldering combustion front. The propagation component is based on a fire growth simulation, the same principle used in some wildland fire models like FARSITE. The model handles well the most challenging physical scenarios of heterogeneous soil composition and multiple contaminated spots (see second figure below). The results show that air permeability, which affects the movement of the injected air, is a dominant factor for the spread rate and shape of the combustion front.
The model can now be used to optimize STAR and its deployment for specific contaminated sites. For example, to help finding the best location for injectors and igniters, or the most convenient distribution of multiple bore holes (eg, vertical, horizontal, staggered).
Moreover, because the physical principles in the model are fundamental, it can be used to study other large-scale smouldering phenomena of importance like subsurface peat and coal fires.
S MacPhee, G Rein, J Gerhard, A Novel method for simulating smouldering propagation and its application to STAR (Self-sustaining Treatment for Active Remediation), Environmental Modelling & Software (in press), 2011. doi:10.1016/j.envsoft.2011.11.004