Modeling of a DBD plasma reactor for porous soil remediation

Abstract

A Dielectric Barrier Discharge (DBD) plasma multiscale simulator has been developed, addressing key mechanisms of soil remediation with characteristic time scales ranging from nanoseconds to minutes in a hierarchical approach. The simulated microscopic DBD plasma processes were linked to the macroscopic remediation modeling through the local species concentrations. A complex, 100 species-based reaction set was implemented in the plasma simulator for the calculation of the concentrations of highly reactive species produced in pertinent operational conditions. These species concentrations were extracted from the microscopic plasma process in the nanoseconds time scale, and introduced as source terms for the solution of the macroscopic problem. In addition, an effective mobility term was introduced to capture the structure effect of the soil medium on the plasma process. The momentum, mass, and energy transport phenomena were modeled and used to predict the degradation rate of atrazine pollutant as a function of specific key reactive molecules, namely, O3 and OH radicals. The activity of these species was examined under different working scenarios, providing valuable information for the remediation process. A wide range of flow rate scenarios were examined, showing that the air velocity influences the remediation process significantly. Another case study involved the application of several sandy soil materials with varying porosity and permeability values, and assessed their impact on the degradation rate. This model analysis was accompanied with experimental data, which were used as reference and validation points for the numerical investigation. Improved operational conditions for the DBD reactor were suggested for the case of atrazine degradation.