Soot and SO₂ contribution to the supersites in the MILAGRO campaign from elevated flares in the Tula Refinery

Abstract

Abstract. This work presents a simulation of the plume emitted by flaring activities of the Miguel Hidalgo Refinery in Mexico. The flame of a representative sour gas flare is modeled with a CFD combustion code in order to estimate emission rates of combustion by-products of interest for air-quality: acetylene, ethylene, nitrogen oxides, carbon monoxide, soot and sulfur dioxide. The emission rates of NO2 and SO2 were compared against measurements obtained at Tula as part of MILAGRO field campaign. The rates of soot, VOCs and CO were compared with estimates obtained by IMP. The emission rates of the species considered were further included in WRF-Chem model to simulate the chemical transport of the plume from 22 March to 27 March of 2006. The model presents reliable performance of the resolved meteorology, with respect to the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), vector RMSE and Index of Agreement (IOA). WRF-Chem outputs of SO2 and soot were compared with surface measurements obtained at the three supersites of MILAGRO campaign. The results suggest a contribution of Tula flaring activities to the total SO2 levels of 23% to 37% at the urban supersite (T0), and of 29% to 39% at the suburban supersite (T1). For soot, the model predicts low contribution at the three supersites, with less than 1% at both T0 and T1; and about 1% at T2. According to the model, the greatest contribution of both pollutants to the three supersites occurred on 23 March, which coincides with the third cold surge event.