CFD simulation of ozone gas flow for controlling Sitophilus zeamais in rice grains

Abstract

Ozone gas (O3) is a prominent alternative for the integrated pest management of stored products. The present study fitted a computational fluid dynamics (CFD) model to elucidate the ozone gas flow dynamics in an aeration system, at a lethal concentration for Sitophilus zeamais Mots in rice grains. First, an experiment was carried out to understand the flow of ozone gas (2.2 mg L−1; 2 L min−1) in a cylindrical PVC column filled with 4 kg of rice grains. The ozone gas concentration was monitored every 12 h, at a point immediately above the grains. The gas flow was modeled using the CFD technique. The parameters used to feed the model and adjust it to the experimental data were the mass transfer coefficient and ozone-rice grain reaction constant. Then, a simulation of ozone gas injection in a silo with a static capacity of 69.6 tons of rice was performed. In the ozone gas injection experiment, 100% of insect mortality was observed on the sixth day, when the O3 concentration reached 0.1 mg L−1. In this case, the mass transfer coefficient was 0.55 m s−1, and the reaction constant was 0.78 s−1. At the concentration of 0.8 mg L−1, it is possible to treat 69.6 tons of rice grains within 9 days.