Simulation and validation of hydrogen sulfide removal from fan ventilated confined-space manure storages

Confined-space manure storage entry is a major safety concern in the agricultural industry. Oxygen-deficient atmospheres as well as toxic and/or explosive gases (i.e., NH ₃, H ₂S, CH ₄, and CO ₂) often result from fermentation and accumulation of the stored manure in confined areas. These gases may create very hazardous conditions to farm workers who may need to enter these confined-space manure storages to work or perform maintenance. Hydrogen sulfide (H ₂S), a highly toxic and irritating gas, was used as a tracer gas to investigate the effectiveness of forced ventilation strategies for eliminating the toxic and oxygen deficient atmospheres in confined-space manure storages. Validated Computational Fluid Dynamics (CFD) modeling protocols were used to simulate H2S evacuation from fan ventilated confined-space manure storages. The simulation studies were conducted for rectangular and round confined-space manure storages and the effects of pollutant source, inter-contamination, storage size (i.e., length, diameter), and air exchange rate on H ₂S removal from fan ventilated confined-space manure storages were investigated. For the same air exchange rate, as the size (i.e., length, diameter) of manure storage increased, the rate of evacuation of the H ₂S from the confined space decreased. For rectangular and round manure storages, the higher the air exchange rate, the higher the rate of evacuation of the H ₂S from the confined space. For the geometries and ventilation system layouts simulated, evacuation times decreased exponentially with air exchange rate for the rectangular tanks. Evacuation times for the round tanks simulated decreased linearly with air exchange rate.