| Confined-space manure storage entry has been identified as a major safety concern in the agricultural industry. Oxygen-deficient atmospheres, as well as toxic and/or explosive gases (e.g., NH3, H2S, CH 4, and CO2), often result from fermentation and accumulation of the manure in confined-space storages. These gases often create very hazardous conditions to farmers who may need to enter these confined-space manure storages to work or perform maintenance. Hydrogen sulfide (H2S), a highly toxic and irritating gas, was the gas of interest to investigate the effectiveness of forced ventilation strategies for eliminating the toxic and oxygen deficient atmospheres in confined-space manure storages.; The overall goal of this research was to develop and validate computational fluid dynamics (CFD) modeling protocols to simulate H2S removal from fan ventilated confined-space manure storages. The CFD model was used to predict the H2S decay and the time (Tpel) to reduce H2S concentrations to the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 10 ppm in a 5.49 m x 2.74 m x 1.83 m rectangular prismatic confined-space manure storage during forced ventilation. Previously identified best ventilation strategies (fan and outlet locations) for confined-space manure storages with three floor cover types (i.e., solid, fully-slotted, and partially-slotted) and experimentally measured H2S emission rates from this study were key CFD model inputs. The CFD-predicted and experimentally measured Tpel values throughout the entire storage were compared to validate the CFD modeling protocols. An extended validation of the CFD modeling protocols was conducted using an independent on-farm confined-space manure pit. The validated CFD modeling protocols were used to study the effect of air exchange rate and manure storage size on H2S removal.; The key findings of this research are: (1) Measured H2S emission rates from stored and agitated manure in forced ventilated manure storage, (2) Validated CFD code and modeling protocols for simulating H2S concentration decay within fan ventilated confined-space manure storages, (3) Identification of relationships between evacuation times (i.e., Tpel) of H2S and air exchange rate for rectangular (non-linear) and circular (nearly linear) confined-space manure storages, (4) Identification of the effect of manure storage length on gas evacuation, and (5) Identification of the effects of gas emission rate from the stored manure and inter-contamination strength in incoming ventilation air on the gas evacuation time from the confined-space manure storages. Based on these findings, a useful simulation protocol was developed to replace measurements of noxious gas concentration decay in fan ventilated confined-space manure storages. These protocols are now available to develop engineering design aids and recommendations for effectively ventilating a wide range of confined-space manure storages. (Abstract shortened by UMI.)... |
