The Influence of Climate Change on CO2 and CH4 Concentration Near Closed Shaft – Numerical Simulations

• Published in: Archives of mining sciences = Archiwum górnictwa 2017-09, Vol.62 (3), p.639-652
• Main Author: Wrona, Paweł
• Format: Article
• Language: English
• Subjects: abandoned shaft; Carbon dioxide; CFD; Climate change; Computer simulation; Computer software; Distance; Extreme weather; Fires; Flammability limits; Gas flow; Gases; Greenhouse effect; greenhouse gas emissions; Greenhouse gases; Mathematical models; Methane; mine closure; Mine shafts; Mine ventilation; Mining; Pressure; Pressure drop; public safety; Simulation; underground gas storage; Ventilation; Wind direction
• ISSN: 1689-0469; 0860-7001; 1689-0469
• DOI: 10.1515/amsc-2017-0046

Given the scientific consensus pointing to climate change, the more extreme weather events associated with this will lead to deeper pressure drops. As has already been stated, pressure drops are the main cause of gas flow from underground sites to the surface. This article presents the results of numerical simulations of the change in distribution of CO and CH near a closed mining shaft under the predicted baric tendency. Simulations have been undertaken by means of the FDS software package with the Pyrosim graphical interface – a CFD tool for fire and ventilation analysis. Assumptions have been based on previous results of measurements. The results (determined for a height of 1m above the ground) were compared to the following levels (later in the text comparison levels): for CO 0.1%vol. according to Pettenkoffer’s scale and 2.5%vol. for CH4 as the half of Lower Explosive Limit (LEL). The results show that the deeper baric drops anticipated could lead to a wider spread of both greenhouse gases in the vicinity of the shaft, especially along the prevailing wind direction. According to the results obtained, CO and CH with concentrations above their comparison levels are expected at a distance greater than 50m from the shaft when wind is present for CO and at a distance of 4.5m for CH . Subsequent analysis of the results enabled the determination of functions for describing the concentration of gases along the wind direction line under the projected pressure drop. The results relate to a particular case, although the model could easily be modified to any other example of gas emissions from underground sites.