Abstract
Increasing productivity stands as a priority in the mining industry, yet this goal comes with increased energy consumption. Additionally, the depletion of shallow-depth sources has compelled mining companies to delve deeper for minerals, necessitating operations at deeper levels. Deep underground mining requires well-designed ventilation systems to ensure a safe and comfortable working environment for miners, particularly in sub-arctic climates where the infrastructure freezing is a concern as well. Mine ventilation, on the other hand, is an energy-intensive process, particularly in mines operating in deep levels located in harsh climates. For instance, a typical mine in Quebec may require approximately 30 MW of refrigeration systems and up to 60 MW for heating. Conventional energy sources, such as propane and diesel, are highly polluting and relatively expensive, rendering the mine ventilation a costly and environmentally unfriendly procedure. Given these challenges, exploring renewable technologies for mine heating and cooling is imperative. Among the suggested alternatives, spray freezing has emerged as a promising solution to provide the heating and cooling needs of mines. In spray freezing, the freezing of water is exploited to heat up the sub-arctic inlet air stream from sub-zero temperatures to above zero. The resulting frozen water can then be utilized for cooling purposes in mine operations. However, successful implementation of spray freezing systems requires a comprehensive understanding of various phenomena, including the droplet freezing and spray dynamics. Also, the so-called supercooling stage during the water freezing impedes the utilization of water latent heat for air heating and therefore should be suppressed. In this presentation, we introduce a multiscale model of spray freezing for mine heating and cooling. This framework encompasses models of droplet freezing and spray dynamics, along with a two-way coupled air-droplet heat transfer model. To ensure the validity of results, the model is validated against the experimental data. Methods to mitigate the supercooling of water is suggested using a nucleation model. Furthermore, we employ a Monte Carlo method in conjunction with multivariate regression analysis to develop user-friendly correlations for estimating the heat rate and cooling capacity of spray freezing systems. The results underscore the remarkable potential of the spray freezing technology for mine ventilation in sub-arctic climates, offering substantial reductions in both pollution and costs. Employing this technology enables the mining industry to enhance its productivity while lowering the carbon footprint.