Mining Contract: Understanding and Design of Ventilation Systems and Their Optimization for Large Opening Underground Mines

Contract # 75D30119C05743
Start Date 9/1/2019
Research Concept

Large-opening mines account for approximately 60% of the metal/nonmetal mines operating in the United States. The commodities produced from these large-opening mines include limestone for aggregates, lead/zinc, salt, marble, lime, and sandstones. Historically, the ventilation techniques used in large-opening mines have been either experience-based or trial-and-error in relation to design and operation. For large-opening mines, the natural ventilation pressure seasonally changes throughout the year whenever heat transfer occurs between the circulating mine airflow and the rock strata. Booster fans are commonly used to enhance and optimize the ventilation system. However, significant knowledge gaps still exist.

Contract Status & Impact

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In recent years, a series of studies suggest that moving adequate quantities of fresh air in large-opening mines presents several challenges. This is due to the large extent and volume of the mine and the extremely low airflow resistance. Compared to mechanical ventilation in underground coal mines, it is extremely challenging to control and direct the airflow to where it is needed and to plan ventilation systems to integrate with production requirements. Because of the extremely low air-course resistance, even a slight change in ventilation driving force, whether natural or artificial/mechanical, can potentially modify the ventilation profile and air distribution. It is well known that seasonal natural ventilation pressures vary throughout the year and that this variation will significantly influence the ventilation of shallow large-opening mines. However, the manner and intensity of these changes has not been systematically and dynamically analyzed and subsequently codified and incorporated in ventilation planning and optimization.

Additionally, booster fans are commonly used as “active regulators” to assist the through-flow of air in discrete areas of the mine to direct and enhance airflow to different parts of the mine. Because of the low air-course resistance and low frictional pressure drop, improper booster fan installations will result in undesired recirculation and will increase operating costs if the fans act in partial opposition to each other or to the primary ventilation system. Increased mine air recirculation in large-opening mines may result in the accumulation of excessive air contaminants at discrete parts of the mine, with typical contaminants including diesel particulate matter (DPM), diesel equipment exhaust gases, welding fumes, silica dust, and nuisance conditions of fog and inert dust. Among these contaminants, DPM is the primary air quality concern due to Mine Safety and Health Administration (MSHA) regulations. To reduce miners’ exposure to DPM and to meet the MSHA rule, there is a pressing need to improve ventilation design and dynamically optimize the ventilation system as the mine progressively advances. Although booster fan induced recirculation is a well-known phenomenon, the underlying mechanisms of air recirculation and its intensity are not well understood, and a modeling capacity with dedicated tools for booster fan optimization is lacking.

To address these needs, this capacity-building contract will train multiple master's and PhD students in mining engineering with a specialization in large-opening mine ventilation design and establish a ventilation design process and optimization guidance to improve the effectiveness of ventilation systems in large-opening underground mines. Researchers will perform field surveys, observe and model airflow behavior in large-opening mines with consideration of natural ventilation pressure, incorporate thermodynamic effects of strata-to-air energy exchange, and study booster fan placement and optimization.

The overarching objective will be achieved through a series of modeling and field investigations. The airflow distribution behaviors will be surveyed and observed in two partner mines, and all the ventilation parameters and properties will be collected over an extended time period. The seasonal natural ventilation pressure and strata-to-air heat energy exchange will be continuously monitored through an in-field temperature and barometric pressure data collection system. This integrated monitoring system has been developed through a previous Alpha Foundation projects. Thermodynamic analyses will be conducted using the collected field data to quantify the natural ventilation energy intensity for both partner mines by combining both atmospheric temperature gradient and strata-to-air heat energy exchange. Following this, CFD models will be established to analyze the holistic airflow distribution in the mine by coupling the time-dependent natural ventilation energy observed over different seasons and years. The airflow distribution will be quantified through CFD models, avoiding the need for ill-constrained airway resistance information, which is almost impossible to measure for large-opening mines due to the intrinsic momentum of the airflow.

Researchers will also develop a set of CFD modules to define DPM dispersion and transport behaviors at the mine which will be the basis for the overall DPM exposure estimation for the mine workers. Also developed will be regional CFD modules for the booster fan placement design and optimization to achieve best ventilation results at short (days) and medium (month to year) time scales. Finally, a general guidance for mine ventilation design and optimization of large-opening mines will be developed, and the guidance will include a series of CFD modules for mine operators to use for mine ventilation planning and design. The knowledge gained through this research will be unique and transformative because it will provide a new and comprehensive understanding of large-opening mine ventilation behaviors based on thermodynamic principles and with crucial application to improve the effectiveness of ventilation system in large-opening mines.

Page last reviewed: February 28, 2023
Page last updated: February 28, 2023