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

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.

Contract Status & Impact

This contract is ongoing. For more information on this contract, send a request to mining@cdc.gov.

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 designed and operated. 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.

In recent years, a series of studies conducted suggests 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 (i) control and direct the airflow to where it is needed and to (ii) plan ventilation systems to integrate with production requirements. Because of the extremely low air-course resistance, a slight change in ventilation driving force, either 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 part 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 increase in 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 - typical contaminants including diesel particulate matter (DPM), diesel equipment exhaust gases, welding fumes, silica dust, and nuisance conditions of fog and inert dust. Among all these contaminants, DPM is the primary air quality concern due to the recent Mine Safety and Health Administration (MSHA) regulations. On May 18, 2006, MSHA promulgated a final rule that changed the interim DPM limit to 350 µg/m3EC (elemental carbon), effective January 20, 2007. On May 20, 2008, the limit was reduced to 160 µg/m3TC (total carbon). 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.

This research will establish a ventilation design process and optimization guidance in order 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
  • study booster fan placement and optimization

This 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 one of our 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, the 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. We will also develop 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 the mine operators to use for their mine ventilation planning and design. The knowledge gained through this project will be unique and transformative because it will provide a new and comprehensive understanding of large-opening mine ventilation behaviors from the thermodynamic principles and with crucial application to improve the effectiveness of ventilation system in large-opening mines.

In order to achieve this project's objective, the following specific aims are defined:

  • Conduct complete mine ventilation surveys for two partner large-opening mines
  • Monitor and record seasonal natural ventilation pressure and strata-to-air energy exchange
  • Quantify the thermodynamic energy of the natural ventilation and strata-to-air heat energy
  • Develop CFD models based on the real geometry of the mine to define the airflow distribution with varying natural ventilation and strata-to-air heat energies
  • Develop CFD modules for booster fan placement design and optimization
  • Develop CFD modules for DPM emission and transport behavior at the mine
  • Establish and finalize guidance for large-opening mine ventilation design and optimization

Page last reviewed: 5/28/2020 Page last updated: 5/28/2020