Dangerous particulate matter (PM) generated by mining can remain suspended in the air for long periods. So it is very challenging to accurately measure the levels of contaminants in the atmosphere and even harder to predict which direction they go and how far they travel.
Mine owners have a regulatory responsibility to evaluate the content of the atmosphere around every mine, smelting and refining facility and mitigate adverse effects on air quality. Without an accurate and reliable process for detecting on-site dust emissions, the companies can unknowingly violate clean air laws, which potentially results in costly fines, lawsuits and production interruptions. To address the need for continuous monitoring of PM in the atmosphere, Micro Pulse LiDAR (MPL) technology is being tested to determine its usefulness for mining applications.
The ground-based MPL system creates a three-dimensional (3-D) view of the movement of suspended PM that allows any user to track plumes of pollution and better understand air quality in a specified area. Originally developed for NASA satellite missions, the advanced photon-counting technology at the heart of the system is used to detect and track fugitive emission plumes by scanning on a pre-programmed schedule without supervision.
A test project at open-cut coal mines in Australia focused on open path boundary/fence line monitoring using a MiniMPL instrument to track the movement of PM toward nearby municipal areas, as well as contaminants entering the mining area from outside sources. This continuous monitoring across an open pit successfully recorded the dust evolution over time. Results showed that the most dangerous smaller particles stay suspended in the atmosphere much longer than initially thought, which increases the probability of transportation by wind.
The MiniMPL covers a lot of ground with a horizontal scan reaching 100m from the instrument up to 6 km away. Thanks to its space heritage, the MiniMPL unit is robust, small, and lightweight, and the system and laptop are housed inside a specialized weatherproof enclosure. Also notable is its built-in environmental monitoring sensors, regenerating dehumidifier, and uninterruptible power supply, which support autonomous operations in remote areas.
By combining the real-time MPL data with a geographic information system (GIS), the trajectory of emission plumes can be overlaid on a map, allowing the user to pinpoint the origin of the plume and the direction the plume is traveling with a high degree of accuracy. The MiniMPL’s real-time scanning capabilities allow mine operators to better manage on-site dust emissions, reduce unnecessary production stoppages, and improve general air quality in the area. If two co-located instruments with interweaving scan patterns were installed, comprehensive 24/7 coverage could create an effective unsupervised early warning system for adverse events.
The MiniMPL also integrates data from third party instruments, such as weather sensors that collect temperature, relative humidity, wind speed and direction. This is very important for accurately calculating the Planetary Boundary Layer (PBL) and emission flux based on up-to-the-minute local conditions. Traditionally PBL estimates are generated using atmospheric readings taken only twice a day at specific geographic locations, which may be hundreds of miles away. For forecasts to be more useful, fluctuations in the PBL should be frequently monitored with on-site sensors.
The MiniMPL data are a valuable addition to Hexagon’s suite of mining enterprise solutions. Integration of multiple data sources enhances the mining monitoring service and provides a more comprehensive picture to users to improve compliance monitoring, plume detection and early warning systems.
To learn more about using Micro Pulse LiDAR to monitor particulate matter in mining applications, view this interview…