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Mining Publication: Methane Emissions and Airflow Patterns on a Longwall Face: Potential Influences from Longwall Gob Permeability Distributions on a Bleederless Longwall Panel
Keywords: Faces Longwall mining Mine monitoring Ventilation
Original creation date: February 2018
Authors: S Schatzel, R Krog, H Dougherty
Peer Reviewed Journal Article - February 2018
Go to Web Page
NIOSHTIC2 Number: 20054555
Trans Soc Min Metall Explor 2018 Feb; 342:51-61
Longwall face ventilation is an important component of the overall coal mine ventilation system. Increased production rates due to higher-capacity mining equipment tend to also increase methane emission rates from the coal face, which must be diluted by the face ventilation. Increases in panel length, with some mines exceeding 6,100 m (20,000 ft), and panel width provide additional challenges to face ventilation designs.
To assess the effectiveness of current face ventilation practices at a study site, a face monitoring study with continuous monitoring of methane concentrations and automated recording of longwall shearer activity was combined with a tracer gas test on a longwall face. The study was conducted at a U.S. longwall mine operating in a thick, bituminous coal seam and using a U-type, bleederless ventilation system. Multiple gob gas ventholes were located near the longwall face. These boreholes had some unusual design concepts, including a system of manifolds to modify borehole vacuum and flow and completion depths close to the horizon of the mined coalbed that enabled direct communication with the mine atmosphere. The mine operator also had the capacity to inject nitrogen into the longwall gob, which occurred during the monitoring study. The results show that emission rates on the longwall face showed a very limited increase in methane concentrations from headgate to tailgate despite the occurrence of methane delays during monitoring.
Average face air velocities were 3.03 m/s (596 fpm) at shield 57 and 2.20 m/s (433 fpm) at shield 165. The time required for the sulfur hexafluoride (SF6) peak to occur at each monitoring location has been interpreted as being representative of the movement of the tracer slug. The rate of movement of the slug was much slower in reaching the first monitoring location at shield 57 compared with the other face locations. This lower rate of movement, compared with the main face ventilation, is thought to be the product of a flow path within and behind the shields that is moving in the general direction of the headgate to the tailgate. Barometric pressure variations were pronounced over the course of the study and varied on a diurnal basis.
First page of Methane Emissions and Airflow Patterns on a Longwall Face: Potential Influences from Longwall Gob Permeability Distributions on a Bleederless Longwall PanelPeer Reviewed Journal Article - February 2018
Go to Web Page
NIOSHTIC2 Number: 20054555
Trans Soc Min Metall Explor 2018 Feb; 342:51-61
See Also
Field Study of Longwall Coal Mine Ventilation and Bleeder Performance
Investigation into the Practical Use of Belt Air at US Longwall Operations
Mine Face Ventilation: A Comparison of CFD Results Against Benchmark Experiments for the CFD Code Validation
Modeling and Prediction of Ventilation Methane Emissions of U.S. Longwall Mines Using Supervised Artificial Neural Networks
A New Methane Control and Prediction Software Suite for Longwall Mines
Predicting Methane Emissions from Longer Longwall Faces by Analysis of Emission Contributors
Prediction of Longwall Methane Emissions and the Associated Consequences of Increasing Longwall Face Lengths: A Case Study in the Pittsburgh Coalbed
Technology News 465 - Method for Predicting Methane Emissions on Extended Longwall Faces
Using Ultrasonic Anemometers to Evaluate Face Ventilation Conditions
Using Ultrasonic Anemometers to Evaluate Factors Affecting Face Ventilation Effectiveness
Page last reviewed: March 27, 2019
Page last updated: March 27, 2019
Content source: National Institute for Occupational Safety and Health, Mining Program
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