Mining Goes Digital – Mueller et al. (Eds)
© 2019 Taylor & Francis Group, London, ISBN 978-0-367-33604-2
636
A sensitive carbon monoxide monitoring system for forecasting
coal spontaneous combustion
Z.W. Wang, Y.F. Li, T.T. Zhang, Y.B. Wei & T.Y. Liu
Laser Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China
ABSTRACT: The coal spontaneous combustion has been recognized as one of the major
hazards in coal mine production. The fiber optic Raman scatter-based Distributed Temperature Sensor (DTS) is an effective approach for coal spontaneous combustion monitoring,
which provides a convenient means to monitor the temperature distribution of coal area over
time. Recently, as the most important characteristic gas, Carbon Monoxide (CO) can be used
for early detection of coal spontaneous combustion in mine goafs. In this work, a sensitive
and stable CO monitoring system was developed by using a Distributed Feedback (DFB)
laser operating at 2.33 μm and a Herriott-type multi-pass gas cell with a 20-m optical length,
taking advantage of the in-situ monitoring, excellent accuracy and simple structure available
from direct absorption spectroscopy. The results obtained have validated the potential use of
such a CO monitoring system in a practical monitoring application, such as the coal spontaneous combustion monitoring.
1 INTRODUCTION
There are a great variety of health and safety hazards in the coal mines, such as water flooding, rock roof collapse, methane gas explosion, and coal mine combustion etc (Liang et al.,
2016). According to the published statistics, the coal mine combustion has been recognized
as one of the major hazards in coal mine production, which can be classified as coal spontaneous combustion and electrical fault (Lieberman and Hewitt, 2004). The coal spontaneous
combustion is due to the slowly oxidized process of coal residue in the goaf. Because of the
highly exothermic oxidized process, the great heat accumulated in turn accelerate the coal
combustion and thus causes fire. So far, the fiber optic Raman scatter-based distributed temperature sensor (DTS) is an effective approach for coal spontaneous combustion monitoring,
which provides a convenient means to monitor the temperature distribution of coal area over
time (Yuan et al., 2012). However, the DTS fiber cable cannot be directly mounted in coal
oxidization zone. Hence, the monitored temperature by the DTS technology is not an actual
temperature of coal oxidization zone.
More recently, multi-gas monitoring technology has attracted more and more attention
to forecasting coal spontaneous combustion (Zhang et al., 2011). The oxidization process
is characterized by presence and increase of many kinds of gases, such as carbon monoxide
(CO) at initial phase of oxidization, ethene (C 2 H 4 ) when the oxidization gets severe, and
ethyne (C 2 H 2 ) where its presence means fire is imminent. By monitoring the concentrations
of each gas within the mixed gases, the early warning signal can be issued before coal spontaneous combustion. Among these characteristic gases, CO is the most important gas for early
detection of coal spontaneous combustion. Typical detection sensitivity of CO present in
goaf area is 1 part per million (ppm) by volume.
Conventional gas analysis system for coal mine combustion monitoring is chromatography-based gas tubing bundles system, which suffers from long time delay due to the longer
distance (10 km or longer) between goaf and the underground gas analysis system (Liu
et al., 2018). As a cutting-edge technology for gas detection, tunable diode laser absorption
© 2019 Taylor & Francis Group, London, ISBN 978-0-367-33604-2
636
A sensitive carbon monoxide monitoring system for forecasting
coal spontaneous combustion
Z.W. Wang, Y.F. Li, T.T. Zhang, Y.B. Wei & T.Y. Liu
Laser Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China
ABSTRACT: The coal spontaneous combustion has been recognized as one of the major
hazards in coal mine production. The fiber optic Raman scatter-based Distributed Temperature Sensor (DTS) is an effective approach for coal spontaneous combustion monitoring,
which provides a convenient means to monitor the temperature distribution of coal area over
time. Recently, as the most important characteristic gas, Carbon Monoxide (CO) can be used
for early detection of coal spontaneous combustion in mine goafs. In this work, a sensitive
and stable CO monitoring system was developed by using a Distributed Feedback (DFB)
laser operating at 2.33 μm and a Herriott-type multi-pass gas cell with a 20-m optical length,
taking advantage of the in-situ monitoring, excellent accuracy and simple structure available
from direct absorption spectroscopy. The results obtained have validated the potential use of
such a CO monitoring system in a practical monitoring application, such as the coal spontaneous combustion monitoring.
1 INTRODUCTION
There are a great variety of health and safety hazards in the coal mines, such as water flooding, rock roof collapse, methane gas explosion, and coal mine combustion etc (Liang et al.,
2016). According to the published statistics, the coal mine combustion has been recognized
as one of the major hazards in coal mine production, which can be classified as coal spontaneous combustion and electrical fault (Lieberman and Hewitt, 2004). The coal spontaneous
combustion is due to the slowly oxidized process of coal residue in the goaf. Because of the
highly exothermic oxidized process, the great heat accumulated in turn accelerate the coal
combustion and thus causes fire. So far, the fiber optic Raman scatter-based distributed temperature sensor (DTS) is an effective approach for coal spontaneous combustion monitoring,
which provides a convenient means to monitor the temperature distribution of coal area over
time (Yuan et al., 2012). However, the DTS fiber cable cannot be directly mounted in coal
oxidization zone. Hence, the monitored temperature by the DTS technology is not an actual
temperature of coal oxidization zone.
More recently, multi-gas monitoring technology has attracted more and more attention
to forecasting coal spontaneous combustion (Zhang et al., 2011). The oxidization process
is characterized by presence and increase of many kinds of gases, such as carbon monoxide
(CO) at initial phase of oxidization, ethene (C 2 H 4 ) when the oxidization gets severe, and
ethyne (C 2 H 2 ) where its presence means fire is imminent. By monitoring the concentrations
of each gas within the mixed gases, the early warning signal can be issued before coal spontaneous combustion. Among these characteristic gases, CO is the most important gas for early
detection of coal spontaneous combustion. Typical detection sensitivity of CO present in
goaf area is 1 part per million (ppm) by volume.
Conventional gas analysis system for coal mine combustion monitoring is chromatography-based gas tubing bundles system, which suffers from long time delay due to the longer
distance (10 km or longer) between goaf and the underground gas analysis system (Liu
et al., 2018). As a cutting-edge technology for gas detection, tunable diode laser absorption