We recently posted some information about air analysis in
mine shafts here and here. These discussions reminded me of another series of
gas analysis inquiries that we had from the mining industry.
For literally centuries, the problem of
subterranean coal mine fires has persisted in many areas of the world.
Just to mention a few:
A couple years ago, a coal mine facility in
the southern United States
approached us for assistance with gas analysis. In the initial development and
construction phases, this mine was considered to be a dangerously high risk for
a number of things including fires.
An elaborate system of tubes was built into
the mine. These small tubes connected all areas of the mine to a centralized
monitoring station. The gas atmosphere in any area of the mine can be accessed by
sampling from one of the tubes in the ‘tube bundle’.
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| Example of tube bundle in underground mine. |
Subsequent re-evaluation of the mine’s
hazards lead to a down-grading of the fire risk consideration. However, the
tube system had already been designed and installed. This allowed the mine to
function as a giant research laboratory. Nova’s involvement with the mine began
in this capacity in 2009-2010.
Application #1 – Mine Atmosphere Baseline
Measurement
To evaluate the mine atmosphere at a
somewhat generalized level, a portable analyzer was requested for these three
gases and ranges:
Oxygen: 0 - 25.0%
Carbon Monoxide: 0 – 2,000 PPM
Carbon Dioxide: 0 – 3,000 PPM
For this application, long-term analysis of
tubes in the bundle allowed for establishment of baseline levels in the mine
upon which further research could be done. We provided a special version of the
Model 375K for these measurements.
Even though this is only a portable
instrument intended for temporary ‘spot-check’ type analysis, it has been
running continuously on this experiment for a couple of years now. I think
maybe we have replaced the built-in pump once. Other than that, the mine has
been very impressed with the performance of this little analyzer. They have
since bought one or two more of these units.
The baseline experiment required long-term
analysis of each of the tubes in the mine bundle. So it seemed like a good idea
to provide a reliable way of logging the data into a format that would allow
further evaluation and research. So these versions of the Model 375K were
provided with a 4-20mA analog output for each gas reading. A portable data
logger was also provided. The outputs wrote to the datalogger during analysis.
The data logger has a serial output which can be connected to a computer.
Software on the computer captures the data on the logger.
Application #2 - Testing of Gas Diffusion
through Coal Core Samples
The mine also briefly used the Model 375K
to study a possible dynamic in spontaneous coal combustion. A coal core sample
was set up in the lab with a known atmosphere on one side of the core sample. The
side with the atmosphere, the ‘input’ side, was subjected to 1psig greater than
the output side. The basic idea was that the pressure differential between the
two sides would possibly force the gases through the coal to be released at the
output side.
The analyzer would measure the output side
to help evaluate the rate of gas movement through the coal in this mine. If gas
moved through the coal at a particular rate, perhaps it could be a factor in
the development of coal combustion in certain areas of the mine.
Last I heard, this experiment was abandoned
because the diffusion rate even through a small core sample was insignificant
enough to be eliminated as a source of concern. The research people at the mine
suspected that to begin with, but there were sufficient reasons to run the
experiment at least for a limited time.
Next post will discuss two other
interesting gas analysis applications that came out of this mine facility. Part 2 is here.
For information on these and other gas
analyzer systems, give Mike or Dave at Nova a call, or send us an e-mail.
1-800-295-3771
sales at nova-gas dot com
websales at nova-gas dot com
http://www.nova-gas.com/
