The recent mining deaths in Colorado USA
involved two miners who died of carbon monoxide poisoning after they entered an
area of the mine where an explosive had previously been detonated. (link)
We usually think only of the dynamic
physical effects caused by explosions. However, explosions can also create gas
emissions that have some resemblance to combustion atmospheres.
A couple years ago, we were approached by
Queen’s University located in Kingston ,
Ontario , Canada
They were detonating an explosive charge in
a chamber approximately 14m3 (500ft3). The produced atmosphere was pumped to a
monitoring station about 10-20m away.
The atmosphere developed in the chamber was
no doubt a product of the following constituents:
- the products of heat and combustion
- the prevailing atmosphere prior to the
explosion; e.g. O2 content
- the chemistry of the explosive
The gas analysis required was:
0 – 25% O2
0 – 2,000ppm CO
0 – 20,000ppm CO2
0 – 800ppm NO2
0 – 800ppm NO
The CO / CO2 were done by infrared
detectors. The other gases were done by electrochemical sensors.
It is understandable that an explosion
event can be very dusty. In this case, the explosion atmosphere was contained
inside a chamber and the intention was to analyze the gases soon after
detonation. To enable this, a remote probe & heated filter was supplied.
After the explosion, the probe / filter assembly would be mated to the chamber
via a set of bolted flanges similar to the graphic below.
Another option would have been to permanently
mount the probe onto the chamber and install a heavy manual valve in the pipe
between them. After the explosion, the valve could be opened and analysis
begun.
During or after analysis, a supply of
instrument air or N2 could be connected to the filter assembly enable a blow-back
function which sends a blast of high pressure air/N2 back through the probe and filter to push any accumulated dust back out into the chamber.
Connected to the filter system was the
analyzer which had a built-in pump. The pump pulls a gas sample through the
probe and filters and into the detectors for analysis. If the sample tubing
between the chamber and the analyzer runs outdoors in cold weather, the tubing
will require some form of freeze-protection. This will ensure that any
condensation will not freeze up and block flow.
Besides the gases listed above, it was
expected that up to 1000ppm NH3 would develop in the chamber. The analyzer was
therefore designed with NH3-resistant components to prevent corrosion. Up to 5000ppm
CH4 was also expected, but this was not a corrosion concern. We were able to propose
a ppmCH4 detector. However, this did not end up being needed.
If a system like this is of interest to
you, contact Nova for details.
1-800-295-3771
sales at nova-gas dot com
websales at nova-gas dot com
http://www.nova-gas.com/
https://twitter.com/NOVAGAS
http://www.linkedin.com/company/nova-analytical-systems-inc-
http://www.tenovagroup.com/
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