Geology Reference
In-Depth Information
Figure 9.2.9. Dräger hand pump and tube apparatus used to extract coal-fire gas and measure the concentration of
a select gas component, depending on the tube used. From Stracher et al., 2007, with modifications, permission of
the Geological Society of America.
Figure 9.2.10. The RA-915+ mercury analyzer used for measuring Hg emissions at coal-fire gas vents. This
instrument is a product of Ohio Lumex Co., Inc., 9263 Ravenna Road, Unit A-3, Twinsburg, Ohio 44087, USA.
Hg emissions from gas vents in the Powder River Basin, Wyoming, and the eastern Kentucky coalfield, USA.
According to Kevin Henke of the Center for Applied Energy Research, University of Kentucky, Lexington:
The
instrument is a typical mercury cold vapor atomic absorption spectrometer, which uses a magnetic field (the
Zeeman Effect) to improve the sensitivity of the instrument. Unlike most atomic absorption units, the RA-915+ is
field portable. The RA-915+ has attachments that permit the measurement of mercury in water, air, and solids. Air
samples directly enter into the absorption cell. An ultraviolet beam (wavelength of 253.7 nm) passes through the
cell. Any mercury vapor in the air will absorb some of the ultraviolet radiation. The amount of absorbed radiation is
proportional to the mercury concentration of the air (the Beer
“
Lambert Law). The instrument has a mercury
detection limit in air of about 2 ng/m
3
. The quantification range is about 10
-
100 000 ng/m
3
.
-
”
The pitot tube is useful for measuring the flow velocity of coal-fire gas at a vent (Figure 9.2.11; see
“
WWW
Addresses: Additional Reading
). This instrument uses the fluid density and pressure differential between the static
and stagnation pressures to determine the velocity of a fluid. Although several types of pitot tubes exist, S-type
tubes are ideal for work with coal fires as they are not easily plugged by particulate matter or readily affected by
high temperatures. In addition, they work well at a variety of gas velocities. Pitot tubes are typically used in
”
