412
3
Methods
Z. Spirit and M. Hraste
The levels of mercury in natural gas were detected and quantified at the selected
sampling points (inlet to and outlet from the adsorber bed), applying the
mercury analyzer based on fluorescence detection technique (Sir Galahad
instrument, manufactured by PS Analytical) and the "gold film" mercury
analyzer (Jerome 301 Gold Film Mercury Detector).
As to problems related to preservation and storage of field samples containing
mercury, it is recommended to conduct the detection and analysis of activated
carbon mercury content on site, immediately upon unloading, since there is no
need for special preparation prior to sample treatment by means of suitable field
analytical devices. Due to the high mercury content (1-20% w/w), sensitivity is of
minor importance. Therefore, in order to complete the investigation, we have
used the standard Eschka gravimetric procedure (Duschak and Schuette 1925)
that adequately covers the required concentrations, resulting with reliable and
reproducible data under the given circumstances.
However, the determinations of high mercury levels in saturated activated
carbon become difficult due to desensitization of commercially available mercury
analyzers. Namely, the analytical instruments developed recently are capable of
detecting increasingly low levels, along with a high sensitivity for activated
carbon contaminant overload (Bloom 1992). Therefore, for the determination of
total mercury content in the saturated activated carbon, we used graphite furnace
atomic absorption spectrometry (GFAAS), or cold vapour atomic absorption
spectrometry (CYAAS). These procedures and methods are applicable for the
determination of total mercury after the oxygen flask combustion (thermal
decomposition). Such methods are quite suitable, but not for the activated
carbons containing high levels of mercury (not only in the form of HgS), and in
the presence of some aromatic hydrocarbons and readily inflammable compounds, this being the case with condensate present in treated natural gas.
Sulphur content in mercury-saturated activated carbon, as total sulphur, was
detected and measured by the X-ray fluorescence spectroscopy method.
4
Results and Discussion
The sulphur-impregnated activated carbon bed was installed and utilized from
April 1993 till September 1995. [approximately 830 working days, passing a total
amount (0) of 2.26 x 10 9 Nm 3 of the natural gas across the bed]. The mercury
removal efficiency results obtained during this test period clearly indicated good
performance of the sulphur-impregnated activated carbon bed. The natural gas
mercury test analyses indicate typical reduction from inlet average 516 ~lg/m3, to
an average outlet mercury concentration of 0.12 ~lg/m3 (for one of the test time
3
Methods
Z. Spirit and M. Hraste
The levels of mercury in natural gas were detected and quantified at the selected
sampling points (inlet to and outlet from the adsorber bed), applying the
mercury analyzer based on fluorescence detection technique (Sir Galahad
instrument, manufactured by PS Analytical) and the "gold film" mercury
analyzer (Jerome 301 Gold Film Mercury Detector).
As to problems related to preservation and storage of field samples containing
mercury, it is recommended to conduct the detection and analysis of activated
carbon mercury content on site, immediately upon unloading, since there is no
need for special preparation prior to sample treatment by means of suitable field
analytical devices. Due to the high mercury content (1-20% w/w), sensitivity is of
minor importance. Therefore, in order to complete the investigation, we have
used the standard Eschka gravimetric procedure (Duschak and Schuette 1925)
that adequately covers the required concentrations, resulting with reliable and
reproducible data under the given circumstances.
However, the determinations of high mercury levels in saturated activated
carbon become difficult due to desensitization of commercially available mercury
analyzers. Namely, the analytical instruments developed recently are capable of
detecting increasingly low levels, along with a high sensitivity for activated
carbon contaminant overload (Bloom 1992). Therefore, for the determination of
total mercury content in the saturated activated carbon, we used graphite furnace
atomic absorption spectrometry (GFAAS), or cold vapour atomic absorption
spectrometry (CYAAS). These procedures and methods are applicable for the
determination of total mercury after the oxygen flask combustion (thermal
decomposition). Such methods are quite suitable, but not for the activated
carbons containing high levels of mercury (not only in the form of HgS), and in
the presence of some aromatic hydrocarbons and readily inflammable compounds, this being the case with condensate present in treated natural gas.
Sulphur content in mercury-saturated activated carbon, as total sulphur, was
detected and measured by the X-ray fluorescence spectroscopy method.
4
Results and Discussion
The sulphur-impregnated activated carbon bed was installed and utilized from
April 1993 till September 1995. [approximately 830 working days, passing a total
amount (0) of 2.26 x 10 9 Nm 3 of the natural gas across the bed]. The mercury
removal efficiency results obtained during this test period clearly indicated good
performance of the sulphur-impregnated activated carbon bed. The natural gas
mercury test analyses indicate typical reduction from inlet average 516 ~lg/m3, to
an average outlet mercury concentration of 0.12 ~lg/m3 (for one of the test time