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Hg-A Applications
Hg-A is designed to remove mercury vapor
from air, hydrogen, natural gas, and other gas streams. Hg-A has proven its
capacity for mercury and ability to achieve less than 0.001 ppbv (approx. 0.01
mg/Nm³) mercury vapor effluent concentrations under dry, 70ºF
conditions. The uniformly sized pellets of Hg-A give a lower pressure drop than
competing spherical or granular absorbents.
Alcoa recommends the Hg-A Bed be located
downstream of dehydration. Water can accumulate over time and adversely effect
the bed capacity and performance. Inlet water dew points less than 10% of
saturation are generally not problematic. Please advise if gas contains
significant water so this can be addressed in the design.
The Hg-A bed should not absorb methanol as
long as the inlet concentration is less than 1000 ppm. If methanol
concentrations exceed 1000 ppm, the bed may absorb several percent by
weight.
Three types of Mercury can be
encountered:
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Free or metallic mercury
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Ionic Mercury
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Organic Mercury
Free or Metallic Mercury is generally of primary concern
since Ionic and Organic do not generally pose corrosion concerns (as in
aluminum heat exchangers). Organic Mercury can be effectively removed with
Hg-A; however this is an absorption rather than chemical reaction, requiring
significantly increased contact times. |
Hg-A Absorbent; Typical:
|
Physical Properties |
| Surface Area, Base Carbon N2BET (ASTM D2854) |
1000 |
m2/gm, minimum |
| Hardness (ASTMD 3802) |
97 |
% |
| Sulfur Content |
14-15 |
weight, % |
| Moisture Content (ASTM D2867) |
3 |
weight, %, maximum |
|
Packed Bulk Density |
34 |
lbs/ft³ (609 kb/m³) |
|
Average Crush Strength per Pellet, 3mm/4mm |
11.7/14.8 |
lbs.
(5.3 kg) / lbs (6.7 kg) |
|
|
Chemical Properties |
| Carbon Tetrachloride Activity, Base Carbon (ASTM D3467) |
60 |
weight %, typical |
| PH
(ATM D 3838) |
6-8 |
|
|
Actual Mercury Capacity to 99% Removal From H2 |
65 |
weight, % |
| Recommended Absorption Contact Time: Vapor <70% RH |
10 |
seconds, minimum |
|
Effluent Mercury Concentration, Dry, 70ºF |
<0.001 |
ppbv
(approx. 0.01 mg/Nmª) |
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Caution: Oxygen is removed
from air by wet activated carbon. Asphyxiation hazard exists inside vessels.
For recommendation on your specific
application, call SME Associates. A complete printout, consisting of design
& pricing specific to your project, can be faxed to you within
hours.
Information presented herein is believed to be
accurate and reliable but does not imply any guarantee or warranty by SME
Associates. Nothing herein shall be construed as an invitation to use processes
covered by patents without arrangements with individuals or companies owning
those patents.
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