The following processes are used for mercury removal from the natural gas stream.
This process uses solid adsorbents that remove mercury from gas to produce residuals in the range of 0.01–0.001 µg/Nm3. Calgon sulfur impregnated HGR® (4 x 10 mesh) and HGR®-P (4 mm dia.) carbons are used in this process for the removal of mercury and indicate designs removing mercury down to very low levels. This process is able to remove both, inorganic and organic mercury. The process is more efficient when dry gas is used. The sulfur impregnate reacts with the mercury to produce a mercury sulfide that is fixed in the carbon microstructure.
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Johnson Matthey Catalysts supplies MereSpec fixed bed absorbents for the removal of both, elemental and organic mercury from the hydrocarbon gases and liquids. The absorbents provide the product mercury concentration that is normally recommended for LNG production and is in service in several European locations including an offshore oil/gas production platform. Merespec is a trademark of Synetix.
Desorex HGD2S and HGD4S from Donau Carbon can be employed to bind mercury through the process of chemisorption involving oxidation and adsorption in the form of a stable compound. Many reference installations of these Desorex products for the purification of natural gases to levels as low as 10 ng/m3 of mercury have been realized over a long period of time.
UOP supplies HgSIV adsorbents which are molecular sieves coated with elemental silver. Mercury in the gas is trapped by amalgamation with silver. The adsorbent serves the dual function of dehydrating the gas. HgSIV can be regenerated thermally, just like molecular sieves for dehydration. This material can be added as a layer to existing molecular sieve dryers58. However, regeneration gas must be handled carefully as as it will contain mercury.