Mercury is present in many natural gas streams. While mercury levels can vary greatly, evenlow levels of mercury need to be removed to avoid damage to cryogenic aluminum heat exchangersand other plant equipment.There are two types of mercury removal materials: non-regenerative sorbents and regenerativeadsorbents. With non-regenerative types of mercury sorbents, the process fluid flows through thesorbent bed for a number of years, after which the sorbent is replaced. The mercury is removed fromthe process fluid and stays on the sorbent. The plus side of this approach is its simplicity. The downside is the installation cost, the additional pressure drop, and the disposal cost of the used sorbent.Regenerative mercury removal is usually practiced simultaneously with another regenerativeadsorption application such as drying. By replacing some of the drying adsorbent with a dual functionwater and mercury removal adsorbent, both water and mercury are removed in the dehydrator. Themercury, like the water, is regenerated off the adsorbent leaving with the spent regeneration gas. Theplus side of this approach is no additional equipment cost, no additional pressure drop, and thepossibility of recovering most of the mercury as a separate mercury stream. However, the mercury isnot permanently held on the adsorbent and the spent regeneration gas may require some secondarymercury removal treatment.This paper will evaluate and compare the various mercury removal technologies including thediscussion of a case study where multiple technologies are used at one plant.
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