Mercury Guard Bed

Mercury Attack on Cryogenic Equipment

Trace mercury in natural gas, condensate, and refinery streams forms amalgams with aluminium that progressively destroy brazed aluminium plate fin heat exchangers in LNG plants, ethylene cold boxes, and cryogenic air separation units. A single point source release of mercury can write off a heat exchanger worth tens of millions of dollars within months. The SorbiTech Mercury Guard Bed is the standard protection: a fixed bed of sulphur impregnated pellet activated carbon captures elemental and ionic mercury as mercury sulphide, holding the outlet below 10 ng/Nm³.

Adsorption Chemistry and Bed Design

Elemental mercury (Hg⁰) physisorbs on the activated carbon micropore structure; the impregnated sulphur reacts with the captured mercury to form mercury sulphide, which is held irreversibly through the bed life. Ionic mercury (Hg²⁺) precipitates directly as sulphide. The bed is single use and sized for the contracted campaign length: typically 3 to 5 years for natural gas service at 1 to 10 µg/Nm³ inlet, shorter for refinery applications with higher inlet loads.

SorbiTech sizes the bed against the contracted inlet, the campaign target, and the operator turnaround schedule.

Spent Media Disposal Under Regulatory Control

Spent mercury guard media is classified as hazardous waste under most regulatory regimes because of the captured mercury content (typically 0.5 to 5 percent by weight at end of life). The SorbiTech changeout service handles the unloading under nitrogen, the certification for transport under the Basel Convention rules, and the licensed disposal route to a thermal mercury recovery facility. Full chain of custody documentation is retained for the operator regulatory reporting.

Where the Bed Fits in the Treatment Train

In LNG feed gas preparation, the mercury guard bed sits between the dehydration unit and the cold box, capturing the mercury that the dehydration sieve does not retain. In refinery service, the bed protects naphtha hydrotreater catalysts and brazed aluminium heat exchangers in the gas plant. In cryogenic air separation, the bed protects the brazed aluminium main exchanger from mercury that can enter via plant air or recycle streams. Applications include natural gas dehydration preparation across the oil and gas sector.

Delivery and Lifecycle Support

Delivered turnkey by SorbiTech or fabricated to client drawings, with SorbiTech maintaining the forward inventory plan that aligns SorbiTech media supply to the operator turnaround calendar. Where the changeout campaign is short and frequent (refinery service), SorbiTech maintains the spent carbon collection programme to the licensed disposal facility on a scheduled service contract.