Chevron U.s.a. Inc.

Robert E Marshall, Iv

Saham Sam Tafreshi

Kamal Gursahani

Yawen Q Owen

Disclosed is a system in which saturated mercury adsorbent in a gas mercury removal unit is dehydrated in a LNG, LPG or cryogenic gas plant using a regeneration gas stream. Spent regeneration gas stream is then condensed and the water is removed therefrom to form a renewed regeneration gas stream in a closed loop. The regeneration gas stream is compressed and recycled to a location in the plant upstream of an acid gas removal unit or upstream of a regeneration gas dehydration unit such that the regeneration gas stream is not sent to a flare. A dehydration unit having a pair of dehydration vessels, arranged in parallel, alternating between absorption and regeneration modes, receives gas from the compressor. Conventional plants can be retrofitted to achieve improved process efficiencies, cost savings and environmental benefits.

System for closed loop dehydration of a mercury removal unit

Saturated mercury adsorbent in a gas mercury removal unit is dehydrated in a LNG, LPG or cryogenic gas plant using a regeneration gas stream. Spent regeneration gas stream is then condensed and the water is removed therefrom to form a renewed regeneration gas stream in a closed loop. The regeneration gas stream is compressed and recycled to a location in the plant upstream of an acid gas removal unit or upstream of a regeneration gas dehydration unit such that the regeneration gas stream is not sent to a flare. Conventional plants can be retrofitted to achieve improved process efficiencies, cost savings and environmental benefits.

Systems and methods for closed loop dehydration of a mercury removal unit

Water saturated molecular sieve in a gas dehydration unit is regenerated. A short loop is used in which regeneration gas is recycled to a heater upstream of a vessel in regeneration mode. The regeneration gas passes over the molecular sieve in the vessel to desorb water thereby regenerating the molecular sieve. The short loop also includes a condenser, a water separator and a compressor. The regeneration gas is not recycled to the AGRU at the front-end of the plant, thus the regeneration gas flow rate can be increased, as it is not limited by the front-end capacity of the plant. Moreover, the pressure of the system during regeneration can be reduced within the limits of system hydraulics. By using the short loop, the total time required for regeneration can also be reduced. The embodiments disclosed can de-bottleneck molecular sieve regeneration constraints in LNG, LPG or cryogenic gas plants.

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Houston, TX, United States of America

Robert E Marshall, Iv