Mercury induced corrosion in LNG plants using mixed refrigerant (Fig.1) can be severe on the cycle gas side of exchangers, primarily during warmup periods. The problem can be avoided by removing mercury from the feed and cycle gas liquid. Also, operating conditions during de-riming can be set to avoid or minimize the time during which corrosion can take place.
Mercury removal by sulfur-impregnated activated carbon is the best commercial method for treating the main gas stream, provided the carbon is not blinded by adsorbed hydrocarbon. However, it is not suitable for treating liquids because of solution of the sulfur. Solid beds of iron sulfide, and sodium vanadate in the treating solution in the de-carbonation units, hold promise for mercury removal and merit further investigation.