Liquefied natural gas is natural gas chilled until it condenses to a liquid, reducing its volume and enabling efficient transportation by ship to markets around the world. The United States has been the world's largest LNG exporter since 2023, with most of its export capacity concentrated along the Gulf Coast. Much of an LNG plant's pretreatment exists to protect its cryogenic section, where even trace amounts of water can form ice or hydrates. Before entering this section, gas must be dried well beyond pipeline specification, and that work falls to a molecular sieve dehydration unit. For many LNG applications, 4A molecular sieve is preferred for its high water adsorption capacity and thermal stability, although there are instances where 3A is recommended. Interra Global supplies molecular sieves for LNG dehydration and offers technical support for the dehydration unit from commissioning throughout its operating life. LNG on the Gulf Coast The Gulf Coast is the largest LNG export hub in the Atlantic Basin, with much of the nation's existing and planned liquefaction capacity concentrated in that region. Southwest Louisiana, from Lake Charles to Cameron Parish, is at the center of this growth, with multiple operating and developing LNG export facilities. New liquefaction capacity brings new dehydration units, while existing facilities replace their molecular sieve periodically over the life of the plant. With engineers located in Texas and Louisiana, home to the majority of U.S. LNG export capacity, Interra Global is positioned to provide responsive technical support to customers across the Gulf Coast. Where Dehydration Sits in the LNG Train An LNG train is one complete processing line that pretreats natural gas and cools it to a liquid state. While the exact configuration varies by facility and process design, LNG pretreatment typically includes:
What Liquefaction Requires of the Dehydration Unit Water that gets past the dehydration unit can freeze into ice and hydrates in the cryogenic section, restricting flow through the heat exchangers, and potentially force an LNG train into an unplanned shutdown. Outlet moisture for cryogenic service is typically specified below 0.1 ppmv. Conventional glycol systems do not typically reach that level, which is why molecular sieve has been the industry standard for this duty since the 1960s. The natural gas dehydration page explains how molecular sieve dehydration works and the factors that influence adsorbent selection. For many LNG applications, 4A molecular sieve is the preferred choice. Its larger pore opening provides higher water adsorption capacity, while its crystal structure offers improved tolerance to repeated hydrothermal cycling. Because acid gas removal typically occurs upstream of dehydration, much of the carbon dioxide and hydrogen sulfide has already been removed before the gas reaches the molecular sieve beds. However, 3A may offer advantages where residual contaminants, hydrocarbon co-adsorption, or regeneration limitations are a concern. Final adsorbent selection should consider feed composition, contaminant levels, regeneration conditions, and overall unit design. Interra Global offers mSORB® 4A-NG and mSORB 3A-NG molecular sieves for this service, each in two bead sizes. Typical properties and packaging are on the product pages. Supporting LNG Dehydration Units Interra Global offers technical support for dehydration units, including reload assistance during bed changeouts, commissioning and start-up support, on-site moisture analysis with breakthrough testing, and spent sample analysis to find the cause of degradation. Support continues throughout the operating life of the unit, including troubleshooting when outlet moisture drifts from specification, engineer and operator training, and recovery support after liquid carryover events, such as amine contamination from the upstream acid gas removal unit. Our technical knowledge comes from years of experience supporting gas processing facilities around the world, and support is available by phone, email, or on site. More details about our technical services can be found on the natural gas dehydration page. Frequently Asked Questions What is LNG pretreatment? LNG pretreatment is the series of processing steps that prepares natural gas for liquefaction by removing the components that would freeze in the cryogenic section or damage its equipment. In a typical LNG train it covers acid gas removal, dehydration, and mercury removal, ahead of the liquefaction section. Why does dehydration come after acid gas removal? Amine treating is a water-based process, so gas leaving the acid gas removal unit is typically saturated with water. Placing the dehydration unit downstream of the amine unit removes this water and deeply dries the treated gas before it enters the cryogenic section, where residual moisture could form ice or hydrates. Which molecular sieve is typically used for LNG dehydration? A 4A molecular sieve is commonly used for LNG dehydration because of its high water adsorption capacity and durability through repeated regeneration cycles. Interra Global supplies mSORB 4A-NG for this service. There are cases where selectivity or limited regeneration heat favors a 3A sieve; the natural gas dehydration page explains that choice. What is an LNG train? An LNG train is one complete processing line that pretreats and liquefies natural gas. Large LNG plants often run several trains side by side, allowing capacity to be developed and expanded in stages. |
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