Natural gas is a plentiful energy resource and is the cleanest-burning fossil fuel, making it a clear choice for fulfilling this growing energy need. However, many natural gas resources are in remote locations, and safely transporting the gas by pipeline over long distances is challenging and expensive.

The solution is liquefied natural gas (LNG), a type of natural gas cooled to a liquid state at about -260°F (-160°C). As a liquid, natural gas is about 600 times smaller in volume than in its gaseous state, making it more accessible, more economical and safer to transport natural gas from producing regions to markets by ship.

Because LNG is often transported across state lines and country borders, LNG production is regulated by several federal agencies such as:

• the Federal Energy Regulatory Commission (FERC)
• the U.S. Coast Guard (USCG)
• the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA)
• state utility regulatory agencies

Each of these agencies has its own set of guidelines and regulations that must be followed – and ensuring an LNG facility meets these standards is essential. Regular representative sampling can help LNG plants and natural gas refineries meet these regulations while ensuring equipment, personnel and environmental safety.

A Complicated Process: Extraction to Distribution

The demand for LNG in the United States began in the late 1970s as part of the effort to diversify energy sources in response to the oil crisis. Today’s LNG supply chain consists of four parts: exploration and production; liquefaction, shipping, and regasification; storage; and distribution.

When natural gas is extracted from the ground, it contains impurities and water that can freeze during the LNG cooling process. LNG export facilities receive the natural gas by a pipeline before cleaning the gas and separating it from heavier liquids.

As impurities are stripped out, the natural gas passes through a water-based solvent that absorbs the carbon dioxide and hydrogen sulfide that would freeze and cause blockages when the gas is cooled.
Next, any remaining water is removed, as this would also freeze.

Finally, the lighter natural gas liquids – such as propane and butane – are extracted to be sold separately or used as refrigerants later in the cooling process. Traces of mercury are also filtered out.

The purified natural gas – methane with some ethane – is ready to be liquefied in heat exchangers. A coolant chilled by giant refrigerators absorbs the heat from the natural gas and cools the gas to -162°C. This process turns the natural gas into clear, colorless, non-toxic LNG.

Next, the LNG is loaded into specially insulated tankers outfitted with super-cooled cryogenic tanks and transported worldwide. Once it has reached its destination, the LNG is offloaded from tankers and stored or regasified into its original state for distribution and sale.

During the regasification process, LNG is dehydrated into a gaseous state by passing through a series of vaporizers that reheat fuel above -260°F. Natural gas pipelines then send the natural gas to end-users, including natural gas-fired power plants, industrial facilities, and residential and commercial customers.

Addressing Challenges during LNG Processing

During the LNG production process, facilities first must ensure that impurities have been removed from the gas to meet the appropriate specifications for transport. It’s also critical to remove freezable compounds, such as water, from the gas before cooling and transport.

Before the gas condensation, additional processing is required to remove the threat of crystallization in the heat exchangers in the liquefaction plant.

At every step of the process, representative sampling can ensure that natural gas and LNG are safe and ready for transportation, storage and use by end-users.

Sampling can help facilities:

• Properly maintain heat exchangers during the cooling process
• Ensuring no contaminants or freezing compounds are present before cooling
• Meet transportation requirements

Sentry Equipment helps natural gas refineries and LNG processers maximize product quality and meet environmental regulations. Our experts offer customized advice and solutions to support many LNG applications and sampling cases within one site and or throughout the company.

Contact us at +1-262-567-7256, or complete our online contact form for more information.