LNG 101: Regasification process and terminals

Photo/Courtesy/Petrobras News Agency

The LNG chain ends with the unloading, storage and vaporization of the gas in a regasification terminal.

Liquefied natural gas is received and offloaded from an LNG carrier into storage tanks ranging in capacity from 100,000 to 160,000 cubic meters. These maintain the gas in the liquid state at minus-163° Celsius.

Regasification involves gradually re-warming the liquefied gas until its temperature rises above 0° Celsius. The process takes place at high pressure through a series of evaporators, the most energy-efficient technique when the right water quality is available. In other cases, some of the gas is burned to provide the necessary heat. The gas returns to its original state. In other words, it recovers its gas form and its initial volume, almost 600 times greater.

Evaporators of various output volumes, constructions and heating methods are the basic equipment used in the LNG re-gasification facility. The location, intended use and fuel availability are the main factors considered in selecting the type of evaporators and the LNG re-gasification facility lay-out.

LNG evaporators are divided into the following groups:

•                  Evaporators that heat to a temperature equivalent to the temperature of the surroundings

•                  Evaporators that heat to a temperature higher than the temperature of the surroundings

•                  Evaporators with direct heating.

On its way out of the terminal, the gas is treated as necessary to meet the specifications of regulators and end-users. For example, its heating value can be modified by adjusting the concentrations of nitrogen, butane or propane or by blending with other gases.

The gas is then injected into a gas pipeline connected to a distribution network and, in this way, it reaches the end user, whether household or industrial. 

One hundred LNG regasification terminals are now operating in 21 countries worldwide, nearly 20 more are under construction, and approximately 30 more have been proposed.

The largest receiving and regasification terminal in the world is the Sabine Pass LNG terminal in Cameron Parish, La. The terminal is spread over an 853-acre site. The terminal is owned and operated by Cheniere Energy. 

The Federal Energy Regulatory Commission, or FERC, approved the project in December 2004. Ground breaking for phase 1 of the terminal took place in March 2005. This phase came on stream in April 2008.

The facility can handle 400 LNG vessels a year and features two unloading docks and four dedicated tugs.

A major development in the LNG industry has been floating regasification and liquefaction terminals. The first Floating Storage and Regasification Unit, or FSRU, was the Golar Spirit, which began operating in Brazil in January 2009.

A regasification vessel is an LNG carrier with LNG vaporizers onboard. Depending on the port location, availability of storage, total transport distance and volumes, the regasification vessel can be stationary and receive cargos from conventional LNG carriers. It can also be a shuttle vessel that picks up its own cargo and goes to the receiving location and regassifies the cargo. Initially, there was a clear distinction between a stationary vessel and the shuttle vessels. Today, users prefer flexible vessels that can act in both modes of operation.

Vessels used primarily in stationary mode may either be moored dockside, then natural gas is discharged via a high line; or the vessel may be moored offshore. If moored offshore, the natural gas will be discharged from the vessel through a mooring and unloading buoy. A regasification vessel may be a conversion of a standard LNG carrier or a completely new vessel. For a conversion project it will typically take two years from construction to operation.  A new vessel project can have a lead-time of about three years, depending on yard availability.

According to Hoegh, LNG, a Norwegian company that owns and operates two floating regasification vessels, there are many benefits with floating vessels. The lead time and investment is smaller than for a land-based terminal. The lead time for an offshore terminal is in the range of three years, while the land-based terminal may be in the range of four years.

For small to medium LNG volumes it is also more economical as the investment costs are moderate compared to a land-based terminal. A land based terminal will require space and access to harbors and traffic lanes that may be congested and provide an obstacle for the LNG carriers. An offshore based terminal can be located away from major shipping lanes and will only require a small area onshore for conditioning of gas before connecting to the gas distribution network.

Finally, a floating regas solution is also very flexible as the vessel can be relocated or used as a conventional LNG carrier and operate in any market.

In our next edition we will provide an overview of LNG terminals – both operating and those under construction. 

This is the fifth in a 10-part series produced by the Alaska Support Industry Alliance to educate the public about liquefied natural gas.


11/07/2013 - 9:33am