LNG storage tanksThe power of French technology

For more than 50 years, the GDF SUEZ Group through its subsidiary GTT has developed the most advanced storage tanks for LNG carriers.

The first attempts to transport LNG in France date back to 1958, when four shipyards conducted research into LNG storage tanks. Two years later, Gaz de France and the research company Méthane Transport contracted these shipyards to develop storage tanks for the experimental ship Le Beauvais, which was inaugurated in 1962. Following the success of this trial, self-contained storage tanks (i.e. tanks that remain separate from the hull and sit on a double bottom) in 9% nickel steel were installed on the future Le Jules Verne ship.

Created in 1965, Gaz Transport signed an agreement with Gaz de France that same year to conduct research into integrated storage tanks, which are better suited than self-contained storage tanks to high-capacity LNG carriers. Featuring ultra-thin insulating walls, these integrated storage tanks fit perfectly into the ship hull and are supported by its structure.

Over the following decades, Gaz Transport and another French company Technigaz developed equipment for many of the world’s LNG carriers. The companies employed various techniques to minimize tank expansion caused by temperature changes. Since the tank is attached to the hull, its dimensions must remain stable. Technigaz developed a ribbing technique to improve the elasticity of the membrane. Gaz Transport opted for a flat metal membrane made from Invar, a 36% nickel steel with an extremely low coefficient of thermal expansion.

In 1994, the two companies merged to increase competitiveness on the international market. The new company Gaz Transport & Technigaz (GTT) quickly proved its merit by developing a new type of membrane in the early 2000s: CS1, a less-costly solution providing improved insulation.

Ninety percent of LNG carriers built around the world use GTT licenses. The French technology of integrated storage tanks has emerged as the international standard.

In 2012, GTT developed a technique to detect defects in storage tank insulation while preventing LNG leaks. The TAMI (Thermal Assessment of Membrane Integrity) method involves injecting nitrogen between the tank’s two insulation barriers. The LNG then cools the nitrogen before it is sent through a second insulation barrier in which it cools the double hull. The process is filmed with an infrared camera to capture cold areas that indicate places in which insulation defects may require repair. Owned by GDF SUEZ, the Matthew LNG carrier was repaired using this method and is now back in service.

Diesel-electric propulsionA major technological breakthrough

LNG carriers have consistently recovered evaporating LNG for use in their propulsion systems but new technological advances have helped develop a more efficient system.

During transport by ship, certain amounts of LNG evaporate naturally. Although this gas is typically recovered and used in the ship’s propulsion system, it does not provide enough energy to power the ship on its own. As a result, an additional energy source is required.

To supply this extra power, several alternative solutions using diesel engines were designed and developed throughout the 1990s.

However, some diesel engines consume heavy fuel oil, which weighs down the ship and reduces the amount of LNG it can carry. Other systems use combined gas and electric turbine engines that involve costly equipment (vacuum condenser), thereby requiring major renovations to the ship.

Of all the alternative solutions available, the diesel-electric motor is the most promising. It helps reduce energy consumption by 30% and emissions by 50%. It can also be adapted to work with any LNG carrier’s speed profile.

Throughout the 2000s, diesel-electric motors started to appear on ships. Gaz de France became the world’s first company to adopt this technology with the ships it commissioned from the Chantiers de l’Atlantique shipyard in 2002. The GDF SUEZ Global Energy carrier featured this type of motor in addition to the latest upgrades made by GTT to its storage tank insulation system, which helped limit evaporation.

Since then, the diesel-electric motor has emerged as the standard propulsion system for all new LNG carriers.

CRIGENOver 50 years of pioneering LNG research

In 1960, five years before the first commercial LNG cargo was delivered to France, the Nantes Roche-Maurice Cryogenic Testing Station, one of the entities that would later form CRIGEN, was created. The station lead trials on every aspect of the LNG process, including its technology and safety. Since then, CRIGEN experts have continued to innovate to support the development of the Group’s LNG value chain.

For over 50 years, numerous studies and trials have focused on LNG.

In 1960, Gaz de France created a cryogenic testing station in Roche-Maurice, near Nantes. Its mission was to demonstrate the feasibility of the LNG value chain. The station included a 500-m3 storage tank (in service until 2002), as well as a liquefaction unit and a regasification unit. In short, a small-scale reproduction of every link in the LNG value chain.

On July 2, 1962, the station received the experimental LNG carrier Le Beauvais, to demonstrate loading and offloading operations, test the different types of storage tanks and study LNG behavior at sea.

To carry out its research and development work, the Nantes Roche-Maurice Cryogenic Testing Station featured all of the following:

  • Two-LNG storage tank facility, with respective capacities of 500 m3 and 250 m3, and a high-pressure regasification unit
  • 120,000 m2 testing ground
  • Workshop for developing trial systems
  • Significant metrology and industrial IT resources
  • Digital modeling tools

Since the 1960s, the station has worked with these resources on challenges connected to various industrial processes including liquefaction, transport and regasification. Its research helped to develop technical materials, to improve safety by studying LNG behavior and to train Gaz de France employees. Gaz de France and Gaz Transport also tested their technique of using integrated storage tanks at Roche-Maurice in 1967.

When the station closed in 2002, it had hosted over a thousand studies and trials, many of which GDF SUEZ conducted in collaboration with international partners

The station generated an immense database, which notably enabled researchers to develop software to improve safety and model LNG behavior during storage or maritime transport (such as EVOLCODE, LNG Master, CARGO, Roll-Over Predictor, LNG Bunkering software, etc.).

Highlights of the Nantes Roche-Maurice Cryogenic Testing Station’s work include:

  • Developing and patenting a liquefaction process known as the Integral Incorporated Cascade (CII) process
  • Helping to develop techniques for building LNG carrier storage tanks with the company GTT
  • Developing various software for studying LNG behavior during transportation and storage (LNG Master, for example, which was validated through tests conducted in the station’s 500-m3 storage tank and through operational observations)
  • Performing qualification tests on materials and processes, by replicating the actual conditions of LNG use and meeting all current standards
  • Working through industrial partnerships to develop LNG supply industries (LNG fuel)
  • Participating in international standards groups and providing technical and training consulting
  • Working with manufacturers to develop innovative systems, notably designed to inspect the inside of storage tanks in service, collect LNG samples and continuously monitor the characteristics of stored LNG
  • Collaborating with other research laboratories to develop and validate safety calculations for engineers and operators
  • Performing large-scale safety trials, notably designed to model:
    • Rapid phase transitions that occur when LNG is discharged into water
    • Spread, vaporization and dispersal of LNG vapor
    • Extent of LNG pool fires

Today, CRIGEN’s LNG researchers are based in Saint-Denis (France) and continue to improve the operational performance of the LNG value chain and to meet new technology challenges related to the GDF SUEZ Group’s development priorities. CRIGEN supports the Group by applying its knowledge of LNG and its thermodynamic properties to develop technologies for LNG fuel and transported LNG. More than ever, research and technology represent a strategic priority in the development of the LNG value chain.

LNG softwareImproving the safety of LNG storage and transport

CRIGEN (Research Center for Natural Gas and New Energies) is one of the Group’s research and technology laboratories dedicated to natural gas activities and new energies. There, researchers develop software and tools for modeling LNG behavior during storage and maritime transport in order to optimize industrial safety at every step in the value chain.

Through computerized tests, models and numerous trials performed at the Nantes Cryogenic Testing Station and at other testing sites, CRIGEN researchers working on LNG have developed software for modeling LNG behavior during storage and maritime transport. These models help optimize facility size and improve the operational and safety management of facilities.

This software notably includes LNG MASTER, which is used to predict the behavior of LNG within storage tanks. This tool improves the operational and safety management of storage tanks at various LNG storage sites (reception terminals, liquefaction plants, peak shaving, etc.). Validated through trials performed on a 500-m3 pilot storage tank in Nantes and through operational data collected at the Montoir-de-Bretagne and Fos-sur-Mer LNG terminals, the latest version of LNG MASTER predicts the following phenomena: LNG aging, mixing, stratification, roll-over, etc.

The CARGO software is used to measure LNG aging during transport by ship, to transmit data on the physical properties and composition of LNG cargo to the destination port, as well as to deliver expertise on LNG behavior and provide advice on complying with quality specifications  during the offloading process.

LNG Bunkering Software assists LNG operators in planning and coordinating bunkering operations between LNG bunkering ships and LNG-powered ships. In particular, the software can model the following operations: loading LNG bunkering ships at the terminal, transporting bunkering ships to LNG-powered ships, bunkering LNG-powered ships.

CRIGEN also provides training and support for all of this software.