Innovative LNG storage solutions are supporting the increased use of LNG as a marine fuel in Scandinavia and the Baltic
Growth in the import of LNG into Scandinavia and the Baltic Sea region has created a seedbed for the development of new small-, mid- and world-scale LNG plants, terminals and bunkering stations, including some flexible and creative LNG storage solutions.
Munich-based Linde AG has had a hand in engineering, designing and building LNG infrastructure across the entire LNG value chain in the Scandinavian and Baltic Sea region for decades. Back in 1996, it began working with Statoil ASA (now Equinor) on the development of the world-scale Snøhvit LNG export plant on the industrial island of Melkøya near Hammerfest, Norway. The plant is designed to operate in arctic conditions and is the only LNG facility in the world to capture and store CO2 from the well stream, reducing its carbon footprint and making it energy efficient.
Situated above the arctic circle, Melkøya receives and processes natural gas from the Snøhvit field in the Barents Sea. The gas is transported via a 168 km gas pipeline to the facility.
Norway’s Snøhvit LNG terminal has two 125,000 m3 LNG storage tanks (image: Bratland/Equinor)
At the onshore facility at Melkøya, condensate, water and CO2 are separated from the well stream before the natural gas is cooled down to LNG and stored in two dedicated tanks.
The two flat-bottomed LNG storage tanks each have a capacity of 125,000 m3, a diameter of 74 m and a height of 48.7 m. The gas processing complex also has a condensate tank, with a capacity of 75,000 m3, diameter of 60 m and height of 42.3 m, and one liquefied petroleum gas (LPG) tank with a capacity of 45,000 m3, diameter of 50 m and height of 37.9 m.
DSI Norway, part of German engineering company Dywidag-Systems International (DSI), was responsible for the supply and installation of the tanks, stressing and grouting a total of 1,650-tonne horizontal and vertical post-tensioning tendons with accessories.
The tank walls were constructed by means of a slip formwork. DSI supervised the installation and position of system components during the concrete works. DSI says a key challenge was the installation of the vertical tendons with 12 strands in the tanks. The vertical tendons of tanks are typical U-shaped or loop tendons. A loop tendon consists of two vertical tendons, which are connected at their bottom ends in the foundation by an 180° arc.
The Melkøya LNG export facility, with a capacity of 4.3 mta, has been operating since 2007. It produces and exports approximately 70 shiploads of LNG every year.
Small-scale storage under pressure
Linde says that unlike the large-scale LNG business, with its downstream LNG distribution chain at atmospheric pressure using LNG carriers, small-scale LNG may require pressurised storage facilities for a number of reasons. One is that economical pressurised storage tanks can be designed for low-storage capacity needs and downstream LNG distribution by either vessel or truck to end consumers.
Linde engineers LNG storage options that include flat-bottom tanks, such as in the case of the Melkøya LNG export facility, spherical tanks – with capacities ranging from 1,000 to 8,000 m³ – and bullet tanks, with capacities of between 100 and 1,000 m³. For small- to mid-scale LNG plants, the storage tank is typically designed to hold a three- to 10-day production volume to have an adequate buffer and flexibility for the downstream supply chain.
“Pressurised bullet tanks offer flexibility, allowing for a modular approach to terminal expansion”
A typical application of a bullet tank is the small-scale LNG import terminal at Agotnes, Norway, which has one 450 m3 pressurised bullet storage tank.
Pressurised bullet tanks also offer flexibility, allowing for a modular approach to terminal expansion. Pori LNG import terminal in Finland, for example, was built with five 1,000 m3 pressurised bullet LNG storage tanks, but could potentially add four more 1,000 m3 LNG storage tanks to its footprint.
At the Halhjem ferry terminal in Norway, Chart Industries supplied two 500 m3 storage tanks to allow ferry operator Fjord1 to bunker its vessels every night. The horizontal storage tanks have the capability to connect to semi-trailers for either bunkering or filling up the storage tanks. The storage tanks connect via a 100-m vacuum insulated piping (VIP) interconnecting pipe underneath the roadway.
Flexibility for expansion
The port of Klaipeda in Lithuania is an LNG hub for the Baltic states. Its infrastructure includes the construction of a single value chain from LNG delivered from the floating storage and regasification unit (FSRU) Independence.
While it does not have the economies of scale of a large LNG terminal, Klaipeda LNG terminal was built in a significantly shorter timeframe and provides operational flexibility. This creates an attractive business model for terminal operators and owners to quickly address the growing demand for LNG as a fuel for transportation and energy and take advantage of new supply.
LNG offloaded and stored at Klaipeda can be loaded onto tanker trucks for virtual pipeline distribution to off-grid users. It is used for truck refuelling, bunkering, as well as vaporised as a source of power generation for local consumers.
“While it does not have the economies of scale of a large LNG terminal, Klaipeda LNG terminal was built in a significantly shorter timeframe and provides operational flexibility”
The cryogenic section of the terminal comprises five identical horizontal vacuum-insulated storage tanks, each with a capacity of 1,000 m3, pre-fabricated by Chart Industries, 10 ambient air vaporisers for gas delivery, loading bays that can simultaneously fill two tanker trucks, four cryogenic submerged pumps for truck filling and bunkering, interconnecting pipework, emergency flare and all associated control and safety systems. The modularised design of the Klaipeda LNG terminal will allow it to double its storage capacity from the current 5,000 m3 to 10,000 m3 if market conditions justify such expansion.
Chart’s horizontal LNG storage tanks can handle storage applications requiring a maximum allowable working pressure of more than 50 psig (3.45 barg). Because pre-fabricated storage tanks are manufactured in a controlled environment, the vacuum technology achieves a higher level of performance as compared with tanks built on site, says Chart.
Development of LNG fuel tanks
With the increasing popularity of LNG as a marine fuel, the most successful design for LNG-fuelled vessels has been vacuum-insulated Type C tanks. A vacuum is maintained in the space between the storage system’s inner and outer tanks to reduce convective heat transfer. Additionally, the space is filled with an absorptive insulating material to reduce the heat transfer.
Cryogenic storage and distribution system manufacturer Inoxcva India supplied two 6.5 m3 fuel tanks to the Dutch firm Cryonorm Systems BV for installation in Europe’s first LNG-powered split hopper dredge, built by Shipyard Constructions Hoogezand Nieuwbouw (SCHN) shipyard in the Netherlands for the Port of Bremen.
One of the largest Type C tanks Inoxcva India has produced was fabricated at its Kandla facility in India. Inoxcva constructed two sets of three 765 m3 LNG marine fuel tanks for TGE Marine Gas Engineering, Bonn, Germany, for installation in Crowley Maritime Corporation’s two 2,400 TEU Container roro (ConRo) ships. The tanks were installed by VT Halter Marine in Pascagoula, Mississippi.
The 34 m tanks have a 6.3 m diameter and weigh 225 metric tonnes. The double-walled, vacuum-insulated Type C tanks have an estimated hold time in excess of 58 days – more than ample for the two LNG-powered ConRo ships that operate in Jones Act service between Jacksonville, Florida, and San Juan, Puerto Rico.
For bunkering storage at the Port of Jacksonville, two 260-metric tonne tanks, each 52 m long were manufactured by Chart Ferox in the Czech Republic.
With an outer diameter of about 6 metres, each tank features an inner shell to hold the product and an outer shell that is insulated and kept under vacuum, to keep the LNG cold.
The tanks are fitted with two internal LNG pumps, each of which can deliver a flow rate of 3,400 litres per minute, with the ability to run multiple pumps for a maximum of 9,100 litres per minutes at peak load rate. Each tank holds enough LNG to fuel the vessels within an eight-hour period.
China’s Gloryholder Liquefied Gas Machinery Co will design and supply the LNG cargo handling and fuel gas supply system for the new 6,000 m3 LNG bunkering vessel being built by Damen Shipyard for Eesti Gaas, Estonia’s leading energy company. The 100 m LNGBV is being built at Damen Yichang Shipyard in China and will have two IMO Type C stainless steel tanks, each with a capacity of 3,000 m3.
LNG storage for fish food plant
Norwegian seafood company Mowi ASA has embraced sustainability as part of its corporate culture. Aquaculture is expected to become an increasingly important source of food to meet the needs of a growing world population. The European Commission’s Joint Research Centre estimates that global average seafood consumption is 22.3 kg per capita, an increase of about 50% since 1980. It comes at a time when wild catch seafood for human consumption is expected to stagnate.
Mowi AS, formerly known as Marine Harvest, wanted to minmise its carbon footprint at its fish food processing plant. An LNG bunkering station at Oksvoll, Norway, was commissioned to support the refuelling of LNG-powered fish farm feeder vessels, serving 40 offshore farms operated by Mowi AS. An integral evaporation plant regasifies LNG to provide a source of natural gas for the nearby fish feed processing facility’s boiler system. The three perlite, vacuum-insulated horizontal LNG storage tanks, each with a capacity of 257 m3, are supplied with LNG by small-scale LNG carrier, but can also unload LNG by truck tankers.
Three tanks have approximately 750 m3 of LNG storage, about two-thirds of which is for LNG bunkering with the remaining capacity supporting the fish feed processing facility’s boiler system.
Both the bunkering and boiler feed sections were designed for low and high operational modes.
Chart engineered and supplied 290 m of VIP of 6-inch inner diameter and 8-inch outer diameter in 12 m sections for optimal transport.
The bunkering station bunkers vessels for a 55-hour roundtrip around the fish farms. Chart says its VIP decreases heat leakage by 90%