The World's Largest LNG Onshore Membrane Tank Successfully in Operation
On November 15th, 2023, the first four LNG tanks of the Tianjin Nangang LNG terminal operated by Beijing Gas were filled to 95% capacity. The first two 220,000 m3 LNG membrane tanks, the largest built to date, have officially entered into commercial operation, completing an adventure of nearly four years, including engineering, construction, and commissioning.
Almost four years after the signing of the agreement with Beijing Gas Group Co., Ltd. (BGG) in the presence of French and Chinese Presidents Emmanuel Macron and Xi Jinping, the first two land-based tanks equipped with GTT's GST® technology at Tianjin gas terminal Phase I were successfully commissioned. GTT supported the Chinese construction company China Huanqiu Contracting & Engineering Co. Ltd. (HQC) during the phases of engineering, material supply, construction, inspection, commissioning, and operations.
The success of this first phase has demonstrated the relevance and competitiveness of the membrane solution compared to 9%Ni technology. With the continuous improvement of its supply chain in China, GTT's onshore membrane tank technology will become even more competitive in terms of investment cost, construction schedule, and other economic aspects. As a reminder, the GST® technology is based on the Mark III containment system used in naval applications, and can store 10% more LNG than competing technologies for the same concrete structure. It consists of a corrugated (1.2mm thick) stainless steel primary membrane, installed on insulating panels made of reinforced polyurethane foam and plywood. The principle of the technology is illustrated in the diagram below.
GST® Containment System description
Unlike in naval applications, the secondary barrier in GST® (Ground Supported Tank) technology only extends to a height of five meters, as specified by the code. It is not necessary to have a secondary membrane covering 100% of the tank. The pre-stressed concrete enclosure, with an average thickness of 800 mm, is capable of containing LNG in the event of a significant leakage beyond this limit.
The assembly of the containment system was carried out by an EPC company experienced in the construction of land-based tanks and LNG terminals, but without experience in assembling the Mark III membrane technology. This was an opportunity for GTT to demonstrate its expertise and the know-how of its technical assistance by mobilizing representatives on site to support the EPC contractor and subcontractors, enhance their skills, and ensure quality monitoring during construction.
With an average duration of eight months between the start of the containment system installation and the completion of the membrane tightness tests, the construction schedule of a membrane tank proves to be as competitive as the 9%Ni. GTT's assistance on these tanks was not limited to the installation of the membrane. Indeed, the pre-commissioning, commissioning, and start-up operations were also carried out with the assistance of GTT's commissioning team. This was an opportunity to highlight this aspect of the expertise offered by GTT.
In order to prepare for these crucial steps of cooling down the tanks, GTT's assistance began more than a year before commissioning, through training sessions and the drafting of procedures with the teams of the EPC and the terminal. One month before the start of operations, the final commissioning procedure was validated by the teams in Chinese language to avoid any operational errors. When the first LNG carrier arrived at the terminal, the terminal teams first commissioned the 9% Ni technology tanks. The cooling rate is particularly slow, around 1-2°C/h for this type of structure.
A few days later, the teams began cooling down the GST® tanks, which are not subject to the same constraints thanks to the high flexibility of the GTT membrane. Although regulations allow cooling rates between 10 and 15°C/h for membrane tanks, the teams started slowly and cautiously, before being convinced by the GTT commissioning teams that the technology can indeed support a faster cooling down. In the end, the cooling, achieved by transferring LNG from the 9%Ni tanks, was completed in 32 hours, half the time taken for the 9%Ni tanks.
Ten days after the completion of the cooling down of the first GST® tank, the commissioning of the second began. The cooling of the tank was completed in 27 hours. However, the cooling rate can still be improved, and the terminal teams are willing to further revise the startup procedure for the tanks in phases II and III.
Since then, new ships have arrived to fill the four tanks, which are now almost all at maximum capacity. Both membrane tanks are 95% full and operated smoothly by the operator BGG.
Convinced of the advantages of GST® membrane tanks, the decision was taken to construct the Beijing Gas Tianjin Nangang LNG Terminal Phases II and III, with a total of 6 units of 220,000 m3 membrane tanks (using GTT onshore membrane technology) planned to be fully operational by mid-2024.
