In the early stages of LNG tank development, tanks were all single-walled. They were insulated with block insulation, but lacked a metallic moisture barrier and were susceptible to wind damage. Subsequently, they evolved into double-walled, double-roofed tanks. Due to the ease with which LNG produces vapor, causing overpressure inside the tank, they eventually developed into double-walled, single-roofed tanks.
1. Tank Classification and Brief Introduction
LNG low-temperature storage tanks come in the following types: underground tanks, spherical tanks, single-vessel tanks, double-vessel tanks, full-vessel tanks, membrane tanks, and mother-child tanks. Currently, single-vessel tanks and mother-child tanks are commonly used in liquefied natural gas plants, while underground tanks, full-vessel tanks, and membrane tanks are primarily applied in large-scale LNG receiving stations.
(1) Single-Container
Single-walled and double-walled containers are available, with design pressures ranging from 17-20 kPa and operating pressures typically at 12.5 kPa. For large-diameter single-walled containers, the design pressure is relatively lower, potentially less than 14 kPa. The equipment layout for single-walled containers requires a larger safety distance and land area, and firebreaks and embankments must be set up.
(2) Mother and daughter drums
The mother-child tank is composed of an inner and an outer tank. The inner tank is made up of multiple sub-tanks, which are assembled side by side within a large outer tank. It is a new type of low-temperature storage tank that has developed in recent years. It is suitable for both pressurized and atmospheric storage, with operating pressures ranging from 0.2 to 1.0 MPa, up to a maximum of 1.8 MPa. Like single-vessel tanks, it requires a larger safety distance, occupies more land area, and often features firebreaks and embankments.
(3) Spherical Vessel
The inner and outer shells of the spherical storage tank are spherical in shape. In operation, the inner tank is an internal pressure vessel, and the outer tank is a vacuum external pressure vessel. The volume of the spherical tank typically ranges from 200 to 1500 m³, with operating pressures between 0.2 to 1.0 MPa.
(4) Underground Tanks
An underground storage tank is a tank where the highest liquid level of stored LNG is below ground level, with the tank body resting on an impermeable stable foundation. Underground storage tanks are typically cylindrical metal tanks, with a reinforced concrete outer shell. Due to the high investment and long delivery cycle of underground storage tanks, they are generally not chosen for design.
(5) Full-Container Load (FCL)
The full-volume tank consists of an inner cylinder, outer cylinder, and a top cover, offering a double containment capability for LNG and its vapors. The design pressure of the full-volume tank reaches up to 0.029 MPa, with a design temperature of -196 to 60°C. The friction coefficient for seismic design is generally 0.3 to 0.6, and the distance between the inner and outer cylinders should not exceed 2 meters. Compared to single or double containment tanks, it is the most expensive but also the most reliable in terms of safety. Therefore, its application in receiving stations is extremely widespread.
(6) Membrane Tank
The membrane tank utilizes stainless steel inner membrane and concrete outer tank walls, meeting the same fire prevention and safety distance requirements as full-volume tanks. The membrane tank offers greater operational flexibility compared to full-volume tanks and is more suitable for use in areas with frequent seismic activity and high population density. However, it is characterized by higher investment costs and a longer construction period.
(7) Double-container罐
The double-container design has the same pressure as the single-container design, with both the inner and outer containers capable of independently containing the stored low-temperature liquid products. The outer container is made of low-temperature steel or concrete, while the inner container is made of 9% nickel steel or stainless steel. The distance between the inner and outer containers must not exceed 6 meters.
30, 60, 100 cubic meters LNG storage tanks
30, 60, and 100 cubic meter LNG tanks are commonly used in our production. It's believed that this new type of LNG tank will also be quickly embraced by a wide range of users. Compared to regular tanks, LNG tanks offer enhanced safety. LNG tanks can be categorized by size as: small LNG tanks, ranging from 5 to 30 cubic meters, often used in residential gas vaporization stations and LNG vehicle refueling stations; medium-sized LNG tanks, from 30 to 150 cubic meters, commonly used in satellite liquefaction units, and are the best choice to replace conventional tanks.
The storage system of the LNG tank consists of low-temperature storage tanks, affiliated pipelines, and control instruments, yet it also falls under the category of low-temperature storage tanks.
2. All lng tank piping is made of austenitic stainless steel tubes. Austenitic stainless steel tubes offer excellent low-temperature properties.
3. Available in vertical (lng) storage tanks, these are insulated with vacuum powder insulation technology. The inner tank and pipes are made of Austenitic S30408 stainless steel, while the outer shell is constructed from high-quality carbon steel Q345R steel plates for pressure vessels. These lng storage tanks offer a long service life and are extremely safe to use, having gained widespread recognition.
30, 60, and 100 cubic meter LNG storage tanks, LNG gasification station, and CNG filling station process and equipment selection
