​Large Capacity Cryogenic LNG Storage Tanks: Maximizing Efficiency Through Insulation Design

Large Capacity Cryogenic LNG Storage Tanks: Maximizing Efficiency Through Insulation Design

Cryogenic LNG (Liquefied Natural Gas) storage tanks are critical infrastructure for ensuring a reliable and efficient energy supply.  A key aspect of their design lies in the effectiveness of their insulation.  The primary goal of LNG tank insulation is multifaceted: to meet the stringent demands of the production process, maintain operational efficiency and throughput, minimize the costly loss of LNG through boil-off, conserve energy, prevent condensation from forming on the outer tank surface (which can lead to corrosion and structural issues), and ultimately, create a safer and more comfortable working environment.

Designing the insulation system for these cryogenic tanks requires a deep understanding of the unique thermal properties of cryogenic liquids. Different tank designs and operational conditions necessitate tailored insulation approaches.  This includes considering factors like tank size, operating pressure, ambient temperature variations, and the expected lifespan of the storage facility.

Top-Tier Insulation: Addressing Specific Challenges

The insulation structure at the top of an LNG storage tank presents specific design considerations.  Because the insulation material covers the ceiling of the inner tank, it doesn't need to bear the direct pressure from internal equipment or vaporized gas.  Therefore, the focus is on selecting a material with exceptional low thermal conductivity to minimize heat ingress and boil-off. It is also critical to utilize lightweight insulation to reduce the overall load.

A common approach for the upper section of the inner vessel in a low-temperature natural gas tank involves multiple layers of insulation. For example, a design might incorporate 500mm of cold-insulated glass wool, arranged in multiple layers.  To further enhance insulation performance and protect the glass wool, a layer of aluminum foil is often applied to the top layer.  This foil acts as a radiant barrier, reflecting heat away from the tank, and also prevents perlite, which is often used in the sidewalls, from migrating into the top section. The foil also serves as a barrier, preventing other contaminants from penetrating the interior of the tank.

Sidewall Insulation: Managing Contraction and Preventing Air Ingress

For the intermediate wall layers, foamed perlite is a popular choice for insulation between the inner and outer tank walls. The foamed perlite provides effective insulation and reduces the heat leak from outer shell to the inner vessel.

After the tank is initially filled with cryogenic liquid, the inner tank contracts significantly due to the extreme temperature drop. This contraction can create voids in the expanded perlite insulation, particularly near the top and edge regions of the tank sidewalls. If these voids are left unaddressed, they can lead to increased heat transfer and potentially allow moist air to enter the insulation space.  The presence of moisture can significantly degrade insulation performance and contribute to corrosion.

To mitigate these issues, a flexible insulating fiberglass mat is often applied to the outer wall of the internal storage tank. This mat helps prevent moist air from entering the insulation space, reducing the need for subsequent perlite refills. Additionally, the mat provides a degree of cushioning, reducing the pressure exerted by the perlite on the inner wall of the tank.

Bottom Insulation: Balancing Support and Thermal Performance

The design of the insulation and cold-insulation structure at the bottom of an LNG storage tank is crucial, as it must simultaneously minimize heat gain and provide robust structural support. The insulation must bear the considerable weight of the inner tank, the LNG itself, and the internal gas pressure.

When designing and building a cold storage tank, the bottom insulation structure is divided according to the principle of significantly reducing the various pressures and cooling loss factors at the bottom of the tank: Two parts. , Press ring and center ring and other cold insulation materials. Given these demanding requirements, the bottom insulation typically features a multi-layered and segmented design.

Specifically, the pressure ring is the main element that supports the weight of the inner tank and has relatively high strength requirements, we adopted a composite structure of concrete and glass brick as the cold insulation material for the pressure ring. In the central part of the bottom, the glass brick itself can meet the design requirements for strength and cold resistance. This composite design ensures both structural integrity and minimized heat transfer.

Conclusion

Effective insulation is paramount for the safe and efficient operation of large-capacity cryogenic LNG storage tanks. A carefully considered design, incorporating appropriate materials and construction techniques, is essential to minimize LNG boil-off, conserve energy, and ensure the long-term reliability of these critical energy infrastructure assets. Companies like Henan Jianshen Metal Metenrial Co.Ltd recognize the importance of optimizing resource allocation and are dedicated to providing safe and stable gas resources to the world, upholding the motto that "safe gas use begins at sea and air."