Natural gas storage tank

Thread Content

Storage tanks are important equipment in receiving stations, and their selection must take into account comprehensive factors such as investment, operating costs, and environmental protection. The structural types of storage tanks include spherical tanks, single-volume tanks, double-volume tanks, full-volume tanks, and membrane tanks. The outer tank of a single-volume tank is made of ordinary carbon steel; it cannot withstand low-temperature LNG. The overall layout requires a large safety distance and sufficient area, as well as the installation of fire dikes. The design pressure of single-volume tanks is low, and a fan is required for the return of gas from the ship. However, the investment for single-volume tanks is relatively low. Due to its relatively lower safety compared to other types of tanks, it has been used less frequently in production plants and receiving stations in recent years. A double-tank vessel has an outer tank made of metal material or concrete that can withstand low temperatures; in the event of a leak in the inner cylinder, gas will escape, but liquid will not, making it safer than a single-tank vessel. Generally, a fire dike is not required, but a large safety distance is still needed. Its design pressure is the same as that of a single-volume tank, and a return gas blower is required; its cost is approximately 1.1 times that of a single-volume tank. The structure of the full-volume tank consists of an inner cylinder made of 9% nickel steel, an outer cylinder made of 9% nickel steel or concrete, and a roof. The outer cylinder can withstand the LNG and its gases that leak from the inner cylinder, preventing any leakage, thus making safety protection relatively easy. When a concrete top cover is used, the design pressure can reach 29 kPa (gauge pressure). During unloading, the pressure of the gas inside the tank can be utilized to send the evaporated gas back to the LNG ship, thereby eliminating the need for a blower to transport the evaporated gas and reducing operating costs. A membrane tank uses a stainless steel inner membrane and a concrete outer wall for the storage tank; it has the same performance as a full-volume tank, but it consists of only one cylinder.