Extensive testing and application examples have fully demonstrated the significant technical and economic advantages of titanium tubes in power plant condensers. From an economic perspective, for example, a 1000MW condenser nuclear power unit in Japan in 1983 required approximately 50,000 condenser tubes, with a design life of 40 years. During this period, aluminum-copper tubes leaked an average of 10 tubes per year, while titanium tubes exhibited virtually no leaks over the 40-year lifespan. However, the practical application of titanium alloy tubes in power plants has not been entirely smooth sailing, and several pressing challenges remain, as follows:
Corrosion Issues
In coastal power plants, seawater is often used as cooling water for condensers. Seawater is rich in sediment, suspended matter, marine organisms, and various corrosive substances. The situation is even more complex and severe in brackish environments where seawater and river water alternate. Traditional copper alloy tubes, exposed to these harsh conditions, are subject to various corrosion mechanisms, including general corrosion (uniform corrosion), erosion, and stress corrosion. Titanium alloy tubes, with their excellent corrosion resistance, effectively prevent seawater leaks caused by condenser corrosion. However, unlike copper alloy tubes, titanium alloy tubes, while corrosion-resistant, are prone to the growth of toxic substances on their surfaces, creating a breeding ground for marine organisms. Large amounts of marine organisms attached to the inner walls of titanium tubes can severely impair heat transfer and, in turn, reduce condenser efficiency. Therefore, power plants using titanium alloy tubes must be equipped with cleaning equipment to regularly remove marine organisms attached to the inner walls.
Hydrogen Absorption Issue
Although titanium forms a dense passivation film on its surface, providing excellent corrosion resistance in many highly corrosive media, titanium has an extremely high affinity for hydrogen and readily absorbs it. This hydrogen absorption occurs at room temperature, but the rate of hydrogen absorption accelerates significantly at high temperatures (e.g., 100°C). The solid solubility limit of hydrogen in titanium is extremely low, approximately 20 ppm. Once this limit is exceeded, hydrides (TiH₂) will precipitate on the titanium surface. As the hydride content on the titanium surface increases, the impact strength and elongation of titanium decrease rapidly, seriously affecting the mechanical properties and service life of titanium tubes.
Furthermore, during the retrofit of older units, if the tubesheets are made of copper alloy and the condenser tubes are made of titanium, cathodic protection is required to prevent electrochemical corrosion. For example, the condensers at Hitachi Power Plants use seawater cooling, with titanium tubes and copper alloy plates used in conjunction. When the protection potential is below 0.75 V (SCE), hydrogen absorption occurs at the outlet end of the titanium tubes, with hydrogen levels reaching 650 ppm after one year of operation. However, when the potential is controlled within the range of 0.5-0.75 V (SCE), titanium does not absorb hydrogen at room temperature.
Vibration Issues
The excellent corrosion resistance of titanium tubes ensures that titanium condensers are protected from corrosion and leakage, but vibration poses another major safety risk. During actual power plant operation, titanium tubes can be damaged by vibration.
To prevent titanium tube vibration, the appropriate baffle spacing must be precisely determined during titanium condenser manufacturing to effectively suppress tube vibration. For retrofit projects involving older units, it's even more important to carefully examine whether the existing partition spacing is suitable for titanium tube use, adjusting it if necessary to ensure the stability and safety of the tubes during operation.
In summary, while titanium alloy tubes offer numerous advantages in power station condenser applications, issues such as corrosion, hydrogen absorption, and vibration still require careful attention. Only by fully understanding and addressing these issues can the advantages of titanium alloy tubes be fully utilized and the operational efficiency and safety of power stations improved.
The company boasts leading domestic titanium processing production lines, including:
German-imported precision titanium tube production line (annual production capacity: 30,000 tons);
Japanese-technology titanium foil rolling line (thinnest to 6μm);
Fully automated titanium rod continuous extrusion line;
Intelligent titanium plate and strip finishing mill;
The MES system enables digital control and management of the entire production process, achieving product dimensional accuracy of ±0.01μm.
