After many experiments and application examples, it has been proved that the use of titanium tubes in the condensers of power stations has great technical and economic advantages. From an economic point of view, a 1000Mw condenser in Japan in 1983 As an example, according to the quotation of the tube used for nuclear power units (about 50,000 condenser tubes), according to the use time of the condenser is 40 years, aluminum brass tubes have leaked 10 pieces per year, and titanium tubes have not leaked in 40 years. Here are three issues to be dealt with in the application of titanium tubes in power stations:
1. Corrosion problem
The condenser of the coastal power station uses seawater as cooling water. Because seawater contains a lot of sediment, suspended matter, marine life and various corrosive substances. The situation is even more severe in brackish water where seawater and river water change. Traditionally used copper-plated gold tube corrosion methods include: comprehensive corrosion (uniform corrosion), erosion, erosion and stress corrosion. Because titanium has excellent corrosion resistance, the leakage of seawater due to corrosion of titanium tube condensers has been eradicated. However, because of the good corrosion resistance of titanium tubes, unlike copper alloy tubes, a kind of Toxic substances. Therefore, there is simply a sea creature attached to the inner wall of the titanium tube, and then the heat transfer effect is affected, so corresponding cleaning equipment must be provided.
2. Hydrogen absorption problem
Although titanium has a fine passivation film on the surface, it is very resistant to corrosion in many strong corrosive media, but because of its strong affinity for hydrogen. Very simple hydrogen absorption. Onset at normal temperature, high temperature (such as 100 ℃) hydrogen absorption quickly. The melting limit of hydrogen in titanium is very small (approximately 20 ppm), and the hydride (TtH2) will be separated on the titanium surface beyond the quantitative limit. With the increase of TiH2 on the surface, the impact value and elongation of titanium decreased rapidly [4J. In addition. During the transformation of the old unit, because the tube sheet is copper alloy, and the condensing tube uses titanium, this requires the use of cathode maintenance equipment to prevent electrochemical corrosion. When the maintenance potential is lower than -0.75 v (ScE), the titanium tube end of the outlet will absorb hydrogen, and the hydrogen content will reach 650 ppm in one year. 75 v (scE), titanium does not absorb hydrogen at room temperature ”
3. Sensational issue
Because titanium tube has good corrosion resistance. Titanium condenser will not leak and damage due to corrosion. However, the titanium tube may be damaged due to oscillation. To prevent the oscillation of titanium tubes, it is necessary to determine the customary spacer distance when making barrier titanium condensers; when retrofitting old units, it is necessary to examine whether the original spacer distance is suitable for titanium tubes.