Ask about steam turbine fouling problem

After the steam turbine passage part is scaled, the circulation area of ​​the steam flow will be reduced. If the pressure at all levels is maintained unchanged, the flow rate will be reduced, resulting in a reduction in the power generated by the steam turbine. To keep its power unchanged, the pressure of fresh steam must be increased, which will inevitably cause the pressure drop and enthalpy drop of the scaling stage to increase, resulting in an increase in reaction and axial thrust. ； Fouling will also make the surface of the flow part rough and increase friction loss. If scale forms on the steam valve stem, it will cause jamming, which may lead to a serious accident in the steam turbine.

The main cause of turbine fouling is unqualified feed water and steam quality. The feed water contains a large amount of inorganic salts, and its source is untreated or untreated supplementary water. In medium and low boilers, due to poor steam-water separation effect, inorganic salts are dissolved by wet steam and brought into the turbine by the steam. In addition, the scale deposited in the boiler superheater or steam pipe will also be taken away by the steam when the boiler changes greatly or is started, and accumulates on the nozzles and blades of the steam turbine. In addition, when the boiler is not operating normally, such as steam and water co-evaporation, etc., the steam turbine will have more opportunities for scaling. Therefore, for the problem of steam turbine fouling, we must not only pay attention to the quality of the boiler feed water, but also the way the boiler operates and the structure of the boiler. When the steam turbine is fouled, the pressure in the monitoring section of the unit will generally increase relatively, so it must be removed. The usual removal methods are as follows:: 1. Stop the steam turbine and uncover the cylinder, using mechanical methods (high-pressure cleaning gun). 2. In the cranking state, clean with hot water. 3. Loaded wet steam cleaning. 4. Wash with hot and humid steam at low speed. When using the latter three methods, the cleaning situation must be determined based on the water quality test of the condensate water. The salt content of the condensate water increases at the beginning. After a certain period of time, if the salt content of the condensate water no longer increases, it means that the cleaning work has been completed. The color and shape of the scale can also be used to roughly determine which substances are high in the water. Generally speaking, the causes of scaling are different, and the colors and shapes of scaling are also different. A common type of white scaling will be deposited wherever steam reaches the entire rotor. This scaling is mostly caused by the sodium salts (sodium carbonate, sodium sulfate, sodium chloride, etc.) contained in the supplementary water. There is also a type of scaling. After the steam turbine cover is opened and the cylinder and rotor are exposed to the air, the color will gradually change from colorless to white, because the main component of this scaling is sodium hydroxide, which will turn into sodium carbonate in the air. In addition, in addition to white scale, steam turbine scale also has dark scale. Sometimes you can see scale like rust spots. This scale is mostly a mixture of a large amount of iron oxides and other salts. http://bbs.hcbbs.com/thread-318316-1-1.html 5th floor