About the condition of steam / sludge drying, slurry drying, recycling drying
About the condition of steam
Condition of steam can be divided into wet steam and superheated steam briefly.
When water is heated under a certain pressure, its temperature stops rising and the water starts boiling. The temperature at this point is called “saturation temperature” and the water at this point has been named as “saturated water”. Steam or water vapor starts being generated at the saturation temperature and the steam is called “saturated steam”.
This temperature in which the steam start being generated has a close relationship with atmospheric pressures or pressures. Generally speaking, the temperature that water starts boiling is 100℃ (212°F) but this figure is under the atmospheric pressure (1 atmosphere = 0.1MPa, 14.3psi), and the boiling temperature or the boiling point changes depending on atmospheric pressures or the pressure given to the water. When water is heated under the pressure higher than the atmospheric pressure, boiling temperature of the water becomes higher than 100℃ (212°F), and water starts boiling with lower temperature than 100℃ (212°F) under the pressure lower than the atmospheric pressure. By using the concrete numbers, boiling point is about 159℃ (70.6°F) when the pressure on the water is 0.5Mpa, 71.4psi (gauge pressure). The water temperature and saturation temperature of saturated water is about 159℃ which is the same as the generated water vapor.
The temperature doesn’t rise for a while after saturated steam starts being generated. However, the temperature starts rising at a specific point. Saturated steam is divided further into “wet saturated steam” and “dry saturated steam” when it distinguished by its characteristics. Even just a little moisture is included in steam, it is called wet saturated steam and called “wet steam” in general. The moisture in the wet saturated steam will all gone by continuing heating and the steam at that point is defined as dry saturated steam. The temperature is settled under a state of the saturated steam even by continuing heating.
By heating the saturated steam further, its temperature starts rising. In other words, the temperature stars rising by adding heat to the saturated steam and the steam is called “superheated steam”. It can be said that the superheated steam is a steam whose temperature is over 100℃(212°F) in the atmospheric pressure.
The states of steam and water vapor changed by heating are in the order of “saturated water” -> “wet saturated steam” -> “dry saturated steam” -> “superheated steam” according to their definitions.