Saturation temperature (boiling point) and saturated steam pressure / Sludge drying, Slurry drying,

When water in a container keeps being heated, its temperature rises and start boiling at some point, and the temperature stops rising. This water is called saturated water and the temperature is called saturation temperature or boiling point. Also, this saturation temperature depends on pressure. The pressure is called saturation pressure.
Saturation temperature of water depends on saturation pressure. At 0.1Mpa which is standard atmospheric pressure, saturation temperature (boiling point) is 100℃. However, atmospheric pressure at the top of Mt.Fuji is 0.063Mpa and saturation temperature (boiling point) is 87℃. Saturation temperature becomes lower when pressure is decreased, and it becomes higher when pressure is raised.

When saturated water keeps being heated, water temperature doesn’t rise and water keeps boiling. Steam generated here is called saturated steam. Temperature of saturated water and saturated steam is the same, and steam is generated until all the water is gone by the boiling. Saturation temperature, which is temperature of saturated steam, rises when pressure is increased and the temperature goes down when pressure is decreased. Temperature of saturated steam is 159℃ at 0.5Mpa of pressure.

KENKI DRYER uses saturated steam as a heat source and dries materials with indirect heating. Its heating and drying temperature can be changed by adjusting pressure of saturated steam. The maximum acceptable pressure of saturated steam is 0.7Mpa in KENKI DRYER.Temperature of saturated steam is about 170℃ and internal temperature of the dryer is around 140℃.
Since steam pressure can be changed easily with pressure reducing valves, adjustment of heating and drying temperature is easy.

The following photo is about pressure reducing valve. Steam pressure can be changed easily by turning handle at the top manually to right or left.

Comparison between heat pump type KENKI DRYER and the previous type which uses steam generated by boiler (saturated steam) is the following. Values are not actually proofed values but estimated values.

Heat pump dryers

Even KENKI DRYER uses only saturated steam as its heat source, it is outstanding in safety and hygiene point of view with its unique drying mechanism based on combined use of conductive heat transfer method and heated air method. Since steam is a stable heat source, quality of discharged material after drying is also stable and equable. Maximum allowed steam pressure is 0.7Mpa and adjustment of steam pressure, adjustment of drying temperature in other words, can be easily done. Saturated steam is commonly used in many factories so that it can be said as a familiar and handy heat source. In comparison with drying methods using burner or hot blasts, saturated steam method is an indirect drying applying heat exchange via pipes that steam is passing through, therefore, it hardly burns the materials and is outstanding in safety and hygiene point of view.

Why low-temperature is used for drying? / KENKI DRYER / sludge drying, slurry drying, feed drying

Heat source, Steam