Vapor, steam and flash steam / Sludge drying, Slurry drying, Waste drying

Heat source used in drying process of KENKI DRYER is vapor. According to Wiki, vapor is described as “a substance in the gas phase at a temperature lower than its critical temperature”.
Strictly speaking, alcohol vapor is also vapor though, vapor normally suggests water vapor and heat source of KENKI DRYER is also water vapor.

Vapor and steam are different. Vapor is transparent and invisible though, steam is white and visible. Steam appears white since small particles in the air reflects lights irregularly. Gas is invisible since its transparent and colorless, however, seam looks white because of water particles in liquid state. Steam can be said as mixture of gas and liquid.
For example, by watching at spout of kettle with boiling water, it is colorless and transparent around the spout, however, it looks white from some distance away. Around the spouts is vapor/gas though, the vapor tunes into liquid by being cooled in the air and the small water particles look white. This is steam. This steam will evaporate and turn to colorless vapor in gas state in time.
From spouts of kettle of boiling water, vapor comes out then it turns to steam. After that, it evaporates and turns to invisible vapor.

Steam which has been used as heat source of drying becomes liquid drain by releasing its latent heat and being condensed.Since this drain doesn’t have calorific power that the steam used to have, it needs to be discharged immediately. For the discharge, steam trap is used.
Steam trap is an automatic valve to discharge drain as much as possible and prevent steam from leaking.

From steam trap, white steam also comes out together with drain. This steam is called flash steam. The flash steam is generated when high temperature drain under high pressure is released to atmospheric pressure and the drain starts boiling. Under atmospheric pressure, pressure on the drain is decreased and temperature of the drain cannot be kept high in the low pressure, so the temperature of drain is decreased to 100℃ and drain starts boiling. This is called flash steam and discharged together with drain. Its ratio and amount can be calculated.
Also, running cost of boiler which is a steam generating apparatus can be reduced by reusing these drain and flash steam. It is called open type when only drain is collected and called closed type when both drain and flash steam are collected. In this way, they are distinguished each other. Closed type can reduce running cost more since recovered calorific power is more, however, cost of equipment is higher than open type. These types are decided depends on both initial cost and running cost.

Mechanical seam trap

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