About drying process
Drying process can be divided into 3 steps briefly.It starts with “drying and preheating period” and moves to “constant rate period”, then “falling rate period” follows them.
First of all, what is “drying and preheating period”?
It suggests a period that drying rate is low while the substance itself is being heated mainly.After the preheating period ends, added heat energy starts being consumed for evaporation of water inside of the substance.Evaporation of water is more intense when temperature of the substance is high, and the amount of heat energy needed for evaporation also increases when the temperature is high.Finally, temperature of substance stays at a certain level since the amount of heat energy added to substance (supplied heat energy) and the heat energy needed for evaporation (consumed heat energy) are balanced.
Drying rate is constant during this period. This is called constant drying rate and this period is called “constant rate period”. This is a period that surface of the substance is being dried mainly.
After the period of drying surface, drying process moves to a phase of drying interior of the substance.It starts that heat energy supplied to the substance is used for raising temperature of the interior, and amount of heat energy used for evaporation becomes only a part of whole energy supplied.Amount of heat energy used for raising temperature increase as heated zone become inner from its surface, and amount of heat energy used for evaporation decrease on the other hand.
This period is called “falling rate period”, and drying rate becomes lower than constant rate period. This period can be said as interior drying period.According to our company’s experience, this period gets shorter and drying rate increases when material is more agitated and more crushed. In case that material is in large solid state, heat is hardly transferred to interior of the substance and drying rate decrease.There are so many difficulties in agitating and crushing sticky sludge during low temperature drying, however, it can be smoothly carried out by using our company’s unique and patented mechanism.Our dryer has a specialty in drying adhesive and sticky materials which is difficult to treat.