Rotary dryer diagram

Triple pass rotary dryer introduction

A set of three rollers of varying diameters, consisting of a multi-ringed roller with an inner and middle ring on the inner and outer surfaces, and an outer ring on the inner surface.

The three layers of drums are rotated at the same number of revolutions and the material direction is as follows: the wet material enters the inner drum, returns to the middle drum from the end, goes to the first end, then to the outer drum, and finally discharges from the end of the outer drum.

Analysis of drying characteristics of the rotary dryer

rotary dryer working principle

Dryness is divided into four sections

AB section: preheating section, the material through the scraper conveyor into the dryer, due to the role of high-temperature hot air makes the material heat up, reaching the wet ball temperature of the hot air, at this time the material moisture barely changes, the hot air temperature is slightly reduced, the heat emitted is mainly used for preheating the material.

BC section: equal speed drying section, the drying rate is constant, there is always a layer of free water on the surface of the material in this section, the heat transferred from the hot air to the material is all used for water vaporization. As a result, the temperature of the surface of the material always remains the same as the temperature of the wet ball of air, the temperature of the hot air and the moisture of the material is rapidly reduced.

CD section: Dry into deceleration section. The internal water diffusion rate of the material is less than the surface water vaporization rate, the material surface does not have enough water, so the drying rate is reduced. 

The heat transferred from the air to the material is greater than the heat consumed by the vaporization of water, so the surface temperature of the material keeps increasing and the air temperature further decreases. If the material temperature reaches the level of insulation, the material temperature will coincide with the hot air temperature.

DE section: for the cooling section, the moisture content of the material has been reduced to the required value, discharged from the dryer, into the cooling system, through the cold air, so that the temperature of the dried material quickly slightly above room temperature, directly bagged and shipped out.

Adopt the following energy-saving measures.
(1) New process for high temperature fast drying
(2) Exhaust gas recycling: i.e., the exhaust gas (about 100°C) is mostly returned to the blending chamber and heated again as a new drying medium.
(3) High efficiency coal-fired hot air furnace
The above measures resulted in a combined heat efficiency of over 76%
(4) The installed capacity of the machine is only one-eighth that of a conventional drum dryer
(5) Automation of the whole machine, saving the operator and thus greatly saving power.

Rotary dryer automatic control

Due to the use of high temperature rapid drying process, the material in the drying system, the flow time is only a few minutes, in order to ensure the quality of drying, when the moisture content of the wet material changes, the corresponding drying parameters must produce changes in line with it. 

This change must be done by an automated control system. In this drying system, our company designed and manufactured a unique control method, first set the water content of the material after drying, in the drying process, regardless of the initial water content of the material and hot air temperature changes, the automatic control system will automatically adjust the corresponding parameters to ensure that the set water content of dry materials.