Asphalt Plant Road Construction

Aggregate Heating and Drying

 Aggregate Heating and Drying , Dryers are inclined rotating steel drums ranging in size from 1 m to 3 m in diameter and from 5 m to 16 m in length depending on the capacity of the plant and the moisture content of the materials being handled.

A  dryer  may  not  be  required  in  a  plant  producing  cold  mix  but  it  is  an  essential component of a hot mix plant.

In  a  hot  mix  plant,  the  dryer  performs  two  functions:  it  removes  moisture  from  the aggregate and heats it to the required mix temperature.

Cold aggregate is fed in one end of the dryer and is continually lifted by lifting flights which line the cylinder and dropped in veils through the burning flame and hot gases. The slope of the cylinder, its speed of rotation, diameter, length and arrangement of flights all control the time taken by the aggregate to pass through the dryer.

The  amount  of  aggregate  entering  the  dryer  should  be  such  that  it  can  be  dried  and heated  to  a  temperature  slightly  higher  than  mixing  temperature,  before  passing  out  at  the opposite end of the drum. The hot aggregate is carried to the screen deck by means of a bucket elevator.

A  temperature  control  in  the  exhaust  line  is  generally  used  to  adjust  the  burner  (or burners) to maintain a reasonably uniform temperature in the dried aggregate.

A  check  should  be kept on the temperature of the discharged aggregate at all times to ensure that it is within the specified range  because overheating of the aggregate may result  in damage to the binder by oxidation. This description about aggregate heating and drying will be part of the process of asphalt batch and continuous plants.