A Duo Drum begins with a counterflow dryer. That’s because you get maximum heat transfer efficiency and a correspondingly low stack temperature with a counterflow dryer. This low stack temperature allows one to superheat the virgin aggregate to allow a higher percentage of recycle to be used. As the superheated virgin material travels toward the burner end, it is blended with recycle material as it passes under the burner. This process allows a positive charging of the mixing drum through t he high lift side discharge. There is no reliance on elongated RAP inlet chutes and there no need to interrupt the integrity of the dryer shell with troublesome RAP inlet ports.

The first section of the rotary mixer is used to allow the superheated virgin material and the RAP material to continue to blend and seek a uniform temperature. Next, the return dust from the baghouse and any fillers are added. Finally, the liquid asphalt and any liquid additives are added without being subjected to temperature extremes. A small fan is supplied to pull of any hydrocarbons and deliver them to a manifold encircling the burner where they are consumed by the intense flame.

This sequential mixing process can only occur in the Duo Drum Design. Single drum systems simply do not allow adequate time and space to efficiently achieve the desired results.