Astec Inc.’s Double Barrel Dryer/Mixer Ideal for RAP

Fri October 02, 2009 - National Edition
CEG

The double barrel dryer/mixer is a combination aggregate dryer and hot mix asphalt mixer.
The double barrel dryer/mixer is a combination aggregate dryer and hot mix asphalt mixer.



The double barrel dryer/mixer is a combination aggregate dryer and hot mix asphalt mixer with high productivity and low operating costs. The ability of the double barrel drum mixer to run up to 50 percent reclaimed asphalt pavement (RAP) with no added fuel cost makes it especially valuable in today’s market of fluctuating fuel and liquid AC prices, according to the manufacturer.

Clean Operation

The design of the double barrel dryer/mixer allows it to keep RAP and virgin aggregate separate until the mixing phase of production. While the virgin material is dried in the main drum, RAP is injected into the outer mixing chamber. Because the RAP never comes into direct contact with the hot gas stream of the dryer, the double barrel drum mixer produces mixes with up to 50 percent RAP with no more blue smoke emissions than all-virgin mixes.

Energy Efficiency

Because of the double barrel dryer/mixer’s double-drum design, virtually all heat produced by the burner is utilized in the drying and mixing process. Heat used in the superheating process is captured in the outer mixing chamber and utilized in the blending of mix materials.

Mix Quality

When injected into the outer mixing chamber, RAP is heated by virgin aggregate that has been superheated in the inner drying chamber. This method has two benefits: excess moisture is removed from the RAP, and the reclaimed liquid asphalt partially coats the virgin aggregate. The mixing tip design and long mixing chamber of the double barrel drum mixer create a consistent, high-quality product when liquid AC is added, according to the manufacturer.