Stansteel’s RAP Eater Drum

Asphalt producers wishing to increase percentages of recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS) in their mixes look to their drum and flight configurations for efficiencies. The team at Stansteel and Hotmix Parts, Louisville, Kentucky, developed the RAP Eater™ drum mixer to allow for the use of high recycled material. Here’s how it works:

The combination of a continuous main shell throughout the length of the drum mixer with an outer RAP shell allows 45 seconds or more of in-process blending time, compared to 10 to 25 seconds for conventional drum mixers.

First, heated aggregate exits the main shell into the outer RAP shell at the point where RAP and RAS enter the outer RAP shell from the RAP housing. This process allows for the RAP and RAS to be brought to temperature in two ways.

1. The hot aggregate heats RAP and RAS by convection in the outer RAP shell.
2. RAP and RAS are heated in the outer RAP shell by radiant heat from the burner through stainless steel panels mounted on the main drum shell in the combustion zone of the drum mixer.

The combined process uses heat that would normally be lost through the shell.

Next, the RAP Eater RAP housing design induces RAP and RAS to flow smoothly into and through the drum. Spiral flights inside the RAP housing allow recycle material to feed directly onto the inlet spiral flights of the RAP shell section of the RAP Eater.

The RAP Eater RAP housing will also allow the introduction of either all the dust returned from the baghouse, only the heavy fines from the primary collector, or other materials, if desired, at the RAP housing. Introducing dust at the RAP housing allows dust to mix with the recycle, thus helping to eliminate blockage at the point of recycle entry into and through the drum mixer.

This also allows an increased mixing time of the dust in the drum mixer of an extra 11 feet.

For more information, contact Stansteel at (800) 826-0223 or visit https://stansteel.com/rap-eater-2/.