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Home » Asphalt Contractor » December 2006

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RAP Preheating System Provides Economical Solution

The Shelly Company, an asphalt producer with 47 plants located throughout Ohio, puts new RapSaver technology to the test in an effort to economically increase the use of reclaimed asphalt pavement (RAP), while lowering emissions

Recycle usage has become more prevalent, which is forcing producers to search for ways to use recycle at sufficient percentages economically, while minimizing problems associated with RAP, such as blue smoke, and temperature reduction.

With inlet RAP moistures of 5 percent of less, RapSaver has been able to dry RAP to 1 percent moisture and less in a single pass.

recycled material falling from conveyor belt

The RapSaver is a preheating system comprised of a continuously fed sealed conductive heating system that allows cold wet RAP to be heated and dried using a slow moving hollow screw heating auger and heated trough.

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The Shelly Company recently purchased a Wiz Bang crushing plant manufactured by Astec in order to maintain maximum control of material sizing. "We wanted a very uniform product and utilizing the Wiz Bang to pre-crush the RAP before sending it to the RapSaver is ideal," says Protengeier.

The unit size operating at Shelly is a 48-inch-diameter screw at 24-feet long with a heat exchanger firing potential of 9.3 million Btu's. The unit permits as a hot oil heater, and does not produce odors, or particulate emissions.

A portion of the heated air from the exhaust stack of the heat exchanger is ducted, using a variable speed blower fan, into the head space above the rotating auger and provides continuous "heated sweep air" for removal of the moisture as steam to either the atmosphere or back into the inlet of the thermal oxidizer system, which is a component part of the heat exchanger combustion zone, assuring emissions quality at all operating temperatures and capacities.

"We knew when we saw the test at Carrollton that the RapSaver system had the potential to allow us to pre-heat and pre-dry a portion of our RAP feed stream going in to the 450 tph Astec double barrel plant," says Protengeier.

Shelly runs anywhere from 350 to 450 tons per hour depending upon moisture content of virgin and RAP, and range from 25 to 40 percent RAP use again depending upon moisture and mix design specs.

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