Dual drum recycle asphalt drying and mixing method and apparatus

摘要

An asphalt drum drying and mixing plant capable of using recycled pavement aggregate material includes two interacting drums, each being heated to different temperatures. A first drum is a parallel flow drying and mixing drum. The recycled material is introduced at the intake or feed end of this first drum and dried and heated to a comparatively low temperature in a first region of the first drum. A burner of relatively lower heat generation capacity furnishes heated gases. The recycled material is protected by supplying the gases through a cylindrical combustion chamber within which the fuel is completely burned such that no luminous gases enter the drum and contact the recycled material. A second, adjacent region of the parallel flow drum is the mixing region. The recycled material is transferred to the mixing region with close control over the temperature at which the material enters the mixing region. The parallel flow drum also has an intermediate feed chute through which virgin aggregate material is added. The virgin aggregate is heated in a counterflow drum to a temperature higher than the recycled material and the temperature of the final mix is controlled by changing the temperature of the virgin material. The exhaust from the mixing region is introduced as secondary air into the counterflow drum burner assembly. From the counterflow drum all gases are passed to a cleaning system including a cyclone separator and a baghouse filter. From the cyclone separator and the baghouse filter separated material and fines are routed into the mixing region together with liquid asphalt cement.