METHOD OF RECIRCULATING USED MIXTURE OF ASPHALT AND AGGREGATES * METHOD OF MIXING ASPHALT AND GRANULAR AGGREGATES UNDER HEATING AND APPARATUS FOR TREATING MIXTURE OF ASPHALT AND AGGREGATES

摘要

In a process for recycling used asphalt-aggregate compositions in a conventional type dryer-mixer drum in which the composition is exposed directly to flame and hot gases of combustion while it cascades along the rotating drum, and in which the flame and hot gases of combustion are directed into an input end of the drum, the improvement comprises separating crushed compositon into a plurality of different portions or increments, each comprising different particle size ranges between coarse and fine particles, introducing the coarse particles into the drum and directly exposing the particles to the flame and/or hot gases of combustion at the input end, and introducing the finer particles downstream from the input end and away from direct exposure to the flame and extremely hot gases in a temperature zone which will avoid overheating and possible burning or coking of the fine particles. The improved apparatus includes means for introducing the coarse particles at the input drum end for direct exposure to the flame or hottest gases and means for introducing the fine particles in a cooler zone of the apparatus.PPIn another embodiment, a burner and combustion chamber incorporating a flame barrier and heat diffuser are utilized to avoid exposing composition to flame and achieve more uniform heating.