Counterflow asphalt drum mixer producing less hydrocarbon emissions and

Abstract

A counterflow drum mixer producing less undesirable hydrocarbon gases and capable of more efficiently drying virgin aggregate. The drum mixer has a rotatable drum with first end receiving virgin aggregate and second end removing combined aggregate, reclaimed paving material, and mixed liquid asphalt. A burner projects into the drum from the outlet end and directs hot gases toward the inlet end. A reclaimed asphalt pavement inlet and a liquid asphalt inlet are located within the drum at a point isolated from the hot gases produced by the burner by a burner shield. When the drum mixer is operating, virgin aggregate moves down the drum toward the outlet counterflow to the drying hot gases projected toward the aggregate inlet by the burner. Reclaimed asphalt pavement is entered into the drum at a point behind the burner shield downstream (with respect to the flow of material) from the burner head producing the hot gases and is not exposed directly to those gases. Similarly, the liquid asphalt enters the drum in an inlet downstream of the burner shield, and fines may be mixed with the liquid asphalt at a mixing box. Less hydrocarbons are produced by this apparatus and method because the asphalt contained in the reclaimed asphalt paving material and the liquid asphalt are not directly exposed to radiation or the hot gases coming from the burner. The small amount of hydrocarbons produced are flowed into the burner to be incinerated.