Abstract: A method and apparatus are disclosed which reduce smoke emissions in an asphalt drum mixer. A drum mixer heats virgin aggregate to a relatively high temperature in a first drying zone. Virgin asphalt and, in some cases, recycled pavement material containing asphalt, are added in a second zone. Mixing and discharge of the materials occur in a third zone. The invention provides for air or water cooling of the gases in the drum mixer upstream of the point of entry of the asphalt. This cooling reduces the formation of smoke which would otherwise be generated by excessive heating of the asphalt. The apparatus, according to a preferred embodiment, employs an axially positioned air duct, the outlet end of which discharges cooling air into the drum just upstream of the area of entry of the recycled material.

Abstract: An apparatus which monitors and controls the mass flow rates of two or more fuels and air is connected to a burner of a conventional asphalt drum mixer. Several fuels are combined and ignited to produce predictable burner temperatures. In this manner, fuels which ordinarily burn inefficiently can be used in conjunction with other more combustible fuels to produce hot mix asphalt. The regulation of the total fuel to air ratio results in controlled combustion which reduces overheating of the asphalt.