Patent ID: 7357562

Claim:
A counter-flow drum mixer asphalt plant for producing asphaltic product from aggregate and liquid asphalt, said asphalt plant comprising: a rotatable cylinder having first and second ends with an internal passageway communicating therebetween and serially providing zones therein from said first end to said second end defined progressively as a drying zone, a combustion zone and first and second stage mixing zones; a support framework carrying said cylinder in a substantially horizontal orientation; a drive motor mounted on said framework and engaged with said cylinder to rotate said cylinder about the central longitudinal axis thereof; a primary aggregate feeder with a material discharge extending within said first end of said cylinder to deliver aggregate material to said drying zone of said cylinder whereby rotation of said cylinder transports said aggregate material progressively through said drying, combustion and first and second stage mixing zones to said second end of said cylinder; a combustion assembly projected into the second end of said cylinder and extending through said first and second stage mixing zones to said combustion zone to generate a hot gas stream in said combustion zone to flow through said combustion and drying zones toward said first end of said cylinder in a countercurrent direction to the flow of aggregate material within said cylinder in order to heat and dry the aggregate material within said combustion and drying zones, said combustion assembly including a burner head positioned at said combustion zone, a fuel supply connected to said burner head, and a primary combustion air supply connected to said burner head to establish a combustion flame within said combustion zone of said cylinder; a liquid asphalt feeder disposed within said first stage mixing zone for delivering liquid asphalt to the hot aggregate carried from the combustion zone into said first stage mixing zone to form an asphaltic composition; a dust feeder disposed within said second stage mixing zone for delivering fine additives to said asphaltic composition carried from said first mixing zone to form a finished asphaltic product; a stationary discharge housing sealingly connected to said second end of said cylinder to permit rotation thereof and having a discharge port for discharging said finished asphaltic product from said cylinder; and a secondary combustion air supply connected to said discharge housing to direct a flow of secondary combustion air to said first stage mixing zone in order to evacuate and carry blue smoke and steam vapors from said first stage mixing zone into said combustion zone and to substantially isolate said second stage mixing zone from the flow of secondary combustion air in order to minimize entrainment of fine additives from said second stage mixing zone.