US 7,581,871 B2 · Counter-flow drum mixer asphalt plant method for two stage mixing

Abstract

A counter-flow drum mixer asphalt plant equipped with a secondary feeder for introducing RAP to direct radiant heat of the combustion zone. Heated virgin aggregate and RAP in the combustion zone are delivered through a transition piece to a first stage of the mixing zone where liquid asphalt is combined with the materials and secondary combustion air flows through the first stage to evacuate blue smoke and steam back to the combustion zone. The second stage of the mixing zone is substantially isolated from secondary combustion air flow where dust and mineral fines are introduced and mixed to complete the asphalt product discharged from the mixing zone. Alternative constructions of the mixing zone are disclosed to provide the first and second stages having such characteristics, as well as options for both the passive and active control of the secondary combustion air. An optional secondary burner in the exhaust housing elevates the temperature of the exhaust gas above its dew point temperature before delivery to the baghouse.

Claims13

Dependent claims

A method for producing asphaltic product from aggregate, RAP, and liquid asphalt, said method comprising the steps of:

introducing aggregate material interiorly of a first end of an inclined, horizontal rotating drum to flow generally from said first end to the second end of said drum and to successively pass through drying, combustion and first and second stage mixing zones of said drum;
generating a hot gas stream within the combustion zone of said drum to flow through the drying zone of said drum to said first end in countercurrent relation to said aggregate material;
adding RAP material directly to the combustion zone of said rotating drum to combine therein with said aggregate material;
delivering said heated and dried aggregate and RAP material to the first stage mixing zone of said rotating drum;
mixing said aggregate and RAP material with liquid asphalt within the first stage mixing zone to form an asphaltic composition.

2 more elements

Dependencies are inferred from the claim text.

Counter-flow drum mixer asphalt plant method for two stage mixing

Life of this patent

Counter-flow drum mixer asphalt plant method for two stage mixing

Life of this patent

Abstract

Claims13