초록 ▼

The counterflow drum mixer includes an elevated virgin aggregate inlet end and an opposite asphaltic product discharge end. A burner lies intermediate the ends and defines a combustion volume. Shield flights surround the combustion volume defining an annular chamber with the drum wall. Recycle mater

The counterflow drum mixer includes an elevated virgin aggregate inlet end and an opposite asphaltic product discharge end. A burner lies intermediate the ends and defines a combustion volume. Shield flights surround the combustion volume defining an annular chamber with the drum wall. Recycle material is supplied to the annular chamber at the upstream end of the combustion volume for heating by convection and conduction in the annular chamber. The virgin aggregate material flows through a drying zone, into the combustion volume and between the shield flights into the annular chamber for contact with and conductive heating of the recycle material. Radiant heat transfer from the combustion volume along radii of the drum to the annular chamber is prevented. Virgin aggregate and recycle material in the annular chamber is prevented from entering the combustion volume by the shape of the shield flights and the rotation of the drum which enables the virgin aggregate in the combustion volume to shield the recycle material from radiant heat. The combined virgin aggregate and recycle material is mixed with liquid asphalt in the mixing zone to form the asphaltic product.

대표청구항 ▼

[ What is claimed is:] [8.] A method for making asphaltic concrete comprising the steps of:introducing aggregate adjacent a first end of a drum mixer for flow toward a second, opposite end of said drum mixer;locating a burner head within said drum mixer intermediate said drum ends and defining a dry

[ What is claimed is:] [8.] A method for making asphaltic concrete comprising the steps of:introducing aggregate adjacent a first end of a drum mixer for flow toward a second, opposite end of said drum mixer;locating a burner head within said drum mixer intermediate said drum ends and defining a drying zone for the aggregate between said burner head and said first end of said drum mixer and a mixing zone between said burner head and said second end of said drum mixer;providing a plurality of flights circumferentially spaced from one another, extending axially towards said first end of said drum from adjacent said burner head and surrounding a combustion volume generated by said burner head, said flights defining a substantially circumferentially continuous annular chamber between said flights and an interior wall portion of said drum mixer and about said combustion volume;generating hot gases of combustion in said combustion volume for flow through said drying zone countercurrently to the flow of aggregate through said drum mixer;flowing the aggregate into the combustion volume onto the flights whereby the aggregate lies radially inwardly of the flights;flowing the aggregate in the combustion volume lying radially inwardly of and on the flights through spaces between said circumferentially spaced flights into said annular chamber; andintroducing recycle asphaltic material into said annular chamber adjacent an upstream end thereof for mixing and lying in heat transfer relation with the aggregate flowing into the annular chamber from said combustion volume through said spaces whereby the recycle material is heated prior to introducing the aggregate and recycle material into the mixing zone.