초록 ▼

An inclined counterflow rotating drum mixer has a burner head intermediate an aggregate inlet at one end of the drum and an asphaltic concrete discharge at the opposite end of the drum. A fan supplies secondary air to the burner through a motive tube having an opening in communication with a mixing

An inclined counterflow rotating drum mixer has a burner head intermediate an aggregate inlet at one end of the drum and an asphaltic concrete discharge at the opposite end of the drum. A fan supplies secondary air to the burner through a motive tube having an opening in communication with a mixing chamber between the burner head and the discharge end of the drum to aspirate gases from the mixing chamber for flow through the burner flame. The aspiration creates a negative pressure in the mixing chamber, causing a reverse flow of a portion of the combustion gases from the dryer chamber into the mixing chamber for preheating RAP input to the mixing chamber. RAP is also preheated by providing a preheat chamber adjacent the flame zone but segregated from direct contact with the flame to preheat the RAP. Hot and dried virgin aggregate is mixed with the RAP in the preheat chamber and valves are provided to prevent gases evolved from the RAP in the preheat chamber from flowing into the drying chamber.

대표청구항 ▼

A method for making asphaltic concrete comprising the steps of: introducing aggregate adjacent a first end of a drum mixer for flow in an axial direction toward a second opposite end of said drum mixer; locating a burner head within said drum mixer intermediate said drum ends defining a drying chamb

A method for making asphaltic concrete comprising the steps of: introducing aggregate adjacent a first end of a drum mixer for flow in an axial direction toward a second opposite end of said drum mixer; locating a burner head within said drum mixer intermediate said drum ends defining a drying chamber for the aggregate between said burner head and said first end of said drum mixer and a mixing chamber between said burner head and said second end of said drum mixer; generating hot gases of combustion at said burner head for flow through said drying chamber countercurrently to the flow of aggregate through said drum mixer; establishing a preheating chamber at least in part along said drum between said burner head and said first end of said drum; introducing recycle asphalt material into said preheating chamber; preheating the recycle asphalt material in said preheating chamber; introducing the preheated recycle asphalt material into said mixing chamber; mixing the preheated recycle asphalt material introduced into said mixing chamber and the heated dried aggregate from the drying chamber in said mixing chamber to form the asphaltic concrete; and causing a portion of the hot gases of combustion to flow from said drying chamber into said mixing chamber.