RAP King^™ Counter-Flow Drum Mixer

Overview | Drum Mixer | Cold-Feed Bins | RAP Bin | Baghouse | Surge Bin & Control House | Photo Gallery

The Drum Mixer

The RAP King^™ drum mixer features a proven design for making hot mix asphalt, including mixes with up to 50% RAP. The design uses a counter-flow aggregate dryer that is surrounded by an outer mixing chamber. Residual heat from the inner drying drum is transferred outward to the mixing chamber, heating its full length.

1. Virgin aggregate enters the dryer by way of a conveyor mounted on the gooseneck of the drum's portable chassis. Aggregate passes into the drum through an opening in the base of the knock-out box.

The knock-out box features an access platform and doorway to allow for inspection and maintenance when the drum is not in operation.

Once inside the drum, aggregate passes through a series of flights that properly veil the rock through a burner flame to remove all moisture.

The standard burner used is a 49.3-million Btu/hour, gas-fired burner. Special low-NOx burners, oil-fired or combination burners are available options.

2. Dry aggregate drops to the outer mixing chamber. When the dry virgin aggregate reaches the burner end of the dryer, it then enters the outer mixing chamber through a series of holes at the end of the drum.

3. RAP is added to the mix through a dedicated RAP inlet to the outer mixing chamber. The RAP inlet chute is mounted near the top of the drum. Oversized RAP that has not already been screened is removed through a special drop-out  chute mounted on the RAP conveyor.

4. Liquid AC is added through an inlet manifold mounted on the side of the drum. The AC is metered with high accuracy and precision by a special two-pump asphalt meter. Mass-flow type meters are also available.

5. Fines are added to the mix through a dedicated inlet on the side of the drum. Fines are captured in the baghouse and are returned to the drum mixer by a series of screw conveyors.

Liquid AC, virgin aggregate, RAP and fines are all mixed together as they travel the length of the mixing chamber. The elongated mixing chamber of the RAP King drum mixer offers longer mix time than parallel-flow mixers of similar length. This proven design produces a better, more homogeneous mix than other drum mixers on the market.

The RAP King's outer mixing chamber features a full-length, hydraulically-opened access door for inspection and maintenance when the drum is not in operation.

6. Hot mix asphalt exits the mixing chamber through an outlet chute on the side of the drum. The outlet chute drops the mix into the base of the plant's drag conveyor.

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