Drum Shells

Drum Shells to Dry and Heat Aggregates and Mix Asphalt

Cold damp aggregates enter the dryer drum through the cold feed housing. Spiral inlet flights, made with abrasion resistant steel, push the cold wet material to the first row of veiling flights. The veiling flights pick the aggregate up one side of the drum and spill the material through the hot gas stream from the burner which heats and dries the aggregate.

If the veil is too thick, the burner’s flame will be choked down, or the baghouse fan will work harder than is necessary. If the veil is too thin, the heat from the burner will pass through to the baghouse, not efficiently transferring heat to the aggregate. 

The area around the burner is called the combustion zone. The burner needs the correct ratio of fuel to air to have efficient combustion. Combustion flights keep the hot aggregate from veiling or crowding the flame in the combustion zone.

If RAP is being used in the asphalt mix, it is generally added after the combustion zone, right at the beginning of the mixing zone. Mixing flights help the hot aggregate transfer heat to the RAP and/or RAS, and get the aggregates, recycle materials, dust, mineral filler, and liquid asphalt blended thoroughly and evenly. The discharge paddles push the hot mixed asphalt out of the mixing drum and into the drag slat conveyor.

Call Chapman Services LLC today.