The purpose of an Asphalt Plant is to blend aggregates, asphalt and other additives in required proportion as per job mix formula and at elevated temperature to produce a homogeneous hot mix paving mixture. This hot mix asphalt is used for road construction.
There are basically two types (based on design) of Plants (1) Batch Mix Plant (Discontinuous type) and (2) Drum Mix Plant.(Continuous type)
In Batch type Plant, drying and heating of aggregates takes place in rotary drum and heated aggregates are weighed & screened in hot bins for proportioning prior to blending with binder in separate pugmill type mixer to make up one batch.
In Drum type Plant the heating, drying and blending of aggregates with the binder takes in the same drum where in feeding of aggregates & binders and output of hot mix asphalt is continuous. This type of plant gives higher production rate and are easy & simple to operate. They are cheaper compared to batch type plant.
Regardless the type of Asphalt Mixing Plant, the basic purpose is the same to produce the quality hot mix asphalt to be used for road construction.
The basic components of Asphalt Drum Mix Plants are Multiple Cold Aggregate Feeder Bins, Single Deck Scalping Screen, Slinger Conveyor, Rotary Drum, Burner, Load out Conveyor, Asphalt Tank, Mineral Filler Unit, Fuel Service Tank, Wet Scrubber and Control Panel with Insulated Control Cabin. These plants can be in mobile (portable) as well as stationary version to meet the customer’s choice.
In Asphalt Drum Mix Plant, different size virgin aggregates are stored in multiple feeder bins. Each bin is fitted with manually operated gates and belt conveyor driven by variable speed motor to preset the proportion of the aggregates to be discharged from each bin. Aggregates from all bins are received on gathering belt which transfer them on to single deck scalping screen for oversize material removal. The screened aggregates are then transferred to rotary drum by slinger conveyor. High pressure jet oil burner fitted at infeed side of the rotary drum dries & heats the aggregate in primary zone of the drum. The heated aggregates then travel to the secondary zone (Coating zone) where they are mixed with the pre metered binders (asphalt & additives) to produce the hot mix asphalt. The hot mix asphalt is transferred to the storage silo or directly into the tipper by load out conveyor fitted with gob hopper. All the operation of the plant is controlled from the control room by control panel.