The asphalt paving industry is the industry that builds the world’s asphalt motorways, airport runways, streets, highways, driveways, parking areas, cycle paths and footpaths and playgrounds and it’s directly associated with the growth of a country.
An asphalt plant is used to blend aggregates, asphalts, and other vital materials in required proportion to produce a homogenous hot mix paving mixture. This hot mix asphalt is usually used for road construction.
Types of Asphalt Plants
There are two types of asphalt plants; batch mix plant and drum mix plant.
Batch mix plants (discontinuous plant) make asphalt in batches. The batch process starts when the aggregates are placed in appropriate containers of the aggregate feeders. A conveyer is then used to transfer the aggregates to the drying drum. The drying drum has flights inside that allow drying to be efficient. Heating and drying of aggregates are done in a rotary drum and heated materials are weighed and divided in hot containers for proportioning before they are mixed with a binder in a different pug mill type mixer to create one batch.
Drum mix plant also known as continuous plants asphalts are made continuously. Unlike in batches, the process of making asphalt in drum plant is continuous. Here the dryer has two purposes, to dry and to mix the aggregates along with bitumen. Drum plant has a higher production rate and is very easy to operate. They are also somewhat cheaper compared to the batch plant.
Regardless of the type of asphalt plant, the main purpose is the same to produce the best quality of asphalt to be used for road construction.
Basic Components of an Asphalt Plant
The basic components of asphalt mix plants are single deck scalping screen, burner, multiple cold aggregate feeder containers, rotary drum, and load out conveyer, single conveyer, fuel service tank, asphalt tank, wet scrubber, control panel and mineral filler unit. These plants can be in a stationery version as well as portable to meet the customer’s preference.
How Does an Asphalt Plant Work?
In asphalt plant, different sizes of aggregates are stored in various feeder bins. Each feeder bin is fitted with gates that are operated manually and belt conveyer driven by adjustable speed motor to predetermine the amount of the aggregates to be discharged from each feeder bin. Aggregates from all the feeder bins are received on a collecting belt which transfers them onto single deck scalping screen to remove the oversize materials. The slinger conveyer is then used to transfer he remaining aggregates (screened aggregates) into a rotary drum. High-pressure jet oil burner dries and heats the aggregate in the primary area of the drum. The heated aggregates are then transferred to the secondary area of the drum (coating area) where they are blended with the pre-metered binders to produce the hot mix asphalt. The load out conveyer is then used to transfer the hot mix asphalt into the storage tower or directly into the tipper. All process of producing the hot mix asphalt is usually monitored and controlled from the control room by a control panel.