The use of an asphalt mixing plant is to produce hot mix asphalt. This hot mix asphalt is also known as HMA. It is widely used for road construction. There is a fixed recipe to make hot mix asphalt. It is a combination of aggregates (of different sizes), bitumen and filler material. Aggregates can be single size or a blend of multiple sizes of aggregates.
Different types of hot mix plants are as below:
● Batch type – It produces hot mix asphalt in batches.
● Drum / continuous type – It makes HMA in a continuous process.
Both the types of asphalt mixers have one common thing i.e. to make hot mix asphalt. The method is different but, in the end, it produces HMA. However, the quality of the end product in batch type plants is better compared to continuous (drum) type plants. Batch type plants are more sophisticated and reliable when it comes to producing quality end products. Having said that they are more expensive to own as well as to maintain. On the other end the drum plants require less space to install, less money to buy and operate.
Asphalt drum mix plant operation (working)
Asphalt drum mix plant operation steps start from adding aggregates into the cold aggregate bins. Once we produce the desired quality of hot mix asphalt the operation of drum mixer ends.
The basic principles (steps) of asphalt drum mix plant operation are as below:
- Aggregates have to be fed into the cold feeder bins. These aggregates are fed into separate bins as per their sizes. Bins are synchronized individually for controlled flow of aggregates.
- Aggregates pass through a common single deck vibrating screen. This will help eliminate bigger sized aggregates thus preventing them to enter the drum.
- Charging conveyor will transfer the aggregates into the drying and mixing drum of asphalt plants.
- Charging conveyor is fitted with a load cell for weighing the aggregates collectively before they enter the drying and mixing drum.
- The data received by the load cell is sent to a computerized panel which in turn will control the flow of bitumen and filler material.
- Bitumen is stored in separate tanks which are equipped with a burner. Upon receipt of the data from the control panel, the bitumen tank will allow bitumen addition into the drying drum via a bitumen pump. This bitumen pump is synchronized with the control panel. It is fitted with a variable speed drive motor to control the flow of bitumen.
- Drying and mixing drums is the most important part of the drum mix asphalt plant. Its job is to heat the aggregates evenly and then mix with bitumen and filler material. A Dry drum is an inclined structure – a cylindrical drum. It is fitted with a burner unit at the higher end of the drum. It is this point that the aggregates enter the drum for heating. First half heating will take place and second half mixing with bitumen and filler material will take place.
- Filler material is stored in separate places – in a hopper. This is transferred to the drying drum by means of a compressor. Quantity of the filler material is as per the quantity set in the control panel as the same is matched with the aggregates.
- Once the material is properly mixed in the drum unit, it will be transferred to a conveyor into the waiting trucks. In some plants a hot storage silo can also be equipped for temporary storage of hot mix asphalt.
- Control panel unit is also one of the important components. It is connected with all the components to ensure that the proportion of all the materials is as desired.
Asphalt drum mix plant components
Asphalt drum mix plants have many components, they all work in tandem to ensure that the best quality of hot mix asphalt is produced. The synchronization of all these parts of the drum mixer asphalt plant is important.
Main components of the asphalt drum mix plant are as below:
- Cold aggregate feeder bins
- Slinger / charging conveyor
- Drying and mixing drum
- Bitumen tanks
- Mineral filler unit
- Control panel
A drum mix asphalt plant will usually occupy space of 45-55 sq. m. including space for sufficient storage of raw material and bitumen. Drum plants occupy less space compared to a batch type asphalt plant.
Types of asphalt plants
We can categorise asphalt plants into two types: batch type and continuous types. They can also be categorised into:
- Stationary type
- Mobile type of mixing plants.
Stationary plants are preferred by customers who want to produce continuously at a single place. Stationary plants will be higher in capacity and more suited for long term production at a single place. Mobile plants are preferred for producing medium to small quantities of material at different places. A mobile plant may be stationed at a place and then moved to another site frequently. They will usually be easier to set up and run in quick time compared to a stationary plant.
Asphalt drum mix plants are easy to maintain and own. The real advantage that they have is its smaller size compared to the batch machines. They can be towed easily and set up in a few days. It’s even easy to transport them across continents due to its size. Contact Atlas Industries to learn about how we can help you with buying an asphalt plant.
