How an asphalt plant works – this question is asked many times. In this blog post I will try and explain the working of asphalt mixing plant in a simple manner. We also have an easy-to-understand video explaining the working (operation) of asphalt batch mix plant see the video:
The aim of an asphalt mixing plant is to produce hot mix asphalt. It can do so in a batch type process or a continuous process. The plant for producing hot mix in batch process or continuous process are different.
Asphalt plant uses aggregates, sand, bitumen and filler material to produce hot mix asphalt. This is also called as asphalt concrete or blacktop. It is then paved and rolled so that it can be made ready for use. The main purpose of the asphalt mixing plant is to heat up the aggregates and mix them with bitumen and other materials. Heating is done at specific temperature and mixing is for a specific time. This process helps to generate hot mix asphalt. Aggregates used can be one, two or more different sizes depending on the requirement of the job.
Types of asphalt plants – batch and continuous (drum) type
There are primarily two different types of asphalt mixing plants:
- Batch type
- Drum type
There are key differences in the operation (working) method of each of the type of asphalt plant. The process of a drum type plant is much simpler than a batch type of asphalt plant. Batch type employs a more complex process to produce hot mix asphalt. The continuous type plant (drum mix) produces hot mix asphalt in a continuous process. These plants are called as continuous asphalt mixing plant or drum mix asphalt plants. Then we have batch type asphalt plants also known as tower asphalt plants. These plants produce hot mix asphalt in specific batch sizes.
The method of producing the end product in both the type of asphalt machines are different. Even though the end product is the same, the quality of the end product produced from both the plants is different. Batch plant produce a better quality of hot mix asphalt compared to a drum type plant.
How an asphalt plant works – Batch asphalt plant
The working of an asphalt mixing plant depends on its type. The batch type will produce hot mix asphalt in batches. Below is explanation of how an asphalt batch plant works:
• Aggregate is the first component that we start our process with. Different sized aggregates are fed into the different feeder bins. This helps in getting proper proportion of each size as per the need. Each bin will have individual gear and variable speed drive motor. It is possible to control the speed of each bin to get proper proportion of each item.
• Drying drum will receive the aggregates once they pass through the primary screening unit. Rotating drum is inclined to allow smooth passage of the aggregates.
• Burner unit will heat up the aggregates so that they are ready for coating with bitumen and filler.
• As the air along with dust particles enter, heavy dust particles are trapped by the pre-separator. Air is made to pass through series of bags inside bag filter. Lighter particles will get accumulated on the bags and clean air will pass through the dust collection system. Filter bags are cleaned thoroughly and all the dust collected is carried through screw conveyor.
• Filler is stored in filler silos or filler bins and available for mixing. Filler is transferred via a screw or bucket elevator to its weighing unit.
• Hot aggregate elevator will take up the heated aggregates to the top of the tower unit. There are many buckets driven by a chain system to carry the aggregates.
• Multi deck vibrating screens will receive the aggregates from the hot elevator. It will separate the aggregates as per the different sizes.
• They are then stored in the hot bins in separate compartments. Hot bin compartment is below the screening unit. Each compartment has radial gates to feed aggregates into the weighing hopper.
• Aggregates will be discharged from the hot bins as per the pre-defined recipe.
• Bitumen is stored in tanks. Here they will be heated to make it flow easily. There can be more than one bitumen tank to allow sufficient storage and uninterrupted flow of bitumen. It is transferred via pipeline to the bitumen scale. Bitumen and filler are received by its respective weighing units. Here they are accurately measured prior to discharge into the mixing unit.
• All components are added into the mixer for mixing. The powerful mixing force ensures that aggregates are rapidly and evenly encased with layer of bitumen. They are discharged via the door below the mixer.
• Hot mix asphalt can also be stored into the silo from where it will be ready to be discharged into the truck. After the mixing cycle the homogeneous mixture of hot mix asphalt is ready for laying.
• Working of the asphalt mixing plant is controlled by the system. It has all the features and controls for each part. Adding and editing recipes is possible from the control panel.
How an asphalt plant works – Drum asphalt plant
The continuous type will produce hot mix asphalt in a continuous process. Continuous asphalt plants are also known as drum type or drum mix asphalt plants. Below is the explanation of how an asphalt drum plant works:
• Different size of aggregates are fed into the different feeder bins. Each bin will have individual gear and variable speed drive motor to allow proper grading.
• Drying and mixing drum will receive the aggregates once they pass through the primary screening unit. Drum is rotating and is inclined to allow smooth passage of the aggregates. This drum unit is equipped with a burner unit. Drum will heat aggregates as well as mix the aggregates with bitumen and filler material.
• Burner unit will heat up the aggregates in the first half of the drum. They are now ready for coating with bitumen and filler. This coating with bitumen and filler material is done in the second half of the drum.
• As the air along with dust particles enter, dust particles are trapped by the wet dust collector. The heavy and light dust particles are trapped by the jet flow of water and then treated to a cyclonic effect. Once this is done, they will be discharged out in form of a sludge.
• Filler is stored in filler silos or filler hoppers. Filler is pushed into the drum via a compressor.
• Bitumen stored in tanks are heated to make bitumen flow easily. There can be more than one bitumen tank to allow sufficient storage and uninterrupted flow of bitumen. It is transferred via pipeline through a bitumen pump.
• Once bitumen and filler are received into the other half of the drum, they will thoroughly coat the heated aggregates.
• Control panel will control the flow of all the materials. All the important mix material data can be printed out.
We produce and export asphalt batch plants of 60-80 tph, 80-100 tph, 100-120 tph, 160 tons, 180 tph, 200 tph and 260 tph per hour. Our hot asphalt batch mixers come with a host of components and features. The machines are with top quality component and promise smooth operation.
Contact us here to learn more.
