what are an asphalt plants?

Asphalt plant is equipment that is designed to produce hot mix asphalt. It uses aggregates, sand, bitumen and filler material in specific proportions to produce HMA also known as asphalt concrete or black top. The main feature of an asphalt mixing plant is that it will heat aggregates and then mix them with bitumen and other adhesive substances to prepare hot mix asphalt which is a paving material. Aggregate here can be a single sized material or it can be combination of various materials of different sizes with a combination of fine and coarse particles with or without addition of a filler unit.

Types of Asphalt Plants

So many types of asphalt mixing plants, small/Large, mobile, batch/discontinuous, drum/continuous hot mix plants, are available on market. Learn about types of asphalt mixing plants here. When you decide to get your own one, the first issue you have to address is to determine what type of hot mix plant you’d like to purchase.

What’s the basis of classification? What’s the difference between these types? What characteristics are available for each type? What type of mixing plants are most suitable for your road construction projects? For your convenience, we have put together everything you would like to know about types of hot mix plants and explain them in detail here.

1. Small/Medium/Large Type Asphalt Plant – Based On Production Capacity

Based on production capacity, asphalt mixing equipment can be divided into three types: small/mini, medium and large. In the eyes of different manufacturers or users from different countries, sorting methods vary greatly.

  • Small portable asphalt plant: hot mix plants with a capacity below 40t/h
  • Medium type asphalt plant: capacities ranging from 40t/h to 400t/h
  • Large hot mix plants: the ones with a capacity of more than 400t/h

There are other viewpoints, for example, someone regard ones with capacity from 20t/h to 100t/h as small and medium hot mix plants, yet large ones have a capacity of more than 100t/h.

No matter how to sort them by production capacity, small and medium mixing equipment are fit for relatively small and medium-scale road construction projects and so forth, while the large ones are suitable for bigger road construction projects.

2. Stationary/Semi-stationary/Mobile Type Asphalt Plant – Based on the Mobility

According to the mobility, all hot mix plants can be divided into mobile, semi-stationary and stationary.

  • Mobile ones can be transferred with the construction site, because they are mounted on chassis, and their aggregate silos and mixers are equipped with tires
  • semi-stationary asphalt mixing plant is installed on several trailers and can be reassembled when it arrives at the new construction site.
  • The stationary plant, also known as asphalt concrete processing factory, has its operation site fixed in a place, can’t move around during the construction process.

The finished mixture produced by mobile mixing plants doesn’t have to be transported to the required location, while stationary mixing equipment needs vehicles to transport finished mixture to the designated spot.

3. Batch Mix/Drum Mix Type Asphalt Plant – Based on the Mixing Method

* BATCH MIX PLANT:

The asphalt concrete batch mix plant consists of a number of components.

The first component is the cold aggregate feeder bins where the aggregates are stored/fed in separate components as per their sizes. There are auxiliary feeder belts below each bin and gathering conveyor that runs below all the bins. This conveyor will transfer all the aggregates to another inclined conveyor belt that will take all the materials into the drying drum. Before the materials are transferred to the inclined conveyor belt, they aggregates have to pass through vibrating screen so that oversize materials are removed.

The next component is the drying drum. It is fitted with a burner unit for moisture removal and heating of aggregates are carried out to achieve proper mixing temperature. These aggregates are them carried to the top of the tower unit by an elevator.

The tower unit consists of 3 main units: vibrating screen on top then we have the hot bins and mixing unit is below the hot bins. As the aggregates are carried to the top of the tower unit, they are made to pass through the multi deck vibrating screen (usually four screens are there) so that aggregates are separated as per their sizes. After separation they are temporarily stored in different compartments called as hot bins. This section of hot bins is just below the screening unit. Hot bins will store the aggregates in individual bins and then release the same into the mixing unit below as per the weight set in the control panel. At the time when aggregates are weighed and released into the mixing unit, bitumen and optional mineral filler is also weighed and released into the mixing unit. After proper mixing, the mixture is released into waiting trucks of into the storage silo.

For environmental protection, air pollution control devices are equipped. These devices in most of the cases are bag filter units. The fines are made to pass through the bags present in the bag filter and the dust is trapped by the bags. This dust collected can also be reintroduced into the aggregate elevator.

* DRUM MIX PLANTS:

The cold bins are the same in asphalt drum mixers like in batching plants. The process here is also the same till the aggregates enters the drum unit by passing through the vibrating screen. The drum here serves two purposes – that of drying and mixing. The first half of the drum is for heating the aggregates and in the second half mixing with bitumen and filler material takes place. Since this is a continuous mixing plant, a small sized hopper for temporary holding the HMA is provided. Bitumen is stored in separate tanks and it is added into the second part of the drum. For pollution control, wet scrubber or bag filters are provided with the plant.

4. Eco-friendly/Traditional Type Asphalt Plant – Based on Environmental Effectiveness

Eco-friendly Asphalt batch Plant

Hot mix plants for sale can fall into eco-friendly type and traditional type according to the environmental influence that they bring.

Eco-friendly hot mix plants adopt special environmental protection measures to significantly reduce air pollution and noise emissions.

Environmental protection measures include enclosed belt conveyors, enclosed mixer tower, high-efficiency activated carbon to filter bitumen smoke, superior dust collecting system, central control system to avoid hot aggregate overflow, etc.

Traditional Type Asphalt batch Plant

Traditional type generally doesn’t adopt special environmental protection measures.

5. Resource Recycling/Non-recycling Type Asphalt Plant – Based on Resource Recycling Feature

Asphalt Recycling Plant

By using hot recycling technology, some mixing plants can be classified as asphalt recycling plants (also called hot recycled asphalt plant). This type can fully make use of RAP, one kind of old asphalt mixture, save fuel and material, reduce pollution and waste, bring better economic and environmental benefits.

Asphalt fumes and harmful gas can be recycled into drying drum and burn again, reducing harmful fume emission; multi-stage dust collecting system can help reduce dust emission

Non-recycling Type Asphalt Plant

It didn’t use the hot recycling technology.