An asphalt plant is a complex system that aims to produce high quality hot asphalt mixture of a given composition and set temperature. The technological and structural characteristics of asphalt plants are determined by the mode of production and the mix of asphalt. This means that asphalt plants can be cyclical and continuous.
Typically asphalt plants utilise a cyclical type of agitation. The cyclic mode is a method where all resources (minerals, fillers and binding agents) are first weighed and then added to a mixer which then runs a mixing cycle to combine them. Once all the inputted resources are mixed, the mixer is emptied and is ready for a new mixing cycle. Therefore the asphalt mix production process takes place in cycles. These plants mostly have a medium to large production output.
Asphalt plants which incorporate a continuous mode of mixing have different production outputs. Their technology is simpler and because of this it is more mobile and suitable for quick and frequent relocation. When compared to cyclical plants, they result in lower costs and greater energy savings. A mixer incorporating a continuous mode of mixing is constantly fed with input resources (minerals, fillers and binding agents) and is continuously discharged as a ready mix. This mix can be discharged into a ready-mix silo or directly onto a lorry. For this type of plant it is necessary to have superlative mineral components (stone aggregates).
Asphalt plants are also sub-divided into static equipment mounted onto concrete foundations, static plants mounted on a metal foundations and mobile asphalt plants. Static plants mounted on metal foundations are easier to install and can be migrated from one location to another with far less difficulty than plants on concrete foundations. These plants are referred to as semi-mobile and the cables and pipelines of such facilities are designed for simple and fast assembly and disassembly.
One of the key factors when selecting an asphalt plant is plant capacity: this depends on the type of asphalt plant, which can range from 80t/h to 400t/h.
The basic systems that comprise each asphalt plant are:
- A pre-dosing system
- A drying and heating system
- A dust collection system
- A mixing tower
- A silo for asphalt mix that can be located next to or integrated into the mixing tower
- A filler delivery system
- A binder (bitumen) delivery system
- A facility control system
Due to greater energy savings, new technologies, better use of resources and the introduction of new standards within the asphalt industry, asphalt plants are upgraded with various sytems. Recently, one of the most popular system upgrades is the incorporation of foamed bitumen (Schaumbitumen) system for the production of low-temperature asphalt which is the future of asphalt industry. This asphalt allows for considerable energy savings whilst providing the same quality of asphalt mixtures. The foamed bitumen (Schaumbitumen) system is often used in asphalt reclamation systems. Combining these two methods allows for considerable energy savings and reduces resource consumption while the asphalt mix retains the same quality as non-reclaimed asphalt systems.
This also contributes to improvements in the quality of production and it should be mentioned that the use of polymer fibres and polymer bitumen provide a better quality of asphalt mix and upgrading to a new plant control system allows for easier and better process management and control of expenditure on materials and the energy asphalt plant which in turns brings savings on energy and resources (minerals, fillers and binding agents).