Energy Efficiency
Drying Drum is the key component of asphalt plant economy and reliability
The drying drum is the biggest energy consumer of an asphalt plant. Environmental factors, such as amounts of dust releases and exhaust gas emissions are also depending on the drying drum. The oil consumption between different asphalt plant manufacturers can vary a lot depending on the drum construction and control methods. For the final asphalt mix quality the drying drum and its control are essential factors. The temperature of the heated aggregate should be correct to avoid structural damage of aggregates by overheating.
In asphalt mixing the reliability of the asphalt plant is extremely important. Downtime of the plant can endanger the project schedule and it also causes expensive waiting time for asphalt transportation and road paving equipment and personnel. The reliability of the drying drum is decisive for the reliability of the whole plant. Especially when using lower quality heavy oils, the drying drum is often causing more downtime of the plant than any other plant component.
A reliable, energy efficient and environmental friendly drying drum requires both correct construction and control features.
Construction of Drying Drum
Important construction criteria:
- - optimum diameter and length of the drum
- - drum insulation and sealing of drum ends (Amomatic: labyrinth seal and rubber seal)
- - quality of the burner (Amomatic: Oertli from Switzerland)
- - replaceable internal parts (Amomatic: all paddles bolt-mounted)
- - drum mechanical efficiency easy to adjust (Amomatic: rotation speed adjusted by inverter)
- - reliable aggregate temperature measurement (Amomatic: fast thermocouple)
- - coarse dust separation after the drying drum (Amomatic: Dust-Eater within the drum).
The most used method for aggregate temperature measurement within asphalt plants is infrared sensor. The disadvantage of it is the need of continuous cleaning in order to get correct indication. When using thermocouple, cleaning is not needed but the problem of rapid wearing of the drum exists. By Amomatic Antiwear protection the same thermocouple can be used for years without need of change or maintenance.
Coarse dust separation after the drying drum is usually performed by a separate coarse dust filter and coarse dust conveyor. Amomatic uses Amomatic dust-eater integrated in the drying drum; separate coarse dust filter and separate conveyor are not needed. Simple construction without moving parts means additional reliability and reduced need for maintenance.
Control of Drying Drum by adjustment of rotation speed
When using inverter for adjustment of rotation speed, the drum can be adapted to different stone materials with different moistures and to different aggregate temperatures. Adjustment of drum inclination or altering the number of paddles inside the drum, which is time-consuming and inaccurate, is no longer needed. The speed adjustment has an extensive effect on the properties of the drying drum.
The possibility to control the rotation speed of the drying drum means that the plant can be operated more reliably than before and the oil consumption can be minimized. By adjusting the drum rotation speed the operator can keep the exhaust gas temperature above the dew point to guarantee trouble-free operation. At the same time the operator can secure that the temperature is not higher than necessary to minimize the oil consumption. Advanced control of drying drum means also reliable operation of dry dust filter, longer life-time of the filter and lower emissions.
