Dual Drum Aggregate Coating Plant for High RAP Recycling
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Solution Overview
Problem
Current asphalt production technologies for road surfacing face challenges in achieving high recycling rates of asphalt aggregates, leading to increased consumption of new aggregates and higher production costs.
Innovation Solution
The proposed aggregate coating installation utilizes a dual-drum system where the first drum dries and heats aggregates, and the second drum, supplied with gases from the first, further dries and mixes asphalt aggregates with heated aggregates and binder, allowing for a high recycling rate without direct exposure to high-temperature flames or gases, thus optimizing energy use and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single dryer drum with burner is used to dry and heat aggregates, then energy consumption is reduced and cost-effectiveness is improved, but the recycling rate of asphalt aggregates is limited and cannot achieve 50% or higher
Solution Approach 1:
The system divides the drying process into two separate drums: a first dryer drum for initial drying of fresh aggregates, and a second dryer drum for drying recycled asphalt aggregates. This segmentation allows each drum to be optimized for its specific function, enabling high recycling rates while maintaining energy efficiency through the single burner setup in the first drum.
Solution Approach 2:
The first drum acts as an intermediary that pre-dries fresh aggregates before they are mixed with recycled materials in the second drum. This intermediary step allows the second drum to operate at lower temperatures with reduced energy input, achieving high recycling rates without proportionally increasing energy consumption.
2Productivity
If multiple burners are installed to increase drying capacity for high recycling rates, then the recycling rate can be improved, but the equipment complexity and production costs increase
Solution Approach 1:
Instead of adding multiple burners to a single drum, the system segments the drying function across two drums with a single burner in the first drum. This segmentation achieves the required drying capacity for high recycling rates without increasing the number of burners or significantly complicating the equipment.
Solution Approach 2:
The first drum serves the dual purpose of drying fresh aggregates and providing pre-dried material for the second drum. This self-service arrangement eliminates the need for additional burners, as the first drum's output supports the second drum's high recycling rate requirement without extra energy input equipment.
3Device complexity
If a single dryer drum is used to reduce equipment complexity, then device complexity is reduced, but the ability to dry and mix asphalt aggregates efficiently at high recycling rates is compromised
Solution Approach 1:
The drying function is segmented into two drums, which initially appears to increase complexity. However, this segmentation enables the second drum to be simpler in design since it only needs to dry recycled aggregates at lower temperatures without handling the full drying load, ultimately achieving high recycling rates with manageable overall system complexity.
Solution Approach 2:
The first drum acts as an intermediary that handles the complex initial drying of fresh aggregates, allowing the second drum to focus on the simpler task of drying recycled materials at lower temperatures. This division enables high recycling rates while keeping each individual drum relatively simple in design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables a recycling rate of 50% or higher, reducing the need for new aggregates and lowering operational expenses by efficiently utilizing heat from the first drum to dry and mix asphalt aggregates in the second drum, while maintaining a single burner setup for cost-effectiveness.
Implementation Method 1
a burner (8) to form a flame (F) and heat the gases circulating in the first drum (4)
Implementation Method 2
the flow of hot gas passing through the curtain of aggregates
Implementation Method 3
the aggregates are raised and fall back forming a curtain of aggregates inside the dryer drum
Implementation Method 4
Due to the inclination of the dryer drum, the aggregates introduced through the raised end of the dryer drum gradually move towards the lowered end of the dryer drum
Implementation Method 5
the second drum, supplied with gases from the first, further dries and mixes asphalt aggregates with heated aggregates and binder, allowing for a high recycling rate
Data Source
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AI summary
The aggregate coating plant is configured for the production of asphalt mixes from fresh aggregates and recycled fresh asphalt pavement (RAP). It comprises a first drum (4) for drying by circulating gas within the first drum (4), and a second drum (6) for drying by circulating gas within the second drum (6). The second drum (6) is separate from the first drum (4). The plant is configured to feed the second drum with at least a fraction of the RAP. The second drum (6) is fluidly connected in series with the first drum (4) for the circulation, within the second drum (6), of gas that has previously circulated within the first drum (4). The application also relates to an aggregate coating process for the production of asphalt mixes from fresh aggregates and recycled RAP.