Indirect Heating Drum for Recycled Asphalt Processing
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Solution Overview
Problem
Existing asphalt drum mixers face issues with product degradation and environmental pollution due to direct heating and mixing methods, which result in gaseous hydrocarbon emissions and sticky dust particles, as well as inefficient recycling of recycled asphalt products.
Innovation Solution
An indirect heating, drying, and mixing chamber design featuring a drum within a heat-insulating enclosure with burners positioned to create two heating paths, allowing heated gases to make two full passes along the drum, reducing direct contact with flames and promoting efficient heat transfer and mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If direct heating with burner flame is used in drum mixer, then heating efficiency is improved, but product degradation and blue smoke emissions occur
Solution Approach 1:
The heating process is segmented into two distinct paths: an upper heating path and a lower heating path. The lower heating path uses burners positioned at the bottom to heat air that rises through the drum, while the upper heating path uses burners at the top to heat air that descends. This segmentation allows efficient heating while preventing direct flame contact with materials, eliminating blue smoke and product degradation.
Solution Approach 2:
Heated air acts as an intermediary medium between the burner flame and the asphalt materials. The burners heat the air, and this hot air then transfers heat to the materials through the drum walls and internal structures, preventing direct contact between the flame and materials while maintaining efficient heat transfer.
2Productivity
If co-current flow design is used where asphalt ingredients flow in the same direction as hot gases, then mixing efficiency is improved, but asphalt components come in direct contact with hot gas stream and burner flame causing degradation
Solution Approach 1:
The conventional co-current flow is inverted to create a counter-current flow system. Hot air rises through the lower section of the drum while cooler air descends through the upper section. This inversion ensures that asphalt materials are heated by hot air rather than direct flame contact, preventing degradation while maintaining mixing efficiency through the counter-current heat exchange mechanism.
Solution Approach 2:
Air serves as an intermediary medium that transfers thermal energy from burners to asphalt materials without allowing direct flame-material contact. The hot air stream heats materials in the lower section while cooler air in the upper section receives heat, creating an efficient counter-current heat exchange that protects asphalt components from thermal degradation.
3Speed
If single-pass heating through drum mixer is used, then processing speed is improved, but uniform heating and drying of recycled asphalt products is insufficient
Solution Approach 1:
The heating path is segmented into two complete passes: a lower heating path where hot air rises from bottom burners through the drum, and an upper heating path where hot air descends from top burners. Materials are conveyed through both paths, receiving uniform heating from both upper and lower sections, ensuring thorough and consistent processing while maintaining efficient throughput.
Solution Approach 2:
The dual-path heating system provides continuous heating action as materials pass through both the lower rising hot air path and the upper descending hot air path. This continuous exposure to heated air in both sections ensures complete and uniform drying and heating of recycled asphalt products without requiring multiple separate processing stages.
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 solution minimizes product degradation and environmental impact by ensuring uniform heating and mixing of recycled asphalt products, reducing emissions and improving the recycling efficiency while maintaining the quality of the asphaltic composition.
Implementation Method 1
heat which travels along the lower section of the enclosure and through the upper section of the enclosure heating the material in the drum
Implementation Method 2
heat which travels along the lower section of the enclosure and through the upper section of the enclosure heating the material in the drum
Implementation Method 3
A mixing/conveyor mechanism is positioned within the drum mixing and moving materials through the drum
Data Source
AI summary
An indirect heating, drying and mixing chamber has a drum. A mixing/conveyor mechanism is positioned within the drum mixing and moving materials through the drum. An enclosure is provided wherein the drum is inserted within the enclosure to form an upper section of the enclosure between the drum and a top surface of the enclosure and a lower section of the enclosure between the drum and a bottom surface of the enclosure. A plurality of heat openings is formed on the bottom surface of the enclosure. A plurality of heating elements is provided, wherein an individual heating element is coupled to a corresponding heat opening, the plurality of heating elements generating heat which travels along the lower section of the enclosure and through the upper section of the enclosure heating the material in the drum.