Bituminous Drying Drum Recirculation for High RAP Content
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing industrial plants for producing bituminous macadams are not very versatile and have limitations in using high percentages of recycled material while also reducing pollutant emissions.
Innovation Solution
A drier and industrial plant design that includes a second drier for recycled bituminous material, featuring a combustion chamber with a specific feed system and recirculation duct to increase the percentage of recycled material and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single burner drier with double drum is used, then the drying capacity is maintained, but the versatility and ability to process high percentages of recycled material is limited
Solution Approach 1:
The drier is divided into two separate drums: a first drum for drying virgin materials and a second drum for drying recycled bituminous materials. This segmentation allows each drum to be optimized for its specific function, enabling the system to process high percentages of recycled material while maintaining overall drying capacity and versatility.
2Quantity of substance
If recycled bituminous material is heated to high temperatures, then the percentage of recycled material can be increased, but pollutant emissions increase
Solution Approach 1:
The patent introduces a recirculation duct that redirects part of the hot combustion gas flow back into the combustion chamber. This recirculated gas helps maintain high temperatures for drying recycled material while also contributing to the reduction of pollutant emissions by promoting more complete combustion and reducing harmful byproducts.
Solution Approach 2:
The system changes the temperature and flow parameters of the combustion gas by recirculating it. The recirculated hot gas modifies the combustion conditions, allowing the maintenance of high drying temperatures while reducing pollutant formation through improved combustion efficiency and gas recirculation.
3Object-generated harmful factors
If a recirculation duct is added to reduce pollutant emissions, then emissions are reduced, but the device complexity increases
Solution Approach 1:
The recirculation duct serves multiple functions: it reduces pollutant emissions by improving combustion efficiency, maintains high temperatures for effective drying of recycled material, and optimizes the use of combustion gas. This multi-functionality justifies the addition of the recirculation duct despite the increased device complexity.
4Productivity
If the first drum is used for virgin materials and second drum for recycled materials, then the drying process is optimized, but the system complexity increases
Solution Approach 1:
Each drum is designed with specific local characteristics optimized for its intended purpose: the first drum is optimized for virgin materials while the second drum is optimized for recycled bituminous materials. This local optimization of each component allows the overall system to achieve high drying efficiency for different material types despite the increased system complexity.
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
The solution allows for an increase in the percentage of recycled material used in bituminous macadams to up to 90-100% while effectively reducing pollutant emissions, achieving higher temperatures for the RAP material without affecting the inert lithic material.
Implementation Method 1
at least one burner (14) for introducing in the drying drum (10) a flow (F1) of combustion gas co-current to a flow (F2) of recycled bituminous material
Implementation Method 2
a flow (F1) of combustion gas co-current to a flow (F2) of recycled bituminous material which is movable, by means of said feed system, between the outlet (12a) of the loading channel (12) and the unloading opening (13)
Implementation Method 3
a recirculation duct (16) extending between an outlet chamber (15) of the flow (F1) of combustion gas and the combustion chamber (11) and a suction system (17) for sucking a flow (F3) of recirculation air along the recirculation duct (16) and injecting it into the drying drum (10)
Implementation Method 4
a plurality of tiles (24) fixed to an inner surface of the drying drum (10) at the combustion chamber (11). The tiles (24) are configured to prevent the lifting of the recycled bituminous material which therefore advances sliding on the bottom (10a) of the drum
Implementation Method 5
The feed system comprises a comb-type blading, fixed to the inner surface of the drying drum downstream of the flame of the burner and the tiles. The blading determines a rain of the material through the flow of hot air in a drying zone in the drying drum.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Described is a drier of recycled bituminous material comprising a drying drum (10) comprising a combustion chamber (11); a channel (12) for loading the recycled bituminous material into the drying drum (10); an opening (13) for unloading the recycled bituminous material from the drying drum (10) positioned on the opposite side to the loading channel (12) along the drying drum (10); a system for feeding the recycled bituminous material in a feed direction (V) from said loading channel (12) to said unloading opening (13); a burner (14) for introducing in the drying drum a flow (F1) of combustion gas co-current to a flow (F2) of the recycled bituminous material movable between the loading channel (12) and the unloading opening (13); an outlet chamber (15) at least of the flow (F1) of combustion gas located at the unloading opening (13) of the recycled bituminous material; the drier being comprises a recirculation duct (16) extending between the outlet chamber (15) and the combustion chamber (11) and a suction system for sucking a flow (F3) of recirculation air along the recirculation duct (16) and injecting it into the drying drum (10); the recirculation duct (16) and the drying drum (10) are configured in such a way that the flow (F3) of recirculation air is co-current with the flow (F2) of recycled bituminous material.