Twin-Screw Heated Mixer for Pollutant-Tolerant Bitumen Recycling
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Solution Overview
Problem
Existing recycling technologies for bituminous waterproofing membranes from construction waste are inadequate in handling non-recoverable pollutants like metallic and mineral particles, leading to blockages and wear, and fail to achieve efficient heating and shearing of composite materials.
Innovation Solution
A heated mixer with interpenetrating twin screws featuring discontinuous blades and a deformable scraping structure, designed to heat and shear materials while allowing passage of macroscopic pollutants, reducing wear and preventing blockages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional heating and shearing devices are used to process bituminous membranes, then the materials can be heated and mixed, but macroscopic pollutants cause blockages and excessive wear
Solution Approach 1:
The mixing device is segmented into distinct functional zones: a first mixing zone for initial heating and mixing, and a second mixing zone with a screen structure for filtration. The screen structure itself is segmented into multiple screens with different mesh sizes to handle different types of pollutants at different stages
Solution Approach 2:
A screen structure acts as an intermediary element between the mixing zones and the discharge. This screen structure with varying mesh sizes filters macroscopic pollutants while allowing processed material to pass through, preventing blockages in downstream equipment
2Productivity
If intensive shearing is applied to break down composite materials, then mixing efficiency improves, but wear on the mixing device increases significantly
Solution Approach 1:
The mixing process is segmented into two zones with different intensity levels. The first zone provides gentle initial mixing, while the second zone with the screen structure provides controlled shearing. This segmentation prevents excessive wear that would result from intensive shearing throughout the entire mixing length
Solution Approach 2:
The mesh size parameter of the screen structure varies along the mixing path, creating zones of different shearing intensity. This gradual change in shearing parameters allows effective mixing while controlling wear on the screen structure and mixing device components
3Reliability
If the mixing device is designed to handle macroscopic pollutants, then blockages are prevented, but the device complexity increases
Solution Approach 1:
The screen structure serves multiple functions simultaneously: it acts as a mixing element, a filtering mechanism, and a support structure for the mixing zones. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting overall device complexity
Solution Approach 2:
The screen structure is nested within the mixing device housing, with multiple screens of different mesh sizes arranged concentrically or in sequence. This nested arrangement allows complex pollutant handling capabilities to be achieved within a compact structure, limiting the increase in device 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
Effectively heats and shears bituminous membranes while removing macroscopic pollutants, ensuring reliable and sustainable processing of construction waste into reusable products.
Implementation Method 1
progressively and simultaneously heat the inputs until they reach a softening/melting temperature of the bituminous binder
Implementation Method 2
shear the membranes (pre-cut or not) to cause their reinforcements to break down and disintegrate
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
The invention relates to a heated mixer (1) for composite products based on thermoplastic material(s), having an elongated constitution defining a longitudinal processing path between an inlet and an outlet and comprising a heated trough (3) in which are mounted two parallel and mutually interpenetrating twin screws (4 and 4'), forming dimensional reduction, heating and displacement element(s) for the products to be treated introduced at the inlet, each screw (4, 4') comprising a heated and driven support shaft (5), arranged along the path direction (DT).Mixer (1) characterized in that the thread (4") of each screw (4, 4') is an interrupted or discontinuous thread and comprises, over at least a major part of the length of the screw (4, 4') considered, a plurality of first blades (6) in the form of flat and smooth plates, separated from each other axially and radially and all arranged according to a constant screw pitch and with a determined inclination with respect to a plane perpendicular to the axis of the screw (4, 4') considered.