Toothed Disk Refiner for Mixed Plastic Recycling
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Solution Overview
Problem
Existing methods for recycling mixed plastic waste struggle with effectively separating pulp and dirt from the plastic, leading to incomplete grinding and processing difficulties, especially with materials like PET, PP, and HDPE, which are hard to compact and grind due to high melting temperatures and rigidity.
Innovation Solution
The use of a toothed disk refiner for grinding agglomerates or compactates, which allows for more homogeneous particle mixing and fine grinding, enabling better separation of pulp from plastic, and subsequent mechanical dehydration and air separation to produce a pulp-free plastic fraction suitable for further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional disk or drum refiners are used for grinding waste plastic agglomerates, then the grinding process can be performed, but the pulp and dirt adherences are not effectively separated from the plastic particles
Solution Approach 1:
The patent changes the operational parameters of the refiner by adjusting the gap distance between grinding disks to 2-10 mm and controlling the rotational speed differential to create optimal shear forces. This parameter optimization enables effective separation of pulp and dirt from plastic particles while maintaining grinding quality.
Solution Approach 2:
The invention introduces dynamic elements by using independently rotating grinding disks with different rotational speeds, creating variable shear zones that dynamically adapt to different particle sizes and types. The system also incorporates adjustable gap distances that can be modified during operation to optimize separation effectiveness.
2Manufacturing precision
If the hole width between refiner teeth is reduced to improve grinding fineness, then particle size is reduced, but the refiner teeth are prone to clogging by non-melted plastic particles
Solution Approach 1:
The patent employs dynamic operational control by adjusting the rotational speeds of the grinding disks independently. This creates variable shear forces that prevent material buildup on the teeth while maintaining fine grinding. The system dynamically adapts to prevent clogging without sacrificing particle size uniformity.
Solution Approach 2:
The invention optimizes the gap distance parameter between grinding disks to 2-10 mm, which is wider than conventional refiners. This parameter change, combined with controlled rotational speed differentials, prevents clogging while achieving sufficient particle size reduction for effective pulp separation.
3Reliability
If moisture content in ground plastic is reduced to prevent steam formation during processing, then processing reliability improves, but pulp adheres more strongly to plastic particles
Solution Approach 1:
The patent performs preliminary mechanical dehydration of the ground plastic material before it enters the refiner grinding zone. This preliminary action removes excess moisture that would cause steam formation during subsequent processing, while the controlled grinding process maintains sufficient moisture to prevent pulp adhesion.
Solution Approach 2:
The invention controls the moisture content parameter within an optimal range by combining mechanical dehydration with controlled refiner operation. The gap distance and rotational speed parameters are adjusted to maintain moisture levels that prevent both steam formation and pulp adhesion simultaneously.
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 approach results in a more efficient grinding process, reducing wear on grinding disks and enabling the production of high-quality recycled plastic for applications like wood plastic composites, while also addressing the economic challenges of pulp disposal.
Implementation Method 1
The grinding of the agglomerate/compactate takes place in at least one refiner step, which contains a so-called toothed disk refiner
Implementation Method 2
The grinding preferably occurs in a disk or drum refiner in the presence of water
Implementation Method 3
The remaining ground material is washed or mechanically dehydrated and dried
Implementation Method 4
The remaining ground material is washed or mechanically dehydrated and dried
Data Source
AI summary
A method for the recycling of all types of waste plastic, in particular mixed plastic (MP), in which compactate, in particular agglomerate, is ground from flakes or other plastic parts in at least one refiner stage in the presence of water, from which fine particles are removed from the ground material emerging from the refiner stage with the process water, the remaining ground material is washed and/or mechanically dehydrated and dried or the dehydrated ground material is again ground in another refiner stage in the presence of water and then dehydrated and dried, wherein the grinding of the compactate is performed in at least one refiner stage using a disk refiner (toothed disk refiner), the disks of which have engaging teeth, which are arranged separated on concentric circles, wherein there is a hole between neighboring teeth of a circle and the holes of a circle are each big enough that the particles to be ground or ground up to that point can pass through freely.