Agglomerated Mixed Plastic Grinding in Refiners
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Solution Overview
Problem
Current methods for processing mixed plastics are inefficient in separating and recycling different types of plastics due to their mixed composition, leading to incomplete separation and contamination, which hinders their reuse and recycling.
Innovation Solution
A method involving the shredding and compaction of mixed plastics into agglomerates, followed by grinding in low-consistency refiners with controlled water addition and recirculation, allows for effective separation and cleaning of impurities, enabling the production of uniform granular material suitable for various applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mixed plastics are directly ground without compaction, then the grinding process is simplified, but thin films pass through without being shredded and the grinding efficiency is poor
Solution Approach 1:
The patent applies preliminary compaction of mixed plastics into agglomerates before grinding. This pre-processing step transforms thin films and scattered plastic pieces into compacted agglomerates with diameter not exceeding the distance between grinding ribs, ensuring they will be effectively shredded during subsequent grinding while maintaining process simplicity
2Quantity of substance
If the diameter of agglomerate is large, then transport bulk density is improved, but the spaces between grinding ribs become blocked
Solution Approach 1:
The patent specifies a critical parameter constraint: agglomerate diameter must not exceed the distance between grinding ribs. This parameter optimization ensures that agglomerates are compacted sufficiently to achieve high transport bulk density while remaining small enough to pass through the grinding rib spaces without blocking, maintaining continuous grinding operation
3Manufacturing precision
If mixed plastics are separated into pure plastics, then recycling quality is improved, but the separation effort and complexity increase significantly
Solution Approach 1:
The patent applies segmentation by separating the recycling process into distinct stages: compaction of mixed plastics into agglomerates, grinding into multi-fractions, and then selective processing of each fraction. This segmentation allows different plastic types to be handled in appropriate downstream processes without requiring complete separation at the initial stage, reducing overall system complexity while maintaining recycling quality
4Reliability
If water is added during grinding, then cleaning and cooling effects are achieved, but energy consumption increases
Solution Approach 1:
The patent employs hydraulic principles by using water spray systems during the grinding process. Water is sprayed onto the agglomerates as they enter the grinder, providing simultaneous cooling and cleaning effects. The water acts as a hydraulic medium that absorbs heat and carries away fine particles and contaminants, achieving reliable cleaning and cooling while the spray efficiency minimizes water and energy consumption
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 process enhances the recycling efficiency of mixed plastics by achieving high material yield, reducing contamination, and producing a granular material with improved flowability and reduced energy consumption, thus enabling their use in diverse applications such as construction materials and fuel.
Implementation Method 1
the plastic is cleaned by washing and abrasion, whereby glass splinters, ground pulp or the finest aluminum powder can be removed with the process water
Implementation Method 2
By spraying the heated, melted plastic mass with cold water at intervals, some of the organic components escape via the water vapor
Implementation Method 3
the melted pieces of film cool down, are broken up by the knife rotors of the agglomerator and agglomerate into pourable, granular-like structures
Data Source
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AI summary
The invention relates to a method for comminuting and cleaning waste plastic, particularly mixed plastic (MKS) with the following steps: a compacted material, particularly an agglomerate, is produced from film scraps or from film remnants, which are comminuted into flakes, and/or from thick-walled plastic parts, which are chopped up into chips. The compacted material is introduced into a disc or drum refiner and is ground therein in the presence of water. The portion of compacted material of the stock located inside the refiner is at least 10 percent by weight. A fine-grain fraction is removed from the ground stock exiting the refiner. The remaining ground stock is washed and either mechanically dewatered and dried or is ground once more in another refiner stage in the presence of water after which it is dewatered and dried.