Polyolefin Recycling Sorting and Washing by Foreign Material Layer
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Solution Overview
Problem
Current mechanical polyolefin recycling processes face challenges in achieving high purity and efficiency due to the use of costly and energy-intensive washing conditions, often resulting in recycled materials with poor mechanical properties and contamination from non-polyolefin materials, especially in the recycling of flexible articles with external foreign material layers.
Innovation Solution
A mechanical recycling process that sorts polyolefin recycling streams into multiple fractions based on the presence or identity of external foreign material layers and applies tailored washing conditions for each fraction, optimizing temperature, duration, and solution to achieve high purity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If uniform washing conditions are applied to all polyolefin recycling fractions, then the process is simple and cost-effective, but the purity and quality of recycled materials with foreign material layers are insufficient
Solution Approach 1:
The recycling stream is divided into multiple fractions based on the presence or type of foreign material layers. Each fraction is then washed with conditions optimized for its specific contamination type, achieving high purity without requiring overly complex uniform treatment for all materials.
Solution Approach 2:
Different washing conditions (temperature, duration, solution type) are applied to different fractions of the recycling stream according to their specific requirements. This localized optimization ensures each fraction achieves maximum purity with appropriate treatment intensity.
2Manufacturing precision
If harsh washing conditions are used to remove foreign materials, then purity is improved, but energy consumption and costs increase
Solution Approach 1:
By segmenting the recycling stream into fractions with similar contamination types, the washing process can apply milder, more energy-efficient conditions to each fraction rather than using harsh uniform conditions for all materials.
Solution Approach 2:
Washing parameters (temperature, duration, solution concentration) are optimized for each fraction's specific needs. This prevents unnecessary energy consumption from applying excessive washing intensity to fractions that require gentler treatment.
3Manufacturing precision
If strong washing solutions are applied to remove all foreign materials, then purity is enhanced, but mechanical properties of recycled polyolefin deteriorate
Solution Approach 1:
The recycling stream is separated into fractions based on foreign material type, allowing each fraction to receive washing treatment appropriate to its contamination level and type, preventing over-washing that would damage polyolefin mechanical properties.
Solution Approach 2:
Washing intensity and solution strength are locally optimized for each fraction's specific contamination type, ensuring sufficient foreign material removal while preserving the mechanical integrity of the polyolefin in each fraction.
4Productivity
If multiple sorting steps are implemented to separate fractions by foreign material layers, then washing efficiency is improved, but process complexity increases
Solution Approach 1:
The recycling stream is divided into a manageable number of fractions based on foreign material characteristics, enabling efficient washing of each fraction while avoiding excessive complexity from creating too many separate processing lines.
Data Source
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AI summary
The present invention relates to mechanical polyolefin recycling process, wherein flexible articles are sorted by at least the presence/absence or identity of an external foreign material layer, with each of the resultant fractions of the recycling stream washed using conditions optimised for said stream, as well as to a mechanical polyolefin recycling apparatus configured for carrying out the mechanical polyolefin recycling process. The mechanical polyolefin recycling process, comprising, in the given order, the steps of a) providing a precursor polyolefin recycling stream (A) that contains polyolefin-containing pieces, wherein the precursor polyolefin recycling stream (A) contains at least 70 wt.-% of polyolefin-containing films; b) sorting the pieces of the precursor polyolefin recycling stream (A) in one or more sorting steps by means of one or more sorters to form two or more polyolefin recycling fractions (B), wherein the precursor polyolefin recycling stream (A) is at least sorted by the presence/absence or identity of an external foreign material layer, wherein the foreign material is any non-polyolefin material; c) washing each of the two or more polyolefin recycling fractions (B) individually, wherein the washing conditions for each of the two or more polyolefin recycling fractions (B) may be the same or different, with the proviso that at least one of the washing conditions is different to at least one other washing condition in least one variable selected from the group consisting of washing temperature, washing duration, washing solution, thereby generating two or more washed polyolefin recycling fractions (C).