Multi-Step Density Separation for Plastic Recovery
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Solution Overview
Problem
Current recycling methods for plastics from electrical devices are inefficient, leading to contamination, loss of valuable plastics, and inability to meet the properties required by the modern electronics industry.
Innovation Solution
A multi-step density separation process is employed, involving first, second, and third density separations in specific density ranges, along with metal removal and further sorting using triboelectric and spectroscopic methods, to isolate and purify various polymer types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If density separation is used to separate plastics, then separation of polymer types is achieved, but contamination with foreign components occurs and purity is insufficient
Solution Approach 1:
The recycling process is divided into multiple sequential density separation steps with different density thresholds. The first separation at density < 1.15 g/cm³ isolates light fractions (polyolefins, styrene-based polymers), while the second separation at density < 1.08 g/cm³ further purifies these fractions. This segmented approach allows each separation stage to target specific polymer types, reducing cross-contamination and improving overall fraction purity.
Solution Approach 2:
Different density thresholds are applied to different separation stages to optimize purification for specific polymer types. The first separation uses a higher density threshold (1.15 g/cm³) to capture a broader range of recyclable plastics, while the second separation uses a lower threshold (1.08 g/cm³) to achieve high purity of light fractions. This localized optimization of separation parameters ensures each fraction meets the required purity standards for its intended application.
2Productivity
If traditional recycling processes are used, then processing capacity is maintained, but plastic loss occurs and recovery rates are low
Solution Approach 1:
A preliminary density separation step is performed before main processing to pre-concentrate valuable plastic fractions. By separating light fractions (density < 1.15 g/cm³) and further purifying them through a second separation (density < 1.08 g/cm³), the process prepares high-purity streams that can be efficiently processed downstream, minimizing losses during subsequent handling and processing stages.
Solution Approach 2:
The process utilizes controlled changes in density parameters through sequential separation steps. By adjusting the density threshold from 1.15 g/cm³ in the first separation to 1.08 g/cm³ in the second separation, the process optimizes recovery of different plastic fractions while maintaining high processing capacity. This parameter optimization ensures maximum plastic recovery without sacrificing productivity.
3Quantity of substance
If plastics are recycled through conventional methods, then volume reduction is achieved, but property requirements for modern electronics are not met
Solution Approach 1:
The process extracts and isolates specific high-value polymer fractions (styrene-based polymers and polyolefins) through selective density separation. By removing these fractions as pure streams with density < 1.15 g/cm³ and further purifying them to density < 1.08 g/cm³, the process produces plastic materials with properties suitable for high-quality applications in modern electronics, rather than mixing them with lower-quality fractions.
Solution Approach 2:
The sequential density separation process transforms the physical state and purity of plastic fractions by controlling density parameters. The first separation at 1.15 g/cm³ concentrates valuable polymers, while the second separation at 1.08 g/cm³ achieves the high purity required for manufacturing precision applications. This parameter control ensures recycled plastics meet the stringent property requirements of modern electronics industry.
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 significantly increases the recovery of styrene-based polymers and polyolefins, minimizes plastic loss, and produces essentially pure polymer fractions that can be reused in high-quality products, akin to those made from original factory-fresh polymers.
Implementation Method 1
performing a first density separation in a first density separation step at a density in the range of 1.14 to 1.18 g/cm3, obtaining a first light fraction and a first heavy fraction
Implementation Method 2
separating the first light fraction into a styrene-based polymer fraction and a polyolefin fraction in a triboelectric sorting step
Implementation Method 3
separating the styrene-based polymer fraction into polymer fractions in a spectroscopic sorting step
Data Source
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AI summary
The invention relates to a method for recovering plastics from a mixture of at least two polymers, wherein one polymer comprises a proportion of 1 to 99 wt.-% is contained, comprising: (a) performing a first density separation (3) at a density in the range of 1.14 to 1.18 g/cm3, obtaining a first light fraction (5) and a first heavy fraction (7); (b) feeding the first light fraction to a second density separation (13) at a density in the range of 1.00 to 1.03 g/m3, obtaining a second light fraction (15) and a second heavy fraction (17); (c) Feeding the first heavy fraction (7) to a third density separation (153) at a density in the range of 1.18 to 1.24 g/cm3, obtaining a third light fraction (155) and a third heavy fraction (157), (d) separating all fractions into fractions containing essentially pure polymers, wherein metal-containing components (143, 147) are removed from the first heavy fraction (7) prior to the third density separation (153).