Plastic Particle Separation via Density and Electrostatic Stages
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Solution Overview
Problem
Existing methods for separating particles from different plastics, particularly PVC, struggle to achieve high-quality, pure fractions due to limitations in electrostatic separation processes, especially when dealing with composite materials containing non-ferrous metals and elastomers, requiring extensive drying and additional separation steps.
Innovation Solution
A method involving multiple stages of density separation using liquids of varying densities, followed by electrostatic separation, with the use of sodium phosphinate solutions and ethanol as additives, to achieve further pure fractions, including eddy current and magnetic separation to handle conductive particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electrostatic separation is used to separate PVC particles from other plastics, then separation based on dielectric properties is achieved, but the process requires extensive drying to reduce residual moisture to a maximum of 0.2 wt.-%, increasing process complexity and energy consumption
Solution Approach 1:
The invention performs preliminary density-based separation using liquid media before electrostatic separation. This pre-separation removes fractions that would interfere with subsequent electrostatic charging, allowing the electrostatic separation to focus on dielectric property differences and achieve high purity with reduced drying requirements.
Solution Approach 2:
The invention divides the separation process into distinct stages: first density-based separation into light and heavy fractions, then electrostatic separation of the dried fraction. This segmentation allows each separation mechanism to optimize for its specific function, improving overall purity while managing drying requirements at specific process points.
2Manufacturing precision
If multiple density separation steps using different liquids are performed sequentially, then additional pure particle fractions are obtained, but the drying effort and process time increase significantly
Solution Approach 1:
The invention performs preliminary density-based separation using liquid media before electrostatic separation. This pre-separation removes fractions that would interfere with subsequent electrostatic charging, allowing the electrostatic separation to focus on dielectric property differences and achieve high purity with reduced drying requirements.
Solution Approach 2:
The invention replaces repeated mechanical density separation steps with electrostatic separation based on dielectric properties. This substitution reduces the number of drying cycles needed, as electrostatic separation can effectively separate particles without requiring them to be completely dry, thereby reducing process time and energy consumption.
3Reliability
If the sink fraction is dried mechanically and thermally to high dryness before electrostatic separation, then electrostatic separation can be performed successfully, but considerable energy and time are expended
Solution Approach 1:
The invention performs preliminary density-based separation using liquid media before electrostatic separation. This pre-separation removes fractions that would interfere with subsequent electrostatic charging, allowing the electrostatic separation to focus on dielectric property differences and achieve high purity with reduced drying requirements.
Solution Approach 2:
The invention changes the moisture content parameter requirement for electrostatic separation by performing preliminary density separation first. This removes interfering fractions, allowing electrostatic separation to achieve reliable results with lower moisture content requirements, thereby reducing the energy and time needed for drying.
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
The method enhances the quality of separation by producing additional pure fractions with reduced moisture content, enabling effective separation of plastics based on dielectric properties and density, resulting in higher purity and improved material properties.
Implementation Method 1
suspending the particles in a liquid having a density of 1.00 to 1.23 g/cm3 and separating the particles suspended in the liquid into a light fraction and a heavy fraction
Implementation Method 2
separating the dried particles from the light fraction and the heavy fraction by electrostatic separation into a first charged fraction and a second uncharged fraction
Implementation Method 3
non-ferrous metals are separated between drying and electrostatic separation using an eddy current separator
Implementation Method 4
The sink fraction is dried mechanically using a centrifuge
Data Source
Figure 1
AI summary
To separate particles (6) made of different plastics, the particles (6) are suspended in a first liquid (10) with a first density and separated into first light particles (11) with a lower density and first heavy particles (12) of at least the first density. The first heavy particles (12) are dried and then separated by a first electrostatic separation (19) on the basis of their dielectric properties into at least a first fraction (21) and a second fraction (22), the particles of which are electrostatically chargeable. The particles of the second fraction (22) are then suspended in a second liquid (25) with a greater second density and separated into second light particles (27) with a lower density and second heavy particles (28) of at least the second density.The second light particles (27) are dried and then separated into at least two further fractions (34, 35) by a second electrostatic separation (32) based on their dielectric properties.