Supercritical CO2 Plastic Dissolution and Purification
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Solution Overview
Problem
Current plastic recycling methods, such as mechanical recycling and chemical recycling, are inadequate in removing impurities like additives and metals from plastic waste, limiting the purity of recycled polymers and requiring high energy consumption.
Innovation Solution
A process involving dissolution of plastic feedstock in a solvent at specific temperature and pressure conditions, followed by washing with a dense solution, and recovery of purified polymers, effectively removing impurities and achieving high purity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical recycling is used to reuse plastic waste, then productivity is improved, but manufacturing precision deteriorates due to insufficient removal of impurities like additives and metals
Solution Approach 1:
The patent changes the physical-chemical parameters of the system by using supercritical carbon dioxide (temperature above 31.1°C and pressure above 73.8 bar) to selectively dissolve and remove impurities from the polymer matrix, achieving high purity while maintaining productivity
Solution Approach 2:
The patent exploits the phase transition of carbon dioxide between supercritical and gaseous states to achieve impurity removal: CO2 becomes supercritical to dissolve impurities, then returns to gaseous state to leave pure polymer, enabling efficient purification without residual solvent
2Manufacturing precision
If chemical recycling via pyrolysis is used to reform monomers, then manufacturing precision is improved, but use of energy deteriorates due to high temperature treatments
Solution Approach 1:
The patent uses moderate temperature and pressure conditions with supercritical CO2 instead of high-temperature pyrolysis, achieving effective impurity removal at lower energy input while maintaining high polymer purity
Solution Approach 2:
The patent replaces thermal decomposition (pyrolysis) with a solvent-based extraction system using supercritical CO2, substituting high-energy thermal processes with a more energy-efficient phase-change-based separation method
3Manufacturing precision
If dissolution and purification by washing with dense solution is used, then manufacturing precision is improved, but device complexity worsens
Solution Approach 1:
The patent employs CO2 that is already present in the industrial environment or can be easily obtained as a byproduct, eliminating the need for complex solvent synthesis or handling systems, thereby reducing device complexity while achieving high purification
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 process achieves a significant reduction in impurity content, allowing purified polymers to be reused in various applications, conserving fossil resources, and reducing solvent consumption.
Implementation Method 1
a) a dissolution step involving placing the plastic feedstock in contact with a dissolution solvent, at a dissolution temperature of between 100° C. and 300° C. and a dissolution pressure of between 1.0 and 20.0 MPa abs, to obtain at least one crude polymer solution
Implementation Method 2
b) a step of washing by placing the crude polymer solution obtained from step a) in contact with a dense solution, at a temperature of between 100° C. and 300° C., a pressure of between 1.0 and 20.0 MPa abs and at a mass ratio between the mass flow rate of the dense solution and the mass flow rate of the crude polymer solution which feeds step b) of between 0.05 and 20.0, to obtain at least one washed polymer solution and one washing effluent
Data Source
AI summary
The present invention relates to a process for treating a plastic feedstock comprising polymers, comprising:a) a dissolution step involving placing the plastic feedstock in contact with a dissolution solvent, at a dissolution temperature of between 100° C. and 300° C. and a dissolution pressure of between 1 and 20.0 MPa abs, to dissolve at least a portion of the polymers of the plastic feedstock and to obtain a crude polymer solution;b) a step of washing by placing the crude polymer solution in contact with a dense solution, at a temperature of between 100° C. and 300° C., a pressure of between 1 and 20.0 MPa abs and at a mass ratio between the dense solution and the crude polymer solution of between 0.05 and 20.0, to obtain a washed polymer solution and a washing effluent; and thenc) a step of recovering the polymers, to obtain a solvent fraction and a purified polymer fraction. FIG. 1 to be published