PET Depolymerization Premixing Homogenization
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Solution Overview
Problem
Current depolymerization processes for polyethylene terephthalate (PET) face challenges in achieving efficient and cost-effective recycling due to the presence of pigments and dyes, which affect the mechanical properties and recyclability of opaque PET, and require complex purification steps to remove insoluble pigments, making the recycling of colored and opaque PETs highly problematic.
Innovation Solution
A process that involves conditioning the PET feedstock by partial melting and mixing it with an alcohol stream using static or dynamic mixers to achieve a homogeneous mixture with a viscosity of less than 50 mPa·s, facilitating a more efficient depolymerization reaction with reduced stirring power and operating costs, and enabling the treatment of PET wastes containing pigments and dyes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If depolymerization is performed on PET feedstock containing pigments and dyes, then the recycling of colored and opaque PET is enabled, but the mechanical properties of recycled PET are adversely affected and complex purification steps are required
Solution Approach 1:
The invention applies preliminary action by conducting a premixing stage before depolymerization where the PET feedstock is mixed with alcohol and catalyst under controlled conditions. This preliminary treatment ensures uniform distribution of components and proper wetting of pigment particles, which facilitates subsequent depolymerization and simplifies purification while maintaining mechanical properties.
Solution Approach 2:
The invention utilizes parameter changes by controlling temperature, alcohol-to-PET ratio, and mixing time during the premixing stage. These parameter optimizations create ideal conditions for depolymerization that reduce the complexity of purification steps needed to remove pigments and dyes while preserving the mechanical integrity of the recycled PET.
2Reliability
If complex purification steps are implemented to remove insoluble pigments, then the quality of recycled PET is improved, but the process complexity and operating costs increase
Solution Approach 1:
The premixing stage serves as a preliminary action that pre-treats the PET feedstock by ensuring uniform alcohol and catalyst distribution before depolymerization. This preliminary treatment breaks down the polymer structure in a controlled manner, making pigment removal easier and reducing the number of purification steps required while maintaining product quality.
Solution Approach 2:
The invention uses alcohol as an intermediary substance during the premixing and depolymerization stages. The alcohol facilitates the breakdown of PET and helps in the separation and removal of pigments and dyes, simplifying the purification process while ensuring high quality recycled PET output.
3Productivity
If homogeneous mixing of PET feedstock with alcohol is achieved, then depolymerization efficiency is enhanced, but the stirring power and energy consumption increase
Solution Approach 1:
The premixing stage acts as a preliminary action that achieves partial mixing and wetting of the PET feedstock with alcohol and catalyst before the main depolymerization process. This preliminary homogenization reduces the energy required during subsequent stirring operations while maintaining high depolymerization efficiency, as the materials are already partially combined and more reactive.
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 improves the homogenization and dispersion of the PET feedstock with the alcohol stream, enhancing the efficiency of the depolymerization reaction, reducing the required stirring power, and lowering operational costs, while effectively handling PET wastes with varying compositions, including opaque and multilayer PETs.
Implementation Method 1
mixing it with an alcohol stream using static or dynamic mixers to achieve a homogeneous mixture with a viscosity of less than 50 mPa·s
Implementation Method 2
exhibiting a viscosity of less than or equal to 50 mPa·s
Implementation Method 3
mixing it with an alcohol stream using static or dynamic mixers
Data Source
AI summary
The invention relates to a process for depolymerization of a polyester feedstock, comprising:a) conditioning of the feedstock using a means for at least partially melting the feedstock and at least one mixer, which are fed with the feedstock and a diol stream, with a ratio by weight between the diol stream and the feedstock of between 0.01 and 6.00, the volume degree of dilution with diol in each mixer being between 3% and 70%;b) depolymerization of the polyester feedstock at 150-300° C., the ratio by weight between the diol and the diester in step b) being adjusted between 0.3 and 8.0;c) optionally, the separation of the diol, at a temperature of between 60 and 250° C. and a pressure lower than that of step b).