Chemo-Mechanical MLP Recycling Through PET Depolymerization
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Solution Overview
Problem
Metallized multi-layered plastic packaging (MLP) is difficult to recycle due to its composite nature, leading to high transportation costs and environmental issues, with existing methods resulting in downcycling or low-grade fuel production, and current recycling processes are inefficient and environmentally harmful.
Innovation Solution
A chemo-mechanical recycling process involving a washing chamber, dryer, agglomerator shredder, chemical reactor, cooling tank, filtration chambers, and acidification chamber to depolymerize PET into terephthalic acid (TPA) and separate aluminum, polyolefins, and cellulose, using NaOH and H2SO4 to recover valuable materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MLP is recycled using conventional methods (waste-to-energy, waste-to-fuel, or combined with cement/silica), then the material can be disposed of, but the value is destroyed and environmental harm increases
Solution Approach 1:
The invention segments the composite MLP material into its individual components (PET, aluminum, polyolefins, EVOH, paper) through a multi-step process involving alkaline hydrolysis, filtration, and separation. This allows each component to be recovered and reused independently, preventing the value destruction and environmental harm associated with conventional downcycling methods
Solution Approach 2:
The invention changes the chemical parameters of the MLP components through controlled reactions. Specifically, PET is converted to terephthalic acid and monoethylene glycol through alkaline hydrolysis using NaOH at elevated temperatures and pressures. The aluminum is converted to aluminum hydroxide precipitate. These parameter changes enable the recovery of high-purity materials that can be reused, avoiding the environmental harm of landfilling or incineration
2Ease of manufacture
If MLP is transported for recycling, then recycling can occur, but transportation costs increase due to high volume and low mass
Solution Approach 1:
The invention extracts and removes the valuable components (PET, aluminum, polyolefins) from the MLP composite structure through chemical and physical separation processes. By taking out these components in concentrated, high-value forms, the system makes recycling economically viable despite transportation requirements, as the recovered materials command premium prices that offset logistics costs
3Manufacturing precision
If MLP is processed through chemical reactions to depolymerize PET, then high-quality materials are recovered, but process complexity increases
Solution Approach 1:
The invention performs preliminary actions by first washing and drying the MLP to remove contaminants, then shredding it into smaller pieces to increase surface area. The material is pre-treated with NaOH solution before the main depolymerization reaction, which facilitates more efficient and selective chemical breakdown of PET into high-purity terephthalic acid and monoethylene glycol
Solution Approach 2:
The invention uses sodium hydroxide (NaOH) as an intermediary substance that mediates the conversion of PET to its monomers. The NaOH facilitates the alkaline hydrolysis reaction, breaking down the polyester bonds in PET without directly becoming part of the final product. This intermediary enables precise control over the depolymerization process while maintaining high material quality
4Ease of manufacture
If MLP is landfilled, then disposal is achieved, but resource loss and environmental pollution occur
Solution Approach 1:
The invention applies discarding and recovering by systematically separating and recovering valuable materials (PET as terephthalic acid, aluminum as hydroxide precipitate, polyolefins as separated plastic) from the MLP composite. This process transforms what would be discarded waste into recovered resources that can be fed back into manufacturing, eliminating both resource loss and the need for landfilling
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 recovers 90-95% of MLP materials, including 90% PET depolymerization into monomers, improves recyclability, reduces contamination, and is environmentally friendly, while being cost-effective and robust against various contaminants.
Implementation Method 1
reacting by a chemical reactor IV, the MLP with an aqueous solution of NaOH to both simultaneously dissolve the aluminium and depolymerize the PET (that is within the MLP) by alkaline hydrolysis reaction
Implementation Method 2
acidifying by the acidification chamber VIII disodium terephthalate with concentrate sulfuric acid (H2SO4) to obtain white precipitate
Implementation Method 3
separating by a gravity filtration chamber V, solid and liquid materials
Implementation Method 4
separating based on density segregation chamber VI, polyolefins from metal hydroxide, unreacted PET and cellulose based on density
Implementation Method 5
separating white precipitate by vacuum filtration chamber IX to get the terephthalic acid (TPA) as residue
Implementation Method 6
drying by a dryer II, waste material received after washing
Data Source
AI summary
The present invention relates to a recycling system & method. The present invention particularly relates to a chemo-mechanical recycling system & method for post-consumer, metalized multi-layered plastic packaging (MLP) comprising: a washing chamber (I) for washing waste materials sourced from local waste-pickers, a dryer (II) for drying washed waste material, an agglomerator shredder (III) for shredding waste material, a chemical reactor (IV) for simultaneous reaction of de-metallization of MLP and depolymerization of PET within the MLP, a cooling tank for cooling reacted waste material obtained from chemical reactor in a gravity filtration chamber (V) for separating solid and liquid residue, a density segregation chamber for separating polyolefins from metal hydroxide, unreacted PET and cellulose in density, an acidification chamber (VIII) with concentrate sulfuric acid (H2SO4) to obtain white precipitate, a vacuum filtration chamber (IX) to separate white precipitate to obtain terephthalic acid (TPA) as residue which contains sodium sulphate.