Continuous Polyester Recycling via Alcoholysis and Transesterification
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Solution Overview
Problem
Current methods for recycling waste polyester, such as chemical recycling, face challenges with long alcoholysis times, uneven product quality, and the need for additional equipment and energy due to intermittent reactions.
Innovation Solution
A continuous alcoholysis and transesterification process involving multiple tanks in series, where waste polyester is pretreated, continuously fed into alcoholysis and transesterification tanks with catalysts and agents, allowing for homogeneous reactions and stable product quality, reducing side reactions and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If intermittent alcoholysis and transesterification reactions are used, then equipment complexity is reduced, but alcoholysis time is extended and product quality becomes uneven
Solution Approach 1:
The patent implements continuous alcoholysis and transesterification reactions, where waste polyester and alcoholysis agent are continuously fed into the reaction system, and the alcoholysis product is continuously transported to the transesterification tank. This continuous operation eliminates idle time between batches, maintains constant reaction conditions, and significantly reduces total alcoholysis time while improving product quality uniformity.
Solution Approach 2:
The patent divides the continuous reaction process into multiple stages with separate tanks: a first alcoholysis tank, a second alcoholysis tank, and a transesterification tank. Each tank performs a specific function and can be independently controlled, allowing optimization of reaction conditions in each stage while maintaining overall continuous operation.
2Device complexity
If intermittent alcoholysis and transesterification reactions are used, then equipment investment is reduced, but energy consumption increases
Solution Approach 1:
The continuous reaction system maintains constant temperature and pressure conditions throughout operation, eliminating the repeated heating and cooling cycles required in intermittent batch processes. The continuous flow of materials through heated tanks ensures sustained reaction temperatures without energy loss from shutdowns and restarts, significantly reducing overall energy consumption despite higher initial equipment investment.
3Duration of action of moving object
If continuous alcoholysis is implemented, then alcoholysis time is shortened and product quality is stabilized, but device complexity increases
Solution Approach 1:
The continuous alcoholysis process is divided into multiple tanks (first alcoholysis tank and second alcoholysis tank), each with controlled residence time. This segmentation allows the overall alcoholysis time to be distributed across stages, maintaining continuous operation while managing device complexity through modular design. Each tank can be independently optimized and maintained.
4Manufacturing precision
If continuous transesterification is implemented, then product quality is stabilized and yield is improved, but device complexity increases
Solution Approach 1:
The transesterification process is implemented in a dedicated transesterification tank that receives alcoholysis product continuously. This separate, specialized tank allows optimization of transesterification conditions (temperature, catalyst concentration, residence time) independently from the alcoholysis stage, stabilizing product quality and improving DMT yield while keeping the overall device complexity manageable through functional separation.
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 method shortens alcoholysis time, stabilizes product quality, and increases the yield and purity of Dimethyl Terephthalate (DMT), while minimizing equipment and energy costs through continuous feeding and processing.
Implementation Method 1
The chemical recycling methods mainly include hydrolysis method, alcoholysis method, ammonolysis method, amine hydrolysis method, thermal cracking method and other degradation methods. An important direction of the chemical recycling method is the alcoholysis of waste polyester with ethylene glycol (EG) into bishydroxy terephthalate (BHET) or oligomers
Implementation Method 2
the alcoholysis product is then through transesterification in methanol to produce Dimethyl Terephthalate (DMT) and ethylene glycol
Implementation Method 3
crystallization, separation and purification of raw DMT
Implementation Method 4
the alcoholysis product is then through transesterification in methanol to produce Dimethyl Terephthalate (DMT) and ethylene glycol. Pure DMT is obtained through purification and used as a raw material for polyester production
Data Source
AI summary
The invention present invention belongs to waste polyester recycling technology field and relates to a method and a device for recycling waste polyester, in particular to a method and a device for recycling waste polyester by modified chemical method to recover waste polyester to prepare dimethyl terephthalate (DMT). The recycling method of the present invention uses a process of continuous feeding, continuous alcoholysis and continuous transesterification. It can make the material undergo homogeneous alcoholysis in the melted state, and the required alcoholysis time is short. Because more than two alcoholysis tanks are used in series for continuous alcoholysis, the product quality of alcoholysis product is stable. When the alcoholysis product is continuously transesterified, it avoids the occurrence of side reactions and the unstable quality of the transesterified product, and the purity and yield of recycling product of waste polyester are greatly improved.