Polymer Granule Drying Circuit With Gas Purification and Low Emissions
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Solution Overview
Problem
Conventional drying plants for granular polymer materials, particularly those containing recycled polyethylene terephthalate (rPET), suffer from high chemical impurity levels, such as benzene and acetaldehyde, which compromise product quality and emit pollutants, while being inefficient and complex.
Innovation Solution
A drying plant with a process gas circuit that includes a dehumidification and heating unit, a purification group with a condenser and activated carbon filter, and a cyclone separator to remove contaminants, optimizing energy efficiency and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If granular polymer material is dried in a conventional fluidized bed dryer, then the material can be dried, but the polymer granules aggregate and form larger granules due to sintering at elevated temperatures
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (60-90°C) to sub-ambient temperatures (-30 to +30°C). This parameter change prevents sintering while maintaining drying effectiveness by using isothermal heat exchange that transfers heat from warm inlet air to cooler outlet air, achieving energy-efficient drying without granule aggregation
Solution Approach 2:
The patent replaces the conventional thermal drying mechanism with an isothermal heat exchange mechanism. Instead of heating the granules directly to evaporate moisture, the system uses counter-current air flow where warm inlet air transfers heat to cooler outlet air through the granular bed, enabling moisture removal at low temperatures without mechanical sintering
2Manufacturing precision
If granular polymer material is dried at low temperatures to prevent aggregation, then granule size is maintained, but the drying time increases significantly
Solution Approach 1:
The patent implements continuous counter-current air flow through the granular bed, where fresh warm air continuously enters at the bottom and dries the granules as they move upward, while dried cool air continuously exits at the top. This continuous action maintains high drying efficiency throughout the process without requiring extended time, even at low temperatures
Solution Approach 2:
The patent employs periodic regeneration of the air stream by continuously introducing fresh warm air at the inlet and removing saturated cool air at the outlet. This periodic renewal of the drying medium maintains the driving force for moisture removal throughout the drying process, preventing time extension despite low operating temperatures
3Productivity
If conventional drying methods are used, then drying capacity is achieved, but the polymer granules undergo sintering and lose their original properties
Solution Approach 1:
The patent changes the temperature parameter to sub-ambient range (-30 to +30°C) and maintains isothermal conditions throughout the drying process. This parameter change preserves polymer granule properties by preventing sintering while achieving effective drying through continuous isothermal heat exchange between counter-current air streams
Solution Approach 2:
The patent substitutes the conventional thermal heating mechanism with an isothermal heat exchange mechanism. By using counter-current air flow where heat transfers from warm inlet air to cooler outlet air through the granular bed, the system achieves drying capacity without subjecting polymer granules to high temperatures that would alter their composition or properties
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 plant effectively reduces chemical impurities and emissions, improving the quality of dried granular polymer materials, especially rPET, with enhanced energy efficiency and simplified construction.
Implementation Method 1
a heat exchanger for preheating the inlet air stream by heat exchange with the outlet air stream
Implementation Method 2
drying of granular polymer material in which water is removed from the granular polymer material at low temperatures
Data Source
Figure 1
Figure 2
AI summary
A plant for drying granular polymer material comprises a hopper, in which granular polymer material is dried, and a process gas circuit which is configured to supply a process gas to the hopper in order to dry the granular polymer material.