Polymer Conversion Using Supercritical Water Flash Depressurization
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Solution Overview
Problem
Current methods for recycling polymeric materials, such as plastics, are inefficient and result in significant waste accumulation, energy loss, and environmental pollution, with existing pyrolysis processes facing issues like char formation, blockages, and the inability to handle impurities effectively.
Innovation Solution
A method involving extrusion of polymeric materials with supercritical water to create a reaction mixture, followed by rapid depressurization in a flash vessel to vaporize and fractionate hydrocarbon products, utilizing the energy of the vapor for further processing and separating impurities, while using supplementary catalysts and controlled conditions to enhance yield and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If external heat is applied in pyrolysis processes, then polymer conversion to hydrocarbons is achieved, but char formation and hot surface blockages occur
Solution Approach 1:
The patent replaces external thermal heating with a mechanical/chemical reaction system. Polymer granules react with steam in a flash vessel to generate heat internally through exothermic reactions, eliminating the need for external heat application and the associated problems of char formation and hot surface blockages
Solution Approach 2:
Steam is introduced as an intermediary substance that facilitates the conversion process. The steam reacts with the polymer to generate heat and drive the depolymerization reaction, serving as both a heat transfer medium and a reactant, thereby avoiding direct external heating of the polymer mass
2Productivity
If heat is applied to polymer masses, then conversion to hydrocarbons occurs, but blockages in plant equipment result
Solution Approach 1:
The polymer is pre-heated and pre-mixed with steam before entering the reaction zone, ensuring uniform temperature distribution and preventing localized overheating that would cause blockages. The rapid depressurization is also a preliminary action that prevents char formation before it can block equipment
Solution Approach 2:
The process uses rapid depressurization to quickly pass through the temperature and pressure conditions that would otherwise cause blockages. The flash vaporization occurs so rapidly that there is no time for char formation or equipment blockage, skipping the problematic intermediate states
3Productivity
If catalytic processes are used for pyrolysis, then hydrocarbon yield is improved, but sensitivity to impurities reduces reliability
Solution Approach 1:
The patent changes the reaction parameters from low-temperature catalytic conditions to high-temperature steam flash conditions. This parameter change makes the process less sensitive to catalyst poisoning by impurities while maintaining high hydrocarbon yield through the extreme conditions that favor depolymerization
Solution Approach 2:
The process uses a disposable catalyst bed that can be easily replaced. Rather than protecting a valuable, sensitive catalyst, the system uses a inexpensive catalyst that can be quickly changed, making the process more reliable when handling impure feedstocks
4Loss of energy
If incineration is used for waste plastic disposal, then energy recovery is achieved, but valuable hydrocarbon feedstock is lost
Solution Approach 1:
The process utilizes phase transitions (vaporization and condensation) to separate and recover hydrocarbons from the reaction products. The rapid depressurization causes flash vaporization of hydrocarbons, which are then condensed and collected, preventing their loss that would occur in incineration
Solution Approach 2:
The reaction products are segmented into different phases (vapor and liquid) through rapid depressurization, allowing selective recovery of the hydrocarbon fraction. This segmentation enables simultaneous energy recovery and feedstock preservation that incineration cannot achieve
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 approach enhances the conversion of polymeric materials into valuable hydrocarbon products, reduces waste, and recovers energy, effectively handling impurities and improving the overall efficiency and sustainability of plastic recycling.
Implementation Method 1
the liquid product stream is rapidly depressurised causing vaporizes a large proportion of the liquid product stream generating a vapour
Implementation Method 2
the vapor formed is fractionated into constituent parts wherein some or all of the fractionated material is condensed
Data Source
Figure 1A
Figure 1B
Figure 2~3
AI summary
The present invention provides methods and an apparatuses for converting polymeric material into hydrocarbon products.