PVC Waste Plastic Dechlorination for Refinery Chemical Feedstock
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Solution Overview
Problem
The presence of chlorine atoms in waste plastics streams, particularly from polyvinyl chloride (PVC), poses challenges in processing mixed waste plastics due to corrosion of equipment and interference with catalytic activity, making it difficult to meet the composition specifications required by refinery and chemical facilities.
Innovation Solution
A process involving dechlorination of PVC in waste plastics streams by heating under vacuum or inert gas sweep to form partially unsaturated PVC, followed by separation and combination with an atmospheric residue stream, then processing through a vacuum distillation unit and coker unit to produce suitable chemical products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If waste plastics containing PVC are processed directly in refinery and chemical facilities, then material circularity is improved, but equipment corrosion and interference with catalytic activity occur
Solution Approach 1:
The patent applies preliminary action by implementing a dechlorination step before the waste plastics enter the refinery and chemical processing facilities. The plastics are heated to 200-300°C in a reactor to convert PVC to partially unsaturated PVC, removing chlorine atoms that would otherwise cause equipment corrosion and catalytic interference. This preliminary treatment enables the waste plastics to be processed in existing facilities without causing harmful effects.
Solution Approach 2:
The patent converts the harmful chlorine atoms in PVC into beneficial partially unsaturated PVC through thermal decomposition. The chlorine atoms are removed as HCl gas during heating, transforming the harmful PVC into a form that can be processed in refinery facilities. This conversion turns the previously harmful material into a useful feedstock for producing chemical products and fuels.
2Object-affected harmful factors
If dechlorination is performed by heating PVC to remove chlorine atoms, then equipment corrosion is reduced, but energy consumption increases
Solution Approach 1:
The patent optimizes the heating parameters to achieve effective dechlorination while minimizing energy consumption. The reactor operates at 200-300°C, which is sufficient to convert PVC to partially unsaturated PVC and remove chlorine atoms, but not excessively high to waste energy. The residence time is controlled to ensure complete dechlorination without prolonged heating that would increase energy consumption.
Solution Approach 2:
The patent uses an intermediary approach by introducing a reactor system that facilitates controlled thermal decomposition. The reactor acts as an intermediary between the waste plastics and the refinery facilities, performing the dechlorination function in a controlled environment before the material enters the main processing stream. This intermediary step reduces the energy burden on subsequent processing equipment.
3Manufacturing precision
If mixed waste plastics are processed through multiple separation and processing steps, then composition specifications are met, but process complexity increases
Solution Approach 1:
The patent segments the processing process into distinct functional units: a dechlorination reactor for removing chlorine, a separation system for removing partially unsaturated PVC, and a blending system for combining with atmospheric residue. This segmentation allows each step to perform its specific function efficiently while maintaining overall process manageability. The segmented approach ensures composition specifications are met without requiring overly complex integrated systems.
Solution Approach 2:
The patent uses atmospheric residue as an intermediary material that blends with the dechlorinated waste plastics. This intermediary blending step helps meet composition specifications by diluting and stabilizing the feedstock before it enters the refinery facilities. The atmospheric residue acts as a mediator that bridges the gap between the processed waste plastics and the requirements of the receiving facilities.
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
Significantly reduces chlorine content in waste plastics, enabling their use in refinery and chemical facilities, thereby improving the circularity of plastic materials and reducing equipment corrosion.
Implementation Method 1
heating under vacuum or inert gas sweep to form partially unsaturated PVC
Implementation Method 2
passing the plastics stream (C) comprising partially unsaturated PVC that is removed from the reaction vessel over a filter system
Implementation Method 3
processing through a vacuum distillation unit and coker unit
Implementation Method 4
processing through a vacuum distillation unit and coker unit to produce suitable chemical products
Data Source
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AI summary
The present invention relates to a process for the conversion of plastics to chemicals comprising in this order the steps of: (i) providing a plastics stream (A) comprising polyvinyl chloride (PVC); (ii) supplying the plastics stream (A) and a solvent (S) to a reactor vessel (1); (iii) subjecting the plastics in the reactor vessel to a temperature of > 250°C to < 350, preferably of > 275°C and < 325°C, preferably for a period of 5-30 minutes, under applying a vacuum, preferably of < 200 mbar, or using an inert gas sweep, and evacuating the generated hydrogen chloride (B) from the vessel, wherein the PVC is partially dechlorinated to form a plastics stream (C) comprising partially unsaturated PVC; (iv) removing the plastics stream (C) comprising partially unsaturated PVC from the reaction vessel; (v) separating in a separation system (2) at least a part of the partially unsaturated PVC from the plastics stream to form a dechlorinated plastics stream (D) comprising the solvent; (vi) combining the stream (D) with an atmospheric residue stream (N) to obtain a stream (O); (vii) supplying the stream (O) to a vacuum distillation unit (3) to produce a vacuum gas oil stream (Q) and a vacuum residue stream (P) that meets the chlorine specifications for a coker unit (4); and (viii) providing the stream (P) to the coker unit, and subjecting the coker unit (4) to such conditions to obtain a liquid coker stream (I) and a solid coke product (L). Such process allows for the conversion of plastic compositions comprising PVC into chemical products that are suitable for renewed use as raw materials in for example the production of high-quality polymer materials, thereby contributing to improvement of circular use of plastic materials.