Integrated Pyrolysis and Hydroprocessing for Waste Plastic Dechlorination
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Solution Overview
Problem
Waste plastics containing polyvinylchloride (PVC) and polyvinylidene chloride (PVDC) pose challenges in pyrolysis processes due to high chloride content and limited olefin production, making it difficult to produce hydrocarbon feedstocks that meet steam cracker requirements.
Innovation Solution
A process integrating pyrolysis, hydroprocessing, and hydrodealkylation to convert waste plastics into hydrocarbon streams with reduced chloride content and increased C6-C8 aromatic hydrocarbons, suitable for steam cracking, involving a pyrolysis unit, hydroprocessing unit, and hydrodealkylating unit to produce treated hydrocarbon streams that can be fed into a steam cracker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If waste plastics containing PVC and PVDC undergo pyrolysis, then hydrocarbon liquid products are produced, but the products contain high concentrations of chlorides and limited olefin content which do not meet steam cracker feed specifications
Solution Approach 1:
The patent extracts and removes harmful chloride components from the pyrolysis liquid products through dedicated dechlorination units and washing stages, separating the harmful chlorides from the valuable hydrocarbon products to meet steam cracker feed specifications
Solution Approach 2:
The patent converts the harmful chlorides present in PVC and PVDC waste plastics into useful hydrogen chloride gas that can be captured and utilized, transforming a contaminant into a potentially valuable byproduct while cleaning the hydrocarbon stream
2Quantity of substance
If waste plastics containing PVC and PVDC undergo pyrolysis, then hydrocarbon liquid products are produced, but the products have limited olefin content which does not meet steam cracker feed specifications
Solution Approach 1:
The patent performs preliminary hydrocracking and hydroprocessing of the pyrolysis liquid products before steam cracking, breaking down heavy molecules and adjusting the olefin content in advance to meet the specific feed requirements of the steam cracker
Solution Approach 2:
The patent changes the chemical parameters of the pyrolysis liquid through hydroprocessing conditions (temperature, pressure, catalysts) to adjust the olefin content and molecular weight distribution, transforming the product composition to match steam cracker feed specifications
3Device complexity
If a single hydroprocessing reactor is used for dechlorination and hydrocracking, then process complexity is reduced, but the ability to maximize C6-C8 aromatic production and meet specific feed requirements is compromised
Solution Approach 1:
The patent segments the hydroprocessing into multiple specialized reactors: a first reactor for dechlorination and a second reactor for hydrocracking and aromatic production. This segmentation allows each reactor to be optimized for its specific function, maximizing C6-C8 aromatic yield while maintaining a manageable process configuration
Solution Approach 2:
The patent applies different local conditions (catalysts, temperature, pressure) in different reactor zones to achieve specific transformations. The first reactor uses conditions optimized for chloride removal, while the second uses conditions optimized for aromatic production, allowing each zone to perform its specialized function effectively
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 effectively reduces chloride content and enhances the production of C6-C8 aromatic hydrocarbons and light gas olefins, meeting steam cracker feed specifications and maximizing the production of high-value products like ethylene and propylene.
Implementation Method 1
converting a plastic waste to a hydrocarbon liquid stream and a first C1 to C4 gas stream in a pyrolysis unit
Implementation Method 2
contacting at least a portion of the first hydrocarbon product with a hydrodealkylating catalyst in the presence of hydrogen to yield a second hydrocarbon product
Implementation Method 3
feeding at least a portion of the treated hydrocarbon stream to a steam cracker to produce a steam cracker product stream
Data Source
Figure 1
Figure 2~3A
Figure 3B~5A
AI summary
A process for processing plastic waste comprising converting plastic waste to hydrocarbon liquid and a first C1-4 gas; contacting hydrocarbon liquid with a first hydroprocessing catalyst in hydroprocessing unit to yield a second C1-4 gas and a first hydrocarbon product comprising C5+ liquid hydrocarbons; introducing the first hydrocarbon product to a first separating unit to produce treated hydrocarbon stream comprising C5-8 hydrocarbons and a first heavies stream comprising C9+ hydrocarbons; contacting the first heavies stream with a second hydroprocessing catalyst in hydrodealkylating unit to yield a second hydrocarbon product comprising C5+ liquid hydrocarbons and a third C1-4 gas; conveying the second hydrocarbon product to the first separating unit; feeding treated hydrocarbon stream to steam cracker to produce steam cracker product; separating steam cracker product into olefin gas, saturated hydrocarbons gas, aromatics, and a second heavies stream; and conveying the second heavies stream to hydroprocessing unit.