Waste Plastic Conversion via Oligomeric Stream Recycle
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Solution Overview
Problem
Current methods for recycling mixed waste plastics are limited, as most are not suitable for direct reuse, leading to significant portions being discarded through incineration, and there is a need for alternative processing methods to increase material circularity and reduce virgin raw material use.
Innovation Solution
A process utilizing existing refinery assets, including a fractionation tower, furnace, and coke drums, where a waste plastics stream is converted into a molten oligomeric stream with a weight average molecular weight of 5,000 to 10,000 g/mol, which is then processed to produce naphtha-range hydrocarbons, allowing for the creation of chemical and polymer products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct reuse of sorted waste plastics is implemented, then material circularity is improved for high-quality streams, but the majority of mixed waste plastics cannot be utilized and must be incinerated
Solution Approach 1:
The patent applies parameter changes by transforming the physical and chemical state of waste plastics through thermal processing. The waste plastics are heated to high temperatures (400-800°C) in the furnace, causing depolymerization and conversion into hydrocarbon liquids and gases. This fundamental parameter change enables the processing of mixed waste plastics that cannot be directly reused, converting them into usable chemical feedstocks.
Solution Approach 2:
The patent utilizes phase transitions in the conversion process. Waste plastics transition from solid state through melting to liquid state, then through thermal decomposition to generate hydrocarbon liquids and gases. The fractionation tower subsequently separates these products based on their different boiling points, achieving separation through phase transition-based distillation.
2Device complexity
If existing refinery assets are utilized for waste plastic conversion, then device complexity is reduced, but the process requires significant energy input for high-temperature heating
Solution Approach 1:
The patent applies universality by adapting existing refinery assets for a new function. The furnace, fractionation tower, and other refinery equipment originally designed for crude oil processing are repurposed to handle waste plastics. This multi-functional use of existing infrastructure reduces device complexity and avoids the need for dedicated waste plastic processing facilities.
Solution Approach 2:
The patent converts the harmful aspect of waste plastics (which would otherwise be incinerated) into a beneficial product (hydrocarbon feedstocks). The high-temperature heating that consumes energy is transformed into a useful depolymerization process, converting unwanted waste material into valuable chemical products that can be reused in polymer production.
3Adaptability or versatility
If chemical recycling through depolymerization is implemented, then adaptability to mixed waste streams is improved, but manufacturing precision of hydrocarbon products may be affected by batch variation
Solution Approach 1:
The patent applies segmentation by dividing the complex mixture of depolymerized plastics into separate fractions based on their boiling points. The fractionation tower separates the hydrocarbon products into different cuts (light ends, naphtha, gas oil, residue), each with more uniform composition. This segmentation approach allows the process to handle variable feedstock composition while producing consistent, specification-grade products.
Solution Approach 2:
The patent implements feedback through the recycling of the bottoms stream from the fractionation tower back to the furnace inlet. This unreacted material is reprocessed in the next batch, ensuring complete conversion and reducing the impact of batch-to-batch variations. The feedback loop helps maintain product consistency despite variations in feedstock composition.
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 process enables the conversion of a wide variety of waste plastics into valuable chemical products, increasing the production of naphtha-range hydrocarbons that can be used to produce new polymer products, thereby enhancing material circularity and reducing the material footprint.
Implementation Method 1
converted into a molten oligomeric stream (L) having a weight average molecular weight of less than 100,000 g/mol, preferably between 5,000 and 50,000 g/mol
Implementation Method 2
a furnace (2), one or more coke drum(s) (3), and a pre-reactor (4), configured so that a bottoms stream (A) from the fractionation tower is mixed with a stream originating from waste plastics (L), and supplied to the furnace
Implementation Method 3
a fractionation tower (1), configured so that a bottoms stream (A) from the fractionation tower is mixed with a stream originating from waste plastics (L)
Implementation Method 4
the product stream from the furnace (C) is supplied to a coke drum
Data Source
AI summary
A process for production of chemical feedstocks from waste plastics, the process comprising providing a process configuration comprising a fractionation tower (1), a furnace (2), one or more coke drum(s) (3), and a pre-reactor (4), configured so that a bottoms stream (A) from the fractionation tower is mixed with an oligomeric stream (L) and supplied to the furnace, the product stream from the furnace (C) is supplied to a coke drum, and an overhead stream (D) from the coke drum is supplied back to the fractionation tower; wherein the oligomeric stream (L) is obtained as product stream from conversion of a waste plastics stream (B) in the pre-reactor, and has a weight average molecular weight of between 5,000 and 10,000 g/mol. Such process allows for the conversion of a wide variety of waste plastics into valuable chemical products.