Mixed Plastic Pyrolysis Steam Cracking for Olefin Yield

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Solution Overview

Problem

Conventional pyrolysis processes for converting waste plastics into high-value chemicals like olefins and aromatic hydrocarbons produce a wide variety of by-products, necessitating the development of methods to minimize these by-products and enhance the yield of desired chemicals.

Innovation Solution

A process involving the conversion of mixed plastics into hydrocarbon products in a pyrolysis unit, followed by separation into gas and liquid phases, with subsequent cracking in gas and liquid steam crackers, and recycling of fractions to optimize the production of olefins and aromatic hydrocarbons, while minimizing by-products.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional pyrolysis processes are used to convert waste plastics to high-value chemicals, then the process is simple and easy to operate, but the product stream contains a wide variety of by-products and the yield of desired chemicals is limited

Engineering Contradiction:

Improveyield of high-value chemicalsVSAvoidby-product formation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent divides the pyrolysis process into multiple stages with different temperature zones and residence times. The process segments the product stream into gas phase and liquid phase components, which are then processed separately through steam cracking to maximize olefin yield while minimizing by-products.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs parameter changes by controlling temperature, pressure, and residence time in different reaction zones. By optimizing these parameters in the pyrolysis and steam cracking stages, the process enhances olefin production while reducing unwanted by-products through precise control of reaction conditions.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the hydrocarbon liquid stream is fully processed through steam cracking to increase olefin yield, then the productivity of high-value chemicals improves, but the process complexity and equipment requirements increase

Engineering Contradiction:

Improveolefin productionVSAvoidprocess configuration

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies partial action by processing only a portion of the hydrocarbon liquid stream through steam cracking. The liquid stream is separated into fractions, with the lighter fraction (boiling point <300°C) being steam-cracked to produce olefins, while heavier fractions are recycled or processed separately, thereby reducing equipment complexity while maintaining high olefin yield.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If the hydrocarbon product is separated into gas and liquid phases and processed through different cracking units, then the selectivity for desired chemicals improves, but the equipment investment and operational complexity increase

Engineering Contradiction:

Improveproduct selectivityVSAvoidnumber of processing units

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent employs multi-functionality by using steam cracking technology to process both gas phase and liquid phase hydrocarbon streams. The same steam cracking principle is applied to both phases, allowing a single type of cracking technology to serve multiple functions and improve product selectivity without requiring fundamentally different equipment for each stream.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 increases the yield of high-value chemicals such as olefins and C6-C8 aromatics by effectively separating and recycling fractions, thereby reducing by-product formation and enhancing the efficiency of chemical production.

Implementation Method 1

converting mixed plastics to a hydrocarbon product in a pyrolysis unit

Methodology Applied

Scientific EffectPyrolysis: Pyrolysis

Implementation Method 2

feeding at least a portion of the hydrocarbon gas stream to a gas steam cracker to produce a gas steam cracker product stream

Methodology Applied

Scientific EffectSteam cracking: Pyrolysis

Implementation Method 3

feeding at least a portion of the first fraction of the hydrocarbon liquid stream to a liquid steam cracker to produce a liquid steam cracker product stream

Methodology Applied

Scientific EffectSteam cracking: Pyrolysis

Data Source

PatentUS10927315B2Maximizing high-value chemicals from mixed plastic using different steam-cracker configurations

Publication Date: 2021.02.23 SABIC GLOBAL TECHNOLOGIES BV

AI summary

A process for producing olefins and aromatics comprising converting plastics to a hydrocarbon product comprising a gas phase and a liquid phase in a pyrolysis unit; separating the hydrocarbon product into a hydrocarbon gas stream comprising the gas phase and a hydrocarbon liquid stream comprising the liquid phase; feeding the hydrocarbon gas stream to a gas steam cracker to produce a gas steam cracker product comprising olefins, wherein an olefins amount in the gas steam cracker product is greater than in the hydrocarbon gas stream; separating the hydrocarbon liquid stream into a first fraction (b.p.<300° C.) and a second fraction (b.p>300° C.); feeding the first fraction to a liquid steam cracker to produce a liquid steam cracker product comprising olefins and aromatics, wherein an olefins amount in the liquid steam cracker product is greater than in the first fraction; and recycling the second fraction to the pyrolysis unit.