Liquefied Waste Polymer Processing via Steam Stripping
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Solution Overview
Problem
Processing liquefied waste polymers is challenging due to fouling issues and the presence of elemental impurities like diolefins, metals, and heteroatoms, which complicate hydrogenation and hydroprocessing, especially in crude oil distillation units not designed for olefinic feeds.
Innovation Solution
A method involving a steam stripper to separate a distillate comprising diolefins and naphtha, followed by hydrotreatment to reduce diolefins and subsequent hydroprocessing to produce hydrogenated naphtha fractions suitable for steam crackers, and co-processing with crude oil to alleviate fouling and impurity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LWP is processed in crude oil distillation units, then distillation can be performed, but diolefins cause problems in downstream hydrogenation processes
Solution Approach 1:
The process segments the LWP stream into different fractions based on boiling point ranges. A steam stripper separates lighter components (distillate) from heavier components (bottoms), allowing selective processing of diolefin-containing fractions before they reach downstream hydrogenation units. This segmentation prevents problematic diolefins from entering crude oil distillation units while still enabling effective distillation of suitable fractions.
Solution Approach 2:
The steam stripper extracts and removes diolefin-containing light fractions from the LWP stream. By taking out the problematic diolefin components in the distillate phase, the process prevents these compounds from causing fouling and catalyst deactivation in downstream hydrogenation processes, while the stripped bottoms can be processed separately.
2Adaptability or versatility
If LWP contains elemental impurities like nitrogen, oxygen, sulphur and chlorine, then the feed source is expanded, but these impurities have detrimental effect on direct utilization
Solution Approach 1:
The process performs preliminary removal of heteroatom impurities through the steam stripping operation before the LWP enters downstream processing units. By removing volatile impurities like nitrogen, oxygen, sulphur and chlorine compounds in the distillate phase, the process protects downstream catalysts and equipment from deactivation and fouling, enabling broader feed source acceptance.
Solution Approach 2:
The steam stripper acts as an intermediary unit between the LWP feed and downstream processing equipment. It mediates the harmful effects of heteroatom impurities by separating and removing them in the vapor phase, allowing the liquid bottoms to proceed to further processing without the detrimental effects of these impurities.
3Adaptability or versatility
If LWP contains significant amounts of olefins and aromatics, then the feed composition is complex, but these components lead to polymerization and coking at elevated temperatures
Solution Approach 1:
The steam stripper extracts olefin-containing components into the distillate phase, removing them from the liquid bottoms stream. This extraction prevents olefins and aromatics from reaching elevated temperature processing units where they would cause polymerization and coking, while still allowing the process to handle complex feed compositions.
Solution Approach 2:
The process performs preliminary removal of polymerization-prone components (olefins and aromatics) through steam stripping before the remaining liquid enters high-temperature processing units. This preliminary action prevents the formation of coke and polymers that would otherwise occur at elevated temperatures, protecting downstream equipment and catalysts.
4Object-affected harmful factors
If a steam stripper is used to separate naphtha from LWP, then fouling problems are avoided, but additional processing steps are required
Solution Approach 1:
The process uses a steam stripper to segment the LWP into distillate (containing fouling-prone components) and bottoms (cleaner fraction). This segmentation effectively reduces fouling in downstream processing by isolating problematic components in a separate stream that can be handled differently or removed, justifying the addition of the stripping step.
Solution Approach 2:
The steam stripper converts the harmful fouling effect of diolefins and impurities into a benefit by concentrating them in the distillate phase. This allows the fouling-prone components to be removed or processed separately, while the cleaned bottoms stream proceeds to further processing with reduced fouling potential, transforming a problem into a solution.
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 method reduces fouling, extends catalyst life, and produces hydrogenated naphtha fractions that can be safely used as steam cracker feeds, while allowing co-processing with crude oil, thereby improving the efficiency and stability of downstream refinery processes.
Implementation Method 1
subjecting the LWP stream to a steam stripper to obtain a distillate comprising diolefins and naphtha, and a distillate bottom
Implementation Method 2
subjecting the distillate to hydrotreatment reaction conditions in the presence of hydrogen and one or more hydrotreatment catalysts to produce diolefin depleted distillate
Implementation Method 3
subjecting the naphtha fraction to hydroprocessing reaction conditions in the presence of hydrogen and one or more hydroprocessing catalysts
Data Source
AI summary
The present disclosure relates to methods for processing liquefied waste polymers (LWP) containing diolefins. The LWP feed is supplied to steam stripper A to provide a distillate containing diolefins and naphtha, and a distillate bottom. The distillate is subjected to hydrotreatment B to produce a diolefin depleted distillate which is separated by distillation C to give rise to one or more fractions comprising at least a naphtha fraction, an optional middle fraction and a bottom fraction. Hydroprocessing D of the naphtha fraction gives rise to hydrogenated naphtha which is suitable as a feed for a steam cracker E. Since the distillation bottom, bottom fraction and the middle distillate are predominantly free from diolefins, they can be mixed with crude oil and processed further in oil refinery.