Aliphatic Hydrocarbon Recovery via Solvent Extraction and Demixing
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Solution Overview
Problem
Existing processes for recovering aliphatic hydrocarbons from waste plastics are energy-intensive, capital-intensive, and suffer from yield loss, fouling, and contamination issues due to heteroatom-containing organic compounds and salts, which negatively impact steam cracker efficiency.
Innovation Solution
A process involving a washing step with a heteroatom-containing solvent to remove contaminants, followed by liquid-liquid extraction with a heteroatom-containing solvent and a demixing solvent to separate aliphatic hydrocarbons, reducing the need for hydrotreating and minimizing downstream contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard distillation is used to separate contaminants from recycle water and NMP, then separation is achieved, but energy consumption increases and contaminant build-up occurs
Solution Approach 1:
The patent changes the separation mechanism from thermal distillation to liquid-liquid extraction by modifying the chemical parameters of the system. Extraction solvents with specific polarity characteristics are selected to selectively extract heteroatom-containing contaminants from the hydrocarbon stream, achieving separation without the high energy input required for distillation
Solution Approach 2:
The patent introduces extraction solvents as intermediary substances that mediate the separation process. These solvents temporarily bind to heteroatom-containing contaminants through solvation, enabling selective separation from aliphatic hydrocarbons. The solvents are then regenerated and recycled, avoiding the energy-intensive direct heating and phase change of distillation
2Reliability
If multiple extraction steps are used to remove heteroatom-containing compounds, then contamination is reduced, but process complexity increases
Solution Approach 1:
The patent segments the extraction process into distinct functional stages: a first extraction step using a polar solvent to remove heteroatom-containing compounds, and a second extraction step using a less polar solvent to recover and purify the extraction solvent. This segmentation allows each step to be optimized for its specific function while maintaining overall process simplicity
Solution Approach 2:
The patent implements a solvent recovery strategy where the extraction solvent is discarded from the hydrocarbon stream in the first extraction step, then recovered and purified in the second extraction step. This allows the solvent to be reused multiple times, reducing the need for continuous fresh solvent addition and simplifying the overall material balance
3Reliability
If salts are present in the feedstock, then they end up in the extract stream, but fouling of distillation columns occurs
Solution Approach 1:
The patent extracts salts and other inorganic contaminants from the hydrocarbon feedstock in the first extraction step using a polar extraction solvent. These contaminants are taken out of the hydrocarbon phase and transferred to the aqueous or polar solvent phase, preventing them from entering subsequent distillation columns where they would cause fouling
Solution Approach 2:
The patent converts the potentially harmful presence of salts and heteroatom-containing compounds in the feedstock into a benefit by using their polarity differences to enable selective extraction. The contaminants that would otherwise cause fouling are precisely the substances that are most readily extracted by polar solvents, turning a problem into the basis of the separation mechanism
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 achieves efficient recovery of aliphatic hydrocarbons with low energy demand and capital expenditure, preventing fouling and contamination, and maintaining high-quality feed for steam cracking.
Implementation Method 1
liquid-liquid extraction of a stream resulting from washing step (i) which comprises aliphatic hydrocarbons, heteroatom containing organic compounds and optionally aromatic hydrocarbons, with an extraction solvent a) which contains one or more heteroatoms
Implementation Method 2
contacting a liquid stream which comprises aliphatic hydrocarbons, heteroatom containing organic compounds and optionally aromatic hydrocarbons, with a washing solvent d) which contains one or more heteroatoms thereby removing heteroatom containing organic compounds
Implementation Method 3
mixing a stream resulting from step a) which comprises extraction solvent a), heteroatom containing organic compounds and optionally aromatic hydrocarbons, with a demixing solvent b) to remove additional heteroatom containing organic compounds and optional aromatic hydrocarbons, wherein demixing solvent b) contains one or more heteroatoms and has a miscibility in heptane which is lower than the miscibility of extraction solvent a) in heptane
Data Source
AI summary
The invention relates to a process for the recovery of aliphatic hydrocarbons from a liquid stream comprising aliphatic hydrocarbons, heteroatom containing organic compounds and optionally aromatic hydrocarbons, involving (i) contacting said liquid stream with a washing solvent thereby removing heteroatom containing organic compounds; a) liquid-liquid extraction of the washed stream with an extraction solvent; b) mixing the extract stream, comprising extraction solvent, heteroatom containing organic compounds and optionally aromatic hydrocarbons, with a demixing solvent to remove additional heteroatom containing organic compounds and optional aromatic hydrocarbons; and c) separation of the remaining stream into a demixing solvent stream and an extraction solvent stream. Further, the invention relates to a process for the recovery of aliphatic hydrocarbons from plastics comprising the above-mentioned process; and to a process for steam cracking a hydrocarbon feed comprising aliphatic hydrocarbons as recovered in one of the above-mentioned processes.