Selective Butene Extraction via Extractive Distillation
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Solution Overview
Problem
The separation of butenes and butanes using extractive distillation with polar solvents often results in high water concentrations in the butene product and potential formation of separate hydrocarbon and aqueous phases, reducing separation efficiency due to their close boiling points.
Innovation Solution
A process involving an extractive distillation column with a lean solvent mixture of water and polar solvents, followed by a stripper with a wash section and reflux system, where condensed overheads are phase-separated and make-up water is refluxed, preventing the formation of separate phases and improving heat integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polar solvents are used for extractive distillation to separate butenes and butanes, then separation efficiency is improved, but water concentration in the butene product increases
Solution Approach 1:
A wash section is introduced as an intermediary zone between the stripping section and the overhead condenser. This wash section uses a polar solvent wash stream to selectively remove water from the vapor phase without significantly removing butenes, thereby reducing water concentration in the final product while maintaining separation efficiency
Solution Approach 2:
The process changes the concentration parameters by controlling the water content in the polar solvent feed to specific ranges (5-50 wt% water for the extractive distillation column, 10-60 wt% water for the stripper). By optimizing these parameter ranges, the system achieves effective separation while minimizing water carryover into the butene product
2Manufacturing precision
If polar solvent mixtures are used in extractive distillation, then separation of butenes and butanes is achieved, but separate hydrocarbon and aqueous phases may form on trays or packing, reducing separation efficiency
Solution Approach 1:
The process maintains phase homogeneity by controlling the water content parameter within specific ranges (5-50 wt% for extractive distillation column, 10-60 wt% for stripper). These parameter controls ensure the polar solvent mixture remains in a homogeneous liquid phase throughout the extraction and stripping sections, preventing separate phase formation that would reduce separation efficiency
Solution Approach 2:
The system performs preliminary phase stabilization by pre-mixing the polar solvent with controlled amounts of water before introducing it to the extractive distillation column. This preliminary action ensures the solvent mixture enters the column in a homogeneous state, preventing phase separation on the trays or packing
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 approach enhances the separation efficiency of butenes and butanes, reduces solvent losses, and achieves a superior butene product with lower solvent concentrations, leading to lower operating expenses and capital costs by maintaining a continuous aqueous phase and optimizing heat recovery.
Implementation Method 1
separating butenes and butanes by extractive distillation using a polar solvent
Implementation Method 2
contacting a hydrocarbon mixture comprising butanes and butenes with a lean solvent mixture comprising water and one or more polar solvents
Implementation Method 3
feeding the bottoms fraction to a stripper comprising a stripping section and a wash section to separate the butenes from the solvent mixture
Implementation Method 4
condensing the overheads fraction to form a water fraction and a product butenes fraction
Data Source
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AI summary
A process and system for separating butenes and butanes by extractive distillation using a polar solvent is disclosed. The process may include: contacting a hydrocarbon mixture including butanes and butenes with a lean solvent mixture in an extractive distillation column to form an enriched solvent fraction comprising butenes; recovering an overheads fraction comprising butanes and a bottoms fraction from the extractive distillation column; feeding the bottoms fraction to a stripper including a stripping section and a wash section; recovering the lean solvent mixture as a bottoms fraction and a stripper overheads fraction comprising butenes and water from the stripper; condensing the overheads fraction to form a water fraction and a product butenes fraction; feeding water as reflux to a top of the stripper wash section; feeding at least a portion of the condensed water fraction intermediate the top and bottom of the stripper wash section as a second reflux.