Butene Separation via Decanter Phase Split and Heat Integration
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Solution Overview
Problem
The separation of butenes from C4 hydrocarbon streams containing butanes using extractive distillation faces challenges such as the occurrence of a second liquid phase and foaming issues in the absorber, which complicates the separation process and reduces efficiency, and requires effective energy recovery to maintain economic viability.
Innovation Solution
The process involves partial vaporization of the C4 hydrocarbon stream and contact with a solvent in an absorber with multiple packed beds, followed by heat integration to optimize energy use, where the solvent's heat is utilized for preheating and evaporation, and a decanter is used to separate liquid phases, with the heavy phase returned to the absorber and the light phase managed separately to prevent foaming and enhance separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high n-butane content reflux is fed into the backwash zone to prevent solvent from passing overhead, then solvent retention is improved, but the occurrence of a second liquid phase and foaming problems increase
Solution Approach 1:
A decanter is introduced as an intermediary device between the absorber and the backwash zone. The decanter separates the reflux stream into two liquid phases, removing the solvent-rich heavy phase before it enters the backwash zone. This mediator prevents the harmful interaction between high n-butane content and solvent that causes second liquid phase formation and foaming, while still maintaining effective solvent retention in the absorber.
2Use of energy by moving object
If heat integration is implemented to utilize hot solvent energy, then energy efficiency is improved, but the temperature control complexity increases
Solution Approach 1:
The process utilizes the natural temperature gradient created by the hot solvent from the desorber to heat the feed stream and the solvent entering the absorber. By arranging heat exchangers to capture and redistribute this thermal energy throughout the process, the system achieves energy efficiency without requiring additional external heating sources or complex temperature control systems. The hot solvent's thermal energy is effectively recycled to maintain temperatures at critical points in the process.
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 effectively reduces the likelihood of second liquid phase formation and foaming, improving separation efficiency and optimizing energy use through heat integration, resulting in a more efficient and economically viable butene-butane separation process.
Implementation Method 1
the butenes are preferentially dissolved in the solvent, and the butanes are separated as the overhead product
Implementation Method 2
the loaded solvent is then freed of the butenes in a stripping column, the desorber, at elevated temperature
Implementation Method 3
the heat of the solvent is used in at least one heat exchanger for preheating the loaded solvent fed to the desorber, for evaporation in the absorber evaporator and for evaporation of the liquid C4 hydrocarbon stream
Implementation Method 4
at least a portion of a liquid phase is removed at the liquid distributor above the first or second packed bed and separated in a decanter into a heavy liquid phase and a light liquid phase
Implementation Method 5
At least partially evaporating the liquid C4 hydrocarbon stream in a feed evaporator, feeding the gaseous C4 hydrocarbon stream
Data Source
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AI summary
The invention relates to a method for separating butenes from C4 hydrocarbon streams containing butanes as well as butenes by means of extractive distillation with a suitable solvent. The method according to the invention is characterised by heat integration which makes it possible to use the heat of the solvent in order to heat various streams.