Raffinate-2 Refining via Segmented Distillation and Pressure Optimization
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Solution Overview
Problem
The separation of 1-butene from raffinate-2 streams is challenging due to its similar boiling point with isobutene, making it difficult to achieve high purity and yield in the refining process, especially when the isobutene/1-butene ratio is high, which complicates the design of the refinement process and can lead to manufacturing issues.
Innovation Solution
A method involving a two-stage distillation process where the raffinate-2 is fed into a first distillation column to separate n-butane and 1-butene, with the 1-butene fraction then being fed into a second distillation column divided by a separation wall, allowing direct feeding without condensation, and utilizing heat exchangers to optimize energy efficiency and reflux streams to enhance separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation is used to separate 1-butene from raffinate-2, then separation can be achieved, but energy consumption is high and separation efficiency is low due to similar boiling points
Solution Approach 1:
The distillation column is divided into two separate columns (first distillation column and second distillation column) with different functions. The first column separates n-butane from 1-butene, while the second column separates 1-butene from isobutane. This segmentation allows each column to be optimized for its specific separation task, improving overall separation efficiency and reducing energy consumption compared to a single conventional distillation column.
Solution Approach 2:
The patent changes the operating parameters of the distillation process by operating the first distillation column at a higher pressure (6.0-8.0 atm) compared to the second column (3.0-5.0 atm). This parameter change exploits the different pressure dependencies of the relative volatilities of the components, enabling more efficient separation at each stage and reducing the total energy requirement.
2Manufacturing precision
If conventional distillation with condensation is used, then separation is achieved, but energy efficiency is reduced due to heat loss and additional cooling requirements
Solution Approach 1:
The patent implements preliminary cooling of the overhead stream from the first distillation column before it enters the second distillation column, but avoids complete condensation. This preliminary action prepares the stream for the next separation stage while retaining the energy that would be lost in full condensation, thereby improving overall energy efficiency.
Solution Approach 2:
The overhead stream from the first distillation column is continuously fed to the second distillation column without complete condensation, maintaining the vapor phase continuity. This allows the separation process to continue efficiently through both columns without the energy-intensive condensation and re-vaporization cycles that would occur in conventional stepped distillation.
3Adaptability or versatility
If separation process is designed for high isobutene/1-butene ratio, then separation capability is tested, but manufacturing difficulty increases and product quality may be compromised
Solution Approach 1:
The two-column distillation system is specifically designed to handle high isobutene/1-butene ratios by segmenting the separation into two distinct stages. The first column removes n-butane, and the second column, operating at lower pressure, is optimized to separate 1-butene from isobutane even when isobutene concentration is high. This segmented approach makes the process adaptable to varying feed compositions while maintaining manufacturing feasibility.
Solution Approach 2:
The patent uses parameter changes, specifically operating the second distillation column at lower pressure (3.0-5.0 atm) compared to the first column, to enhance the separation capability when dealing with high isobutene/1-butene ratios. This pressure parameter change adjusts the relative volatilities to favor 1-butene separation even in challenging feed conditions, maintaining both adaptability and ease of manufacture.
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 maximizes energy efficiency, allowing for the recovery of 1-butene with a purity of 99.0% or more and a yield of 80% or more, while reducing external heat supply and energy consumption, effectively addressing the separation challenges.
Implementation Method 1
feeding a raffinate-2 containing n-butane, isobutane, and 1-butene to a first distillation column; obtaining a heavy raffinate-3 containing n-butane from a lower part of the first distillation column and an upper part fraction containing 1-butene from an upper part of the first distillation column
Implementation Method 2
feeding the upper part fraction containing 1-butene to a second distillation column; and recovering a lower part fraction rich in 1-butene from a lower part of the second distillation column and a light raffinate-3 containing isobutane from an upper part of the second distillation column
Implementation Method 3
sending a portion of the compressed light raffinate-3 to a first heat exchanger of the lower part of the first distillation column, and heat-exchanging the portion of the compressed light raffinate-3 with the lower part fraction of the first distillation column
Data Source
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AI summary
Provided is a method of separating and refining 1-butene with a high purity and a high yield from a raffinate-2 stream, and recovering the refined 1-butene with a high purity and a high yield while maximizing an energy saving rate by using a high efficiency distillation column installed with a separation wall.