De-ethenizer Ethylene Separation at Low Pressure
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Solution Overview
Problem
Current ethylene separation processes in propylene production are energy-intensive and costly, with inefficiencies in removing unreacted ethylene from metathesis reactions, particularly due to high operating pressures in de-ethenizers.
Innovation Solution
The process involves introducing a feed stream of ethylene and butene into a de-ethenizer for fractional distillation, operating at pressures below 2.41 MPaG, with fresh ethylene used as reflux supplement and recycling the overhead stream, compressed to optimize separation and reduce energy needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high pressure operation is used in de-ethenizer, then separation efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent changes the operating pressure parameter from conventional high pressure (2.76 MPaG or 400 psig) to lower pressure (less than 2.41 MPaG or 350 psig). This parameter change reduces energy consumption while maintaining separation efficiency through optimized fractional distillation at the lower pressure condition.
Solution Approach 2:
The patent introduces fresh ethylene as a reflux supplement, creating a copy of the ethylene component to enhance the reflux effect. This additional ethylene stream improves separation efficiency without requiring higher operating pressures, thereby reducing energy consumption.
2Measurement precision
If fresh ethylene is introduced as reflux supplement, then separation efficiency is improved, but capital cost increases
Solution Approach 1:
The fresh ethylene introduced as reflux supplement serves multiple functions: it enhances the reflux effect to improve separation efficiency, maintains the ethylene partial pressure in the column, and contributes to the overall mass balance. This multi-functionality justifies the additional capital investment by delivering multiple benefits from a single modification.
3Use of energy by moving object
If operating pressure is reduced below 2.41 MPaG, then energy consumption is reduced, but separation efficiency may deteriorate
Solution Approach 1:
The introduction of fresh ethylene as reflux supplement compensates for the reduced driving force available at lower operating pressures. The additional ethylene stream enhances the reflux effect, maintaining separation efficiency despite the lower pressure condition, thereby enabling energy reduction without sacrificing performance.
Solution Approach 2:
The patent optimizes multiple parameters simultaneously: operating pressure is reduced below 2.41 MPaG, fresh ethylene flow rate is introduced as reflux supplement, and the system is re-optimized for fractional distillation at these new conditions. This coordinated parameter change maintains separation efficiency while reducing energy consumption.
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 reduces heating requirements by up to half in metathesis reactors and de-ethenizers, while potentially offsetting capital costs through lower system pressures, enhancing the efficiency of ethylene separation and propylene production.
Implementation Method 1
separating the ethylene from the butene via fractional distillation within the de-ethenizer
Implementation Method 2
compressing the overhead stream from a first pressure to a second pressure
Implementation Method 3
condensing a portion of the overhead stream to form a recycle ethylene stream
Data Source
Figure 1~2
AI summary
Ethylene separation processes are described herein. The ethylene separation processes generally include introducing a feed stream including ethylene and butene into a de-ethenizer; and separating the ethylene from the butene via fractional distillation within the de-ethenizer to form an overhead stream including separated ethylene and a bottoms stream including separated butene, wherein the de-ethenizer operates at a pressure of less than 350 psig.