VAM Purification With Two-Stage Distillation for Ethyl Acetate Removal
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Solution Overview
Problem
Current VAM production processes face challenges in efficiently and cost-effectively reducing the amount of ethyl acetate in the finished vinyl acetate monomer product due to similar boiling behaviors, leading to high energy consumption and impurity retention.
Innovation Solution
A two-stage distillation process is implemented, where the side draw from the azeotropic distillation tower is positioned to maintain a constant water content in the bottom product, enhancing the ETAC-enriched vapor stream, which is then processed in a secondary distillation tower to separate and recover valuable components for recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If azeotropic distillation is used to purify VAM, then VAM can be separated from acetic acid and water, but ethyl acetate cannot be effectively removed due to similar boiling behavior
Solution Approach 1:
The distillation process is divided into two separate stages: first azeotropic distillation to separate VAM from acetic acid and water, then a second distillation column specifically dedicated to removing ethyl acetate. This segmentation allows each column to be optimized for its specific separation task, with the second column receiving a feed stream that is already enriched in ethyl acetate relative to other components.
Solution Approach 2:
A side stream is extracted from the azeotropic distillation column that is enriched in ethyl acetate. This side stream is then fed to a second distillation column where ethyl acetate is selectively removed. By extracting and treating the ethyl acetate-rich stream separately, the main VAM product stream is protected from contamination while ethyl acetate removal is addressed in a dedicated unit.
2Quantity of substance
If secondary distillation is implemented to remove ethyl acetate, then ethyl acetate content in VAM product is reduced, but energy consumption increases
Solution Approach 1:
The second distillation column is designed with localized optimization for ethyl acetate removal. The column configuration, including tray arrangement and reflux ratio, is specifically tailored to achieve efficient ethyl acetate separation while minimizing energy consumption. The side stream feed location is strategically positioned to maximize ethyl acetate recovery efficiency.
Solution Approach 2:
The process recovers ethyl acetate from the side stream of the azeotropic distillation column and concentrates it in the second distillation column. The ethyl acetate-rich bottom product from the second column can be discarded as waste or recovered for potential reuse, while the overhead product returns to the main VAM product stream with reduced ethyl acetate content.
3Manufacturing precision
If side draw position is optimized to maintain constant water content, then bottom product quality is improved, but process complexity increases
Solution Approach 1:
The side draw position in the azeotropic distillation column is determined based on feedback from the desired bottom product water content specification. By positioning the side draw at the appropriate tray location, the column automatically maintains the target water content in the bottom product through the natural concentration gradients established during distillation operation.
Solution Approach 2:
The azeotropic distillation column is designed with a predetermined side draw position that is calculated based on mass balance and equilibrium considerations. This preliminary design ensures that the bottom product will have the desired water content without requiring complex real-time control adjustments during operation.
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 ethyl acetate content in the VAM product, decreases energy and water consumption, and improves overall production efficiency by allowing for the recovery and recycling of valuable materials.
Implementation Method 1
This crude stream can be purified by an azeotropic distillation, between VAM and water, in the purification section of the VAM plant
Implementation Method 2
The overhead product is condensed and further separated into an organic phase containing VAM, a water phase
Implementation Method 3
an ethyl acetate enriched liquid stream is obtained as a side stream... separation of the ethyl acetate requires a high energy consumption
Data Source
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AI summary
Purification methods and systems for working up a crude vinyl acetate stream containing vinyl acetate monomer, acetic acid, water, ethyl acetate, and other impurities. Crude vinyl acetate streams are purified with an azeotropic distillation tower using a side draw to remove ethyl acetate and water, and a bottom stream to remove acetic acid from the crude vinyl acetate. The methods and systems move the side draw to a location on the azeotropic distillation tower that maintains a constant water concentration in the bottom product of about 4 to about 15 wt. % and forms a vapor side product. A second distillation tower is used to further purify the vapor side product to obtain water, VAM, ethyl acetate and AA. The system provides easier disposal of ethyl acetate, and cleaner water that can be recycled in the reactor or purification sections of a VAM plant and full recovery of AA.