Vinyl Acetate Separation Process Energy Reduction
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Solution Overview
Problem
Current processes for producing vinyl acetate from ethylene and acetic acid over palladium-based catalysts face inefficiencies due to high energy expenditure in separating ethyl acetate and water, with significant amounts of dissolved gases in recycle streams requiring costly compression and corrosion-resistant equipment to handle acetic acid.
Innovation Solution
A process involving a first distillation column for cooling and separating gas mixtures, followed by a washing column with aqueous acetic acid to isolate vinyl acetate, and subsequent distillation columns to recycle and separate ethyl acetate, reducing energy consumption and corrosion risks by recycling heated acetic acid and optimizing reflux ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multi-stage distillation processes are used to separate vinyl acetate from reaction products, then vinyl acetate purification is achieved, but energy consumption increases significantly
Solution Approach 1:
The distillation process is divided into multiple stages with different functions: a first distillation column for initial separation and water removal, and a second distillation column for final vinyl acetate purification. This segmentation allows each column to be optimized for its specific separation task, reducing the overall energy requirement compared to a single comprehensive distillation system.
Solution Approach 2:
The first distillation column performs preliminary separation by removing water and other components before the second column handles the final vinyl acetate purification. This preliminary action reduces the load on the second column and minimizes the total energy consumption by addressing separations in a logical sequence rather than attempting all separations simultaneously.
2Productivity
If conventional gas recycling processes are used, then unreacted ethylene is returned to the reactor, but compression energy expenditure increases due to dissolved gases
Solution Approach 1:
Dissolved gases are extracted from the recycle gas stream using a scrubbing column where the gas is contacted with a liquid absorbent. This removal of dissolved gases before compression significantly reduces the energy required by the recycle gas compressor while maintaining high ethylene conversion efficiency through effective gas recycling.
3Manufacturing precision
If acetic acid is used in large quantities for washing and scrubbing, then vinyl acetate separation efficiency improves, but corrosion of equipment increases
Solution Approach 1:
The concentration and temperature parameters of the acetic acid solution are optimized to achieve effective vinyl acetate separation while minimizing corrosion. By controlling the acetic acid concentration within specific ranges and adjusting temperature parameters, the process maintains high separation efficiency while reducing the corrosiveness of the acetic acid solution toward equipment.
4Manufacturing precision
If traditional ethyl acetate separation methods are used, then ethyl acetate is removed from vinyl acetate, but the process requires corrosive-resistant equipment and high energy input
Solution Approach 1:
The separation process is segmented into distinct functional units: the first distillation column handles water and heavy component removal, while the second distillation column specifically addresses ethyl acetate separation from vinyl acetate. This segmentation allows each column to be designed for its specific separation challenge, reducing the need for overly complex corrosive-resistant equipment throughout the entire system.
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 process reduces energy consumption by minimizing return gas compression needs and decreases acetic acid-related corrosion, achieving efficient separation of vinyl acetate while lowering operational costs and equipment demands.
Implementation Method 1
a) the gas mixture exiting from the reaction zone is fed into a first distillation column
Implementation Method 2
b) the gas mixture exiting at the top of the first distillation column is cooled to -20 to +50°C, the resulting condensate separating into a water phase and an organic phase
Implementation Method 3
e) the non-condensed gas containing vinyl acetate in step b) is washed in a washing column with at least 90% aqueous acetic acid and a vinyl acetate-containing, acetic acid solution is thereby obtained at the bottom
Implementation Method 4
b) the gas mixture exiting at the top of the first distillation column is cooled to -20 to +50°C
Implementation Method 5
g) the liquid obtained during the expansion in step f) to a second distillation column and withdraws an ethyl acetate-containing side stream from an enrichment zone above its bottom
Data Source
Figure 1
AI summary
The separation of vinyl acetate from a gas mixture, comprises feeding the mixture left from a reaction zone into a first distillation column, cooling down (-20 to + 50[deg]C) the mixture discharged at the column head to form a first condensate separated into water phase (42) and first organic phase (44), and removing the water phase. The gas mixture from the zone is cooled down in a counter-current heat exchanger (9) with a colder cycle gas to 115-150[deg]C. The first organic phase as feedback is totally/partly fed back to the column head. The separation of vinyl acetate from a gas mixture, comprises feeding the mixture left from a reaction zone into a first distillation column, cooling down (-20 to + 50[deg]C) the mixture discharged at the column head to form a first condensate separated into water phase (42) and first organic phase (44), and removing the water phase. The gas mixture from the zone is cooled down in a counter-current heat exchanger (9) with a colder cycle gas to 115-150[deg]C. The first organic phase as feedback is totally or partly fed back to the column head, and a part of the organic phase not used as feedback is removed. The gas mixture is formed in a gas phase during a reaction of ethylene with acetic acid and oxygen at a catalyst containing palladium or palladium compounds. A gas containing non-condensed vinyl acetate is washed in a washing column with aqueous acetic acid (90%) to obtain the acid containing the vinyl acetate at a sump. The sump product containing vinyl acetate, ethyl acetate, acetic acid and water, is supplied to a collecting tank (14), and a liquid is primarily relaxed at 0.1-0.15 MPa to from a gas. The relaxed liquid is supplied to a second distillation column to remove a side stream containing ethyl acetate from an enrichment zone above the sump of the column. The removed side stream is totally or partly used for the gas washing in the washing column. A head vapor removed from the side stream is cooled down to form second condensate separated into water and second organic phases, and the water phase is removed. A part of the second organic phase is fed back to the head of the second distillation column, and the non-fed back second organic phase is removed. A part of the acetic acid solution containing the vinyl acetate is cooled through a pumping (15) in a closed cycle and the cooled solution is fed back to the sump of the washing column. The uncooled solution is heated at 60-100[deg]C and the heated solution is delivered to 5 t>h to 10 t>h column plates of the first distillation column bottom. The sump discharge of the first distillation column exhibits a temperature of 80-150[deg]C. The first non-fed back organic phase is secondarily relaxed at 0.1- 0.15 MPa in relaxation container (56) to from a gas combined with the gas from the primary relaxation. The head vapor of the second distillation contains acetic acid and ethyl acetate. The secondarily relaxed organic phase is combined with the second fed-back organic phase in a phase separator containing ethyl acetate. A part of the non-fed back second organic phase removed is directed into a third distillation column (48). A head product of the third distillation column is cooled down to form low boiling fraction and water. A sump product of the third distillation column is directed into a fourth distillation column to remove the pure vinyl acetate at the fourth distillation column head.