Recovery Column Temperature Zones for Acrylonitrile Purity
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Solution Overview
Problem
Existing methods for separating acrylonitrile from acetonitrile mixtures are inefficient in achieving high purity and yield, particularly in the recovery column stage, due to incomplete separation and residual impurities.
Innovation Solution
A recovery column process is employed with controlled temperature zones and an internal vertical baffle to form an acrylonitrile-water azeotrope, allowing for the separation of acrylonitrile-water azeotrope, crude acetonitrile, and sidestreams with specific compositions, using solvent water and temperature control to optimize separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional extractive distillation is used in the recovery column, then acetonitrile can be removed from the aqueous solution, but the separation is incomplete and residual impurities remain in the product streams
Solution Approach 1:
The recovery column is divided into three distinct temperature zones (top portion: 55-80°C, middle section: 65-85°C top/100-120°C bottom, bottom section: 105-125°C), each performing a specific separation function. This segmentation allows different vapor-liquid equilibrium conditions in each zone, enabling complete separation of acrylonitrile, acetonitrile, and water without requiring multiple columns or complex purification stages.
Solution Approach 2:
The invention changes the temperature parameter across different sections of the recovery column to optimize separation. By maintaining specific temperature ranges in each zone, the process exploits differences in volatility and azeotrope formation behavior of the components, achieving complete separation that conventional isothermal distillation cannot accomplish.
2Manufacturing precision
If the recovery column operates at uniform temperature, then the process is simpler to control, but separation efficiency and product purity are reduced
Solution Approach 1:
The temperature control system is segmented into three independent zones with specified temperature ranges. Each zone can be controlled separately, allowing optimization of separation in each section without requiring complex coordinated control of the entire column. The top portion (55-80°C) handles acrylonitrile enrichment, the middle section (65-85°C/100-120°C) performs intermediate separation, and the bottom section (105-125°C) completes the separation, achieving high purity with manageable control complexity.
3Productivity
If conventional separation methods are used, then the process design is simpler, but the yield and purity of acrylonitrile recovery are insufficient
Solution Approach 1:
The recovery column incorporates an internal vertical baffle that segments the column interior, creating distinct flow paths for vapor and liquid phases. This structural segmentation enhances mass transfer efficiency and ensures complete separation of components, maximizing acrylonitrile recovery yield while maintaining a relatively simple single-column design without multiple side draws or complex internal configurations.
Solution Approach 2:
By implementing specific temperature ranges in each zone and controlling the azeotrope formation conditions, the process optimizes vapor-liquid equilibrium to maximize acrylonitrile recovery. The temperature gradient enables complete separation that achieves high yield (90% or greater) while avoiding the need for multiple columns or complex purification trains.
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
The process achieves an overhead stream with 0.05% or less acetonitrile, a bottoms stream with minimal acetonitrile, and a sidestream with 5-70% acetonitrile, enhancing the purity and yield of acrylonitrile recovery.
Implementation Method 1
contacting the mixture of acrylonitrile and acetonitrile with aqueous solvent to provide an acrylonitrile-water azeotrope
Implementation Method 2
This column removes acetonitrile from the aqueous solution through extractive distillation
Implementation Method 3
maintaining a temperature of 55 to 80 °C in a top portion of a top section of the recovery column; maintaining a temperature of 65 to 85 °C in a top portion of a middle section of the recovery column and a temperature of 100 to 120 °C in a bottom portion of the middle section of the recovery column
Implementation Method 4
The aqueous solution then proceeds to a recovery column. This column removes acetonitrile from the aqueous solution through extractive distillation
Data Source
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AI summary
A process for separating acrylonitrile from a mixture of acrylonitrile and acetonitrile includes providing a mixture of acrylonitrile and acetonitrile to a recovery column; contacting the mixture of acrylonitrile and acetonitrile with aqueous solvent to provide an acrylonitrile-water azeotrope; and separating the acrylonitrile-water azeotrope from the acetonitrile to provide an overhead stream that includes the acrylonitrile-water azeotrope and about 0.05 weight percent or less acetonitrile, a bottoms stream that includes about 0 to about 0.0075 weight percent acetonitrile, and a sidestream that includes about 5 to about 70 weight % acetonitrile.