Evaporator Design for Acetic Acid Catalyst Management
Solution Overview
Problem
The carbonylation process for producing acetic acid faces challenges in preventing catalyst precipitation and accumulation in the evaporator, which affects productivity and safety operations.
Innovation Solution
A method involving a specific evaporator design with an inverted truncated conical cylindrical connection portion and a vortex breaker, along with a carbon monoxide-containing gas introduction, to manage catalyst precipitation and accumulation, ensuring efficient recycling and maintaining catalyst concentration in the reaction vessel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional evaporator design is used to separate reaction mixture into vapor and residual liquid streams, then acetic acid can be efficiently produced from inexpensive raw materials, but catalyst precipitation and accumulation occur in the evaporator
Solution Approach 1:
The evaporator incorporates an inverted truncated conical cylindrical connection portion with a specific inclination angle (5° to 85°) that creates curved surface geometry. This curvature prevents catalyst particles from settling and accumulating by directing flow along the sloped surface back into the reaction vessel, thereby maintaining catalyst stability while preserving production efficiency
Solution Approach 2:
The evaporator body is segmented into distinct functional zones: an upper cylindrical portion for vapor separation, a lower cylindrical portion for liquid collection, and an inverted truncated conical connection portion that acts as a transition zone. This segmentation allows each zone to perform its specific function while the conical portion specifically addresses catalyst precipitation by directing residual liquid back to the reaction vessel
2Device complexity
If the evaporator operates without special catalyst prevention structures, then the process is simple and inexpensive, but catalyst concentration varies in the reaction vessel affecting safety operation
Solution Approach 1:
The inverted truncated conical connection portion introduces a geometric feature that is relatively simple to manufacture but effectively prevents catalyst accumulation. The inclination angle design creates a self-cleaning effect where catalyst-laden residual liquid is directed back to the reaction vessel, maintaining safe operational conditions without complex control systems
Solution Approach 2:
The evaporator design changes the geometric parameters of the connection portion (inclination angle between 5° to 85°, diameter ratios between upper and lower portions) to optimize catalyst flow characteristics. These parameter changes create appropriate flow velocity and direction to prevent catalyst deposition while maintaining operational simplicity
3Productivity
If catalyst recycle rate is increased to maintain catalyst concentration, then productivity is improved, but catalyst accumulation in the evaporator worsens
Solution Approach 1:
The inverted truncated conical connection portion with its specific inclination angle creates a flow pattern that prevents catalyst accumulation during the recycle process. As residual liquid flows through this conical section, catalyst particles are directed back into the reaction vessel rather than accumulating in the evaporator, enabling sustained high-rate catalyst recycling
Solution Approach 2:
The evaporator design ensures continuous catalyst recycle by preventing accumulation that would otherwise interrupt the recycle flow. The conical connection portion maintains uninterrupted flow of catalyst-laden residual liquid back to the reaction vessel, sustaining continuous productive 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 significantly suppresses catalyst precipitation and accumulation, maintaining stable catalyst concentration, thereby enhancing acetic acid productivity and ensuring safe operation.
Implementation Method 1
an inverted truncated conical cylindrical connection portion which joins the upper cylindrical portion and the lower cylindrical portion
Implementation Method 2
a linear velocity r of the residual liquid stream passing through a gap between the circumferential end of the vortex breaker main body and the inside bottom surface of the evaporator bottom part is larger than 10 m/h
Implementation Method 3
a vortex breaker comprising a plate-like vortex breaker main body and a leg which horizontally supports the vortex breaker main body
Implementation Method 4
a linear velocity r of the residual liquid stream passing through a gap between the circumferential end of the vortex breaker main body and the inside bottom surface of the evaporator bottom part is larger than 10 m/h
Implementation Method 5
a technique of improving the stability of carbon monoxide and a complex of an iodide ion and a metal is known which involves introducing a carbon monoxide-containing gas to the bottom of an evaporator to increase a CO partial pressure or the amount of CO dissolved in an evaporator bottom fraction
Implementation Method 6
an evaporation step of separating the reaction mixture obtained in the carbonylation reaction step into a vapor stream and a residual liquid stream in an evaporator
Implementation Method 7
a distillation step of distilling the vapor stream to purify acetic acid
Data Source
Figure 1
Figure 2~3
AI summary
Provided is a method for producing acetic acid, which suppresses catalyst precipitation and accumulation in an evaporator, can efficiently recycle catalysts to a reaction vessel, and can contribute to maintenance and improvement in acetic acid productivity and securing of safety operation. In the method, the evaporator has a catalyst precipitation and accumulation prevention structure: (a) structure where inclination angle θ of inside wall surface of an inverted truncated conical cylindrical connection portion is 5° to 85°; and/or (b) structure where a vortex breaker comprising a plate-like vortex breaker main body and a leg is disposed such that the vortex breaker main body covers right above the connection portion of an evaporator bottom part to a residual liquid stream recycle line, and linear velocity r of the residual liquid stream passing through a gap between the vortex breaker main body and the evaporator bottom part is larger than 10 m/h.