Acetic Acid Production Heat Integration via Flash Evaporation
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Solution Overview
Problem
Current processes for producing acetic anhydride and acetic acid involve high heat removal under severe conditions without utilizing the heat of reaction, and there's no opportunity to sequence reactions for beneficial equilibrium shifting, leading to inefficient heat management and process challenges.
Innovation Solution
A process where methanol, water, or their mixture is added to an acetic anhydride-containing stream within a flash evaporation zone, converting some acetic anhydride to acetic acid and utilizing the reaction heat for evaporation, allowing for co-production of acetic anhydride and acetic acid under anhydrous conditions, with the reaction zone operating at elevated temperatures and pressures and the evaporation zone at reduced pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If methanol and water are fed to the carbonylation reactor to coproduce acetic acid, then acetic acid production is achieved, but the heat of reaction must be removed under severe conditions without utilization
Solution Approach 1:
The patent converts the harmful effect of excessive heat generation during coproduction into a beneficial effect by using the heat of reaction from methanol carbonylation to provide the energy needed for flash evaporation and distillation operations. The reaction heat, which previously had to be removed under severe conditions, is now utilized to drive subsequent separation processes, eliminating the need for external heating and improving overall energy efficiency.
Solution Approach 2:
The patent changes the operational parameters by sequencing the carbonylation reactions and controlling the timing of heat release. By feeding methanol and water at specific stages and controlling the carbonylation conditions, the process optimizes heat generation timing to match the energy requirements of flash evaporation and distillation, transforming heat management from a problem into an integrated energy supply system.
2Productivity
If all heat of reaction is released in a single reaction step, then acetic acid and acetic anhydride are produced, but there is no opportunity to utilize the heat directly in the production system
Solution Approach 1:
The patent segments the carbonylation process into distinct reaction stages and sequences them to control heat release timing. By dividing the overall transformation into stepwise carbonylation reactions (methyl iodide to acetyl iodide, then to acetic acid, and parallel formation of acetic anhydride), the process creates multiple heat release points that can be matched to the energy requirements of subsequent separation operations like flash evaporation and distillation.
Solution Approach 2:
The patent performs preliminary carbonylation reactions to generate heat before the flash evaporation and distillation steps. By controlling the sequence so that exothermic carbonylation reactions occur first, the process prepares the thermal energy needed for subsequent separation operations, ensuring that heat is available when required for efficient product recovery.
3Productivity
If the process operates under severe conditions with high pressure and corrosive environment, then carbonylation reactions proceed, but heat removal becomes challenging
Solution Approach 1:
The patent implements a self-service heat management system where the carbonylation reactions themselves provide the heat needed for flash evaporation and distillation. The exothermic heat of reaction, generated during carbonylation, is directly utilized to drive the separation processes without requiring external heating systems or complex heat exchange networks, thereby simplifying the overall equipment design while maintaining high productivity.
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 effectively increases the weight percent of vapor product removed by utilizing the reaction heat, improving efficiency and reducing the need for severe heat removal conditions, while allowing for beneficial shifting of reaction equilibrium.
Implementation Method 1
reacts exothermically with acetic anhydride to produce acetic acid or a mixture of acetic acid and methyl acetate and the heat of the methanol/acetic anhydride and/or water/acetic anhydride reaction
Implementation Method 2
the heat of the methanol/acetic anhydride and/or water/acetic anhydride reaction increases the weight percent of vapor product removed from the evaporation zone
Implementation Method 3
feeding a liquid carbonylation product effluent from the reaction zone to an evaporation zone comprising at least one evaporation vessel
Data Source
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AI summary
Disclosed is a process for the production of acetic acid or mixtures of acetic acid and acetic anhydride in a carbonylation process wherein a mixture comprising methyl acetate and/or dimethyl ether and methyl iodide is contacted in the liquid phase with carbon monoxide in the presence of a carbonylation catalyst at elevated pressures and temperatures. Methanol, water, or a mixture thereof is added to an acetic anhydride- containing stream within a flash evaporation zone to convert some or all of the acetic anhydride to acetic acid and optionally methyl acetate and to provide heat for the evaporation of a portion of the product effluent produced by the carbonylation process.