Energy Recovery and Water Removal in Aromatic Acid Oxidation
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Solution Overview
Problem
Current methods for producing aromatic carboxylic acids, such as terephthalic acid, face challenges in efficiently recovering energy from exothermic liquid phase oxidation reactions and removing excess water, which can lead to corrosion and require additional processing steps.
Innovation Solution
A process involving the oxidation of an aromatic feedstock to form an aromatic carboxylic acid composition, where the oxidation reaction offgas is directly or indirectly fed to an expander for energy recovery, followed by a fractionation zone with multiple stages to efficiently separate and remove water, allowing for the recovery of mechanical power and partial dehydration of the mono-carboxylic acid solvent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxidation reaction offgas is passed to a condenser to remove condensable components before energy recovery, then corrosion is avoided, but energy recovery efficiency is reduced
Solution Approach 1:
The patent converts the harmful condensable components (water and carboxylic acid vapors) into a beneficial resource by using them as fuel in the expander. The offgas containing these condensable components is directly fed to the expander without prior condensation, and the expansion process generates mechanical power while the condensables burn to provide heat, thus converting what was previously a corrosion problem into an energy source.
2Quantity of substance
If a fractionation device is used to separate water from the oxidation solvent, then water concentration in the reactor is controlled, but process complexity and energy consumption increase
Solution Approach 1:
The patent merges multiple functions into the expander unit: it serves as both an energy recovery device and a water separation device. The fractionation of water from the oxidation solvent occurs within the expander system through the expansion and condensation process, eliminating the need for a separate external fractionation device and reducing overall process complexity.
Solution Approach 2:
The system uses its own offgas to drive the expansion process and provide the heat necessary for water separation. The oxidation reaction offgas containing water and carboxylic acid vapors is fed directly to the expander, where the expansion process itself facilitates water removal without requiring external energy input or additional separation equipment.
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 recovers energy from the oxidation reaction offgas and efficiently removes excess water, reducing the need for external heat sources and increasing the recovery of mono-carboxylic acid solvent, while maintaining a low water concentration in the oxidation reaction zone.
Implementation Method 1
oxidizing an aromatic feedstock composition to an aromatic carboxylic acid composition in an oxidation reaction zone... under reaction conditions which produce an oxidation reaction offgas... highly exothermic
Implementation Method 2
feeding said oxidation reaction offgas from step a) directly or indirectly to an expander for recovering mechanical power
Implementation Method 3
allowing a portion of the solvent to vaporize during the reaction... the combination of the reaction gases and the vaporized solvent is sometimes referred to as oxidation reaction offgas
Implementation Method 4
feeding said expander outlet product from step b) directly or indirectly to a fractionation zone... producing a liquid containing partially de-watered mono-carboxylic acid product
Data Source
AI summary
This invention relates to a process for the manufacture of aromatic carboxylic acids by exothermic liquid phase oxidation of an aromatic feedstock. More particularly, this invention relates to the efficient energy recovery of the exotherm produced by the liquid phase oxidation of an aromatic feedstock. Also, this invention relates to the efficient energy recovery of the exotherm produced by the liquid phase oxidation of an aromatic feedstock while also utilizing the heat from the energy of oxidation to efficiently remove water resulting from the exothermic oxidation reaction.