Secondary Reactor Oxygen Distribution for Terephthalic Acid

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Solution Overview

Problem

Conventional liquid-phase oxidation reactors for producing terephthalic acid, such as CSTRs and bubble column reactors, face issues with high capital and maintenance costs, mechanical failures, and inefficient oxygen distribution, leading to impurities and reduced reaction rates due to oxygen-starved regions.

Innovation Solution

A system comprising a primary oxidation reactor and a secondary oxidation reactor with specific inlet and outlet configurations, where the secondary reactor has a slurry inlet spaced from the bottom by 0.3L to 0.9L and upper oxidant inlets positioned to minimize unaerated zones, enhancing oxygen distribution and reducing impurity formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional CSTRs with mechanical agitation are used, then mixing of multi-phase reaction medium is achieved, but capital cost and maintenance cost increase due to expensive motors, fluid-sealed bearings, and complex stirring mechanisms

Engineering Contradiction:

Improvemixing efficiencyVSAvoidmechanical agitation system

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces mechanical agitation systems with gas-phase sparging systems. Gas bubbles are introduced into the liquid-phase reaction medium to provide agitation and mixing through buoyancy-driven flow, eliminating the need for motors, bearings, and complex stirring mechanisms while maintaining effective mixing of the multi-phase reaction medium

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses gas-phase oxidant sparging into the liquid-phase reaction medium to create pneumatic agitation. The rising gas bubbles generate liquid circulation and mixing without mechanical contact, reducing device complexity and maintenance requirements while achieving the desired mixing effect

Inventive Principle:

Principle #29Pneumatics and hydraulics

2Reliability

If conventional bubble column reactors are used, then mechanical maintenance is reduced, but unaerated zones form at the top of the reactor leading to oxygen-starved regions and impurity formation

Engineering Contradiction:

Improvemechanical system stabilityVSAvoidimpurity formation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by positioning multiple spargers at different vertical locations within the reactor. The first sparger is positioned to aerate the bottom portion and the second sparger is positioned to aerate the top portion, ensuring uniform oxygen distribution throughout the reaction medium and preventing oxygen-starved regions that would otherwise generate impurities

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the gas injection function by using multiple spargers distributed at different heights in the reactor rather than a single sparger. This segmentation ensures that the entire volume of reaction medium receives adequate aeration, eliminating unaerated zones and the associated harmful impurity formation

Inventive Principle:

Principle #1Segmentation

3Quantity of substance

If liquid phase contains insufficient concentration of molecular oxygen, then oxygen availability for reaction is reduced, but side-reactions generate impurities and intended reactions are retarded

Engineering Contradiction:

Improvedissolved oxygen concentrationVSAvoidimpurity formation

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent changes the physical state and distribution parameters of oxygen by introducing it as a gas-phase sparger stream that bubbles through the liquid phase. This creates extensive gas-liquid interfacial area for oxygen dissolution, maintaining high dissolved oxygen concentrations throughout the reaction medium and preventing the formation of impurities associated with oxygen starvation

Inventive Principle:

Principle #35Parameter changes

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 configuration improves the efficiency and economy of terephthalic acid production by minimizing unaerated zones, maintaining higher oxygen concentrations, and reducing impurities, resulting in higher quality and yield of terephthalic acid.

Implementation Method 1

At least a portion of the molecular oxygen introduced into the reactor as a gas dissolves into the liquid phase of the reaction medium to provide oxygen availability for the liquid-phase reaction

Methodology Applied

Scientific EffectDissolution: Absorption (physical)

Implementation Method 2

Agitation of the reaction medium in the reaction zone is provided primarily by the natural buoyancy of gas bubbles rising through the liquid phase of the reaction medium

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Implementation Method 3

liquid-phase catalytic partial oxidation of para-xylene to terephthalic acid

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentEP2528886B1Oxidation system with sidedraw secondary reactor

Publication Date: 2017.09.06 GRUPO PETROTEMEX SA DE CV

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AI summary

Disclosed are process and apparatus for vertical splitting of the oxygen supply to a post-oxidation reactor. Further disclosed are process and apparatus for supplying reaction medium to a post-oxidation reactor at a mid-level inlet. Such apparatus and process can assist in reducing oxygen pinch throughout the post-oxidation reactor.