Oxidation System Sidedraw Secondary Reactor
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Solution Overview
Problem
Conventional liquid-phase oxidation reactors for producing polycarboxylic acids, such as terephthalic acid from para-xylene, face issues with oxygen-starved regions leading to impurities and reduced reaction rates, and have high capital and maintenance costs due to mechanical agitation systems, which also suffer from mechanical failures.
Innovation Solution
A system comprising a primary oxidation reactor and a secondary oxidation reactor with a secondary reaction zone designed to optimize oxygen distribution and agitation, where the slurry inlet is positioned between 0.3Ls and 0.9Ls from the bottom of the secondary reaction zone, promoting vertical gradients in oxygen and reactant concentrations to enhance reaction efficiency and reduce impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If mechanical agitation means are used in conventional CSTRs to mix the reaction medium, then thorough mixing and uniform concentration distribution are achieved, but capital cost increases due to expensive motors, fluid-sealed bearings, drive shafts, and complex stirring mechanisms
Solution Approach 1:
The patent replaces mechanical agitation systems with a non-mechanical approach by introducing gas bubbles into the liquid phase. The rising bubbles create natural convection currents that mix the reaction medium without requiring motors, shafts, or seals. This substitution eliminates the complex mechanical components while achieving the desired mixing effect through fluid dynamics.
Solution Approach 2:
The invention uses gas-liquid two-phase flow to achieve mixing. Gas bubbles are introduced into the liquid reaction medium, and the interaction between the rising gas phase and the liquid phase creates circulation patterns and turbulence that promote uniform concentration distribution. This pneumatic-hydraulic approach replaces traditional mechanical mixing.
2Stability of the object's composition
If mechanical agitation systems are used in CSTRs, then mixing is provided, but operating cost increases due to regular maintenance requirements and labor shutdown time
Solution Approach 1:
By replacing mechanical agitation with gas bubble-induced convection, the system eliminates moving parts that require maintenance. The mixing function is achieved through the natural rise of gas bubbles and the resulting fluid circulation, which has no mechanical components to wear out or fail, thereby eliminating maintenance shutdown time.
Solution Approach 2:
The gas bubbles themselves perform the mixing function as they rise through the liquid. The system uses the energy from gas injection to create self-sustaining convection currents that continuously mix the reaction medium without external mechanical intervention, making the mixing process self-regulating and maintenance-free.
3Stability of the object's composition
If mechanical agitation systems are used in CSTRs, then mixing is achieved, but reliability decreases due to mechanical failure of rotating and oscillating components
Solution Approach 1:
The patent eliminates all rotating and oscillating mechanical components by using gas bubble rise and natural convection for mixing. Since there are no motors, shafts, bearings, or seals, there are no mechanical parts that can fail, thereby dramatically improving system reliability while maintaining concentration uniformity through fluid dynamic mixing.
4Quantity of substance
If gas-phase oxidant is introduced into the reactor, then oxygen availability for liquid-phase reaction is provided, but oxygen-starved regions can still form leading to impurities and retarded reaction rates
Solution Approach 1:
Instead of introducing gas as a single large stream, the system divides the gas phase into numerous small bubbles distributed throughout the liquid. This segmentation increases the total gas-liquid interfacial area and ensures oxygen is delivered to multiple locations simultaneously, preventing oxygen-starved regions from forming while maintaining uniform oxygen distribution.
Solution Approach 2:
The gas bubbles are distributed throughout the liquid phase to create localized oxygen delivery zones. Each bubble provides oxygen to its surrounding liquid region, and the collective effect of numerous bubbles ensures uniform oxygen availability throughout the entire reaction medium, addressing local oxygen deficiency issues.
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 yield and purity of polycarboxylic acids by minimizing oxygen-starved regions and reducing mechanical complexity, leading to a more economical and reliable oxidation process with lower impurity generation.
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
Implementation Method 2
the slurry inlet is spaced from the bottom of the secondary reaction zone by a distance in the range of from about 0.3L s to about 0.9L s promoting vertical gradients in oxygen and reactant concentrations
Data Source
Figure 1
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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.