Aqueous Phase Oxidation Process Oxygen Recycling
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Solution Overview
Problem
Aqueous phase oxidation processes face challenges such as high energy consumption, emission of noxious gases, incomplete metal recovery, and difficulties in controlling oxygen gas supply and pressure fluctuations, leading to inconsistent reaction rates and equipment oversizing.
Innovation Solution
An improved aqueous phase oxidation process that involves pre-processing feedstock to uniform particle size, using a combination of nitric and sulfuric acids, and dispersing oxygen gas from the reactor headspace into the reaction mixture to maintain consistent oxygen levels, allowing for efficient oxidation of various feedstocks including municipal and farm waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxygen gas is bubbled into the aqueous phase to oxidize reduction products of nitric acid, then oxidation efficiency is improved, but oxygen gas quickly separates and collects in the headspace requiring large amounts to be supplied
Solution Approach 1:
The patent implements a feedback control system where oxygen gas is continuously transferred from the headspace back into the aqueous phase based on measured oxygen levels. This creates a closed-loop system that maintains optimal oxygen concentration for oxidation while minimizing gas loss to the headspace, directly resolving the contradiction between oxidation efficiency and oxygen consumption.
Solution Approach 2:
The patent introduces an intermediary mechanism (oxygen transfer system from headspace to aqueous phase) that recycles oxygen gas instead of allowing it to escape. This intermediary process captures the separated oxygen and returns it to where it is needed, reducing the overall amount of oxygen gas required while maintaining oxidation efficiency.
2Ease of operation
If oxygen gas supply is controlled based on headspace measurements, then control simplicity is improved, but precise control of oxygen in aqueous phase is difficult
Solution Approach 1:
The patent replaces the indirect mechanical measurement approach (headspace gas analysis) with direct aqueous phase oxygen sensing. This substitution enables precise measurement of the actual parameter of interest (dissolved oxygen) while maintaining automated control simplicity, resolving the contradiction between ease of operation and measurement precision.
3Productivity
If reactor pressure is maintained high for oxidation reactions, then reaction rate is improved, but pressure fluctuations make continuous feed material introduction difficult
Solution Approach 1:
The patent prepares feed material in advance and uses a pressurized feed system that pre-charges material into the reactor at controlled rates. This preliminary preparation and controlled introduction method allows continuous operation despite high pressure conditions, resolving the contradiction between maintaining high reaction rates and enabling steady feed material introduction.
4Productivity
If residence time is extended to accommodate feed material variations, then complete oxidation is achieved, but equipment must be oversized
Solution Approach 1:
The patent changes key process parameters including temperature, pressure, and oxygen concentration to accelerate the oxidation reaction rate. By optimizing these parameters, the system achieves complete oxidation in shorter residence times, eliminating the need for oversized equipment while maintaining oxidation completeness.
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
The process achieves complete or near-complete oxidation of feedstocks with reduced energy consumption, minimized gas emissions, and improved process control, enabling efficient and consistent operation across different feed materials.
Implementation Method 1
The feedstock is oxidized in an aqueous reaction mixture by one or more oxidizing acids
Implementation Method 2
Oxygen gas may be supplied to the reaction mixture to reoxidize the reduction products of the oxidizing acid
Implementation Method 3
Oxygen gas may be supplied to the reaction mixture to reoxidize the reduction products of the oxidizing acid that were formed during oxidation of the feed materials
Data Source
AI summary
An improved oxidization process may be used to oxidize a wide variety of feedstocks. Oxidation takes place in a reactor where the feedstock is mixed with an oxidizing acid, such as nitric acid. The reaction mixture may also include a secondary oxidizing acid such as sulfuric acid as well as water and/or dissolved and mechanically mixed oxygen gas. The reactor may be maintained at an elevated pressure such as at least approximately 2070 kPa or desirably at least approximately 2800 kPa. The temperature of the reaction mixture may be maintained at no more than 210° C. In the various embodiments described herein, the process may include: combining recycled effluent from the reactor with the feedstock, combining one or more oxidizing acids with the feedstock, comminuting the feedstock to reduce the size of the particles, feeding the feedstock into the high pressure reactor at an approximately constant feed rate, dispersing oxygen gas from the headspace of the reactor into the reaction mixture, and/or removing all or almost all of the gas from the reactor through the liquid effluent.