Oxygen Injection System Recirculation Loop White Liquor Oxidation
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Solution Overview
Problem
The increasing cost of pure sodium hydroxide (NaOH) in the European market necessitates the development of methods to reuse process streams in the kraft pulp process to produce a NaOH substitute, as the current methods for oxidizing white liquor in air-based oxidation reactors are limited by the capacity of air to oxidize the liquor.
Innovation Solution
An oxygen injection system with a recirculation loop is introduced, comprising pipes, pumps, valves, mixing means, and an oxygen dosing cabinet, which circulates white liquor from an air-based oxidation reactor, mixes it with oxygen, and returns the oxidized mixture, enhancing the oxidation process by overcoming limitations in air-based systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air-based oxidation is used to oxidize white liquor, then the process is simple and safe, but the production amount of oxidized white liquor is limited
Solution Approach 1:
The patent introduces pure oxygen or oxygen-enriched air as the oxidation gas to replace or supplement atmospheric air. This provides a higher concentration of oxygen (up to 100% pure O2) compared to air (21% O2), thereby accelerating the oxidation reaction rate and increasing the production amount of oxidized white liquor while maintaining the safety and simplicity of the air-based system
2Productivity
If oxygen injection is added to increase oxidation capacity, then the production amount increases, but the system complexity increases
Solution Approach 1:
The patent combines the oxygen injection system with the existing air-based oxidation reactor by integrating the oxygen injection line into the gas distribution system. The oxygen injection device is merged with the recirculation loop and gas spargers, allowing pure oxygen to be injected alongside or instead of air without requiring a completely separate system, thus increasing productivity while limiting the increase in system complexity
3Productivity
If pure oxygen is used instead of air, then the oxidation efficiency increases, but the cost and safety risks increase
Solution Approach 1:
The patent changes the oxygen concentration parameter from atmospheric levels (21% in air) to high concentrations (up to 100% pure oxygen) to dramatically improve oxidation efficiency. To mitigate the associated safety risks of flash or explosion, the system maintains controlled operating conditions including temperature control (below 100°C) and pressure control (below 1.02 bar abs), and uses distributed oxygen injection through multiple spargers to prevent localized high-concentration zones that could lead to runaway reactions
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 system increases the production of oxidized white liquor by 40% or more, reducing the reliance on purchased NaOH and providing a cost-effective solution by efficiently utilizing oxygen, while ensuring safe operation and avoiding flash or explosion risks.
Implementation Method 1
the first pipe (2.1.1) comprises at least one pump (2.2)
Implementation Method 2
the at least one mixing means (2.4) is selected from a static mixer or a venturi mixer
Implementation Method 3
so that the gas is dissolved in the liquid in a zone extending from the stirring means to the liquid surface
Implementation Method 4
methods to produce NaOH by the oxidation of white liquor
Implementation Method 5
the second pipe (2.1.2) comprises at least one temperature probe (2.6)
Data Source
Figure 1~2
Figure 3
AI summary
The present application relates to an oxygen injection system for an air-based oxidation reactor (1), wherein the oxygen injection system comprises a recirculation loop (2). The application also relates to a process for increasing the amount per unit of time of oxidized of white liquor produced by adding oxygen to white liquor via the oxygen injection system. An air-based oxidation reactor (1) comprising at least one oxygen injection system is also disclosed herein. The present invention allows to produce between 40 and 100% more oxidated white liquor with the same air-based reactor.