Catalytic NOx Removal via NO2 Enrichment and Oxidative Scrubbing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for removing nitrogen oxides from gases are limited by slow oxidation of nitric oxide to nitrogen dioxide at low oxygen concentrations, requiring long residence times and are often complex and costly, especially when using ozone.
Innovation Solution
A method involving catalytic oxidation to convert nitric oxide to nitrogen dioxide followed by oxidative gas scrubbing, utilizing a fixed-bed reactor with a Pt/Al₂O₃ catalyst and an aqueous alkaline solution, allowing for efficient nitrogen dioxide enrichment and scrubbing at moderate oxygen and pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalytic oxidation is performed at low oxygen partial pressure, then nitrogen monoxide conversion to nitrogen dioxide proceeds slowly, but the process becomes more complex and expensive when using alternatives like ozone
Solution Approach 1:
The patent changes the oxygen partial pressure parameter to an optimal range (0.1-6 vol%, preferably 0.5-3 vol%) and adjusts temperature (40-400°C, preferably 100-300°C) to enable efficient catalytic oxidation of nitric oxide to nitrogen dioxide without requiring complex alternative processes. This parameter optimization resolves the contradiction by achieving high productivity through simple catalytic oxidation rather than complex ozone-based methods.
Solution Approach 2:
The patent introduces a catalyst as an intermediary substance that mediates the oxidation reaction between nitric oxide and oxygen. The catalyst enables the reaction to proceed efficiently at moderate oxygen partial pressures and temperatures, avoiding the need for complex process modifications. This intermediary approach resolves the technical contradiction by providing a straightforward catalytic pathway for nitrogen dioxide formation.
2Productivity
If high oxygen content (3-6 vol% at >15 bar) is used, then oxidation of nitric oxide to nitrogen dioxide proceeds rapidly, but the process is limited to high pressure conditions increasing operational complexity
Solution Approach 1:
The patent decouples the oxidation rate from high pressure requirements by optimizing oxygen partial pressure (0.1-6 vol%) and temperature (40-400°C) parameters. This allows rapid oxidation to proceed at moderate pressures, eliminating the limitation to high-pressure operations and enhancing operational flexibility while maintaining high productivity.
3Reliability
If long residence time is used, then nitric oxide can be sufficiently oxidized, but the process becomes less efficient and more complex
Solution Approach 1:
The patent changes the temperature parameter to an optimal range (40-400°C, preferably 100-300°C) and oxygen partial pressure (0.1-6 vol%) to achieve rapid oxidation kinetics. This allows complete oxidation to occur within short residence times, simultaneously ensuring reliability of oxidation completeness and maintaining high process efficiency, thereby resolving the contradiction between these two parameters.
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 approach enables high scrubbing rates and compliance with regulatory emissions standards while reducing operational complexity and costs, suitable for retrofitting existing plants.
Implementation Method 1
subjecting the starting gas to catalytic oxidation to obtain a gas enriched in nitrogen dioxide compared to the starting gas (in which catalytic oxidation, nitrogen monoxide is converted to nitrogen dioxide)
Implementation Method 2
catalytic oxidation, nitrogen monoxide is converted to nitrogen dioxide
Implementation Method 3
subjecting the gas enriched in nitrogen dioxide compared to the starting gas to oxidative gas scrubbing to obtain a scrubbed gas
Data Source
Figure 1
AI summary
A process for removing nitrogen oxides from a gas is proposed, comprising providing a starting gas (2) containing nitrogen oxides, subjecting the starting gas (2) to catalytic oxidation (5) to obtain a gas (3) enriched with nitrogen dioxide, wherein nitric oxide is converted to nitrogen dioxide during the catalytic oxidation, and subjecting the enriched gas (3) to oxidative gas scrubbing (8) to obtain a scrubbed gas (4). A corresponding apparatus (13) is also proposed.