Ammonia Oxidation Catalyst Gauze Ignition
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Solution Overview
Problem
Platinum/rhodium alloy gauzes used in ammonia oxidation processes face difficulties in ignition during start-up, leading to losses of unreacted ammonia and safety issues due to high ignition temperatures and the complexity of applying platinum coatings, which are costly and risky.
Innovation Solution
Incorporating a top layer of knitted un-alloyed platinum wire into a platinum/rhodium alloy gauze pack enhances ignition by maximizing gas exposure and reducing shielding, allowing for controlled reaction zones and minimizing platinum losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum/rhodium alloy gauzes are used for ammonia oxidation, then high conversion is achieved, but ignition temperature is too high and start-up is difficult
Solution Approach 1:
The patent applies local quality by incorporating un-alloyed platinum wires specifically at the surface layer of the platinum/rhodium alloy gauze. This creates a localized region with different catalytic properties - the un-alloyed platinum provides low-temperature ignition activity, while the underlying alloy maintains structural integrity and high-temperature conversion capability. This resolves the contradiction by enabling reliable ignition at lower temperatures without sacrificing the high conversion performance of the alloy gauze.
Solution Approach 2:
The patent employs composite materials by combining un-alloyed platinum wires with platinum/rhodium alloy in a hierarchical structure. The un-alloyed platinum component serves as an ignition promoter, while the alloy component provides mechanical strength and catalytic activity. This composite approach allows the gauze to exhibit both low ignition temperature (from un-alloyed Pt) and high conversion efficiency (from Pt/Rh alloy), resolving the technical contradiction between ignition reliability and ignition temperature.
2Reliability
If platinum coatings are applied to lower ignition temperature, then ignition is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent applies segmentation by separating the ignition function from the structural and high-temperature catalytic function. Instead of applying a coating to the entire gauze surface, un-alloyed platinum wires are selectively incorporated only at the surface layer where ignition occurs. This segmented approach provides ignition improvement while avoiding the complexity and cost of coating the entire gauze structure, as the alloy substrate remains exposed in non-critical regions.
Solution Approach 2:
The patent effectively uses a small amount of un-alloyed platinum (a more valuable but simpler material) in a localized manner to achieve the ignition function. Rather than applying extensive platinum coatings throughout the gauze structure, the un-alloyed platinum wires are concentrated only where needed for ignition, reducing overall manufacturing complexity and material costs while maintaining ignition reliability.
3Area of stationary object
If knitted structure is used for catalyst gauze, then gas exposure is maximized, but shielding at cross-over points increases
Solution Approach 1:
The patent applies local quality by concentrating un-alloyed platinum wires specifically at the surface-exposed regions of the knitted gauze structure. This ensures that the regions with maximum gas exposure (the outer surface of the knit loops) have the enhanced ignition activity, while minimizing the impact of shielding at cross-over points. The un-alloyed platinum is strategically placed where it can most effectively interact with the reactant gases.
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 solution enables rapid, uniform, and reliable ignition of ammonia oxidation processes, improving catalyst selectivity and reducing platinum losses while maintaining efficient manufacturing and gauze density.
Implementation Method 1
a first layer of knitted first wire material, wherein said first wire material is made from a platinum-rhodium alloy, characterized in that said first layer contains an activator in the form of a second wire material which is knitted among the first wire material and which is made from un-alloyed platinum
Implementation Method 2
ammonia oxidation processes... the reactant gases are mixed and passed at elevated temperature and pressure through a reaction vessel in which is placed a pack of platinum/rhodium alloy gauzes that catalyse the oxidation reactions
Data Source
AI summary
A catalyst gauze for an ammonia oxidation process is described, containing a first layer of knitted first wire material, whereby said first wire material is made from a platinum-rhodium alloy, characterized in that said first layer contains an activator in the form of a second wire material which is knitted among the first wire material and which is made from un-alloyed platinum.