Duplex Steel Liquid Distributors Resisting Cross-Cut Corrosion
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Solution Overview
Problem
The liquid distributors in urea manufacturing plants, made from corrosion-resistant duplex steel, experience frequent replacement due to corrosion, leading to inefficient tube loading and reduced stripper efficiency, as the size and shape of holes change over time, affecting liquid flow and distribution.
Innovation Solution
A ferritic-austenitic steel alloy with specific composition and microstructural characteristics, produced through hot isostatic pressing, is used to create liquid distributors that are more resistant to cross-cut end-attack corrosion, resulting in reduced weight loss and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid distributors are made from corrosion-resistant duplex steel, then corrosion resistance is improved, but the holes still change size and shape over time due to cross-cut end-attack corrosion
Solution Approach 1:
The patent applies parameter changes by modifying the microstructural parameters of the duplex steel, specifically controlling the austenite spacing to be less than 20 μm and the austenite phase length/width ratio to be less than 5. This microstructural optimization changes the material's resistance to cross-cut end-attack corrosion, preventing hole dimension changes while maintaining corrosion resistance
Solution Approach 2:
The patent utilizes composite material principles by creating a duplex steel with a two-phase microstructure (ferritic and austenitic phases) with specific characteristics. The controlled austenite spacing and phase ratio create a composite microstructure that resists cross-cut end-attack corrosion, protecting the holes from changing size and shape
2Reliability
If liquid distributors are frequently replaced due to corrosion, then corrosion damage is addressed, but stripper efficiency is reduced due to inefficient tube loading
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the microstructure of the duplex steel before the liquid distributors are installed and subjected to corrosion. By controlling the austenite spacing and phase ratio in advance, the material is prepared to resist cross-cut end-attack corrosion, preventing the need for frequent replacements and maintaining stripper efficiency
Solution Approach 2:
The patent changes the material parameters of the duplex steel (austenite spacing < 20 μm, austenite phase length/width ratio < 5) to improve durability. This parameter optimization ensures the liquid distributors last longer without corrosion damage, maintaining consistent tube loading and stripper efficiency
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 use of the ferritic-austenitic steel alloy, with its optimized microstructure and composition, significantly reduces corrosion vulnerability and weight loss, enhancing the longevity and efficiency of liquid distributors in urea manufacturing plants.
Implementation Method 1
The use of the ferritic-austenitic steel alloy, with its optimized microstructure and composition, significantly reduces corrosion vulnerability and weight loss
Data Source
AI summary
Disclosed is a Hot Isostatic Pressed ferritic-austenitic steel alloy, as well objects thereof. The elementary composition of the alloy comprises, in percentages by weight:C 0-0.05;Si0-0.8;Mn0-4.0;Crmore than 29-35;Ni3.0-10; Mo0-4.0;N0.30-0.55; Cu0-0.8;W0-3.0;S 0-0.03;Ce0-0.2;the balance being Fe and unavoidable impurities. The objects can be particularly useful in making components for a urea production plant that require processing such as machining or drilling. A preferred use is in making, or replacing, liquid distributors as used in a stripper as is typically present in the high-pressure synthesis section of a urea plant.