Catalyst-Coated Feedwater Piping for Nitrous Acid Corrosion Control
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Solution Overview
Problem
In thermal power plants, ammonia added to feed water reacts with high temperatures to generate nitrogen monoxide, which converts to nitrous acid, accelerating corrosion in low-pressure turbines and feed water heaters, leading to increased maintenance and reduced plant reliability.
Innovation Solution
Installation of a nitrogen monoxide cracking unit in the feed water or waste water system, utilizing materials with high catalytic effects like chromium, copper, or nickel, to decompose nitrogen monoxide into nitrogen and water before it forms nitrous acid, thereby inhibiting corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ammonia is added to feed water for corrosion prevention, then corrosion resistance is improved, but nitrogen monoxide is generated at high temperature which accelerates corrosion in low-pressure turbines and feed water heaters
Solution Approach 1:
A nitrogen monoxide decomposing unit is introduced as an intermediary device in the feed water system. This unit contains a catalyst that decomposes nitrogen monoxide into nitrogen and oxygen before the water reaches the low-pressure turbine and feed water heater, preventing the harmful formation of nitrous acid while maintaining the corrosion prevention benefits of ammonia addition
Solution Approach 2:
The harmful nitrogen monoxide component is extracted and removed from the feed water stream through the decomposing unit. By separating and decomposing NO before it can convert to nitrous acid, the system eliminates the harmful factor while preserving the beneficial ammonia corrosion protection
2Productivity
If steam temperature is raised to 700°C or higher for improved power generation efficiency, then productivity is improved, but nitrogen monoxide generation increases which accelerates corrosion
Solution Approach 1:
The decomposing unit converts the harmful nitrogen monoxide generated at high temperatures into beneficial nitrogen and oxygen gases. This allows the system to operate at higher steam temperatures for improved efficiency while the catalyst transforms the harmful byproduct into harmless substances, turning the corrosion problem into a non-issue
3Reliability
If nitrous acid concentration is reduced to prevent corrosion, then reliability is improved, but nitrogen monoxide must be decomposed which requires additional equipment
Solution Approach 1:
The nitrogen monoxide decomposing unit performs preliminary decomposition of NO early in the feed water system, before the water enters the low-pressure turbine and feed water heater. By taking preventive action upstream, the system avoids the formation of nitrous acid that would cause corrosion, extending plant service life without requiring complex downstream remediation systems
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
Effectively prevents corrosion in piping members and boilers by reducing nitrous acid concentration, allowing the use of cost-effective carbon steel instead of stainless steel, and reducing the load on condensate water desalination units, thus extending plant service life and maintaining water quality.
Implementation Method 1
utilizing materials with high catalytic effects like chromium, copper, or nickel, to decompose nitrogen monoxide into nitrogen and water
Data Source
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AI summary
The present invention makes it possible, in a plant such as a thermal power plant, to prevent the corrosion of a piping member or a device such as a boiler by effectively decomposing nitrogen monoxide (NO) included in waste water or condensate water and inhibiting the generation of nitrous acid (HNO2). The present invention is a piping member used in a feed water system or a waste water system of a plant, and characterized by coating an inner wall of the piping member (200) with a catalyst (201) accelerating decomposition of nitrogen monoxide.