Boiler Tube Panel Sintering for Steam Oxidation Resistance
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Solution Overview
Problem
The existing methods for improving steam oxidation resistance of small-diameter boiler tubes in coal-fired boilers are inefficient, costly, and pose safety hazards due to the need for individual heat treatment and re-welding, leading to issues like tube blockage and explosion, with existing coatings showing poor stability and reliability under high-temperature conditions.
Innovation Solution
A method and apparatus involving a sandblasting device to remove oxide scale, a coating device to apply a paint mixture of aluminum and nickel powders, and a panel-type integral heating and sintering device to form an oxidation-resistant coating on the inner tube wall, all performed during boiler shutdown for high efficiency and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional individual heat treatment method is used on each tube, then oxidation resistance can be improved, but manufacturing cost increases and productivity decreases
Solution Approach 1:
The patent merges multiple individual tube heat treatments into a single integrated heat treatment process for the entire tube array. The coating device applies coating material to multiple tubes simultaneously, and the heating device treats all coated tubes together in one operation, transforming sequential individual processing into parallel batch processing to dramatically improve productivity.
Solution Approach 2:
The patent develops a universal heat treatment system that can process multiple tubes of different positions and orientations simultaneously. The heating device and coating device are designed to accommodate the entire tube array structure, enabling one system to perform the function of multiple individual treatment stations, thus improving both efficiency and consistency.
2Reliability
If tubes are cut and heat treated individually, then oxidation resistance is improved, but device complexity and labor requirements increase
Solution Approach 1:
The patent combines cutting, coating, and heating operations into an integrated process where tubes remain in their assembled array configuration throughout. The coating device and heating device are designed to work on the tube array as a whole structure, eliminating the need for disassembly, individual handling, and reassembly operations.
3Ease of manufacture
If re-welding is performed after heat treatment, then tube assembly is completed, but safety hazards increase due to welding defects
Solution Approach 1:
The patent performs the heat treatment and coating application on the tube array while it remains in its assembled state, before any welding operations would be needed. This preliminary treatment ensures that the tubes receive protective coating before being subjected to welding heat, preventing welding-induced damage to the oxidation-resistant layer and eliminating the need for post-weld repair or re-welding operations.
4Reliability
If Cr2O3 film is grown on austenitic steel, then oxidation resistance is improved, but film stability decreases at high temperatures
Solution Approach 1:
The patent employs a composite coating system consisting of multiple layers with different compositions and functions. The coating material contains Cr2O3-forming components for oxidation resistance, combined with other materials that provide structural stability and adhesion at high temperatures. This multi-component composite structure allows the outer layer to form protective Cr2O3 while the underlying layers maintain film stability and prevent spalling.
Solution Approach 2:
The patent creates different material compositions at different depths within the coating structure. The outer surface layer is formulated to form Cr2O3 for oxidation protection, while inner layers contain materials designed for thermal stability and bonding to the substrate. This gradient structure provides local optimization of properties at each depth, achieving both oxidation resistance and high-temperature stability.
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 method significantly enhances the steam oxidation resistance of small-diameter boiler tubes by forming a reliable oxidation-resistant layer, reducing maintenance duration and improving safety, while maintaining high production efficiency.
Implementation Method 1
a sandblasting device to remove oxide scale
Implementation Method 2
a panel-type integral heating and sintering device to form an oxidation-resistant coating
Data Source
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AI summary
This application relates to the technical field of coal-fired boilers, and provides a method and an apparatus for improving steam oxidation resistance of a small-diameter boiler tube in a coal-fired boiler. The method includes the following steps: cutting a boiler tube panel from a ceiling of the boiler, vertically hoisting and fixing the boiler tube panel, and cutting out a section from a bottom portion of a lower bend of the boiler tube panel; cleaning an inner tube wall of each tube body in the boiler tube panel; performing oxidation resistance coating sintering on the inner tube wall of each tube body in the boiler tube panel; and performing a welding repair on each tube body in a sintered boiler tube panel. All construction processes of this method can be completed in a furnace during shutdown and maintenance, production efficiency is high, and maintenance duration can be significantly reduced. In addition, a steam oxidation resistance layer can be formed on an inner wall of the small-diameter boiler tube, so that a steam oxidation resistance capability of a small-diameter boiler tube in a service coal-fired boiler can be greatly improved.