Boiler Tube Inner-Wall Coating 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 disassembly, re-welding, and the instability of Cr2O3 films, leading to oxide scale issues that can cause tube blockages and explosions.
Innovation Solution
A method involving cutting a boiler tube panel, cleaning the inner tube wall, applying an oxidation resistance coating using a sandblasting and coating device, and sintering the coating with a panel-type integral heating device to form a durable oxidation resistance layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional heat treatment method is used on small-diameter boiler tubes, then oxidation resistance is improved, but disassembly and re-welding are required causing safety hazards and high costs
Solution Approach 1:
The patent extracts the harmful welding process from the heat treatment workflow. Instead of removing tubes for individual heat treatment and re-welding, the invention applies heat treatment in-situ within the assembled boiler structure, eliminating the extraction-reprocessing-reinstallation cycle that introduces welding defects and safety hazards
Solution Approach 2:
The patent introduces an intermediary heating device that can access and heat the interior of small-diameter tubes without disassembly. This mediator device enables heat treatment through the existing tube structure, avoiding the need to break welding connections and reassemble the system
2Reliability
If traditional heat treatment method is used on small-diameter boiler tubes, then oxidation resistance is improved, but maintenance time and cost increase
Solution Approach 1:
The patent merges multiple operations into a single in-situ heat treatment process. By combining access, heating, and treatment into one continuous operation performed within the assembled boiler, it eliminates the separate disassembly and reassembly phases that traditionally extended maintenance time and increased costs
Solution Approach 2:
The patent performs preliminary preparation by positioning the heating device within the tube structure before initiating the heat treatment process. This preliminary positioning enables immediate treatment upon device insertion, avoiding time-consuming disassembly procedures
3Reliability
If Cr2O3 film is formed on austenitic steel, then oxidation resistance is improved, but film stability decreases at high temperature causing loose oxide scale
Solution Approach 1:
The patent changes the thermal parameters by applying controlled heat treatment at specific temperature ranges and durations. This transforms the microstructure and compositional distribution within the tube wall, promoting formation of stable oxide scales with different characteristics than those formed by simple exposure
4Productivity
If small-diameter boiler tubes are used in ultra-supercritical boilers, then steam transmission efficiency is improved, but oxide scale accumulation increases causing blockages and explosions
Solution Approach 1:
The patent applies preliminary heat treatment during manufacturing or initial installation to establish a stable, oxidation-resistant surface structure before the tubes enter service. This preliminary action creates a protective condition that prevents oxide scale accumulation during the high-efficiency steam transmission operation
Solution Approach 2:
The patent converts the inherently high-temperature operation that causes oxidation into a benefit by applying controlled heat treatment that stabilizes the material composition. The same thermal conditions that would normally create harmful oxide scales are instead used to create a stable, protective microstructure
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 enhances the steam oxidation resistance capability of small-diameter boiler tubes by forming a robust oxidation resistance layer during maintenance, reducing maintenance duration and improving safety by eliminating oxide scale issues.
Implementation Method 1
cleaning an inner tube wall of each tube body in the boiler tube panel
Implementation Method 2
performing oxidation resistance coating sintering on the inner tube wall
Implementation Method 3
sintering the coating with a panel-type integral heating device to form a durable oxidation resistance layer
Implementation Method 4
forming a robust oxidation resistance layer during maintenance, reducing maintenance duration and improving safety by eliminating oxide scale issues
Data Source
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.