Hydrogen Combustion in Direct Fired Furnace for Steel Coating
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Solution Overview
Problem
The existing melting diving processes for steel flat products rely on fossil fuels, which need to be reduced or eliminated to align with decarbonization goals, while also addressing issues of oxidation and quality control in the preheating stage.
Innovation Solution
A process using hydrogen as a combustion gas in a Direct Fired Furnace (DFF) oven, with a water vapor partial pressure controlled by diluting the combustion gas with low-water vapor and hydrogen-free gases, to maintain a reducing oven atmosphere and prevent uncontrolled oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If hydrogen is used as fuel gas in the DFF furnace to reduce fossil fuel usage, then decarbonization goals are achieved, but water vapor partial pressure increases causing oxidation and scale formation on the steel surface
Solution Approach 1:
An intermediary gas (nitrogen, carbon dioxide, or their mixture) is introduced into the DFF furnace to act as a mediator between the hydrogen combustion process and the steel surface. This intermediary gas dilutes the combustion atmosphere, reducing water vapor partial pressure to below 10^-1 bar, thereby preventing oxidation while maintaining the benefits of hydrogen fuel usage
Solution Approach 2:
The water vapor partial pressure parameter in the furnace atmosphere is actively controlled and adjusted to a specific range (below 10^-1 bar) by introducing additional gases. This parameter change transforms the harmful high-water-vapor environment into a controlled, low-water-vapor environment suitable for steel preheating with hydrogen fuel
2Use of energy by moving object
If the water vapor partial pressure in the furnace atmosphere is high, then hydrogen combustion is efficient, but oxidation resistance of the steel surface deteriorates
Solution Approach 1:
The furnace atmosphere is differentiated into zones with different gas compositions. The combustion zone maintains high temperature for efficient hydrogen combustion, while the steel surface zone is protected by the introduced intermediary gas that creates a low water vapor partial pressure environment, achieving local quality optimization for both combustion efficiency and oxidation protection
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
This approach reduces fossil fuel usage, minimizes oxidation and tinder formation on the steel surface, and maintains the quality of the metallic cover applied during the melting diving process, thereby ensuring the integrity and properties of the steel flat products.
Implementation Method 1
the DFF furnace has at least one burner operated with a fuel gas and an oxygen-containing gas, which are combusted to form a combustion gas
Implementation Method 2
heating and/or maintaining the preheated steel flat product at a temperature between 400°C and 950°C
Implementation Method 3
heating and/or maintaining the preheated steel flat product at a temperature between 400°C and 950°C
Implementation Method 4
cooling the warm steel flat product to a temperature that is at least 50 K below and at most 50 K above a molten bath temperature
Implementation Method 5
immersing the cooled steel flat product in a metallic molten bath with a molten bath temperature in order to coat the steel flat product with a metallic coating by hot-dip coating
Data Source
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AI summary
The invention relates to a method for hot-dip coating a flat steel product and a hot-dip coating system (100).