Direct Reduction Shaft Furnace Gas Control for Iron Oxide
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Solution Overview
Problem
Integrated steel mills face inefficiencies in reducing iron oxide to metallic iron using associated gases like coke oven gas (COG) and oxygen steelmaking furnace gas (BOFG), as existing methods do not effectively utilize these gases to minimize energy consumption and CO2 emissions while maintaining production levels.
Innovation Solution
A method involving the removal of carbon dioxide from a top gas stream, heating it to form a reducing gas stream, and combining it with preheated COG as a synthesis gas stream, which is then used in a direct reduction shaft furnace, with optional use of a thermal reactor system and hot oxygen burner to control carbon content and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If coke oven gas and oxygen steelmaking furnace gas are used to reduce iron oxide to metallic iron, then energy consumption is reduced and CO2 emissions are minimized, but the gases must be carefully controlled to avoid nitrogen buildup and maintain proper carbon content
Solution Approach 1:
The patent combines coke oven gas and oxygen steelmaking furnace gas into a unified reducing gas stream for iron oxide reduction. This merging allows both gases to be utilized together, maximizing energy efficiency and minimizing CO2 emissions while maintaining production levels through integrated gas management.
Solution Approach 2:
The patent implements dynamic control of gas composition parameters, particularly managing nitrogen content from BOFG and carbon content from COG. By adjusting the proportions and treatment of each gas stream, the system optimizes reducing gas composition to prevent nitrogen buildup while maintaining proper carbon content for efficient iron oxide reduction.
2Manufacturing precision
If coke oven gas is used as reducing gas, then carbon content control is improved, but methane must be reformed under proper conditions to form CO and H2
Solution Approach 1:
The patent applies preliminary reforming treatment to coke oven gas before it enters the reduction zone. By pre-reforming methane into CO and H2 under controlled conditions, the system ensures optimal carbon content and reducing gas composition are achieved before the gas contacts iron oxide, improving manufacturing precision while managing reforming complexity in advance.
3Productivity
If oxygen steelmaking furnace gas is used for reduction, then production efficiency is maintained, but nitrogen may build up to very high levels in recirculating system
Solution Approach 1:
The patent converts the harmful nitrogen content in oxygen steelmaking furnace gas into a manageable parameter by carefully controlling its proportion in the mixed reducing gas stream. By balancing BOFG usage with COG and implementing proper gas management, the system maintains production efficiency while preventing nitrogen buildup through controlled dilution and recirculation management.
4Productivity
If carbon dioxide is removed from top gas stream and gas is heated to form reducing gas stream, then iron oxide reduction efficiency is enhanced, but energy input requirements increase
Solution Approach 1:
The patent implements preliminary CO2 removal from the top gas stream before heating and recirculation. By removing CO2 in advance, the system enhances the effectiveness of subsequent heating and reduction processes, ensuring that the energy input is used more efficiently for iron oxide reduction rather than being consumed by CO2-related reactions.
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 method enhances the efficiency of iron oxide reduction to metallic iron, allowing for control of carbon content and temperature in the resulting direct reduced iron (DRI), reduces energy consumption, and minimizes CO2 emissions by optimizing the use of COG and BOFG.
Implementation Method 1
removing carbon dioxide from the top gas stream using a carbon dioxide removal unit
Implementation Method 2
heating the top gas stream in a gas heater to form a reducing gas stream
Implementation Method 3
reacting the preheated COG stream in a thermal reactor system to form the synthesis gas stream
Implementation Method 4
a thermal reactor system comprises a hot oxygen burner and a nozzle that processes oxygen and a fuel, wherein the oxygen and fuel are combined in the hot oxygen burner
Implementation Method 5
Both COG and BOFG contain significant percentages of carbon monoxide (CO) and hydrogen (H2), which are the primary reductants for reducing iron oxide to metallic iron
Data Source
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AI summary
Novel systems and methods are described for reducing iron oxide to metallic iron in an integrated steel mill or the like that has a coke oven and/or an oxygen steelmaking furnace. More specifically, the present invention relates to novel systems and methods for reducing iron oxide to metallic iron using coke oven gas (COG) or COG and basic oxygen furnace gas (BOFG).