Ammonia has various advantages especially in direct reduction of iron, making it a potential tool to decarbonize the steel sector.
In an article posted in ChemEurope, it is given that ammonia can be a good hydrogen carrier. The article conveys that
- Ammonia can also be used for direct reduction of iron that helps ammonia overcome any deficiency in hydrogen
- In contrast to hydrogen-based reduction, nitrides form during cooling in ammonia, which could protect the sponge iron from corrosion and make it easier to handle.
- Liquefaction cost for Ammonia is low.
- Ammonia can be directly used to reduce iron ores without cracking it into hydrogen and nitrogen. Avoiding this cracking process can reduce the overall costs by 18%.
To modify existing furnaces for ammonia-based steel production, specific changes are required in various components of the steelmaking process. Below is a detailed list of modifications needed for each component:
1. Reactor/Furnace Design
- Ammonia Injection System: Install specialized gas injection systems capable of introducing ammonia uniformly into the reactor. This ensures optimal contact with iron ore.
- Temperature Regulation: Enhance temperature control systems to maintain the necessary reaction temperatures (around 700°C) for effective ammonia decomposition and iron ore reduction.
- Reactor Configuration: Consider modifications to the reactor configuration, such as moving from a conventional design to a packed bed or fluidized bed reactor, to facilitate better gas-solid interactions.
2. Gas Handling Systems
- Gas Distribution Manifold: Upgrade or install gas distribution manifolds to ensure even distribution of ammonia and its decomposition products throughout the reactor.
- Heat Exchangers: Incorporate heat exchangers to recover heat from the reaction and maintain optimal temperatures, which can also help in the efficient operation of the ammonia decomposition process.
3. Catalyst and Reaction Medium
- Catalyst Selection: Implement catalysts that are effective for ammonia decomposition, such as ruthenium-based catalysts, which can operate efficiently at lower pressures and temperatures compared to traditional iron-based catalysts.
- Reaction Bed Materials: Use materials in the reaction bed that can withstand the corrosive nature of ammonia and its decomposition products, ensuring longevity and efficiency.
4. Post-Processing Adjustments
- Nitrides Management: Modify downstream processing systems to effectively manage and remove nitrides formed during the reduction process, ensuring the quality of the final steel product.
- Integration with Existing Processes: Evaluate how the ammonia-based process can be integrated with existing steelmaking processes, potentially requiring adjustments to downstream melting and refining operations.
Interestingly, we have some other posts related to this content:
Green Ammonia’s Role in Hydrogen Market: Green ammonia projects face evolving prospects. Selling to existing ammonia market may be better than conversion to hydrogen due to cost and efficiency concerns.
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