Ammonia Dissociation Reducing Gas for Low-CO2 Direct Reduced Iron
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Solution Overview
Problem
Existing direct-reduction processes for producing direct-reduced iron (DRI) and subsequent steel production in Electric Arc Furnaces (EAFs) have high CO2 emissions, which are difficult to reduce in regions lacking suitable energy resources for producing green hydrogen.
Innovation Solution
A direct-reduction process using ammonia as a feedstock to produce hydrogen-containing reducing gas, which is then used to reduce iron oxides in a direct-reduction reactor, with nitrogen acting as a ballast gas to prevent NOx formation, and optionally using hydrocarbons and steam to enhance the reducing gas composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If natural gas reforming is used to produce reducing gas, then the reducing gas can be produced efficiently, but CO2 emissions are high
Solution Approach 1:
The invention changes the chemical composition parameters of the reducing gas from hydrocarbon-based (CO and H2 from natural gas reforming) to ammonia-based (H2 from ammonia dissociation). This parameter change eliminates carbon-containing compounds from the reducing gas, thereby eliminating CO2 emissions while maintaining reducing capability through hydrogen produced from ammonia dissociation.
Solution Approach 2:
The invention substitutes the chemical mechanism of natural gas reforming (which produces CO2) with ammonia dissociation (which produces only H2 and N2). This substitution replaces a carbon-intensive chemical process with a carbon-free chemical process, eliminating the harmful CO2 byproduct while maintaining the function of producing reducing gas.
2Object-generated harmful factors
If green hydrogen is used directly as reducing agent, then CO2 emissions are reduced, but transportation and storage become difficult
Solution Approach 1:
The invention uses ammonia as an intermediary carrier for hydrogen. Instead of transporting and storing hydrogen directly (which is difficult due to its low density and high flammability), the process transports and stores ammonia (which has favorable physical and chemical properties for transportation and storage). At the point of use, ammonia is dissociated to release hydrogen for the reducing reaction, thus solving the transportation and storage problem while maintaining the benefits of green hydrogen.
Solution Approach 2:
The invention discards the hydrogen from its molecular form in ammonia and recovers it at the point of use through dissociation. The ammonia is transported and stored in a stable form, then at the direct reduction plant, the ammonia is dissociated to recover the hydrogen which is immediately used for reducing iron oxides. This approach separates the transportation/storage function from the reaction function, solving the operational difficulties.
3Object-generated harmful factors
If ammonia is used as feedstock, then CO2 emissions are reduced, but NOx formation may occur
Solution Approach 1:
The invention creates an inert atmosphere using nitrogen, which is the primary component of the reducing gas produced from ammonia dissociation. The nitrogen acts as a diluent and inert gas that suppresses combustion reactions and prevents the formation of NOx. By maintaining a reducing atmosphere rich in H2 and N2 and poor in O2, the process eliminates the conditions necessary for NOx formation while preserving the benefits of ammonia-based reducing gas.
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 process significantly reduces CO2 emissions by up to 95% compared to traditional methods, enables widespread use of green hydrogen, and avoids NOx formation, making it suitable for regions with less sustainable energy sources.
Implementation Method 1
In the gas reformer, the NH3 in the gas feed undergoes the following dissociation reaction 2NH3 → N2 + 3H2
Implementation Method 2
Inside said direct-reduction reactor, the iron ore is subjected to reduction of the iron oxides contained within by reaction with the reducing gas
Data Source
Figure 1
AI summary
Direct iron-ore reduction process whereby an NH3-containing a gas feed (24a) is supplied to a gas reformer (25) and reformed therein so as to obtain a hydrogen-containing reducing gas (25a, 25b) which, at least in part, is supplied to a direct-reduction reactor (1) in which iron ore (2) is subjected to direct reduction with the reducing gas (25a, 25b) so as to obtain direct reduced iron (30) and whereby during the reforming of the hydrogen-containing reducing gas (25a), the NH3 in the gas feed (24a) is subjected to the dissociation reaction 2 NH3 — > N2 + 3H2.