Hydrogen-Reduced DRI Pellets With Low Reactivity and High Strength
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Solution Overview
Problem
Traditional direct reduced iron (DRI) pellets are not well suited for handling, transport, and storage due to high porosity, low density, and reactivity, leading to corrosion, oxidation, and potential self-ignition, and require additional processes like briquetting to mitigate these issues, which adds cost and complexity.
Innovation Solution
Production of DRI pellets using hydrogen as a reducing gas, achieving metallization greater than 97%, low carbon content, median pore diameter of at least 1.5 μm, and porosity less than 60%, resulting in improved mechanical strength and reduced reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional shaft-based direct reduction is used to produce DRI pellets, then the production process is simple and cost-effective, but the DRI pellets have high porosity, low density, and high reactivity leading to corrosion, oxidation, and self-ignition risks
Solution Approach 1:
The patent applies parameter changes by modifying the reduction conditions (temperature, gas composition, residence time) to produce DRI pellets with controlled porosity and metallization degree. This resolves the contradiction by achieving both ease of manufacture through continuous shaft-based reduction and improved reliability through optimized physical and chemical parameters of the DRI pellets
2Productivity
If DRI pellets are produced with high porosity for easy reduction, then the reduction efficiency is high, but the mechanical strength is low and the pellets break down during handling to produce reactive dust
Solution Approach 1:
The patent optimizes reduction parameters including temperature profile, gas flow rates, and residence time to achieve the right balance between porosity for efficient reduction and sufficient mechanical strength for handling. The continuous shaft-based reduction process allows precise control of these parameters throughout the reduction zone
3Reliability
If additional processing steps like briquetting are applied to DRI pellets, then the reactivity and safety issues are mitigated, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by optimizing the reduction process itself to produce DRI pellets with inherently lower reactivity and better stability, eliminating the need for subsequent briquetting or passivation treatments. The reduction conditions are pre-configured to achieve the desired product properties directly
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 DRI pellets exhibit superior mechanical strength, slower aging, and reduced reactivity, enabling safe handling, transport, and storage without the need for additional processing steps like briquetting, and are suitable for use as a feedstock in steel production.
Implementation Method 1
Production of DRI pellets using hydrogen as a reducing gas
Implementation Method 2
Corrosion and oxidation reactions of DRI can also produce hydrogen, an explosive gas which is lighter than air, and carbon monoxide, a highly toxic gas
Implementation Method 3
Many of these reactions are exothermic, leading to self-heating and eventually self-ignition and fires if not controlled
Data Source
AI summary
The disclosure relates to direct reduced iron (DRI) pellets, wherein the DRI pellets have an average metallization of greater than or equal to 97%. The DRI pellets are either essentially free of carbon, or alternatively they comprise less than or equal to 2 wt % carbon. The DRI pellets are further characterised in that they (i) have a median pore diameter of greater than or equal to 1.5 μm; and/or (ii) have an average BET surface area of less than or equal to 0.5 m2/g; and/or (iii) have an average porosity of less than or equal to 60%. The disclosure further relates to uses of such DRI pellets.