Fluidized Bed Direct Reduction of Fine Iron Particles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fluidized bed processes for direct reduction of oxidic iron-bearing particles face challenges with high reactor area requirements and operational complexity due to small grain sizes, leading to low usable gas velocities and increased discharge of particles, which reduces efficiency and increases construction and safety demands.
Innovation Solution
A process where oxidic iron-bearing particles with at least 90% by mass having a grain size of not more than 200 micrometers are reduced in a fluidized bed with a reduction gas containing 30-100 mol % hydrogen flowing in crosscurrent, with superficial velocities set between 0.05 m/s and 1 m/s, above the theoretical fluidization velocity but not exceeding the maximum velocity, to minimize particle discharge and maintain efficient fluidization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas velocity is increased to increase mass flow rate of reduction gas, then productivity is improved, but particle discharge from fluid bed increases
Solution Approach 1:
The patent changes the particle size parameter to predominantly fine particles (≤200 μm) and adjusts the gas velocity parameter to a specific range (0.3-1.5 m/s) that maintains fluidization while minimizing discharge. This parameter optimization allows operating at higher gas velocities for improved productivity without excessive particle loss.
Solution Approach 2:
The patent employs dynamic control of gas velocity within an optimized range rather than using fixed high velocities. The fluidized bed operates in a controlled dynamic state where gas flow is sufficient to maintain suspension and mass transfer but below the point of excessive particle entrainment and discharge.
2Area of stationary object
If gas velocity is increased to reduce reactor area, then device complexity is reduced, but particle discharge increases
Solution Approach 1:
By changing the particle size distribution parameter to predominantly fine particles and optimizing the gas velocity parameter, the patent achieves efficient mass transfer at moderate velocities. This allows using a compact reactor design without incurring high particle discharge penalties that would occur at much higher velocities.
3Productivity
If small grain size particles are used to increase exchange area, then mass transfer rate is improved, but fluidization velocity decreases
Solution Approach 1:
The patent optimizes the particle size parameter to a specific fine range ( predominantly ≤200 μm) that provides high surface area to volume ratio for enhanced mass transfer. Concurrently, the gas velocity parameter is adjusted to an optimized range that maintains proper fluidization of these fine particles, balancing mass transfer enhancement with adequate fluidization velocity.
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 allows for higher gas velocities than expected, reducing particle discharge and maintaining efficient fluidization, thereby lowering reactor area needs and operational complexity while achieving high metallization levels of the reduction product, thus enhancing the economic viability and safety of the process.
Implementation Method 1
reduction gas flow is counter to gravity through solid-state particles—i.e. the oxidic iron-bearing particles, for example bulk iron ore material. This puts the solid-state particles in a fluidized, i.e. suspended, state
Implementation Method 2
on account of the high exchange area present between the solid state and gas, comparatively high mass and heat transfer rates are achieved
Implementation Method 3
on account of the high exchange area present between the solid state and gas, comparatively high mass and heat transfer rates are achieved
Implementation Method 4
direct reduction of oxidic iron-bearing particles to a reduction product in a fluidized bed through which a reduction gas containing 30-100 mol % of hydrogen H2 flows
Implementation Method 5
comparatively high mass and heat transfer rates are achieved. This correspondingly results in high specific conversion rates in the reduction reactions
Data Source
AI summary
The invention relates to a method for the direct reduction of oxidic iron carrier particles to a reduction product in a fluidized bed through which a reduction gas containing 30-100 mol % hydrogen H2 flows in crossflow. At least 90% by mass of oxidic iron carrier particles introduced into the fluidized bed have a particle size of less than or equal to 200 micrometers. The superficial velocity U of the reduction gas flowing through the fluidized bed is set between 0.05 m/s and 1 m/s such that, for the particle size d equal to d30 of the oxidic iron carrier particles introduced into the fluidized bed, it is above the theoretical suspension velocity Ut and is less than or equal to Umax.