# Development of a Moving-Bed Ironmaking Process for Direct Gaseous Reduction of Iron Ore Concentrate

^{*}

## Abstract

**:**

## 1. Introduction

_{2}are being developed [4,5,6,7,8,9]. Some of these processes have been successfully commercialized [10] by replacing the coke making process, lowering energy requirements and CO

_{2}emissions, and using iron ore fines or concentrates directly without pelletization. In spite of the recent successes in alternative ironmaking, BF technology is still the predominant industrial method.

## 2. Process Concept

## 3. Configuration of a Horizontal Moving-Bed Furnace

## 4. Hydrogen Reduction Kinetics of Concentrate Particles

^{−1}K

^{−1}, T is in K, p is in atm, and t is in seconds. It should be noted that the rate decreased with temperature in the range 650–800 °C. This phenomenon has been observed previously [13,14,15,16] for iron oxide reduction.

## 5. Incorporation of Interparticle Diffusion in the Rate Analysis

^{−1}K

^{−1}, T is in K, p is in atm, and t is in seconds.

_{p}is a shape factor, which has a value of 3 for a sphere and 1 for a flat bed.

_{m}is the mass transfer coefficient.

## 6. Design of a Horizontal Moving-Bed Furnace

#### 6.1. Model Formulation

- (a)
- The overall reaction is ${H}_{2}\left(g\right)+\frac{1}{4}F{e}_{3}{O}_{4}\left(s\right)={H}_{2}O\left(g\right)+\frac{3}{4}Fe\left(s\right)$, which in general notation is represented by $A\left(g\right)+bB\left(s\right)=cC\left(g\right)+dD\left(s\right)$.
- (b)
- The reduction occurs under isothermal conditions.
- (c)
- The solid and reducing gas are in plug flow and steady state.
- (d)
- The reactor has a uniform cross-sectional area.
- (e)
- Mass transfer between the gas and the top of the bed is fast.

_{o}is the final value of X at the gas entrance; G

_{g}and G

_{s}are the total input rate per unit cross-sectional area of the reactor of gas (including hydrogen, water vapor, and inert gas, if any) and the input molar rate per unit cross-sectional area of the reactor of solid B, respectively; K is the equilibrium constant for wüstite reduction; x is the mole fraction of gaseous species; n = 1.5 is the Avrami parameter in the nucleation-and-growth kinetics equation; k

_{o}is the pre-exponential factor in the rate equation; P is the total pressure of the gas phase; ε

_{p}is the porosity of the product iron layer; and ρ

_{B}is the true molar density of B.

#### 6.2. Design of Industrial Reactors

_{o}= 0.95. The normalized driving force of reducing gas, θ, is set at 0.3 at the gas outlet. The reactor is assumed to have a width of 5 m and a height of 3 m.

## 7. Concluding Remarks

- (1)
- The proposed technology for a modest-scale ironmaking operation with a production rate of 0.1 Mtpy can be operated at temperatures between 650 and 1000 °C.
- (2)
- The design parameters and the operating conditions for the horizontal moving-bed reactor were established.
- (3)
- A simple model for a moving-bed reactor that indicated that the proposed ironmaking technology has industrial potential was formulated.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Sketch of a counter-current horizontal moving-bed reactor. p

_{A}and p

_{C}are the partial pressures of H

_{2}and H

_{2}O, respectively; G

_{g}and G

_{s}are the total input rate per unit cross-sectional area of the reactor of gas (including hydrogen, water vapor, and inert gas, if any) and the input molar rate per unit cross-sectional area of the reactor of solid B, respectively; y is the distance from the gas inlet; X is the fractional removal of oxygen from iron oxide; and a represents the cross-sectional area of the reactor.

**Figure 4.**Comparison of time for 90% conversion from the rate equations with experimental data. Time is in seconds.

**Figure 5.**Illustration of the reaction of a flat bed of particles under (

**a**) one-step diffusion control and (

**b**) mixed control.

Component | Wt.% |
---|---|

Total Iron | 70.65 |

SiO_{2} | 1.87 |

Al_{2}O_{3} | 0.13 |

CaO | 0.27 |

MgO | 0.13 |

MnO | 0.11 |

Cr_{2}O_{3} | 0.11 |

K_{2}O | 0.01 |

Na_{2}O | 0.1 |

TiO_{2} | 0.01 |

ZrO_{2} | 0.03 |

P | 0.01 |

S | 0.02 |

C | 0.24 |

Sr | 0.01 |

**Table 2.**Effect of bed thickness and temperature on residence time, reactor length, speed of bed, and gas velocity for a moving-bed reactor with a production rate of 0.1 Mtpy.

Temperature (°C) | Bed Thickness (cm) | Residence Time (min) | Reactor Length (m) | Bed Speed (cm/min) | Gas Velocity (cm/s) |
---|---|---|---|---|---|

1000 | 1 | 23.5 | 5.76 | 24.5 | 182 |

2 | 92 | 11.3 | 12.3 | 188 | |

5 | 571 | 28.1 | 4.91 | 211 | |

900 | 1 | 28.7 | 7.03 | 24.5 | 182 |

2 | 108 | 13.3 | 12.3 | 188 | |

5 | 661 | 32.4 | 4.91 | 211 | |

850 | 1 | 32.1 | 7.87 | 24.5 | 183 |

2 | 118 | 14.5 | 12.3 | 189 | |

5 | 718 | 35.3 | 4.91 | 212 | |

650 | 1 | 95 | 23.3 | 24.5 | 196 |

2 | 371 | 45.6 | 12.3 | 203 | |

5 | 2303 | 113.1 | 4.91 | 227 |

**Table 3.**Design parameters or operating conditions for horizontal moving-bed reactors (0.1 Mtpy) at different temperatures.

Temperature (°C) | 1000 | 900 | 850 | 650 |
---|---|---|---|---|

Characteristic Length (cm) | 2 | 2 | 2 | 2 |

Gas Flow Rate (Nm^{3}/h) | 20,350 | 20,400 | 20,500 | 21,950 |

Residence Time (min) | 92 | 108 | 118 | 371 |

Speed of Grate (cm/min) | 12.3 | 12.3 | 12.3 | 12.3 |

Reactor Length (m) | 11.3 | 13.3 | 14.5 | 45.6 |

Reactor Volume (m^{3}) | 170 | 200 | 218 | 684 |

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**MDPI and ACS Style**

Sohn, H.Y.; Roy, S.
Development of a Moving-Bed Ironmaking Process for Direct Gaseous Reduction of Iron Ore Concentrate. *Metals* **2022**, *12*, 1889.
https://doi.org/10.3390/met12111889

**AMA Style**

Sohn HY, Roy S.
Development of a Moving-Bed Ironmaking Process for Direct Gaseous Reduction of Iron Ore Concentrate. *Metals*. 2022; 12(11):1889.
https://doi.org/10.3390/met12111889

**Chicago/Turabian Style**

Sohn, Hong Yong, and Syamantak Roy.
2022. "Development of a Moving-Bed Ironmaking Process for Direct Gaseous Reduction of Iron Ore Concentrate" *Metals* 12, no. 11: 1889.
https://doi.org/10.3390/met12111889