Method for direct reduction in a fluidized bed

Patent metadata

Field	Value
Publication number	US-2022145412-A1
Application number	US-202017438529-A
Country	US
Kind code	A1
Filing date	Mar 12, 2020
Priority date	Mar 15, 2019
Publication date	May 12, 2022
Grant date	—

Abstract

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 H 2 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 d 30 of the oxidic iron carrier particles introduced into the fluidized bed, it is above the theoretical suspension velocity U t and is less than or equal to U max .

First claim

1 - 15 . (canceled)

16 . A process of direct reduction of oxidic iron-bearing particles to a reduction product in a fluidized bed, comprising:
flowing in crosscurrent a reduction gas containing 30-100 mol % of hydrogen H 2 through the fluidized bed; wherein the oxidic iron-bearing particles introduced into the fluidized bed have a grain size of not more than 200 micrometers to an extent of at least 90% by mass; wherein a 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 it is above the theoretical fluidization velocity U t and not more than U max for the grain size d=d 30 of the oxidic iron-bearing particles introduced into the fluidized bed; wherein a theoretically predicted value U t for a grain size d is found from:

U
t

=

√

(

4
3

*

(

ρ
⁢

⁢
p

-

ρ
⁢

⁢
g

)

ρ
⁢

⁢
g

*

d
*
g

Cw

)

with
⁢

⁢
Cw

=

24
Re

+

4

Re

+
0.4

and with

Re
=

ρ
⁢

⁢
g
*

U
t

*
d

μ

;

and
wherein U max is calculated from an actual correlation found between particle size and fluidization velocity for a particle size d=d 30 :
U max =(40000* d ){circumflex over ( )}2.78.

17 . The process as claimed in claim 16 , wherein the process is conducted at a temperature between 773 K and 1123 K.

18 . The process as claimed in claim 16 , wherein the process is conducted under a slightly elevated pressure compared to the environment.

19 . The process as claimed in claim 16 , wherein d 30 is not more than 110 micrometers for the oxidic iron-bearing particles introduced into the fluidized bed.

20 . The process as claimed in claim 16 , wherein the oxidic iron-bearing particles introduced into the fluidized bed are between 15 micrometers and 100 micrometers to an extent of at least 50% by mass.

21 . The process as claimed in claim 16 , wherein the oxidic iron-bearing particles are present at smaller than 10 micrometers μm with fractions of not more than 30% by mass.

22 . The process as claimed in claim 16 , wherein the fluidized bed has different zones with different bed heights.

23 . The process as claimed in claim 16 , wherein the bed height in the fluidized bed is 0.1-0.5 m.

24 . The process as claimed in claim 23 , wherein the bed height in the fluidized bed is 0.3-0.4 m.

25 . The process as claimed in claim 16 , wherein a gas dwell time of the reduction gas in the fluidized bed is 0.1 second to 10 seconds.

26 . The process as claimed in claim 25 , wherein the gas dwell time of the reduction gas in the fluidized bed is 1 second to 2 seconds.

27 . The process as claimed in claim 16 , wherein spent reduction gas exiting from the fluidized bed, after processing, is recirculated again into the fluidized bed as a component of the reduction gas.

28 . The process as claimed in claim 16 , wherein the fluidized bed is supplied with the same reduction gas throughout.

29 . The process as claimed in claim 16 , wherein different zones of the fluidized bed are supplied with different reduction gases.

30 . A signal processing device with a machine-readable program code, wherein the signal processing device has control commands for performance of the process as claimed in claim 16 .

31 . A machine-readable program code for a signal processing device, wherein the program code has control commands that cause the signal processing device to perform the process as claimed in claim 16 .

32 . A storage medium having a machine-readable program code as claimed in claim 31 stored thereon.

33 . A process of direct reduction of oxidic iron-bearing particles to a reduction product in a fluidized bed, comprising:
flowing in crosscurrent a reduction gas containing 30-100 mol % of hydrogen H 2 through the fluidized bed; limiting a grain size of the oxidic iron-bearing particles introduced into the fluidized bed to not more than 200 micrometers to an extent of at least 90% by mass; and setting a superficial velocity U of the reduction gas flowing through the fluidized bed to between 0.05 m/s and 1 m/s such that it is above the theoretical fluidization velocity U t and not more than U max for the grain size d=d 30 of the oxidic iron-bearing particles introduced into the fluidized bed; wherein a theoretically predicted value U t for a grain size d is found from:

U
t

=

√

(

4
3

*

(

ρ

Assignees

• Primetals Technologies Austria GmbH

Inventors

• Eisl Roland
• Hiebl Bernhard
• Ofner Hanspeter
• Rein Norbert
• Wurm Johann

Classifications

• F27B15/18

  Arrangements of controlling devices · CPC title

• F27B15/10

  Arrangements of air or gas supply devices · CPC title

• F27B15/09

  Arrangements of devices for discharging · CPC title

• C21B13/0033 Primary

  In fluidised bed furnaces or apparatus containing a dispersion of the material · CPC title

• C21B13/0073

  Selection or treatment of the reducing gases · CPC title