Process for manufacturing a slag conditioning agent for steel desulfurization

Patent metadata

Field	Value
Publication number	US-2021395846-A1
Application number	US-201917309680-A
Country	US
Kind code	A1
Filing date	Dec 17, 2019
Priority date	Dec 17, 2018
Publication date	Dec 23, 2021
Grant date	—

Abstract

Process for manufacturing a slag conditioning agent for steel desulfurization wherein a dried slag material obtained from secondary steelmaking process is mixed with quicklime particles to produce a slag conditioning agent.

First claim

1 . Process for manufacturing a slag conditioning agent for steel desulfurization comprising the steps of:
providing a slag material obtained from secondary steelmaking process, in particular a slag material obtained after an Al-killing steel process, said slag material comprising at least calcium, aluminum iron, moisture and a phase of calcium aluminate; mixing said slag material with quicklime particles having a predetermined maximum particle size, and drying said slag material by having at least a part of the quicklime particles reacting at least partially with a moisture contained in the slag material thereby obtaining a first blend comprising slag material, hydrated lime and optionally unreacted quicklime, sieving said first blend at a cut-size superior or equal to said predetermined maximum particle size of said quicklime to remove a passing fraction of said first blend from a retained dried fraction of said first blend, said passing fraction having a maximum particle size lower than said cut-size and comprising a majority of said hydrated lime; and mixing said retained dried fraction with a composition having an Al 2 O 3 mass fraction of at least 80 wt % relative to the weight of the composition, and collecting a slag conditioning agent having an equivalent mass ratio CaO/Al 2 O 3 comprised between 0.55 and 1.5.

2 . Process according to claim 1 wherein the said slag material comprising at least calcium, aluminum iron, moisture and a phase of calcium aluminate comprises:
an amount of calcium measured by X-ray fluorescence expressed in equivalent CaO comprised between 20 and 45 wt % relative to the weight of the slag material;
an amount of aluminum measured by XRF expressed in equivalent Al 2 O 3 comprised between 10 and 45 wt % relative to the weight of the slag material; and
an amount of iron measured by XRF expressed in equivalent Fe 2 O 3 of at least 2 wt % relative to the weight of the slag material,
and wherein at least a part of said amount of calcium and at least a part of said amount of aluminum is present in said calcium aluminate phase

3 . Process according to claim 1 , wherein the said slag material comprises up to 20 wt % of iron expressed in equivalent Fe 2 O 3 relative to the weight of the slag material.

4 . Process according to claim 1 , wherein the moisture of said slag material is present at a moisture content less than 10 wt % relative to the weight of the slag material.

5 . Process according to claim 1 , wherein the said quicklime particles comprises at least particles having a reactivity with water t 60 according to the EN 459-2:2010E, less than 2 min.

6 . Process according to claim 1 , wherein the said quicklime particles comprises at least lime kiln dust particles.

7 . Process according to claim 1 , wherein the said quicklime particles have a BET specific surface area greater than 0.8 m 2 /g measured by nitrogen adsorption manometry after vacuum degassing at 190° C. for at least 2 hours, calculated by the multiple-point BET method as described in standard ISO 9277:2010 E.

8 . Process according to claim 1 , wherein the said slag material is crushed and optionally sieved to have a maximum particle size below a maximum value (b).

9 . Process according to claim 1 , wherein the said slag material is sieved to have a minimum particle size above a minimum value (a).

10 . Slag conditioning agent for a process of steel desulfurization, comprising phases of calcium aluminate and an equivalent mass ratio CaO/Al 2 O 3 comprised between 0.55 and 1.5, said slag conditioning agent having an iron content measured by XRF and expressed in equivalent Fe 2 O 3 of at least 2 wt %, and an aluminum content expressed in equivalent Al 2 O 3 of at least 30 wt %.

11 . Slag conditioning agent according to claim 10 , comprising an amount of calcium ferrites measured by XRD of at least 1 wt % relative to the weight of the slag conditioning agent.

12 . Slag conditioning agent according to claim 10 , having a particle size distribution comprised between a minimum value and a maximum value, said minimum value being of at least 1 mm.

13 . Slag conditioning agent according to claim 10 , having a particle size distribution comprised between a minimum value and a maximum value, said maximum value being of maximum 20 mm.

14 . (canceled)

15 . Use of slag conditioning agent according to claim 10 in a process of steel desulfurization, at an amount of 2 to 16 kg of slag conditioning agent/ton of steel, in combination with elemental aluminum in amounts less than 100 g/t of steel, and an amount of quicklime of less than 12 kg/t steel.

Assignees

• Lhoist Rech Et Developpement Sa

Inventors

• Perrin Eric
• Chunlamani Souliyann

Classifications

• C21C5/54

  Processes yielding slags of special composition · CPC title

• C21B2400/028

  with the permanent addition of cooled slag or other solids · CPC title

• C21C1/025

  Agents used for dephosphorising or desulfurising · CPC title

• C21C7/0645 Primary

  Agents used for dephosphorising or desulfurising · CPC title

• C21C5/36

  Processes yielding slags of special composition · CPC title