AU5681496A

AU5681496A - Process for forming shaped articles

Info

Publication number: AU5681496A
Application number: AU56814/96A
Authority: AU
Inventors: Maroun George Rahme
Original assignee: NU ROCK TECHNOLOGY Pty Ltd
Current assignee: RAHME MICHELLE MAROUN
Priority date: 1996-05-27
Filing date: 1996-05-27
Publication date: 1996-12-11
Anticipated expiration: 2016-05-27
Also published as: AU724028B2

Description

Process for Forming Shaped Articles

Technical Field

The present invention is directed towards a process for preparation of shaped articles for the recycling of various wastes from steelmaking furnaces such as blast furnaces and steel furnaces or from mines. The invention also relates to a process for treatment and disposal of waste materials by convening them into shaped articles or solid aggregates. The shaped articles may be fed back into the furnace as an artificial iron ore

Background Art

Conventionally the wastes from steelmaking processes and mining operations are stockpiled and various disposal methods are employed. In an alternative method cement or sintering is used to bind together waste particles. However this is unsatisfactory when fed back into the furnace due to the impurities that are introduced.

The present invention is directed to a process for the production of an alternative means of recycling the wastes with low energy consumption. Large amounts of furnace flue dust, sinter fines, caster mill scale, hot shrink mill scale, B.O.S. furnace flue fines, plate mill scale, burner fines, limestone fines, dolomite fines, fly ash, iron ore fines, iron ore dusts and other waste materials are generated during the steel or mining process and the continued retention and storage of further amounts of this waste material is problematic.

Disclosure of the Invention

The present inventor has recognised that there exists a need for a process that is capable of re-solidifying all the waste material containing high amounts of iron and producing an artificial iron ore that is to be fed back into the furnace and that would be convenient, simple and cost saving. The present invention provides a process for producing an artificial iron ore suitable as a raw material in iron and steelmaking, which process comprises the steps of (1) treating a waste material containing iron with an aqueous alkaline material at pH > 7 for a time sufficient to convert at least a part of any silica contained within the waste to silicate; (2) mixing the treated waste with silica and/or a silicate and optionally further waste materials and/or fillers to form a mixture containing at least about 50% (dry weight) of iron; (3) forming the mixture into a shape; and (4) allowing the shaped mixture to harden to thereby form an artificial iron ore.

In another embodiment, the invention provides a method for producing a solid calcium and/or magnesium containing feed for an iron or steel making process, which method comprises the steps of (1) mixing limestone or dolomite fines or fly ash with silica and/or a silicate and with iron oxide or a compound of iron, and optionally further waste materials and/or fillers; (2) forming the mixture into a shape; and (3) allowing the shaped mixture to harden to thereby form a solid calcium and/or magnesium containing feed. In further embodiments of the invention there are provided solid paniculate feedstocks for iron or steel making made by the process or the method of the invention.

It is preferred that the anificial iron ore and the solid paniculate feedstocks be of sufficient strength and/or weight in order to be able to break through the solid slag crust when fed to a furnace.

It is preferred that the artificial iron ore will contain about 45 % to about 75 % of iron, preferably about 65 % to about 75 % of iron.

Preferably the waste material is treated with an aqueous alkaline material at pH about 11 to about 14. The amount of silica and/or silicate either produced and/or added is preferably about

1.5 to 15 % , more typically about 3 to 15 % by weight of the waste material, most preferably about 1.5 to 4% . A prefened silicate is sodium silicate.

The artificial iron ore will preferably contain from about 15 % to about 20% lime or dolomite which may conveniently derived from limestone fines, dolomite fines and/or fly ash.

Preferred waste materials for use in the present invention include blast furnace flue dust, sinter fines, caster mill scales, hot shrink mill scale, B.O.S. furnace flue fines, plate mill scale, burner fines, limestone fines, iron ore fines, iron ore dust, dolomite fines, fly ash and steel slags or other pozzulanic materials. If the end product is to be in the form of a shaped article the mixture may be compacted and shaped prior to curing. Compaction and shaping generally improves the strength of the final product. In some applications the strength of the final product may not be as important and it is not necessary to compact the mixture. This is generally the case when the final product is an aggregate material. Typically, the waste material remains in contact with the alkali from about 1 to about 48 hours, preferably about 12 to 48 hours.

In waste materials which contain sufficient amounts of silica, the reaction between the alkali and silica may produce sufficient silicate such that it may not be necessary to add further silicate.

Best Mode or Modes of Carrying out the Invention

Typically to produce an artificial iron ore suitable as a raw material in iron and steelmaking, about 50 to 100kg waste material is treated with about 0.5 to 3L aqueous alkali material such as sodium hydroxide solution. Typically the waste material is treated for about 1 to 48 hours, usually up to 24 hours if required. Usually about 0 to 50kg filler may be added to the waste material and mixed for about 1 to 10 minutes. The waste material and filler are usually blast furnace flue dust, sinter fines, caster mill scales, hot shrink mill scale, B.O.S. furnace flue fines, plate mill scale, burner fines, limestone fines, iron ore fines, iron ore dust, dolomite fines, fly ash and steel slags or other pozzulanic materials. Usually 1 to 10L of a 50% solution of silica or silicate is added to the mixture and mixed thoroughly. Typically the silicate is sodium silicate. The mixture is usually pressed and/or vibrated in a brick mould at about 1 to 30T pressure.

Typically to produce a solid calcium and/or magnesium containing feed for an iron or steel making process, about 50 to 100kg limestone or dolomite fines or fly ash is mixed with about 1 to 10L of a 50% solution of silica or silicate. Typically the silicate is sodium silicate. Iron oxide or a compound of iron is added to the mixture. Typically the mixture is treated with about 0.5 to 3L aqueous alkali material such as sodium hydroxide solution. Typically the limestone or dolomite fines or fly ash is treated for about 1 to 48 hours, usually up to 24 hours if required. Usually about 0 to 50kg waste material/filler may be added to the limestone or dolomite fines or fly ash and mixed for about 1 to 10 minutes. The waste material and filler are usually blast furnace flue dust, sinter fines, caster mill scales, hot shrink mill scale, B.O.S. furnace flue fines, plate mill scale, burner fines, limestone fines, iron ore fines, iron ore dust, dolomite fines, fly ash and steel slags or other pozzulanic materials. The mixture is usually pressed and/ or vibrated in a brick mould at about 1 to 30T pressure.

When the final product is to be a shaped article, it is highly desirable that the mixture be compacted prior to curing. The compaction has been found to increase substantially the final strength of articles formed by the method according to this invention. The. compaction may be brought about by compressing or extruding the mixture or by the use of a compaction roller. Alternatively articles may be slip cast to bring about the desired compaction.

Once the shaped article is formed, it is allowed to cure in ambient air, preferably at a temperature of about 30°C. If desired, curing may be accelerated by the use of higher temperamres. Typically temperatures of about 50 to 100°C may be employed. The shaped article is usually of sufficient strength and weight to be used in the furnace as artificial iron ore.

As no heating is required in the formation of the shaped articles of the invention the energy requirements are quite low, thereby contributing to the relatively low cost of these shaped articles.

The invention will now be illustrated in the following examples which should not be construed as limiting on the scope of the invention.

Example 1

1. 27kg of sinter fines, 27kg B.O.S. flue dust, 27kg of caster mill scale. 10kg of limestone dust was mixed with water and 2L of 20% sodium hydroxide solution for five minutes and the mixture was kept for 24 hours.

2. 5kg of fly ash was added into the mixture and mixed together for two minutes.

3. 5L of 50% sodium silicate was then added to the mixture and thoroughly mixed. 4. The homogenised mass was then pressed and/or vibrated in a brick mould at 20T pressure. The test specimen formed was 75mm high and 110mm wide and 230mm long.

5. The pressed brick was dried in air at room temperature for 7 and 28 days then 5 cut in half and tested for its strength.

Example 2

The procedure of Example 1 was repeated using no fly ash and 10kg of limestone fines and 5kg of dolomite fines, sodium silicate was 5L.

Example 3 ι o The procedure and materials of Example 2 were repeated with the difference that the sodium silicate was 3L and waste was 15kg fly ash and no limestone or dolomite fines as in Example 2.

Example 4

1. 27kg of sinter fines, 27kg B.O.S. flue dust, 27kg of caster mill scale, 10kg of 15 limestone dust was mixed with water and 0.9L of 20% sodium hydroxide solution for two minutes and the mixture was kept for up to 24 hours if required.

2. 5kg of fly ash or granulate slag was added into the mixture and mixed together for two minutes.-

3. 2.4L of 50% sodium silicate was then added to the mixture and thoroughly 20 mixed.

4. The homogenised mass was then pressed and/or vibrated in a brick mould at IT to 30T pressure. The test specimen formed was 75mm high and 110mm wide and 230mm long.

5. The pressed/vibrated brick was dried in air at room temperature for 7 and 28 25 days then cut in half and tested for its strength.

Example 5 The procedure of Example 4 was repeated with the difference that the amount of sodium silicate was 2% and filler was 0kg instead of 5kg.

Example 6

30 The procedure of Example 4 was repeated using no fly ash or granulate slag and

10kg of limestone fmes and 5kg of dolomite fmes and 2L sodium silicate.

Example 7

The procedure and materials of Example 6 were repeated with 3L sodium silicate and 1.5kg fly ash as the filler with no limestone or dolomite fines as in Example 6.

35 Example 8

The procedure of Example 4 was repeated with 35kg iron ore fines, 35kg iron ore dust and 15kg limestone or dolomite fmes as the material.

Example 9 The procedure of Example 4 was repeated with 27kg mill scale. 27kg burner fines,

27kg plate mill scale and 15kg limestone or dolomite fines as material.

Example 10

The procedure of Example 4 was repeated with 75kg iron ore fines and 15kg limestone or dolomite fines as the material.

Example 11

The procedure of Example 4 was repeated using 75kg BOS flue dust and 15kg limestone or dolomite fines as the material.

Example 12

The procedure of Example 4 was repeated using 75kg sinter fines and 10kg limestone or dolomite fines as the material.

Example 13

The procedure of Example 4 was repeated using 75kg mill scale and 25kg limestone or dolomite fines as the material.

Example 14 The procedure of Example 4 was repeated using 75kg hot shrink mill scale and 10kg limestone or dolomite fines as the material.

Example 15

The procedure of Example 4 was repeated using 75kg dolomite and 10kg B.O.S. flue dust as the material.

Example 16

The procedure of Example 4 was repeated using 75kg limestone fines and 10kg sinter fmes as the material.

Claims

I . A process for producing an artificial iron ore suitable as a raw material in iron and steelmaking, which process comprises the steps of (1) treating a waste material containing iron with an aqueous alkaline material at pH > 7 for a time sufficient to convert at least a pan of any silica contained within the waste to silicate: (2) mixing the treated waste with silica and/or a silicate and optionally further waste materials and/or fillers to form a mixture containing at least about 50% (dry weight) of iron; (3) forming the mixture into a shape; and (4) allowing the shaped mixture to harden to thereby form an artificial iron ore.
2. The process for producing an artificial iron ore as claimed in claim 1 , wherein said artificial iron ore is of sufficient strength to break through a solid slag crust when fed into a furnace.
3. The process for producing an artificial iron ore as claimed in claim 1 , wherein said artificial iron ore contains about 45 % to 75 % by weight of iron.
4. The process for producing an artificial iron ore as claimed in claim 1 , wherein said waste material is blast furnace flue dust, sinter fines, caster mill scales, hot shrink mill scale, B.O.S. furnace flue fines, plate mill scale, burner fines, limestone fmes, iron ore fines, iron ore dust, dolomite fines, fly ash, steel slags or other pozzulanic materials.
5. The process for producing an artificial iron ore as claimed in claim 1 , wherein said pH is about 11 to about 14.
6. The process for producing an artificial iron ore as claimed in claim 1, wherein said waste material is in contact with said aqueous alkali material for about 1 to about 48 hours.
7. The process for producing an artificial iron ore as claimed in claim 1 , wherein said silica and/or silicate is about 1.5 to 15 % by weight of the waste material and said silicate is sodium silicate.
8. The process for producing an artificial iron ore as claimed in claim 1 , wherein said artificial iron ore contains from about 15 % to about 20% by weight of lime or dolomite.
9. A method for producing a solid calcium and/ or magnesium containing feed for an iron or steel making process, which method comprises the steps of (1) mixing limestone or dolomite fines or fly ash with silica and/or a silicate and with iron oxide or a compound of iron, and optionally further waste materials and/ or fillers; (2) forming the mixture into a shape; and (3) allowing the shaped mixture to harden to thereby form a solid calcium and/or magnesium containing feed.
10. The method for producing a solid calcium and/or magnesium containing feed as claimed in claim 9, wherein said silica and/or silicate is about 1.5 to 15 % by weight of the waste material and said silicate is sodium silicate.
II. The method for producing a solid calcium and/or magnesium containing feed as claimed in claim 9, wherein said waste material is blast furnace flue dust, sinter fines, caster mill scales, hot shrink mill scale, B.O.S. furnace flue fines, plate mill scale, burner fmes, limestone fmes, iron ore fines, iron ore dust, dolomite fines, fly ash. steel slags or other pozzulanic materials.
12. A solid paniculate feedstock for iron or steel making whenever produced by the method of claim 1 or 9.