AU712106B2

AU712106B2 - Process for separating titanium and/or vanadium from pig iron

Info

Publication number: AU712106B2
Application number: AU36128/97A
Authority: AU
Inventors: Alfred Edlinger
Original assignee: Holderbank Financiere Glarus AG
Current assignee: Holcim Ltd
Priority date: 1996-07-24
Filing date: 1997-07-23
Publication date: 1999-10-28
Anticipated expiration: 2017-07-23
Also published as: WO1998004750A1; NZ329895A; AU3612897A; NO981310D0; CN1068058C; AR007955A1; CN1198190A; EP0874915B1; NO981310L; EP0874915A1; DE59704786D1; BR9702355A

Description

I

1 Process for Separating Titanium and/or Vanadium from Pig Iron The invention relates to a process for separating titanium and/or vanadium from pig iron.

When refining pig iron, a number of metals different from iron are oxidized with oxygen and slagged. As a rule, vanadiumcontaining basic steel slags having accordingly low vanadium contents are obtained. Considering the low vanadium contents, the recovery of vanadium from such slags involves considerable expenditure. According to an earlier proposal by applicant, such vanadium-containing steel slags were reduced in several steps by retaining a residual iron oxide content in the slag and separating metallic iron in a first reduction step. The remaining slag melt was further reduced to metallic chromium and/or vanadium or iron alloys thereof in a second reduction step having a higher reduction potential than the first reduction step, whereby a hydraulically active slag could then be separated.

In order to separate vanadium from pig iron, it has already been proposed to selectively oxidize and separate Si at first.

After this, a further step was suggested for separating P and S by the addition of MgO-containing charging substances, whereupon, in a subsequent third-step, alkali carbonates and iron oxide, ferrite or carbonates were introduced and a P- and S-containing slag was discharged. Subsequently, vanadium was oxidized while feeding oxygen, with a number of other metals naturally also being subjected to oxidation.

From JP-57-63647 A, a process has become known, by which i.a.

Na, P and V are to be recovered from slags. There, pig iron is introduced into a ladle and Si is separated. The metal bath is supplemented with soda (Na2CO3) and iron oxides and oxygen are fed so as to render feasible desulphurization and dephosphorization. The slag obtained is introduced into hot water and C02 is blown through into the aqueous phase in order r 2 to extract Na2CO3, Na3PO4 and NaV03. The desired products are precipitated from the aqueous phase. Vanadium in that case is precipitated as ammonium vanadate by aid of ammonium sulphate.

In Soviet Patents Abstract, Section M24, Week 9601, 26 January 1996, Derwent Publication Ltd., London, RU 2034031-Cl (URALS FERR METALS RES INST) (cf. official action), a process for recovering titanium-containing slags from titanium magnetite in blast furnaces has become known, in which iron-oxidecontaining slags are melted with titanium magnetite and discharged as mixed slags, with pig iron being formed. At the same time, the iron loss in the blast furnace slag is to be reduced.

The invention aims at providing a simple and selective process to be carried out in one step for each respective metal to be recovered and by which slags directly enriched with titanium and/or vanadium can be formed, from which the recovery of titanium and/or vanadium, respectively, has been substantially facilitated. Furthermore, the invention aims at providing a process of the initially defined kind, by which slags directly enriched with titanium and/or vanadium may be produced with little expenditure and without any modification of existing bottom-blowing converters. To solve this object, the process according to the invention essentially consists in that the pig iron in a first process step is supplemented with an amount of iron oxides sufficient for the slagging of titanium, that titanium is slagged and the slag is separated, if desired, and subsequently an amount of iron oxides sufficient for the slagging of vanadium is added and the slag formed and enriched with vanadium is separated, whereupon the pig iron is refined to steel. By admixing oxidic iron ores to the molten pig iron, mild refining and reduction of the iron from the iron ores is feasible, whereby titanium and, in the following, vanadium and silicon can be slagged quantitatively. The accordingly low slag amounts almost exclusively consist of titanium and/or vanadium oxides and silicon dioxide, wherein a 3 basic slag may be formed in case of an insufficient slag basicity by the addition of lime under the formation of calcium titanate and calcium vanadate, respectively, as well as calcium silicates. These basic slags highly enriched with titanium and/or vanadium subsequently may be aftertreated in a conventional manner by means of reduction steps, thereby enabling the recovery of metallic titanium, vanadium, ferrotitanium or ferrovanadium, respectively, in high purity and, in particular, free of carbon. The adjustment of the slag basicity and hence slagging in the form of calcium titanate and calcium vanadate, respectively, is feasible in a particularly simple manner in that Fe oxides and CaO are added in the first and second steps, each in stoichiometric quantities, for reacting the titanium and/or vanadium contained in the pig iron to CaTiO4 and CaV04, respectively, wherein additional lime is used as a function of the SiO2 content of the slag, lime advantageously being charged along with the iron ore for adjusting a slag basicity of With very low Ti contents in the pig iron, separate separation may be uneconomical. In such cases, the slagging of vanadium may be effected immediately, wherein low contents of titanium contained in this slag may be scorified at the same time. The use of amounts of iron oxide and/or lime respectively adapted to the Ti and V contents of the pig iron results in a selective one-step mode of operation by which the desired enrichment is obtained at once.

Since, as already mentioned, also silicon is slagged during the first, mild oxidation with raw ores and/or oxidic iron ores, the adjustment of the desired slag basicity, as a rule, is feasible by an additional lime charge only, wherein A1203 and/or SiO2 advantageously are added during the slagging of vanadium in order to adjust the desired viscosity of the slag.

The further refining process may be effected in a conventional manner, wherein it is advantageously proceeded such that; following the slagging of vanadium and the separation of the 4 slag, Mn, P and chromium are burnt off by refining and slagged in an additional process step. Due to the fractionated oxidation in a multi-step refining process, it has become feasible to separate a number of metals selectively from the pig iron, these subsequent slags containing hardly any silicon oxide on account of the silicon having been burnt off during preceding slagging. It may, thus, be reasonable and necessary to add A1203 and/or SiO2, also in this case, during the additional process steps in order to adjust the desired viscosity of the slag.

Following such an additional step, a steel works slag free of phosphorus and manganese may be formed upon separation of a slag containing said metals, which steel works slag, as a result, is suitable particularly for further processing and, in particular, as a starting product for the production of fertilizers [Thomas meal (Ca3(P04)2], hydraulic binders or hydraulic binder additives. Due to the step-wise refining, it is feasible to selectively slag titanium and/or vanadium in a first step, whereupon chromium, manganese and phosphorus may be slagged. The multi-step refining process, therefore, allows for the separation of the respective components that are undesired in the final slag while forming extremely slight slag amounts, wherein, above all, the advantage of recovering valuable substances, such as titanium and/or vanadium, may be realized in a substantially simpler manner than with the known processes.

Due to the relatively simple adjustability of the viscosity of the slag, the process may be carried out at relatively low temperatures closely above the liquidus temperature of the metal bath, wherein a large portion of the heat required for overheating the slag may be recuperated directly from the refining process. At the same time, iron oxide from the oxidic ores is additionally reacted to pig iron in the first step such that the iron balance of the process may be substantially improved.

I 5 The reaction of the final slags with a view to producing cement clinker and special binder grades having high U-belite contents and high final strengths may be effected in any desired manner. Thus, it is, for instance, possible to mix liquid slags from reduction processes and steel works processes with each other, it being feasible to conduct also this process in a largely autothermic way due to the exothermic neutralization reaction. A consecutive reduction procedure, for instance above an iron bath, may then be realized in one step in a simple manner, since the metals mentioned in the beginning have already been selectively slagged previously and were able to be discharged at relatively slight amounts of slag.

Vanadium-containing steel works slags typically contain 2 to 6 by weight V205. The enrichment of vanadium according to the invention at the beginning of the refining process results in a slag whose vanadium content may amount to more than 32 by weight. Taking into account the already effected separation of metals, such as titanium, vanadium and, later on, chromium or manganese, a subsequent reduction step for the purpose of aftertreating the steel works slag likewise may be carried out at reduced temperatures, which is beneficial in terms of energy.

In a particularly simple manner, pig iron already enriched with Ti and V may be used, the use of pig iron formed by the complete reduction of LD slags being preferred.

Slagging of titanium and vanadium while observing the conditions required for a quick and selective oxidation is feasible in a particularly safe and selective manner in a bottom-blowing converter.

6 The recovery and, in particular, the carbon-free recovery of vanadium from the slag formed advantageously is realized using Fe/Si or Al as reducing agents.

Exemplary embodiment: The following fundamental reactions *are applied for the slagging of V: Fe203 2V V203 2Fe V203 CaO -4 CaV204 3 kg vanadium are dissolved in 1 ton of pig iron. In order to introduce this vanadium into the slag, 4.71 kg iron ore are required. 4.41 kg V203 as well as 3.3 kg additional iron are formed.

In order to scorify 4.41 kg V203, 1.65 kg quick lime are required. Thus, 6 kg vanadium slag (CaV204) are formed per ton of pig iron. In order to keep this slag liquid, 20 A1203 are added. Thus, 7.6 kg vanadium final slag are formed per ton of pig iron.

If the extraction of such very low specific slag amounts from the converter involves difficulties, they may be raised by the addition of quick lime, bauxite and/or quartz sand, dry clay, ash-containing carbon carriers, etc. Yet, in that case the vanadium concentration will decrease accordingly.

The vanadium slag is composed as follows: Component Portion by weight) CaO 22 V203 58 (39) A1203 I.,r 7 This vanadium slag, which is highly liquid at 1380 0 C, is extremely well suited for reduction by aid of FeSi/Al in an induction crucible furnace (high-medium frequency).

7.6 kg vanadium slag are formed per ton of raw slag. Thus, in a 120 ton bottom-blowing converter 812 kg vanadium slag are formed per charge, with the auxiliary substances being nozzled in.

This vanadium slag is supplied to a slag collector in order to deposit entrained pig iron collect a sufficient slag volume for the vanadium reactor.

The slag reduction in the vanadium reactor advantageously is effected discontinuously above an FeSi/Al bath worked with argon. Thus, the vanadium portion of the ferrovanadium alloy is controlled via the quantitative ratios of Si and Al in the carbon-free iron bath.

The temperature of the iron bath ranges between 1500 and 1900 0 C, depending on the FeV alloy to be formed and on the final slag.

In the instant case, Al was supplied to the iron bath as a reductant.

209 kg Al must be fed to the iron bath per ton of vanadium slag. Hence result 390 kg vanadium, 393 kg A1203 being slagged.

Therefore, 813 kg final slag containing 27 CaO and 73 A1203 are formed from 1 ton of vanadium slag. This composition corresponds to a "refractory concrete" (castable) base material of the highest quality.

LIILi_-_X~ 8 If FeSi (Si) is used as a reducing agent, high-quality "alumina melt cement" may be obtained. The most diverse grades may be obtained as a function of the Al/Si ratio.

The FeV alloy contains V by about 50

Claims

1. A process for separating titanium and/or vanadium from pig iron, characterized in that the pig iron in a first process step is supplemented with an amount of iron oxides sufficient for the slagging of titanium, that titanium is slagged and the slag is separated, if desired, and subsequently an amount of iron oxides sufficient for the slagging of vanadium is added and the slag formed and enriched with vanadium is separated, whereupon the pig iron is refined to steel.

2. A process according to claim i, characterized in that Fe oxides and CaO are added in the first and second steps, each in stoichiometric quantities, for reacting the titanium and/or vanadium contained in the pig iron to CaTi04 and CaV04, respectively, wherein additional lime is used as a function of the Si02 content of the slag.

3. A process according to claim 1 or 2, characterized in that lime is charged along with the iron ore for adjusting a slag basicity of 1.3.

4. A process according to claim i, 2 or 3, characterized in that, following the slagging of vanadium and the separation of the slag, Mn, P and chromium are burnt off by refining and slagged in an additional process step.

A process according to any one of claims 1 to 4, characterized in that A1203 and/or Si02 are added during the slagging of vanadium for adjusting the slag viscosity desired.

6. A process according to any one of claims 1 to characterized in that the slagging of titanium and vanadium is effected in a bottom-blowing converter. 10

7. A process according to any one of claims 1 to 6, characterized in that pig iron formed by the reduction of LD slag is used.

8. A process according to any one of claims 1 to 7, characterized in that the vanadium-containing slag is reduced to a ferrovanadium alloy by aid of Fe/Si.or Al.