Beneficiation of Titanium Oxides From Ilmenite by Self-Reduction of Coal Bearing Pellets

Availableonlineatwww.sciencedirect.comBCIENCEDIRECT·JOURNAL OF IRON AND STEEL RESEARCH, INTERNATIONAL. 2006, 13(2): 06-09Beneficiation of Titanium Oxides From Ilmenite bySelf-Reduction of Coal Bearing PelletsXU Meng, GUO Ming-wei, ZHANG Jian-liang, WAN Tian-ji, KONG Ling-tan(School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China)Abstract: The study on the beneficiation of titanium oxides from Panzhihua ilmenites by reduction of coal bearingpellets was carried out. The iron oxides in pellets were efficiently reduced to metal iron, and titanium oxide slagbeneficiated was separated from metal iron. The effect of temperature, flux and coal blending ratio on the reduction and separation was investigated, and rational parameters were determined. a new process for the beneficiationof titanium oxides by rotary hearth furnace(RHF) was proposedKey words: ilmenite; pyrometallurgy; reduction; separation; titaniferous slag: coal bearing pelletTo produce 1 t pigment from ilmenite(contai- process for smelting titaniferous slag by rotary hearthning TiO, about 50%), about 8 t waste sulphuric furnace(RHF) will be proposed. This process feedsacid and 3 t FeSO..7H, O waste slag are produced. powder materials or pellets containing ilmeniteMany large-scale producers of pigment are facing the fines, coal fines and one or more than one flux. Atpressure of environmental protection and forced to high temperature, FeTiO3 in ilmenite is reduced byincrease the investment for treatment of these coal in RHF. The main factors affecting the reduc-wastestion and separation of composites have been studiedThe replacement of ilmenite by acid soluble ti- by present experiments, and rational process paramtaniferous slag of high grade and low impurity will eters have been determinedeliminate the reduction of iron fines and Feso residuals with reduction of concentration of titanium so-1 Experimental Equipment and Methodlution and increase acidolysis productivity. Thus,Experiments were carried out in an electric remuch attention has been paid to acid soluble titanif- sistance furnace heated by Si-Mo heating unit.erous slag abroad. The slow development of acid Green pellets composed of ilmenite fines, coal finessoluble titaniferous slag production in China may be and fluxes were put on the carbonaceous fines withexplained by two reasons. First, the acidolysis tech- size of 0-3 mm in a graphite box, as shown innology of acid soluble titaniferous slag is just under Fig. 1. The graphite box with pellets was heated todevelopment domestically. Second, the technology 1 450 C for 25-30 min, After being cooled, pelletsof smelting titaniferous slag in electric arc furnace is were crushed and iron shots were picked out bystill immature in chinahand. Tiny iron grains in slag were sorted out byAcid soluble titaniferous slag is mainly pro- magnet.duced on large sealed submerged arc furnace withThe composition of Panzhihua ilmenite in masselectrodes abroad, but in China, it is on open and percent(%)is TFe 31. 60, FeO 29. 25, TiO2 47. 76,small-submerged arc furnace with three electrodes. SiO2 1.45, Al2 O3 1.33, Cao 0. 68, MgO 5. 60The latter is featured by high power consumptionV2nO0.63,S0.22andP0.005.Thegh cost and severe environmental pollution. Based中国煤化工 nass percent(%)on Itmk3 technique developed by BUSTLI-A a new moilCNMH 2.4, fixed carbonBiography:XUMeng(1973-),Male,Doctor:E-mail:duoduo-xu886@sina.com:RevisedDate:November17,2004No. 2Beneficiation of Titanium Oxides From Ilmenite by Self-Reduction of Coal Bearing PelletsFrom Table 2, it is clear that when Na2 SO andLi2 CO, are used as fluxes, the separation is easierNaz CO3 deteriorates the separation. After coolingmost of iron was agglomerated into one or several ironshots in the size of 3-8 mm, gathered on the lowerpege of pellet punevenness of hearth layer material. After the pellets were crushed, these iron shots could be pickedout easily and the amount was defined as the yield ofiron. But some iron still remained in slag as tinyparticles and it was difficult to sort out. But in massproduction, iron can be separated from slag bycrushing and magnetic dressing. The morphology ofFig. 1 Green pellets in graphite boxreduced pellets is shown in Fig. 2.89. 1 and S 0. 12. All raw materials were crushed 2. 2 Effect of temperature on reduction and separationand milled to about 0. 154 mm. The effects of flu-The effect of temperature on yield of iron is shownxes, temperature and coal blending ratio on reduc- in Fig 3. At 1 500 C, while Na2 SO, and Li CO, aretion and separation of pellets were investigatedTable 1 Composition of fluxes in mass percent2 Experimental Results and analysisFlux No. Flux content Nai SO, Naz CO Liz CO32.1 Choice of fluxesTable 1 shows Na2 SO,, Na2 CO3 and Li, cO2.5contents in fluxes. The degree of separation of ironfrom slag after reduction of pellets at 1 450 Cshown in table 2Table 2 Degree of separation of iron from slagTotal slag mass/gFlux No. Flux content/% Mass of dry pellet/g Mass of iron shots]g Magnetic substance Non-magnetic substance242.6中国煤化工CNMHGJournal of Iron and Steel Research, InternationaVol. 13is generally believed that Li2 CO, behaves as a catalystthe reduction of ferriferous oxides. The melting point ofNa sO, and Li,COa as nuxesLi CO is 726C, so it may be thought)that the alkali metal infiltrates into carbon particles and reactswith carbon: Li, CO,(1)+C(s)=Li, O(1)+2co(g)Li, O()+co2 (g)=Li2 CO3(1), promoting the gasiNaSO, Na, COg andfication of carbon. At the same time, the addition ofLi, CO, as fluxesLi2 CO, also promotes the reaction of FeO-+Fe.However, at the experimental temperature, the gas-ification of carbon and the reduction of ferriferousoxides both go on very rapidly, and the catalysis is14501460147014801490150weakened greatly with highlighted fluxing action. InTTiO2-Li,O binary phase diagram:., TiO2 and Li,OFig 3 Effect of temperature on reduction and separationfirstly form congruent melting phase Li2O.3TiOwith congruent melting point at about 1 220c beused as fluxes, the yield of iron reaches 98%, and tween Li2O.3TiO and TiO2. It can be seen fromthe content of magnetic substance in slag is the the phase diagram that small quantity of Li2O playsleast, so the reduction rate is not the dominant fac- a fluxing action for TiO2 remarkably. And there isor for yield of iron. At high temperature, iron and an optimal value for Li2 O, beyond or below whichslag are melted quickly, and the viscosity of slagthe melting temperature of the binary mixture is in-are easier to aggregate and form iron shots. But, the experiment resule se are in good agreement with thelower, so the fluidity is higher, and iron droplets creased. All of thepartial replacement of Na2 SO, with Naz CO3 decreases the yield of iron.2. 4 Effect of coal blending ratio on reduction andparation of pelle2.3 Effect of Li, CO, content on reduction and sepaCoal in a pellet mainly plays two roles: one is therationreductant, and the other is the carburizing agent of ironThe displayed results in Fig. 4 are obtained at that decreases the melting point of iron alloy. But too1 450 C with total content of Na? SO and Li, CO, of much carbon particles in the pellet will retard the aggre-10%. It is shown that small quantity of Li CO, can gation of iron and slag, especially iron. Accordinglyincrease the yield of iron and decrease magnetic sub- they will make the separation of iron and slag morestance in slag. When the amount of Li2 CO3 is 2%difficult. This has been proved by the results shown3%, the yield of iron is the highest. Beyond 3%, in Fig. 5. When the coal blending ratio is 8%,thethe yield of iron is decreased, and correspondingly yield of iron is the highest. When it is beyond 12%the content of magnetic substance in slag is higher. It the yield of iron decreases dramatically because the tiny50(a)中国煤化工Li, CO, content in one pellet%CNMHGFig 4 Effect of Li2 CO, content on reduction and separationig. 5 Effect of coal blending ratio on yield of ironNo. 2Beneficiation of Titanium Oxides From Ilmenite by Self-Reduction of Coal Bearing Pelletsiron particles are remained in slag and it is difficult iron nuggets similar to pig iron in com positionpickoutAs long as the furnace temperature can be raised to 1 450 C or higher, Rhf will2.5 Beneficiation rate of titanium oxides and compo- be able to meet the technical requirements of smelnents of slag phaseting the titaniferous slag.The beneficiation rate of titanium oxides is 70%76% obtained by chemical analysis, which is in good 4 Summaryagreement with theoretical estimation. The X-raydiffraction of the slag phase is shown in Fig. 6. B,(1) The optimal parameters of reduction andcontrast, the titaniferous slag is composed of the separation of coal bearing ilmenite pellets aresolid solution phase of M,O, type (pseudobrookite, adding Li? CO, of 2%-3% and Na? SO, of 7%-8%M=Ti, Fe, Mg, Al, Mn, Li and so on) and small as fluxes, coal blending ratio 8%-12% and temper-amount of silicate phase. In accordance with the ature 1 450 C or higher. The beneficiation rate ofRef[7], when iron and titanium are extracted from titanium oxide slag can be up to 70%-76%all kinds of titaniferous and ferriferous oxide ores by of iron irom slag. Especially, adding Li, CO on(2) The fluxes play critical role for separationreduction, the main phase of slag is usually anosvite[m(M2+0. 2Ti02).n(M+O,. TiO,), which is 2%-3% can decrease the separation temperaturesimplified as M,O type, enriched with TiO, and is easi- by about 100 C.ly dissolved in acid. While in existence of excess carbon(3) The main phase of beneficiation slag is thethe following reaction occurred between Feo. 2TiO solid solution phase of M3 O, type called as anosvite.and carbon in titaniferous metallized pellet:Refex(FeO·2TO2)+5(x-2)C=2(Fe-x·Ti2O3)+3(x-2)Fe+5(x-2)CO(2≤x≤3)[1] Osamu Tsuge, Shoichi Kikuchi, Koji Tokuda, et al.Successful3 Propose of Developing RHF Smelting TitanIron Nuggets Production at Itmk3 Pilot Plant [A].2002 Ironmaking Conference Proceedings [C]. USA: Iron and Steel So-iferous Slag Processciety,2002.511-519[2] Larry Lehtinen, Steven D Rutherford. The Mesabi NuggetRHF has been successfully applied to production ofProject--New Iron Making Technology of the Future [A]direct reduction iron domestically and abroad. MoreoSSTech 2003 Conference Proceedings [C]. USA: Iron andver, Itmk3 process has passed the pilot experimenteel Society,2003.1043-1048.in Japan and America, which produces pebble iron or[3] Meissner S, Kobayashi 1, Tanigaki Y, et al. Reduction andMelting Model of Carbon Composite Ore Pellets [J]. ISIJInt2003,30[4] Yoshitaka SA WA, Tetsuya YAMAMOTO, Kanji TAKEDAet al. New Coal-Based Process to Produce High Quality DRIM,O,for the EAF [] ISU Int, 2001, 41(Supplement), SI7-S21[5] GUO Xing-min, TANG Hong-fu, ZHANG Bi-sheng, et al400MO3Study on the Catalysis Mechanism of Liz CO, for Reduction ofIron Ore Pellet With Carbon [J]. Acta Metallurgica Sinica2000M,2000,36(6);638-641( in Chinese)[67 Ernest M Levin, Carl R Robbins, Howard F McMurdie, PhaseDiagrams for Ceramists [M]. Ohio: The American Ceramic So-ciety, 1964.[7] CUI Shu-xian, LI Ji-zhong. Effect of the Constituents of the26/(°)Electric Are Furnace Slags Containing Titania on Their Acid.Fig6 X-ray diffraction pattern of titaniferous slag phase57-63(in Chinese)中国煤化工CNMHG