D0I:10.13374/j.issn1001-053x.1989.06.024 第11卷第6期 北京科技大学学报 Vol.11 No.6 1989年11月 Journal of University of Science and Technology Beijing Nov.1989 On Niobium Reduction in Blast Furnace Dong Yicheng(董一战)，Yang Tianjun(扬天钓) Men Tao（孟涛)，Wang Zhenfeng(王振峰)* ABSRTACT:The Baotou Iron Ore of China contains very high niobium.This paper reported the results through laboratory and practical experiments on niobium enrichment in blast furnace.The effect of temperature,constituents of slag and silicon content in hot metal on niobium recoery was studied and the results had ceen verified by blast furnace operation.According to the reaserch,a comprehe- nsive extraction process that extraction combines with ore dressing and with pyro-- hydro-metallurgy should be adopted for Baotou niobium resource which is difficult to concentrating.The methods of increase in aiobium recovey were also suggested in this paper· KEY WORDS:niobium extraction,the blast furnace,resource chemistry,ext- ractive metallurgy The large Baotou iron niobium deposit in China,which contains Nb2Os 0.08 to 0.14 percent,is a pyrometasomatic deposit.Nb minerais associate with rion, grain size inlays finely and rare earth elements,phosphorous and fluorine content is very high,therefore,ore dressing and extraction are rather difficult.This paper studied practically and theoritically the reduction benefication of Baotou iron niobium ore in the blast furnace. 1 Experiments on Reduction Equilibrium of Niobium The experiments have been done at temperature of 1450°C±8°C and under conditions modifying the blast furnacc atmospherc,slag constituents and hot metal constituents.It was evidenced that equilibrium distribution rate of niobium between slag and metal can be up to 0.03 (Lx=(wt%in slag)/(wt%in metal)).The maximum recovery rate is more than 95%.This indicated that reduction process in blast furnace is more potential for niobium enrichment (See Fig.1) Manuscript Received November 8,1988 ··Dept.of Metallurgy 533
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2 Experiments Modifying Blast Furnace Conditions 2.1 Effect of Temperature on Niobium Recovery The experiments shows that temperature takes a much more important role in reducing niobium into metal.The increase of temperature,especially in the range of 1400C to 1500C,results in an increase of niobium recovery rate.The incre- ase rate slows down if the temperature over 1500C.(Sec Fig.2). 0.50 _(Nb) 0 100r 0.20 51M 2 80 0.30 6 60 ⊙ 0.10 0.10 20 N6) .0 80120240300360400480 1300 1400 1500 1600 Time min Temperature,C Fig.1 Equilibrium of Nb between Fig.2 Relation between Nb reco- metal and sythetic slag very rate with temperatures under Baotou Iron and Steel under blast furnace condi- Corp。conditions tions 2.2 Effect of Slag Constituents Experiments on the effecs of slag basicity,fluorine and rare earth element content on reduction of niobium oxide have been done under simulating metal-slag reaction conditions in blast furnace which smelts Baotou iron niobium ore. (1)An increase of slag basicity leads to increase niobium recovery The thermodynamic considerations and experiments verified that Nb oxide in the hearth is suboxide,so it is basic.The high slag basicity is good for increase activity of niobium oxide,besides,an incrcase of slag basicity makes its melting point high and increasc hearth temperature,therefore it also helps to reduce nio- bium (See Fig.3). (2)Fluorine constituent improves the fluidity of slag and kinetic conditions of niobium reduction.So it helps to increase niobium recovery (See Fig.4). (3)Rare earth constituents make the fluidity of slag worse so it decreases niobium recovery,the fluorite should be used to adjust the slag fluidity (Scc Fig.5). 534
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0 0.251 (F:15% 0.20 30 30.5 忠 26 0.10 0.05 20 0 0.40.60.81.01,2 15 Slag basicity.(CaO/SiO2) 1380 1430 Temperature,C Fig.3 Effect of slag basicity on Nb Fig.4 Effect of fluorine content equilibrium distribution ratio In slag on niobium reduction 45 45 20 15 1380 143: Temperature,'C Fig.5 Effect of rare earth content in slag on niobium reduction (RExOy:1-5%;2-15%) 2,3 Effects of Silicon Content in Hot Metal on Niobium Recovery Experiments show that at a certain temperature silicon content in hot metal has an increasing tendency at primary stage of slag-metal reaction,which implies that silicon services as a reducing agent for oxides of iron,manganese etc.du- ring this period,however,the silicon content in hot metal goes up again soon, meanwhile niobium content in the metal keeps at a certain level.Therefore the 535
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decrease of silicon content in the metal will result in an increase of quality of niobium iron and niobium recovery (See Fig.6). It can be seen from Fig-7 that more than 90%niobium recovery ratio may be obtained if silicon content in metal is kept above 0.3%. 1.5r 100r 1.3 0.25 96 9 (Nb) 1,1 0,20 % 0.9 (S) 10.15 2 0.7 0.10 0.5 0.0 78 40G0150270340450 00.20.40.60.81.0 Time,min S:in metul, Fig.6 Ci.anges of Si and Nb in hot Fig.7 Relation of Nb reccvery metal during slag-me'al rea- ratio with Si content in ction metal 3 Production Tests of Blast Furnace That blast furnace smelting medium grade iron niobium ore was analystically compared with that blast furnace smelting S-M slag.Niobium balance test aimed to check niobium behavior on a united smelting process from blast furnace to cle- ctric are furnace via LD furnace was been donc in Baotou Iron and Steel Corp. 3.1 Anolysis and Comparision of Blast Furnace Smelting S-M Slag with that Smelting Medium Grode Iron Niobium Ore Niobium enrichment in blast furnace which charges with S M slag solved the problem that niobium is recovered from Baotou resource first time but coke rale is more than 2500 kg per ton iron and niobium recovery rate is only about 40% thus,cconomical results of this technological process is not so good. In order to improve the economical results of niobium extraction,medium grade iron ore is directly smelted in blast furnace without dressing.Its effects are much more better than that of blast furnace smelling S-M slag.Even though niobium conteut in mid-grade ore is lower than in S-M slag,however,the c,ke rate of smelting with medium grade ore is less than 1500 kg per ton irou aad ni,bium recovery rate increases to more than 60%.Meanwhile rare earth can be conce- 536
洲尸 ， · 〕 〕 · · 多‘ 。 、 · 。 写 ’ 声 子一口‘ 谷咖冬 二︺‘﹄。热 ‘ 洲一扣‘中巨己 夕 门 〔 〕 ， ’ 。 月 、 刁夕 尹 ﹃一的诱村次三。冬 一 几 川 ， 一 士 · 矛 ’ 川 ‘ 认 ， ‘ 少 ， 一 入 · 。 、 ， ， 、 一 · 丫 一 卜 卜 一 一 、 、 一 ， 、 入 ， 、 一 。 一 一 。 一 一 。 ， ， ， 。。 犷 场 ， 一 一 、 · 、 一 ， 一 ‘。 、 一 一 一 一 入 、、 · 、 。 一 一 ， ，一 一 一 一 。 、 。 一 ‘ 一 一 人 ， 。 、 、 ， 。 、 。 、 。 一 、 、 一 一 。 。 、 、 、 、 ‘ ， 一、 ， 一 、 ，一 一泣 一 儿 。 、 。 乡石 · 、 洲
ntrated int)s'ag which ca1 be used as material t)prduce the low grade rare eart silicon iron.Tanle I gives the com parision of two processes. Table I Production index of smelting with S-M slag or with medium grade iron niobium ore Nb2O3 Coke ratio Recovery ratio 〔Nb) Productivity % t/t.Fe % % t/m3.d S-M slag 0.5 2.1~2.5 35~45 0.5~0.7 0.4~0.43 Med grad. 0.15 1.3~1.8 70 0.2~0.3 0.55~0.65 In order to find the optimum production index and niobium recovery in biast furnacc smelling medium grade ore of Baotou,a test operation was run in a 55m3 blast furnace to collect relevant data.The experiments show that the niobium recovery rate can reach up to 80%through this process,while the recovery rale of mineral dressing at that time is under 40%,the coke rate during test run was lower than 1000 kg per ton iron when blast furnace smelts medium grade orc. 3,2 Blast Furnace --LD Furnace--Electric Arc Furnace United Smelting Te:t Test shows that good economical and technolegical index can be obtained in the process which enriches niobium in blast furnace from Baotou cre.The test especially examined the effect of silicon content in metal on niobium recoery (See Table 2). Table 2 Index of the united smelting test Produc-Coke BlastH ot metal Slag [Si [Nb]Nb2O, Iron Indev livity rate temper。temper。temper, cost unit t/m3d t/ta C C C % % % RMB/t data 0.65 1.22 927 1347 1358 0.420.180.05 74.11 It is obvious that the increase of silicon in hot metal affects niobium content in hot metal.Comparision of two tests concludes that niobium oxide content in LD slag could increase nearly one time by decreasing silicon content in hot metal (See Table 3). Table 3 Effects of silicon content in metal on niobium oxide content in LD slag Hot metal Nb2Os content Heats 〔Si边 〔Mn [Nb) temperaturc in LD slag % % % C % run 1 1.73 0.81 0.246 1203 4.52 run 2 0.429 0.45 0.181 1347 8,86 537
入 士 且 七 往 士 ， 、 互 孔 之气 、 几 广 〕 几 ， ， 二 及 卫 王 弓 恤。 。 ‘ 〕 生 弓三生 弓 生。 卜 一 一 。 、 〔 〕 写 了 “ 一 一 人 · 。 。 。 。 。 。 。 。 。 。 。 。 。 、 工 以 、 全 住 爪 。 让 ， 飞 、、 · ， 二 一 丁 扭 乡百 ， 。 里、 盯 二 一 盯 皿 。 。 · 、 、 一 一 了 七 通 了 任 。 · 。 一 丁 。 七 一 又 “ ‘ 〔 〕 〔 〕 百 入 。 。 。 。 。 。 一 。 〔 〕 〔 〕 〔 〕 且 “ 。 乙吮月 上︻ 八 一 ︹ 。 。 。 。
It has been further proved by pra- 2,0 ctice that a low silicon content iron smelting conditions are needed in order to get a high niobium recovery when 1.5 blast furnace smelts containing niobium material.Therefore sufficient thermal 1.0 cnergy and evenly active conditions in 今 hearth and a suitable working slag 0.5 are essential.It is suggested that under Mgo in slag,% Baotou Iron and Steel Corp.'s conditi- ons more Mgo is needed to increase Fig.8 Effect of MgO content in slag three elements basicity.Lab experi- on si content in hot metal ments on effect of MgO content in slag on silicon content in hot metal was done (See Fig.8). 4 Conclusions (1)A comprehensive extraction process which ore dressing combines with cxtraction and with pyro-hydro-metallurgy should be adopted for full utilization of Baotou lean niobium ore.Blast furnace effectively enriches niobium into hot metal from lean niobium ore. (2)Small scale operational tests show that niobium recovery ratio in blast furnace can reach up to 80%,however,in practice it is only 60%to 70%when medium grade ore is smelted in it,the potential for further improvement exists, and when S-M slag is smelted its recovery ratio is only about 40%,thus there is more potential. (3)In addition to increasing niobium content in burden,a high temperature and evenly active conditions in hearth are more important for increasing niobium recovery in blast furnace,it is also meaningful to control silicon content in hot metal. REFERENCES 1 Ernest M Levin,Carl R Robbins.Phase Diagram for Ceramists,First Edition 1964,71;Supplement 1975;71 2 Chen Weiqing.J.of Beijing University of Iron and Steel Technology, 1985,(10):74 3 Shao Xianhua.Iron and Steel,1982;17(2):23 4 Han Qiyong,et al.Iron and Steel,1982;17(12):12 538
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