Effect of vanadium occurrence state on the choice of extracting vanadium technology from stone coal

Availableonlineatwww.sciencedirect.comScience DirectRARE METALSELSEVIERRARE METALS, Vol 27, No 2, Apr 2008, P 112Effect of vanadium occurrence state on the choice of extracting vanadiumtechnology from stone coalWANG Mingyu, XIANG Xiaoyan, ZHANG Liping, and XIAO LianshengSchool of Metallurgical Science and Engineering, Central South University, Changsha 410083, ChinaReceived 1 February 2007; received in revised form 20 March 2007; accepted 25 April 2007AbstractThe extraction technology of vanadium from stone coal by means of no-salt-roasting and dilute acid solution leaching treatment has the adBo. tages of low pollution, low investment, as well as high vanadium leaching effiwhich makes it the best technology for extendingplication. In the present study, the effects of vanadium occurrence state in stone coal, roasting temperature and additive agent on the leachng efficiency of vanadium were studied. The results indicate that the effect of vanadium occurrence state on the extracting vanadium technology is obvious. If the vanadium component in stone coal existed in amorphous phase form, this type of stone coal can be treated byno-slat-roasting and dilute acid solution leaching technology; while the vanadium-bearing crystalline phase existed in stone coal, the roastingadditive must be added to destroy this crystalline form so as to acquire high vanadium leaching rateKeywords: vanadium; extraction; roasting; acid leaching; stone coal1 Introductionand high cost, thereby the application of calcium salt roasting technology is limited [8-10]. Due to the simple flow, litVanadium is an important by-product that is used almost tle pollution and low production cost, the technology of exexclusively in ferrous and non-ferrous alloys. Vanadium tracting vanadium from stone coal by no-salt-roasting andconsumption in the iron and steel industry represents about dilute acid solution leaching becomes the best technology5%of the vanadium-bearing products produced worldwide for extending application [11][1]. China is rich in mineral resources of vanadium, 87% ofHowever. most of the aforementioned studies havewhich is vanadium-bearing stone coal, deposited mostly mainly been aimed at the effect of additives on vanadiumaround the southern provinces. The deoxidized condition leaching, and the effect of vanadium occurrence state inresults in the vanadium existing in stone coal only as v stone coal on roasting and extracting vanadium has rarelyand V, and the latter consists of more than 90% of total been reported. Due to the dispersed distribution of the stonecoal resource in various provinces and the small reserves ofThe traditional vanadium recovery technique from stone each stone coal resource, it is difficult to study the extractingoal is roasting with a source of sodium under oxidizing vanadium technology from stone coal one by one. To findconditions by flat kiln, and then vanadium in stone coal will the intrinsic affecting mechanism of roasting and extractingbe converted to soluble sodium salt [3-6]. The soluble vanadium, two different region stone coals were studied inamount of vanadium in the roasted material is leached out this study to provide a guiding for the choice of no-salt-with water, and then precipitated and separated from the so- roasting recovering vanadium technology from stone coallution as insoluble vanadium compounds. However, the re-leased exhaust gas containing Cl and HCl pollutes the en- 2. Experimentalvironment seriously that the sodium salt roasting technologyhas been prohibited by the government [7]. Though the ex-The samples I and 2 are taken respectively from thehaust gas pollution is avoided by roasting with calcium vanadium bearing stone coal of Songtao District in Guizhoucompounds, the leaching process of vanadium is complex Province and hi中国煤化工 ovince of ChinaCorresponding author: WANG Mingyu E-mail: wmydxxCNMHGWang M.Y. et al., Effect of vanadium occurrence state on the choice of extracting vanadium technology from stone coaland the chemical composition of stone coal was listed in of stone coals are basically the same and sio2 is the mainTable l. It is can be seen that the compositions of two kinds compositionTable 1 Composition of the stone coalwt%Sample VoS Mgo AlO3 Sio, K,o Nayo C Ba Sr Ca TFe C1.161.228.7763.913.570.3810.030.810.040.041.210.101.201.110,4444075910.640.0711.201470.030410.840.060.22Two types of stone coal samples were broken into pow- temperature, the leaching rate of sample 2 is far beyond thatder which was used to make the pellets of 8-10 mm in di- of sample Iameter with proper quantity of water. The pellets wereFig. 2 shows the XRD patterns of sample 1. It can bespread in a crucible and heated in an electric muffle furnace, seen clearly that there are three crystalline mineral phases,whose door was kept open to maintain an oxidizing envi- quartz(SiO2), muscovite(KAL(Si3)Oo(OH)2) and illiteronment. The pellets were stirred, as the furnace temperature (K(Al, V)2(Si, Al)4O10(OH)) in the raw stone coal and the il-raised every 50C. As soon as the temperature reached the lite phase is the only vanadium-bearing crystal mineraldesired value, the pellets were stirred every 20 min. The phase. After being roasted at 800oC, though the peak intenroasting efficiency of vanadium is expressed as followssity of XRD patterns of illite phase decreases, the illite phaseSoluble volarstill exists. The structure of illite mineral phase in stone coal7r100%Total volumeis steady, which can be destroyed only under the functionsDuring the leaching process of no-slat-roasting samplesof high temperature and additives [12]0.3%H2SO4 Solution(v/n was chosen as the leaching solu-tion; for salt roasting of stone coal, the leaching solution was100(awater. The contents of vanadium in stone coal samples andQuartz80000solution were analyzed by the ammonium ferrous sulfateIllite☆ Muscoviteoxidation deoxidization method. Stone coal samples were360000examined by XRD which was tested in the State Key labratory for Powder Metallurgy of Central South University400003. Results and discussionFig. I shows the relationship between the roasting tem-perature and the vanadium leaching rate. During the roasting(process no salt additive was added. It is obvious by comparison between the two curves that though the vanadium100b0leaching rates of two samples are in connection with roasting80000☆ Muscovite万4000020000Sample I0成Fig. 2. XRD patterns of stone coal sample 1: (a) raw stone coal(b) roasted stone coal at 800oC for 4 h.Temperature/℃Fig. 3 shows the XRD patterns of sample 2. It is obviousFig. 1. Relationship between vanadium leaching rate and by comparison中国煤化工 hat the mineralroasting temperature.phases existingTHCNMHGsamples114RARE METALS, oL. 27, No. 2, Apr 2008ferent; there is only quartz phase in the raw stone coal sam- phase( (K, Na)(SisAl)Og). Obviously, the addition of Naclple 2. After being roasted at 800C, the peak intensity of changes the original mineral phase distribution. After bearXRD patterns of quartz phase in sample 2 remains un- ing roasted with NaCl added, the illite phase disappears andchanged, which shows that the crystal lattice structure of a new mineral sanidine is formed. The decrease of the peakquartz mineral phase is undestroyed. It is indicated by com- intensity of quartz shows that Sio2 takes part in the reactionparison of vanadium leaching rates(Fig. 1)and the mineral during the roasting process, that is to say, some SiO2 is condistributions of samples I and 2( Figs. 2 and 3)that the ef- sumed during the decompose process of the mineral phasefect of vanadium occurrence state on extracting vanadium illite and muscovite. The reaction of vanadium-bearing minfrom stone coal is remarkable. If the vanadium component eral phase can be expressed asexisted in the amorphous phase form, the no-salt-roasting K(Al, V)2(Si, Al)4O10(OH2+NaCl+SiO2+02and dilute acid solution leaching technology can be used todeal with this type of stone coal, which provides a simple(K, Na)(Si3AlOs)+NaVO3+HCl+Cl3and quick method for estimating roasting mode by XRD1600001400/(a)e Quartz712000010000080000400000000ii,LiiiNacl content /wt%26/()Fig 4. Relationship between vanadium leaching rate and Naclcontent (roasted at 800C for 4 h)16000014000060000120000Quartz1000005000080000400006000030000400002000020000L人M10000Fig 3 XRD patterns of stone coal sample 2:(a)raw stone coal(b)roasted stone coal at 800C for 4 hFig. 4 shows the relationship between the content ofFig. 5. XRD patterns of sample 1 roasted at 800C and addedNacl and the vanadium leaching rate of sample I after beingroasted at 800C for 4 h. This figure shows clearly that withle increase of NaCl, the leaching rate of vanadium in4. ConclusionsThe XRD patterns of sample I roasted at 800oC for 4 hIt is proved from the above experiments that the effect ofwith 12 wt. NaCl added are shown in Fig. 5, which reveal vanadium occurrence state on the roasting and extractingthat there are two crystalline mineral phases in the stone coal vanadium technctone nnal ic obvious. If theroasted sample; one is quartz phase and the other is sanidine vanadium comp中国煤化工 the amorphousCNMHGWang M.Y. et al., Effect of vanadium occurrence state on the choice of extracting vanadium technology from stone coal115phase form, the treatment of this type of stone coal byanadium in stone coal of southern China. Rare Met. 1990.9no-slat-roasting and dilute acid solution leaching constitutes(2):110a very efficient method and more than 70% of vanadium [5] Xu G.Z., Chen B Z, Li J, Guo X.G., and Yi X P. Effect ofcan be extracted; on the contrary, when the vanadium bear-atmosphere composition on transform of vanadium in stoneing crystalline phase exists in the crystalline phase form, adcoal of southern China, Rare Met, 1991, 10(3): 198ditives must be added for extracting vanadium. The elemen[6] Liu A.H., Li L.S., and Yu L, Technology of vanadium extractary choice of recovering vanadium technology can be madetion from V bearing solid wastes and its prospect, Metal Mine( in Chinese,2003,(10):61by examining the mineral phase distribution in stone coal[7 Zou X.Y., Peng Q.J., Ouyang Y Z, and Tian R.G., Study onthe composite additives of roasting for bone coal vanadiumAcknowledgementsmine, Inorg. Chem. Ind (in Chinese), 2001, 33(3): 14[8 Zou X.Y., Peng Q.J., Ouyang Y Z, and Tian R.G., ResearchThis work was financiallyly supported by the Scienceon the roasting process with calcium compounds for silicaFoundation of Central South University(No. 76112037)andbased vanadium ore, Chin J. 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