FLOTATION KINETICS AND SEPARATION SELECTIVITY OF COAL SIZE FRACTIONS

Transcription

1 Physicochem. Probl. Miner. Process. 49(2), 2013, Physicochemicl Problems of Minerl Processing ISSN (print) ISSN (online) Received April 16, 2012; reviewed; ccepted November 15, 2012 FLOTATION KINETICS AND SEPARATION SELECTIVITY OF COAL SIZE FRACTIONS Ynfeng LI, Wend ZHAO, Xihui GUI, Xiobo ZHANG School of Chemicl Engineering nd Technology, Chin University of Mining nd Technology, Xuzhou , Jingsu, Chin. E-Mil: Abstrct: Flottion recovery nd kinetics for three size frctions of col were investigted. Flottion of combustible mtter recovery ws pproximted with the first order kinetic eqution while flottion of the sh forming minerls with the second order eqution. Next, the equtions for ech size frction were combined nd formul ws obtined which ws used for pproximtion of the experimentl results using the so-clled Fuerstenu upgrding curve, which reltes the recovery of combustible mtter recovery nd recovery of sh forming minerls, both in concentrte. The Fuerstenu upgrding plot showed tht the best selectivity ws obtined for the middle size frction of mm, while the flottion selectivity of lrger mm nd smller mm prticles ws diminished. This finding grees with mny other investigtions. Keywords: col, flottion rte, combustible mtter recovery, sh, prticle size Introduction Chin is country in which col is the min energy source nd in very long period of time it will not chnge (Xu, 2003). The fine prticle minerl processing technology hs become one of the most importnt development directions in current field of minerl processing (Jmeson, 2010; Albijnic et l., 2010; Bhttchry nd Dey, 2008). Flottion is the most widely used nd effective method of seprtion of fine nd very fine mterils. The principle of flottion is bsed on different surfce properties of minerl mtter (Fn et l., 2010; Willim et l., 2010; Mugnd et l., 2011). Very importnt spect of flottion is its kinetics. The flottion rte is mesured s the recovery chnge of the floting mteril in the flottion product per unit time nd it is chrcterized by rte constnt nd kinetics order (Vpur et l., 2010; Gui et l., 2011, Brozek nd Mlynrczykowsk, 2013). It is known tht the col prticles of different sizes hve different flottion rtes. This hs been confirmed with industril dt (Song et l., 2001).

2 388 Y. Li, W. Zho, X. Gui, X. Zhng Most flottion rte tests show tht the fine col prticles cn be described by the first order kinetic model nd its rte constnt chnges with the incresing regents dose (Chelgni et l., 2010; Abkhoshk et l., 2010; Ucurum nd Byt, 2007; Akts et l., 2008; Brozek nd Mlynrczykowsk, 2007, 2013). The reltionship between flottion rte constnt nd flottion recovery with prticle size ws found to be nonliner (Abkhoshk et l., 2010). Prticle size hs lso gret effect on the ttchment/detchment of bubbles nd prticles (Irelnd nd Jmeson, 2012). It ws shown recently by Drzyml nd Luszczkiewicz (2011) s well s Bklrz nd Drzyml (2013) tht hving kinetics of flottion of the useful component of col or ore nd kinetics of the remining components in the feed, it is possible directly produce the Fuerstenu upgrding plot. This is so becuse the Fuerstenu upgrding plot reltes recovery of both components while the kinetic curves lso relte both recoveries through the time of the process. The im of this pper is to utilize this pproch for col by tking into ccount the kinetics of flottion of different size frctions present in ground col. Experimentl Anlysis of col smple Tble 1 provides the size composition of the col smple. As the size becomes smller, the sh content becomes greter. The sh content in the mm size frction ws 30.36%. It is more thn 5.60 percent points greter thn the verge sh content. The yield of dominnt mm size frction is 43.56%. Tble 1. Size nlysis dt of col smple Size frction, Oversize Undersize Yield,% Ash,% mm Yield,% Ash,% Yield,% Ash,% Totl From Tble 2, one cn see tht the dominting density frction of the investigted col is g/cm 3. Its yield is 37.93% with the sh content of 10.54%. The yield of the -1.5 g/cm 3 density frction is 57.03% with the sh content of 9.04%. Dt for other frctions re given in Tble 2. The dt show tht there is significnt mount of sh forming mtter in the col frctions.

3 Flottion kinetics nd seprtion selectivity of col size frctions 389 Density, g/cm 3 Yield,% sh,% Tble 2. Density nlysis of col smple Flot ccumultion Sediment ccumultion Yield,% sh Yield,% sh (Seprtion density±0.1) Density, g/cm 3 Yield,% Totl Experimentl procedure Col ws mixed with distilled wter nd stirred for 120 s. Next collector ws dded nd stirred for 60 s. The foming gent contct time ws 10 s, nd then flottion ws initited. The clen col collection intervls were 30, 30, 60, 60, nd 120 s. The totl flottion time ws 5 min. The obtined six flottion (clened col) products were lbeled s concentrtes J1, J2, J3, J4, J5 nd tilings T. The regents dosge nd other opertionl prmeters were: 320 g/mg of collector (kerosene), 110 g/mg of foming gent (2-octyl lcohol), flottion feed pulp mss concentrtion ws 90 g/dm 3, ir flow 0.37 m 3 /min, nd the stirring speed during flottion ws 1800 rpm. Results nd discussion The flottion kinetics of size frctions of the investigted col (Tble 3 nd Fig. 1) cn be expressed by the clssicl first order eqution: kt 1 (1 e ) (1) where ε is the combustible mtter recovery in concentrte, ε mximum combustible mtter recovery in concentrte, t flottion time nd k 1 is the first order kinetics constnt. The vlues of ε nd k 1 were determined with the Mtlb softwre nd they re presented in Tble 4.

4 390 Y. Li, W. Zho, X. Gui, X. Zhng Tble 3. Results of col size frctions flottion Products Combustible mtter recovery (%) Ash content (%) J J J J J T Totl Figure 1 shows chnges of the combustible mtter recovery with time. The dt were pproximted with the first order kinetic eqution (Eq. 1). It cn be seen from Fig. 1 nd Tble 4 tht the rte of flottion of the combustible mtter increses with the prticle size. This is so becuse the fine prticles exhibit low collision efficiencies due to their low mss nd inertil force while the corse prticles hve high degree of heterogeneity. The flottion rte of the mm, mm nd mm size frctions chnges from fst to slow. This grees with the results of other reserchers (Brożek nd Mlynrczykowsk, 2013; Jmeson, 2012; Polt et l., 1993; Gudin et l., 1931). Fig. 1. Reltionship between cumulted combustible mtter recovery for different size frctions of investigted col nd flottion time

5 Flottion kinetics nd seprtion selectivity of col size frctions 391 In the cse of the sh forming minerls flottion, the second order kinetic eqution ws used 2 kt 2 2 (2) 1 kt where ε is the sh mtter recovery in the concentrte, ε mximum sh mtter recovery in concentrte, t flottion time nd k 2 is the second order kinetics constnt. The vlues of ε nd k 2 were determined with the Mtlb softwre nd they re presented in Tble 4. Tble 4. Kinetics of flottion Kinetic eqution Size frction/mm or k 1 or k 2 Correltion coefficient First order (combustible) Second order (sh) Figure 2 shows the chnge of sh recovery to concentrte nd its pproximtion with the second order kinetic eqution presented in Eq. 2. It cn be seen from Fig. 2 nd Fig. 2. Reltionship between cumulted sh in concentrte for different size frctions nd flottion time

6 392 Y. Li, W. Zho, X. Gui, X. Zhng Tble 4 tht the rte of flottion of sh is different from tht of combustible mtter becuse the finest frction flots better tht the mm size frction nd worse thn the mm size frction. This cn prtly be explined by combined effect of collision nd ttchment/detchment sub-processes, dominnt for smll nd lrge sizes, respectively. The clened col mm prticles hs the most obvious chnge nd the highest cumulted sh content due to high content of ultrfine sh forming mtter. This grees with the results of other reserchers (Brozek nd Mlynrczykowsk, 2013; Rhmn et l., 2012; Vpur et l., 2010; Polt nd Chnder, 2000; Al Tweel et l., 1986). As presented recently by Drzyml nd Luszczkiewicz (2011) s well s Bklrz nd Drzyml (2013) the flottion kinetics, tht is reltions between recoveries nd time cn be combined providing the Fuerstenu upgrding curves (Drzyml nd Ahmed, 2005; Drzyml, 2006) relting recovery of the combustible mter nd recovery of sh in the concentrte. The Fuerstenu upgrding curves for the investigted size frctions re given in Fig. 3. The experimentl points were pproximted with the eqution k1 k ( ) 2 ( 1 e ) (3) resulting from Eqs 1 nd 2 fter removing time s the prmeter. The obtined equtions for ech size frction of the investigted col re given in Tble 5. Size frction/mm 1 kinetic eqution (1 e ) Tble 5. Upgrding equtions used for pproximtion of dt points of the Fuerstenu upgrding curve for ech size frction ε t ε t The derived ε ε kt 2 kt ε = 97.79, k 1 = 3.52 = 41.72, k 2 = ε = 96.04, k 1 = 2.47 = 38.20, k 2 = ε = 95.89, k 1 = 2.17 = 43.53, k 2 = 0.05 kt k1 k ( ) 2 ( 1 e ) Figure 3 indictes tht the selectivity of flottion is the best for the middle size frction while both smller nd lrger size frctions hve diminished selectivity. This observtion grees well with numerous flottion dt. For ech size frction, the recovery of combustible mtter in concentrte is greter thn the recovery of sh in concentrte.

7 Flottion kinetics nd seprtion selectivity of col size frctions 393 Fig. 3. The Fuerstenu upgrding curve showing flottion results for different size frctions of investigted col Conclusions According to the tests conducted for col nrrow size frctions, the flottion rte of the mm, mm nd mm size frctions chnges from fst to slow. As the flottion proceeds, the cumulted combustible mtter recovery grdully increses nd reches plteu level t bout 95%. The combustible mtter recovery in concentrte cn be pproximted with the first order kinetic eqution while the sh mtter recovery in the concentrte cn be pproximted with the second order kinetic eqution. Combintion of kinetic equtions for combustible nd sh mtter provides n k1 k ( ) 2 eqution ( ( 1 e ) which cn be used for pproximtion of the dt points for ech flottion size frction in the recovery-recovery Fuerstenu upgrding curve. The Fuerstenu upgrding curves show tht the best selectivity of seprtion occurs for the middle size frction of col. Acknowledgments This work ws finncilly supported by the New Century Excellent Tlents Support Pln from Ministry of Eduction of Chin (NCET ), the Ntionl Nturl Science Foundtion of Chin ( ) nd the Fundmentl Reserch Funds for the Centrl Universities (JH111793).

8 394 Y. Li, W. Zho, X. Gui, X. Zhng References ABKHOSHK E., KOR M., REZAI B., A study on the effect of prticle size on col flottion kinetics using fuzzy logic. Expert Systems with Applictions, 37(7): AKTAS Z., CILLIERS J.J., BANFORD A.W., Dynmic froth stbility: Prticle size, irflow rte nd conditioning time effects. Interntionl Journl of Minerl Processing, 87(1 2): AL TAWEEL, A.M., DELORY, B., WOZNICZEK, J., STEFANSKI, M., AN-DERSEN, N., HAMZA, H.A., Influence of the surfce chrcteristics of col on its flotbility. Colloids Surf. 18(1), ALBIJANIC B, OZDEMIR O., NGUYEN A.V., BRADSHAW D., A review of induction nd ttchment times of wetting thin films between ir bubbles nd prticles nd its relevnce in the seprtion of prticles by flottion. Advnces in colloid nd interfce science, 159 (1):1 21. BAKALARZ A., DRZYMALA. J., Interreltion of the Fuerstenu upgrding curves with kinetics of seprtion. Physicochemicl Problems of Minerl Processing, 49(2), BHATTACHARYA S., DEY S Evlution of frother performnce in col flottion: A criticl review of existing methodologies. Minerl Processing nd Extrctive Metllurgy Review, 29(4): BROZEK M., MLYNARCZYKOWSKA A., Anlysis of effect of prticle size on btch flottion of col, Physicochemicl Problems of Minerl Processing, 49(1): BROZEK M., MLYNARCZYKOWSKA A., Anlysis of kinetics models of btch flottion. Physicochemicl Problems of Minerl Processing, 41: BROZEK M., MLYNARCZYKOWSKA A., An Anlysis of Effect of Prticle Size on Btch Flottion of Col. Physicochem. Probl. Miner. Process. 49(1), 2013, CHELGANI S.C., SHAHBAZI B., REZAI B., Estimtion of froth flottion recovery nd collision probbility bsed on opertionl prmeters using n rtificil neurl network. Interntionl Journl of Minerl Metllurgy nd Mterils, 17(5): DRZYMALA J., LUSZCZKIEWICZ A., Zlety krzywej uzysk uzysk (Fuerstenu) do technologicznej nlizy i oceny wzbogcni surowców, Przegld Gorniczy, 2011, 7/8, DRZYMALA, J., Atls of upgrding curves used in seprtion nd minerl science nd technology. Physicochemicl Problems of Minerl Processing, 40: DRZYMALA, J., AHMED, H.A. M., Mthemticl equtions f or pproximtion of seprtion results using the Fuerstenu upgrding curves. Int. J. Miner. Process. 76, FAN M., TAO D., HONAKER R. ET AL., Nnobubble genertion nd its pplictions in froth flottion (prt 2):fundmentl study nd theoreticl nlysis. Mining Science nd Technology, 20(2): GAUDIN, A.M., GROH, J.O., HENDERSON, H.B., Effects of prticle size on flottion. Am. Inst. Min. Metll. Eng., Tech. Publ. 414, GUI X., LIU J., TAO X., WANG, Y., CAO Y., Studies on flottion rte of hrd-to-flot fine col. Journl of Chin Col Society, 36(11): (In Chinese) IRELAND P.M., JAMESON G.J., Drg force on sphericl prticle moving through fom: The role of wettbility. Interntionl journl of minerl processing, 102: JAMESON G. J., The Effect of Surfce Libertion nd Prticle Size on Flottion Rte Constnts. Minerls Engineering, (2012) JAMESON G.J., Advnces in Fine nd Corse Prticle Flottion. Cndin Metllurgicl Qurterly, 49(4):

9 Flottion kinetics nd seprtion selectivity of col size frctions 395 MUGANDA S., ZANIN M., GRANO S.R., Influence of prticle size nd contct ngle on the flottion of chlcopyrite in lbortory btch flottion cell.interntionl Journl of Minerl Processing, 98: POLAT M., CHANDER, S., First-Order Flottion Kinetics Models And Methods For Estimtion Of The True Distribution Of Flottion Rte Constnts. INT. J. MINER. PROCESS. 58, POLAT, M., ARNOLD, B., CHANDER, S., HOGG, R., ZHOU, R., Col flottion kinetics: Effect of prticle size nd specific grvity. In: Prekh, B.K., Groppo, J.G. Eds., Proc. nd Util. of High Sulfur Cols V, Elsevier, RAHMAN R. M., ATA S., JAMESON G.J., The effect of flottion vribles on the recovery of different prticle size frctions in the froth nd the pulp. Interntionl Journl of Minerl Processing (2012) SONG B., ZHI Y., ZENG D., The Investigte of Col flottion optiml prticle size. Col Processing nd Comprehensive Utiliztion, 1: (In Chinese) UCURUM M., BAYAT O., Effects of operting vribles on modified flottion prmeters in the minerl seprtion. Seprtion nd Purifiction Technology, 55(2): VAPUR H., BAYAT O., UÇURUM M., Col flottion optimiztion using modified flottion prmeters nd combustible recovery in Jmeson cell. Energy Conversion nd Mngement 51, VAPUR H.; BAYAT O., UCURUM M., Col flottion optimiztion using modified flottion prmeters nd combustible recovery in Jmeson cell. Energy Conversion nd Mngement, 51(10): WILLIAM J.O., ORHAN O., ANH V.N., Effect of mechnicl nd chemicl cly removls by hydrocyclone nd dispersnts on col flottion. Minerls Engineering, 23: XU Z Electro kinetic study of cly interctions with col in flottion. Interntionl Journl of Minerl Processing, 68:

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