Effect of calcium on the vanadium extraction from high calcium type stone coal

Abstract

The high calcium type stone coal from Hubei province was leached by water and dilute acid separately after being roasted with different dosage of NaCl. The water leaching rate of vanadium (WLRV) was low and only 26.8% of vanadium can be leached by water when 4% NaCl was added, but the acid leaching rate of vanadium (ALRV) was relatively high. Calcium in the high calcium type stone coal is greatly superfluous relative to vanadium, hence, the calcium reacts with vanadium to form Ca(VO₃)₂, Ca₂V₂O₇ and Ca₃(VO₄)₂ orderly during the stone coal roasting process and high temperature is beneficial to the reactions between calcium and vanadium, which was validated by simulated reactions between pure calcium carbonate and vanadium pentoxide. These calcium vanadates are all water insoluble but acid soluble and this causes the low WLRV and relatively high ALRV. After calcium removal by HCl, the WLRV is highly enhanced and reaches about 50% when only 2% NaCl was added. If the HCl content is too high, the stone coal is easily sintered and the formed glass structure can enwrap vanadium, which leads the WLRV to decline. Single water leaching process is not appropriate to extract vanadium from high calcium type stone coal.

Keywords

stone coal / high calcium / calcium vanadate / leaching / roasting / calcium removal

References

[1] Bin Z Progress of the Research on Extraction of Vanadium Pentoxide from Stone Coal and Market of the V₂O₅[J]. Hunan Nonferrous Met., 2006, 22(1): 16-20.

[2] Han S, Zhang Y, Bao S, . Sodium Roast and Extraction of Vanadium from Low Grade Stone Coal with High Calcium from Hubei[J]. Metal Mine, 2012, 435: 83-86.

[3] Zhang Y, Bao S, Liu T, . The Technology of Extracting Vanadium from Stone Coal in China: History, Current Status and Future Prospects[J]. Hydrometallurgy, 2011, 109: 116-124.

[4] Zhu X, Zhang Y, Huang J, . A Kinetics Study of Multi-stage Counter-current Circulation Acid Leaching of Vanadium from Stone Coal[J]. Int. J. Miner. Process, 2012 1-6.

[5] Zhao Y, Zhang Y, Liu T, . Pre-concentration of Vanadium from Stone Coal by Gravity Separation[J]. Int. J. Miner. Process, 2013, 121: 1-5.

[6] Lin H, Fan B Study on Mechanism of Phase Transformation During Roasting and Extracting Vanadium from Fangshankou Bone Coal[J]. Chinese Journal of Rare Metals, 2001, 25(4): 273-277.

[7] Bie S, Wang Z, Li Q, . Review of Vanadium Extraction from Stone Coal by Roasting Technique with Sodium Chloride and Calcium Oxide[J]. Chinese Journal of Rare Metals, 2010, 34(2): 291-297.

[8] Greenwood N, Earnshaw A Chemistry of the Elements, 1997 2nd Edition Oxford: Butterworth-Heinemann

[9] Lide D R CRC Handbook of Chemistry and Physics. Internet Version 2007[M], 2007 Boca Raton, FL: Talylor and Francis

[10] Zou X, Peng Q, Ouyang Y, . Research on the Roasting Process with Calcium Compounds for Silica Based Vanadium Ore[J]. The Chinese Journal of Process Engineering, 2001, 1(2): 189-192.

[11] Kooli F, Jones W Characterization and Catalytic Properties of a Saponite Clay Modified by Acid Activation[J]. Clay Minerals, 1997, 32(4): 633-643.

[12] Xu H, Van Deventer JSJ The Geopolymerisation of Alumino-silicate Minerals[J]. Int. J. Miner. Process, 2000, 59(3): 247-266.