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Journal of the Southern African Institute of Mining and Metallurgy

On-line version ISSN 2411-9717
Print version ISSN 0038-223X

J. S. Afr. Inst. Min. Metall. vol.110 n.5 Johannesburg May. 2010

 

TRANSACTION PAPERS

 

The plasma manufacturing of titania pigment and nano-titania in a pilot plant

 

 

J.T. NelI; J.L. HavengaI; J. SwanepoelII; H. BosmanII

IThe South African Nuclear Energy Corporation Ltd, Pretoria, South Africa
IIThermtron Plasma (Pty) Ltd, Pretoria, South Africa

 

 


SYNOPSIS

The establishment of a pilot plant for the continuous production of titania pigment and nano-titania is discussed. The plant was designed, constructed and operated on the Necsa site. The TiO2 production capacity is 7-10 kg.h-1 by the reaction of TiCl4 and O2 at >1000°C. Liquid TiCl4 is sprayed under pressure into a plasma reactor where it evaporates and reacts with O2 to form TiO2. Process optimization has allowed for continuous production without any clogging or blockages. The primary advantage of the plasmaassisted process is the possibility to recover and recycle the chlorine values in high yield as Cl2 for use in the manufacture of TiCl4. The HCl formed in most conventional fossil-fuelled processes makes Cl2 recovery and recycling much more difficult. Particle size distribution analysis of the fine, white product revealed a d50 = 125 nm. The raw product consisted of 60% rutile that could be increased to 80-100% rutile by post-annealing. The specific surface area (SSA) of the pigment was 8-20 m2·g-1(BET). According to the CIE colour index the 'whiteness' (L*>95) of the plasma-produced pigment was better than that of several commercially available pigments. The particle size could be manipulated by controlling the TiCl4 feed rate, gas flow rates, and the particle quench rate and residence time. Nano-sized TiO2 powders with a particles size (d50) as small as 50 nm were also successfully produced in this way.


 

 

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References

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3. BLAKEY, R.R. and HALL, J.E. Pigment Handbook. vol. 1, 1988.         [ Links ]

4. HSC Chemistry 5.1. Outokumpu Research Oy, Pori, Finland.         [ Links ]

5. CIE Recommendations on Uniform Colour Spaces, Colour Difference Equations, Psychometrics Colour Terms. Supplement number 2 of CIE Publ. No. 15 (E1-1.31) 1971. Bureau Central de la CIE, Paris, 1978.         [ Links ]

6. WON, D.J., WANG, C.H., JANG, H.K., and CHOI, D.J. Effects of thermally induced anatase-to-rutile phase transition in MOCVD-grown TiO2 films on structural and optical properties. Appl. Phys. A., vol. 73, no. 5, 2001. pp. 595-600.         [ Links ]

7. NEL, J.T. The development of plasma technology for the beneficiation and production of specialised minerals and materials. Innovation Fund Project No. 32450. Final Report, 97-98, 13 June 2006.         [ Links ]

 

 

Paper received Mar. 2009
Revised paper received Dec. 2009

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