Journals →  Tsvetnye Metally →  2012 →  #7 →  Back

ALUMINIUM, ALUMINA, CARBON MATERIALS
ArticleName Improved efficiency of autoclaves digesting for processing of hard bauxites
ArticleAuthor Domanskiy I. V., Davydov I. V., Borovinskiy V. P., Malofeev M. N., Morozov A. A.
ArticleAuthorData

OJSC RUSAL All-Russian Aluminium-Magnesium Institute (RUSAL VAMI), Saint Petersburg, Russia:

I. V. Domanskiy, Senior Researcher
I. V. Davydov, Executive Officer of Engineering Department, e-mail: Ioan.Davydov@rusal.com
V. P. Borovinskiy, Leading Researcher
M. N. Malofeev, Researcher
A. A. Morozov, Engineer

Abstract

In the stat-of-the-art process, the flows of Bayer alumina technology production of the digestion process for hardly processed diaspore and diaspore-boehmite bauxites is conducted in the multi-shell autoclave testings under the temperature of 230÷270 оС. The minimization of the energy in this power intensive process is achieved by the variation of pressure, using step by step orificing of the heated slurry and utilization of the exit-juice steam, which is formed after evaporation under reduced pressure for heating of the initial slurry at the train input. As well known, the elementary orificing appliances are the openings, made at the ends of the cross-flow pipes. These pipes connect each autoclave of the train with the corresponding flash tank, or orifices, or nozzles with appropriate diameter. The methods of the correct design for different orificing appliances allow to avoid the slurry boiling directly in the cross-flow piping and excluding the contamination of the exit -juice steam by the drops of slurry. For design of the orifices diameters it should be known the flow rate for steam-liquid mixture, the hydrodynamics of the flow, considerably different from pure liquors. At the first stage of this study there was considered the flow of the gas-liquid system (water-air) from the tube with orifice. The experiment demonstrated that the empirical values of the flow rate are located between the values, which are provided by following methods: first considers the complete phase mixing and second considers the complete phase separation in the zone of the mixture outflow. In this paper there is suggested the incomplete phase separation when only part k of liquid phase is mixed with the gas. The formula for k calculation is suggested with benchmarking of trials and theoretical values.

keywords Alumina, digestion, bauxites, slurry, autoclave train, orifice, nozzle, rate, gas-liquid system, dispersion, evaporation, Bayer method, exit-juice steam
References

1. Layner A. I., Eremin N. I., Layner Yu. A., Pevzner I. Z. Proizvodstvo glinozema (Alumina production). Moscow : Metallurgiya, 1978. pp. 100–103.
2. Eremin N. I., Naumchik A. N., Kazakov V. G. Protsessy i apparaty glinozemnogo proizvodstva (Processes and apparatuses of alumina production). Moscow : Metallurgiya, 1980. p. 150.
3. Spravochnik metallurga po tsvetnym metallam. Proizvodstvo glinozema (Reference book of non-ferrous metals metallurgist. Alumina production). Moscow : Metallurgiya, 1970. pp. 194–196.
4. Samaryanova L. B., Layner A. I. Tekhnologicheskie raschety v proizvodstve glinozema (Technological accounts in alumina production). Moscow : Metallurgiya, 1988. pp. 127– 138.
5. Kogan V. B. Teoreticheskie osnovy tipovykh protsessov khimicheskoy tekhnologii (Theoretical basis of unit processes of chemical technology). Leningrad : Khimiya, 1977. p. 584.
6. Sokolov V. N., Domanskiy I. V. Gazozhidkostnye reaktory (Gas-liquid reactors). Leningrad : Mashinostroenie, 1976. p. 213.
7. Ostrovskiy G. M. Prikladnaya mekhanika neodnorodnykh sred (Applied mechanics of heterogeneous environment). St. Petersburg : Nauka, 2000. 359 p.
8. Uginchus A. A. Gidravlika i gidravlicheskie mashiny (Hydraulics and hydraulic machines). Kharkiv : Kharkiv State University Publ., 1970. 196 p.
9. Kiselev P. G. Gidravlika. Osnovy mekhaniki zhidkostey (Hydraulics. Fluid mechanics' basis). Moscow : Energiya, 1980. 174 p.
10. G. Wallis. Odnomernoe dvukhfaznoe techenie (One-dimensional two-phase flow). Moscow : Mir, 1972. 440 p.

Language of full-text russian
Full content Buy
Back