National Mineral Resources University (Mining University) (Russia):

Sizyakov V. М., Doctor of Engineering Sciences, Professor, Professor, kafmetall@mail.ru

Brichkin V. N., Doctor of Engineering Sciences, Head of Chair, kafmetall@mail.ru

Kurtenkov R. V., Postgraduate, kurtenkov@mail.ru

Problem areas in all-round processing of nepheline raw materials into alumina and co-products with nepheline slime utilization in portland cement production are considered. It is shown, that increasing nepheline raw materials processing depth with balancing of co-production of portland cement clinker may be achieved through improvement of initial raw material processing, increase in throughout recovery of alumina, as well as through nepheline slime conversion processing. A connection between belite conversion and total volume of nepheline slime to be processed to produce single-component portland cement raw mix has been established. This permits to achieve high processing results and change over to double-stream flow sheet, providing for production costs minimization. Relationships between soda conversion and its indices with respect to process duration, temperature and soda solution concentration have been established. With consideration of a high caustic solution concentration, a total conversion process stoichiometry with formation of sodium metasilicate, stable under the conditions in question, is substantiated. The causes decreasing soda conversion degree are shown, related to high indices of caustification of solutions and precipitation of double sodium and calcium carbonates. Proposals are expressed with regard to conversion degree increase through carbonation of produced caustic soda. Belite interaction mechanism is substantiated, including formation of solid products that cause increase in diffusional resistance to mass transport. A process of reacting substance surface mechanical activation is proposed. Principal process engineering solutions are considered for nepheline slime conversion processing and preparation of single-component raw mix.

The work was performed with the financial aid from the Ministry of Education and Science of the Russian Federation (government order, project No. 14.577.21.0127, dated 20 October 2014. UIPNI RFMEFI57714X0127).

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