Nizhniy Tagil Iron and Steel Works — “EVRAZ NTMK” JSC (Nizhniy Tagil, Russia):

A. V. Shestoperova, Head of the Central Laboratory, Coke and Chemical Shop
S. N. Kupriyanova, Leading Technologist, Coke-Coal laboratory, Coke and Chemical Shop, E-mail: Svetlana.Kupriyanova@evraz.com
V. N. Kruglov, Deputy Head of the Coke and Chemical Shop on Production and Sales

It is important to exclude the factors of coal charge preparation technology having negative effect on bulk density in the conditions of coking of multi-component coal mixtures with non-stable properties and quality parameters. At first coal concentrates were subjected to preliminary crushing before feeding in the silos of dosing area. To avoid excessive comminution, sintering components of coal charge were crushed in a hammer grinder without sieves and pockets, in the conditions of free falling; it provided crushing of large coal pieces. Prepared coal charge was directed to final crushing. Excessive comminution of sintering components led to charge self-depletion and, consequently, to reducing of coke strength parameters. Coarse classes of coal contain grains of rock and semiproduct which become the centers of local stresses during coking and promote crack forming in coke pieces as well as destruction of prepared coke under the effect of downing material volume and high temperature in the blast furnace. To reduce internal thermal stresses in coke pieces and to increase coke mechanical strength, it was required to raise the level of preliminary comminution of depleted components of coal charge, and to provide feed of sintering components in the dosing area without preliminary crushing. Variation of the preparation technology released the hammer grinder as a reserve for preliminary crushing of depleted components and reduced the load on final crushing.

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