In this cooperation project, a new oxygen enrichment technology was applied to the rotary kiln used by MIM Golesh Company to produce magnesite. This new technology improved considerably the kiln operation by increasing production capacity, decreasing the production cost and fuel consumption, as well as minimizing environmental pollution.
This paper gives the details of this technology improvement along with a description of its advantages as well as the gains in productivity, cost and environment aspects.

Formation of skulls is one of the main disadvantages of the processes, carried out in rotary kilns (productivity decrease, process chemistry violation).
Analysis of skull formation process reveals the main causes of their growth:
-chemical composition of charge mixture (containing slag-forming compounds – CaO, SiO2, FeO);
-kiln rotation speed;
-feed material quantity;
-temperature conditions;
-grain size composition of charge mixture.
Setting operating conditions of rotary kiln in accordance with charge material composition makes possible to avoid skull formation.
At the same time, it is necessary to make the skull-formation in the kiln as a means of the furnace refractory protection from chemical and thermal “corrosion”.
It is possible to solve the problem of the furnace operation without any skulls and refractory time facing more than 12 months by rotary kiln operating in variable silica ratio mode:
- Period 1, silicate unit (C/S) – 0.4 – 0.6 (skull is not formed). Duration is 2-4 days. Skull is removed if the furnace operation is more than 4 days;
- Period 2, silicate unit (C/S) – 1.4 – 1.6 (skull is formed). Duration is 1 day. Skull can be increased if the furnace operation is more than a day.
Provision of operation mode requires the variable silicate module:
- installation of the thermal imager, controlling the furnace body temperature, which allows to estimate the skull thickness;
- repeating the furnace operation with the silicate module 1.4 – 1.6.
Keywords: Waelz process, skull, silica ratio, charge, lining, temperature gradient.

PJSC Chelyabinsk Zinc Plant processes the dust of copper-smelting industry. Copper plant dust processing differs from EAF-dust processing by charge preparation. There is no need to separate tin from lead, so the finished product is lead concentrate.<br />The main detail of the technology is the introduction of two-stage Waelz process. Waelz process 1 for the whole separation of volatile (Zn, Pb, Sn) and non-volatile components (Fe, Cu). Waelz process 2 allows Waelz-oxide purification from harmful impurities (Cl, F, As) and separation of tin from the lead. The new technology has expanded resource base of non-ferrous and ferrous metallurgy and improved the environmental situation in the regions. <br />New technologies implementation allowed:<br />- to recover more than 100 000 t of non-ferrous and ferrous metallurgy wastes that were not processed before;<br />- to get more than 10 000 t of Zn, 4 000 t of Pb and tin in the form of lead and tin concentrates out of them and also excluding these metals form the raw material for ferrous metallurgy – Zn-containing slag and non-ferrous metallurgy – copper slag. <br />Decision of ecological issues:<br />- ferrous and non-ferrous metallurgy wastes included into recycling with land areas rescue and the possibility not to pollute ground water with heavy metals;<br />- emissions reducing during Waelz-process from 10 mg/nm3 (project data) to 0.4÷0,7mg/m3;<br />- greenhouse gases emission reducing (carbon dioxide) for 2 mln m3 a year thanks to the usage of the improved construction of waste-heat boiler and stream production for zinc production technology.

« Back To Technical Program