The technology includes pre-drying of the entire ore mass with a reduction in humidity from 30-35% to 18-20%, roasting of the ore/metallic mixture – mixture of ore with reducing agent (AC, ASH), as well as with dust that returns after trapping in the electrostatic precipitators.
The roasting is carried out in tubular rotary kilns which are 4.5m in diameter and 70m in length. When working with coal-fired fuel, multi-fuel burners are used for heating and operation. The maximum operating power of one burner is 41.8MW, and the minimum operating power is 30.3MW. The consumption of coal dust can reach 6000 kg/h, the maximum consumption of natural gas is 4466 m3/h and consumption of endothermic gas (ore thermal) does not exceed 5000 m3/h. The exhaust gas temperature at the loading end of the furnace is 350-480°C.
The obtained hot-cork with a temperature of 800-900°C is loaded using special devices for the recovery of melting on rough ferronickel in 40MW electric melting furnaces with six self-sintering electrodes which are 1200mm in diameter.
In the process of ore recovery melting, there is a 7,000-11,000 m3/h yield of gases. This yield is comprised of approximately 65% carbon monoxide, which after cleaning from dust goes into combustion in a tubular rotary kiln, thereby reducing the consumption of coal dust by 10-15%.
The furnace loading and melting in the furnace is a constant process. The releases from the furnaces of ferronickel slag melts are periodic (scheduled), maintaining constant levels of ferronickel and slag melts. The working temperature of the slag is determined by its composition and is permissible up to 1620°C.
The temperature of the rough metal at the outlet of the RTP is 1350-14600C. Rough ferronickel: 14-20% Ni; 3.5-5.5% Si; 1.8-2.5%; S is no more than 0.4; 1.0-2.0% Cr; P is no more than 0, 18%, Cu is no more than 0,07%, the rest: iron, is extra-desulfurized with soda ash.
The final cleaning of impurities upon the receipt of finished ferronickel is carried out in 50 ton vertical converters with top oxygen supply (oxygen of own production) by means of a dual process (sequentially in two converters).
The process for smelting finished ferronickel in converters is accompanied by gas emissions of up to 140,000 m3/h. To clean from the exhaust gases dust in the converter compartment, there are dust-gas trapping devices in the wet, two-stage cleaning. The degree of purification is 96.0%.
The finished ferronickel has a nickel content of about 15-20%, impurities of less than 0.5%, and is cast into 35kg ingots or is granulated.