Outotec roasting technology is characterized by lowest operating cost, minimum waste material, safe and simple 
operation at high availability and the production of useful side products as steam and sulfuric acid. Stringest environment regulations are met for solid, liquid and gaseous products or emissions.
The roasters are built with a grate size of 12 - 123 m². Depending on the raw material, the roaster operates with a capacity of 15 000 - 300 000 t/y (zinc) and respectively 55 000 – 260 000 t/y (pyrite).
The combustion air serves both as a carrier medium for the fluid bed and as a source of oxygen for the predominant reaction, which convert the metal sulfide to metal oxide and sulfur dioxide. The combustion air is provided by a high pressure air fan, which is controlled between the lower and a upper limit for a stable fluidisation of the bed. The reaction in the roaster is strongly exothermic, and the gas leaves the roaster with a temperature of approximately 800°C to 975°C and an SO2 concentration of approximately 10 % by volume, dry basis.
The hot dust-laden gas stream leaving the roaster is drawn into the waste heat boiler under suction from the SO2 blower. In the boiler, the dust-laden gases are cooled down from the roasting temperature to about 350°C before entering the dust precipitation system.
Outotec is able to deliver the whole off-gas treatment and energy recovery system after the roaster which includes following process steps:
For further information, please contact 
zinc(at)outotec.com
Brochure