The stainless steel that has been cast into slabs, blooms or billets is then processed or hot rolled into much thinner and longer steel strips, so called coils, plates and long products such as rods. One of the significant environmental impacts of this process arises from the energy consumed.
Although not of the same magnitude as the energy required in the melting process, there is still a significant usage of fuel to re-heat the steel so that it can be hot rolled. Emission of combustion gases like NOx and CO2 and, depending on the fuel used, SOx is the most significant environmental aspect of the hot rolling process.
In order to minimise these impacts a number of different techniques are employed, including high efficiency burners, oxy-fuel combustion and modern furnace design techniques. Local considerations determine the choice of technology employed.
In Tornio exhaust gas containing carbon monoxide from the ferrochrome plant is recovered and used as a fuel in the Hot Rolling Mill. The result is improved air quality and major savings in fuel oil consumption. The energy provided by the carbon monoxide corresponds to 45,000-50,000 tonnes of oil per year. Combustion of the sulphur-free carbon monoxide is also important from an environmental point of view.
The hot rolling process also uses lubricants such as oils and greases. The cleaning of effluents in sand filters and treatments plants effectively removes these from the effluent discharges.