A successful combat against dioxins

Monitoring, dealing with and improving chimney emissions


That same critical and in-depth approach to problem situations and close consultation with the internal ArcelorMittal Gent environmental department have led to a drastic reduction in dioxin emissions from the sinter plant chimneys.


We initiated an intensive programme of measurements, analyses, trials, tests and comparisons against other equivalent factories. We built the necessary new installations and commissioned them. At a record pace, a poor situation was turned around into a benchmark for dioxin emissions from sinter plants.
Perpetuating the results achieved and further improving emissions is and will remain our constant concern and objective.



Dioxins

Inevitably dioxins are formed during a baking process in which oxygen, carbon, chlorine and organic hydrocarbons are present in the mixture.
“Dioxins” is a collective name for 17 polychlorided hydrocarbons, which can be harmful to human health. They come under very strict environmental legislation and an operating licence, and are expressed in Toxic Equivalents or TEQ.

 

An overall reduction of 97% has been attained in the emission concentration of PCDD/F in the flue gases. In rough terms that reduction can be broken down into three substantial stages. Firstly, adding burnt lime into the sinter mix resulted in an approximately 50% decline in PCDD/F emission concentrations. Secondly, selecting a series of process-integrated measures achieved an additional 35% reduction. Lastly, an extra 12% reduction was realised by building the active carbon injection installation.

The dust with the adhering dioxins is separated in the multi-centrifuge and in the filters and then reused as recycled dust in the raw materials mix. During the combustion process, they decompose and burn.

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