Slide Background
Slide Background


Leoni, F. and Penco, C.

In order to comply with the regulations governing emission limits (SOx and particulate) the following possible solutions were analysed: to burn low sulphur fuel oil in the boilers and kilns and install new ESPs, or to build a desulphurisation plant, continuing to burn the cheaper high sulphur fuel oil. Eurallumina adopted the second choice based on project economics.

The BRDS technology selected by Eurallumina was developed and applied by Sumitomo Chemical Co. Ltd at its Niihama (Japan) refinery. Based on this technology, Hamon Research-Cottrell Italia S.p.A. was selected as turn-key contractor to design and build two desulphurisation units, one each in the boiler and calcination areas.

The BRDS process is a SOx/particulate scrubbing process based on contact between red mud and the flue gas to be treated. The neutralization reaction takes place in a multi-tray absorber using sodalite (DSP) as the reactive agent. SO2 gas reacts with sodium contained in the sodalite and is absorbed as sodium bisulphite and sodium sulphite. Sodium sulphite reacts to become sodium sulphate through oxidation.

Main elements of the desox unit are: the gas-gas heater where raw flue gas is cooled and clean flue gas is heated; the quencher to saturate and dedust the raw flue gas; the absorption tower for the desulphurisation process; the demister to remove red mud particles; and the red mud recycle tank where fresh and treated red mud are handled.

The two units have been in operation at Eurallumina from the beginning of the year 2000, showing low plant operating cost, easy plant operation and high stability for varying loads. The results in terms of SO2 and particulate emissions at the stack are significantly better than the design limits.