Boliden Aktiebolag

Johan E Wiklund

Karl-Axel Melkersson

Bo G Hedenas

Thore R Johansson

The invention relates to a method for separating gaseous elementary mercury from a gas in conjunction with a wet-gas cleaning process comprising a plurality of washing stages. The mercury-containing gas is treated with an aqueous washing liquid conducted in a closed circuit, the liquid containing 0.1-300 mmol/1 mercury (II) ions and at least twice this amount of ions having the ability of forming complexes with mercury (II) ions, the mercury in the gas being oxidized and absorbed in the washing liquid. The invention is characterized in that the treatment process is carried out in conjunction with a gas-cooling process effected after the last washing stage of the wet-gas cleaning process, to form a condensate for absorbing the halogens contained in the gas. The resultant condensate is transferred to the washing liquid and the mercury (II) content of the washing liquid is maintained by contacting the washing liquid with an oxidizing agent for mercury (I) ions. The agent used to oxidize mercury (I) ions is preferably chlorine gas.

Method for separating gaseous, elementary mercury from a gas

The invention comprises a method of wet-cleaning gases containing sulfur dioxide, halogens together with arsenic and/or arsenic compounds obtained in a pyrometallurgical treatment of sulfidic materials. The gases are washed in a diluted sulfuric acid circulating in a closed circuit, from which arsenic is recovered. The gases are then cooled to water condensation whereby the halogens are substantially completely taken up in said condensate and separated. The separated condensate is then discharged to a recipient after precipitation of residual arsenic and neutralization.

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Helsingborg, Sweden

Johan E Wiklund