Paste Production and its Performance in Søderberg Smelters

The evolution of the capacity of Søderberg smelters and of the pot technology over the past two decades is addressed. Today’s figures of specific energy consumption and current efficiency are reviewed along with the paste performance in view of anode voltage drop, skimmed carbon and paste consumption. Bench mark performance figures are commented as a function of the technology using dry, semi-dry or wet carbon pastes.Laboratory testing of paste and baked artefacts is overviewed and the typical worldwide ranges of the key properties are given. The impact of the pitch and fines content on the intrinsic paste properties is quantified and the effects of raw materials are illustrated. The importance of the baked paste properties for the carbon consumption is explained. The peculiarities of dry aggregate preparation and paste production in the carbon plants are discussed with their impact on the paste quality and consistency.Modern Søderberg smelters with point feeders and hooded high amperage cells comply with severe emission limits and continue to be profitable. Modernization of the existing carbon plants is thus mandatory to keep up with the pot requirements.