Challenges in power modulation

Abstract

Due to the increasing power prices and the increase in the spread between hourly power prices, various European smelters have started implementing power modulation, where amperage is increased during the usually cheaper night hours, while it is lowered during the day. The maximum leverage for power modulation can be achieved by a constant anode-to-cathode distance (ACD) approach. However, this solution has the biggest negative impact on the cell thermal behaviour. Therefore, it is important to evaluate the effects of extreme scenarios, ranging between a "constant ACD" approach and a "constant heat" approach. Typically, reduction cell operations are tuned to near constant amperage, while the cell voltage is being used to adjust the power input into the cells. No matter what modulation approach is chosen, traditional voltage-based control should be replaced by a purely energy-based control. This paper outlines some of the challenges that TRIMET Essen encountered in this process.