Research on slag modifying agents for CaO-Mg based hot metal desulphurisation

摘要

To improve the slag/iron separation problems in CaO-Mg based hot metal desulphurisation, experiments were carried out to generate a more fluid slag and to reduce the amount of hot iron entrapped within the desulphurising slag. The optimised slag modifying agent effectively decreased the melting temperature and viscosity of CaO-Mg based desulphurising slag. The optimised modifying agent has been successfully applied to industrial production. Industrial tests show that the average desulphurisation exceeded 82% when using the 80CaO-15Mg-5CaF₂ desulphurising agent at 3·5-4·0 kg t-1, and with an average final S of 0·005%. The skimming time decreased from nearly 12 min to ∼6·5 min. The heat loss during desulphurisation decreased to ∼19°C which is favourable to the subsequent steelmaking process. Average total Fe content in post-desulphurisation slag is 34% with 0·7-0·8 kg t-1 modifying agent, a decrease of ∼30% in iron loss compared with current status.