Smelting practice of scrap addition in blast furnace and theoretical analysis of cost saving

The recycling of scrap has attracted more attention in recent years, and scrap can be used as iron-bearing material to smelt hot metal. The smelting practice of blast furnace (BF) with scrap addition in China was investigated, with the types of scrap being small pieces of scrap, such as crushed materials, light and thin materials, and small compacts which were easy to be added into BFs. The higher productivity of BFs with scrap addition was observed compared with that of BFs without scrap addition at the same volume, and the positive correlation between production increase rate and addition amount of scrap was found. The reducing agent rate of most BFs with scrap addition was lower than the average reducing agent rate at the same volume, while the gas utilization of BFs with scrap addition would not be reduced significantly. The theoretical analysis of cost saving was carried out as well, and the results indicated that the cost could be saved by scrap addition. The melting and carburizing were the two main processes of scrap in BF, in which three steps were involved in the melting process of scrap. The amount of carburization depended on the carbon content of hot metal in hearth and the original carbon content in scrap. The calculation showed that the coke rate could be reduced by 27 kg with 100 kg scrap addition per ton of hot metal, and the saving cost was decided by the amount of scrap and the actual situation of BF.