Current status of the technology for utilizing difficult-to-treat dust and sludge produced from the steel industry

Steel metallurgical dust and sludge is an important secondary resource, containing up to 20 valuable elements and compounds. It is the goal of various dust treatment processes to efficiently recover the valuable components in the dust and sludge while minimizing the environmental hazards of the dust and sludge. This paper summarizes the chemical composition, phase composition and particle size distribution characteristics of typical steel metallurgical dust and sludge. The chemical composition of secondary ash and the physical characteristics of rotary kiln tailings are analyzed, and the results show that the rare elements in the dust and rotary kiln tailings have high value recovery conditions. The reaction mechanism, process flow, domestic and foreign applications, advantages and disadvantages of conventional treatment methods such as pyrometallurgical process , wet process and physical process were discussed in depth. Conventional treatment processes often only target the separation and recovery of some elements with high content, and do not achieve the total resource utilization of dust and sludge. With the increasing shortage of resources and stricter environmental protection requirements , a single treatment process can no longer meet the requirements, and the technical solution of pyroenrichment–wet-separation–multi-process coupling extraction and complete recycling is proposed. Through the analysis of the reaction mechanism, the evolution and migration mechanism of valuable elements such as Zn and Sn in the pyroenrichment, wet separation and slag utilization systems are elucidated. It is proposed that the collaborative extraction technology of Rb, Cs, and other scattered elements should be developed in the future for the total utilization process to develop toward a more refined method. It is hoped that the above work can provide a reference for the harmless treatment and total resource utilization of difficult-to-treat dust and sludge in the steel industry. • Waste dust/sludge from the steel industry contains recoverable valuable elements. • The physicochemical properties of steel metallurgical dust and sludge and the treatment process are summarized. • A pyroenrichment–wet-separation–multi-process coupling extraction is proposed. • Technology for the recovery of precious and rare elements requires research. • The total utilization process is a crucial direction for dust and sludge management.