Abstract
In recent years, the steel industry has accumulated approximately 100 million tons of dust annually, severely threatening the environment. Rotary kiln technology is one of the main industrial methods used to process this dust. However, some substances in flue gas congeal on the cooling wall of the gas duct and seriously affect production. In this study, the properties and formation mechanisms of the coagulum were investigated on the basis of experimental and thermodynamic analyses. The experimental results showed that the coagulum is mainly composed of chlorides (KCl, NaCl, and ZnCl2), oxides (ZnO, FeO), and carbon, with three structures: lumps, fibers, and particles. Based on a thermodynamic analysis, a reasonable explanation was proposed to clarify the formation mechanism. The liquid phase (a eutectic system of KCl–NaCl–ZnCl2), dendrites (KCl, NaCl), and particles (ZnO, FeO, C) were found to act as binders, stiffeners, and aggregates in the coagulum, respectively, constituting a composite structure. Liquids acting as binders are essential for coagulum formation, and dendrites and particles strengthen this effect. Furthermore, the eutectic system of chlorides plays a crucial role in coagulum formation. The results of the present study offer a theoretical understanding of gas-duct coagulation and will provide guidance for adopting alleviation measures.
Highlights
1.8 billion tons of crude steel were produced worldwide in 2020
The contents the main elements the feedstock, The contents of theofmain elements in theinfeedstock, the thecoagulum, coagulum,and and the crude zinc powder listed in Table the crude zinc powder areare listed in Table
Some of the oxides in the feedstock were reduced and chloridized to form metals and chlorides. These oxides volatilized into the flue gas at high temperatures
Summary
1.8 billion tons of crude steel were produced worldwide in 2020. This amount corresponded to more than 100 million tons of dust, accounting for approximately8%–12% of the crude steel output. 1.8 billion tons of crude steel were produced worldwide in 2020. This amount corresponded to more than 100 million tons of dust, accounting for approximately. Dust containing heavy metals and cyanide is classified as hazardous waste [1,2,3], and poses a threat to the environment. The use of this dust causes the accumulation of zinc and alkali metals in the blast furnace, shortening the service life of the blast furnace and leading to poor production [7]. Some researchers have proposed new methods based on two schemes: integral use and recycling metals
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