Formation and Growth Behavior Analysis of Slagging Rings in Rotary Kiln-Type Hazardous Waste Incineration Systems

Abstract

Rotary kiln incineration technology has the advantages of strong material adaptability and a simple treatment process and has been widely used in hazardous waste treatment. However, the actual incineration process has caused problems such as ring formation in the treatment system due to the lack of research on the slagging mechanisms. In this paper, slagging phenomena occurring in the second half of the rotary kiln, the exit flue of the secondary combustion chamber, and the wall of the quench tower are analyzed and discussed in detail through characterization methods. The results indicate that the adhesion of low-melting alkali metal salts on the refractory surface in the second half of the rotary kiln is the key factor in forming the initial slagging layer. In the growth process of the slagging ring, the formed liquid phase can bond incineration residues of different sizes together and form a dense embryo body through liquid phase sintering. The deposition and solidification of molten/semi-molten fly ashes cause slagging formation in the exit flue of the secondary combustion chamber. The slagging phenomenon occurring in the inner wall of the quench tower belongs to the “crystalline-coalesce-hardening” process of the inorganic salts precipitating out of the high-salt wastewater.

Formation Mechanism of Deposits in Rotary Kiln during Steelmaking Dust Carbothermic Recycling

“…Some scholars have shown that deposits in the rotary kiln are characterized by large amounts of Na, Si, Cl, Ca, and Fe. Its molten phase is mainly formed by alkali metal salts with low melting points, such as sodium chloride (801 • C) [12,35]. Zhu et al [36] found that the main chemical compositions of the hazardous waste incineration residue were SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, and MgO.…”

“…Then, it is discharged from the end of the kiln into the cooling system [11]. This process has the advantages of low capital investment, strong adaptability, large production capacity, and flexible operation [12][13][14]. The iron oxides in the dust are reduced to metallic iron or low-valence iron oxide; at the same time, the zinc oxides are reduced to metallic zinc under high-temperature conditions in the rotary kiln using carbon as the fuel.…”