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.
Highlights
Given the rapid and continuous development of China’s economy, the demand and utilization of hazardous chemicals have gradually increased, resulting in the production of approximately 40–60 million tons of hazardous waste (HW) every year [1]
The objective of this paper is to report on the industrial-scale results of the slagging behavior that occurred in the second half of the rotary kiln, exit flue of the secondary combustion chamber, and wall of the quench tower during actual production
The solid and semisolid hazardous wastes are directly sent to the rotary kiln through the feeder for incineration, and the liquid hazardous wastes are injected into the rotary kiln and secondary combustion chamber for incineration according to the difference in calorific value. hazardous wastes undergo high-temperature decomposition and combustion reactions in the rotary kiln, resulting in a great reduction in volume, and the burned residues flow continuously from the tail of the rotary kiln
Summary
Given the rapid and continuous development of China’s economy, the demand and utilization of hazardous chemicals have gradually increased, resulting in the production of approximately 40–60 million tons of hazardous waste (HW) every year [1]. Policies usually determine the method and scale of waste treatment [4], for example, the 3R (Reduce, Reuse and Recycle) principle. China’s disposal methods for HW include mainly safe landfills, curing stabilization, and thermochemical processes [5]. Thermochemical conversion technologies of waste play an important role, mainly including incineration (full oxidation combustion), gasification (partial oxidation), pyrolysis (absence of oxygen), and newly proposed plasma treatment technologies [6]. The waste can convert refuse-derived fuel (RDF) through thermic treatment technologies such as torrefaction, pyrolysis, gasification, plasma treatment, and liquefaction, etc., which has advantages of higher heating value, more homogeneous physical and chemical compositions, lower pollutant emissions, and excellent compatibility, etc., but will increase the cost of equipment and complexity of process [9]
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