In this study, two typical commercially used CaO-SiO₂-CaF₂-based mold fluxes with different basicities were adopted. Solid slag films of the two mold fluxes were obtained by immersing an improved water-cooled copper probe in the molten fluxes for different probe immersion times and molten slag temperatures. The film thickness, closed porosity, and roughness of the film surfaces in contact with the copper probe were measured. The heat flux through the solidified films and the comprehensive thermal conductivity of the films were both calculated. The results indicated that compared with the heat flux through high-basicity films, the heat flux through low-basicity films exhibited high fluctuation due to the evolution of fusion cracks within the glass layer. High-basicity mold fluxes resulted in higher thickness, growth velocity, surface roughness, and devitrification velocity of the films. With the growth and crystallization of the slag films, the comprehensive thermal conductivity of the high-basicity films increased significantly. For the low-basicity films, their comprehensive thermal conductivity first decreased and then increased after the solidification time exceeded 30 s. The comprehensive thermal conductivity of the high- and low-basicity films ranged from 0.63 to 0.91 and 0.62 to 0.81 W/(m·K), respectively. The results provide a novel method for analyzing the potential effect of the structural factors of slag films on heat transfer control and controlling the heat transfer behavior of slag films.

Elemental arsenic (As) is essential for diverse industrial applications. Most elemental As in China is produced by reducing gaseous arsenic trioxide (As₂O₃) with carbonaceous materials in steel reactors. This study aimed to extend the reactor lifespan through corrosion experiments and analysis. In this study, corroded regions of steel reactors were inspected after each production batch, and the corrosion process was examined. X-ray diffraction (XRD) was used to identify the major corrosion products, X-ray fluorescence (XRF) was used to measure the composition of corroded area, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to inspect the features and elemental distributions of the corroded steel-plate cross-sections. The results revealed that the steel wall near the charcoal zone exhibited the highest corrosion rate. Tin (Sn), selenium (Se), and antimony (Sb) did not promote the corrosion process, whereas carbon (C) accelerated it by forming an Fe–As–C system at the grain boundaries of the steel matrix, characterized by a low melting temperature. The important source of C responsible for initiating corrosion was solid-state C particles originating from reused materials from previous batches. Additionally, owing to the high processing temperature, oxygen (O) was transferred to the inner side of the steel wall before the dramatical corrosion of the matrix by elemental As and C. Results of this study provide references to increase the lifespan of steel reactors for elemental As production.