Formation mechanism of arsenic-containing dust in the flue gas cleaning process of flash copper pyrometallurgy: A quantitative identification of arsenic speciation

Abstract

The proper disposal of arsenic-containing smelting dust has been an important challenge in the copper pyrometallurgy industry which is mostly limited by the variability of arsenic content and species in different types of dusts. The eight types of flash smelting dusts produced along the gas line have been extensively characterized and comparatively studied. Arsenic content gradually increases along the flash smelting (FS) and flash converting (FC) parts of the gas line, and a negative correlation with the pH and copper content has been observed. PM10 accounts for 81.65% and 95.02% of the flash copper furnance (FSF) dust pocket dust and FSF electrostatic precipitator (ESP) dust, respectively. The size distribution variation inply the As enrichment in finer particles. The valence state of arsenic tends to migrate to reach higher valence states along both the FSF and FCF gas line, and the formation mechanism of different types of arsenic particles differs. The As(III)-O mainly remains in the WHB convection part dust and most of them are oxidized to arsenate compounds. More than 80% of the arsenic species was present in the ESP as As(V) and As(III)-arsenite. Fragmentation of concentrate particles and rapid condensation by gas phases lateral flushing of the pipe may produce arsenic particles in the waste heat boiler (WHB), while those remaining in the dust pocket and the ESP may result from adsorption, condensation, and chemical reactions. Temperature is the main factor that affects the deposition site of As2O3 particles. Alkali metal oxide particles influence As content and speciation in dusts by promoting the arsenate formation.