Investigation of eight target metals in solid residues of industrial waste gasification in a downdraft gasifier

Nowadays thermochemical conversion treatments represent a requirement for sustainable waste management. Therefore, investigations on concentration, distribution and leaching properties of metals in feedstock, char and cyclone dust samples collected from a downdraft industrial waste gasifier have been carried out in this study. Calorific value, ash amount and moisture of the industrial waste composition have been analyzed to define the thermal properties of the feedstock. Behavior of metals and their enrichment in char and cyclone dust during plant operation have been reported. An inductively coupled plasma optical emission spectrometer was used to determine heavy metal concentrations in the samples. X-ray florescence and X-ray powder diffraction were used to clarify the main inorganic phase content of the char and cyclone dust samples. Based on the reported data, operating conditions of the gasifier, feedstock composition and properties have direct influence on distribution and leaching properties of the metals. Cd, Zn and Cu containing forms distinctly favor enrichment on fine particles of cyclone dust, Ba, Ni compounds favor adsorption on char, and Cr is almost equally enriched in char and cyclone dust. According to the leaching data, gasifier solid residues (char and cyclone dust) must be sent to Class I landfill facilities. To prevent from further environmental risks, solid residues of gasification must be subjected to a proper immobilization process.