Conversion rules of sulfur compounds in iron chelate desulfurization system

Abstract

ABSTRACT Iron chelate desulfurization is a popular method in the coking industry due to its low generation of secondary salts. The conversion of sulfur compounds in the system plays a crucial role in this process. In this paper, the favorable conditions for the formation of polysulfide ions (Sx 2-) were investigated by ultraviolet-visible spectrophotometry (UV-Vis) in the reaction system of EDTA-Fe and Na2S. The reaction solution was analyzed by high-performance liquid chromatography (HPLC), aiming to obtain the main forms of the presence of Sx 2- after the reaction. HS− was first converted to Sx 2-, and then to elemental sulfur (S8). In the experimental range, the concentration of Sx 2- increased with increasing the concentration ratio of reactants (c(Na2S)/c(EDTA-Fe)) and decreasing the temperature, was maximal at pH 9.84. At c(Na2S)/c(EDTA-Fe) of 120, the forms of Sx 2- reached a maximum, which was S3 2--S10 2-. When the concentration ratio reached 130, S8 was generated, as the concentration ratio increased on this basis, the time for S8 to appear was shortened from 21 min to 12 min. Therefore, the study of the conversion rules of sulfur compounds in the iron chelate desulfurization system provides both the ideas to suppress the generation of by-salts in this system and new evidence to reveal the common problem of sulfur compounds conversion in the wet catalytic oxidation desulfurization process.