Resource treatment of HPF coking desulphurisation waste solution: composition and characteristics of pyrolysis

HPF (H: hydroquinone; P: dinuclear cobalt-phthalocyanine sulfonate; F: ferrous sulphate) coking desulphurisation waste solution (CDWS) produced from coking oven gas desulphurisation process is an extremely harmful pollutant. The fundamental natures of this solution, which involves its main ingredient and content, type of organic matter, thermal decomposition characteristics of salt, and relationship of boiling point and density with salt content, were examined in this paper. Results show that inorganic salts in CDWS mainly contain ammonium thiosulfate and ammonium thiocyanate; the content and ratio of this two differ with factories and batches of CDWS. Organic matters in CDWS mainly contain phenolic and nitrogenous organic compounds, which together account for 98.79% of the total organic matter. The salts in CDWS are of poor thermal stability and can be decomposed at 425°C. The density and boiling point of CDWS increase with increasing salt content. Heating temperature should be strictly controlled, and solution flow should be supplemented by stirring at vacuum conditions during concentration and drying.