Oxidation of Spray Dry Scrubber Residues in Wet Flue Gas Desulphurization Plants

摘要

A pilot-scale falling-film column was used to investigate the possibility of oxidizing spray dry scrubber byproducts (RP) to gypsum in wet FGD plants. The experimental results showed that the residual Ca(OH)_2 and CaCO_3 in the RP could be utilized for desulphurization resulting in a reduced limestone consumption and an increased removal rate of SO_2. At the condition of the presence or absence of Cl~- in the slurry of limestone and RP, the residual CaCO_3 in the gypsum slurry increased drastically with F~- concentration up to 100 mg/l. The result demonstrated that in RP oxidation of wet FGD, F~- reacted with Al~(3+) dissolved from the RP to form AlF_x in the liquid phase which was absorbed on the surface of limestone particles and extremely inhibited their dissolution even when the concentration of AlF_x was very low in the liquid phase. When pH value of the holding tank was controlled below 5, the residual CaCO_3 in the gypsum slurry was very low (about 2 % ). The particle size of gypsum crystal decreased as pH value and the concentrations of RP and Cl~- and F~- in the slurry of limestone and RP increased. During one of month continuous operation of the plant, the phenomena of product scaling and pipes plugging, which could be attributed to the presence of RP and F~- and Al~(3+) , have not been observed.