Diagnosis and Traceability Analysis of Slurry Foaming of Limestone-Gypsum Wet Flue-Gas Desulfurization (WFGD) System

Based on problem diagnosis and sample analysis of a typical case of wet flue-gas desulfurization (WFGD) slurry foaming, this study deeply explored and traced the slurry foaming origins. Above all, the main causation of this accident was the accident slurry discharged with the absorber slurry to cause chemical oxygen demand (COD) of the absorber slurry exceeded the tolerance. Secondly, the continuous accumulation of defoamers and other additives was also one of the important causes. These organic substances entered the absorber slurry, deteriorated the slurry quality and caused the slurry viscosity to increase and the surface tension to decrease. Besides, the organic substances in the absorber slurry may undergo some chemical reactions, such as saponification, to produce foam. Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) analysis of absorber slurry and overflow foam showed that the key organics to cause slurry foaming were 9-octadecane amide, cyclic polydimethylsiloxane, and N-cyclohexyl cyclohexylamine. This study provided an efficient problem diagnosis method and countermeasures including necessary efforts to slow down the accident before the problem clearly investigated and targeted measures according to analysis results.{Graphical Abstract}