DISPOSAL OF WASTE-WATER FROM FLUE-GAS DESULFURIZATION (FGD)

Wet methods of FGD produce troublesome wastewater which contains large amounts of suspended solids. The hot flue gas stream which is passed through the absorber gives an effluent which contains dissolved sulphur compounds. This effluent is sent to a special reactor for pH adjustment by lime treatment, as well as for the precipitation of calcium sulphites and calcium sulphates. In this study special consideration was given to the following items: (1) sedimentation of particulate matter (suspended solids) produced during quasi-simulation of wet FGD and during pH adjustment of the sorption effluent by lime treatment, and (2) flow characteristics of sedimentation sludges. In terms of particulate separation, the efficiency of the sedimentation process was far above 70%. The best gravitational thickening effects and the most efficient release of the sludge were achieved in vertical settling tanks with deep funnels of 60-degrees bottom slope. Depending on the water content, sedimentation sludges behave either as a Newtonian fluid or a Bingham plastic. This behaviour should be taken into account when pipe transport is considered.