Experimental study on decay kinetics of residual chlorine in cooling water from coastal power plants

According to the practical chlorination technics of coastal power plants,the decline of residual chlorine concentration with time during 30 min in natural seawater was measured by DPD method at different chlorine dosages and temperature increments in laboratory.The results showed that there was an initial rapid chlorine decline(0~5 min) followed by a slower decay in seawater.The first-order kinetic model could describe the chlorine decay in seawater more precisely than the second-order kinetic model.Chlorine declined more slowly with rising chlorine dosage,but more rapidly with elevating seawater temperature.Chlorine was prone to decay rapidly in natural seawater due to its low apparent activation energy(Ea).As in the Yueqing Bay,the Ea in spring,summer,autumn and winter were 632.94,701.82,388.67 and 565.52 J/mol,respectively.Besides,the predicted equations of residual chlorine decaying in cooling seawater during 30 min at the chlorine dosage of 1.0~1.8 mg/L were obtained from the experiments in four seasons,and the relativities between predicted and measured values were very well based on linear correlation tests.