Characteristics for the hydration reaction of limestone washing process sludge from steel works

In order to understand the fundamental features of hydration reaction of sludge generated from a limestone washing process at a steel works and to improve its utilization as a secondary resource, the physicochemical properties of the sludge were examined and its hydration characteristics were investigated under several different conditions. The sludge was mainly composed of CaCO3 and its thermal behavior was observed to be affected by its composition. Compared to the conventional methods for hydrating limestone, using an ultrasonic vibration reactor produced more impalpable slacked lime powder with an even grain size because of the uniform reaction to the entire pulp without a violent reaction. Adequate pulp density for the production of fine slaked lime in an ultrasonic vibration reactor was observed to be 10 wt% or less. Hydration of the sludge formed by the limestone washing process was better and produced more homogeneous fine slacked lime powder than that of natural limestone. Slaked lime powder formed from the limestone washing-based sludge was very minute and the hydration reaction was completed within 10 minutes. In addition, the degree of hydration of the limestone washing-based sludge was found to be higher than that of natural limestone.