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Dewatering of LimestoneSludge using a Centrifuge by Eisetsu OI1, Hiroshi KAMEGAYA1, Satoshi ARAI1 and Haruji KOBAYASHI1Limestone sludge dewatered by conventional rotary vacuum filters has a high moisture content. Limestone sludge of low moisture content could be used for the raw materials of cement. The dewatering by a centrifuge has been studied to reduce the moisture content to a lower level to facilitate the handling property of limestone sludge.Experiments were performed using a laboratory, vertical-axis centrifuge and 3.0 cm internal-diameter acrylic tube to minimize the vaporization of water from the surface of the dewatered cake. In this experiment, the effects of centrifugal force on the residual equilibrium moisture content of limestone. sludge were investigated for different bed heights of the cake.The plastic limit which is the moisture content of soil when the soil is allowed to vary from a semi-solid to plastic property was proposed to estimate the optimum, economical degree of dewatering. The measured value of the plastic limit of limestone sludge was 18.8%. The moisture contents dewatered by the centrifuge were compared with the value of the plastic limit in different centrifugal forces and bed heights.The moisture contents of limestone sludge dewatered at centrifugal forces of less than 2,000 G's were higher than the plastic limit. A solution of a surfactant(sodium dodecyl-benzene sulfonate) was added to limestone sludge to reduce the moisture content of dewatered cake. The experimental results showed that limestone sludge with a 300 ppm surfactant addition to limestone sludge was dewatered to as low as 18.8%(plastic limit of limestone sludge) at the centrifugal force of 900 G's.