HIGH-EFFICIENCY SEPARATORS .1. EFFECT ON CEMENT

The development of high efficiency separators promised significant energy savings, increased production capacity and improved cement quality. However the results obtained in cement finish grinding mills were sometimes disappointing. Part 1 of this paper reviews the effects of high efficiency separators on cements; part 2 discusses the selection and operation of high efficiency seperators for optimum performance. High efficiency separators have two major effects on cements: a narrower particle size distribution and lower milling temperatures. The narrower particle size distribution will result in higher strength for a given specific surface, but will also increase the water demand in the cement paste. This effect is less significant in concrete. Lower milling temperatures provide benefits in cement production, but they also result in less dehydration of the gypsum, leaving the calcium sulfates in a less soluble form. Thus it may be necessary to adjust the dosage of the gypsum in order to ensure that there is sufficient SO3 in solution to control flash set or early stiffening of the cement. Optimizing the dosage and degree of dehydration. of the gypsum also mitigates the effects of the narrower particle size distribution on water demand.