Research of efficiency of cleaning and dehydration of coal slims in centrifuges

Abstract

The efficiency of solid phase retention and dewatering of coal sludges from a coal preparation plant with a particle size of less than 3 mm was investigated using sedimentation centrifuges with a cylindrical-biconical rotor shape. It was established that the efficiency of solid phase removal from polydisperse sludge with a particle size of up to 3 mm reaches 85 –93%, while the moisture content of the dewatered product (sediment) ranges from 17–25% due to the displacement of moisture from the sediment pores during compaction. The sediment moisture content increases with the growth of the centrifuge's volumetric capacity, the degree of solid phase retention, and the proportion of particles smaller than 63 µm. It was revealed that the efficiency of solid phase retention in the coal fraction depends on the particle size distribution and the centrifuge's capacity. As the capacity of the sedimentation centrifuge decreases, the degree of solid phase retention increases due to the longer exposure time on solid particles. When dewatering polydisperse sludges, compression of fine fractions within the sediment occurs between larger particles. An increase in the content of 0.4–1.5 mm size fractions above 30% contributes to a reduction in sediment moisture under otherwise equal conditions. It was established that when dewatering fine-dispersed sludges with particle sizes below 63 µm, the sediment moisture content increases with the rise in solid phase retention efficiency due to the high moisture content of fine fractions. An increase in the proportion of fine fractions leads to a rise in moisture content up to 33%.