Residence time distribution of solid particles in liquid fluidised bed separator

Residence time distribution (RTD) of coal particles in a floatex density separator (FDS) was investigated using stimulus response technique. The mean residence time of the underflow particles was observed to increase with a decrease in the particle size as well as density. The resistance to settling is enhanced at higher bed pressure and the residence time of the particles increases. A linear correlation of the mean residence time with the terminal settling velocity of the particles was observed. The mixing behaviour in the FDS was neither plug flow type nor fully mixed type. The n-tank in series model described the mixing pattern in the FDS well with 'n' values in the range of 3-5. The relatively low values of 'n' indicated that the flow behaviour in the FDS was closer to the well mixed state.