Entrainment separation devices in raw sugar processing

Ebullition during boiling projects droplets of liquor or juice into the vapour space. In juice multi-evaporation the mass velocities of the vapour upflow are relatively constant in the different stages of the set. However the actual velocity increases as the absolute pressure (and hence the vapour density) decreases along the set. The Stokes terminal settling velocity of the entrained droplets does increase slightly along the set but the vapour velocity in the last effect is nearly an order of magnitude higher than that in the earlier stages and the tendency for the entrained droplets to be carried over in much more severe in the final vessel. If not collected and returned to process entrainment results in loss of sugar to waste, contamination of boiler feed condensates and a major water pollution problem due to sugar in water overflows.