CYCLIC DISTILLATION SYSTEM
Cyclic distillation process has following phase interaction mode - while the vapor passes through the column, the liquid doesn’t flow from tray to tray, and if the liquid flows over, it is not mixed on adjacent trays. In this case, the liquid flow (feed, reflux, distillate and bottom product) moves in a continuous mode. This method was named the controlled cyclic mode. Cyclic distillation operation consisting of two key parts: vapor flows goes through the distillation column and the stationary liquid stays on the trays (Fig. 1a), and this is called the vapor flow period, while the liquid flow period arises when vapor flow is stopped and the liquid holdup in sluice chambers (Fig. 1b), the vapor flow period starts and liquid from sluice chambers falls into the tray below (Fig. 1c).
➽ The time interval from the start till the finish of vapor supply is called the vapor period (VP) and the time interval from the start till the finish of liquid flow – liquid period (LP). The time of each liquid and vapor phase flow is, in total, the full time of cycle (TC):
TC=VP+TC (1)
➽ The design algorithm of a Maleta tray is as follows: the requirement as to the absence of liquid overflow on the trays during vapor supply is performed on hollow type trays while the vapor speed exceeds the column flooding. The requirement as to the absence of liquids mixing on adjacent trays during liquid overflow is ensured by means of a sluice chamber located under the tray. Cyclic distillation column works in the follow way: liquid flows (feed, reflux) are continuously supplied to the tray.
➽ During vapor supply, the liquid doesn’t overflow from tray to tray for the speed of vapor in the column exceeds the column flood speed. The controlling influence on liquid overflow from tray to tray is exercised by vapor, the cut in the supply of which for a couple of seconds allows the liquid to overflow from the tray bubbled cloth to the sluice chamber. Subsequent vapor supply opens the sluice chamber and the liquid flows to the empty tray below. Such sequence of actions takes place synchronically on all trays on the column’s height.
