All kinds of trays can only be operated within a certain gas-liquid flow rate range to ensure the effective contact of the gas-liquid two-phase, so as to obtain a better mass transfer effect. The tray load performance graph can be used to indicate the gas-liquid flow range during normal operation of the tray. The gas-liquid flow limit indicated by the several side lines in the diagram shown by the tray designer is:
(1) Leakage line. When the gas flow rate is lower than this limit, a large amount of liquid leaks through the opening.
(2) Excessive mist entrainment line. When the gas flow is higher than this limit, the amount of mist entrainment exceeds the allowable value, which will significantly reduce the efficiency of the plate.
(3) Lower limit line of liquid flow. If the liquid flow is too small, the height of the liquid layer on the overflow weir will be insufficient, which will affect the uniform distribution of the liquid flow and reduce the efficiency of the plate.
(4) Upper limit of liquid flow. When the liquid flow rate is too large, the residence time of the liquid in the downcomer is too short, and the bubbles entrained in the liquid phase will not be separated in time, which will cause the gas phase back mixing and reduce the efficiency of the plate.
(5) Flood line. When the gas-liquid flow exceeds this line, it will cause the downcomer to flood, which will damage the normal operation of the tower.
If the normal operating range of the trays is large and the adaptability to gas-liquid load changes is good, the operating flexibility of these trays is said to be large. The operation flexibility of the valve tower and bubble tower is relatively large, and the sieve plate tower is slightly inferior. The plate efficiencies of the three types of towers introduced by the tray design manufacturers are roughly the same in the normal range.