The operation of a distillation column requires mastering material balance, vapor-liquid balance, and heat balance.
Material balance refers to the principle that the amount of material entering the column per unit time should equal the sum of the amounts of material leaving the column. Material balance reflects the column's production capacity and is primarily regulated by the feed rate and the top and bottom discharge rates. During operation, changes in material balance are specifically reflected on the liquid level at the bottom of the column. When the column's operation deviates from the overall material balance, it can be reflected in changes in the column pressure differential. For example, if more material enters than exits, the column pressure differential will increase.
For a fixed distillation column, the column pressure differential should be within a certain range. If the pressure differential is too large, the rising vapor velocity within the column is too high, resulting in severe mist entrainment and even flooding, disrupting normal operation. If the pressure differential is too small, the rising vapor velocity within the column is too low, reducing the gas-liquid mass transfer effect on the trays and even causing leakage, significantly reducing tray efficiency. Poor material balance control can lead to chaotic operation of the entire column; mastering material balance is a crucial aspect of column operation. If the normal material balance is disrupted, it will affect the other two balances: the gas-liquid balance will not achieve the expected effect, and the thermal balance will also be disrupted and needs to be readjusted.
