Ask for help: The difference between tower flushing and liquid flooding

Tower flushing is mist entrainment caused by excessive air speed in the tower. Liquid flooding occurs because a tower with a certain diameter has a limited cross-section for the free flow of gas and liquid phases. If the flow rate of one of the two phases increases to a certain limit, the liquid in the downcomer cannot flow down smoothly. ； When the liquid in the pipe reaches the top of the overflow weir of the upper plate, it will overflow to the upper plate, causing abnormal fluid accumulation, which will eventually lead to the space between the two plates being filled with foam liquid. Flooding.

For a tower with a certain liquid flood diameter, the cross-section for the free flow of gas and liquid phases is limited. If the flow rate of either of the two increases to a certain limit, the liquid in the downcomer cannot flow down smoothly. ； When the liquid in the pipe reaches the top of the overflow weir of the upper plate, it will overflow to the upper plate, causing abnormal fluid accumulation, which will eventually lead to the space between the two plates being filled with foam liquid. This phenomenon is called liquid flooding, also known as flooded tower. When flooding begins, the pressure drop across the tower rises sharply and the efficiency drops sharply. Operations at the tower were subsequently disrupted. There are two main factors that contribute to liquid flooding:: a. The liquid in the downcomer flows back to the upper plate. Since the tray has resistance to the rising air flow, the pressure above the lower plate is greater than the pressure above the upper plate. Only when the static pressure head equivalent to the height of the foam liquid in the downcomer can overcome this pressure difference can the liquid flow downward. When the liquid flow rate remains unchanged and the gas flow rate increases, the pressure difference between the lower plate and the upper plate also increases, and the liquid level in the downcomer rises. If the gas flow increases to the point that the liquid in the downcomer rises to the top of the weir, the liquid in the pipe will not only be unable to flow downward, but will begin to flow back to the upper plate, and liquid will begin to accumulate on the plate. ； During operation, liquid is continuously fed in from outside the tower, and eventually the entire tower will be filled with liquid. A flood is formed. If the gas flow rate is constant but the liquid flow rate increases, the resistance of the liquid passing through the downcomer increases, and the liquid layer on the plate thickens, which increases the pressure difference between the upper and lower plates, which will increase the liquid level in the downcomer, resulting in liquid flooding. b. Excessive liquid foam is entrained to the upper plate. Liquid foam entrained to the upper plate by the air flow can thicken the liquid layer on the plate. Under normal circumstances, the increase is not obvious. Under a certain liquid flow rate, if the gas flow rate increases to a certain level, the liquid layer will thicken significantly (the amount of liquid on the plate will increase, and the bubbles will increase and become larger). The liquid foam brought out by the air flow through the thickened liquid layer further increases. This excess liquid entrainment reduces the distance between the top of the foam layer and the bottom of the upper plate, and the liquid entrainment continues to increase. Large droplets are easily sprayed directly onto the upper plate, and the foam can also rise to the upper plate, until the entire tower is filled with liquid.