【Weekly Topic】The relationship between rising gas velocity, flooding velocity, and empty tower velocity
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In a distillation column, the upward gas velocity has a direct impact on the mass transfer efficiency; the maximum allowable upward gas velocity must not exceed (answer A) A. the flooding velocity, B. the empty column velocity, C. half of the empty column velocity, D. half of the flooding velocity. Here’s the question: how do you determine the upward gas velocity in actual operation? Why must the upward gas velocity be lower than the flooding velocity? Must the minimum value be higher than the empty tower velocity? How are these defined? What is its guiding significance in practical operations? ? ? ?
The linear velocity in an empty tower is merely a value representing flow rate, and its upper limit is the velocity at which flooding occurs.
I’ll just watch without saying anything:shutup: Come in and learn*learn*:lol
I believe that the recovery rates from the top and bottom of the tower can achieve material balance with qualified quality, and at this point the upward gas velocity is appropriate. If the upward gas velocity is increased further, causing the pressure difference across the tower to keep rising, it becomes difficult to maintain the liquid level in the reflux tank and at the bottom of the tower; it seems that flooding is about to occur. At this point, the increased upward gas velocity prevents the reflux liquid from flowing downward properly; the liquid phase accumulates between the tray levels, and as a result the tower loses its separation capability.
The flooding velocity is calculated. Space velocity refers to the amount of feed that passes through a unit of catalyst per unit of time, and it reflects the processing capacity of the plant. There are two ways to express the air velocity: volume air velocity and mass air velocity. In practice, the gas flow velocity must not be higher than the flooding velocity; otherwise, the liquid phase on the tray will move upward together with the rising gas phase to the upper tray. It causes foam entrainment.