In the design of a distillation tower, the bottom of the tower needs to be sealed at night; so how is the liquid level for sealing calculated?

In order to keep the pressure inside acetylene generator 1 below a certain value (gauge pressure), a safety liquid seal (also known as a water seal) device must be installed outside the furnace. Its function is to allow gas to be discharged through tube 2 when the pressure inside the furnace exceeds the specified level. Determine the depth h below the water surface into the tank that the safety liquid seal tube of this furnace should be inserted to. Solution: When the pressure inside the furnace exceeds the specified value, the gas will be discharged through the liquid seal tube; therefore, the depth to which the liquid seal tube should be inserted below the water surface in the tank is first calculated based on the maximum allowable pressure inside the furnace. Draw an isopressure surface o-o' through the liquid seal port, and select points 1 and 2 on it. Where: p1 = pressure inside the furnace; or, since p1 = p2, it follows that h = 1.19 m. For safety reasons, the depth to which the tube is inserted below the water surface during actual installation should be slightly less than 1.09 m. For example, the water vapor generated during vacuum evaporation is usually sent to the mixed condenser shown in the figure accompanying this question, where it comes into direct contact with cold water and is condensed. To maintain the vacuum level during operation, the area above the condenser is connected to the vacuum pump, which periodically removes the non-condensable gases (air) from inside the device. At the same time, to prevent outside air from leaking in through the pressure tube 4 and thereby reducing the vacuum level inside the equipment, the pressure tube must be inserted into the liquid seal tank 5; water then rises to a certain height h inside the tube. This measure is known as a liquid seal. If the reading of the vacuum gauge is , determine the height h to which the water rises in the pressure tube. Solution: Let the absolute pressure above the water surface in the pressure tube be p, and let the pressure acting on the water surface in the liquid-sealing tank be the atmospheric pressure pa. According to the basic equation of hydrostatics, it follows that: Therefore, in this equation, =8.15 m

I’m not aware of the specific situation you’re referring to; in some distillation columns and reboilers, they are separate units. In such cases, the liquid return pipe from the distillation column to the reboiler (also known as the reflux pipe) needs to have a liquid seal, and this can be achieved by adding an S-shaped bend. It is mainly to prevent the vapor phase from the reboiler from going up through the liquid return pipe (also known as the reflux pipe). If the reboiler is integrated with the distillation tower, then the issue of liquid sealing is no longer a concern. Also, is the liquid seal mentioned by the poster the one that enables automatic drainage from the reboiler’s drain pipe? This liquid seal is quite complex and depends on the actual circumstances.

Sorry, I got the question wrong; it should be ‘In the experiment to determine the absorption mass transfer coefficient in a packed tower, how is the liquid level height calculated?’’

It can be calculated using Bernoulli’s equation, but in reality it is a rather complex process, as the variables involved can change. I think the U-tube serves merely to prevent the gas phase inside the tower from rising directly up to the reflux tank at the beginning of the reflux process. As long as the reflux tank is filled with liquid and there is a small liquid seal height, this will suffice to fulfill the function of the liquid seal; provided that there is a certain height difference between the reflux tank and the tower. The minimum required height difference can be calculated using the pressure at the outlet of the reflux pipe inside the tower (which is difficult to determine, as it is related to the resistance in the gas pipes at the top of the tower, and pipeline resistance is related to factors such as the gas velocity in those pipes) and the pressure in the reflux tank. Thus, the height of the U-tube corresponds to this minimum height difference between the reflux inlet inside the tower and the reflux tank. As long as the reflux tank is installed at a height higher than this minimum difference, there should be no problems. . .