What size is appropriate for the tower bottom?
Thread Content
I designed or purchased a packing distillation experiment setup with a tower diameter of 50 mm and a packing height of 2 m; the feed rate is around 5 l/h. The experimental system uses methanol and dimethyl carbonate, and the design pressure is 15 bar. I consulted several manufacturers, who recommended using a 5-liter reactor, but they also said that as the pressure increases, the volume of the reactor would change. They didn’t explain why or how this change occurs; I wasn’t able to figure it out. After searching for relevant information, I couldn’t find any calculation data specific to such small towers – there were only examples and standards for large industrial towers. Are there any standards that can be used for calculating small experimental towers? I would like to ask the experts on the forum for recommendations! Thank you!
It is sufficient to ensure a flow rate of 5 to 10 minutes; of course, this flow rate includes the flow rates from the reboiler and the bottom outlet of the tower. Your tower isn’t very tall; it is recommended that you use a tower with a diameter of DN100–200, as this will make construction easier and yield better test results. Because you are having difficulties with your small tower packing, and it cannot reach the packing density you designed.
It is probably mainly because: 1. The pressure is high, and the reactor bottom is too small to be processed easily. 2. A heating tube needs to be placed in the tower bottom; the tower bottom is too small to accommodate it.
To ensure gas sealing of the liquid in the tower, it is better to maintain a residence time of around 15 minutes
Under high pressure, the liquid volume generally increases, so the residence time is insufficient.
Based on laboratory experience, for a DN50 distillation column, a 5L reboiler is sufficient; for a 50-sized distillation column, both random packing and structured packing can be used as the packing material. To calculate the evaporation rate and the reflux volume, pressure data is needed for tower design. I’m not sure whether the diameter of the tower in question has been accurately determined; I wonder if a DN50 distillation column will meet your requirements. I suggest using design software such as ProII and Aspen to carry out the design, determine the tower diameter and the evaporation rate at the bottom of the tower. The evaporation rate can then be estimated by taking 10–20% of the amount of liquid filled in the bottom of the tower. Generally, the bottom of the tower is filled with liquid to about half to two-thirds of its capacity. It’s advisable that you conduct a proper design – just my suggestion!