How is the tower diameter calculated for batch distillation?
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Intermittent distillation is used very rarely; neither the batchsep nor the batchfrac modules offer functions similar to those for packing sizing or tray sizing. Yet, when working on projects, it is necessary to know the fluid dynamics data within the tower in order to select the appropriate type of packing and calculate the tower diameter. How do people handle such situations? Is continuous distillation used to estimate batch distillation? If so, how is it done? After all, the composition within a batch distillation column is constantly changing – how should this be taken into account? ?
Just use a continuous model to simulate it, that’s it
By using a continuous model to set the distillation rate equal to that in batch mode, what about the product purity? Will there be a big difference like this?
The tower diameter has basically no relation to the purity of your product; use the gas-liquid flow rate under maximum load in batch distillation to estimate the tower diameter for continuous distillation
For example, if there are three components a, b, and c, and the boiling point increases step by step, how should I determine the amount of evaporation for each step when the tower diameter is fixed? As you said, this is how I understand it: when distilling a, I use a continuous column to determine the gas and liquid flow rates inside the column; then, by comparing these flow rates, I simulate the process in a batch column to determine the vaporization rate at the top of the column, and from that, the distillation time can be calculated ； The same principle applies when steaming again at b. I’m not sure if I understand correctly
If possible, use a continuous mode instead of intermittent one; the results from continuous calculation will suffice. For those with experience, the tower diameter can be specified directly.
The F factor can be used to calculate the tower diameter; the gas volume under maximum operating conditions can be determined, the gas density can be calculated using a continuous column model, and by determining the F factor based on the type of packing, the tower diameter can be computed. The gas-liquid load inside the tower can also be calculated using Aspen’s batch distillation module, by selecting the condition under maximum operating load; the tower diameter is then determined using hydraulic simulation software.