Seeking advice on the selection of height and heat load for a batch distillation column
Thread Content
I have previously calculated for continuous distillation columns; I have no experience with batch distillation columns. How should the column height and heat load for a batch column be determined? For example, the design for recycling 2t of NMP solvent with 10% moisture content. I have previous experience in factories with other systems; when cutting off the water flow, the process is relatively slow, and once the water flow is stopped, the flow rate at the top of the tower increases by 5-6 times. For a 10-cubic-meter tank, the flow rate at the time of water removal is up to 0.5 t/h; after the water has been removed, if no heating steam is applied, the flow rate remains at 2.5 t/h ； The heat load is related to the operation time; a higher heat load results in increased gas and liquid flow rates, which in turn leads to a larger tower diameter ； So how do you make a choice? The height of a continuous column is generally determined by the reflux ratio and the number of trays, while what about the height of an intermittent column? I also would like to ask those experienced seniors: in the overfeeding stage, should the reflux ratio be increased to reduce the overfeed fraction?
There are exactly two key technical parameters for a batch distillation column: height and heat load. The principle for choosing between height and heat load is that the lower the heat load, the lower the tower height can be ； The greater the heat load, the higher the tower height can be; generally, the minimum tower height is twice the heat load. Generally, when increasing the capacity of a distillation tower, it is possible to do so by maintaining the same tower height and increasing the heat load ； Moreover, when expanding the capacity of the distillation column, it is best to increase the heat load by adding height to the column, in order to ensure operational safety and the structural integrity of the column.
I have some doubts about this. Isn’t the tower height related to the system and backflow, while the heat load is related to the tower diameter? The question is how to determine the heat load?