Control method for the heating load of a distillation tower

The pressure and temperature at the bottom of the tower, the pressure at the top of the tower, and the total pressure drop across the tower can all be used as references

This post was last edited by *amingteda on 2017-2-21 09:24. What’s the difficulty in that? It’s explained in any chemistry book that covers control structures; for ordinary distillation towers, two approaches are generally used: 1. The reflux rate is kept constant, and the heating capacity of the reboiler is adjusted to control the temperature of a certain sensitive tray within the tower. For example: if the temperature of the sensitive plate is too high, the heating capacity of the reboiler is reduced ； The temperature of the sensitive plate is low, so the heating amount is increased. The goal of controlling the product composition is achieved by ensuring that the temperature of the sensitive plate remains within a certain range. 2. Keep the reboiler heating capacity constant, and adjust the reflux flow rate (or reflux ratio; in special cases, the top product yield) to control the temperature of a specific sensitive tray. The analysis is the same as above!

The actual systems and operating conditions for distillation separation vary, requiring appropriate control strategies; moreover, many columns used for removing small amounts of impurities do not have a sensitive plate temperature. For example, in the case of some product recovery distillation columns, the control strategy commonly used is to increase the heating load of the reboiler when the liquid level at the bottom of the column is high, in order to evaporate the product components from the top of the column as much as possible and prevent these components from being discharged from the bottom of the column as heavier components ； Only when the accumulated heavy components at the bottom of the tower raise the bottom temperature to a certain level should the flow rate of these heavy components being removed from the bottom of the tower be increased appropriately, or intermittent removal of such components be carried out.