Is automatic control used for intermittent distillation in production?
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Production conditions are changing; is it too difficult to achieve automatic control?
I have conducted relevant research; intermittent distillation takes into account the fact that the equilibrium within the tower changes throughout the process. Tower temperature is an important control parameter. If it is not a constant-pressure tower, then tower pressure also needs to be considered, as it has a significant impact on the equilibrium within the tower. In practice, simple PID control is sufficient for such purposes
From an engineering implementation perspective, it is not difficult to use automatic control; PLCs are generally employed. Selecting the appropriate control valves is more challenging, and dual valves are often used in such cases. There are also those that use a reflux ratio controller, but the effect is not very good. The key actually lies in whether the process conditions have been properly determined and whether the operation mode has been established – whether to fix the purity of the product obtained or to set the reflux ratio or tower temperature. If these aspects are taken care of, automatic control can be used; otherwise, remote control is necessary. However, from the perspective of precise control and ease in exploring and recording data, it is still better to use DCS.
Based on my experience, for the automatic control of towers like this, a PID loop is sufficient to meet the control requirements. If simultaneous control of temperature and pressure is needed, cascade PID control can be used. The key here is to have a good understanding of the process; there are many methods available for control, but the most important thing is that the process requirements and parameters must be clearly defined.