The difference between two methods of controlling steam consumption~~
Thread Content
I am studying* During the operation of the distillation tower, it was discovered that there are two different control methods for the distillation tower still temperature. One is cascade control of the tower still temperature and the steam flow rate of the reboiler, and the other is cascade control of the tower still temperature and the pressure value after the steam regulating valve of the reboiler. . . I would like to ask, what are the advantages and disadvantages of these two control schemes?
If everything is in a theoretical state, both methods are controllable. However, in the actual operation process, because the conditions of the tower are different, the feed, tower tank liquid level, and composition are all in a dynamic fluctuation. It is very difficult to control the steam flow rate, so the operability is not high. In the second case, controlling his pressure is actually not very good. The principle is the same as the first one, because during the actual operation, it is dynamically fluctuating, and the control pressure is not controlled at the point. Personally, I suggest that the best operation is to control the temperature of the tower kettle, that is to say, use the cascade control of the temperature of the tower kettle and the steam valve. Because under a certain pressure of the tower, only the appropriate temperature can evaporate the ingredients you need, and it has little to do with the steam flow rate and steam pressure you mentioned. Some DCS systems are more advanced and can be cascaded together. For example, when the temperature and control valve opening are cascaded, the shell pressure of the heat exchanger can be measured. It's better this way, the adjustment is more fine-grained.
Generally, the temperature of the tower kettle is controlled and steam is used as the heating medium. The control of steam is carried out by controlling steam flow and referring to steam pressure compensation.