Reboilers—Open-Loop Dynamics

as R becomes very large, the preceding equation becomes simpler  

We wish to make an analysis of column bases with associated reboilers where there is significant liquid holdup. The analysis should take into account the temperature of the entering liquid and the sensible heat effect of the liquid mass. Such an analysis also applies to vaporizers with associated separators or knockout drums. 

First signal flow diagram for Wc of flooded condenser 

Reduced signal flow diagram for of flooded condenser 

By using perturbation techniques and Laplace transfcMming this equation we get  

---

Reboilers—Open-Loop Dynamics If steam flow is noncritical,... 

Subsequently, we used Aspen Dynamics for time-domain simulations. A basic control system was implemented with the sole purpose of stabilizing the (open-loop unstable) column dynamics. Specifically, the liquid levels in the reboiler and condenser are controlled using, respectively, the bottoms product flow rate and the distillate flow rate and two proportional controllers, while the total pressure in the column is controlled with the condenser heat duty and a PI controller (Figure 7.4). A controller for product purity was not implemented. 

---