The main equipment of cracked gas compressor unit includes five stage compressors whose numbers are K-13001, K-13002, K-13003, K-13004, and K-13005; alkali washing tower whose number is C-1340; and high pressure depropanizer
tower whose number is C-1365.
To test the methodology proposed in previous section, a depropanizer
process (Lee, 1993) is used as a case study where the mole fractions of propane in distillate and isobutane in bottom product are controlled by simultaneously adjusting the reflux ratio (RR) and boil-up rate (Q) in the face of sinusoidal disturbances in feed composition.
The effect of neglecting the vapour phase in the simulation of a depropanizer
operating at a pressure of 15 bar is illustrated in Figure 7 where the propane composition in the bottoms is plotted as function of the time after an increase in the reflux ratio.