Question

Q3: The distillation column shown in the figure below is used to distill a binary mixture. Symbols x, y, z denote mole fractions of the more volatile component, while B, D, R, and F represent molar flow rates. It is desired to control distillate composition y despite disturbances in feed flow rate F. All flow rates can be measured and manipulated with the exception of F, which can only be measured. A composition analyzer provides measurements of y. (a) Propose a feedback control method and show the sketch in a figure. (b) Propose a feedforward control method and show the sketch in a figure. (c) Identify the controlled variable and the manipulated variable(s) in each control method above. D, y 0 B, x

Answer 1

According to Given question (a) The feedback controller consists of the At (analyzer or Transmitter) and AC (composition or the analysis controller). The molar flow rate B, x is indicated in the figure The feedback controller responds only if there is any deviation present in the controlled variable from the set point Here, y = control variable R - manipulated variable. AT - Analyzer/Transmitter AC - composition (analysis) controller (b) The feed forward control method responds if there is any disturbance is detected in the process involved. The molar flow path B, x is indicated in the figure. Here in figure y = control variable R = manipulated variable Measured variable = Disturbance in the feed (F) (P.T.O)