MeOH Column Control app for iPhone and iPad

A 40-tray binary distillation column (methanol/water) is simulated dynamically in this App. The column is equipped with a hierarchy of conventional PID controllers from basic level- and flow-controls, through tray temperature, ratio- and feedforward controls, and up to product composition controllers. The hierarchy is configured in a cascade arrangement. The user can select local Automatic or Manual on all controllers and Cascade mode on those controllers that have their set-points provided by a Master controller. All controllers can be tuned by the user and in many cases it is possible to find good settings from using the built-in ATV tuning technique.
The feed rate and composition to the column can be changed to study the columns open-loop responses to these disturbances and the closed-loop control systems ability to reject them. The feed rate and composition can also be configured to inject periodic disturbances of varied frequency and magnitude. As the feed composition is changed, the feed- and temperature trays can also be altered to optimize the columns steady-state and dynamic behaviors.
Each controller has two associated strip-charts; one for PV and one for the controller output. In addition, other strip-charts and Profile Charts are selectable by the user. The Profile Charts show temperature and composition profiles across the column. A profile can be "frozen" or "un-frozen" at any time by "double-tapping" the chart. This is particularly useful for finding a responsive tray temperature location.