Ideal binary distillation column optimization depends on the process control principles of feedback, feedforward, and hill climbing methods. For particular continuous distillation operation (olefins purification) both methods can be used simultaneously by the optimum operating parameters. Each method has its own different advantages and to find out the best of it, is an important task of the design engineer to develop a strategy for stable controlling. By choosing situation of a static model, we can easily develop a mathematical model for of distillations control system. By the help of a mathematical model, we can figure out the dependent and independent variable that are to be controlled and monitored.
Establishing a control system with two control variables is much easier than multi-variables. Two variable control systems are,
- Temperature and pressure control (feed, distillate and residue temperature and column pressure)
- Dual quality control (Steam flow rate, reflux rate)
To optimize the ideal binary distillation column four-control valves are used for controlling the level and temperature variables.
|Global valve/ needle valve||Level controller|
|1. Fitted at the bottom line of the distillation column to withdraw bottom product||1. To maintain the level at the bottom section of the distillation column|
|2. Placed at the distillate outlet line||2. To maintain the level in the reflux drum|
|Global valve||Temperature controller|
|Fixed in the steam input line to the reboiler||For controlling the flow of steam input and maintain the distillation column temperature|
|Global valve||Flow controller|
|Fixed in the reflux line||To maintain the flow rate of reflux into the column|