Sensor locations and noise reduction in high-purity batch distillation control loops

The influence of the sensor locations on the composition control of high-pu rity batch distillation columns has been investigated. Using concepts of th e nonlinear control theory, an input-output linearizing controller was impl emented to keep the distillate composition constant at a desired value by v arying the reflux ratio. An Extended Kalman Filter was developed to estimat e the compositions required in the control algorithm using temperature meas urements. In the presence of measurement noise, the control performance dep ended greatly on the sensor locations. Placing the sensors further from the top stages reduced the detrimental effects of noise but increased the infe rence error. To achieve accurate composition control, both noise reduction and composition estimate accuracy should be considered in the selection of the sensor locations.