An ultrasonic technique is employed for the control of the dispersed-phase volume fraction (holdup) in liquid-liquid column extractors. The technique is tested for a multistage extractor of pilot-plant scale where the holdup is continuously monitored in all stages. The average holdup in the column, calculated from the profile, is considered as the control variable, while the agitation speed is used as the manipulated variable. The volumetric flow rates are the other operating conditions and are considered as disturbance variables. Adaptive and nonadaptive control are demonstrated by applying the Dahlin algorithm. By inspection of the holdup profile, information about the operation of the column with respect to flooding or phase inversion is provided. This information is processed for driving the holdup set point in the proximity of flooding where optimum operation usually occurs. For the first time, holdup is controlled over a wide range of values from as low as 10% to as high as 90% of the holdup value at flooding. The importance of the ultrasonic technique for the control of extraction columns is that it can be readily applied for safe operation at optimum conditions for any type of existing or new extractors.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering