Development of a Strategy to Monitor and Control the Oil-Water Interface Level of a liquid-Liquid Separator for Treatment of Wastewater Using an Image-Based Detector

摘要

The objective of this work is to present the development of a strategy to monitor and control the organic solvent-water interface level on the MDIF~R (a mixer-settler based on phase inversion) process. This is one of the most important variables for this equipment. However, the measurement of the organic solvent-water interface level (in line) is still a hard task. There are few sensors able to measure it in laboratory scale systems due to dimensional compatibility. In the present study, a sensor for detecting the organic solvent-water interface level was developed based on the acquisition and treatment of images obtained dynamically through a camera (webcam). In addition, a control strategy was implemented in feedback mode in order to maintain the referred interface level in a desired condition. A control and data acquisition program was built in Compaq Visual Fortran language to perform the following tasks: acquisition and treatment of images for identification of water-solvent interface; decisions and implementations of control signals; and recording of data in files. Some experimental runs in open-loop were carried out using the MDIF~R and random pulse disturbances were applied on the input variable (water outlet flow). The responses of interface level permitted the process identification by transfer models. From these models, the parameters for a PID controller were tuned by direct synthesis and tests in closed-loop were performed. Preliminary results for the feedback loop demonstrated that the sensor and the control strategy developed in this work were suitable for level control.