Novel studies on model and tuner based approach for advanced controllers in milk pasteurization process

Abstract

Milk can be defined as the lacteal secretion practically free of colostrum. However, the contamination of milk from the udder and teat surface, as well as soil bedding, manure, feed, milking equipment, milk handlers invariably lead to the introduction of psychotropic and mesophilic bacteria at reasonably high numbers. To ensure the increase in shelf life of the bovine milk, thermal treatment with three generic techniques have been evolved in dairy industries. newlinePasteurization is a nonlinear and multivariable interacting process of heating the raw milk from 6°C to 70°C, holding it for a period of 15 seconds in the holding tube and cooling it down for upto 2-4°C depending upon the setpoint in the controller. It is difficult to control this system by the conventional on off controllers since the on off controller can handle the temperature profiles for milk and water oscillating over the plant requirements. newlineThe biggest challenge for controller design in front of dairy producers and plant builders is to ensure that the process parameters are under steady state conditions followed every time and as closely as possible. Any deviation can lead to changed features or contamination, in overall to product recall and loss. This thesis presents preliminary effects of the identification of the heating exchange processes in industrial milk processing applications in respect of making improvements in control and monitoring. The control system applied in the pasteurization unit works as a closed loop system. Its goal is to stabilize the holding tank outflow temperature as close to the process set point as possible. newline