Implementation of advanced real-time process control on a continuous flow ohmic heater

Ohmic Heating (OH), and its application to food processing, is a very energy-efficient form of heating compared to conventional methods such as conduction and convection. OH is a Moderate Electric Field (MEF) processing technique in which the applied electric field is ≤ 1kV/cm, considerably lower than the field strength used in the high voltage Pulsed Electric Fields (PEF) technology. Key advantages of OH include rapid heating, reduced food processing times, bacterial inactivation, electroporation, and elimination of unwanted temperature peaks. This paper describes the work to design and implement advanced real-time control on a continuous flow ohmic heater pilot plant. The application of classical to advanced model-based process control including Proportional, Integral and Derivative (PID) control, Model Predictive Control (MPC) and adaptive model predictive control on the continuous flow ohmic heater pilot plant gives a template that can be replicated in the industry for efficient energy consumption. The implementation of these controllers is achieved using Open Platform Communications (OPC). With OPC, a server and client protocol are used to exchange data in real-time between the Programmable Logic Controller (PLC) and a stand-alone lab-based computer so that classical PID control and advanced model-based control (e.g., Model Predictive Control) designed in MATLAB/Simulink can be applied on the continuous flow Ohmic Heater. This research demonstrates the following: • model-based design and validation of OH processes with applications in the food industry; • advantages of OH comparing to conventional methods; • benefits of advanced process control comparing to classical controller in food engineering; • technique of implementing real-time advanced process control on a PLC based hardware. This work presents the quantitative results which demonstrate significant improvements in modelling and controlling the OH process with regard to food materials of varying conductivities, flow rates and initial temperatures.