Identification of high temperature short time milk pasteurization unit

Abstract

AbstractThis research pertains to the development of a dynamic‐model and identification of parameters for high‐temperature‐short‐time (HTST) pasteurization process using plate‐heat‐exchangers for precise controller scheme for this process. Real‐time HTST process consists of three integrated sections, (a) plate‐heat‐exchanger engaged in regeneration, heating and cooling (b) holding tank, and (c) holding tube. The models for these sections are identified using Matlab. The dynamics of the HTST process using the first‐principle method consisting of two inputs one‐output model is derived. The parameters of the dynamic model are identified using the autoregressive‐exogenous linear identification technique, ARMAX, and subspace system identification to predict the outlet temperature of HTST process. Finally, a dynamic‐model, relating exit temperature to input enthalpy is obtained from the closed‐loop process input–output data, using a nonlinear least‐square‐estimation technique. The quality of prediction of linear‐model structures is checked using plant's data. The results obtained from the linear‐models are in good agreement with plant‐data.Practical applicationMilk should be free from toxins and pathogens and also it must retain all nutrients and vitamins with extended period of storage life. To achieve the above said criteria, milk is heated to a particular temperature for a brief time then cooling it down once more quickly. Moreover, to avoid superheating, the temperature needs to be controlled. As model‐based‐control perform satisfactorily, tuning of controllers can be done using model parameters of this milk‐heating process. These model parameters are obtained from on‐line identification of the predicted model using real time plant input–output data. This paper deals with identification of model parameters for the milk pasteurization process. The formulated model equations are also validated, which will help in optimizing the operating parameters and scale‐up design.