Experimental evaluation of the continuous pasteurization control of a orange juice model fluid / Avaliação experimental do controle da pasteurização continua de um fluido modelo de suco de laranja

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The goal of this work was the building, instrumentation and implementation of conventional and non-conventional controllers in a HTST (Hight Temperature Short Time) continuous processing prototype of fruit juice. A plate heat exchange with three sections of heat exchange (regeneration, heating and cooling) and a holding tube were used to achieve a holding time of 40 s at 91oC, used in the processing of orange juice. Water at high temperature and propylene-glycol solution were used to heat and cool the product, respectively. The model-solution used was composed of water and sucrose, with the same rheological and thermo-physical properties of the refereed juice. The three fluid lines were instrumented and controlled according to the strategies and logics used. The dynamic behavior of the pasteurization and cooling temperatures after disturbances in the secondary fluid flow rates were best represented by second-order systems with the dumping ratio equals to one. The dynamic behavior of the same temperatures after disturbances in the inlet product temperature were best represented by first-order systems with dead time. Both behaviors presented low level of non-linearity. The control strategies and logics implemented were the conventional controllers PID/feedback and PID/feedback/feedforward and the non-conventional controller Fuzzy/PID/Feedback. The controlled variables were the pasteurization temperature after holding tube, and the cooling temperature at the outlet of the pasteurizer; while the manipulated variables were the flow rates of the secondary fluids. The controls were evaluated and compared by the absolute error indexes, IAE, ITAE e ISE and by the behaviors of the manipulated variables, after disturbances in the product inlet temperature. The results showed that the error of both controlled temperatures were within ±0,4 oC range after disturbances in the inlet modelsolution temperature. The error indexes of the three controllers tested presented similar values, indicating efficiency of the controllers in the maintenance of the pasteurization and cooling temperatures.

ASSUNTO(S)

suco de laranja logica difusa suco de laranja - pasteurização nebulous logic controladores pid pasteurization orange juice dip controllers

ACESSO AO ARTIGO

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