Comprehensive exergy analysis of an industrial-scale yogurt production plant

In this study, a comprehensive and detailed exergy analysis was carried out to investigate an industrial-scale pasteurized yogurt production plant located in the north-west of Iran, West Azarbaijan province. For this goal, the plant was subdivided into four main subsystems, including steam generation, above-zero refrigeration, milk standardization and pasteurization, and yogurt production lines. Accordingly, exergetic efficiency and exergy destruction rate were defined and computed for each component of the four lines individually. Moreover, this analysis was conducted to find the amount of exergy consumed in producing a given amount of the pasteurized yogurt. The main contributors to the exergy destruction of the entire plant were in descending order of importance: boiler & air compressor combination of the steam generator (12484.88 kW), ice-water tank & agitator combination of the above-zero refrigeration system (2900.59 kW), and pressure reducer #2 of the steam generator (731.82 kW). Moreover, the specific exergy consumption of the pasteurized yogurt was found to be 841.34 kJ/kg based on the mass allocation concept. More specifically, the percentile contributions of the steam generation, above-zero refrigeration, milk standardization and pasteurization, and yogurt production lines to the specific exergy consumption were determined as 82.62%, 9.36%, 2.80%, and 5.21%, respectively.