Enhancement of energy efficiency at an Indian milk processing plant using exergy analysis

The dairy sector in India is the largest milk producer in the world. Substantial amounts of freshwater and energy are consumed during milk processing with concomitant impacts on sustainability. In this chapter, we study the energy efficiency at India’s largest milk processing plant and propose retrofits for improving the plant’s sustainability. Specifically, we report on exergy analysis of a milk powder manufacturing unit. Exergy of a system at a certain thermodynamic state is the maximum amount of work that can be obtained when the system moves from that state to one of equilibrium with its surroundings. In contrast to a conventional energy analysis, which maps the energy flows of the system and suggests opportunities for process integration, an exergy analysis pinpoints the locations, causes, and magnitudes of thermodynamic losses. The milk powder plant that is the focus of the current study consists of two sections—an evaporation section and a drying section. Our results reveal that exergy efficiency of certain units is very low (<20%). Significant improvements in energy efficiencies can be achieved through simple, low-cost retrofits to these units.