Graduate research project (EPFL, Fall 2023) analyzing and optimizing the energy and environmental performance of a dairy processing facility.
The work combined thermodynamic modeling, exergy analysis, heat recovery design, pinch analysis, and utility integration to identify cost-saving and decarbonization opportunities.
How can an industrial dairy factory reduce energy costs and exergy losses while integrating circular-economy co-products (e.g., Rivella from whey, biogas from sludge)?
- Computed heat and mass balances for all major sections: pasteurization, evaporation, drum dryers, Cleaning-in-Place, cold storage, hot water generation, and wastewater/sludge handling.
- Established flow properties as a basis for exergy and energy analyses.
- Exergy losses were quantified across subsystems, with pasteurization and evaporation identified as major inefficiencies.
- An energy bill was calculated for both France and Germany, yielding OPEX of 1.43 M€/yr and 1.68 M€/yr, respectively.
- Optimized minimum temperature differences in heat exchangers to improve efficiency.
- Evaluated additional heat recovery in pasteurization and Cleaning-in-Place processes.
- Found modest OPEX reductions, with country-specific differences in feasibility.
- Constructed hot/cold composite curves and the grand composite curve.
- Determined minimum energy requirement (15,873 kW), maximum recovery potential (27,013 kW), and pinch temperature (67 °C).
- Designed HEN using path and loop methods:
- Path → reduced CAPEX, increased OPEX
- Loop → increased CAPEX, reduced OPEX
- Modeled alternative technology mixes with Rosmose: cooling tower, boiler, cogeneration engine, heat pump, and refrigeration.
- Integrated utilities with the grand composite curve to minimize exergy losses.
- Identified optimal configuration: cogeneration engine + HP + refrigeration + cooling tower, with no boiler required.
- Rivella production: converting whey into a beverage co-product → halved utilities installation costs via increased revenue.
- Biogas production: digestion of whey and sludge → low financial returns, limited impact on costs.
- Combined Rivella + Digester scenario showed Rivella as the dominant value-adding option.
- Large exergy losses in pasteurization and evaporation highlight need for efficiency improvements.
- Heat recovery and HEN design yielded moderate OPEX reductions but were sensitive to process configurations.
- Utility integration showed boilers unnecessary; cogeneration and HPs are more effective.
- Rivella co-production strongly reduced TOTEX via new revenue streams, while biogas had negligible effect.
- Final recommendation: Collaborate with Rivella and implement optimized energy conversion technologies.