Application of advanced thermodynamics, thermoeconomics and exergy costing to a Multiple Effect Distillation plant: In-depth analysis of cost formation process

• A forward feed Multiple Effect Distillation plant is examined.
• An exergy analysis is performed at single effect and at subprocess levels.
• A thermoeconomic model is developed, that includes “residue” exergy flows.
• Specific costs are calculated for each chemical and thermal exergy flow.
• Asymmetries are found in the unit cost of distillate produced in different effects.

The high thermal energy consumption per m3 fresh water is one of the main barriers to the spread of thermally driven desalination processes and has limited their use to applications in countries with high reserves of fossil fuels or to specific technological solutions like dual purpose cogeneration plants and solar desalination systems. Being energy conversion efficiency a major issue to improve the performance of thermally driven desalination plants, thermoeconomic analysis has been attracting the efforts of researchers for the identification of margins for process improvement. In this paper a rigorous exergy and thermoeconomic analysis is presented for an 8 effect forward feed Multiple Effect Distillation plant, based on models developed in Engineering Equation Solver. The innovative contribution lies in the detailed methodological formulation with explicative notes on the main assumptions and in the high level of disaggregation used, which allows us to follow each specific subprocess and thus to acquire an in-depth understanding of the whole cost formation process. The results indicate that the monetary value associated with the physical and chemical exergy flows highly vary throughout the plant and that the contribution to the final cost of fresh water is higher for the distillate produced in the last effects.