Article ID Journal Published Year Pages File Type
625684 Desalination 2010 9 Pages PDF
Abstract

This paper represents the 2nd part of a paper in two parts. In part I a 2nd Principle analysis of a Multiple-Effects-Evaporation (MEE) process has been proposed. In this Part II perspectives for process improvement will be investigated, along two distinct research lines: the thermoeconomics-aided optimization of a new system and the increase of thermal efficiency for existing systems by a pinch-based plant retrofit. As concerns the first research line, a detailed productive structure for the plant stage (i.e. effect) examined in Part I is presented; the cost formation structure is then used to improve a simplified optimization process, revealing capable to properly reflect the interactions among exergy flows. It is shown that the flash at brine inlet and the exergy destruction at the pre-heaters, both apparently playing a secondary role with respect to heat transfer at the evaporators, become main sources of irreversibility when the ΔT between two consecutive effects increases. Then, as a corollary to the low exergetic efficiency calculated in Part I of this paper, the potential for exergy saving through process integration is discussed. Although detailed calculations are not included, a conceptual application of pinch-based techniques is proposed, which reveals scarce margins for integration at process level and a much higher potential for process/hot-utility integration. The use of heat cascades can be optimized looking at the Thermal Desalination Process as a black box; economics of cogeneration systems integrated with the desalination plant and targeted on heat supply, in fact, essentially depends on the cost of feed steam, fuel and electricity.

Related Topics
Physical Sciences and Engineering Chemical Engineering Filtration and Separation
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