Title: Thermo-physical properties and exergy analysis of mixed-flow MEE caustic soda system

Authors: Saad Alabduljalil; Fuad Alasfour

Addresses: Department of Mechanical Engineering, Kuwait University, Khaldiya, 72303, Kuwait ' Department of Mechanical Engineering, Kuwait University, Khaldiya, 72303, Kuwait

Abstract: This research aims to perform exergetic analysis on synthetic caustic soda multi-effect evaporator (MEE) system; mixed flow type. The study investigated the effect of feed temperature variation (summer/winter) on caustic soda plant performance. Due to lack of data on thermo-physical properties of synthetic caustic soda, enthalpy (h) was evaluated and presented using three different techniques where entropy difference (s−s_o) was computed and compared against seawater published correlation. The validity range of published enthalpy correlation was tested and extended to broader temperature and concentration ranges. The deviation in entropy difference values between seawater published correlation and when using specific heat relation is found to be 4.5% at a low feed temperature of 15°C, and a more pronounced 12.6% at 90°C. Results showed that exergy destruction in the second effect decreased as the feed temperature increased while exergetic efficiency increased with an increase in feed temperature; 23.7% at 15°C and 89.7% at 90°C.

Keywords: mixed-flow MEE; synthesis; caustic soda; thermo-physical properties; NaOH synthesis entropy; NaOH synthesis exergy.

DOI: 10.1504/IJEX.2017.085767

International Journal of Exergy, 2017 Vol.23 No.3, pp.263 - 277

Received: 23 Feb 2017
Accepted: 22 Apr 2017
Published online: 12 Aug 2017 *

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