Gas turbine total energy vapour compression desalination system

Abstract

Various arrangements for heat recovery systems (HRS) are investigated for using the waste energy of a gas turbine (GT) engine driven sea water desalination plant, and the outcomes are compared with a basic sea water reverse osmosis (SWRO) plant. These arrangements are analyzed, and their flow diagrams are presented. The analysis showed that using a mechanical vapour compression (MVC) unit driven by the engine and utilizing its exhaust to fire two LiBr-H 2O absorption cycle subsystems, in an all evaporation distillation system, yields a significantly improved plant performance compared to the basic one. The first absorption cycle operates in parallel with the MVC unit to fire a multiple effect stack (MES-I) with an evaporation range (ER) of 117–69°C across 17 effects. The second cycle, however, works across a 19 effects low temperature MES-II with an ER of 66–6°C with its bottom effect being connected to a common absorber for the two cycles. Compared with the SWRO system alone, using a 5.72 MW GT engine, the proposed arrangement increases the production by 72.4 percent from 2.9 to 5 mgd of potable water in addition to the 138.2 m 3/d of heating steam condensate. This increases the performance ratio (PR) from 15.2 to 26.2 and, thus, reduces the power requirements from 12.5 to 7.27 kWh/m 3 of potable water. This is equivalent to an increase of 21.2 points for the GT thermal efficiency. Moreover, the system contributes a 1000 TR (ton refrigeration) cooling to the A/C units, as a by-product, which saves 1029 kW of equivalent power. Thus, the overall thermal efficiency is boosted by 26.5 points, which is equivalent to an annual savings of 11094 tons of Diesel fuel.