Techno-Economical Simulation and Study of a Novel MSF Desalination Process

  • Mohamed Ibrahim Al-Hamahmy

Student thesis: Master's Thesis

Abstract

A techno-economical model of conventional MSF configurations (both Once-Through and Brine Recirculation) was developed. The model is validated against the design data of a 1 MIGD desalination plant Ayoun Mousa (Suez- Egypt). A model of a 16.2 MIGD MSF plant is also generated and used for model verification. After verification, the model is used to investigate areas of cost reduction in Ayoun Mousa, which involve using Al-Br for low-temperature flashing stages and increasing the diameter of condenser tubes. The model was then used to study a novel MSF configuration tentatively known as “Brine extraction”, where part of the brine flowing in the water boxes is extracted before reaching the brine heater and injected directly into the low cost flashing stages at lower temperature. Two extraction methods were studied: Single-point extraction and multiple-point extraction configurations. Finally, single point brine extraction at high TBT was studied for the 16.2 MIGD plant. The results show that: 1. For Ayoun Mousa, the common practice of using Cu-Ni 90/10 for high temperature flashing stages (> 70°C) and Al-Br for low temperature flashing stages causes a considerable reduction in CAPEX but increases specific electrical consumption due to the reduced flow area and increased brine velocity. CAPEX was reduced by 16.1% and specific electrical consumption was increased by 4.21% while tube diameter was kept the same. However, an increase in diameter of the recovery section condenser tubes offsets the increase in specific electrical consumption A 10% increase in tube outer diameter (with constant thickness) caused nearly a 21% reduction in specific electrical consumption, and a 10.9% decrease in specific cost of water compared to conventional Ayoun Mousa, with the GOR remaining unchanged. 2. Single-point brine extraction performed better than multiple-point brine extraction. For Ayoun Mousa, single-point extraction from the eighth stage caused up to an 8% increase in GOR, a 10.85% decrease in electrical consumption, and a 1.826% decrease in specific water cost. For the 16.2 MIGD plant, single-point extraction from the fourth stage caused up to a 7.23% increase in GOR, a 3.47% decrease in electrical consumption, and a 3.90% decrease in specific cost of water. 3. For the 16.2 MIGD plant at 9% extraction ratio, brine extraction at high TBT showed improved results for certain parameters. At 130°C TBT, extraction caused a 5.8% increase in GOR and an 8.5% decrease in electrical consumption. Economically speaking, introduction of brine extraction at this higher TBT caused a 5% increase in CAPEX and a 5.4% decrease in OPEX, leaving the total specific cost of water nearly unchanged. Therefore, the implementation of brine extraction at higher TBT may be fruitful in the case of solar-power MSF considering the high expense of supplying thermal and electrical energy through solar means.
Date of Award2011
Original languageAmerican English
SupervisorHassan Fath (Supervisor)

Keywords

  • Saline Water Conversion
  • Saline Water Conversion-Economic Aspects

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