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Optimal Model of Integrated Water Network to Reduce the Freshwater and Energy Consumption and Produce Wastewater at Power plant

Kahe, Sadegh | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53836 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Avami, Akram
  7. Abstract:
  8. In recent years, there has been the extensive researches on energy and water efficiency due to the increasing stress on these resources. Therefore, the water-energy nexus in large industries, especially power plants, has become very important. In the present study, the water and energy nexus has been analyzed using energy analysis tools, exergy, economic and environmental in a combined cycle power plant. The nexus are observed in the boiler blow-downs, leakage of steam traps, cooling of the air entering the compressor and injection of steam into the combustion chamber, which have been studied in different scenarios to improve water and energy consumption and reduce environmental impact. In Scenario 1, implementing the cooling of the boiler and injecting it into the condenser will save 47809.5 cubic meters of make up water during one year. Using boiler blow-down waste heat will save 1.115 million cubic meters of natural gas per year. The saved costs are 3846.5 and 51116.7 million Rials per year based on domestic and international prices, respectively. As a result of the implementation of the steam trap management plan in Scenario 2, 11,900 cubic meters of make-up water and 1.64 million cubic meters of natural gas (indirectly) per year will be saved which is equal to 2672 and 46525 million Rials per year according to domestic and international prices, respectively. The payback time are 14 and 1 month, respectively. In Scenario 3, the Maisotsenko evaporative cooler is replaced instead of the fogging system which will increase the water consumption index by 9.58% and decrease fuel by 82.82%. The revenue index also increases by 13.7% in terms of domestic prices and 14% in terms of international prices. In Scenario 4; Due to the operation of the steam injection system from the heat recovery boiler to the combustion chamber of the gas unit, the output power of the combined cycle power plant is reduced by 2.1 MW (0.83%) and its exergy degradation rate is reduced by 8.5 MW (2.42%). Also, the efficiency of the first and second laws have been decreased by 0.49% and -0.4%, respectively. The concentration of nitrogen oxides may decrease from 78 ppm to 2 ppm by decreasing flame temperature by steam injected. Based on domestic prices, the economic benefits of reducing nitrogen oxide emissions from the operation of this system are not cost-effective. The economic damage in this Scenario is insignificant, while the economic benefits is 129 million Rials per hour based on international prices
  9. Keywords:
  10. Exergy ; Water and Energy Nexus ; Steam Injection ; Boiler Blowdown ; Fogging System ; Steam Traps Management ; Maisotsenko Evaporative Cooler ; Combustion Chamber

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