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Designing of Integrated Polygeneration System of Heating, Power and Carbon Dioxide in Urban Wastewater Treatment Plants

Movahhed, Paria | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51834 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Avami, Akram
  7. Abstract:
  8. With the growing development of urban communities and population, the demand for water and treated sewage water has grown significantly. The environmental damage of polluted water has resulted in passing of new and strict environmental laws on wastewater discharge recently. In the present research, a hybrid system involving a power, heat and cool cogeneration and a carbon dioxide capture system has been designed for a typical wastewater treatment plant. The plant is optimized from economic and environmental criteria. The anaerobic digester is modeled using the ADM1 model. The biogas is directed into the hydrogen sulfide removal filter to remove the impurities and into the heat exchanger to remove the moisture. The biogas is entered into the microturbine as fuel and the product gases supply the required heat and then the product gases of combustion are used to grow alga and produce biodiesel. Genetic algorithm has been used to optimize the hybrid system. The objective functions include system’s total cost rate, the amount of the produced biogas, annual profit, the amount of the produced carbon dioxide and the levelized cost of electrical energy which are studied in a 4 different scenarios. The optimization variables include digester hydraulic retention time, compressor pressure ratio, compressor isentropic efficiency, recuperator pinch time temperature, turbine isentropic efficiency, turbine input temperature, number of microturbines and the fraction of the product gases combustion to grow alga. The objective functions for each scenario is first optimized using the genetic algorithm’s single-objective optimization, and then, optimized using multi-objective optimization. Non- dimensionalised Euclidean and linmap methods are used to find the final optimal point. In the first scenario, the optimal value of the system’s total cost rate and the amount of the produced biogas of 0.027406 dollars per second and 12623.5 cubic meters have been obtained, respectively. In the second scenario, the maximum annual profit and the minimum produced carbon dioxide of 1070458 and 47.73474 tons per year have been obtained, respectively. Finally, the effect of some important parameters have been assessed on different objectives like the system’s total cost rate’s objective functions, levelized cost of electrical energy and annual profit using Sobol sensitivity analysis. Retention time, power purchase price, and profit rate have the highest impact on the system’s total cost rate by 15% each. Retention time has the highest impact on the levelized cost of electrical power by 15%. Also, power purchase price, chemical oxygen demand, retention time and carbon tax have the highest impact on the annual profit by 14% each
  9. Keywords:
  10. Wastewater Treatment Plant ; Biogas ; Optimization ; Anaerobic Digestion ; Microturbine ; Algae Cultivation ; Sensitivity Analysis

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