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Numerical Simulation of Reacting Flow in Large Scale Heavy Fuel Oil Fired Furnaces to Control Temperature Field and NOx Emission

Fatin, Ali | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50943 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Darbandi, Masoud
  7. Abstract:
  8. Heavy fuel oil (HFO) is usually consumed in large scale furnaces, e.g., those of power plants. Experience shows that its combustion produces large amount of NOx emission. In present study, a large scale heavy fuel oil fired furnace is numerically simulated to investigate different possible solutions for NOx reduction. In this regard, a computational framework is firstly designed benefiting from the researches reported previously in literature. The results of this framework are then compared with available measurements to evaluate the accuracy of current designed computational framework. Second, the influences of a number of different controlling parameters are studied carefully to improve the reacting flow characteristics and reduce the pollution emission through a large furnace. The investigated parameters include the swirl of the burner secondary flow, the air distribution between burner’s stages, the size of fuel droplets, and the fuel injection velocity. The effect of these parameters is specially investigated to evaluate the NO emission at the stack exit. The results show that both NO emission and combustion efficiency first decrease and then increase by increasing the swirl effectiveness. On the other hand, it is shown that by increasing the air flow rate through the first stage of burner, there is reduction in NO emission. However, the combustion efficiency shows different scenarios. Indeed, no general comment can be derived for the combustion efficiency. The study of fuel droplet shows that both NO emission and combustion efficiency reduce accordingly by increasing the fuel droplet size. Similarly, the current results show that an increase in fuel injection velocity will reduce both the NO emission and combustion efficiency. Following the performed investigations, we prepare three different adjustments for the proposed burners. Then, the best adjustment is selected among these based on not only the maximum NO reduction but also the minimum combustion efficiency drop. Eventually, the current study shows that the NO emission can be reduced by 225 ppmv (39% reductions) in the best scenario. However, the combustion efficiency drops negligibly under this circumstances
  9. Keywords:
  10. Numerical Simulation ; Combustion ; Heavy Fuel Oil ; Reduction of Nitrogen Oxides ; Large Scale Furnace

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