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Dynamic Modeling of Top-Fired Steam Methane Reforming Furnaces

Moein Kia, Zahra | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56790 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Farhadi, Fathollah; Vafa, Ehsan
  7. Abstract:
  8. CFD models are accurate but time-consuming for simulation and optimization of steam methane reformer and controlling the tube wall temperature, and syngas production rate and unsuitable for online optimization. Empirical data-driven models are less accurate when there are wide variations in operating conditions. The physics-based model presented in this thesis overcomes these limitations. In this model, the furnace side and the process side are divided into zones with uniform temperature and composition, and for each zone, mass, energy and momentum balances are derived. Radiative heat transfer modeling and calculation of exchange areas are accomplished with the zone method. The system of nonlinear algebraic equations obtained in the steady state and the system of nonlinear differential-algebraic equations in the unsteady state are solved by numerical methods. The temperature profiles of the furnace gas, the inner and outer walls of the tube and the process gas, as well as the molar composition profiles and pressure profiles of the process gas are obtained. With the help of this model, the furnace is balanced. Balancing is the proper distribution of fuel between the burners in order to make the temperature distribution uniform in the cross section of the furnace. By reducing the non-uniform distribution of the tube wall temperature in the cross-section of the furnace, the maximum operational temperature of the furnace increases by observing the admissible temperature limit of the tubes, and the efficiency of the process and the rate of hydrogen production increase. Also, the transition behavior of the reformer is predicted in vis-a-vis the disturbances. The time constants and duration required to reach steady conditions after furnace balancing are calculated and reformer optimization and control structure design are obtained. The results of the static model, are similar to those of the literature and the results of the dynamic model, are appropriate for the studied scenarios. This model can be converted into more specialized versions. In this research, a benchmark dynamic model was presented to conduct control studies. A platform for calculating exchange areas between different zones of furnaces with conventional geometries was created and successfully realized
  9. Keywords:
  10. Steam Methane Reforming ; Static Models ; Dynamic Model ; Radiative Heat Transfer ; Zone Method ; Furnace Balancing ; Computational Fluid Dynamics (CFD)

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