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Optimum Design of Air Jet Nozzle Preventing Hot Solid Particles Deposition on the Furnace Wall Using Numerical Simulation of Gas-Particle Two-Phase Flow

Hosseini, Faezeh Sadat | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57439 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Darbandi, Masoud
  7. Abstract:
  8. Deposition of solid particles present in the process air on the walls of furnaces is one of the challenges in industries. This phenomenon has various causes. For example, in a furnace, the temperature of particles increases as they pass in front of the furnace burners, and due to the softening of the particles, their chances of deposition increase when they collide with the walls. Over time, with the growth of deposited particle layers on the combustion chamber walls, the performance of the combustion system gradually becomes impaired. present research aims to design air jets intersecting with the process air path, with the purpose of reducing the temperature of particles prone to deposition and preventing their deposition on the combustion chamber floor. In this regard, gas-solid two-phase flow in an industrial furnace is numerically simulated. Due to the dilution of the dispersed phase, the Eulerian-Lagrangian approach is used for simulation, and the discrete phase model is employed for particle tracking. The realizable k-ε model is used for turbulence, for flame radiative heat transfer, the discrete ordinates model is used, and for species transport and combustion, the finite-rate/eddy-dissipation model is used. Particle deposition process in the combustion chamber floor is modeled using the critical viscosity model and user defined functions, along with the virtual memory defined by the researcher, implemented as code in commercial software. To demonstrate the capability of the developed method, the deposition of particles on the combustion chamber floor is first simulated without the presence of air jets, and in the particle diameter range of 40-120 microns, the effect of increasing the diameter on the deposition coefficient and the distribution of deposits is investigated. It is observed that as the particle diameter increases, the deposition coefficient initially increases and then decreases. Then, three different configurations are designed for the anti-deposition air jet with 2, 3, and 5 air jets, and these jets are placed perpendicular to the process air path and parallel to the burner. The performance of each configuration is evaluated using a baseline simulation (without jets), and the effect of jets on particle deposition rate is examined. In the following, the particle diameter and air jets velocity are varied, and through a parametric study, the effect of each parameter on particle deposition is determined. Finally, the optimal design that results in the maximum deposition reduction is introduced. It is observed that all designed configurations decrease particle deposition compared to the no-jet case; however, the designed jets perform better under conditions with higher air velocity and larger particles diameter. It is demonstrated that the optimized configuration can reduce particles deposition up to 64%. Fortunately, the mass flow rate required for these jets is less than 4% of the total air mass flow rate entering the furnace
  9. Keywords:
  10. Furnaces ; Numerical Simulation ; Critical Viscosity Model ; Jet Coefficient of Performance (COP) ; Deposition Coefficient ; Solid Particles Deposition ; Gas-Particle Two Phase Flow ; Air Jet

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