Numerical Simulation of an Entrained Flow Gasifier by an Eulerian Model
In the present work, the Eulerian–Eulerian method is used to simulate a laboratory-scale coaxial entrained flow gasifier in Brigham Young University. The gas turbulence in the reactor is modeled by the k-ε turbulent model, and the particle phase is modele
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Abstract
In the present work, the Eulerian–Eulerian method is used to simulate a laboratory-scale coaxial entrained flow gasifier in Brigham Young University. The gas turbulence in the reactor is modeled by the k-ε turbulent model, and the particle phase is modeled with the kinetic theory of granular flow (KTGF). In the simulation of turbulent chemical reaction flow, three heterogeneous reactions and five homogeneous reactions are considered. For thermal energy equilibrium, the P-1 radiation model is coupled with the transport equation of energy. Different from conventional Eulerian model, in this work the gradient-diffusion model is introduced to modify the particle distribution because of turbulent diffusion. Furthermore, it is considered the diameter of solid fuels is changing during the gasification. Therefore, a new variable and its transport equation are implemented to capture the coal particle diameter change in this simulation. All submodels above are integrated and realized in the open-source software MFIX. The simulation results have a good agreement with the experimental measurements, and the carbon conversion in the simulation is 82.8 %. Keywords
Coal gasification
Numerical simulation
With the strict demand of environment protection, more and more attention has been paid to the coal clean technology (CCT). Coal gasification is an important technology of CCT instead of burning coal directly. Many works have been done to study the gasification theory and improve the gasification process. According to research conducted by experiments and numerical simulations, the entrained flow gasifier is the main reactor for coal gasification [1–3]. The syngas composition and temperature distribution can be received based on CFD simulation due to the more affordable and enhanced computation hardwares. Therefore, the CFD simulation is used as a tool for design and optimization of reactor in industries. Chen et al. [4] used the multi-solids process variable method to simulation a pilot-scale gasifier and analyzed the effect of the different operating parameters on gasification results. Watanabe et al. H.P. Xu H.B. Zhao (&) C.G. Zheng State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan, 430074, China e-mail: [email protected]
Gradient-diffusion model
Diameter change
[5] developed the extended model to design and optimize coal gasifiers. Snider et al. [6] conducted the three-dimensional simulation using the computational particle fluid dynamic method and studied the energy transport between phases. However, the particle mass is changing in the real operation. Many modified submodels are introduced to capture the mass loss in the simulation work. Vascellari et al. [7] investigated the particle diameter changing submodel modeling coal pyrolysis and char conversion, and the results of four different rank coals validated the method. The gas and particles were described by two separate PDF transport equations in the Stoellinger el al. work [8], and the particle diameter change
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