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Magnus Marklund, PhD student ETC

Modelling, Simulation and Optimisation of a Downflow Entrained-flow Reactor for Pressurised Black Liquor Gasification. Magnus Marklund, PhD student ETC. Gasification Plant. Gasification Reactor.  600 mm H: 1886 mm. Objective.

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Magnus Marklund, PhD student ETC

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  1. Modelling, Simulation and Optimisationof a Downflow Entrained-flow Reactorfor Pressurised Black Liquor Gasification Magnus Marklund, PhD student ETC

  2. Gasification Plant Gasification Reactor 600 mm H: 1886 mm

  3. Objective The main goal is to develop an advanced process model forthe reactor that can be used for design optimisation ofarbitrary unit sizes.

  4. Main model specifics • Based on a commercial CFD code • Simplified atomiser/burner • Submodels for drying, pyrolysis, and char gasification • Gas/droplet interactive turbulence model • Partial combustion of fuel gases • Inclusion of radiation and conjugate heat transfer • Submodel for thickness prediction of smelt layer on wall • Inorganic (smelt) reactions

  5. Methodology • CFX4 (or FLUENT 6/CFX5) • Distribution of non interacting discrete droplets • Droplet conversion by customised user routines • k-e and Reynolds stress turbulence models • Gas combustion modelled by EDC • Discrete transfer or Monte Carlo method for thermal radiation and a coupled model for conjugate heat transfer • Åbo Academy’s model for wall layer thickness • Inorganic (smelt) reactions by customised user routines

  6. Plan 01/02 • CFD4: Possible collaboration with Dr. Fletcher USYD or Åbo Academy • EXP1: Possible founding of a Particle Dynamics Analysis (PDA) device

  7. Modified coal combustion model Needed: • Proximate analysis (Moisture, volatiles, fixed carbon, and ash) • Ultimate analysis of the volatiles and fixed carbon • Higher heating value • Emissivities for droplet and char particle Devolatilization: • Moisture and volatiles are released at a rate proportional (Arrhenius) to the remaining volatiles in the droplets • Droplet swells linearly with released volatiles Char gasification: • Only combustion with oxygen • Controlled by diffusion of oxygen to the droplet surface and the char reactivity

  8. Uncertainties and difficulties Uncertainties: • Droplet size and velocity distributions from burner • Parameters for devolatilization and gasification rates • Characteristic volatile composition • Gasification of char • Boundary conditions for heat transfer Difficulties: • Resolving the burner • Convergence

  9. Simulations So far... • 2-dimensional axi-symmetric model • Burner modelled as a circular inlet • Simplified mechanistic model (no gas/ droplet interaction) • CFX4 coal combustion model • K-e turbulence model • Eddy Dissipation Model (EDM) and Eddy Dissipation Concept (EDC) …to come • 2D and 3D models • More detailed burner (separate inlets for liquor and oxygen) • Implementation of a more advanced droplet/gas interaction model • Reynolds stress turbulence model • Wall smelt layer

  10. First results (simple model) 90º Full-cone 95º Full-cone

  11. Latest results (coal model) 70° full cone spray 110° full cone spray

  12. For updated information www.etcpitea.se/blg Acknowledged sponsors:

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