1/50 MFIX Overview M. Syamlal, Fluent, Inc. Federal Energy Technology Center Morgantown, WV

2/50 Outline Multiphase Theory Validation Studies –Bubbling Fluidized Bed –Circulating Fluidized Bed –Turbulent Gas-solids Jet –Carbonizer Gasifier Application

3/50 Multiphase Theory

4/50 Multiphase Formulation Two Phases Three phases Fluid Solids Solids - 1 Solids - 2 Fluid Coal Char

5/50 Multiphase Formulation Details of flow field and particle interaction have been averaged out. Account for the information lost due to averaging - constitutive equations Constitutive equations specify how the phases interact with themselves and with each other 1 1. Drew and Lahey (1993)

6/50 Continuity Equation

7/50 Momentum Equation Interaction within the phase - stresses –collisions, sliding or rolling friction –electrostatic, van der Waals, capillary

8/50 Momentum Equation Interaction between phases - interphase forces

9/50 Momentum Equation Interactions with rest of the universe - body forces

10/50 Drag -- MFIX C d from a Richardson and Zaki correlation MFIX manual p.10

11/50 Buoyancy Model A – full description of buoyancy –1-D model has imaginary characteristics; leads to ill-posed initial value problem 1 Model B –describes only Archimedean buoyancy;e.g., doesn’t describe buoyancy in rotating flow –1-D model leads to well-posed problem 2 1. Gidaspow (1994 p. 191); 2. p.134; Also see Enwald et al. (1996)

12/50 Granular Flow Regimes Elastic RegimePlastic RegimeViscous Regime StagnantSlow flowRapid flow Stress is strainStrain rateStrain rate dependentindependentdependent ElasticitySoil mechanicsKinetic theory

13/50 Energy Balance originates from a work term for  changes

14/50 Energy Balance Viscous dissipation

15/50 Energy Balance Energy sources; e.g..., radiation

16/50 Energy Balance heat conduction

17/50 Energy Balance Interphase heat transfer

18/50 Energy Balance Energy transfer with mass transfer

19/50 Fluid-Particle Heat Transfer - The interphase heat transfer coefficient is given by where the Nusselt number is given by 1 1. Gunn (1978)

20/50 Species Mass Balance Multiphase chemical reactions are described by tracking chemical species in each of the phases

21/50 Fluid Catalytic Cracking C G PlPl AlAl C Al PhPh NhNh AhAh C Ah NlNl Ten-lump model 1 Aromatic Side chains Naphthenes paraffins Aromatic Carbon Gasoline Coke 1. Mobil/Sundaresan

22/50 Validation Studies

23/50 Fluidized Bed with Jet Gidaspow (1994) & 800  m sand (2610 kg/m 3 ) Jet velocities: 3.5, 5.77, 9.88 m/s 2D bed with a central jet 0.39 m width x 0.58 m height 124 x 108 cells 1. Sec.7.8.1; Syamlal (1997)

24/50 Bubble Size and Shape Gidaspow (1994) Fig. 7.10

25/50 Bubble Size and Shape Gidaspow (1994) Fig. 7.11

26/50 Voidage Contours time average 3.55 m/s 5.77 m/s Data - Gidaspow, Lin, and Seo (1983)

27/50 Centerline Voidage time average Data -- Gidaspow and Ettehadieh (1983)

28/50 Bubble Rise Velocity Rowe and Partridge (1962), Davidson and Harrison (1963), Syamlal and O’Brien (1989)

29/50 Jetting Fluidized Bed Yang and Keairns (1980) 0.28 cm Polyethylene (901 kg/m 3 ) Jet velocity 62 m/s, grid velocity 0.96 m/s 0.28 m dia x 2.1 m height 20x77 cells Boyle and Sams (1997)

30/50 Jet Velocity Profile Boyle and Sams (1997)

31/50 Uniform Fluidization Halow and Nicoletti (1992) 700  m plastic (1460 kg/m 3 ) Uniform flow 1.04 U mf -air 3D cylindrical bed 0.15 m diameter x 0.25 m height 30 x 100 x 16 cells

32/50 Bubble Properties Average of 9 bubbles Data -- Halow and Nicoletti (1992)

33/50 Bubble Rise Velocity Data -- Halow and Nicoletti (1992)

34/50 Circulating Fluidized Bed Bader, Findlay, and Knowlton (1988) 76  m FCC catalyst (1714 kg/m 3 ) Solids flux: 98 and 147 kg/m 2  s V g0 : m/s m dia x m height 2-D, cyl., 12 x 240 cells Gas Solids Gas + solids O’Brien and Syamlal (1993)

35/50 Pressure Drop Across CFB Data -- Bader et al. (1988)

36/50 Solids Distribution in Riser Data -- Bader et al. (1988)

37/50 Turbulent Gas-Solids Jet Tsuji et al. (1988) 2D Axisymmetric cylindrical 500  m polystyrene (1020 kg/m 3 ) - air 24 m/s gas-solids jet 20 mm nozzle in 0.3 m dia chamber 49 x 259 cells

38/50 Gas and Solids Velocities Centerline Data -- Tsuji et al. (1988)

39/50 Carbonizer Model Froehlich et al. (1994) 550  m coal and sorbent particles 1207 K, 1034 kPa axisymmetric cylindrical coordinates Flows (kg/s): coal ; sorb- 0.01; air - 0.1; N ; Steam max dia x m height 16 x 132 cells Coal, sorbent, air and steam Product gas Syamlal et al. (1996)

40/50 Carbonizer Chemistry Ash Moisture Volatile Matter Fixed Carbon CaO CaCO 3 CaMg(CO 3 ) 2 MgO CO 2 + H 2 O + CO + CH 4 + H 2 +Tar CO 2 + H 2 O + CO + CH 4 + H 2 + Fixed Carbon CO 2 + H 2 O O2O2 O2O2 coal sorbent H2OH2O CO + H 2 O W CO 2 + H 2 CO 2 O2O2 CO H2OH2OH 2 + CO H2H2 CH 4

41/50 Temperature Distribution Syamlal et al. (1996)

42/50 SynGas Composition Syamlal et al. (1996)

43/50 Gasifier Application

44/50 PyGAS J Gasifier Novel gasifier 1 ;1200 K, 4130 kPa 2120  m coal and sorbent axisymmetric cylindrical coordinates Flows (kg/s): coal+sorb- 1.8; air: pyro - 2.6, top - 0.9, grate max dia x 8.2 m height 39 x 165 cells 1. Sadowski (1992) air + Steam air+ coal air fuel gas ash

45/50 Gas Temperature Scale: Red - Blue K Upper Zone Flame (~1800 K) Stable flame at the riser bottom (~1600 K)

46/50 Coal Mass Fraction Scale: Red - Blue g/cc Coal conversion to char completes in the pyrolyzer

47/50 CO Mass Fraction Scale: Red - Blue CO and CH 4 concentrations are low in hot regions Nonuniform CO distribution in the packed bed

48/50 Tar Mass Fraction Scale: Red - Blue Coal devolatilization is completed 20 ft above the inlet Tar cracking is completed in the pyrolyzer

49/50 Other Results Information on gas and solids flow patterns Cannot maintain a tall coflow bed No regions where coal agglomerate Sticky coal particle ( o C) Char particles

50/50 It is far better to foresee even without certainty than not to foresee at all. - Henri Poincare

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