MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...

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6. High Pressure Char Oxidation Model A new High Pressure Carbon Burnout Kinetics model (HP-CBK) was developed in this study. The HP-CBK model was based on the Carbon Burnout Kinetics model (CBK) developed by Hurt et al. (1998b). The intended purpose of the HP-CBK model is to describe char oxidation over wide ranges of experimental conditions (from atmospheric to elevated pressures, from low to high temperatures). The CBK model is described briefly in the first part of this chapter. The HP-CBK model differs from the CBK model in several aspects, which are detailed in the second part of this chapter. CBK Model The main component of the CBK model is the single-film char oxidation submodel. Some submodels (e.g., thermal annealing and ash film prohibition) and treatments (e.g., statistical treatment of properties) are available in CBK for treating near- extinction behaviors of char oxidation. These submodels were included, but were not investigated in detail in this study due to lack of detailed high pressure experimental data during late burnout. 69
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MODELING CHAR OXIDATION AS A FUNCTI
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BRIGHAM YOUNG UNIVERSITY As chair o
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CBK model uses: 1) an intrinsic Lan
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Table of Contents List of Figures..
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Appendices.........................
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Figure A.2. Mass releases of the Ko
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Table 7.6. Parameters Used in Model
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Ed activation energy of desorption,
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vc the volume of combustible materi
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Background 1. Introduction The rate
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the CBK model developed at Brown Un
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Zone III rate ∝ C og E obs → 0
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coal-general kinetic rate constants
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Boundary Layer Diffusion The molar
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= q obs q max The factor can be use
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where k 1 and K are two kinetic par
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particle can therefore be convenien
Page 38 and 39: This is the first time that the gen
Page 40 and 41: Data of Mathias Mathias (1996) perf
Page 42 and 43: urn with shrinking diameters, and t
Page 45 and 46: 3. Objectives and Approach The obje
Page 47 and 48: Introduction 4. Analytical Solution
Page 49 and 50: Task and Methodology Task One of th
Page 51 and 52: 2 [ (i +1) − (i − 1)] i b = −
Page 53 and 54: Table 4.1. The Relative Error * (%)
Page 55 and 56: The resulting observations regardin
Page 57 and 58: correction. The values of functions
Page 59 and 60: Table 4.6. The Relative Error* (%)
Page 61 and 62: Table 4.8. The Relative Error* (%)
Page 63 and 64: general asymptotic solution. An arc
Page 65 and 66: 5. Theoretical Developments The int
Page 67 and 68: order of a reaction is usually dete
Page 69 and 70: nobs = 1 (KCs ) 2 2 1 [KCs − ln(1
Page 71 and 72: The observed reaction order in Zone
Page 73 and 74: Bulk Diffusion vs. Knudsen Diffusio
Page 75 and 76: where D K is in cm 2 /sec, r p is t
Page 77 and 78: where T p is in K, P is in atm. The
Page 79 and 80: Both of these assumptions are argua
Page 81 and 82: 2 r obs ′ − [kD Pog + k d + kD
Page 83 and 84: oxygen partial pressure (Suuberg et
Page 85 and 86: Farrauto and Batholomew (1997) prop
Page 87: assumes a homogeneous, non-interact
Page 91 and 92: The fraction of the carbon content
Page 93 and 94: 6. Return to step 2 and repeat the
Page 95 and 96: The size distribution function can
Page 97 and 98: At time zero the function f E is as
Page 99 and 100: where k 1p = k 1/(RT p), K p = K/(R
Page 101 and 102: the external surface (Smith, 1981).
Page 103 and 104: arbitrariness in estimating S ext/S
Page 105: Range of Reynolds Number = (1 − P
Page 108 and 109: temperatures are so limited. Howeve
Page 110 and 111: (see Eqs. 5.4 and 5.13). From Eq. 7
Page 112 and 113: pore structure models require exten
Page 114 and 115: = 2[1 + 3 ] = 2(1 + 3 × 0.5) = 5.
Page 116 and 117: The HPCP reactor was originally bui
Page 118 and 119: Table 7.3. Conditions of the Large
Page 120 and 121: found that for each condition the r
Page 122 and 123: The second and third findings mean
Page 124 and 125: varied between 1000 and 1500 K, wit
Page 126 and 127: Table 7.5. (continued) RL P XO2 Tg(
Page 128 and 129: calculation of radiative heat trans
Page 130 and 131: Predicted Burnouts (%) 100 80 60 40
Page 132 and 133: Table 7.7. Rate Data and Experiment
Page 134 and 135: made under condition #2, it is requ
Page 136 and 137: kcal/mol for char #2 and 7.0 kcal/m
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pressure on reaction rates; and it
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120
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general asymptotic solutions predic
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Second Effectiveness Factor and ERE
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effectiveness factor for the Langmu
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2) The effectiveness factor approac
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• The CO/CO 2 product ratio is a
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Carberry, J. J., Chemical and Catal
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Hurt, R. H. and R. E. Mitchell, "On
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Reade, W., “An Improved Method fo
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138
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140
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on char properties, chars were prod
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To Air Water Bath Water Traps Flowm
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Table A.2. Measured Centerline Reac
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Bulk Density and True Density To ob
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Coal Table A.3. Proximate Analysis
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Table A.7. Elemental Analyses of Mi
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Table A.10. Densities, Surface Area
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Mass release (%) 70 60 50 40 30 20
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concentration on N 2 BET surface ar
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Rate (gC /g C remaining /sec) 2.5x1
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experiments (and reported by many r
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as high as that of char #2, both on
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4.0x10 -3 Rate (gC/cm 2 /sec) 3.0 2
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H/C mole ratio 1.00 0.75 0.50 0.25
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3) Chars produced in the presence o
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