MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...

Effectiveness Factor, η
2
1
8
6
4
2
0.1
8
6
4
6 8
0.1
Zeroth order, two asymptotic lines
first order
2 4 6 8
1
General Thiele Modulus, MT 19
2 4 6 8
10
Figure 2.2. The effectiveness factor curves for first order and zero-th order reactions
in Cartesian Coordinates. For reactions between zero-th order and first
order limits (0 < m < 1 or 0 < KC s < ∞), the curves lie in the narrow band
bounded by the first order and the zeroth order curves.
High Pressure Data in the Literature
A review of published data from high pressure coal combustion and char oxidation
experiments is listed in Table 2.1. The experiments by Monson (1992) have been
mentioned earlier. The rest of these experiments are discussed briefly below.
Table 2.1. Test Conditions for Various High Pressure Oxidation Rate
Measurements
Investigator(s) Fuel diameter
(μm)
Tp (K) Ptotal(atm) xO2 (%)
Monson (1992) chars 63-75 1300-2100 1-15 5~21
Mathias (1996) coals and
chars
Mostly 8000 900-1300 0.86-5 6-18
Ranish and Walker (1993) graphite flakes 733-842 1-64 100
Banin et al. (1997) chars ~6 1200-1800 8 0-100
Croiset et al. (1996) chars 90-106 850-1200 2-10 1.5-10
MacNeil and Basu (1998) chars 417-2000 973-1123 1-7 10-21
2