MODELING CHAR OXIDATION AS A FUNCTION OF PRESSURE ...

Bulk Density and True Density
To obtain the bulk density of a coal or char, the coal or char sample was weighed
using a microbalance and put into a graduated cylinder, which was then tapped until the
volume of the sample did not change. The bulk density (also called tap density) is the
weight of the sample divided by the volume displaced by the sample, where the volume
includes micro- and macro-pores and inter-particle voids. Apparent densities were
calculated from the bulk density, ρ b, by:
app =
b
1− bv
where bv is the fraction of inter-particle void volume in the char bed, usually taken as
0.45 (White et al., 1995). True densities were measured in a Quanta Chrome helium
micro-pycnometer (model MPY-2).
High Temperature Reactivity
The temperature profiles at the centerline of the FFB tower were measured for
conditions #2 and #4 at extended sampling heights. These two measured temperature
profiles were very similar at each sampling height. The difference between the two
148
(A.1)
temperature profiles at any reaction height was usually about 7 K, and never greater than
50 K. Some of the differences observed in the measured temperature profiles were due to
(a) the uncertainty of the thermocouple bead position (vertical and horizontal), and (b)
the non-steady heat-up effects of the tower.
Koonfontain chars were collected at heights of 1”, 2”, 4”, and 6” under these two
conditions. The daf mass release data for these chars were determined by ICP tracer